Vayudoot Aviation

1. Which of the following will give the most accurate calculation of aircraft ground speed?

A DME station sited on the flight route

A DME station sited across the flight route

A VOR station sited on the flight route

2. No. of a/c required to saturate DME beacon are

126

127

100

3. The OFF flag on aircraft DME mileage displays indicate

any of the below; B or C.

DME is tuned to the wrong frequency.

the DME is off.

4. An aircraft receives a reply pulse from a DME 1200 µ sec after transmission of the interrogation pulse. The DME has a fixed delay of 50 microsec) The range of the aircraft from the DME station is

45 nm

93 nm

75 nm

5. The range indicated by DME is considered to be accurate to within

1.25 % of range ± 0.25 nm.

3% of range.

0.2 nm.

6. Max no of a/c that can use a DME stn are

127

100

126

7. A VOR and DME are co-located. You want to identify the DME by listening to the Call sign. Having heard the same call sign 4 times in 30 seconds the

VOR and DME call signs were the same and broadcast with the same pitch

DME call sign was not transmitted, the distance information is sufficient proof of correct operation

DME call sign is the one with the higher pitch that was broadcast only once

8. An aircraft DME receiver rejects pulses meant for other aircraft because

the pulses are unique to each aircraft.

the random PRF is unique to each aircraft.

the transmission and reply frequencies are 63 MHz apart.

9. What is the slant range error for an aircraft flying at 9000 feet absolute altitude above a DME located at elevation 2000 ft, when the slant range is 12 NM?

0.9 NM.

0.31 NM.

1.42 NM.

10. During a flight at FL210, a pilot does not receive any DME distance indication from a DME station located approximately 220NM away. The reason for this that the

Aero plane is below the "line of sight" altitude

Altitude is too high

Aero plane is circling around the station

11. Airborne DME equipment is able to discriminate between pulses intended for it self and pulses intended for other aircraft because

aircraft will only accept unique twin pulses.

each aircraft has its own frequency allocation.

aircraft reject pulses not synchronised with its own random pulse recurrence rate.

12. The DME (Distance Measuring Equipment) operates within the following frequencles

962 to 1213kHz

329 to 335MHz

962 to 1213MHz

13. The DME automatic standby will activate the DME interrogator when

a VOR frequency that has a frequency paired DME is selected.

the DME ident signal is received.

there are too many aircraft in the area for it to service.

14. If a VOR station and a DME station, having different locations, are selected to provide a fix

two sets, with separate frequency control, are required in the aircraft.

all 2 answers below are correct.

two different IDs will have to be checked

15. Referring to DME during the initial stage of the search pattern before lock-on

the aircraft transmits 24 pulses per second and the receiver checks a maximum of 150 pulses per second.

the airborne transmitter transmits 150 pulses each second.

the ground receiver maintains the ground transmitter pulse transmission rate at no more than 150 per second.

16. The aircraft DME receiver cannot lock on to interrogation signals reflected from the ground because

reflections are subject to Doppler frequency shift

aircraft transmitter and DME ground station are transmitted on different frequencies

DME pulse recurrent rates are varied

17. A DME station is located 1000ft above MSL. An aircraft flying at FL 370, 15NM away from the DME station, will have a DME reading of

15NM

14NM

16NM

18. A letter Z at the end of identification code means

DME and VOR are co-located and are serving same stn.

DME and VOR are not co-located, are serving same stn. are within 7 nm from each other.

DME and VOR are not co-located but serving same stn and at a dist of more than 7 nm

19. When a DME is used insted of marker beacons to provide range to the threshold on an ILS approach and where the DME frequency is paired with the ILS, the DME indications should not be used at altitudes greater than

25,000 ft

6,000 ft

3,000 ft

20. The time taken for the transmission of an interrogation pulse by a Distance Measuring Equipment (DME) to travel to the ground transponder and return to the airborne receiver was 2000micro-second. The slant range from the ground transponder was

186NM

296NM

165NM

21. What is the maximum distance between VOR and DME / TACAN ground installations if they are to have same morse code identifier?

