DISTANCE MEASURING EQUIPMENT (DME)

Question 1

1. Airborne DME equipment is able to discriminate between pulses intended for itself and pulses intended for other aircraft because:

Answer 1

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

Question 2

2. A DME beacon having a transmit frequency of 962 MHz would have a receive frequency of:

Answer 2

1025 Mhz

Question 3

3. 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:

Answer 3

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

Question 4

4. Distance Measuring Equipment is an example of …………… radar operating on a frequency of …………… in the ……………. band.

Answer 4

secondary 962 MHz UHF

Question 5

5. A DME transponder does not respond to pulses received from radars other than DME because:

Answer 5

it will only accept the unique twin DME pulses

Question 6

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

Answer 6

+/-0.25 nm +/-1.25% of range

Question 7

7. A DME receiver is able to distinguish between replies to its own interrogations and replies to other aircraft because:

Answer 7

Each aircraft transmits pulses at a random rate and will only accept synchronised replies

Question 8

8. When a DME transponder becomes saturated:

Answer 8

it increases the receiver threshold to remove weaker signals

Question 9

9. An aircraft flying at FL250 wishes to interrogate a DME beacon situated 400 ft amsl. What is the maximum range likely to be achieved?

Answer 9

222 nm

Question 10

10. For a DME and a VOR to be said to be associated it is necessary for:

Answer 10

the aerial separation not to exceed 100 ft in a TMA or 2,000 ft outside a TMA

Question 11

11. The transmission frequency of a DME beacon is 63 MHz removed from the aircraft interrogator frequency to prevent:

Answer 11

the airborne receiver locking on to primary returns from its own transmissions

Question 12

12. The accuracy associated with DME is:

Answer 12

+/-0.25 nm +/-1.25% of range

Question 13

13. For a VOR and a DME beacon to be said to be associated the aerial separation must not exceed …………… in a terminal area and ……………. outside a terminal area.

Answer 13

30m 600m

Question 14

14. DME is a …………… radar operating in the …………… band and uses ……………. in order to obtain range information. The correct words to complete the above statement are:

Answer 14

secondary UHF twin pulses

Question 15

15. The receiver of airborne DME equipment is able to “lock on” to its own “reply pulses” because:

Answer 15

the aircraft receiver only accepts reply pulses which have the same time interval between successive pulses as the pulses being transmitted by its own transmitter

Question 16

18. DME operates in the …………… frequency band, it transmits …………… which give it the emission designator of ……………

Answer 16

UHF twin pulses P0N

Question 17

19. Referring to DME during the initial stage of the “search” pattern before “lock-on”:

Answer 17

the airborne transmitter transmits 150 pulses each second

Question 18

20. DME and VOR are “frequency paired” because:

Answer 18

cockpit workload is reduced

Question 19

21. 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:

Answer 19

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