AERODROME TRAINING COURSE
– MODULE 4
Control of Obstacles
CONTROL OF OBSTACLES
Learning Outcome
On completion of this module students will be able to explain the
requirements for controlling obstacles to facilitate an airport
operation.
They will be able to:
• Explain the basic requirements and inter-relationship between :Obstacle Limitation - Obstacle Assessment - Obstacle Protection Surfaces
• With access to reference material detail the specific dimensions
of an Airports Obstacle Limitation Surfaces
Obstacle Limitation Surfaces (ANNEX 14)
Obstacle Assessment Surfaces (PANS OPS Doc 8168)
•
ANNEX 14 Obstacle Limitation Surfaces
The broad purpose of these surfaces is to define the volume of airspace
around aerodromes to be maintained free from obstacles so as to permit
the intended aeroplane operations at the aerodrome to be conducted safely
and to prevent the aerodromes from becoming unusable by the growth of
obstacles. This is achieved by establishing a series of OLS that define the
limits to which objects may project into the airspace
•
PANS OPS Obstacle Assessment Surfaces
These surfaces are intended for use by procedure designers for the
construction of instrument flight procedures and for specifying minimum
safe altitudes/heights for each segment of the procedure
•
ANNEX 14
Annex 14 Obstacle Limitation Surfaces
•Transitional Surfaces
•Inner Horizontal
•Conical
•Outer Horizontal
•Approach
•Take-off climb
•Balked Landing (Precision)
•Obstacle Free Zone (Precision Cat 2 & 3)
•
PANS OPS DOC 8168
Obstacle Assessment Surfaces
Annex 14 Obstacle Protection Surface
•
for VASIS/PAPI
•
•
•
Instrument Approach Surfaces
Circling
Departure Surfaces
ANNEX 14 OLS
Purple –Inner Horizontal, conical, Outer horizontal
Obstacle Limitation
Surfaces
Green Approach
Red Take-off climb
OBSTACLE LIMITATION SURFACES
OLS DIMENSIONS
Annex 14 Transition OLS
Transition OLS
Annex 14 Approach Surface
Annex 14 Approach Surface
Annex 14 Transition and Approach Surfaces
Inner Horizontal surface 4000m
radius from Reference Point
45m above a runway elevation
datum
Refer AerodromeServices Manual Part 6
Where surfaces overlap the lower surface
should be regarded as dominant
Conical surface from Horizontal
surface 45m at slope of 5% to 100m
Inner Horizontal and Conical
Annex 14 Take-off Surfaces
Code 3 & 4
6480m
60m from Runway End*
*The take-off climb surface starts at the end of the clearway if the clearway
length exceeds the specified distance. Refer Annex 14 Table 4-2
Annex 14 Take-off 1.6%
*The take-off climb surface starts at the end of the clearway if the clearway
length exceeds the specified distance. Refer Annex 14 Table 4-2
Annex 14 Take-off 2.0%
ANNEX 14
Obstacle Free Zone
Obstacle Free Zone
•
•
Reference:
Obstacle Free Zone is established for Precision
Category I (recommended), II, III operations
Inner approach, Inner Transitional and Balked Landing surfaces
create the Obstacle Free Zone for precision approach operations
Description of ANNEX 14 4-3
Doc 9137 Part 6
Obstacle Free Zone
ANNEX 14
Obstacle Protection
Surface
ANNEX 14
Figure 5 -20
Obstacle protection surface for visual approach slope indicator system
ANNEX 14
Figure 5 -20
Dimensions and slopes of the obstacle protection surfaces
PANS OPS
SURFACES
OCA/H for Visual manoeuvring (Circling)
Aircraft
Category
A
B
C
D
E
PANS OPS 8168
Circling Area
Radius from Thres
(R)
3.12
4.90
7.85
9.79
12.82
Obstacle clearance
m
90
90
120
120
150
Lowest OCH above Aerodrome
120(394ft)
150(492ft)
180(591ft)
210(689ft)
240(787ft)
PANS OPS 8168
VOR Approach surfaces
Relationship between different surfaces
1 in 7 Side Transition, Inner Horizontal and Conical,
Annex 14 Approach, VOR Approach
PANS OPS 8168
Basic ILS obstacle assessment surfaces

ILS Collision Risk Model
Visual Segment Surface
•All new straight-in instrument approach procedures published on or after
15 March 2007 shall be protected for obstacles in the visual segment.
Straight-in instrument approach procedures published before 15 March
2007 shall be protected in the visual segment by means of the VSS after
the periodical review of the procedure, but not later than 15 March 2012.
Dimensions
a base width of 300 m (150 m either side of the extended runway
centreline) for a Code 3 and 4 runway and 150 m (75 m either side of the
extended runway centreline) for Code 1 and 2, originating 60 m prior to
the runway threshold, splaying 15 per cent on either side of the extended
runway centreline, and terminating at the point where the height of the
surface reaches the OCH
where the final approach course is offset and intersects the extended
runway centreline, the splay on the side closest to the final approach
course is increased by the offset angle. Vertically, the VSS originates at
the runway threshold height and has a slope of 1.12 degrees less than the
promulgated approach procedure angle
Departure 2.5% Obstacle assessment surface
to protect aircraft climbing at 3.3%
PANS OPS 8168
Departure Surface
Annex 14 Take-off surfaces with
PANS OPS 8168 Departure Surface
3D view of Take-off OLS Annex 14 surface
showing penetration of terrain
OLS Existing with structures included
3D modelling used to highlite proposed structures (RED) are below proposed raised
OLS (yellow) but existing structures (BLUE) penetrate this surface
Initial Approach surfaces
Intermediate Approach surfaces
VOR/DME approach surface showing Nil penetration
of obstacles
PRACTICAL EXERCISES
1.
Calculate the height that an obstacle can be
erected above an instrument runway precision
Code 4 given: on extended centreline distance
from threshold 4000m?
2.
What OLS will control the height of an obstacle
to be erected adjacent to midpoint of a Code 4
instrument runway at 320m for runway
centreline?