Dear Readers,
Important notice
This guide is intended to provide general information regarding All Weather Operations.
In no case it is intended to replace the operational and flight manuals for ATR aircraft.
In all events, the information contained in the Aircraft Flight Manual shall prevail over the content of this guide.
Every effort has been made to ensure document quality. However please
do not hesitate to share your comments and information with us by using
the following address: flight-ops-support@atr.fr
We would also like to thank ENAC (Ecole Nationale de l’Aviation Civile) for
its involvement in the development of this guide.
Yours faithfully,
Printed on 100% recycled paper using vegetable inks
Your ATR Training and Flight Operations support team.
© ATC June 2010
All reasonable care has been taken by ATC to ensure the accuracy of the present document.
However this document does not constitute any contractual commitment from the part of ATC which will offer, on request,
any further information on the content of this brochure. Information in this brochure is the property of ATC and will be treated
as confidential. No use or reproduction or release to a third part may be made there of other than as expressely authorised by ATC.
7B$75B$:2BFRYHULQGGFRXY
Dear Readers,
The ATR operational documentation chapters related to CAT II precision
approaches are being revised (AFM 7-01-03 CATII Operation and FCOM
2-02-04 AFCS). The revision has been recently implemented for 42300/42-320 series and will be extended to the other aircraft types at their
next documentation normal revision during the year 2010.
The major evolution to notice is a change of the tasks management in the
operational procedure, as described in Chapter E. Flight Crew Operating
Procedures of this manual.
Until the effective revision of the ATR operational documentation, the
information contained in the Airplane Flight Manual shall prevail over the
content of this manual.
Your ATR Training and Flight Operations support team.
NoteTemporaire.indd 1
01/07/10 10:47
Introduction
The purpose of this guide is to provide ATR aircraft pilots and operators with information and
regulatory material relating to All Weather Operations.
Training pilots for All Weather Operations is the operator’s responsibility. This guide aims to
give pilots a good overview on low visibility operations and to help operators develop their
own documentation and their flight crew training programmes in order to obtain the Low
Visibility Operations approval from their national authority.
Most stated recommendations are issued from ICAO annexes and from FAA and EASA
regulations. Nevertheless, some national authorities may have additional requirements.
The content of this guide is intentionally limited to operations for which ATR aircraft have
a technical capability, that is to say: low visibility take-off, lower than standard Category I,
Category II, other than standard Category II and Category IIIA approaches.
The overall safety level of low visibility operations is achieved through the implementation of
specific rules and requirements equally concerning:
– the aircraft
– the airfield
– the flight crew
– the operator
All 4 fields are addressed in this guide but with an emphasis on the last two items being more
widely developed.
This guide incorporates features of the ATR -600 aircraft type due for entry into service by
2011. For the time being, low visibility approach certifications are still under progress and the
guide will be amended to develop these points specifically related to the -600 in later revision.
Introduction
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Contents
Contents
Chapter A. General
1. A brief history ........................................................................................................................................................................................................................................8
2. Economic aspects .........................................................................................................................................................................................................................8
3. Low Visibility Operations (LVO) concept...................................................................................................................................................9
3.1. General....................................................................................................................................................................................................................................................9
3.2. Low Visibility Take-Off (LVTO)..................................................................................................................................................................................9
3.3. Category II approaches................................................................................................................................................................................................10
3.4. Category IIIA approaches .........................................................................................................................................................................................10
3.5. Lower than standard Category I operation .......................................................................................................................................10
3.6. Other than Standard Category II operation ......................................................................................................................................10
4. Relevant regulations ..............................................................................................................................................................................................................10
4.1. Aeroplanes certification ..............................................................................................................................................................................................10
4.2. Airfield regulation .................................................................................................................................................................................................................10
4.3. Operational regulation ...................................................................................................................................................................................................11
5. Definitions ...............................................................................................................................................................................................................................................11
5.1. General................................................................................................................................................................................................................................................11
5.2. Categories of precision approach and landing operations ........................................................................................12
5.2.1. Category II (CAT II) .........................................................................................................................................................................................................12
5.2.2. Category IIIA (CAT IIIA) .............................................................................................................................................................................................13
5.2.3. Category IIIB (CAT IIIB) .............................................................................................................................................................................................13
5.2.4. Category IIIC (CAT IIIC).............................................................................................................................................................................................13
5.2.5. Lower than Standard Category I ....................................................................................................................................................................13
5.2 .6. Other than Standard Category II ....................................................................................................................................................................14
5.3. Summary ..........................................................................................................................................................................................................................................14
Chapter B. Revision of low visibility weather conditions
1. The characteristics of fog .............................................................................................................................................................................................16
1.1. Radiation fog ..............................................................................................................................................................................................................................16
1.2. Advection fog .............................................................................................................................................................................................................................17
1.3. Frontal / Precipitation fog .........................................................................................................................................................................................17
1.4. Upslope and valley fogs ..............................................................................................................................................................................................18
2. Effects of precipitation, wind and turbulences ..........................................................................................................................18
2.1. The effect of precipitation ........................................................................................................................................................................................18
2.2. The effect of wind and turbulences .............................................................................................................................................................19
3. Runway Visual Range (RVR)......................................................................................................................................................................................20
3.1. General................................................................................................................................................................................................................................................20
3.2. RVR measurements...........................................................................................................................................................................................................20
3.3. RVR use .............................................................................................................................................................................................................................................22
3.4. RVR practical limitation ...............................................................................................................................................................................................24
3.5. Conversion of reported meteorological visibility to RVR ...............................................................................................24
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4. Weather documentation ..................................................................................................................................................................................................25
4.1. Weather charts .........................................................................................................................................................................................................................25
4.2 TAF/METAR/SPECI ...............................................................................................................................................................................................................26
4.2.1. General .......................................................................................................................................................................................................................................26
4.2.2. TAF ..................................................................................................................................................................................................................................................26
4.2.3. METAR/SPECI .....................................................................................................................................................................................................................27
Chapter C. Aircraft requirements
1. Aircraft certification status .........................................................................................................................................................................................29
1.1. General................................................................................................................................................................................................................................................29
1.2. Guidance and landing systems .........................................................................................................................................................................29
1.2.1. CAT II approaches ..........................................................................................................................................................................................................29
1.2.2. CAT IIIA approaches with DH ≥50ft .............................................................................................................................................................30
1.2.3. Lower than standard CAT I and other than standard CAT II.............................................................................................30
1.2.4. Low visibility take-off ..................................................................................................................................................................................................30
1.3. System performances ....................................................................................................................................................................................................31
1.4. Aircraft Flight Manual content ............................................................................................................................................................................31
2. ATR automatic flight control system...........................................................................................................................................................31
2.1. AFCS on classic instruments ATR .................................................................................................................................................................31
2.2. AFCS on ATR -600 ...............................................................................................................................................................................................................33
3. Aircraft minimum equipment required .....................................................................................................................................................33
3.1. Classic instruments ATR ............................................................................................................................................................................................34
3.2. ATR -600 ............................................................................................................................................................................................................................................34
4. Aeroplane malfunctions ...................................................................................................................................................................................................34
4.1. ATR 72-500.....................................................................................................................................................................................................................................35
4.2. ATR -600 ............................................................................................................................................................................................................................................35
5. Maintenance ........................................................................................................................................................................................................................................36
Chapter D. Airfield requirements
1. Aerodrome approval...............................................................................................................................................................................................................38
2. Runway and taxiway characteristics..........................................................................................................................................................38
2.1. Runway length ..........................................................................................................................................................................................................................38
2.2. Runway width ............................................................................................................................................................................................................................38
2.3. Runway slope ............................................................................................................................................................................................................................38
2.4 Runway-holding position .............................................................................................................................................................................................38
3. Effects of pre-threshold terrain profile....................................................................................................................................................39
4. Obstacles clearances requirements............................................................................................................................................................39
5. Navaids - Characteristics and limitations ..........................................................................................................................................41
5.1. General................................................................................................................................................................................................................................................41
5.2. ILS characteristics ..............................................................................................................................................................................................................41
5.3. ILS performances .................................................................................................................................................................................................................42
5.4. ILS classification ...................................................................................................................................................................................................................43
5.5. ILS protection ............................................................................................................................................................................................................................44
6. Characteristics of the visual aids .....................................................................................................................................................................44
6.1. Runway markings.................................................................................................................................................................................................................44
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Contents
6.2. CAT II/III Lighting systems .......................................................................................................................................................................................45
6.2.1 Taxiway lights........................................................................................................................................................................................................................46
6.2.2. Stop bars ..................................................................................................................................................................................................................................46
6.2.3. Runway guard lights ....................................................................................................................................................................................................46
6.2.4. Runway lights ......................................................................................................................................................................................................................47
6.2.5. The approach lighting system ...........................................................................................................................................................................47
6.2.6. Lighting system condition .....................................................................................................................................................................................49
6.3. Lighting systems for Lower than standard CAT I and other than standard CAT II
approaches ...................................................................................................................................................................................................................................49
7. ATC Procedures.............................................................................................................................................................................................................................50
Chapter E. Flight crew operating procedures
1. General .........................................................................................................................................................................................................................................................52
2. Pre-flight procedures............................................................................................................................................................................................................52
3. On ground procedures and precautions...............................................................................................................................................53
3.1. General................................................................................................................................................................................................................................................53
3.2. Recommended procedures ....................................................................................................................................................................................53
3.2.1. Prior to taxiing ....................................................................................................................................................................................................................53
3.2.2. During taxi...............................................................................................................................................................................................................................53
3.2.3. Prior to approach phase ..........................................................................................................................................................................................54
3.3. Usual difficulties.....................................................................................................................................................................................................................54
3.4. Airport moving map...........................................................................................................................................................................................................55
3.4.1. Electronic Flight Bag (EFB)...................................................................................................................................................................................55
3.4.2. ATR -600 ....................................................................................................................................................................................................................................55
4. Low visibility take-off (LVTO) ...................................................................................................................................................................................55
4.1. General................................................................................................................................................................................................................................................55
4.2. Low Visibility Take-Off under European regulation (EU-OPS) .................................................................................56
5. Approach preparation..........................................................................................................................................................................................................57
5.1. Conditions at destination / at the alternate aerodrome ..................................................................................................57
5.2. Aircraft capability .................................................................................................................................................................................................................57
5.3. Fuel calculation .......................................................................................................................................................................................................................57
5.4. DH setting .......................................................................................................................................................................................................................................58
5.5. Approach briefing.................................................................................................................................................................................................................58
5.6. Cabin crew information................................................................................................................................................................................................58
5.7. Seat position ...............................................................................................................................................................................................................................59
6. Normal procedures for low visibility approaches ..................................................................................................................59
6.1. General................................................................................................................................................................................................................................................59
6.2. Approach ban / RVR controlling ......................................................................................................................................................................59
6.3. Task sharing .................................................................................................................................................................................................................................60
6.4. Normal procedures on classic instruments ATR for CAT II approaches ..................................................60
6.5. Normal procedures and task sharing for CAT III, other than standard CAT II and
lower than standard CAT I approaches on ATR -600.......................................................................................................... 64
6.6.Visual segment at DH and minimum visual references......................................................................................................64
6.7. Loss of visual references below DH ...........................................................................................................................................................65
7. Abnormal procedures ..........................................................................................................................................................................................................65
7.1. General................................................................................................................................................................................................................................................65
Contents
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7.2. Failure treatment concept ........................................................................................................................................................................................66
7.3. Failure treatment on classic instruments ATR .............................................................................................................................66
7.4. Failure treatment on ATR -600 ............................................................................................................................................................................67
7.5. Maximum ILS deviation allowed ......................................................................................................................................................................67
8. Effects of failure of ground equipment....................................................................................................................................................68
Chapter F. Flight crew training and qualification
1. General .........................................................................................................................................................................................................................................................71
2. Ground training...............................................................................................................................................................................................................................71
3. Simulator training and checking ........................................................................................................................................................................72
3.1. Full training program .......................................................................................................................................................................................................72
3.2. Training for flight crew members with Category II or Category III experience................................74
3.3. Training for flight crew members flying on classic instruments ATR and on ATR -600 .......74
3.4. Flight crew qualification ..............................................................................................................................................................................................74
4. Line training..........................................................................................................................................................................................................................................74
5. Type and command experience ..........................................................................................................................................................................75
6. Recurrent training and checking.......................................................................................................................................................................75
7. The qualification process of flight crew under EASA regulation: overview ...............................76
Chapter G. Operator’s duties
1. Establishing operating minima .............................................................................................................................................................................78
1.1. General................................................................................................................................................................................................................................................78
1.2. EASA take-off minima ....................................................................................................................................................................................................79
1.3. EASA CAT II minima ..........................................................................................................................................................................................................79
1.4. EASA CAT III minima ........................................................................................................................................................................................................79
1.5. EASA Lower than standard CAT I minima ..........................................................................................................................................80
1.6. EASA other than standard CAT II minima ...........................................................................................................................................80
1.7. Operating minima publication.............................................................................................................................................................................81
2. Operations manual content .......................................................................................................................................................................................81
3. Operational demonstration.........................................................................................................................................................................................82
3.1. General................................................................................................................................................................................................................................................82
3.2. Operational demonstration under European regulation .................................................................................................83
3.3. Operational demonstration under FAA regulation ..................................................................................................................84
4. Eligible aerodromes and runways ...................................................................................................................................................................84
5. Continuous monitoring ......................................................................................................................................................................................................85
6. Operator approval process .........................................................................................................................................................................................85
6.1. Prerequisite / transitional period.....................................................................................................................................................................85
6.2. Operational approval file ............................................................................................................................................................................................86
6.3. Sequencing of action during the approval process ..............................................................................................................86
Abbreviations
...............................................................................................................................................................................................................
Contents
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A. General
A - General
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A. General
1. A brief history
Landing in Low Visibility Conditions was made possible by huge improvements in aircraft automatic control systems
over the last 40 years coupled with stringent requirements for airfield equipment and crew qualification.
All modern aircraft are now certificated for CAT II operations and many for CAT III operations. CAT II approaches approval has been granted to ATR aircraft at the initial certification in 1985. The new series ATR 42-600 and ATR 72-600
will be certificated for CAT II and CAT IIIA approaches.
Figure A1: ATR aircraft in low visibility conditions at parking
2. Economic aspects
There is an overall positive economic impact for the adoption of Low Visibility Operations.
In certain regions of the world, the best way for an airline to maintain its schedule all year round without any diversion
due to weather, is to be approved to perform Low Visibility Operations.
There may initially be a cost implication to implement Low Visibility Operations (CAT II/III equipments, flight crew training...). However, it is the only way to keep in-line services operational throughout the whole year with a minimum
number of diversions. Weather conditions mainly depend on the airfield location, nevertheless actual CAT II/III conditions may occur at any airfield depending on the periods of the year. Diversions and delayed flights are expensive for
an airline, due not only to passenger compensation costs but also due to the resulting bad “image”. For these reasons,
getting operational approval for CAT II/III approaches and Low Visibility Take-Off can be considered as a necessary step
in the evolution of a modern airline.
There may further be a slight positive environmental impact from a higher landing success rate at destination, plus a
consequential reduction in fuel consumption.
A - General
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3. Low Visibility Operations (LVO) concept
3.1. General
When developing low visibility procedures, the airline objective is to achieve under low visibility conditions both a level
of safety and a rate of reliability equivalent to those achieved during normal operating conditions.
Take-off and taxing in low visibility conditions involves specific operating procedures and suitable airport installations
(runway lighting system, RVR measurement system, ...) but does not require specific on board equipment.
Landing in low visibility conditions is made possible using high performances ground ILS equipment together with the
onboard receivers and the automatic flight control system of the aircraft. The decision to land is taken in very close
proximity to the ground (between 200ft and 0 ft, depending on the category of the approach); pilots see the runway
lights only a few seconds before touchdown, therefore there is no margin for error. The desired level of safety is
achieved through:
– Ground ILS facility,
– Airborne equipment,
– Visual aids (runway markings, lighting systems),
– Flight crew training,
– Flight crew procedures,
– Air Traffic Control procedures,
– Aircraft maintenance,
– Airfield maintenance,
– Criteria for obstacle clearance.
The basic principles governing Low Visibility Operations are that:
Q
the
aerodrome satisfies the ICAO standards for LVO, including visual and non-visual aids, runway characteristics, obstacle clearance area, RVR measurements, ATC procedures… The aerodrome is approved for such
operations by the State in which the aerodrome is located.
Q
the
aeroplane is certificated for such operations. Limitations and conditions specified in the Aircraft Flight
Manual are respected. The aeroplane and its equipments are maintained in accordance with the approved
maintenance manual.
Q
each
flight crew member has successfully completed the training and checking program approved by the
operator’s Authority.
Q
operating
procedures have been established and are applied by flight crew members. Those procedures
cover task sharing during Low Visibility Take-Off and approaches and the actions to be taken in case of equipment failure.
Q
the
operator has obtained from his national authority an operational approval to perform such operations.
3.2. Low Visibility Take-Off (LVTO)
When visibility decreases the pilot must continue to be able to judge the aeroplane’s lateral position to keep it within
acceptable limits relative to the runway centre line throughout the take-off roll and eventually during the aborted takeoff phase.
The basic information required by the pilot is normally provided by external visual cues but these may be supplemented
by instrument derived information. When take-off is performed using only external visual cues, the runway lighting
system is essential.
A - General
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A. General
3.3. Category II approaches
In Category II operations, the ILS precision instrument approach is performed using the automatic flight control system
down to below the Decision Height (typically 100ft). At the Decision Height, the visual references should be sufficient to
allow the pilot to continue the approach and to perform a manual landing using only external visual cues.
3.4. Category IIIA approaches
In Category III the Decision Height and the Runway Visual Range are lower than in CAT II operations. The time from the
decision height to the start of the flare is shorter. To preserve the safety level it has been considered necessary that the
ILS precision instrument approach be performed using the automatic flight control system right until the aircraft is on the
ground. Approach, flare and landing are performed automatically. At the Decision Height, the visual references should
be sufficient to allow the pilot to decide if the aircraft will land within the touchdown zone.
The main difference between CAT II and CAT III operations is that in Category II conditions the pilot has enough time
and sufficient visual references to permit a manual landing, whereas it is not the case when in Category III conditions
and an automatic landing has to be performed.
3.5. Lower than Standard Category I operation
On aerodromes only supporting Category I approach, the Decision Height can not be lower than 200ft. Nevertheless, depending on the ILS ground equipment performance, the required Runway Visual Range can be lower than the
Standard CAT I RVR if the aircraft is equipped with an auto-land system approved for CAT III operations. In order to be
authorised to use reduced RVR, the approach must be flown auto-coupled to an auto-land.
3.6. Other than Standard Category II operation
Category II or III approach can not be published on aerodromes using limited facilities for approach lighting and runway
lighting. On those aerodromes, aircraft able to perform an auto-land can consider the use of a Category II Decision
Height (typically 100ft) with an RVR higher than the one of a Standard Category II approach. Such approaches are
referred to as other than Standard Category II operation.
4. Relevant regulations
4.1. Aeroplanes certification
FAA
– Advisory circular AC 120-29A, Criteria for approval of Category I and Category II weather minima for approach
– Advisory circular AC 120-28D, Criteria for approval of Category III weather minima for take-off, landing, and
rollout
– Advisory circular AC 20-57, Automatic Landing Systems
EASA
– CS AWO, Certification Specifications for All Weather Operations
4.2. Airfield regulation
ICAO
–
–
–
–
Annex 14 Volume 1, Aerodrome Design and Operations
Annex 10 Volume 1, Radio navigation aids (ILS specifications)
PANS-OPS (Doc 8168) Volume 2, Construction of visual and instrument flight procedures
Doc 9328, Manual of Runway Visual Range Observing and Reporting Practices
A - General
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Other
Each State may have its own policy to approve its aerodromes for Low Visibility Operations. Those regulations
are not supposed to be less restrictive than ICAO Annexes otherwise differences should be notified.
4.3. Operational regulation
ICAO
– Annex 6, Operation of Aircraft
– Doc 9365, Manual of All Weather Operations
FAA
– Advisory circular AC 120-29A, Criteria for approval of Category I and Category II weather minima for approach
– Advisory circular AC 120-28D, Criteria for approval of Category III weather minima for take-off, landing, and
rollout
EASA
– EU-OPS Subpart E, All Weather Operations
Other
Each State may have its own operational regulation
It is worth noting that harmonisation was conducted between EASA and FAA operational regulations for CAT II and CAT
III operations which are now very similar.
5. Definitions
5.1. General
All Weather Operations
ICAO Doc 9365 – Foreword
Any taxi, take-off and landing operations in conditions where visual reference is limited by weather conditions.
Aerodrome operating minima for take-off
ICAO Annex 6 – Chapter 1: Definition
The limits of usability of an aerodrome expressed in terms of runway visual range and/or visibility and, if necessary,
cloud conditions.
