by
JOY N. HERMOSILLA, PECE # 00203
Air Navigation System Specialist
Manila Approach Radar
Civil Aviation Authority of the Philippines
Air Navigational Tools
 Objectives:
 To learn the basics of electronic Air Navigational tools.
 To learn its purpose.
 To learn on the future of electronic Navigational tools.
Air Navigational Tools
 Introduction
 Electronic navigational tools were used to determine
the position of an aircraft relative to a fixed position on
the ground.
 Pilots can navigate by using rate and time relationship.
Air Navigational Tools
 Three Methods of Navigation
1. Rho Theta – measuring distance and bearing information.
North
θ
ρ
Air Navigational Tools
2. Rho Rho Rho – measuring 3 distance information.
ρ1
ρ3
ρ2
Air Navigational Tools
3. Theta Theta Navigation – measuring bearings to two
or more ground stations.
North
θ1
θ3
θ2
Instrument Landing System (ILS)
 Assist the pilot in positioning the aircraft for landing
under low visibility conditions.
 A VHF/UHF radio navigational aid that provide two
radio beams which can be used as an ideal flight path.
 Two transmitters are located at the runway:
 Localizer – Provides azimuth.
 Glide Slope – Provides elevation information.
 Both transmitters radiates two electromagnetic energy
patterns that overlaps one another.
Instrument Landing System (ILS)
•The emission patterns of
the localizer and glide
slope signals
 The narrow area of overlap
defines the ideal flight
path by providing:
 Azimuth
 Approximate range
 Elevation reference
 Localizer frequency range:
108-112MHz
 Spaced at 50KHz with fc of
odd frequencies.
Instrument Landing System (ILS)
 Glide Slope frequency range: 328 – 336MHz
 Localizer and Glide Slope frequencies are paired.
 At the cockpit, the pilot sets the Localizer frequency
and the system will automatically set the Glide Slope.
 Front Course Approach – the combination of Localizer
and Glide Slope.
 Fly to the needle.
 At the back course, Glide slope is absent.
 Fly away from the needle.
MARKER BEACON
 Outer Marker- a transmitter antenna located about
6miles from the end of the runway that gives distance
information.
 Transmits vertical cone (elliptical) signal at 75MHz.
 The modulation is repeated Morse-style dashes of a
400 Hz tone.
 The cockpit indicator is a blue lamp that flashes in
unison with the received audio code.
MARKER BEACON
 Middle Marker – located 3500ft away from the
threshold.
 It is modulated with a 1.3 kHz tone as alternating Morse-
style dots and dashes at the rate of two per second.
 The cockpit indicator is an amber lamp that flashes in
unison with the received audio code.
 Inner Marker - Ideally at a distance of approximately
1,000 ft (300 m) from the threshold.
 The modulation is Morse-style dots at 3 kHz.
 The cockpit indicator is a white lamp that flashes in
unison with the received audio code.
MARKER BEACON
Instrument Landing System (ILS)
Instrument Landing System (ILS)
Mixer
RF
IF
Audio
Det.
90Hz
Filter
150Hz
Filter
Flag
Loc.
OSC
Deviation
MICROWAVE LANDING SYSTEM
 MLS employs 5GHz transmitters at the landing place
which use passive electronically scanned arrays to send
scanning beams towards approaching aircraft. An
aircraft that enters the scanned volume uses a special
receiver that calculates its position by measuring the
arrival times of the beams.
 Is an all-weather, precision landing system originally
intended to replace or supplement the Instrument
Landing System (ILS).
 A wide selection of channels to avoid interference with
other nearby airports (200 channels).
 Excellent performance in all weather.
 A small "footprint" at the airports.
MICROWAVE LANDING SYSTEM
• MLS used a single
frequency, broadcasting
the azimuth and altitude
information one after the
other.
MICROWAVE LANDING SYSTEM
 The system may be divided into five functions:
 Approach azimuth
 Back azimuth
 Approach elevation
 Range
 Data communications
 Approach azimuth guidance - The azimuth station
transmits MLS angle and data on one of 200 channels
within the frequency range of 5031 to 5091 MHz and is
normally located about 1,000 feet (300 m) beyond the stop
end of the runway.
MICROWAVE LANDING SYSTEM
 The azimuth coverage:
 Laterally,
at least 40
degrees on either side of the
runway centerline in a
standard configuration.
 In elevation, up to an angle
of 15 degrees and to at least
20,000 feet (6 km), and in
range, to at least 20 nautical
miles (37 km).
MICROWAVE LANDING SYSTEM
 Elevation guidance
 The
elevation station
transmits signals on the
same frequency as the
azimuth station.
