Avionics MCQs – Fly-by-Light Flight Control

1 - Question

Which of the following affects the Fly-By-Wire system?
a) EMI
b) Lightning strikes
c) Flying in powerful Radio/Radar region
d) Bad weather
View Answer Answer: d
Explanation: One of the common modes of failure in the Fly-By-Wire system is EMI. Since the whole aircraft runs on electricity, Electromagnetic Interference heavily affects the FBW system. It is caused by lightning strikes and in regions of high power radio or radar.

2 - Question

What is EMP?
a) Electromagnetic pulse
b) Electromagnetic Power
c) Electromagnetic protection
d) Electrically Matched power line
View Answer Answer: a
Explanation: An EMP, abbreviated as Electromagnetic pulse is a sudden change in the magnitude of an electrical field(a pulse) with strengths of hundreds of volts per meter. It occurs in a very wide range of electromagnetic radiation spectrum and can damage any electrical equipment in its vicinity.

3 - Question

What is EMC?
a) Electromagnetic capture
b) Electromagnetic compatibility
c) Electromagnetic combat
d) Electromagnetic course
View Answer Answer: b
Explanation: EMC or Electromagnetic compatibility is the ability of the aircraft equipment to withstand high levels of EMI. This is a necessary condition as many cases have occurred of aircraft experiencing severe transients in the automatic flight control system placing the aircraft temporarily out of control whilst overflying high power radar/radio transmitters. This has been due to the susceptibility of the flight control system analogue electronics to EMI because of inadequate electro-magnetic screening.

4 - Question

What is nuclear hardness?
a) Ability to survive a nuclear explosion
b) Ability to survive in the vicinity of nuclear explosion
c) Ability to defend nuclear weapons
d) Ability to drop nuclear weapons with precision
View Answer Answer: b
Explanation: Vicinity to a nuclear explosion and consequent emission of gamma radiation and an EMP of very high electric field strength. Military avionic equipment is specially designed to survive up to a certain (classified) level of these effects. This attribute is referred to as ‘nuclear hardness’ and is achieved by the design of the circuits, use of nuclear hard components, circumvention techniques and very efficient electromagnetic screening.

5 - Question

Where is an EMC vault used?
a) Housing of FBW computer
b) Housing of all electronics
c) Screened enclosure around the connector
d) Shield for wires
View Answer Answer: c
Explanation: The wires from the cable connectors and the EM filters are housed within a screened enclosure around the connector known as an ‘EMC vault’ so that there is no aperture for EMI radiation to enter the box. The wires connecting different electrical equipment are the most affected by EMI.

6 - Question

Fiber optic cables are used in aircraft only for faster data transmission.
a) True
b) False
View Answer Answer: b
Explanation: In addition to high data rates in the optical transmission medium, another important advantage is its ability to survive EMI. Fiber optics have very less interference by EMI and are used in aircraft mainly for this reason.

7 - Question

Which one of the following is false with respect to fiber optic cables?
a) High speed
b) Heavy compared to normal wires
c) Less EM interference
d) Costly
View Answer Answer: b
Explanation: Fiber optics weigh comparatively very low than normal wires. Wires require shielding from EMI which also adds up to the overall weight of the connectivity system. They also offer high speed data transfer and are relatively costly.

8 - Question

Optical fiber is an insulator.
a) True
b) False
View Answer Answer: a
Explanation: Fiber optic cables carries a digitally modulated light intensity signal. IT has no necessity to be made of an conductor as the only condition for light to pass through is an opaque medium. Optical fibers are always made with an insulating material as they offer less EMI.

9 - Question

What type of multiplexing is used in optical fiber lines?
a) Time division multiplexing
b) Code division multiplexing
c) Frequency division multiplexing
d) wavelength division multiplexing
View Answer Answer: d
Explanation: Fibre optic data transmission use ‘wavelength division’ multiplexing whereby a single fibre can be used to transmit several channels of information as coded light pulses of different wavelengths (or colours) simultaneously. The individual data channels are then recovered from the optically mixed data by passing the light signal through wavelength selective passive optical filters which are tuned to the respective wavelengths. WDM has a very high integrity as the multiplexed channels are effectively optically isolated.

10 - Question

Where was the first Fly-By-Light system used?
a) Fighter aircraft
b) Bomber Aircraft
c) Airships
d) Spacecrafts
View Answer Answer: c
Explanation: Non-rigid airships may be acquiring a new lease of life as long duration platforms for airborne radar surveillance systems. The airship is able to carry a large high power radar antenna within its envelope and is able to remain airborne for several days. Since the antenna could severely interfere with FBW systems FBL system was used.

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