Aerodrome operating minima for precision approach and landing operations
ICAO Annex 6 – Chapter 1: Definition
The limits of usability of an aerodrome expressed in terms of visibility and/or runway visual range and decision
altitude/height (DA/H) as appropriate to the category of the operation.
Decision altitude (DA) or decision height (DH)
ICAO Annex 6 – Chapter 1: Definition
A specified altitude or height in the precision approach or approach with vertical guidance at which a missed
approach must be initiated if the required visual reference to continue the approach has not been established.
Note: Decision altitude (DA) is referenced to mean sea level and decision height (DH) is referenced to the
threshold elevation.
A - General
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A. General
According to EASA, the Decision Height for Category II, Category III and other than Standard Category II operations is
determined by means of radio-altimeter.
For some specific Category II approaches, the FAA gives free choice on DH recognition (radio-altimeter, inner markers
or barometric altimeter).
Low Visibility Operations (LVO)
For this specific document, LVO includes Low Visibility Take-Off, Category II approaches, Category IIl approaches, other
than Standard CAT II and lower than Standard CAT I approaches.
Low Visibility Procedures (LVP) - EASA definition
EU-OPS 1.435 Terminology
Procedures applied at an aerodrome for the purpose of ensuring safe operations during Lower than Standard
Category I, Other than Standard Category II, Category II and III approaches and Low Visibility Take-Offs.
Low Visibility Take-Off (LVTO) - EASA definition
EU-OPS 1.435 Terminology
A Low Visibility Take-Off is a take off where the Runway Visual Range is less than 400m.
Runway visual range (RVR)
ICAO Annex 6 – Chapter 1: Definition
The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings
or the lights delineating the runway or identifying its centre line.
NOTE: Category II and Category III instrument approach and landing operations shall not be authorised unless RVR information is provided.
5.2. Categories of precision approach and landing
operations
5.2.1. Category II (CAT II)
ICAO and FAA
ICAO Annex 6 – Chapter 1: Definition
AC 120-29A - Appendix 1: Definitions and acronyms
A Category II operation is a precision instrument approach and landing with a decision height lower than 60 m
(200 ft), but not lower than 30 m (100 ft), and a runway visual range not less than 350 m.
EASA
EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (f)
A Category II operation is a precision instrument approach and landing using ILS or MLS with a decision height
below 200 ft but not lower than 100 ft; and a runway visual range of not less than 300 m.
NOTE: For the minimum RVR requested, the EASA definition is slightly different from the ICAO and FAA definitions: not less than 350 m for
ICAO and FAA but not less 300 m for EASA.
A - General
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5.2.2. Category IIIA (CAT IIIA)
ICAO and FAA
ICAO Annex 6 – Chapter 1: Definition
AC 120-29A - Appendix 1: Definitions and acronyms
A Category IIIA operation is a precision instrument approach and landing with a decision height lower than 30 m
(100 ft) or no decision height; and a runway visual range not less than 200 m.
EASA
EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (g)
A Category IIIA operation is a precision instrument approach and landing using ILS or MLS with a decision height
lower than 100 ft; and a runway visual range not less than 200 m.
NOTE: The ICAO and FAA regulations differ from EASA by considering CAT IIIA approaches with no DH. EASA systematically associates CAT
IIIA approaches with a decision height.
5.2.3. Category IIIB (CAT IIIB)
ICAO and FAA
ICAO Annex 6 – Chapter 1: Definition
AC 120-29A - Appendix 1: Definitions and acronyms
A Category IIIB operation is a precision instrument approach and landing with a decision height lower than 15 m
(50 ft) or no decision height; and a runway visual range less than 200m but not less than 50 m.
EASA
EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima (g)
A Category IIIB operation is a precision instrument approach and landing using ILS or MLS with a decision height
lower than 100 ft, or no decision height; and a runway visual range lower than 200 m but not less than 75 m.
NOTE: The ICAO and FAA regulations differ from EASA on the minimum RVR associated with CAT III B approaches.
5.2.4. Category IIIC (CAT IIIC)
ICAO and FAA
ICAO Annex 6 – Chapter 1: Definition
AC 120-29A - Appendix 1: Definitions and acronyms
A Category IIIC operation is a precision instrument approach and landing with no decision height and no runway
visual range limitations.
EASA
CAT III C operations are not currently authorised so EASA does not make reference to this sub-category.
5.2.5. Lower than Standard Category I
EASA
EU-OPS 1.435 Terminology
A Category I Instrument Approach and Landing Operation using Category I DH, with an RVR lower than would
normally be associated with the applicable DH.
A - General
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A. General
5.2.6. Other than Standard Category II
EASA
EU-OPS 1.435 Terminology
A Category II Instrument Approach and Landing Operation to a runway where some or all of the elements of the
ICAO Annex 14 Precision Approach Category II lighting system are not available.
5.3. Summary
Definitions of Categories of precision approach give the lowest acceptable minima. During operations those values
may be limited by aircraft capability, by airfield limitation, by crew individual qualification or by operator’s authorisation.
Lower than stand.
CAT I
DH
ICAO
FAA
EASA
–
–
DH ≥200ft
RVR
–
–
400m≤RVR
DH
100ft ≤ DH < 200ft
100ft ≤ DH < 200ft
100ft ≤ DH < 200ft
CAT II
RVR
350m ≤ RVR
1200ft ≤ RVR
350m ≤ RVR < 800m
1200ft ≤ RVR < 2400ft
300m ≤ RVR
1000ft ≤ RVR
Other than stand.
CAT II
DH
–
–
100ft ≤ DH < 200ft
RVR
–
–
350m ≤ RVR
DH
No DH or DH < 100ft
No DH or DH < 100ft
DH < 100ft
CAT IIIA
RVR
200m ≤ RVR
700ft ≤ RVR
200m ≤ RVR
700ft ≤ RVR
200m ≤ RVR
700ft ≤ RVR
DH
DH < 50ft or No DH
DH < 50ft or No DH
DH < 100ft or No DH
RVR
50m ≤ RVR < 200m
150ft ≤ RVR < 700ft
50m ≤ RVR < 200m
150ft ≤ RVR < 700ft
75m ≤ RVR < 200m
250ft ≤ RVR < 700ft
DH
No DH
No DH
–
RVR
No RVR limitation
No RVR limitation
–
CAT IIIB
CAT IIIC
Table A1: Summary of approach category definitions, in accordance with ICAO, FAA, and EASA Regulations
ICAO Annex 6 – Chapter 1: Definition
Note: Where decision height (DH) and runway visual range (RVR) fall into different categories of operation, the
instrument approach and landing operation would be conducted in accordance with the requirements of the
most demanding category (e.g. an operation with a DH in the range of CAT IIIA but with an RVR in the range of
CAT IIIB would be considered a CAT IIIB operation or an operation with a DH in the range of CAT II but with an
RVR in the range of CAT I would be considered a CAT II operation).
Acceptable operational correspondance meter/feet (according to ICAO)
15m = 50ft
30m = 100ft
50m = 150ft
100m = 300ft
150m = 500ft
175m = 600ft
300m = 1000ft
350m = 1200ft
500m = 1600ft
600m = 2000ft
800m = 2400ft
1000m = 3000ft
1600m = 5000ft
75m = 250ft
200m = 700ft
550m = 1800ft
1200m = 4000ft
A - General
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1. The characteristics of fog
Although visibility may be reduced by the presence in the air of solid particles such as smoke, dust or sand, most of
the time low visibility conditions are caused by fog.
There is fog if the visibility is less than 1000m and the obscuring agent is water droplets. Fog differs from rain or mist in
that its water particles are more minute and suspended and do not fall earthward.
The droplets of water suspended in the air near the earth’s surface act on scattering the light and thus reduce the visibility near the ground.
The formation of a fog layer occurs when a moist air mass is cooled to its saturation point (dew point): the water vapor
within the air mass condenses on small particles in the air to form liquid cloud droplets. This cooling can be the result of:
– radiative processes (radiation fog),
– advection of warm air over cold surfaces (advection fog),
– evaporation of precipitation (precipitation or frontal fog),
– movement of humid air up or down the hillside (upslope fog or valley fog).
1.1. Radiation fog
Radiation fog is caused by the radiation cooling of earth’s surface.
After sunset, earth receives no heat from the sun, but its surface continues to reradiate heat. The surface begins to
cool because of this heat loss. As the Earth cools, the layer of air adjacent to the surface is cooled by conduction.
This causes the layer near earth to be cooler than the air immediately above it, a condition called an inversion. If the air
beneath the inversion layer is sufficiently moist and cools to its dew point, fog forms.
In case of a calm wind and since air is a poor conductor of heat, this cooling by conduction affects only a very shallow layer i.e. a few inches deep. Wind of low speed (3 to 5 knots) causes slight, turbulent currents. Such turbulence is
enough to spread the fog through deeper layers.
As nocturnal cooling continues, the air temperature drops further, more moisture is condensed, and fog becomes
deeper and denser. If wind speed is between 5 and 10 knots then the fog will usually thicken vertically. Winds greater
than 10 knots usually result in the formation of low scud, stratus, or stratocumulus.
At sunrise, the Earth is heated. Radiation from the warming surface heats the lower air, causing an evaporation of the
lower part of fog, thereby giving the appearance of lifting fog. Before noon, the radiated heat from the warming of the
earth surface destroys the inversion process, so then the fog evaporates into warmed air.
Radiation fog appears over land, it never forms over a water surface and it may cover a wide area. The conditions giving
rise to the formation of radiating fog are:
– cloudless nights, allowing the earth to lose heat by radiation,
– moist air that requires a little cooling to reach the dew point temperature,
– light winds (5-7kts) to mix the lower layers of air, thereby thickening the fog layer.
Such conditions are common in high-pressure areas during autumn and winter in temperate zones.
Further radiational
cooling at top of
fog layer, deepens it.
Heat radiating from the
surface at night, cools
the bottom air until it
reaches saturation.
Fog forms first at
the surface, thickening
as cooling continues.
Figure B1: Radiation fog
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1.2. Advection fog
Advection fogs are formed when air moves either over a cooler surface or over a warmer moist surface and, as a
result, the air mass reaches saturation.
Most often this occurs when a moist air mass moves over a cold surface with a temperature lower than the dew point
of the moving air. Cooling from below takes place and gradually builds up a fog layer. The cooling rate depends on
the wind speed and the difference between the air temperature and the temperature of the surface over which the air
travels. A low wind speed heightens the likelihood as the air remains in contact with the surface long enough to sufficiently cool the air layer.
Advection fogs are often persistent since the weather situation that forms them can last a day or more. Usually, either a
frontal passage with a change of air-mass or a major change in wind direction are needed for the dissipation of advection fog.
Fog forms
Colder surface
Warmer, moist air
moves over a colder
surface and its temperature drops
Figure B2: Advection fog
1.3. Frontal / Precipitation fog
This fog type is due to the evaporation of falling rain and occurs under the frontal surface in the cold air mass. Precipitation falls from the lifted warm air through the cold air. Evaporation from the rain continues as long as the raindrop
temperature is higher than the temperature of the air, even though the cold air is already saturated. Naturally, the
upper regions become saturated first because, at higher altitude, both the temperature and dew point are lower. As
rain evaporation continues, a layer of clouds begins to build down from the frontal surface. Eventually, this cloud layer
extends to the ground turning into fog.
Cold fronts usually move so rapidly and have such narrow bands of precipitation and high wind speeds that a cold front
fog is comparatively rare and short lived. A warm front fog, on the other hand, is fairly common. Warm-front fog may
cover a wide area. Also this type of fog is deep because it extends from the ground to the frontal surface.
precipitation falls through warm air
rain cloud
warm air
front
cold air
fog
evaporation leads to saturation
Figure B3: Frontal fog
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1.4. Upslope and valley fogs
Upslope fog is caused by adiabatic cooling of rising air. When moist, warm air is forced to move over a terrain obstacle, it cools to some degree as it rises, the degree of cooling depending on the amount of rise. During that cooling, if the
air temperature falls below dew point, the resulting condensation will form a cloud. The air must be stable before it starts
its motion, so that lifting does not cause convection, nor vertical currents, which would dissipate the fog. Wind speed
is needed, of course, to cause upslope motion. This type of fog is deep and requires considerable time to dissipate.
Fog forms
on slope.
Moist air flows
toward slope.
As air rises with the
terrain, it cools to
condensation temperature.
Figure B4: Upslope fog
Valley fog forms during the evening as a result of air being cooled by radiation on slopy topographical features. As this
air becomes denser than its surroundings, it starts going down the slope. This results in the creation of a pool of cold
air at valley floor level. If the air is cold enough to reach its dew point, fog formation occurs.
Air cools at
higher elevations.
Fog forms in valley
Cold air drains
downslope
into valley.
Cold air drainage
reduces air temperature in
valley to condensation point.
Figure B5: Valley fog
2. Effects of precipitation, wind and
turbulences
2.1. The effect of precipitation
Precipitation includes drizzle, rain, snow, ice crystals and hail. Although liquid precipitation on windshields can be
a serious irritation for pilots, it does not seriously limit visibility, except when rain or drizzle is associated with fog. Even
heavy rain does not usually limit visibility to less than 1 km.
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Figure B6: View from windshield during precipitation
Snow fall is a different matter; a very light snowfall alone can reduce visibility considerably. As snowfall becomes heavy,
visibility may drop to only a few meters.
Blowing snow is to be expected when loose snow is raised by the wind. The limited visibility may extend to a considerable height. This problem is quite significant in cold climates.
Snow also affects approach and runway lighting intensity, thus reducing the chances of acquiring visual cues at Decision Height. Furthermore, the actual visibility may be less than the horizontally measured visibility because of the lack
of contrast between the approach lighting and the snow-covered ground.
Figure B7: Snowy environment
2.2. The effect of wind and turbulences
Low visibility conditions are usually due to the presence of fog which often appears in anticyclones. Therefore most
of the time CAT II and CAT III approaches are performed with light or moderate wind, except on a limited number of
airports where specific conditions may associate fog and strong wind.
For CAT II operations, the ATR flight manual states the maximum “demonstrated wind”. It corresponds to the worth
wind conditions encountered during certification flight tests. Therefore it should not be considered as a limitation. It is
the operator’s responsibility to set the limit as per his national operational regulations.
CAT III operations are constrained in respect of the wind component. Unlike the demonstrated wind for manual landings, the autoland wind capabilities are always limiting. The maximum crosswind values for auto-land operations are
often less than the manually demonstrated crosswind landings.
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effect of tailwind: in some airports, not all runways are equipped for cat II/III operations. Therefore in low
visibility conditions, a runway may be in use in spite of a light tail wind. The main consequence is a higher ground
speed, reducing the time between DH and touchdown. During CAT II approaches, the pilot has less time to take
control of the aircraft after the auto pilot disconnection.
Q
The
effect of crosswind: At decision height the pilot may have more difficulties to acquire the visual references which are not located on the aircraft axis. Before Decision Height, according to the drift resulting from the
crosswind, the pilot has to anticipate where to search visual cues. In CAT III operations the ATR autoland system
performs the de-crab but does not follow the runway axis when the aircraft is on ground (no roll out function).
Q
The
effect of turbulences: turbulences will increase the pilot’s workload to maintain the approach speed
within acceptable limits. In case of severe turbulences, there is also a risk of autopilot disconnection, leading to
a missed approach.
3. Runway Visual Range (RVR)
3.1. General
The Runway Visual Range (RVR) is an instrumentally derived value that represents the horizontal distance a pilot may
see down the runway. It is the maximum distance at which the runway markings or the runway lights can be seen by
the pilot of a lined up aircraft.
The purpose of RVR is to provide pilots and air traffic services with information on runway visibility conditions during
periods of low visibility.
ICAO Doc 9328 Chapter 11, Transmission and reporting practices, states the following practices for RVR reporting:
– RVR must be assessed on all runways intended for Categories II and III approaches.
– Where RVR assessments are required, they should be made and reported throughout periods when either the
visibility or the RVR is observed to be less than 1500m.
– The lower limit of the reporting range should be 50 m and the upper limit should be 2000 m.
– The reporting increments should be 25 m up to 400 m RVR,
50 m between 400 and 800 m RVR,
100 m for values of RVR above 800 m.
– The measurements should be averaged over a period of one minute.
3.2. RVR measurements
The RVR value is determined by calibrated instruments (i.e. transmissometer or forward scatter meter) located alongside and higher than the centre line of the runway.
A transmissometer measures the transmittance of the atmosphere between two points in space, over a specified path
length or baseline. It consists essentially of a transmitter that directs a beam of light at a photo detector in a receiver unit.
receiver
transmitter
optical axis
height mini: 1.50 m
maxi: 1.00 m
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Q
The
measurement reference = 30.00 m
electronic box
frangible post
data
concentrator
optical fibres link
Figure B8: Transmissometer principle
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A scatter meter estimates the extinction coefficient by measuring the flux scattered from a light beam by particles
present in the atmosphere. It consists of a transmitter and a receiver spaced by about one meter.
Transmitter
Receiver
Figure B9: Forward scatter meter principle
RVR is calculated taking into account the measured quantity (i.e. transmittance or extinction coefficient), the characteristics of the lights and the expected detection sensitivity of the pilot’s eye under prevailing conditions of background
luminance.
Figure B10: Transmissometer
Figure B11: Forward scatter meter
The RVR measurement system includes:
– instruments (transmissometers or scatter meters),
– background luminance sensor: it measures the brightness of the background, against which the pilot would
view the runway lights,
– a runway light intensity monitor: it provides information on runway light setting,
– RVR computer (dedicated or part of the integrated observing system),
– digital displays of RVR in the appropriate Air Traffic Services unit,
– a recorder to archive data over a given period of time.
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Figure B12: RVR measurement
The visibility sensors are strategically located along the runway to provide RVR measurements associated with three
basic portions of a runway:
– the touchdown zone (TDZ), located about 300m from the threshold
– the mid-runway portion (MID), located at a distance of 1000 m to 1 500 m from the threshold
– the rollout portion or stop end located at a distance of about 300 m from the end of the runway
NOTE: For runways less than 2400m, RVR is normally provided for TDZ and Rollout only.
The lateral position of the sensors should be within 120m of the runway centreline and the height above runway should
be approximately 2.5 m.
In certain conditions the RVR may be measured by the pilot or other weather observers. Typically the RVR may be
evaluated by the pilot at take-off position, by counting the number of either the runway edge lights or the centreline
lights that are visible.
3.3. RVR use
Operating minima are expressed in terms of DH and RVR for approach and landing but exclusively in terms of RVR for
take-off (please refer to Paragraph G.1, Establishing operating minima).
Before commencing a take-off or an approach to land, the crew must satisfy itself that the RVR reported by air traffic
services is equal to, or better than, its operating minima.
Take-off
The minimum RVR required for a take-off should provide the pilot with sufficient visual references to control the aeroplane until it is airborne, or until the end of an abandoned take-off. This minimum RVR value is to be compared to the
reported RVR which represents the visual segment available at the take-off position.
Approach and landing
For approach and landing, the minimum RVR associated to a Decision Height is intended to provide a high probability
that the required visual references will be available at that decision height. The visual references required (please refer to
Paragraph E.6.6, Visual segment at DH and minimum visual references) at and below DH depend on the nature of the task
the pilot has to carry out (manual landing or monitoring of an autoland).
The reported RVR is an horizontal measure made on the ground while the pilot will normally be looking along a slant
path at approach Iights. It is probable that the fog will be less dense at ground level than it is above ground level and
slant visibility will probably be Iess than the horizontal visibility at ground level too. Thus, the most relevant information
for the pilot is the slant visual range (SVR); however, as practical methods of measuring SVR have not yet been developed, only the RVR measurement is made available.
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9=9
3PTP[VM
]PZPVU
3PTP[VM
]PZPVU
:=9
Figure B13: RVR and SVR
A geometrical relation can be used to compute the SVR required for the pilot to visually acquire the specified visual
segment in relation to the obscured segment.
There exist a number of models to convert required SVR into required RVR. They take into account the increase of fog
density with the height and they provide SVR/RVR ratios as a function of eyes height. It is then possible to compute a
minimum RVR as a function of the DH and of the required visual segment.
7PSV[L`LZM[
‡WP[JO
/VYPaVU[HSYLMLYLUJL
‡*\[VMM
HUNSL
M[T
:=9
‡
:LNTLU[VIZJ\YLK M[T
=PZ\HSZLNTLU[
Figure B14: Visual and Obscured segment
SVR / RVR
1
0,9
0,8
0,7
0,6
0,5
0,4
0
25
50
75
100
125
150
175
Pilot’s eyes height (ft)
Figure B15: Evolution of SVR/RVR ratio depending on height
Even if such methods enable to deal with the DH/RVR relationship in respect of Category II and III operations, the minimum RVR values set in most current operational regulations have been established by also taking into account various
real-life operating experiences which have given satisfactory results over a long period. However it is worth noting that
these RVR values, published in tables of operating minima, on their own, have no intrinsic meaning; they have significance only in conjunction with a set of operating policies and procedures.