 Located about 400 feet
from the side of the
runway between runway
threshold
and
the
touchdown zone.
MICROWAVE LANDING SYSTEM
 Range guidance
 The MLS Precision Distance Measuring Equipment
(DME/P) functions the same as the navigation DME, but
there are some technical differences.
 The beacon transponder operates in the frequency band
962 to 1105 MHz and responds to an aircraft interrogator.
 The MLS DME/P accuracy is improved to be consistent
with the accuracy provided by the MLS azimuth and
elevation stations.
 A DME/P channel is paired with the azimuth and
elevation channel.
MICROWAVE LANDING SYSTEM
 Data communications
 The data transmission can include both the basic and
auxiliary data words.
 All MLS facilities transmit basic data.
 Where needed, auxiliary data can be transmitted.
 MLS data are transmitted throughout the azimuth (and
back azimuth when provided) coverage sectors.
 Representative data include:
 Station identification, Exact locations of azimuth,
elevation and DME/P stations, Ground equipment
performance level, DME/P channel and status.
MICROWAVE LANDING SYSTEM
 Auxiliary data content:
 3-D locations of MLS
equipment.
 Waypoint coordinates.
 Runway conditions and
Weather etc.
VHF OMNIDIRECTIONAL RANGE
 Is a type of radio navigation system for aircraft.
 A VOR ground station broadcasts a VHF radio
composite signal including the station's identifier in
Morse code (and sometimes a voice identifier).
 The data allows the airborne receiving equipment to
derive a magnetic bearing from the station to the
aircraft.
 The intersection of two radials from different VOR
stations on a chart allows for a "fix" or approximate
position of the aircraft.
VHF OMNIDIRECTIONAL RANGE
VHF OMNIDIRECTIONAL RANGE
VHF OMNIDIRECTIONAL RANGE
 An aircraft could follow a specific path from station to
station by tuning the successive stations on the VOR
receiver.
 Then either following the desired course on a Radio
Magnetic Indicator, or setting it on a Course Deviation
Indicator (CDI) or a Horizontal Situation Indicator
(HSI, a more sophisticated version of the VOR
indicator) and keeping a course pointer centered on
the display.
VHF OMNIDIRECTIONAL RANGE
 VORs are assigned radio channels between 108.0 MHz
and 117.95 MHz (with 50 kHz spacing); this is in the
VHF range.
 The VOR uses the phase relationship between a
reference-phase and a rotating-phase signal to encode
direction.
 The carrier signal is Omni-directional and contains an
amplitude modulated (AM) station Morse code or
voice identifier.
 The reference 30 Hz signal is frequency modulated on
a 9960 Hz sub-carrier.
VHF OMNIDIRECTIONAL RANGE
VHF OMNIDIRECTIONAL RANGE
 A second, amplitude modulated (AM) 30 Hz signal is
derived from the rotation of a directional antenna
array 30 times per second.
 Although older antennas were mechanically rotated,
current installations scan electronically to achieve an
equivalent result with no moving parts.
 When the signal is received in the aircraft, the two
30 Hz signals are detected and then compared to
determine the phase angle between them.
 The phase angle is equal to the direction from the
station to the aircraft, in degrees from local magnetic
north, and is called the "radial."
VHF OMNIDIRECTIONAL RANGE
 OBS
– Omni Bearing
Selector.
 In the illustration on the
right, notice that the
heading ring is set with 360
degrees (North) at the
primary index.
 The needle is centered and
the To/From indicator is
showing "TO".
VHF OMNIDIRECTIONAL RANGE
 In many cases the VOR stations have co-located DME
(Distance Measuring Equipment) or military TACAN
(TACtical Air Navigation).
 A VOR radial with DME distance allows a one-station
position fix.
 VORTACs and VOR-DMEs use a standardized scheme
of VOR frequency.
DISTANCE MEASURING EQUIPMENT
 Distance
measuring equipment (DME) is a
transponder-based radio navigation technology that
measures distance by timing the propagation delay of
VHF or UHF radio signals (Int:1025 to 1150 MHz,
Xponder: Tx,962 to 1150 MHz; Rx, 962 to 1213 MHz).
 Aircraft use DME to determine their distance from a
land-based transponder by sending and receiving
pulse pairs - two pulses of fixed duration and
separation.
 DME is similar to Secondary Surveillance Radar (SSR),
except in reverse.
 DME can be co-located with VOR, ILS, or MLS.
DISTANCE MEASURING EQUIPMENT
 The
DME system is composed of a UHF
transmitter/receiver (interrogator) in the aircraft and a
UHF receiver/transmitter (transponder) on the
ground.
