1. Fiber optic cables are used in aircraft only for faster data transmission.
a) True
b) False
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.
2. 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
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.
3. Optical fiber is an insulator.
a) True
b) False
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.
4. 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.
5. Where was the first Fly-By-Light system used?
a) Fighter aircraft
b) Bomber Aircraft
c) Airships
d) Spacecrafts
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.
6. What is ILS?
a) Instrument landing system
b) Indian Levitation System
c) Indian Landing system
d) International Levitation system
Explanation: ILS or instrument landing system is a radio based approach guidance system installed at major airports and airfields where the runway length exceeds 1800 m which provides guidance in poor visibility conditions during the approach to the runway.
7. Which one of the following can provide a reliable and accurate approach path guidance in category II visibility conditions?
a) ILS
b) MLS
c) SBAS
d) VHF
Explanation: SBAS or Satellite Based Augmentation Systems exploiting differential GPS techniques will be able to provide reliable and accurate approach path guidance in category II visibility conditions. This will be increasingly used in the future.
8. What are the two main components of an ILS on the ground?
a) Horizontal alignment transmitter and vertical alignment transmitter
b) Localizer transmitter and glide slope transmitter
c) Center line transmitter and glide slope transmitter
d) Center line transmitter and approach slope transmitter
Explanation: ILS system basically comprises a localiser transmitter and a glide slope transmitter located by the airport runway together with two or three radio marker beacons located at set distances along the approach to the runway. The airborne equipment in the aircraft comprises receivers and antennas for the localiser, glide slope and marker transmissions.
9. What is the frequency used by the localizer transmitter?
a) VHF
b) UHF
c) MF
d) LF
Explanation: The localizer transmitter used VHF range from 108-122 MHz frequency and provides information to the aircraft as to whether it is flying to the left or right of the center line of the runway it is approaching. The localizer receiver output is proportional to the angular deviation γL, of the aircraft from the localizer beam center line which in turn corresponds to the center line of the runway.
10. What is the frequency used by the glide slope transmitter?
a) VHF
b) UHF
c) MF
d) LF
Explanation: The glide slope or glide path transmission is at UHF frequencies from 329.3 to 335 MHz frequency and provides information to the aircraft as to whether it is flying above or below the defined descent path of nominally 2.5◦, for the airport concerned. The glide slope receiver output is proportional to the angular deviation γV, of the aircraft from the center of the glide slope beam which in turn corresponds with the preferred descent path.