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3.4. RVR practical limitation
The reported RVR is an instrumentally derived value that has significant limitations. It can be greater than, or less than,
the actual visibility available to a pilot’s eye. None of the values measured on the ground can accurately indicate whether
or not the pilot will have the required visual reference when at decision height.
Main error conditions are as follows:
– RVR is measured horizontally while the pilot is looking along a slant path,
– unusual daylight, such as when a runway is aligned with a sunrise or sunset conditions in shallow or patchy fog,
– spatial variations in the weather phenomenon between the pilot‘s view and the location where the RVR is measured (e.g. patchy fog or obscuration varying rapidly in time),
– measurement errors from the sensor measuring the extinction coefficient or the transmittance,
– angular and temporal variations in light intensity,
– differences between the actual and assumed runway light intensity,
– differences in background luminance between the pilot‘s view and the direction where the background luminance is measured, or errors in background luminance measurements.
Figure B16: Distorted vision through the windshield
Figure B17: Shallow or patchy fog
Furthermore, when assessing RVR, no account is taken of the effects on the pilot‘s vision of factors such as:
– the transmittance of the windshield of the aircraft,
– rain on the windscreen,
– the level of cockpit lighting,
– the illumination to which the pilot has been exposed prior to take-off or landing such as apron floodlighting, very
bright fog and flying over bright approach lights,
– physical and psychological conditions, e.g. tiredness or stress.
3.5. Conversion of reported meteorological visibility to RVR
On aerodromes where there is no instrument to measure the RVR, the only information transmitted to the pilot by Air
traffic services is the meteorological visibility. To compare the transmitted value to his operating minima (expressed in
terms of RVR), the pilot needs to convert the reported meteorological visibility into RVR. This conversion is prohibited
for CAT II and CATIII operations. For other types of operations, the regulatory Authorities usually specify the rules for
such conversion.
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For example the European regulation states that:
EU-OPS 1.430 - Appendix 1 (new): Aerodrome operating minima
(l) Conversion of reported meteorological visibility to RVR/CMV.
An operator must ensure that a meteorological visibility to RVR/CMV conversion is not used for take-off, for
calculating any other required RVR minimum less than 800m, or when reported RVR is available. (…)
In all other circumstances an operator must ensure that the following Table is used:
Lighting elements in operation
RVR/CMV= Report Met Visibility x
Day
Night
Hi approach and runway lighting
1.5
2
Any type of lighting installation other than above
1.5
1.5
1
Not applicable
No Lighting
Note: If the RVR is reported as being above the maximum value assessed by the aerodrome operator, e.g. “RVR
more than 1 500 meters”, it is not considered to be a reported RVR in this context and the Conversion Table may
be used.
Amongst the Low Visibility Operations covered by this document, only lower than Standard CAT I is concerned by this
conversion.
4. Weather documentation
During flight preparation the weather document analysis should enable the flight crew to identify or assess the risk of
encountering low visibility conditions.
4.1. Weather charts
Weather charts cover a large area and are not intended for detection of low visibility condition on a specific airport,
nevertheless significant weather symbols inform where visibility reducing weather phenomena are likely to appear. Such
information allows the crew to anticipate weather degradation and to be prepared to face low visibility conditions.
'UL]]OH
+DLO
5DLQ
6HYHUHVDQGRUGXVWKD]H
6KRZHU
6QRZ
:LGHVSUHDGEORZLQJVQRZ
:LGHVSUHDGIRJ
:LGHVSUHDGKD]H
:LGHVSUHDGPLVW
:LGHVSUHDGVDQGVWRUPRUGXVWVWRUP
:LGHVSUHDGVPRNH
Figure B18: Symbol of weather phenomena affecting visibility
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4.2 TAF/METAR/ SPECI
The Information provided in the following paragraphs is voluntarily limited to elements affecting visibility.
4.2.1. General
A METAR states the weather observed on an aerodrome during the last 10 minutes prior to the observation time. It is
issued twice every hour. At some airports it may be issued only once an hour. If the weather changes significantly from
the last METAR a special observation report (SPECI) is issued.
The TAFs are meteorological forecasting at airport. It is worth noting that RVRs are never forecasted and thus never
included in TAF messages. Only the horizontal meteorological visibility is provided.
Range and resolution of visibility in TAF, METAR and SPECI:
Horizontal visibility range
Resolution
Vertical visibility
Resolution
0000 m – 0800 m
50 m
VV000 – VV020
100ft (e.g. 160ft → VV001; 2000ft → VV020)
0800 m – 5000 m
100 m
VV ///
No vertical vis at all
5000 m – 10000 m
1000 m
Weather phenomena affecting visibility are reported into TAF METAR and SPECI using the following information.
Forecast weather abbreviations
DZ
RA
SN
SG
IC
PL
GR
drizzle
rain
snow
snow grains
ice crystals (diamond dust)
ice pellets
hail
GS small hail and/or
snow pellets
BR mist
FG fog
FU smoke
VA volcanic ash
DU widespread dust
SA
HZ
PO
SQ
FC
SS
DS
sand
haze
dust/sand whirls (dust devils)
squall
funnel cloud(s) (tornado and waterspout)
sandstorm
duststorm
Examples
+ SHRA
FZDZ
+ TSSNGR
heavy shower of rain
moderate freezing drizzle
thunderstorm with heavy snow and hail
TSSN
SNRA
thunderstorm with moderate snow
moderate snow and rain
4.2.2. TAF
Below is a TAF message typical of CAT II conditions forecasting:
LFBO
150500Z
Airport
identification
Day of issue 15
at 05TU
150615
36003KT
0500
Validity: the 15th
between 06 and
15 TU
Wind 360°
03kt
Visibility: 500m
FZFG
Cloud layout
200ft
Weather:
freezing fog
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4.2.3. METAR / SPECI
Below is a METAR typical of CAT III conditions:
LFBO
191050Z
Airport
identification
01002KT
0200
Wind: 010°,
02kt
Day of
issue 19 at
10h50 z
FZFG
R14R0250D
OVC001
Weather:
RVR RWY
Freezing fog 14R = 250m
downgrading
Visibility
200m
M02/M02
Q1025
AOT= –2°C
Dew point=
–2°C
Cloud
layout: 100ft
QNH
Other information on reported RVR in METAR (cf. ICAO Annex 3):
– the RVR reported in a METAR is a value averaged over a period of 10 minutes,
– only the representative value of the touchdown zone is reported in METAR,
– in METAR, the runway visual range should be based on the maximum light intensity available on the runway,
– whenever RVR changes and passes through 150, 350, 600 or 800m a report of special observations (SPECI) is
issued.
R16L/0350
R for RVR
Runway 16 Left (C: center R right)
RVR 350 meters
R16C/M0050
M means RVR is below the minimum value that can be determined by the system in use
(i.e 50m)
R14L/P2000
P means RVR is above the maximum value that can be determined by the system in use
(i.e.2000m)
R20/0400V0800
V means that during the averaging period of 10 minutes RVR has varied between 400m
and 800m
R12/0550N
R20/800D
“U” or “D” are used when during the averaging period of 10 minutes the variation of the
RVR shows an Upward or Downward tendency. The abbreviation “N” indicates there is no
distinct tendency
Table B1: Description of the RVR in METAR
In a METAR, the present weather phenomena (i.e. FG or SN) may be associated with the following information:
MIFG
Shallow – less than 2m above ground level.
BCFG
Patches – fog patches randomly covering the aerodrome.
PRFG
Partial – a substantial part of the aerodrome covered by fog while the remainder is clear.
DRSN
Low drifting – snow raised by the wind to less than 2 m above ground level.
BLSN
Blowing – snow raised by the wind to a height of 2 m or more above the ground.
VCFG
Vicinity – Fog reported between approximately 8 and 16 km of the aerodrome reference point.
The OAT / dew point is an interesting indicator: fog usually forms when the dew point and the air temperature are within
a few degrees of each other, with the air temperature being lowered to the dew point, or when the dew point being
increased to the air temperature causes fog formation. Contrarily, fog would be lifting when the temperature-dew point
spread begins increasing.
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C. Aircraft
requirements
C - Aircraft requirements
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1. Aircraft certification status
1.1. General
The basic rule for an aeroplane is to be operated under a current certificate of airworthiness and to be maintained in a
serviceable condition, in accordance with an approved maintenance program.
Instruments and equipment for Category II and Category III operations have to comply with specific airworthiness requirements. It is assumed that the aircraft has a basic airworthiness approval for IFR operations.
The supplementary airworthiness requirements for CAT II operations are described in appendix 3 of AC 120-29A (FAA
regulation) and in subpart 2 of CS-AWO (European regulation).
For CAT IIIA operations the relevant regulations are Appendix 3 of AC 120-28D (FAA) and subpart 3 of CS AWO (European regulation).
To perform lower than Standard CAT I approaches under European regulation, the aeroplane has to be certificated in
accordance with CS-AWO to conduct Category II operations and the auto-land system shall be approved for Category
IIIA operations.
For other than Standard Category II operations under European regulation, the aircraft has to be certificated in accordance with CS-AWO for operations with a decision height below 200ft.
The certification process is to demonstrate that a high safety level and an acceptable rate of missed approaches are
achieved during low visibility approaches. Such demonstration can be done examining:
– airborne system accuracy,
– airborne system availability and integrity,
– reliability of the airborne equipment,
– degree of redundancy,
– probability of airborne system failure and consequences.
The safety level must not be less than the average safety level achieved in Category I precision approaches. The rate of
approaches terminating in a go-around below 500ft, due to the approach and landing system performance or reliability,
may not be greater than 5%.
1.2. Guidance and landing systems
Aircraft equipped with head up guidance landing system (HUDLS) or enhanced/synthetic vision systems or hybrid system (e.g.; autoland system in combination with head up display system) can be certificated to perform CAT II, CAT IIIA,
lower than Standard CAT I and other than Standard CAT II approaches. As ATR aircraft are not equipped with HUDLS
the following paragraphs do not deal with those systems.
1.2.1. CAT II approaches
An aircraft cannot be approved to perform CAT II approaches without being fitted with an approach guidance system,
composed of the following equipment and functions:
– two ILS and/or two MLS receivers,
– an automatic approach coupler with an audible warning of automatic pilot failure or a flight director system,
– one radio altimeter with display at each pilot’s station of radio altitude and the selected decision height,
– an indication, at each pilot’s station, of when the aeroplane reaches the pre-selected decision height appropriate to the approach (e.g. an alert light),
– an automatic or flight director go-around system,
– an appropriate equipment failure warning system,
– an alert, at each pilot’s station, on excess deviation from the required approach path.
NOTE: FAA regulation authorises flight director CAT II approaches. For EU operational regulation, only auto-coupled CAT II approaches are
considered.
Classic instruments ATR aircraft are certificated for CAT II approaches providing MOD (1112) is applied. MOD (0069)
allows the use of the auto-pilot down to 50ft (MOD 0069 is not available for ATR 42-500).
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C. Aircraft requirements
AIRCRAFT
MOD
NAME
SB
42-300
72
0069
AUTOFLIGHT – AFCS: USE A CAT II APPROVED AP/FD DOWN TO 50 FT
42-22-0017
72-22-1006
All
1112
AUTOFLIGHT – RETROFIT CAT II CAPABILITY TO A/C DELIVERED WITH
CAT I CAPABILITY
42-22-0001
72-22-1007
Basically, ATR -600s are CAT II certified.
1.2.2. CAT IIIA approaches with DH ≥50ft
An aircraft approved to perform automatic CAT IIIA approaches (with DH ≥ 50ft) is basically fitted with an automatic
approach and landing system including the equipment and functions listed above for CAT II approaches plus:
– an automatic voice system, which calls when the aeroplane is approaching the decision height and when it
reaches the decision height,
– a fail-passive or fail-operational automatic landing system,
– an acceptable speed control device or an automatic throttle control.
An automatic landing system is fail-passive if, in the event of a failure, there is no significant out-of-trim condition or deviation of flight path or attitude but the landing is not completed automatically. For a fail-passive
automatic landing system the pilot assumes control of the aircraft after a failure (cf. CS-AWO 300 Applicability
and Terminology (b)(3)). Fail-passive landing system can support CAT IIIA approaches with DH ≥ 50ft, but cannot
support CAT IIIB approaches nor CAT IIIA approaches with DH<50ft.
An automatic landing system is fail-operational if, in the event of a failure below a specified height, the approach,
the flare and landing can be completed by the remaining part of the automatic system. In the event of failure, the
automatic landing system will operate as a fail-passive system (cf. CS-AWO 300 Applicability and Terminology (b)(4)).
Fail operational landing system are requested for CAT IIIB approaches and CAT IIIA approaches with DH<50ft.
Out of the ATR family of aircraft only the ATR -600 is equipped with a fail-passive automatic landing system and a speed
control system. Only the ATR -600 can be certificated for CAT IIIA approaches with DH ≥50ft.
ATR aircraft are not equipped with fail-operational landing systems nor automatic throttle controls, nor automatic
ground roll controls, hence they cannot be certificated for CAT III approaches with DH<50ft.
1.2.3. Lower than Standard CAT I and other than Standard CAT II
One of the conditions for an aircraft without HUDLS to be authorised for such operations is to perform an automatic
landing. Only aircraft certificated to conduct Category II approaches and equipped with an auto-land system can perform lower than Standard CAT I or other than Standard CAT II.
Since ATR -600s are equipped with an automatic landing system they can support lower than Standard CAT I and other
than Standard CAT II operations.
1.2.4. Low visibility take-off
As long as take-off is performed using only external visual references, even in low visibility conditions, there is no need
to satisfy additional certification requirements. The operational regulation, which may vary from one State to another,
sets the minimum RVR conditions in which the pilot may be expected to have available the external visual references
required for the control of the aeroplane until it is airborne, or until the end of an abandoned take-off (e.g. 125m RVR
for European regulation).
This RVR limit may be lowered if the aircraft is equipped with a guidance system which provides directional guidance
information to the pilot during the take-off or abandoned take-off (e.g. HUD). This guidance information normally takes
the form of command information, but it may alternatively be a situation (or deviation) information. In the event of loss of
visibility during the take-off or abandoned take-off, the system enables the pilot to control the aeroplane on the runway
centreline using the normal steering controls.
With the operational benefits provided by such devices being limited (e.g. RVR limit reduced from 125m to 75m), ATR
aircraft are not equipped with such a guidance system for take-off, hence they are not required to be subjected to additional certification process.
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1.3. System performances
During the certification process, a level of performance, integrity and availability must be demonstrated by a combination
of simulator tests, statistical analysis and flight tests. The test conditions must be representative of operative conditions
and they must cover the range of parameters affecting the behaviour of the aeroplane (e.g. wind speed, ILS ground facility
characteristics, aerodrome elevation and temperature, ground profile, aeroplane configuration, weight, CG…).
In addition, an analysis of failure conditions and their effects has to be carried out, including not only failures of the guidance and landing system but also failures of other aeroplane equipment.
The aim of this guide is not to describe in details the airworthiness requirements which vary according to the type of
operations and to the regulation applied.
Nevertheless it is to be noted that, in CAT II certification, particular attention is given to the ILS tracking performances.
The probability that the maximum ILS deviation does not exceed the excess deviation alerts has to be demonstrated
as being satisfied.
In CAT III, the autoland system performances have to be evaluated. Notably it must be shown that the touchdown
performance is such that any of the following events is improbable:
– longitudinal touchdown earlier than a 60 m from the threshold point on the runway,
– longitudinal touchdown beyond the end of the touchdown zone lighting (900 m from threshold),
– lateral touchdown with the outboard landing gear more than 21 m (70 ft) from runway centreline (this value
assumes a 45 m (150 ft) runway),
– sink rate for structural limit load,
– bank angle resulting in hazard to the aeroplane and
– lateral velocity or slip angle for structural limit load.
1.4. Aircraft Flight Manual content
The certification process for Low Visibility Operation leads to specific statements in the Aircraft Flight Manual covering
the following items:
– Limitations, take-off and approach capacity, including the minimum decision height to which the aeroplane is
certificated;
– Permitted configurations (e.g. flap setting, number of operating engines);
– Normal and abnormal procedures;
– Changes to the performance information, if necessary (e.g. approach speed, landing distance required, goaround climb);
– Minimum required equipment and effect of failures on aircraft capacity;
– The height losses for go-around initiation heights below 30m (100ft).
– The maximum head, tail and cross wind components in which the performance of the aeroplane has been
demonstrated.
NOTE: Actual RVR minima to be used are subject to operational regulation and may vary from one state to another taking account of local
circumstances. For this reason, RVR minima should not be included in the Aeroplane Flight Manual as Limitations.
With the ATR family, limitations depend on type (42 or 72), on series and modifications applied.
Example:
Limitation for ATR 72-500 (please refer to AFM 7.01.03, CAT II operation):
Minimum height for use of autopilot in approach mode: 80ft (50ft for MOD 0069)
Minimum decision height: 100ft
Certified configuration: flaps 30
Maximum demonstrated wind: Headwind: 30kts, tailwind: 10kts, crosswind: 15kts
2. ATR automatic flight control system
2.1. AFCS on classic instruments ATR
The Automatic Flight Control System is made up of the following components:
– one computer
– one advisory control panel
– one control panel
– three servo-actuator (one for each axis)
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C. Aircraft requirements
ADVISORIES
SELECT LT
MESSAGES
ARMED MODE
CAPTURED MODE
ADU
AFCS
CONTROL
PANEL
AFCS
COMPUTER
QUICK
DISC/ TCS
QUICK DISC/ TCS
Figure C1: Classic ATR AFCS description
The computer receives data from several sensors and generates commands to the flight control actuators and to the
FD bars.
Dual microprocessor architecture and digital servo-monitoring techniques are used to provide an adequate safety level.
In ILS approach mode, LOC and GS are displayed both on ADU and on EADI:
– In white during the arm phase LOC
– In green with a star during the capture phase LOC*
– In green without star when in track phase LOC . Track phase, for both LOC and G/S, can only take place below
1500ft RA, but must be achieved before 800ft RA.
Category II capability
As soon as APP mode is armed, the approach capability (as seen by the AFCS computer), will be displayed on the first
line of the ADU (CAT 1 or CAT 2)
CAT2 message means that CAT II conditions are met; it replaces the CAT1 message on ADU as and when all the following requirements are satisfied:
– Pilot and copilot AHRS valid
– Pilot and copilot EFIS valid
– Pilot or copilot DADC valid
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– Radio altitude 1 or radio altitude 2 valid
– Pilot and copilot displaying an ILS source
– Radio altitude greater than 800 feet AGL
– Comparison monitor annunciator is non-active.
Figure C2: CAT 2 display on ADU
The CAT2 message remains displayed for the duration of the approach if all the above stated conditions remain satisfied. If any of those requirements for the CAT2 message are lost, a CAT2 INVALID message flashes on the ADU. In
addition a triple click aural warning is generated.
Excess Deviation monitoring utilizes ILS data from both SGU and is enabled when CAT II conditions are met.
Dual coupling
During ILS approach, DUAL coupling automatically occurs after LOC and GS track phase has begun, if only if both NAV
receivers are tuned to ILS. In dual CPL both arrows are illuminated and both NAV receivers are coupled to the AFCS
computer which utilizes average data for guidance computation.
Dual coupling requires that all of the following conditions are met.
– The EHSIs are displaying different ILS navigation sources tuned to the same frequency
– Both the localizer and glideslope are in track mode
– Radio altitude is below 1200 feet AGL
– Both navigation receivers are operative.
Figure C3: CPL on AFCS control panel
2.2. AFCS on ATR -600
For later revision.
3. Aircraft minimum equipment required
The equipment which must be serviceable at the beginning of the approach is established during the certification process and included in the AFM.
This list should be used to amend the airline Minimum Equipment List (MEL). The dispatch conditions for relevant equipment should clearly indicate that CAT II or CAT III operations are not authorised.
This list should also be included in the airline operating manual and/or QRH to be used by the crew mainly in case of in
flight failure. Before commencing a low visibility approach the crew has to check that all relevant equipment is operative.
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C. Aircraft requirements
3.1. Classic instruments ATR
Below is the minimum equipment required on ATR 72-500 to meet CAT II approach criteria (please refer to AFM 7.01.03,
CAT II operation).
Equipment required:
Autopilot
FD bars
AP quick disconnect
AP OFF warning (light and aural)
1
1 (PF side)
1 (PF side)
1
ADU
ILS receiver
AHRS
Standby Horizon
CRT
SGU
Radio altimeter
DH indicator
GA pushbutton
Windshield wipers
Yaw damper
Airspeed indicators
1
2
2
1
3 (2 PF side)
2
1 (with 2 displays)
2
1 (PF side)
1 (PF side)
1
2
CM2 side must be operative(1)
CM1 side must be operative, if CM1 is PF
3
Blue + Green
DC: BUS 1 / BUS 2 / EMER / STBY / ESS
AC: BUS 1 / BUS 2 / STBY
ACW: BUS 1 / BUS 2
3
Altimeter
Hydraulic system
Electrical system
MFC modules
(1)
The standby airspeed instrument can be easily monitored only from the Captain position.