300m

600m

2000m

22. On a DME, display counters rotating throughout their range indicates

airborne equipment failure

the airborne receiver is conducting a range search

the airborne equipment is conducting a frequency search

23. Ground Speed indications when using a DME will be retiable / accurate when a/c is flying

towards / away from ground stn

a/c is flying at height less than 1000' per nm

a/c is flying 90° to ground stn (max error)

24. A DME receiver is able to distinguish between replies to its own interrogation pulses and those intended for other aircraft using the same transponder because

when DME is in the range search mode it will accept only pluses separated by + or - 63 MHz from the interrogation frequency.

each aircraft transmits pulses at a random rate (jittering) and will only accept replies that match this randomisation.

DME is a secondary radar and each aircraft transmits and receives on a different frequency.

25. When an altimeter is used for SSR is always referenced to

1013.25 hPa

QFE

The pressure setting in use

26. For a conventional DME facility "Beacon Saturation" will occur whenever the number of simultaneous interrogations exceeds

60

100

200

27. The airborne DME equipment will transmit pulse pairs at a comparatively high PRF

When first switched on and after a channel selection

At all times, except when the panel control LO is operated.

Whenever a stable signal is being received from the selected ground station

28. DME is a (i) radar operating in the (ii) band and transmits (iii)

(i) secondary; (ii) SHF; (iii) 2400 pulse pairs per second

(i) primary; (ii) SHF; (iii) CW pulses

(i) secondary; (ii) UHF; (iii) pulse pairs

29. Groundspeed measurement using DME equipment is most accurate flying

from the station at long range.

past the station at short range.

towards the station at short range.

30. An a/c is flying at a height of 20,000 ft over a DME stn it will show

Appx 6 km

2,000'

Zero.

31. An aircraft will not accept replies from its own transmissions that are reflected from the ground because the

the aircraft's registration is embedded onto the signal.

pulses are transmitted in pairs.

interrogation and reply frequencies are 63 Mhz apart.

32. Distance Measuring Equipment (DME) operates in the

UHF band and is a secondary radar system

SHF band and uses frequency modulation techniques

UHF band and is a primary radar system

33. A DME that has difficulty obtaining a "lock-on":(NOTE : PRE = pulse recurrence frequency, PPS = pulse per second)

stays in search mode but reduces PRF to max, 60PPS after 1500 pulse pairs have been transmitted

stays in search mode but reduces PRF to max. 60PPS after 100 seconds.

stays in search mode but without a reduction in PRF

34. A VOR/DME share the same first two letters of their respective identifiers; the last identifying letter of the DME is a Z. This means that

they are widely separated and do not serve the same location.

they are more than 600m apart but serve the same location.

they are a maximum distance of 30m apart.

35. DME and VOR are frequency paired because

both ground transmitter aerials can be placed on the same site if required.

the same receiver can be used for both aids.

cockpit workload is reduced.

36. In which situation will speed indications on a airborne Distance Measuring Equipment (DME) most closely represent the groundspeed of an aircraft flying at FL 400?

When tracking directly towards the station at a range of 100NM or more

When overhead the station, with no change of heading at transit

When passing abeam the station and within 5NM of it

37. A DME is located at MSL. AN aircraft passing vertically the station at FL360 will obtain a DME range of approximately

8NM

6NM

7NM

38. An a/c DME shows 50 nm, accuracy of indicated distance will be

0.625 nm ±0.25nm

0.15 nm ±0.5 nm

0.5 nm±

39. A DME receiver does not lock on to its own transmitter because of

Transmitter and receiver are working at different frequency.

It works on the principle of random PRF

DME is free from ground clutter.

40. If an ident signal is received once in 30 seconds on a frequency paired VOR/DME, then:

the VOR only is operational.

the DME only is operational

the TACAN signal is degraded.

41. An aircraft flying at flight level 250 wishes to interrogate a DME beacon situated 400 ft above man sea level. What is the maximum range likely to be achieved?

222 nm.

210 nm.

198 nm.

42. Mode 'C' or mode 'S' of SSR is not to be used when indication differ more than

±200'

±100'

None of the above

43. The accuracy of a DME

is approximately +-2 nm.

is approximately +-0.5 nm.

decreases with increase of range

44. Of what use, if any, is a military TACAN station to civil aviation?

It is of no use to civil aviation

It can provide DME distance

It can provide a magnetic bearing

45. A DME in tracking mode subsequently experiences a reduction in signal strength will switch the equipment in the first instance to

memory mode

signal controlled search

standby mode

Question Bank

Questions for R* B*LI RADAR