Avionics MCQs – Fly-by-Light Flight Control
1 - Question
Which of the following affects the Fly-By-Wire system?
b) Lightning strikes
c) Flying in powerful Radio/Radar region
d) Bad weather
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
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
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
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
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.
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
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.
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
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
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.