In addition to this list it is worth noting that in case of engine failure on ATR, although the autopilot can be engaged
during approach, CAT II approaches are not authorised.
3.2. ATR -600
For later revision.
4. Aeroplane malfunctions
During the CAT II/III certification process, the analysis of failure conditions and their effects will determine the actions
to be taken by the flight crew in case of failure of any system, instrument, or element during a low visibility approach.
The nature of the failure and the point of its occurrence determine which response is appropriate. In general there are
three possible responses to a failure:
– CONTINUE the approach to the planned minima,
– REVERT to higher minima and proceed to a new DH,
– GO AROUND and reassess the capability.
The appropriate actions to be taken in case of failure are provided by the Aircraft Flight Manual. The procedures following failure, established by the operator and published in his Operating Manual, should not be less restrictive than
those of the AFM.
Here below are listed the failures and associated actions during a CAT II Approach for an ATR aircraft.
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4.1. ATR 72-500
AFCS and ADU
Flight intruments
A/C systems
Warnings
Actions at the time of failure detection
> 800 ft AGL
Flap failure, jammed
between 0 and 15 position
Revert to CAT I minima
Flap failure, jammed above
15 position
Continue
Increase VAPP (flaps 30)
by 10 kt
Engine failure
Revert to CAT I minima
Hydraulic failure
(without fluid loss)
Transfer
No capability loss
First MFC module failure
Apply associated procedure
continue the approach
Second MFC module failure
Apply associated procedure
Revert to CAT I minima
Standby horizon flag
Revert to CAT I minima
Radio altimeter warning on
PNF EFIS
Revert to CAT I minima
ATT/PIT/ROLL warning on
any EFIS
Switch to valid AHRS
Reengage AP
Revert to CAT I minima
HDG warning on any EFIS
Switch to valid AHRS Revert
to CAT I minima
< 800 ft AGL
< 500 ft AGL
Not applicable
First action before
switching AHRS
is to refer to
standby horizon
to determine the
wrong AHRS
Discontinue the approach
Revert to CAT I minima
Loss of one CRT
Switch affected CRT OFF
Loss of both CRT on one
side
Switch to valid SGU.
Revert to CAT I minima
Loss of CM2 airspeed
indicator and CM1 side
if PF
Revert to CAT I minima
Loss of any altimeter
Revert to CAT I minima
AP disengage
Try to recover
If impossible revert to CAT I
FD approach
Discontinue the approach
Not applicable
Discontinue
the approach
Loss of ADU
Perform a CAT I minima
manual approach
Loss of CAT II capability
(Triple click)
Try to recover
If impossible revert to CAT I
minima
Multiply landing
distance flaps 30
by 1.13
Discontinue the approach
LOC / GS / ILS / warning
on any EFIS
LOC or G/S excess
deviation
Complementary
actions
Discontinue the approach
Table C1: Failures & associated actions during a CAT II approach.
4.2. ATR -600
For later revision.
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C. Aircraft requirements
5. Maintenance
Operational regulations request that on board guidance systems and equipment used for Low Visibility Operations be
maintained in accordance with a maintenance program established by the operator in liaison with the aircraft manufacturer, and approved by the authority.
On all ATR aircraft, equipment used for Low Visibility Operations is part of the basic design standard. Therefore, related
tasks are covered by the ATR Maintenance Program. There is no special recommendation for scheduled maintenance
tasks or functional checks to maintain CAT II / CAT III capabilities.
In case of failure affecting the aircraft CAT II or CAT III capability, the aircraft status is primarily governed by status messages issued from a Multi Purpose Computer. However, crew entry in the Technical Log Book must take precedence.
A log entry must be made each time the CAT II or CAT III capacity is not available.
Concerning the auto-land capability on ATR 42-600 / 72-600 a program for unscheduled maintenance is established to
advise on all necessary corrective actions / procedures following an automatic landing failure and/or component failure.
A reliability programme is also established to monitor the system operational status.
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D. Airfield
requirements
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D. Airfield requirements
1. Aerodrome approval
Operations with limited visual references at an aerodrome will need additional facilities, services and procedures to
those required for good weather operations.
It is the responsibility of the airport national Authority to verify that ground facilities and services meet ICAO specifications, before promulgating a runway as available for Category II or III operations.
An operator shall not use an aerodrome for CAT II or CAT III operations unless it is approved for such operations by the
State in which the aerodrome is located.
The relevant ICAO documents for the approval of an aerodrome for Low Visibility Operations are:
– Annex 14 – aerodrome design and operations
– Annex 10 - ILS
– Doc 9365 – Manual of All Weather Operations
There are national differences in methods for licensing aerodromes. Some States may promulgate specific national
requirements but they should not be less restrictive than CAT II and CATIII ICAO standards.
The additional criteria to satisfy before opening an aerodrome to all-weather operations concern mainly the following
items:
– adequacy of runways and taxiways,
– visual and non-visual aids,
– control of obstacles,
– assessment of RVR,
– air traffic service, including surface movement control.
The demonstration of compliance with ICAO standards is a long and complex process, with a large number of directives to satisfy. This section sums up the ICAO specifications for CAT II/III airports.
2. Runway and taxiway characteristics
2.1. Runway length
There is no specific requirement concerning runway length for an aerodrome to be CAT II or III approved. The runway
length should be adequate to meet the operational requirements of the aeroplanes for which the runway is intended.
2.2. Runway width
The runway width should normally be not less than 45m.
2.3. Runway slope
In order to permit the use of the automatic landing system, disregarding normal standards, it is recommended that for
the first and the last quarter of the length of the runway the longitudinal slope does not exceed 0.8%.
2.4. Runway-holding position
The location of a runway-holding position is such that a holding aircraft or a vehicle does not infringe the obstacle
free zone, approach surface, take-off climb surface or ILS critical/sensitive area nor interferes with radio aids. Without
distinction of approach categories, ICAO recommends that the distance between the runway-holding position and the
runway centreline should not be less than 90m (or 107.5m for a 60m width runway). Nevertheless, for many airports,
CAT II and CAT III holding positions are located at a minimum distance of 150m from the runway centreline.
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3. Effects of pre-threshold terrain profile
The topography of an approach terrain is important in all weather operations. A regular and preferably leveled prethreshold area ensures correct radio altimeter functioning. The operation of automatic landing systems is dependent,
among other things, on the radio altimeter. The flare profile, the rate of descent at touchdown, and the distance of the
touchdown point from the runway threshold can, therefore, be affected by the profile of the terrain immediately preceding the threshold. The terrain which is most critical lies in a 60 m area on either side of the runway centreline and
extends before the threshold, to the distance of at least 300 m into the approach area. Within this area, ICAO recommends that slope changes be avoided or, when it is not possible, that the rate of change between two consecutive
slopes should not exceed 2% per 30m.
On some airfields where underlying terrain is irregular, radar reflectors are used to stabilise the radio altimeter signals in
the area preceding the runway threshold.
Regardless of the effect on the AFCS during the landing phase, an irregular terrain profile up to 1000 m out from the
threshold may have an influence on the determination of a CAT II decision height. It may also affect the approach management. This is particularly so where the terrain under approach is markedly lower than the threshold. Then the time
available for the head down to head up transition, and for the visual cues acquisition, may be significantly shortened.
“Hundred above”
“Hundred above”
“Decision”
“Decision”
200ft RA
DH=110 ft 210 ft RA
DH=100ft
available time for decision making
shortened time for decision making
Figure D1: Effect of terrain profile on time available for decision making
4. Obstacles clearances requirements
Obstacle clearance is a primary safety consideration in the development of instrument flight procedures. The criteria
and methods used aim to avoid any aircraft at take-off, on approach, landing or go-around touching obstacles on the
ground.
For each runway a series of Obstacle Limitation Surfaces (OLS) define the limits to which objects may project into
the airspace. Those surfaces, established in accordance with ICAO Annex 14 Chapter 4, Obstacle restriction and removal, identify the lower limits of the aerodrome airspace above which objects become obstacles.
Transitional
Conical
Inner horizontal
Outer horizontal
Figure D2: Obstacle Limitation Surfaces (OLS)
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Inner
approach
surface
Inner transitional surface - slope 33.3%
Runway
Threshold
18 m
60 m
900 m
Slope 33.3%
m
Slope=2%
H= 45 m
12
0
D. Airfield requirements
For precision approach, surfaces closer to the runway (i.e. inner approach, inner transitional and balked landing surface)
define a volume of airspace in the immediate vicinity of the runway known as the Obstacle Free Zone (OFZ). This
zone must be kept free from any fixed obstacle other than a low-mass and frangibly mounted equipments required for
air navigation purposes.
Balked
landing
surface
Divergence 10%
1,800m
or runway length L if L<1,800m
Figure D3: Obstacle Free Zone (OFZ)
In addition to the OFZ constraints, for each approach type an Obstacle Clearance Height (OCH) is calculated. For
an aircraft on the approach track, the OCA/H ensures clearance of obstacles from the start of the final approach to the
end of the intermediate missed approach segment. The OCH of a precision approach is defined as the lowest height
at which a missed approach must be initiated to ensure compliance with the appropriate obstacle clearance design
criteria. The OCH is referenced to the elevation of the relevant runway threshold and it is used to establish the approach
operating minima (please refer to Paragraph G.1, Establishing operating minima).
The ICAO Doc 8168 (PANS OPS) Volume II Part II Section 1 chapter 1, Instrument Landing System (ILS), presents different methods for the OCH calculation.
Q
Among
those methods, two of them involve a set of surfaces (basic ILS surfaces or Obstacle Assessment
Surfaces (OAS)). The OCH is determined by accounting for all obstacles which penetrate those surfaces. OAS
are established taking into account, amongst others, the glide path angle, the miss approach climb gradient, the
localizer-threshold distance, the category of the approach, the use or not of autopilots certified for CAT II operation.
Q
Another
method uses a Collision Risk Model (CRM). This method is employed mainly when the obstacle
density below OAS is considered to be excessive. The CRM is a computer program that takes into account all
obstacles located in the vicinity of the runway. It determines the minimum OCH which provides a safety target
of 10–7 (1 in 10 million) per approach for risk of collision with obstacles.
Z
Y
Glid
X
e pa
th
W
E
l
Fina
oach
appr
se
cour
C
D
La
nd
ing
th
re
sh
old
Figure D4: ILS Obstacle Assessment Surfaces (OAS)
OCH is established for all Category I and Category II precision approaches and for each aircraft category (A,B,C,D). An
OCH is not associated with CAT III operations. These are supported by overlapping protection from the CAT II criteria.
Category III operations are possible only if the CAT II OCH is equal or less than 100ft.
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5. Navaids - Characteristics and limitations
5.1. General
The precision instrument approach systems intended to support CAT II and CAT III operations are:
– Instrument Landing System (ILS)
– Microwave Landing System (MLS)
– GNSS Landing System (GLS)
The ILS has been the mainstay of landing system aids for well over 50 years. Although ILS has some limitation, for the
time being it is the only system to support CAT II and CAT III operations on a world scale.
The MLS has a number of operational advantages, including a wide selection of channels, an ability to allow curved
approaches, a lesser sensibility to interference, an excellent performance in all weather, and a small “footprint” at the
airports. Although some MLS systems became operational in the 1990s, airline reluctance to invest in MLS and the rise
of GLS has jeopardised a widespread deployment.
GLS (LAAS) is a landing systems based upon the Global Navigation Satellite System (GNSS Landing System). For
Low Visibility Operations the landing system typically includes a Local Area differential Augmentation System (LAAS)
located in the vicinity of the runway. The local area system uses differential techniques to correct and improve the accuracy of GPS, it may serve one or more runways, or nearby airports. GLS (LAAS) promises to provide CAT II and CAT
III capability and is already included into FAA regulation. Nevertheless LAAS is currently a research and development
project focusing on the resolution of integrity and safety issues: no approaches have been certified to date (Sept. 2009).
It is worth noting that Wide Area Augmentation Systems (e.g., WAAS, EGNOS) are typically considered to be RNAV
systems, and are not alone considered to be GLS able to support CAT II/III operations.
For the time being ATR aircraft are not equipped with MLS or GLS; consequently only ILS is developed in this brochure.
5.2. ILS characteristics
An ILS consists of three independent sub-systems:
– the localizer providing lateral guidance. A Localizer antenna array is located beyond the departure end of the
runway and consists of several pairs of directional antennas,
– the glideslope, providing vertical guidance. A Glidepath (GP) antenna array is sited to one side of the runway
touchdown zone,
– marker beacons or DME providing information on the distance from the runway threshold. In modern ILS installations a DME, co-located usually with the Glideslope, augments or replaces marker beacons.
Localizer and Glideslope signals are transmitted on different carrier frequencies but the technical principles are similar:
For each system, two signals are transmitted: one is modulated at 90 Hz, the other at 150 Hz. The on board localizer
and glideslope receivers measure the Difference in the Depth of Modulation (DDM) of the 90 Hz and 150 Hz signals The
difference between the two signals varies depending on the position of the approaching aircraft from the centreline for
the localizer and from the desired slope (approximately 3°) for the glideslope. If there is a predominance of either 90 Hz
or 150 Hz modulation, the aircraft is off ILS axes. If the DDMs are zero, then the aircraft is on axes.
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LOC Aerial
D. Airfield requirements
90 Hz
Localizer
150 Hz
90 Hz
Glideslope
GS Aerial
150 Hz
50 ft
~1,000 ft
Figure D5: Localizer and glideslope signals emission patterns.
To achieve a high degree of integrity, monitors continually assess the vital characteristics of the transmissions. If any
significant deviation beyond strict limits is detected, either the transmitters are automatically switched or the ILS is
turned off.
Figure D6: Glideslope antenna
Figure D7: Localizer antenna array
5.3. ILS performances
The ILS installation must conform to technical specifications contained in ICAO Annex 10, Volume 1. Ground and flight
check are performed at regular intervals to detect any degradation in ILS performances.
The aim of this brochure is not to describe in detail complex technical standards; nevertheless some figures give an
idea of ILS performances:
Localizer
At threshold a half dot-deviation on the ILS indicator means the plane is off course by 27m.
At threshold the course alignment accuracy requested is:
– for CAT II ILS: 7.5 meters (4.5m recommended) – alarm threshold: 7.5m
– for CAT III ILS: 3 meters- alarm threshold: 6m
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Glideslope
The beam width is 1.4° (0.7° for full scale deflection).
At threshold a one dot-deviation equals about a 7-foot excursion from the prescribed glidepath, 14ft at 100ft.
Monitoring system
For CAT II and CAT III ILS, the monitoring system is such that the period of radiation outside the performance limits
never exceeds 2 seconds (recommended 1 second).
5.4. ILS classification
ILS are classified according to their performances by using three characters as follows:
Q
I,
II, III: Performance category:
– I: ILS performances sufficient to provide guidance down to 200ft
– II: ILS performances sufficient to provide guidance down to 50ft
– III: ILS performances sufficient to provide guidance down to and along the surface of the runway.
Performances concern several parameters such as coverage, carrier modulation characteristics, course accuracy,
alarm threshold…
Q
A,B,C,T,D
or E: This character defines the point to which the localizer course structure comply with the ICAO
annex 10 technical standard. The position of these points is given on the figure here below
Q
1,2,3,4: this number indicates the level of integrity and continuity of service as defined by ICAO annex 10:
Level 3 is a required objective for equipment supporting CAT II and CAT IIIA operation
Level 4 basically relates to the needs of the full range of CAT III operations.
C
A
B
Stop end of runway
T
Threshold
E
D
30ft
600m
900m
1050m
7.5km (4 Nm)
Figure D8: ILS points
ILS Class vs. approach category
– An ILS intended to support CAT II approaches would be described at least as a class II/T/3.
– An ILS intended to support CAT III approaches would be typically described as a class III/E/4.
– An ILS intended to support lower than Standard Category I operation must be certificated to:
Class I/T/1 for operation to a minimum RVR of 450m RVR; or
Class II/D/2 for operations to less than 450m RVR.
Single ILS facilities are only acceptable if Level 2 performance is provided.
– An ILS intended to support other than Standard Category II operation must be certificated to class II/D/2 for
operations in less than 450m RVR or to a DH of less than 200ft.
D - Airfield requirements
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D. Airfield requirements
5.5. ILS protection
ILS localizer and glideslope systems have some limitations. Localizer systems are sensitive to obstructions in the signal
broadcast area. Glideslope systems are also limited by the terrain in front of the glideslope antennas. If terrain is sloping
or uneven, reflections can create an uneven glidepath causing unwanted bar deflections.
The areas within which movable objet may degrade the guidance signal must be defined and recognised.
ICAO considers two kinds of protection areas:
Q
The
ILS critical areas are areas of defined dimensions about the localizer and glide path antennas. All vehicles
and aircraft must remain outside these areas during all ILS operations. Critical areas are fenced and secured to
prevent them from unauthorised access.
Q
The
ILS sensitive areas are much wider. Their size depends on a number of factors including the type of ILS
antenna, the topography, the ILS category and the size of aircraft operating on the airport. They have to be entered
and exited during normal operation but, during low visibility procedures, clearance from ATC is required before
entering sensitive areas. Their limits are marked on the taxiway by yellow lines, red stop bars and CAT II/III signs.
Designation of critical and sensitive areas is the airport authority responsibility. ATC control access to sensitive areas
when low visibility procedures are in force (please refer to Paragraph D.7, ATC procedures). With the same aim of protecting the ILS beam, ATC usually increase separation between aircraft on landing or take-off.
300m or end of runway
Localizer sensitive area
Localizer
critical area
Runway
120m
Localizer antenna
Figure D9: Typical localizer critical and sensitive areas
Runway
threshold
Glideslope
antenna
250m
Glideslope
critical area
30m
Glideslope
sensitive area
Taxiway
Figure D10: Typical glideslope critical and sensitive areas
6. Characteristics of the visual aids
The runway marking and lighting standards are detailed in ICAO Annex 14 Chapter 5, Visual aids for navigation.
6.1. Runway markings
There is a no specific CAT II or CAT III requirement concerning runway markings except for the runway centreline
that must have a width not less than 0.9m. The touchdown zone markings are mandatory for all runways supporting
precision approaches, but CAT II/III runways usually have a distance coding.
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CAT II and CAT III specific holding positions are normally located upstream of the standard holding position to avoid
aircraft entering into the obstacle free zone or the ILS sensitive area. The markings used are also specific. They are associated with CAT II or CAT III signs placed on either edge of the taxiway. The sign CAT III must be accompanied with
flashing lights.
Runway
Figure D10: CAT II /III holding position signs
2.1m
Taxiway
3m
Figure D11: CAT II /III holding position markings
Figure D13: Taxiway markings for CAT II / III operations
Figure D13: Touchdown zone markings for runway with a length of 2400m or more
6.2. CAT II/III Lighting systems
Runway and approach lights on runways intended to support CAT II or CAT III operations consist of high intensity lights.
The main characteristics of a lighting system meeting the ICAO Annex 14 standard for CAT II/III operations are explained in the following paragraph.
D - Airfield requirements
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D. Airfield requirements
6.2.1 Taxiway lights
Taxiway lights Colours
Spacing
Special features
Centre line
green
15m on a straight section
7.5m on curves
Requested for operations with RVR <350m
Edge lights
blue
60m on a straight section
<60m on curves
Not requested for taxiways with centre line lights
Table D1: Taxiway lights
6.2.2. Stop bars
Stop bars consists of red lights spaced at interval of 3m across the taxiway. In conditions with less than 350m RVR a
stop bar shall be provided at every runway-holding position, except where appropriate aids and/or procedures (e.g.
surface movement radar) are available to prevent inadvertent runway incursions. Stop bars are controlled by Air Traffic
Services; the switching is made in conjunction with at least 3 taxiway centre line lights.
Figure D14: Stop bars
Figure D15: Stop bar closed
Figure D16: Stop bar opened
6.2.3. Runway guard lights
Runway guard lights consist of two pairs of flashing yellow lights located at each side of the taxiway. Runway guard lights are provided at
each taxiway / Runway intersection where a stop bar is not installed.
Guard lights:
pair of flashing
yellow lights
Figure D17: Guard lights
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6.2.4. Runway lights
Runway lights
Colours
Spacing
Special features
Threshold
Green – unidirectional
3m
Runway end
Red – unidirectional
6m
At least 6 lights
Edge
– Variable white
– may be yellow from 600m
to the runway end (limited to
1/3 of the runway)
60m
May be omitted at the
intersection
Centre line
– variable white
– alternate red and white
from 900m (or runway mid
point if RWY length <1800m)
to 300m from the runway
end
– red from 300m to the
runway end
15m – may be reduced to
7.5m
Touchdown zone
Barrette of variable white
– unidirectional
– barrettes – longitudinal
spacing : 60 or 30m
– barrettes – lateral spacing:
18 to 22.5m
– A barrette is composed of
at least 3 lights. Its length is
between 3 and 4.5m
– TDZ extends from threshold
to 900m from threshold (or
to runway mid point if RWY
length <1800m)
Table D2: Runway lights
6.2.5. The approach lighting system
The approach lighting system consists of a row of lights on the extended centreline of the runway, extending, wherever
possible, over a distance of 900m from the threshold.
