Automatic Direction Finder · Like RDF units, most ADF ... -The loop antenna sense the direction of...
Transcript of Automatic Direction Finder · Like RDF units, most ADF ... -The loop antenna sense the direction of...
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COMSOFT
COMSOFT GmbH | AMHS/AIS Qatar | April 2008
Automatic Direction Finder
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
HOW DO I GET FROM HERE TO THERE?
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
Automatic Direction Finder
What is Automatic Direction Finder?
Automatic Direction Finder is navigational instrument use to point in
the direction of whatever station you tune-in that automatically and
continuously displays the relative bearing from the ship or aircraft to a
suitable radio station.
It is used as a means of identifying positions, receiving low and medium
frequency voice communications, homing, tracking, and for navigation
on instrument approach procedures.
ADF receivers are normally tuned to aviation or marine NDBs operating
in the LW band between 190 – 535 kHz. Like RDF units, most ADF
receivers can also receive medium wave (AM) broadcast stations.
The low/medium frequency navigation stations used by ADF include
non-directional beacons, ILS radio beacon locators, and commercial
broadcast stations.
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
ADF COMPONENTS
ADF Receiver
- pilot can tune the station desired and to select the mode of operation.
- The signal is received, amplified, and converted to audible voice or morse
code transmission and powers the bearing indicator.
Control Box (Digital Readout Type)
- the frequency tuned is displayed as digital readout.
- ADF automatically determines bearing to selected station and it on the RMI
- .
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
ADF COMPONENTS
Antenna
- The aircraft consist of two antennas
- LOOP antenna and SENSE antenna
- The ADF receives signals on both loop and sense antennas
- The loop antenna sense the direction of the station by the strength
of the signal on each coil but cannot determine whether the
bearing is TO or FROM the station.
Bearing Indicator
- displays the bearing to station relative to the nose of the aircraft.
- Relative Bearing
- Magnetic Bearing
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
Non-directional Beacon
Ground equipment consists of a simple a.m. radio station
The NDB is the station on the ground that emits the signal that the ADF
tunes to. Its signal is emitted in all directions so it doesn’t matter where the aircraft's position is relative to the station, the ADF will still pick up
its signal.
the ADF always points to the NDB station.
NDBs may be located on the surface of airports, or may be within a few
miles from an airport. Sometimes they are co-located with the Outer
Marker in ILS approaches.
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
TYPE OF ADF INDICATOR
Fixed Compass Card
- It is fixed to the face of instrument and cannot rotate. 0 degree is
always straight up as the nose of aircraft.
Rotatable Compass Card
- The dial face of the instrument can be rotated by a knob
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
TYPE OF ADF INDICATOR
Single-Needle Radio Magnetic Indicator
- Radio Magnetic Indicator is an instrument that combines radio and
magnetic information to provide continuous heading , bearing ,
and radial information.
Dual-Needle Radio Magnetic Indicator
- the dual needle RMI is similar to single needle RMI except that it
has a second needle.
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
OPERATION of ADF
ADF operate in the low and medium frequency bands.
By tuning to NDB station or commercial AM radio stations.
NDB frequency and identification information may be obtained from
aeronautical charts and Airport Facility Directory.
The ADF has automatic direction seeking qualities which result in the
bearing indicator always pointing to the station to which it is tuned.
The easiest and perhaps the most common method of using ADF , is to
" home " to the station .
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
Purpose of ADF
The ADF may be in its design and function it is used by the pilot in flight for at
least five different purposes:
1. Position Fixing i.e. determining the aircraft's position
2. Enroute navigation
3. Instrument approaches
4. Holding
5. Indication on the commencement point of a more sophisticated instrument
approach
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
LIMITATIONS AND BENEFITS
Radio waves reflected by the ionosphere return to the earth 30 to 60
miles from the station and may cause the ADF pointer to fluctuate.
Mountains or cliffs can reflect radio waves, producing a terrain effect.
Shorelines can refract or bend low frequency radio waves as they pass
from land to water.
electrical storm is nearby, the ADF needle points to the source of lightning rather than to the selected station because the lighting sends
out radio waves.
The ADF is used for primary navigation over long distances in remote
areas.
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
Quiz
1. Define ADF? Answer. Automatic direction finder
2-3. What are the two common use of ADF? Answer. Homing to a station and Tracking from a station
4-7. What are the components of ADF?
Answer. ADF receiver, control box, antenna, bearing indicator
8. What is the allocated range frequencey band for ADF receiver?
Answer. 190-1750 Khz
9. Which of the following factors could cause an error of an ADF bearing of an NDB?
Answer. Night effect
a. Atmospheric scatter b. Phase interference
c. Night effect
d. None of the above
10. What gives the greatest error in ADF? Answer. Static interference from thunderstorms
COMSOFT GmbH | AMHS/AIM Qatar | April 2008
Assignment
What is ADF system?
The ADF/NDB navigation system is one of the oldest air
navigation systems still in use today. It works from the most simple radio
navigation concept: a ground-based radio transmitter (the NDB) sends an
omnidirectional signal that an aircraft loop antenna receives. The result is a
cockpit instrument (the ADF) that displays the aircraft position relative to an NDB station, allowing a pilot to "home" to a station or track a course
from a station.