Radio Navigation Aids

Question 1

VHF Omni Range (VOR)

Answer 1

Uses the concept of phase differential
Transmits a 30 Hz reference and a 30 Hz variable-phase signal
Receiver compared these and finds the radial from the station

Question 2

VOR Errors

Answer 2

Airborne Equipment (receiver error +/- 2)
Vertical Polarisation (antenna is banked out of the horizontal plane)
Ground Station (transmission equipment +/- 2)
Aggregate (total of all errors +/- 5)
Site/terrain effect (bending or scalloping of signals due obstacles close to the site +/- 2)

Question 3

Magnetic Variation Application VOR

Answer 3

Applied at the transmitter (calibrated)

Question 4

Doppler VOR

Answer 4

Almost eliminated site effect by using FM

Question 5

NDB/ADF

Answer 5

Uses ground waves
NDB radiates a non-directional signal in MF band (<200nm)
2 antennae, 1 loop giving the null position and 1 sense solving the 180 degree ambiguity

Question 6

Locators

Answer 6

NDB with less power

Question 7

Errors NDB/ADF

Answer 7

Mountain effect (reflected signals from mountains/hills)
Interference (co-channel, from other NBB’s which increases at night)
Night effect (sky wave interference)
Terrain effect (signals attenuated over non conductive surfaces)
Costal refraction (bent towards land as they cross the coast)
Height effect (decreased range at decreased altitude over non conductive surfaces)
Aircraft (signal bending due aircraft interference)
Thunderstorms

Question 8

DME

Answer 8

UHF
Automatically tuned to VOR frequency
Ground transponder and aircraft transmit pulses to compute a distance
Uses actual distance (slant range) to station

Question 9

Ground Speed DME Error

Answer 9

Ground speed readout will decrease at a;increasing rate when overflying an aid due to slant range error increasing
Will reach 0 as the aircraft passes directly overhead the aid
If not flying directly to station, ground speed will be erroneously decreasing and time to station increasing.

Question 10

Limitations of DME

Answer 10

Line of sight only
Will only respond to the strongest signals when lots of traffic which decreases the range

Question 11

SSR (Secondary Surveillance Error]

Answer 11

Ground based interrogator transmits requesting all transponders to respond
Can show altitude as well as range and azimuth
~110nm range

Question 12

ILS

Answer 12

Localiser in the same band as VOR
Consists of two transmitters, 1 at 90 Hz and 1 at 150 Hz
Transmitters aligned for equal strength on the wry extended centreline

Question 13

3 Components of the ILS

Answer 13

Localiser
Glideslope
Marker Beacons

Question 14

ILS Full Scale Deflection of CDI

Answer 14

2.5 degrees off centreline

Question 15

Localiser Range

Answer 15

25nm within +/- 10 degrees of the CDI + 2000ft

Question 16

Localiser False Indications

Answer 16

Outside sector 35 degrees either side of the localiser

Question 17

Glideslope

Answer 17

Provides a 3 degree slope to the 1000ft markers
Pass threshold at 50ft

Question 18

Glideslope Full Scale Deflection

Answer 18

0.7 degrees above or below