In addition, the system has two side rows of red lights, extending 270m from the threshold, and crossbars located at
150m, 300m, 450m, 600m and 750m from the threshold.
Such approach lighting intends to support all low visibility approaches. Depending on the operational regulations, reduced
lengths may be acceptable for CAT II or CAT III operations (please refer to Paragraph E.8, Effect of failure of ground equipments). For CAT I approaches a reduced approach lighting system causes an increase in operating minima.
Approach lights
Colours
Spacing
Special features
Extended centre
line for the first
300m from the
threshold
Barrettes of variable white
30m
Minimum barrette length: 4m.
Maximum spacing between
barrettes’ lights: 1.5m
Extended centre
line beyond
300m from the
threshold
Variable white
30m
Consists of either:
– barrettes, as used on the
inner 300m
– 2 lights in the central 300m
and 3 lights in the outer
300m
Side row
red
– barrettes - longitudinal
spacing : 30m
– barrettes – lateral spacing:
equal to that of the TDZ
Length of barrettes and
spacing of its lights equal to
those of the TDZ
Crossbar located
at 150m from
threshold
Variable white
Lights’ lateral spacing: ≤2.7m Fills the gap between the
centre line and the side row
barrettes
Crossbar located
at 300m from
threshold
Variable white
Lights’ lateral spacing: ≤2.7m Extends to 15m on both side
of the center line
Table D3: Approach lights
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D. Airfield requirements
Figure D18: CAT II/III approach light system
D - Airfield requirements
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Figure D19: Approach lights description
Figure D20: Approach lights during a night landing
6.2.6. Lighting system condition
For a runway meant for use in low visibility conditions, the electrical systems for the power supply, lighting and control of
the lighting are designed so that an equipment failure will not leave the pilot with inadequate visual guidance or misleading information. To achieve the required level of availability a secondary power supply must be able to switch over within
one second (time extended to 15s for taxiway lights, edge lights and approach lights beyond 300m from the threshold).
The maintenance services must ensure that, during any period of Category II or III operations, all approach and runway
lights are serviceable, and that in any event at least 95% of the lights are serviceable except for runway end lights (75%),
approach lights beyond 450m (85%) and TDZ lights (90%). In addition two adjacent lights should not remain unserviceable except for lights in a barrette or a crossbar.
6.3. Lighting systems for Lower than Standard CAT I and
other than Standard CAT II approaches
Lower than Standard CAT I and other than Standard CAT II approaches can be conducted on a runway where some or
all of the elements of the ICAO Annex 14 Precision Approach Category II lighting systems are not available.
For those approaches the lighting system must include at least the runway lighting (runway edge lights, threshold lights,
runway end lights).
As for CAT I operations, the length, the configuration and the intensity of the approach lighting has a direct impact on
the minimum value of the RVR requested to perform such approaches (Please refer to Paragraph G.1, Establishing operating minima). In order to easily associate an RVR to a particular approach lighting system the European regulation has
classified approach lighting into four main categories:
Q
FALS
(full approach light system):
ICAO: Precision approach CAT I Lighting System (HIALS 720 m ≥) distance coded centreline, Barrette centreline.
Q
IALS
(intermediate approach light system):
ICAO: Simple approach lighting system (HIALS 420-719 m) single source, barrette.
Q
BALS
(basic approach light system):
Any other approach lighting System (HIALS, MIALS or ALS 210-419 m)
Q
NALS
(no approach light system):
Any other approach lighting system (HIALS, MIALS or ALS < 210 m) or no approach lights
D - Airfield requirements
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D. Airfield requirements
Presence of touch-down zone lights and/or runway centre line lights has also an impact on minima (Please refer to
Paragraph G.1, Establishing operating minima).
Figure D21: Basic Approach Light System (BALS)
Figure D22: Full Approach Light System (FALS)
7. ATC Procedures
In low visibility conditions the increased operating risk due to the lack of visual control requires that the aerodrome operator or Air traffic service provide specific Low Visibility Procedures (LVP). Those procedures are aimed at maintaining
a safe ground environment for aircraft and vehicles by reducing to a minimum level the risk of collision and infringement
of an active runway.
Each aerodrome authority develops its own procedures taking into account local conditions; however, the main issues
to address are:
–
–
–
–
–
–
–
–
control of any person or vehicle entering on the manoeuvering area,
protection of the OFZ by the control of ground movements,
protection of the ILS critical area and the ILS sensitive area by control of ground movements,
separations between successive landing aeroplanes and between a departing aeroplane overflying the ILS
antennas and the arriving aeroplane,
control of runway access to prevent runway incursion by using, if necessary, any additional ground aids and
equipment,
information of the pilots in case off degradation in ILS performances and/or visual aids,
establishment of appropriate emergency procedures (deployment of rescue and fire fighting services),
reduction of the aerodrome capacity during Low Visibility Operations.
The ATS or airport authority has to define the weather conditions at which low visibility procedures come into operation.
The delay to set up those procedures requires anticipating on weather downgrading: usually LVP are activated before
reaching the CAT II conditions (e.g. when RVR is lower than 600m or ceiling equal or lower than 200ft).
An operator shall verify that Low Visibility Procedures (LVP) have been established, and will be enforced, at aerodromes
where Low Visibility Operations are to be conducted.
Before commencing a Low Visibility Take-Off, a lower than Standard CAT I, an other than Standard CAT II, or a Category
II or III approach, the commander must ensure that appropriate Low Visibility Procedures are in operation.
There are a number of aerodromes which may support Low Visibility Take-Off although they are not approved for Category II or III operations. In such case, low visibility procedures may be lightened. The simplest acceptable LVP may
consist in allowing only one aircraft at a time on the manoeuvering area and in restricting vehicle traffic to the absolute
minimum.
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E. Flight crew
operating procedures
E - Flight crew operating procedures
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E. Flight crew operating procedures
1. General
Operators must develop procedures and operational instructions to be used by flight crews. These procedures and
instructions must be published in the Operations Manual. All the instructions must be compatible with the limitations
and mandatory procedures contained in the approved Aircraft Flight Manual.
The procedures and the operational instructions should cover normal and abnormal situations that can be encountered
in actual operations.
Each airline develops its own procedures taking into account its own specificities. The following chapters give guidance
material on the main items to be covered. Proposed procedures need to be modified or adapted to the airline operating
rules according to the operational regulation in force.
General principles
Q
CAT
II, other than Standard CAT II and CAT III approaches on ATR are ILS approaches for which decision
height (DH) is determined by means of a radio altimeter.
Q
All
CAT Il, CAT III, other than Standard CAT II and lower than Standard CAT I approaches are performed with
the autopilot engaged.
– For CAT II approaches, the autopilot is disconnected at a height of 80ft and the landing is performed manually.
– For CAT IIIA, other than Standard CAT II and lower than Standard CAT I approaches the autopilot is disconnected at touchdown: The approach and landing are performed automatically, the aircraft is controlled manually during the roll-out.
Q
Prior
to conducting a Low Visibility Take-Off, CAT Il approach, CAT III approach, other than Standard CAT II or
lower than Standard CAT I approach, each crew member must be qualified for such operations and have completed an approved training and checking program (please refer to chapter F, Flight crew training and qualification).
Q
CAT
Il, CAT III, other than Standard CAT II and lower than Standard CAT I approaches are conducted according
to a clearly defined task sharing. Basically the pilot flying is the one who acquires the visual references and
takes the decision to land or to carry out a go-around at DH. The Pilot Not Flying has the task of monitoring the
approach with permanent reference to the instruments and to make the appropriate call-outs.
2. Pre-flight procedures
In addition to normal flight preparation, the following planning and preparation must be performed when CAT Il, CAT III,
other than Standard CAT II and lower than Standard CAT I approaches are planned.
Q
Aircraft
status check: review the log book to confirm that no write-up during previous flights affects equipment required for Low Visibility Operations. The required equipment list is given in the FCOM and in the AFM
and is duplicated in the operating manual (please refer to Paragraph C.3, Aircraft minimum equipment required).
The dispatch conditions of the MEL should be in accordance with this list.
Q
Crew
qualification: check that both Captain and First Officer are qualified and current to perform Low Visibility
Operations.
Q
Weather
information: In case of low visibility conditions at take-off or at the destination aerodrome, check that
the weather forecasts at the take-off alternate aerodrome and/or at the destination alternate aerodromes allow
complying with the operating regulation on planning minima.
Q
NOTAMs
review: make sure that at the destination visual aids (runway and approach lighting) and non-visual
aids (ILS, RVR equipment, stand-by power) still meet LVO requirements.
Q
Fuel
planning: assess the need to take extra fuel for possible approach delays.
E - Flight crew operating procedures
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3. On ground procedures and precautions
3.1. General
Ground movement starts from the parking stand to the take-off run, and from the end of the landing roll to the parking
stand.
Many crew members are not aware that taxiing is one of the most critical phases in low visibility conditions. Aerodrome
complexity and traffic density contributes to increase the risk of:
– Mistake in location and identification of taxi routes to be followed,
– Collision with vehicles or other aircraft on the maneuver area, at taxiway intersections or along taxiways,
– Unauthorised entry to an active runway.
The most hazardous situation comes from an unauthorized entry on to an operational runway. In restricted visibility or
at night this can happen without the ATC controller being immediately aware of the situation. On airports approved to
support Low Visibility Operations, active runways are clearly and unmistakably marked. The most common cause of
unauthorised runway incursion is a misunderstood clearance. The crew believes that it has been cleared to enter or
cross a runway and proceeds unless there is some obvious, immediate, danger.
Language difficulties, busy environment, confusing phraseology, congested radio frequencies, cockpit distractions,
time pressure, and similarity of call signs are all factors which may result in a misinterpretation of what has been said.
Conversely, a good understanding of the over-all situation (gained by monitoring the ground frequency), a systematic
request of clearance confirmation at the slightest doubt, a confirmation of clearance to enter a runway by visual signals
(e.g. stop bars if installed) are good means to reduce the risks associated to a misunderstood clearance.
3.2. Recommended procedures
The following procedures could give support in conducting safe and efficient taxi operations
3.2.1. Prior to taxiing
Q
Prepare
and read low visibility taxi charts (when published),
Q
Determine
the expected taxi route to be followed,
Q
Perform
a briefing with a detailed description of the routing between the apron and the holding point by using
the airport chart and/or the low visibility taxi charts (when published); ensure that both crewmembers understand the expected taxi route,
Q
Identify
the main intersections, the direction changes, the holding positions and the areas to be avoided,
Q
Write
down the taxi clearance when received (CM2 copies it on the Nav Log or through the scratch pad which
can be easily use as a short notepad),
Q
Amend
Q
Adjust
the taxi briefing in accordance with the taxi clearance before commencing taxi,
the pilot’s seat and rudder pedals so that it is possible to apply maximum braking with full pedals deflec-
tion,
Q
Start
engine 1 before taxiing,
Q
On
ATR -600 select the airport moving map on both MFD,
Q
On
ATR equipped with an Electronic Flight Bag, activate the airport moving map.
3.2.2. During taxi
Q
In
low visibility conditions taxi with more caution, and at slower speeds,
Q
Both
crew members must be concentrated on the visual surveillance and on the identification of taxi routes to
be followed. Consequently:
– Both CM1 and CM2 must have their taxi charts visible,
– The flight crew should postpone all unnecessary activity and duties,
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E. Flight crew operating procedures
– Taxi actions and checklist, before take-off briefing and company communication are performed preferably
when the aircraft is stopped,
– CM2 should follow taxi progress on the airport diagram, check consistency of taxiway orientation with aircraft
heading, call out all signs to verify position.
– On ATR -600 CM1 and CM2 control aircraft position on the airport moving map (please refer to Paragraph E.4,
Low Visibility Take-Off).
Q
Always
use taxi light to visually indicate movement. (When entering any active runway ensure all exterior lights
are illuminated).
Q
Read
back all clearances: If any crewmember is in doubt regarding the clearance, stop the airplane and verify
taxi routing against the written clearance or with ATC.
Q
In
case of malfunction or if a problem occurs during taxi, stop the aircraft, set parking brake, and inform ATC
before performing any action.
Q
If
and when the crew feels lost or has any doubt on their position, they must ask ATC for help.
3.2.3. Prior to approach phase
Q
When
low visibility conditions exist at destination, the approach briefing should include a detailed description of
the routing from the runway exit to the apron area. Potential difficulties should be addressed in reference to the
airport chart and/or low visibility taxi charts (when published).
Q
As
crew members establish contact with the company staff at destination, they request the assigned stand
number to confirm (or eventually amend) the briefing.
Q
If
it is necessary to cross a parallel runway after landing, the standard procedure is to hold short between runways. The crew members must monitor the tower frequency and be sure to have received a clearance to cross
the runway before proceeding.
3.3. Usual difficulties
Changes in visibility or light intensity, the disappearance of familiar landmarks, the use of a rarely employed taxiway or
runway, an excessive concentration on the taxiway centreline can all contribute to mistakes in location identification
and positioning.
Figure E1: Low Visibility taxiing
Pilots can get confused at intersections if they do not see the signs indicating which taxiway they are crossing. The
problem lies in the fact that the signs are placed a fair distance before the intersection - an important feature which
allows the crew to anticipate -, and that they are not repeated as a confirmation of the intersection. In fact, at a given
intersection, the only visible signs may be those for the next intersection.
For a variety of reasons pilots may face a change of route during the taxi phase: taxiing to the gate is most difficult when
the route is changed in mid-stream. Once pilots get a mental picture of the route they need to take from the runway to
the gate, it is hard to replace it with another route. Such situation requires increased vigilance during taxi routing and
whilst in visual surveillance
E - Flight crew operating procedures
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3.4. Airport moving map
3.4.1. Electronic Flight Bag (EFB)
The PilotView® EFB can be fitted on any ATR version. EFB Chart viewer applications are provided by Jepessen, Lido
or EAG. These interactive viewers allow the display of the aircraft position on the airport charts, from the aircraft GPS
position input. During taxi, this is particularly interesting for pilots maneuvering around unfamiliar airports. This efficiently
increases situational awareness and reduces runway incursions.
3.4.2. ATR -600
The airport NAV provides the flight crew with aircraft progression on airport surface by displaying an aircraft symbol on
the airport map. Nevertheless the other aircraft are not displayed on the map.
Such device is of real assistance to the pilots: it increases efficiency and safety during low-visibility surface operations.
Figure E2: Airport moving map
4. Low visibility take-off (LVTO)
4.1. General
Low visibility take-offs on ATR are performed with the exclusive use of visual references during the take-off run and
eventually during the aborted take-off phase. Consequently for LVTO on ATR:
– there is no specific requirement concerning airborne equipment,
– the standard take-off operating procedure applies.
The airport installation (runway lighting system, RVR measurement system ...) is the determining factor in establishing
the minimum acceptable values of RVR allowing a take-off based exclusively on visual reference.
These minimum RVR values, defined as take-off minima, vary according to the applicable operational regulation. As
an example, the following Paragraph E.4.2 presents the rules applicable for operators subject to European regulation.
In addition to the conditions prescribed by regulation for LVTO, the operator may edit specific instructions such as:
– The Captain is the Pilot flying
– Rolling take-offs are prohibited
– When possible, the full length of the runway is used….
In low visibility conditions it is usually not possible to come back and land at the aerodrome of departure. Consequently,
a suitable take-off alternate aerodrome has to be selected, according to the applicable operational regulation.
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E. Flight crew operating procedures
4.2. Low Visibility Take-Off under European regulation (EU-OPS)
Operators must verify that Low Visibility Procedures (LVPs) have been established and will be enforced at aerodromes
where Low Visibility Take-Offs are to be encountered.
Conversion of reported meteorological visibility into RVR (please refer to Paragraph B.3.5, Conversion of reported meteorological visibility to RVR) is not permitted at take-off.
Take-offs with RVR less than 400m are considered by EU-OPS as LVTO and are split into two categories:
LVTO with RVR between 400m and 150m
No operational approval is required to perform LVTO with these minima. The minimum RVR depends on the runway
lighting and markings and on the RVR measurement system, in accordance with the table below:
Ground facilities
RVR/ visibility(1)
Nil (day only)
RVR/visibility ≥500m
Runway edge lighting and/or centreline marking (for night
operation, edge and runway end lights are required)
500m> RVR/visibility ≥250m
Runway edge and centreline lighting
250m> RVR/visibility ≥200m
Runway edge and centreline lighting and multiple RVR
information
200m> RVR/visibility ≥150m(2)
(1)
The reported RVR/Visibility value representative of the initial part of the take-off run can be replaced by pilot
assessment.
(2)
RVR must be achieved for all of the relevant RVR reporting point (covering the acceleration/stop distance)
except for the initial part of the take-off run that can be replaced by pilot assessment.
LVTO with RVR lower than 150m but not lower than 125m
Take-offs in this range of RVR are subject to an operational approval by the Authority. Both flight crew members must
be qualified for such operations and have completed training in a flight simulator (please refer to Chapter F, Flight crew
training and qualification). The following conditions must also be met:
– High intensity runway centreline lights spaced 15m or less and high intensity edge lights spaced 60m or less are
in operation,
– A 90m visual segment is available from the cockpit at the start of the take-off run,
– The 125m RVR value has been achieved for all of the relevant RVR reporting points (no exemption for the initial
part of the take off run).
NOTE: The obscured segment for an ATR aircraft on ground is only 8 meters. Consequently, with 125m RVR, the condition on a 90m visual
segment should not be a limiting condition.
Example: EU OPS Take-off minima published for Toulouse Airport
RVR <400m: low visibility take off.
LVP must be in force.
Conditions on ground facilities
and
Associated RVR
For CAT B (ATR)
Minimum RVR of 125m for Approved Operators
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Summary of flight crew actions before commencing a Low Visibility Take-Off under
European regulation
Q
check
that low visibility procedures are active,
Q
check
that the reported Visibility/RVR is not below the published minima (or the operator minima, if higher) according to the lighting and markings available,
Q
check
that a take-off alternate aerodrome is available: as ATR aircraft are not certified to perform CAT II or
CAT III approaches with one engine out, when the reported RVR is below the minimum value required for
a Category I approach on the departure aerodrome (basically 550m), a take-off alternate aerodrome with
weather conditions above the landing minima must be selected (please refer to EU-OPS 1.297, Planning minima
for IFR flights),
Q
for
take-off with RVR=125m check that the additional conditions are satisfied (Operator approval, crew qualification, runway lights spacing, visual segment, RVR for all relevant reporting points),
Q
apply
standard take-off procedures and task sharing, except if airline policy introduces specific requests.
5. Approach preparation
The following actions have to be performed preferably before the start of descent and in any case before the beginning
of the approach phase.
5.1. Conditions at destination / at the alternate aerodrome
When low visibility conditions are expected at destination, the flight crew should take ATIS as soon as possible.
A weather analysis allows the crew to determine if present conditions require a low visibility approach and if the wind
is compatible with the CAT II/III wind limitation (please refer to Paragraphs B.2.2, The effect of wind and turbulences and
C.1.4, AFM content).
The weather at the selected alternate aerodrome should also be collected. It must be checked that weather conditions at the destination or at the alternate aerodrome will be, at the expected time of arrival, above the operating
minima. If weather conditions at destination are below the operating minima, the flight can be continued towards
the destination (but not beyond the approach ban point) as long as conditions at the alternate are above the landing
minima.
If a CAT Il, CAT III, other than Standard CAT II or lower than Standard CAT I approach is likely, it must be check that
LVPs are reported active.
If any ground equipment is reported unserviceable, the effect on the minima must be determined (please refer to Paragraph E.8, Effects of failure of ground equipments).
5.2. Aircraft capability
Flight crew members must verify the technical status of the aircraft to ensure that it has the capability to perform a low
visibility approach. They must consider any equipment out of order, including that which failed during the flight. It must
be checked, by using the lists published in the AFM and in the operating manual (please refer to Paragraph C.3, Aircraft
minimum equipment required), that the minimum equipment required to perform CAT Il, CAT III, other than Standard CAT
II or lower than Standard CAT I approach is available.
5.3. Fuel calculation
When low visibility procedures are in force on an airfield, spacing between aircraft is increased and the number of
runways in use may be reduced. The airport may have been closed for a time with several aircraft already waiting
for weather improvement. If weather conditions are fluctuating, some aircraft going around may attempt another approach. For all these reasons, low visibility conditions often generate holding time for arriving aircraft. Consequently
E - Flight crew operating procedures
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E. Flight crew operating procedures
it is necessary to perform an accurate fuel management to establish the maximum holding time at destination before
diverting. The crew should also consider the risk of holding due to a large number of diverting flights at the alternate
aerodrome.