 The aircraft interrogates the ground transponder with
a series of pulse-pairs (interrogations).
 The ground station replies with an identical sequence
of reply pulse-pairs with a precise time delay (typically
50 microseconds).
 The DME receiver in the aircraft searches for pulsepairs (X-mode= 12 microsecond spacing) with the
correct time interval between them.
DISTANCE MEASURING EQUIPMENT
 The correct time between pulse pairs is determined by
each individual aircraft's particular interrogation
pattern.
 The aircraft interrogator locks on to the DME ground
station once it understands that the particular pulse
sequence is the interrogation sequence it sent out
originally.
 Once the receiver is locked on, it has a narrower
window in which to look for the echoes and can retain
lock.
DISTANCE MEASURING
EQUIPMENT
 Slant Distance – is the
measured distance
between DME
transponder station and
aircraft interrogator.
 Slant Distance =
(Ttot-50μsec)/2(12.36), NM
 Accuracy : ±0.1NM,
about ± 185m.
Surveillance System
 Primary Surveillance Radar (PSR)
 The radar transmitter sends out a pulse of radio energy,
of which a very small proportion is reflected from the
target aircraft back to the radar receiver.
 The orientation of the radar antenna provides the
bearing of the aircraft from the ground station.
 The time taken for the pulse to reach the target and
return provides a measure of the distance of the target
from the ground station.
 The bearing and distance of the target then displayed to
the Air Traffic Controller.
Surveillance System
Surveillance System
Surveillance System
 Secondary Surveillance Radar (SSR)
 The purpose of this system is to improve the ability to
detect and identify aircraft while it additionally provides
automatically the Flight Level (pressure altitude) of a
flight.
 An SSR continuously transmits interrogation pulses as
its antenna rotates, or is electronically scanned in space.
 A transponder on an aircraft that is within line-of-sight
'listens' for the SSR interrogation signal and sends back
a reply that provides aircraft information.
 The reply sent depends on the mode that was
interrogated.
Surveillance System
 Secondary Surveillance Radar (SSR)
 The aircraft is then displayed as a tagged icon on the
controller's radar screen at the calculated bearing and
range.
 An aircraft without an operating transponder still may
be observed by primary radar, but would be displayed to
the controller without the benefit of SSR derived data.
 A cross-band beacon is used, which simply means that
the interrogation pulses are at one frequency (1030
MHz) and the reply pulses are at a different frequency
(1090 MHz).
Surveillance System
 Secondary Surveillance Radar (SSR)
 The SSR interrogation format (sometimes called
uplink format) is very simple.
 Consisting of two pulses (P1 and P3) of 0.8 µs width
which are separated by a certain time – that
determines the mode of interrogation.
 P2 is used for side lobe suppression.
Surveillance System
T
P1
P3
P2
Surveillance System
 Military Mode 1: T=3(±0.2)μsec.
 used to support 32 military identification codes
(although 4096 ‘mode 1’ codes could also be used).
 Normally, the 32 codes could be used to indicate role /
mission / type.
 However, this mode itself is not in common use in a
normal peacetime environment.
 Military Mode 2: T=5(±0.2)μsec.
 provides 4096 ID codes for military use (as for mode A).
 Normally used to identify an individual aircraft airframe.
Surveillance System
 Military Mode 3/ Civil Mode A: T=8(±0.2)μsec.
 Provides 4096 ID codes for civil / military use. Normally,
the 32 codes could be used to indicate role / mission /
type.
 The commonly used mode.
 Civil Mode B: T=17(±0.2)μsec.
 Originally defined but never been used.
 Civil Mode C: T=21(±0.2)μsec.
 Pressure Altitude Extraction.
Surveillance System
 Civil Mode D: T=25(±0.2)μsec.
 Not Used.
 Mode S: Selective Unique Interrogation.
 providing an individual address capability (24-bit
addresses are allocated to every airframe by their
registering authority).
 Increase in data integrity by the use of a parity check
mechanism.
Surveillance System
Surveillance System
Side Lobe Suppression
P2 comparison
Future of Air Navigation System
 Communication Improvements
 This involved a transition from voice communications to
digital communications.
 Aircraft Communications Addressing and Reporting
System (ACARS) is the medium used.
 An application was hosted on the airplane known as
Controller Pilot Data Link Communication (CPDLC).
Future of Air Navigation System
 Navigation Improvements
 This involves a transition from Inertial Navigation to
Satellite Navigation using the GPS satellites and WAAS.
 Surveillance Improvements
 This involves the transition from voice reports (based on
inertial position) to automatic digital reports.
 FANS procedural control
 The improvements to CNS allow new procedures which
reduce the separation standards for FANS controlled
airspace.