What is the main electronic nav aid in use today?
What frequency does the VOR operate on?
Two signals are transmitted for a 360 degree signal with a phase difference.
When are the two signals “in phase”
What are the signals called that VORs transmit?
Each dot in the VOR receiver is how many degrees?
What does a VOR receiver do if no signal is being received?
A flag is displayed
What are the advantages for VOR?
- not effected by weather
- Accurate radials
- two VORS can provide a fix
- Accurate instrument approaches
What are the disadvantages of VOR?
Range limited line of site
What is a TACAN?
Military version of VOR/DME
What is the frequency band of TACAN?
What are the hurts of the two components of TACAN?
What are TACANs co-located with?
What are TACAN/VOR known as?
If the antenna of a TACAN fails what signal can’t be used?
In the VORTAC which part performs the function of a DME?
No need for a separate, co-located DME
Because the rotation of the antenna creates a large portion of the azimuth signal, if the antenna fails, the azimuth component is no longer available and the TACAN downgrades to?
A DME only Mode
How does the DME operate?
By transmitting and receiving paired pulses from the Ground station
The transmitter in the aircraft sends out very narrow pulses at a frequency of about?
What frequency does DME operate in?
UHF wave band
How accurate is DME?
What error does DME suffer from?
15nm DME can no longer be used
Why are DMEs in two frequencies for interrogator and transponder?
To avoid a/c interrogating each other
How does a DME work?
- Interrogator transmits
- Transponder replies
- computer works out range from elapsed time between signals
- Indicator shows range on digital or linear display
The antenna used for transmission and reception is a?
Small shark fin mounted on the underside of the aircraft.
Modern DME receivers incorporate digital readout of frequency, Distance from DME station and can automatically calculate the aircraft’s groundspeed. True or False?
A DME displays?
Slant range in nautical miles
What are the advantages of DME?
- VOR/DME installation can be used to make an IAP
- Simple to use/ calculate groundspeed
- Obtain a fix from 2 DMEs
What are the disadvantages of the DME ?
Only gives slant range
Not accurate at high altitudes over DME station
What is ILS?
A precision runway approach that provides accurate guidance in both azimuth and elevation.
Why does the ILS consist of?
A localiser Transmitter
Marker beacons or NDB
Approach lighting system
Where is the localiser situated?
Upwind of the runway 300m for the threshold.
Where is the glidepath situated?
300m for the landing threshold and offset 100-200m form the centre line.
How far are the
What frequency does the localiser transmit on?
What is the range of coverage for a localiser?
35 degrees either side up to 17nm and 10 degrees either side up to 25nm
What frequency does the Glide path operate on?
What is the coverage of the Glide path?
Horizontally 8 degrees either side of the centre line for 10nm and below 0.45xGP and 1.75xGP above.
List the different ILS categories
- Lower than standard Cat 1
-Other than standard CAT2
What are are the minimum heights/ visibility for CAT 1?
Vis not less than 800m
RVR not less than 550m
What are are the minimum heights/ visibility for lower than standard CAT 1?
What are are the minimum heights/ visibility for CAT 2?
What are are the minimum heights/ visibility for other than CAT 2?
Used if some/ all Precision approach lights are out.
What are are the minimum heights/ visibility for CAT 3A?
What are are the minimum heights/ visibility for CAT 3B?
What are are the minimum heights/ visibility for CAT 3C?
What does the localiser do?
Provides lateral guidance
What does the glidepath do?
Provides vertical guidance to the pilot during landing
What are the advantages of ILS?
1) Pilot interpreted and easy to use
2) Precision approaches possible
3) can be couples to auto-pilot for automatic approach and landings
What are the disadvantages of ILS?
Subject to interference from local VHF stations
Reflections from other ground facilities can cause false glide paths
Shortage of frequencies
What does MLS stand for?
Microwave Landing System
How does MLS work?
Uses passive arrays to send scanning beams towards aircraft.
Aircraft uses a receiver to calculate its position by measuring the arrival time s of beams.
Provides azimuth, elevation, and distance as well as back azimuth, from missed approach
What is the MLS coverage?
60 degrees either side of centre line to 14 nm
40 degrees either side of centre line to 20nm
What is the max vertical
Coverage of MLS?
30 degrees maximum limit