5.4. DH setting
In addition to the standard setting performed prior to any ILS approach (speeds bugs, TQ bugs, Markers volume), for
a CAT II, other than Standard CAT II or CATIII approach, the DH of the procedure must be set and cross-checked.
A radio altimeter test is recommended.
Figure E3: DH setting on EADI
5.5. Approach briefing
The approach briefing should include normal items, as for any IFR arrival, and in addition, the following subjects should
be covered prior to a low visibility approach:
Q
qualification
of each flight crew member,
Q
aircraft
systems status and capacity,
Q
airfield
and runway operational status CAT II / CAT III, LVP in force…,
Q
weather
Q
holding
conditions at destination, compatibility with the applicable minima,
time available before diverting,
Q
brief
review of task sharing and call-outs,
Q
brief
review of procedure in case of malfunction above and below 800ft,
Q
review
of routing from the runway exit to the apron area,
Q
review
of the go-around procedure,
Q
alternate
aerodrome selected and weather conditions.
5.6. Cabin crew information
A low visibility approach requires a specific task sharing between flight crew members. Both must be concentrated
on systems monitoring and on the actions and call-out sequencing. In order to maintain a sterile cockpit during such
approaches, the cabin crew must be informed that a low visibility approach will be performed. They are invited to not
disturb the flight crew and to avoid awkward calls, except in case of emergency.
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5.7. Seat position
Each flight crew member has to adjust his seat height and position
to obtain an optimum visual segment. The seat is correctly adjusted when the pilot’s eyes are in line with the red and white balls
located above the glare shield.
Figure E4: Seat position setting
6. Normal procedures for low visibility
approaches
6.1. General
CAT II approaches are conducted in automatic mode down to 80ft RA, the autopilot is disconnected at 80ft and landing
and roll out are performed manually.
CAT III, other than Standard CAT II and lower than Standard CAT I approaches are conducted in automatic mode, with
the speed hold function engaged all the way to touchdown. The roll-out is performed manually.
The go-around is performed manually using the flight director guidance.
The DH recognition is made in reference to the height measured by radio-altimeter and all height call-outs are based on
the radio altimeter. The approach may be continued below DH provided that the required visual reference is established
at the DH.
Flight crew members’ duties during approach, flare, roll-out and missed approach are to be clearly delineated in the
Operations Manual. Special attention should be paid to the allocation of flight crew duties so as to ensure that the
workload of the pilot making the decision to land or to execute a missed approach enables the pilot to concentrate on
supervision and on the decision-making process.
The task sharing proposed in Paragraph E.6.3 here below is one example of how to conduct a low visibility approach. It
can be adapted by operators to be consistent with their own standard procedures; nevertheless, the AFM procedures
must always be observed.
6.2. Approach ban / RVR controlling
Policy regarding approach ban and RVR controlling may slightly differ according to the operational regulation applied.
EU rules for approach ban and RVR controlling (cf. EU OPS 1.405):
Q
The
approach shall not be continued beyond the OM or equivalent position or 1000ft above the aerodrome
(where no OM or equivalent position exists) if the reported RVR is less than the applicable minima.
Q
After
passing this position, if the RVR falls below the applicable minima, the approach may be continued to DH.
The touchdown zone RVR is always controlled. If reported and relevant, the mid-point and the stop-end point
are also controlled: the minimum RVR value for mid-point is 125m and 75m for the stop-end point.
Relevant means: part of the runway used during the high speed phase of the landing down to a speed of approximately 60kts.This has to be appreciated taking into account the conditions of the day. Nevertheless, most
of the time, given the ATRs’ landing distance (usually short), only TDZ RVR needs to be controlled.
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E. Flight crew operating procedures
In summary, when passing OM or equivalent position if the last transmitted RVR for touch down zone is below
the operating minima, a go-around is initiated.
6.3. Task sharing
ATR AFM and FCOM procedures for low visibility approaches indicate task sharing between PF and PNF without
specifying the real position of PF. This was intentionally done to give airlines the possibility of adapting their own
policy. At the ATR Training Centres the recommended task sharing for low visibility approach is that CM1 is PF and
CM2 is PNF.
The workload is distributed in such a way that PF primary tasks are supervising and decision making, and the PNF
primary task is the monitoring of automatic systems.
In summary tasks are enacted and shared as follows:
CM1 - PF
Q
is
head down during approach,
Q
monitors
Q
controls
Q
has
A/C position, flight path parameters and AP,
the speed,
hands on controls and power levers throughout the approach,
Q
selects
modes and announces changes,
Q
requests
checklists, flaps setting and gear extension,
Q
is
head up approaching DH to search visual references,
Q
at
DH, announces the decision to land or to go around,
Q
in
CAT II: takes manual control at 80 ft and performs a manual landing,
Q
in
CAT III, monitors flare and de-crab, at touchdown disconnects auto pilot, retards power levers and takes
manual control for the roll-out.
CM2 - PNF
Q
is
head down to monitor flight instruments throughout approach, go-around or landing until rollout completion,
Q
takes
charge of radio communications,
Q
carries
Q
calls
out actions requested by CM1 (flaps setting, gear extension, AFCS (or FGCS) selection),
any deviation or failure warning,
Q
monitors
auto call-out or calls out radio heights including “100 above”,
Q
at
DH, if decision is not announced by CM1, calls out “DECISION”- If no response from CM1, initiates a goaround.
6.4. Normal procedures on classic instruments ATR for
CAT II approaches
The Table here below presents the detailed task-sharing recommended by ATR Training Centres for CAT II approaches
with ATR-500 series, but it can be extended to other classic instruments ATR.
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E: Execute
A: Announce
C: Check
FLIGHT EVENTS / ACTIONS
O: Order
Items specific to CAT II
CM1 (PF) ANNOUNCEMENTS
CM2 (PNF) ANNOUNCEMENTS
REMARKS
CM1
CM2
E
E
PF
E
PNF
E/A
E/A
E
C
C
E
“ILS NAV 1set” - adjust Marker volume
“NAV 2 VOR set”
E /A
C
O/E
A
O
C
O
O
E/A
A
E
C
E
A
E/C
E
“Approach mode set”
“LOC white, G/S white”
“VOR alive”
“LOC star”
“Runway Axis confirm”
“Set RWY HDG, Dual ILS”
“Rwy HDG set, Dual ILS set”
“CAT II Capability”
“STBY horizon checked”
“Glide slope alive”
“Flaps fifteen”
“Speed checked” - set flaps to 15°
“Flaps fifteen”
“Speed bug white bug plus 10”
“one dot”
“Gear down”
“Speed checked” - set LDG lever down,
PWR MGT to TO, Taxi light ON
“LDG gear down”
“Half dot”
“Flaps 30”
“Speed checked” - set flaps to 30°
“Flaps 30”
“Speed bug V approach”
“G/S star”
“Set go-around altitude”
“XXX ft set”
“Before Landing C/L”
“Center HDG bug”
Outer marker or equivalent position
but not lower than 1000ft
Check the altitude on radio altimeter
and altimeter
Check that A/C is stabilized
C
C/A
“Outer, altitude checked, stabilized” (1)
A
C
800ft RA
Check dual coupling and no stars
on LOC or G/S
500ft RA
Speed maintain to Vapp +10kts/-5kts
DH +100RA
CM1 head up
CM2 Head down
DH (RA)
C
C/A
“Eight hundred, Dual coupling, No star”
CM2 starts monitor ILS deviation
C
E
C
A
C (A)
A
“500”
Before descent
CAT II briefing
RA test / DH setting
Not later than IAF
Before Localizer interception
NAV 1 ILS
NAV 2 VOR (or ILS)
ILS/VOR identification
Cleared for approach
App mode selected
VOR alive
LOC star
Check HDG/Course/QFU
HDG bug on RWY HDG / NAV 2 ILS
CAT II on ADU
Check STBY Horizon
G/S alive
Flaps to 15°
A
O
A
E/A
C
A
O
Flaps 15
O/E
G/S one dot
Gear to down
A
C
E/A
E/A
E/A
A
E
A
O
E/A
Three Green lights
G/S ½ dot
Flaps to 30°
A
A
O
Flaps 30
G/S star
Set Go-around altitude
Before landing C/L
Heading bug centered
A
“We continue”
“Hundred above”
CM1 look outside for visual references
“Decision”
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E. Flight crew operating procedures
If visual references sufficient
E: Execute
A: Announce
C: Check
O: Order
FLIGHT EVENTS / ACTIONS
Approach is continued
80ft RA
AP disconnection
50ft RA
20ft RA
CM1
Items specific to CAT II
CM2
A
CM1 (PF) ANNOUNCEMENTS
CM2 (PNF) ANNOUNCEMENTS
REMARKS
“Landing”
C
E/A
A
C
“80”
“AP off”
CM1 disconnects AP at 80 ft(2)
C
C
A
A
“50”
“20”
CM1 reduces PL and performs a
manual landing
CM2 remains head down until aircraft is
on the ground with IAS< 70kts
A
A
“Two low pitch”
“70 kts”
“I have control”
A
“Runway vacated” message to ATC
Low pitch
70kts
A
Runway vacated
(1)
Stabilised means: – On the final approach segment flight path
– In landing configuration at Vapp speed
– Final checklist completed
(2)
On aircraft fitted with MOD 0069, AP can be disconnected between 80ft and 50ft (50ft is the minimum height
certified for use of autopilot in approach mode)
If no visual or loss of visual reference or wrong positioning
FLIGHT EVENTS / ACTIONS
Approach is discontinued
Normal Go-around procedure
CM1
CM2
A /E
E
CM1 ANNOUNCEMENT
CM2 ANNOUNCEMENTS
REMARKS
“Go-around – set power - Flaps one notch”
E
CAT 2 message on ADU
The CAT2 message must be displayed before proceeding to Category II approach
minima. This message remains displayed for
the duration of the approach if all the CAT II
conditions remain satisfied.
If those conditions are lost the CAT2
INVALID message flashes on ADU.
(Please refer to Paragraph C.2.1, AFCS on
classic- instruments ATR)
Figure E5: CAT 2 display on ADU
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Dual couple approach mode
Dual coupling is confirmed by checking that both the CPL arrows are displayed on the AFCS control panel.
(Please refer to Paragraph C.2.1, AFCS on classic instruments ATR, for dual
coupling conditions)
Figure E6: CPL on AFCS control panel
Key points for a CAT II approach
– IAF: if the pilot flying on the flight leg is CM2, then CM1 should become PF not farther than IAF.
– OM or equivalent position but not lower than 1000ft: it is the approach ban point. This point is also used to
confirm glide slope and to check stabilisation.
– 800ft RA: LOC and GS must be fully captured (no *) and dual coupling confirmed – this point is also a key point
in failure management logic: below 800ft RA any failure should conduct to a go-around (Please refer to Paragraph
E.7, Abnormal procedures).
– DH +100ft: CM1 moves head up and searches visual references.
– DH: CM1 decides to land or to go around.
– 80ft: CM1 disconnects AP.
NAV 2 VOR set
CALL-OUTS
DURING A CATEGORY II
APPROACH
ILS NAV 1 set
Approach mode set
LOC white, GS white
GS star
Set go around
altitude
Speed bug white
bug +10
CM1 (PF) call-outs
STBY horizon
checked
Speed bug
V approach
CM2 (PNF) call-outs
Gear down
Before LDG C/L
Flaps 30
LOC star
CAT II
capability
Flaps 15
Center HDG bug
Go around
set-power
flaps one notch
Half dot
xxxft set
We continue
Speed checked
Flaps 30
Outer,
Altitude checked,
Stabilized
500
Landing
80
AP off
50
20
100
above
Decision
100ft
RA
800ft
RA
One dot
Speed checked
Flaps 15
VOR alive
Set RWY
HDG, dual
ILS
RWY HDG set,
Dual ILS set
RWY axis
confirm
LDG gear down
Glide slope alive
Eight hundred,
Dual coupling,
No star
Two low pitch
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E. Flight crew operating procedures
6.5. Normal procedures and task sharing for CAT III, other
than Standard CAT II and lower than Standard CAT I
approaches on ATR -600
For later revision.
6.6.Visual segment at DH and minimum visual references
The minimum visual references allowing at the decision height to continue the approach and landing must be clearly
defined in the Operations Manual and be in accordance with the applicable operational regulation.
Figure E7: Visual segment approaching CAT II minima
Figure E8: Visual segment at 80 ft
In CAT II conditions, the visual cues must be sufficient to enable the pilots to judge the aircraft’s orientation to the runway and to perform a manual landing.
In CAT III, visual cues must allow the pilot to decide if the aircraft will land in the touch down zone.
In order to establish lateral position and cross track velocity most pilots need not less than a 3 lights segment of the
centreline of the approach light, or runway centre line or runway edge lines.
For roll guidance, most pilots need to see a lateral element of the ground pattern (e.g an approach lighting cross bar,
the landing threshold, or a barrette of the TDZ). To make an accurate adjustment to the flight path in the vertical plane,
such as a flare, most pilots need to see a point on the ground which has a low or a zero rate of apparent movement
relative to the aircraft.
On the basis of those findings, the European regulation states that a pilot may not continue an approach below DH
unless visual references in accordance with the table hereunder are obtained and maintained.
Use of landing lights at night in low visibility conditions can be detrimental to the acquisition of visual references. Reflected lights from water droplets or snow may actually reduce visibility. Landing lights would therefore not normally be
used in Category II/III weather conditions.
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CAT II
Other than stand. CAT II
Lower than stand. CAT I
CAT III A
3 consecutive lights of :
– the centre line of the approach lights,
– or the touchdown zone lights,
– or the runway centreline lights,
– or the runway edge lights,
– or a combination of these
X
X
A lateral element of the ground pattern:
– Approach lighting cross bars,
– or threshold
– or barrettes of the TDZ
X
Visual references
Table E1: visual references vs. approach categories
If the RVR is at the minimum value of the approach category (300m for CAT II, 200m for CAT IIIA) the visual segment at
the decision height should be as shown on the drawings below:
Zone
obscured
by fog
Visual
segment
Zone
obscured
by aircraft
nose
Figure E9: Visual references at 100ft with 300m RVR
Figure E10: Visual references at 50ft with 200m RVR
6.7. Loss of visual references below DH
Before touchdown, when the decision to continue has been made, if the visual references subsequently become insufficient, or if the flight path deviates unacceptably, a go-around must be initiated.
7. Abnormal procedures
7.1. General
There are three possible responses to the failure of any system, instrument or element during a low visibility approach.
– Continue the approach to the planned minima,
– Continue the approach to higher minima and proceed to a new DH or DA,
– Go-around, reassess the capability and consider a new approach or a diversion.
The nature of the failure and the point of its occurrence will determine which response is appropriate.
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E. Flight crew operating procedures
7.2. Failure treatment concept
In the Operations Manual, each operator has to develop its own abnormal procedures, in agreement with its Authority.
ATR recommends that any failure occurring during a low visibility approach be treated in accordance with the following
general rule:
Q
If
associated actions, checklist and assessment are completed before reaching 800ft RA:
– The approach can be continued to the planned minima if the failure does not affect the aircraft capability,
– The approach can be continued to higher minima if the failure allows reversion from CAT II, lower than Standard CAT I, other than Standard CAT II to CAT I or from CAT III to CAT II or CAT I. In such cases the reported
RVR must be above the new category’s minima; a short briefing is made and the new DH or DA is set.
– If none of the previous situations apply, a go-around is performed and a diversion is considered
Q
If
associated actions, checklist and assessment are not completed before reaching 800ft RA or if failure occurs below 800ft RA
– A go-around is performed, the aircraft capability is reassessed and according to the weather conditions, the
flight crew decides to perform a new approach or to divert.
It has been considered that below 800ft, not enough time is available for the crew to perform the necessary switching,
to check system configuration and limitations and brief for minima.
Nevertheless if visual references are obtained at the time of failure’s occurrence the Captain may decide to continue the
approach considering the aircraft position and the kind of failure.
The operator policy may also decide to make some exemption to this general rule for some very specific events (engine
fire, smoke in the cabin…) where it may be considered preferable (Captain decision) to continue the approach.
The failure treatment
is completed before
800ft RA and
CAT II / III capability is not affected
£
CAT II/III approach is continued
CAT II / III capability is affected
Reversion to higher minima is possible
£
Approach is continued
to higher minima
CAT II/III capability is affected
£
Reversion to higher minima is not possible
Go-around
800ft
RA
The failure treatment is
not completed before
800ft RA
Go-around
Go-around
The failure occurs
between 800ft RA
and DH
DH
The failure occurs below DH £ Captain decision to land or to go-around
according to the type of failure, the visual
references and the aircraft position
Figure E11: Failure treatment logic during CAT II/III approaches
7.3. Failure treatment on classic instruments ATR
Guidance material is available in the Aircraft Flight Manuel on the effect of some failures during a CAT II approach (please
refer to Paragraph C.4, Aeroplane malfunctions).
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Those failures and their associated procedures have to be developed in details in the airline’s Operations Manual.
A summary is given hereunder:
Q
Failures
for which a reversion to CAT I minima is possible if failure has been completely treated before reaching
800ft (considering CM1 is PF):
– Flaps failure (jammed between 0 and 15°)
– Engine failure
– Failure of two MFC modules
– Flag on standby horizon
– Radio altimeter
– EFIS COMP -ATT/PIT/ROLL warning on any EFIS
– EFIS COMP - HDG warning on any EFIS
– EFIS COMP - LOC/GS/ILS warning on any EFIS
– Loss of both CRT on one side (SGU failure)
– Loss of Airspeed indicator 1 or 2
– Loss of Altimeter 1 or 2
– AP disengagement (with impossibility to recover)
– Loss of ADU
– Loss of CAT II capability (with impossibility to recover)
Q
Failures
which do not prevent continuation of the approach to CAT II minima if the failure has been completely
treated before reaching 800ft:
– Flaps failure (jammed above 15°)
– Hydraulic failure without fluid loss (blue and green circuit available)
– Failure of one MFC module
– Loss of one CRT
– Master Caution or Master Warning for any other event which do not cause one of the failure or warning address here above chapter E.7.2 and E.7.3.
Comments
Q
ATR
aircraft are not certificated for CAT II approaches with one engine out; nevertheless in conditions equal or
better than CAT I, a single engine approach can be performed with the autopilot engaged.
Q
The
STBY horizon must be operative during a CAT II approach because in case of:
– CAT II INVALID message,
– excess deviation (please refer to Paragraph E.7.5, Maximum ILS deviation allowed),
– AFCS failure,
– EFIS COMP,
a Go-around must be performed by using the STBY horizon with an initial missed approach pitch of 10°.
Q
RA
Failure: If the radio altimeter fails, amber dashes replace the digital display, and the rising runway (if displayed) is removed.
Q
The
ADU must be operative for the display on it of CAT II capability and “CAT II INVALID” messages.
7.4. Failure treatment on ATR -600
For later revision.
7.5. Maximum ILS deviation allowed
As for any approach, in case of flight parameters’ deviation, the PNF must make the appropriate calls:
DEVIATION
CALLs
IAS: +10 Kts / –5 Kts
speed
Bank angle >10°
bank
Pitch attitude: ± 4°
pitch
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E. Flight crew operating procedures
The excessive ILS deviation monitor is active during dual coupled Category II approaches. Glideslope deviation is
monitored between 500 feet and 100 feet AGL, and localizer deviation is monitored between 500 feet and 0 feet AGL.
Excessive deviation threshold
Localizer
1/3 dot
Glideslope
3/4 dot
On classic instruments ATR, if excessive deviation is detected, the associated scale and pointer turn amber and flash
and the message EXCESS DEV is displayed on the ADU. If installed, the Guidance warning light located in the primary
field of view of the pilot is also triggered.
If this warning occurs during a CAT Il, CAT III, other than Standard CAT II or lower than Standard CAT I approach, the
PNF announces “Deviation” or “Guidance” and the PF initiates a go-around except provided that visual references are
sufficient.
8. Effects of failure of ground equipment
Aerodrome facilities are expected to be installed and maintained to the prescribed standards in ICAO annexes 10 and
14. Any deficiencies are expected to be repaired without unnecessary delay. If the failure can not be fixed and concerns
the ILS, the lighting, or the RVR measurement equipment, the general rule for the crew is to consider that the CAT II or
CAT III approach is no longer available.
Nevertheless and depending on the operational regulation applied, it may be accepted that a simple or partial failure
does not prevent a low visibility approach or merely leads to increased minima.
