Avionics Multiple Choice Questions on “Automatic Landing Systems”.
1. Auto land system is a must for _________ and above?
a) Category I
b) Category II
c) Category III
d) Category IV
Answer: b
Clarification: Air carrier aircraft that are authorized for precision approach below Category II must have an automatic landing system. Auto land systems use information from various landing systems like ILS Tacan and at some cases even GPS to safely land the aircraft.
2. The reduction of glide slope gain is called as________
a) Auto throttle
b) Auto gain
c) Auto attenuation
d) Gain scheduling
Answer: d
Clarification: During the final approach the glide slope gain in the auto land system is reduced in a programmed fashion and is called gain scheduling. Supplementary sensors must supply the vertical guidance below 100ft.
3. What is the nominal accuracy of radar altimeters below 100ft?
a) 5 ft
b) 10 ft
c) 20 ft
d) 1.5 ft
Answer: d
Clarification: Low range radar altimeters have a nominal accuracy of 1.5 ft below 100ft altitude and 2% of full scale at higher altitude. They have a low noise output that allows the derivation of vertical rate information.
4. Accurate calculation of aircraft height using the glide path deviations and distance information is not practical.
a) True
b) False
Answer: a
Clarification: The ILS cannot develop similar information as radar altimeter since the glide slope receiver provides from the zero DDM glide path which is not at a constant height across the width of the localizer course. Therefore, accurate calculation of aircraft height using the glide path deviations and distance information is not practical.
5. What is the wheel height where flare command is initiated?
a) 75ft
b) 100ft
c) 25ft
d) 5ft
Answer: a
Clarification: The flare command is initiated at a wheel height of about 75ft, well before the runway threshold. However, the radar altimeter may not be used prior to threshold due to uneven terrain or tidal variations.
6. __________ is the exponential path tangent to a horizontal plane several feet below the runway?
a) Flare
b) Ground roll
c) Taxi
d) Tide
Answer: a
Clarification: The flare is an exponential path tangent to a horizontal plane several feet below the runway, which ensures a positive touchdown.
7. What is done to reduce the error in localizer as the runway is approached?
a) Gain scheduling
b) Reduce speed
c) Increase angle of attack
d) Flare
Answer: a
Clarification: The localizer gain must be scheduled to decrease as the runway is approached because the surfaces of constant DDM coverage to make the error signal more sensitive to distant displacement.
8. British Trident and U.S. L-1011 aircraft was certified for category III A operations.
a) True
b) False
Answer: a
Clarification: In the early 1970s the British Trident and the U.S. L-1011 aircraft including their autoland systems were certified for Category III A operations in revenue service using guidance information form the ILS and other on-board sensors.