This set of Aircraft Maintenance Multiple Choice Questions & Answers (MCQs) focuses on “Aviation Communication Systems – DME-1”.
1. What is the full form of DME?
a) Distance measuring equipment
b) Distance maintaining equipment
c) Data measuring equipment
d) Data maintaining equipment
Explanation: DME refers to distance measuring equipment. It is a radio navigation technology that measures the distance between an aircraft and a ground station.
2. The propagation delay of DME radio signals in the frequency band is timed between ___________
a) 960 Hz and 1215 Hz
b) 960 MHz and 1215 MHz
c) 96 MHz and 121 MHz
d) 96 Hz and 121 Hz
Explanation: The propagation delay of DME radio signals in the frequency band is timed between 960 MHz and 1215 MHz. Line of visibility between the aircraft and the ground station is necessary.
3. Which of the following specifies the carrier frequency and the spacing between the pulses?
a) Pitch assignment
b) Amplitude assignment
c) Channel assignment
d) Frequency assignment
Explanation: The channel assignment specifies the carrier frequency and the spacing between the pulses. These are two essential operating values of the DME.
4. Which of the following is not an agency that sets standards for DME systems?
Explanation: Rolls-Royce is not an agency that sets standards for DME systems. However, RTCA, EASA and ICAO are all agencies that set standards for DME systems.
5. ICAO characterizes DME transmissions as ___________
a) High frequency
b) Ultra high frequency
c) Low frequency
d) Medium frequency
Explanation: ICAO characterizes DME transmissions as UHF or ultra high frequency. This is because of the relatively high frequency of such transmissions in comparison to other transmissions. It may also be described by the term L-band.
6. Where was the DME developed?
Explanation: The DME instrument was developed in Australia. It was invented by James Gerrand, under the supervision of Edward George Bowen. Germany is another country having significant contributions to the aerospace industry. Airbus has a major facility at Hamburg, Germany. India and Canada also have a fair share of Aerospace Business.
7. DME is functionally identical to the distance measuring component of ___________
Explanation: The DME is functionally identical to the distance measuring component of TACAN. This is done to maintain compatibility between the two systems.
8. What is the typical peak pulse output of a DME ground transponder for en-route or terminal navigation?
a) 100 kW
b) 10 kW
c) 1 kW
d) 1000 kW
Explanation: The typical peak pulse output of a DME ground transponder for en-route or terminal navigation is 1 kW, on the assigned UHF channel.
9. How much is the typical time delay after which the aircraft interrogates with the ground transponder?
a) 50 microseconds
b) 50 seconds
c) 50 minutes
d) 50 milliseconds
Explanation: 50 microseconds is the typical time delay after which the aircraft interrogates with the ground transponder. The process involves a series of pulse-pairs (interrogations).
10. The DME system comprises a UHF interrogator in the aircraft.
Explanation: True, The DME system comprises a UHF interrogator in the aircraft. This interrogator may also be referred to as a receiver or transmitter and is necessary to interpret the incoming UHF transmission signals.
11. How much time does a radio signal take, to travel 1 nautical mile to the target and back?
a) 12.36 nanoseconds
b) 12.36 seconds
c) 12.36 microseconds
d) 12.36 milliseconds
Explanation: 12.36 microseconds is the time taken by a radio signal to travel 1 nautical mile to the target and back. The distance is approximately 1,852 meters.
12. How much is the accuracy of DME ground stations?
a) 1.85 m
b) 185 m
c) 18.5 m
d) 0.185 m
Explanation: 185 m is the accuracy of DME ground stations. It may vary by ±0.1 nautical mile. ICAO recommends an accuracy of less than the sum of 0.25 nautical miles.
13. An aircraft directly above the DME station at 1 nautical mile altitude would show ___________ on the DME readout.
a) 100 nautical mile
b) 10 nautical mile
c) 0 nautical mile
d) 1.0 nautical mile
Explanation: An aircraft directly above the DME station at 1 nautical mile altitude would show, 1.0 nautical mile on the DME readout. This indicates the aircraft is technically a mile away, just a mile straight up.
Sanfoundry Global Education & Learning Series – Aircraft Maintenance.
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