As an example, the table here below shows the effect of failure of ground equipment for operators applying the European regulation:
Failed or downgraded equipment
Approach lights
Approach lights except the last 210m
EFFECT ON LANDING MINIMA
CAT IIIA
CAT II
Not allowed for operations with
DH>50ft
Not allowed
No effect
Not allowed
Approach lights except the last 420m
No effect
Standby power for approach lights
No effect
Whole runway light system
Edge lights
Centreline lights
Not allowed
Day only / Night – not allowed
Day – RVR 300m
Night – not allowed
Centreline lights spacing increased to 30m
Touchdown zone lights
No effect
Day – RVR 300m / Night – RVR 550m
Standby power for runway lights
Taxi light system
ILS standby transmitter
Day – RVR 300m
Night – RVR 550m
Not allowed
No effect- except delays due to reduced movement rate
Not allowed
No effect
Outer marker
No effect if replaced by published equivalent position
Middle marker
No effect
Touch Down Zone RVR assessment system
Midpoint or stopend RVR
Anemometer for Rwy in used
Celiometer
May be temporarily replaced with midpoint RVR if approved by the
State of the aerodrome. RVR may be reported by human observation
No effect
No effect if other ground source available
No effect
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NOTE:
– Multiple failures of runway lights other than indicated in this table are not acceptable.
– Deficiencies of approach and runway lights are treated separately.
– A combination of deficiencies in runway lights and RVR assessment equipment is not allowed.
– Failures other than ILS affect RVR only and not DH.
This table is intended for use both pre-flight and in-flight. It is not expected however that the commander would consult
such instructions after passing the outer marker or equivalent position. If failures of ground aids are announced at such
a late stage, the approach could be continued at the commander’s discretion. If however failures are announced before
such a late stage in the approach, their effect on the approach should be considered as described in the table, and the
approach may have to be abandoned to allow this to happen.
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F. Flight crew training
and qualification
F - Flight crew training and qualification
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1. General
Operators must provide appropriate training and qualification for each pilot intended to perform Low Visibility Operations. Training and crew qualification programs should include provisions for appropriate ground training, simulator
training, and recurrent training.
Flight crew members are expected to have a comprehensive level of knowledge with respect to each of the ground
training subjects. During the simulator training pilots are expected to perform the relevant procedures or applicable
manoeuvers and must demonstrate having the skill to perform their assigned duties.
The training program must be related to the aeroplane type, to the particular airborne system and to the operating procedures adopted by the operator. Operational regulation establishes the minimum content of those training program.
ICAO, FAA and EASA regulations are quite similar.
Training and qualification program provided in the following paragraph is based on EASA requirements. Each flight crew
member must have successfully completed this training and qualification program prior to conducting:
– Low visibility take-offs in less than 150m RVR
– Lower than Standard Category I approaches
– Other than Standard Category II approaches
– CAT II and CAT III approaches
2. Ground training
It is the operator’s duty to establish a ground course to ensure flight crew understands the specific environment of
Low Visibility Operations and that they have a good knowledge of characteristics and limitations of both ground and
airborne equipment.
The European regulation requests that at least the following items be covered (cf. Appendix 1 to EU-OPS 1.450 (b)).
1. The characteristics and limitations of the ILS and/or MLS.
Please refer to Paragraph D.5
2. The characteristics of the visual aids.
Please refer to Paragraph D.6
3. The characteristics of fog.
Please refer to Paragraph B.1
4. The operational capabilities and limitations of the particular airborne system.
Please refer to Paragraphs C.1 & C.2
5. The effects of precipitation, ice accretion, low-level windshear and turbulence.
Please refer to Paragraph B.2
6. The effects of specific aircraft malfunctions.
Please refer to Paragraph C.4
7. The use and limitations of RVR assessment system.
Please refer to Paragraph B.3
8. The principles of obstacle clearance requirement.
Please refer to Paragraph D.4
9. Recognition of and action to be taken in the event of failure of ground equipment.
Please refer to Paragraph E.8.
10. The procedures and precautions to be followed with regard to surface movement during operations when
the RVR is 400m or less and any additional procedures required for take-off in conditions below 150m.
Please refer to Paragraphs E.3 & E.4
11. The significance of decision heights based upon radio altimeters and the effect of terrain profile in the approach area on radio altimeter readings and on the automatic approach/landing system.
Please refer to Paragraph D.3
13. The qualification requirements for pilots to obtain and retain approval to conduct Low Visibility Take-Off
and CAT II and CAT III operations.
Please refer to Chapter F
14. The importance of correct seating and eye position.
Please refer to Paragraph E.5.7
Flight crew members with previous CAT II or CAT III experience with the operator or with another European operator may undertake an abbreviated ground training course.
F - Flight crew training and qualification
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F. Flight crew training and qualification
3. Simulator training and checking
3.1. Full training program
Each flight crew member must be trained to carry out his/her duties appropriate to the particular airborne system as
well as be instructed on the coordination required with other crew members. Maximum use should be made of flight
simulators capable of performing the specified manoeuvers, and which can appropriately represent the limiting visual
conditions related to the applicable minima.
EASA requirements are detailed in Appendix 1 to EU-OPS 1.450 (c & f). The main outlines of this document are explained here below:
Training must be divided into phases covering normal operations with no aeroplane or equipment failure but including
all weather conditions which may be encountered and detailed scenarios of aeroplane and equipment failures which
could affect Category II or III operations.
The initial simulator training program for Low Visibility Operations must include the following items (1 to 7) and the following exercises (8 to 19):
1. checks of satisfactory functioning of equipment, both on the ground and in flight;
2. effect on minima caused by changes in the status of ground installations;
3. monitoring of automatic flight control systems and autoland status annunciators with emphasis on the action to be taken in the event of failures of such systems;
4. actions to be taken in the event of failures such as engines, electrical systems, hydraulics or flight control
systems;
5. the effect of known unserviceabilities and use of minimum equipment lists;
6. operating limitations resulting from airworthiness certification;
7. guidance on the visual cues required at DH together with information on maximum deviation allowed from
glidepath or localizer;
8. approach using the appropriate flight guidance, autopilots and control systems installed in the aeroplane,
to the appropriate decision height and to include transition to visual flight and landing;
9. approach with all engines operating using the appropriate flight guidance systems, autopilots, and control
systems installed in the aeroplane down to the appropriate decision height followed by missed approach;
all without external visual reference;
10. where appropriate, approaches utilising automatic flight systems to provide automatic flare, landing and rollout;
11. normal operation of the applicable system both with and without acquisition of visual cues at decision height;
12. approaches with engine failure at various stages on the approach;
13. approaches with critical equipment failures (e.g. electrical systems, auto flight systems, ground and/or
airborne ILS/MLS systems and status monitors);
14. approaches where failures of auto flight equipment at low level require either;
– reversion to manual flight to control flare, landing and roll out or missed approach; or
– reversion to manual flight or a downgraded automatic mode to control missed approaches from, at or
below decision height including those which may result in a touchdown on the runway;
15. failures of the systems which will result in excessive localizer and/or glide slope deviation, both above and
below decision height, in the minimum visual conditions authorized for the operation.
16. failures and procedures specific to aeroplane type or variant.
17. practice in handling faults which require a reversion to higher minima.
18. handling of the aeroplane when, during a fail passive Category III approach, the fault causes the autopilot
to disconnect at or below decision height when the last reported RVR is 300 m or less.
19. incapacitation procedures appropriate to Low Visibility Take-Offs and Category II and III operations.
20. take-offs with RVRs of 400 m and below: systems failures and engine failure resulting in continued as well
as rejected take-offs.
F - Flight crew training and qualification
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21. take-offs in RVRs below 150 m:
– normal take-off in minimum authorised RVR conditions;
– take-off in minimum authorised RVR conditions with an engine failure between V1 and V2, and
– take-off in minimum authorised RVR conditions with an engine failure before V1 resulting in a rejected
take-off.
Example of LVO syllabus for initial training on classic instruments ATR
LVO
Nb
1
Partial
time
Total
time
RVR 125m
RVR 300m, ceiling 120ft
Simulator freeze at 100ft / 50ft – view of
visual references in day, dusk and night
condition
0h25
0h25
LVO EXERCISES
REMARKS
LVTO - radar vectoring
Full CAT II briefing
CAT II approach / freeze at DH / landing
2
Repositioning base leg
CAT II approach - landing
RVR 300m; ceiling 120ft
0h10
0h35
3
LVTO - radar vectoring
Full CAT II briefing
CAT II approach
No visual reference – Go around
RVR 125m
RVR 300m, ceiling 120ft
RVR 300m, ceiling 50ft
Engine failure at go around
0h25
0h55
4
Engine restart in down wind
CAT II approach
F/O decision / Go around
RVR 300m, ceiling 120ft
Captain incapacitation at 1300ft
Research of diverting airport
0h15
1h10
5
Radar vectoring to base leg
CAT II approach
Captain decision
Go around with STBY horizon
RVR 300m, ceiling 120ft
At 500ft: Drift roll EADI
0h15
1h25
6
Radar vectoring to base leg
CAT II approach
Go around
RVR 300m, ceiling 120ft
auto-pilot failure at 400 ft
0h15
1h40
7
Repositioning to base leg
CAT II approach
Reversion to CAT I - Landing
Flaps jam 15° at 2000ft
RVR 550m ceiling 220ft
0h10
1h55
8
LVTO
Aborted take off
RVR 125m
Engine failure before V1
0h05
2h00
0h05
2h05
9
LVTO
FO’s decision – carrying on T/O
RVR 125m
Captain incapacitation at 90kts
0h05
2h10
10
Radar vectoring
CAT II approach
Excess deviation - Go around
RVR 300m, ceiling 120ft
LOC deviation at 200ft
0h15
2h25
11
Radar vectoring to base leg
Procedure and C/L
CAT I approach- landing
RVR 400m,
RA failure at 2000ft
RVR 550m ceiling 220m
Reversion to CAT I
0h20
2h45
12
LVTO
RVR 125m – ceiling 120m
Engine failure between V1&V2
Engine restart- RVR 300m
“CAT 2 invalid” at 800ft
0h20
3h05
15
3h20
BREAK
Radar vectoring to base leg
CAT II approach - Go around
13
Radar vectoring to base leg
CAT II approach
Captain decision – go around
RVR 300m, ceiling 120ft
ADC failure at 500ft
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F. Flight crew training and qualification
14
Repositioning 10Nm
CAT II approach
Captain decision – go around
RVR 300m, ceiling 120ft
Loss of ADU at 1500ft
10
3h30
15
Repositioning 10Nm final
CAT II approach
Captain decision – go around
RVR 300m, ceiling 120ft
Loss STBY horizon at 1200ft
10
3h40
16
Radar vectoring
CAT II approach
Captain decision: app. Continued
Captain decision : landing
RVR 300m, ceiling 120ft
FO’s EADI failure at 1200ft
20
4h00
Engine fire at 400ft
Example of LVO syllabus for initial training on ATR -600
For later revision.
3.2. Training for flight crew members with Category II or
Category III experience
The flight simulator course may be abbreviated for flight crew members who gained Category II/III experience with:
– another European Community Operator through a similar type of operation (auto coupled/auto-land or Category
II with manual land) on the same type and variant of aeroplane
or
– the operator but on a different type or variant of aeroplane.
The abbreviated flight simulator course consists of a minimum of six approaches and/or landings in a flight simulator.
With the approval of the Authority the operator may reduce this number of approaches/landings.
More details on conditions allowing abbreviating the flight simulator course are given in Appendix 1 to EU-OPS 1.450
(a&d).
3.3. Training for flight crew members flying on classic
instruments ATR and on ATR -600
For later revision.
3.4. Flight crew qualification
Following completion of ground and simulator training, flight crew members must demonstrate their competency to the
appropriate authorities. Each pilot undergoes a check before conducting Category II/III operations and/or Low Visibility
Take-Off with RVR below 150m. This check may be replaced by successful completion of the flight simulator training
prescribed here above.
4. Line training
Once the simulator training and checking program has been completed, each flight crew member undergoes the following line flying under supervision (LIFUS) before initiating Category II or III approaches: (cf. Appendix 1 to EU-OPS
1.450 d (4))
Q
For
Category II when a manual landing is required, a minimum of three landings from autopilot disconnect;
except that only one manual landing is required when the flight simulator training required has been carried out
in a flight simulator qualified for zero flight time (ZFT) conversion.
F - Flight crew training and qualification
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Q
For
Category III, a minimum of two auto lands except that only one autoland is required when the flight simulator training has been carried out in a flight simulator qualified for zero flight time conversion… (see also (d) ii B
App 1 EU-OPS 1.450 for flight crew members who have completed a ZFT type rating conversion course)
5. Type and command experience
Before a pilot may be authorised to operate with Category II or III minima, that pilot must have gained sufficient flight
experience on the aeroplane type before being authorized to apply Category II or III operating minima under actual
conditions.
EASA requirements concerning flight experience can be summed up as follows: (cf. Appendix 1 to EU-OPS 1.450 (e))
Before commencing Category II or III operations, the following additional requirements are applicable to commanders, or pilots to whom conduct of the flight may be delegated, and who are new to the aeroplane type:
– 50 hours or 20 sectors on the type, including line flying under supervision; and
– 100 m must be added to the applicable Category II or Category III RVR minima until a total of 100 hours or
40 sectors, including LIFUS has been achieved on the type.
Those requirements may be reduced for flight crew members who have previously been qualified for Category II/
III operations with a Community operator or who have CAT II/III command experience. See details in Appendix 1
to EU-OPS 1.450 (e).
6. Recurrent training and checking
At fixed intervals, a recurrent training program should take place to ensure and maintain an adequate level of proficiency
for Low Visibility Operations qualified pilots.
In conjunction with the normal operator proficiency checks, a pilot’s knowledge and ability to perform the tasks associated with Low Visibility Operations must be demonstrated.
Under European regulation (cf. Appendix 1 to EU-OPS 1.450 (g)), the required number of approaches to be undertaken in the flight simulator within the validity period of the operators proficiency check (6 month) is to be a minimum
of two:
– one must be a landing at the lowest approved RVR;
– one may be substituted by an approach and landing in the aeroplane using approved Category II and III
procedures.
In addition, during the conduct of the operators proficiency check, one missed approach must be flown.
If the operator is authorised to conduct take-off with RVR less than 150 m, at least one LVTO to the lowest applicable
minima shall be flown during the conduct of the operators proficiency check.
Recency for LTVO and Category II/III based upon automatic approaches and/or auto-lands is maintained by recurrent
training and checking, as prescribed in this paragraph.
F - Flight crew training and qualification
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F. Flight crew training and qualification
7. The qualification process of flight crew
under EASA regulation: overview
Flight crew without
CAT II/III experience
Flight crew with CAT
II/III experience:
– with other operator &
– on different type
Flight crew with CAT
II/III experience:
– with other operator &
– same type of operation
on same type and
variant
Flight crew with CAT
II/III experience:
– with same operator
on different type or
variant
GROUND TRAINING
GROUND TRAINING
GROUND TRAINING
GROUND TRAINING
Full ground training
course
Abbreviated ground
training course
Abbreviated ground
training course
Abbreviated ground
training course
SIM. TRAINING
– Full Simulator training
course
– Simulator check
SIM. TRAINING
– Abbreviated simulator
training course
– Simulator check
SIM. TRAINING
– Full Simulator training
course
– Simulator check
LINE TRAINING
Manual CAT II : 3 landings (1 if training on ZFT simulator)
Autoland CAT III: 2 autoland (1 if training on ZFT simulator)
COMMANDER with
COMMANDER with
– 50h on type or
– 20 sectors
– 100h on type or
– 40 sectors
Qualification to CAT
II/III approaches with
RVR minima +100ft
SIM. TRAINING
– Abbreviated simulator training course
– Simulator check
Qualification for
LVTO with RVR
below 150m
FIRST OFFICER
QUALIFICATION FOR CAT II/III
APPROACHES to the lowest minima
F - Flight crew training and qualification
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G. Operator’s duties
G - Operator’s duties
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G. Operator’s duties
1. Establishing operating minima
1.1. General
Aerodrome operating minima are defined as the limits of usability of an aerodrome for either take-off or landing. They
are established in order to ensure a desired level of safety for aeroplane operations at an aerodrome by limiting these
operations in specified weather conditions.
It’s the operator’s responsibility to establish aerodrome operating minima for each aerodrome to be used in operations.
In determining the values of operating minima, the operator must take into account. (cf. ICAO Annex 6 § 4.2.7.2)
The type, performance and handling characteristics of the aeroplane;
Q
the
composition of the flight crew, their competence and experience;
Q
the
dimensions and characteristics of the runways which may be selected for use;
Q
the
adequacy and performance of the available visual and non-visual ground aids;
Q
the
equipment available on the aeroplane for the purpose of navigation and/or control of the flight path during
the approach to landing and the missed approach;
Q
the
obstacles in the approach and missed approach areas and the obstacle clearance altitude/height for the
instrument approach procedures;
Q
the
means used to determine and report meteorological conditions; and
Q
the
obstacles in the climb-out areas and necessary clearance margins.
Take-off operating minima are expressed in terms of RVR / visibility.
For low visibility approach, operating minima are expressed as an RVR associated to a DH.
DH is the minimum height in an approach by which a missed approach must be initiated if the required visual
reference to continue the approach has not been established. DH value is established taking into account:
– the characteristics of the aeroplane and its equipment (i.e. minimum DH specified in the AFM),
– obstacles in the approach and missed approach area (i.e. obstacle clearance height)
– the performance of the approach aid (ILS),
– the category of operations.
The RVR associated to a Decision Height is intended to provide a high probability that the required visual references will be available at that decision height.
The RVR is established taking into account:
– the DH value: As a general rule, the higher the aeroplane is at DH, the greater will the RVR required be (please
refer to Paragraph B.3.3, RVR use)
– the lighting system characteristics,
– the tasks the pilot is required to carry out at and below DA/H in order to complete the landing (manual landing
or monitoring of an autoland).
Nevertheless, aerodrome minima established in that way by the operator must not be lower than:
– minima that may be established by the State in which the aerodrome is located,
– DH and RVR minimum values imposed by the operator’s authority through a specific authorisation, or more
generally through the applicable operational regulation.
NOTE: Minima on their own have no intrinsic meaning; they only have significance in conjunction with a set of operating policies,
procedures and pilot training program. For this reason, the imposition of specific operating minima by the State of the Aerodrome
on operators from another State can lead to inconsistencies or be counter-productive.
For example, a European operator who has implemented low visibility operational procedures and a pilot training program, as described in Chapter E and F, can use the minimum DH and RVR required by EASA regulation, except if the
State of the aerodrome where operations take place has published higher minima.
G - Operator’s duties
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1.2. EASA take-off minima
Please refer to EU-OPS 1.430, Appendix 1 (a) - Take-off Minima
The take-off minima established by an operator must be expressed as RVR/Visibility values not lower than:
Take off RVR / visibility
RVR / visibility for ATR aircraft(1)
Facilities
Nil (day only)
500m
250m(2)
Runway edge lighting and/or centreline markings
Runway edge and centreline lighting
200m
150m(3)
Runway edge and centreline lighting and multiple RVR information
(1)
The reported RVR/Visibility value representative of the initial part of the take-off run can be replaced by pilot
assessment.
(2)
For night operations at least runway edge and runway end lights are required.
(3)
The required RVR value must be achieved for all of the relevant RVR reporting points with the exception
cited (1) above.
Subject to approval from the relevant Authority, and provided additional conditions are satisfied, the take-off minima
may be reduced to 125 m (please refer to Paragraph E.4.2, Low Visibility Take-Off under European regulation (EU-OPS) ).
1.3. EASA CAT II minima
Please refer to EU-OPS 1.430, Appendix 1 (a) - Take-off Minima
Q
The
Decision Height for CAT II operations must not be lower than:
– the minimum decision height specified in the AFM (100ft for all ATR series); or
– the minimum decision height to which the precision approach aid can be used without the required visual
reference; or
– the Obstacle Clearance Height (OCH- see paragraph D4) for the category of aeroplane; or
– the Decision Height to which the flight crew is authorised to operate; or
– 100ft (30m).
NOTE: CAT II approaches are “auto-coupled” approaches to below DH. The automatic flight control system must be used down to a height
which is not greater than 80% of the applicable DH. Thus airworthiness requirements may, through minimum engagement height for the
automatic flight control system, affect the DH to be applied. For ATR aircraft, as the minimum height for the use of autopilot in approach
mode is 80 ft (50ft for Aircraft with Mod 0069), there is no limitation for the use of a DH equals to 100ft.
Q
The
required RVR depends on the DH value as follows:
Decision height
RVR for Cat B aircraft (ATR)
100ft – 120ft
300m
121ft- 140ft
400m
141ft and above
450m
1.4. EASA CAT III minima
Please refer to EU-OPS 1.430, Appendix 1 (g) - Precision approach - Category III operations.
Q
The
Decision Height for CAT III operations must not be lower than:
– the minimum decision height specified in the AFM, (50ft for ATR -600); or
– the minimum height to which the precision approach aid can be used without the required visual reference; or
– the decision height to which the flight crew is authorised to operate.
Q
The
minimum RVR required for CAT IIIA approaches with a DH less than 100ft is 200m.
