DMEs

Question 1

Echo Protection Circuit

Answer 1

Prevent errors arising from reflection from earth surface - installed on ac receiver to protect

Question 2

DME operate in what frequency band

Answer 2

960-1215 MHz
Space waves
Decimetric

Question 3

DME work by

Answer 3

Providing slant ranges - measures time interval between transmission from interrogator in ac to reply from transponder on the ground.

Slant range by pulse technique

Question 4

Interrogator unit back to the transponder delay

Answer 4

50 microsecond delay

Question 5

Jittering

Answer 5

Interrogation pulse randomised so identification can be made between ac and DME ground responder

Question 6

Frequency used for receiving and transmission

Answer 6

1 for transmission/ 1 for receiving
UHF/VHF prevent own transmission being locked onto
+- 63MHz transponder reply frequency

Question 7

What prevent DME receiver from locking onto other transmissions

Answer 7

Because time intervals between pulse pairs are unique to the AC

Question 8

3 types of DME

Answer 8

DME normal
DME precision
Terminal DME - distance to define point on runway

Question 9

Search Mode

Answer 9

150 pulses pairs per second for 100 seconds
60 pulse pairs per second after

Question 10

Tracking Mode

Answer 10

27 pulse pairs per second after locking on
If signal lost due to masking of antenna will move back to search mode

Question 11

Masking Mode

Answer 11

10 seconds after signal lost
Goes back to search mode

Question 12

Beacon saturation

Answer 12

Ground transponder limited capacity to random jitters
2700 pulse pairs per seconds
100 aircraft limit
DME will respond to 100 strongest signals

Question 13

Station identification

Answer 13

Beacon transmit 3 letter call sign every 40 seconds at a different frequency

Question 14

Military TACAN

Answer 14

Able to be utilised for DME distance only

Question 15

Slant Range Error when descending

Answer 15

Slant error reduces more accurate

Question 16

Slant range error climbing

Answer 16

Slant error increases - less accurate

Question 17

Slant range error - flying abeam

Answer 17

Groundspeed will be zero

Question 18

VOR Speed measurement accuracy - flying away on radial/flying overhead/flying on radial different heading

Answer 18

Flying away/towards VOR on radial:
GS accurate more when flying away on radial

Flying overhead:
Groundspeed is zero

Flying on the radial:
Groundspeed less accurate/less value

Question 19

Terminal VOR/DME

Answer 19

30NM max distance

Question 20

En-route VOR/DME

Answer 20

Co-located 600nm

Question 21

Theta Rho

Answer 21

VOR/DME

Theta = bearing
Rho = Range

Question 22

Rho Rho

Answer 22

DME DME
Rho = Range

Question 23

Theta Theta

Answer 23

VOR/VOR
Theta = Bearing (Angle)

Question 24

VOR and DME is identified by

Answer 24

VOR/ILS is transmitted 3 times for every DME ident
DME has a higher tone frequency

Question 25

What does it mean when the DME display counter rotates throughout there range

Answer 25

Airborne receiver is conducting a range search

Indicator rotate rapidly from zero nm through to max range

Question 26

DME operates in and uses how many frequency’s?

Answer 26

UHF band and uses two frequencies

Question 27

How many channels in DME

Answer 27

126

Question 28

DME are more accurate the

Answer 28

Further away you get

Question 29

Ident co located with a VOR time intervals

Answer 29

VOR = 3x per 40 second cycle
DME = 1x per 40 second cycle

10 sec intervals between ident codes (first three VOR/ILS and 4th DME (higher pitch)

Question 30

Two DME ranges plotted on chart used to fix aircraft position what would be indicated on the chart?

Answer 30

Two circular position lines intersecting at two points, the distance from each transmitter being the slant range

Question 31

What is a DME Line of position

Answer 31

A circle/arc with the DME transponder at the centre and the radius formed by the DME range

Question 32

Accuracy of DME

Answer 32

0.2nm