Avionics Multiple Choice Questions on “Instrument Landing Systems – 1”.
1. Which of the following systems use a collection of radio transmitting stations to guide an aircraft to a particular runway?
a) ILS
b) GPS
c) VOR
d) RADAR
Answer: a
Clarification: The instrument landing system or ILS is a collection of radio transmitting stations used to guide aircraft to a specific airport runway, especially during times of limited visibility.
2. How many ILS systems does an airport require?
a) 0
b) 1
c) Depends upon aircraft size
d) Depends upon density of traffic on the airspace
Answer: d
Clarification: High density airports where a lots of planes land and take off typically have more than one runways with multiple ILS systems. Chicago’s O’Hare airport had an ILS installed on 12 runways in 1996.
3. _______ standardized the signal in space for the ILS ground transmitting equipment?
a) ISRO
b) FAA
c) ICAO standards and recommended practices
d) NASA
Answer: c
Clarification: The ICAO Standards and Recommended Practices for the ILS, subscribed by the180 member states, standardize the signal in space for the ILS ground transmitting equipment, no matter where they are manufactured to maintain international standards.
4. Where is the localizer antenna placed?
a) Beyond the stop end of the runway
b) Start of the runway
c) Along the runway
d) Air traffic control
Answer: a
Clarification: The localizer antenna is centered on the runway beyond the stop end to provide lateral guidance. The glide slope is located beside the runway near the threshold to provide vertical guidance.
5. Which of the following is used to detect the failure in an ILS?
a) Fail safe ILS
b) Radiation monitors
c) ILS detector
d) ILS failure system is not used anywhere
Answer: b
Clarification: Radiation monitors are used to detect ILS failure. They are placed at a particular distance away from the runway to check for errors in ILS transmission or drift in the frequency of radiation.
6. What is the type of polarization is used in ILS systems?
a) Horizontal polarization
b) Vertical polarization
c) Circular polarization
d) No polarization
Answer: a
Clarification: Every transmitter in the ILS including the glide slope transmitter, localizer and the marker beacons radiate continuous wave, horizontally polarized, radio frequency energy which can be received by the on-board receiver.
7. What is the frequency at which the marker beacons operate?
a) 65 MHZ
b) 50 MHZ
c) 150 MHZ
d) 75 MHz
Answer: d
Clarification: All the marker beacons, all around the world, operate on a single frequency of 75MHz.
8. Localizer, Glide slope and DME frequencies are paired to each other.
a) True
b) False
Answer: a
Clarification: The localizer, glide slope and DME frequencies are paired such that only the localizer frequency is required to tune by the pilot. This hard pairing reduces the pilot’s work load.