G - Operator’s duties
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G. Operator’s duties
1.5. EASA Lower than Standard CAT I minima
Please refer to EU-OPS 1.430, Appendix 1 (e) - Lower than Standard Category I operations
Q
The
Decision Height for lower than Standard CAT I operations must not be lower than:
– the minimum decision height specified in the AFM, if stated;
– the minimum height to which the precision approach aid can be used without the required visual reference; or
– the OCH for the category of aeroplane; or
– the decision height to which the flight crew is authorised to operate; or
– 200 ft.
Q
The
required RVR depends on the DH value as follows:
Class of lighting facility
DH (ft)
FALS
IALS
BALS
NALS
RVR/CMV(1) (metres)
(1)
200 - 210
400
500
600
750
211 - 220
450
550
650
800
221 - 230
500
600
700
900
231 - 240
500
650
750
1000
241 - 249
550
700
800
1100
CMV: Converted Meteorological Visibility (please refer to Paragraph B.3.5, Conversion of reported meteorological
visibility to RVR).
The visual aids required to conduct lower than Standard Category I Operations comprise:
– standard runway day markings and
– runway lighting (runway edge lights, threshold lights, runway end lights).
– approach lighting (for FALS, IALS, BALS and NALS definitions, please refer to Paragraph D.6.3) and,
– touch-down zone and/or runway centre line lights for operations below 450m.
1.6. EASA other than Standard CAT II minima
Please refer to EU-OPS 1.430, Appendix 1 (f) - Precision approach: Category II and other than Standard Category II
Q
The
DH is established as for Category II approaches (see here above)
Q
The
required RVR depends on the DH value as follows:
Class of lighting facility
DH (ft)
FALS
IALS
BALS
NALS
RVR (meters)
100 - 120
350
450
600
700
121 - 140
400
500
600
700
141 - 160
450
500
600
750
161 - 199
450
550
650
750
The visual aids required to conduct other than Standard Category II Operations comprise:
– standard runway day markings and
– runway lighting (runway edge lights, threshold lights, runway end lights).
– approach lighting ( for FALS, IALS, BALS and NALS definitions, please refer to Paragraph D.6.3) and
– centre line lights for operations in RVR of 400 m or less.
G - Operator’s duties
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1.7. Operating minima publication
For standard operations, a large number of operators decides to use operating minima published on Jeppesen approach charts. Minima published by Jeppesen are the minimum values allowed by the operational regulation prevailing
in the concerned region of the world.
Concerning Low Visibility Operations, Jeppesen documentation can also be used for Low Visibility Take-Off (please
refer to Paragraph E.4.2) and for CAT II approaches (see figure 56 here below). Concerning lower than Standard CAT I,
other than Standard CAT II and CAT III approaches, Jeppesen does not publish any operating minima. It is the operator
responsibility to publish minima for these operations.
Figure G1: Example of CAT II minima on a Jeppesen approach chart
2. Operations manual content
In their Operations Manual, operators must publish all relevant information, procedures and operating instructions
relating to Low Visibility Operations. Instructions must be compatible with the limitations and mandatory procedures
contained in the Aeroplane Flight Manual.
The implementation of Low Visibility Operations will generally affect different parts of the Operations manual, depending
on the general structure of the document.
Q
The
general/basic part which contains non type-related operational policies should include a chapter concerning Low Visibility Operations: this chapter should address the following matters:
– definition of Low Visibility Operations
(please refer to Paragraph A.5, Definitions),
– regulatory framework
(please refer to Paragraph A.4, Relevant regulations),
– general conditions on aircraft, crew and ground equipment
(please refer to Paragraph A.3, Low visibility operations (LVO) concept),
– rules for the determination and use of operating minima
(please refer to Paragraph G.1, Determination of operating minima),
– rules for the commencement and continuation of approach
(please refer to Paragraph E.6.2, Approach ban / RVR controlling),
– use of weather report and RVR controlling
(please refer to Paragraphs B.4, Weather Documentation and E.6.2, Approach ban / RVR controlling),
– minimum visual references
(please refer to Paragraph E.6.4, Normal procedures on classic instruments ATR for CAT II approaches),
– effects of ground equipment failure
(please refer to Paragraph E.8, Effects of ground equipment failure).
Q
The
section on the Aeroplane operating matters comprises all type-related instructions and procedures. It
should contain aircraft limitations plus detailed operating procedures which must include the description of flight
crew member duties during take-offs, approaches, flares, roll-outs and missed approaches. Special attention
must be paid to task sharing in conjunction with the workload of each crew member. Particular emphasis must
be placed on flight crew responsibilities during transition from non-visual conditions to visual conditions, and
on the procedures to be used in deteriorating visibility conditions or when failures occur. The given instructions depend on which airborne equipment is used and on which flight deck procedures are being followed
(please refer to Chapter E, Flight crew operating procedures).
G - Operator’s duties
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G. Operator’s duties
Q
The
Training part should describe in detail the flight crew training and qualification process and the recurrent
training and checking program
(please refer to Chapter F, Flight Crew Training and qualification).
For European operators, Appendix 1 to EU-OPS 1.455 (b) lists the different items to be covered by the operations
manual:
(i) checks for the satisfactory functioning of the aeroplane equipment, both before departure and in flight
(please refer to § C3, E2, E5)
(ii) effect on minima caused by changes in the status of the ground installations and airborne equipment
(please refer to § C3, C.4, E8)
(iii) procedures for the take-off, approach, flare, landing, roll-out and missed approach
(please refer to § E3, E4, E5, E6)
(iv) procedures to be followed in the event of failures, warnings and other non-normal situations
(please refer to § E7)
(v) the minimum visual reference required
(please refer to § E.6.4);
(vi) the importance of correct seating and eye position
(please refer to § E.5.7);
(vii) action which may be necessary arising from a deterioration of the visual reference
(please refer to § E.6.5);
(viii) allocation of crew duties in the carrying out of the procedures according to subparagraphs (i) to (iv) and
(vi) above, to allow the Commander to devote himself/herself mainly to supervision and decision making
(please refer to § E.6.3);
(ix) the requirement for all height calls below 200 ft to be based on the radio altimeter and for one pilot to
continue to monitor the aeroplane instruments until the landing is completed
(please refer to § E.6.1);
(x) the requirement for the Localizer Sensitive Area to be protected
(please refer to § D.5.4 & E.5.1);
(xi) the use of information relating to wind velocity, wind shear, turbulence, runway contamination and use of
multiple RVR assessments
(please refer to § B.2, B.3, B.4, E.5.1, E.6.2);
(xii) procedures to be used for:
(A) lower than Standard Category I;
(B) other than Standard Category II;
(C) practice approaches and landing on runways at which the full Category II or Category III aerodrome
procedures are not in force
(please refer to § E.6);
(xiii) operating limitations resulting from airworthiness certification and
(please refer to § C.1, C.2)
(xiv) information on the maximum deviation allowed from the ILS glide path and/or localizer
(please refer to § E.7.5).
3. Operational demonstration
3.1. General
Operational regulation (cf. AC 120-29A / AC 120-28D §10.5 and Appendix 1 to EU-OPS 1.440) compel operators to carry
out an operational demonstration before being authorised to perform CAT II/III approaches.
The aircraft system suitability is demonstrated through the initial airworthiness demonstration. The aim of the operational demonstration is not to repeat the flight test program performed for the CAT II/III airworthiness approval. It is to
determine or validate the use and effectiveness of the aircraft flight guidance systems, training, flight crew procedures,
maintenance program, and manuals applicable to the program being approved.
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In practice the operational demonstration consists in performing a number of approaches in CAT I or better weather
conditions using Category II/III systems and procedures. Such demonstration may be conducted in line operations,
during training flights or during aircraft type or route proving runs. The flight crew involved in this demonstration must
have completed his low visibility ground and simulator training. Approaches and landings performed during this demonstration must be recorded through a data collection method (e.g. a form to be used by the flight crew) to establish
that performances and reliability in line service are suitable.
EU-OPS 1.440 - Appendix 1: Low visibility operations — General operating rules
AC 120-28 and -29 Paragraph 10.5.2 – “Operator Use Suitability” Demonstration
If an operator has different variants of the same type of aircraft utilising the same basic flight control and display
systems, or different basic flight control and display systems on the same type of aircraft, the operator must [FAA:
shoud] show that the various variants have satisfactory performance, but the operator need not conduct a full
operational demonstration for each variant.
3.2. Operational demonstration under European regulation
The EU regulation (cf. Appendix 1 to EU-OPS 1.440 b) requests that for CAT II/III operations with a DH of 50ft or higher,
at least 30 approaches and landings be accomplished in operations to validate the operational demonstration.
A reduction in the required number of landings may be considered on a case-by-case basis if justification is provided
to the authority.
If the number of unsuccessful approaches exceeds 5% of the total (e.g. unsatisfactory landings, system disconnects)
the evaluation program must be extended in steps of at least 10 approaches and landings until the overall failure rate
does not exceed 5%. Unsatisfactory approaches and/or automatic landings shall be documented and analysed. The
resulting data and a summary of the demonstration data should be made available to the operational Authority.
Data Collection for Operational Demonstrations
IEM Appendix 1 to EU-OPS 1.440
Data should be collected whenever an approach and landing is attempted utilising the Category II/III system,
regardless of whether the approach is abandoned, unsatisfactory, or is concluded successfully. Not more than
30% of the demonstration flights should be made on the same runway.
The data should, as a minimum, include the following information:
– Inability to initiate an Approach: Identify deficiencies related to airborne equipment which preclude initiation
of a Category II/III approach.
– Abandoned Approaches: Give the reasons and altitude above the runway at which approach was
discontinued or the automatic landing system was disengaged.
– Touchdown performance: Describe whether or not the aircraft landed satisfactorily (within the desired
touchdown area) with lateral velocity or cross track error which could be corrected by the pilot or automatic
system so as to remain within the lateral confines of the runway without unusual pilot skill or technique.
The approximate lateral and longitudinal position of the actual touchdown point in relation to the runway
centreline and the runway threshold, respectively, should be indicated in the report. This report should also
include any Category II/III system abnormalities which required manual intervention by the pilot to ensure a
safe touchdown.
Unsuccessful approaches due to the following factors may be excluded from the analysis:
– ATS Factors: Examples include situations in which a flight is vectored too close to the final approach fix/
point for adequate localiser and glide slope capture, lack of protection of ILS sensitive areas, or ATS
requests the flight to discontinue the approach.
– Faulty Navaid Signals: Navaid (e.g. ILS localiser) irregularities, such as those caused by other aircraft taxiing,
over-flying the navaid (antenna).
– Other Factors. Any other specific factors that could affect the success of Category II/ III operations that are
clearly discernible to the flight crew should be reported.
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G. Operator’s duties
EASA definition of a successful approach
IEM Appendix 1 to EU-OPS 1.440
• From 500 feet to start of flare:
– Speed is maintained as specified in AMC-AWO 231§ 2 (speed control); and
– No relevant system failure occurs; and
• From 300 feet to DH:
– No excess deviation occurs; and
– No centralised warning gives a go-around command (if installed).
EASA definition of a successful automatic landing
IEM Appendix 1 to EU-OPS 1.440
No relevant system failure occurs;
No flare failure occurs;
No de-crab failure occurs (if installed);
Longitudinal touchdown is beyond a point on the runway 60 meters after the threshold and before the end
of the touchdown zone lighting (900 meters from the threshold);
– Lateral touchdown with the outboard landing gear is not outside the touchdown zone lighting edge;
– Sink rate is not excessive;
– Bank angle does not exceed a bank angle limit; and
– No roll-out failure or deviation (if installed) occurs.
(More details can be found in CS-AWO 131, CS-AWO 231 and AMC-AWO 231)
–
–
–
–
3.3. Operational demonstration under FAA regulation
The FAA regulation on operational demonstration is quite similar. The main difference concerns the number of approaches and landing to be carried out. At least 100 successful landings are required for the demonstration. Nevertheless a reduction in the required number of landings may be accepted by the authority on a case-by-case basis.
AC 120-28 and -29 Paragraph 10.5.2 – “Operator Use Suitability” Demonstration.
At least one-hundred (100) successful landings should be accomplished in line operations using the low visibility
landing system installed in each aircraft type applicable to the Category II/ III authorisation. Demonstrations may
be conducted in line operations, during training flights, or during aircraft type or route proving runs.
4. Eligible aerodromes and runways
Operators must assess airports and runways eligible to perform Category III approaches. The purpose of this assessment is to check the compatibility between airborne and ground facilities to perform successful autoland.
For Category II approaches such assessment is limited to specific situation in particular where the pre-threshold terrain profile may affect the conduct of the approach (please refer to Paragraph D.3. Effects of pre-threshold terrain profile).
EU-OPS 1.440 - Appendix 1: Low visibility operations — General operating rules
(h) Eligible aerodromes and runways
1. Each aeroplane type/runway combination must be verified by the successful completion of at least one
approach and landing in Category II or better conditions, prior to commencing Category III operations.
2. For runways with irregular pre-threshold terrain or other foreseeable or known deficiencies, each aeroplane
type/runway combination must be verified by operations in Standard Category I or better conditions, prior to
commencing Lower than Standard Category I, Category II, or other than Standard Category II or Category III
operations.
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5. Continuous monitoring
After obtaining the authorisation to perform low visibility approaches, the operator must monitor the overall safety of
those operations and monitor the automatic landing system performance of each aeroplane.
The reporting of satisfactory and unsatisfactory Category II/III aircraft performance is a tool to detect any decrease in
the level of safety before it becomes hazardous. Flight crew reports may be used to achieve this.
If the analysis of those reports shows that conditions exist which could adversely affect safe Low Visibility Operations,
the operator is expected to take appropriate corrective actions. Examples of appropriate corrective action could be an
adjustment of Category II/III programs, procedures, training, modification to aircraft, restriction of minima, limitations on
winds, restriction of NAVAID facility use, adjustment of payload, service bulletin incorporation, or other such measures
necessary to ensure safe operation.
Reported data and their analysis must be retained for a period of 12 months. It must include at least: (cf. Appendix 1 to
EU-OPS 1.440(e))
Q
the
total number of approaches, by aeroplane type, where the airborne Category II or III equipment was utilized
to make satisfactory, actual or practice, approaches to the applicable Category II or III minima; and
Q
reports
of unsatisfactory approaches and/or automatic landings, by aerodrome and aeroplane registration, in
the following categories:
– airborne equipment faults;
– ground facility difficulties;
– missed approaches because of ATC instructions; or
– other reasons.
Such system for recording approach and/or automatic landing success and failure is requested by European regulation
for Category II, other than Standard Category II, and Category III operations.
6. Operator approval process
The approval process may differ according to the various regulations but the general principle consists in providing an
operational approval file to the National Authority and in performing a specific sequence of actions in agreement with
the Authority.
Under European regulation, an operator cannot perform the following Low Visibility Operations unless approved by the
Authority:
– Low Visibility Take-Offs in less than 150m RVR;
– Lower than Standard Category I approaches;
– Other than Standard Category II approaches;
– CAT II and CAT III approaches.
6.1. Prerequisite / transitional period
The national Authority may request that an operator has operated an aeroplane type for a said-minimum period before
granting an LVO approval.
For instance, under EASA regulation, an operator must have gained a minimum experience of 6 months of Category I
operations on the aeroplane type before being authorised to perform CAT II or CAT III approaches. Nevertheless an
operator with previous CAT II/III experience (on another aeroplane type) may obtain authorisation for a reduced transition period.
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G. Operator’s duties
6.2. Operational approval file
The operational approval file represents the official application for Low Visibility Operations. The aim of this file is to
demonstrate to the authority that arrangements made by the operator comply with the relevant operational regulation
on Low Visibility Operations.
Basically, this file should include the following items.
Q
General
Presentation of the type of operations submitted to approbation (Category of approach, LVTO, special operations...), timetable for the implementation of LVO, previous experience with other aircraft type, lowest values of
the operating minima established for the different categories of operations…
Q
Aircraft
status
Extracts from the Aircraft Flight Manual addressing certification status for Low Visibility Operations, associated
limitations, list of required equipment for the intended operations, normal procedures and procedures following
failures. For ATR aircraft this information is provided in part 3 of the AFM.
Q
Operating
procedures
Copy of the amendment to the Operations manual covering Low visibility operations.
Information and procedures to be introduced into the operation manual by an operator who intends to perform
LVO are set out in paragraph G.2, Operations manual content. Details of operating procedures are addressed
in Chapter E, Flight crew operating procedures.
Q
Flight
crew training and qualification
– Description of the flight crew training and qualification process according to the pilot’s previous experience
(ground, simulator and line training, command experience, checking) including the process to qualify instructors.
– Description of the recurrent training and checking.
(please refer to Chapter F, Flight crew training and qualification)
Q
Maintenance
program
Description of the maintenance program, which is mandatory to ensure the airborne equipment will remain at
the level of performance and reliability demonstrated during the certification
(please refer to Paragraph C.5, Maintenance).
Q
Aerodromes
List of aerodromes (if requested by the Authority) where the operator intends to perform Low Visibility Operations and demonstration that those aerodromes are eligible to such operations.
(please refer to Paragraph G.4, Eligible aerodromes and runways)
Q
Operational
demonstration
Presentation of the operational demonstration that the operator intends to perform including the data collection
and analysis process.
(please refer to Paragraph G.3, Operational demonstration)
Q
Continuous
monitoring
Description of procedures set up by the operator to monitor LVO performances after having obtained the initial
authorisation.
(please refer to Paragraph G.5, Continuous monitoring)
6.3. Sequencing of action during the approval process
1) The first step consists in obtaining acceptance of the file described here above by the National Authority. This may
require several corrections or amendments involving multiple back and forth stage between the Authority and the
operator.
2) As soon as the operating procedures, the training and qualification programmes are accepted by the Authority,
ground and simulator training can be initiated. Some Authorities may request to supervise the first simulator sessions
and/or the training and checking of instructors.
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3) Line training is initiated with flight crew members having completed their ground and simulator training. When approaches performed for line training are recorded they may be taken into account for the operational demonstration.
4) As and When:
– the transitional period
(please refer to Paragraph G.6.1, Prerequisite / transitional period) is over and
– the operational demonstration
(please refer to Paragraph G.3, Operational demonstration) is completed with satisfactory results and
– the amendment to the operating manual covering Low Visibility Operations is effective,
the National Authority should grant authorisation to perform LVOs
5) Low Visibility Operations can be initiated by the operator to the lowest minima with the possible limitation associated
to the “type and command experience” (please refer to Paragraph F.5, Type and command experience) and to conditions on “eligible aerodromes and runways” (please refer to Paragraph G.4, Eligible aerodrome and runways).
6) Actions concerning the continuous monitoring must become effective.
(please refer to Paragraph G.5, Continuous monitoring).
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Abbreviations
ADU
Autopilot Display Unit
AFCS
Automatic Flight Control System
AGL
Above Ground Level
AHRS
Attitude & Heading Reference System
AP
Auto Pilot
ATC
Air Traffic Control
AWO
All Weather Operations
BALS
Basic Approach Light System
CRM
Collision Risk Model
CS
Certification Specifications
CM1
Left-seated Crew Member
CM2
Right-seated Crew Member
CMV
Converted Meteological Visibility
DH
Decision Height
EADI
Electronic Attitude Display Indicator
EASA
European Aviation Safety Agency
FAA
Federal Aviation Administration
FALS
Full Approach Light System
FD
Flight Director
GLS
GNSS Landing System
G/S
Glide Slope
HUDLS
Head-Up Display Landing System
IALS
Intermediate Approach Light System
ICAO
International Civil Aviation Organisation
ILS
Instrument Landing System
LOC
Localizer
LVO
Low Visibility Operations
LVP
Low Visibility Procedures
LVTO
Low Visibility Take-Off
METAR
Meteo Airport Report
MLS
Microwaves Landing System
NALS
No Approach Light System
OAS
Obstacle Assessment Surfaces
OCH
Obstacle Clearance Height
OFZ
Obstacle Free Zone
OLS
Obstacle Limitation Surfaces
OM
Outer Marker
PF
Pilot Flying
PNF
Pilot Non Flying
RA
Radio Altimeter
RVR
Runway Visual Range
SVR
Slant Visual Range
TAF
Terminal Aerodrome Forecast
TDZ
Touch Down Zone
Abbreviations
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Dear Readers,
Every effort has been made to ensure document quality. However please
do not hesitate to share your comments and information with us by using
the following address: flight-ops-support@atr.fr
We would also like to thank ENAC (Ecole Nationale de l’Aviation Civile) for
its involvement in the development of this guide.
Yours faithfully,
Printed on 100% recycled paper using vegetable inks
Your ATR Training and Flight Operations support team.
© ATC June 2010
All reasonable care has been taken by ATC to ensure the accuracy of the present document.
However this document does not constitute any contractual commitment from the part of ATC which will offer, on request,
any further information on the content of this brochure. Information in this brochure is the property of ATC and will be treated
as confidential. No use or reproduction or release to a third part may be made there of other than as expressely authorised by ATC.
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