Avionics Question Bank on “Instrument Landing Systems – 2”.
1. What is the type of receiver used for marker beacon?
a) Heterodyne
b) Super Heterodyne
c) Capacitative pick off
d) Crystal controlled
Answer: d
Clarification: The marker beacon receiver is a dedicated crystal controlled receiver fixed tuned to 75 MHz. This is because all marker beacons use the same frequency.
2. Which of the following cause multi path signals?
a) Low transmission power
b) Ground reflection
c) Low frequency transmission
d) High frequency transmission
Answer:b
Clarification: Mulit path Signals are created when a part of the original signal take a different path than LOS to reach the receiver. Thus a signal with same information reaches the receiver at multiple times. Multi path signals are created when the actual signal gets reflected from the ground and reaches the receiver.
3. Which of the following transmits an audio Morse code?
a) Localizer
b) Glide slope transmitter
c) DME
d) Marker beacons
Answer: a
Clarification: An audible Morse code identification signal is transmitted on the localizer frequency. A voice channel from the control tower may also be provided.
4. ______________ provides deviation when the aircraft is displaced laterally from the vertical plane of the runway?
a) Localizer
b) Glide slope transmitter
c) DME
d) Marker beacons
Answer: a
Clarification: The localizer establishes a radiation pattern in space the provides a deviation signal in the aircraft when the aircraft is displaced laterally from the vertical plane containing the runway center line.
5. What is the signal that are added to the localizer signal, if the beam is narrow, to provide signal coverage?
a) Localizer plus
b) Difference signal
c) Sum signal
d) Clearance signal
Answer: d
Clarification: When the localizer CSB pattern is narrow, to reduce reflections from buildings and other aircraft, the system requires the addition of “clearance” signals to provide 35° coverage in both directions.
6. What type of antenna is used in the localizer?
a) Long periodic antenna
b) Helical antenna
c) Dipole antenna
d) Parabolic antenna
Answer: a
Clarification: Almost all of the localizer antenna is long periodic antenna. It provides unidirectional radiation, can be installed without guy cables and has good broadband characteristics.
7. Clearance signals can be transmitted from the same array antenna as the localizer signal.
a) True
b) False
Answer: b
Clarification: Clearance Signals, when required, can be provided by a separate array antenna specifically for clearance signals. In some designs, both clearance signals and localizer signals are transmitted from different elements of the same array. Nevertheless, the same antenna cannot be used.
8. What is the type of glide slope that depends on the reflection of signals by the ground?
a) Reflection slope
b) Refraction glide slope
c) Image glide slope
d) Direct glide slope
Answer: c
Clarification: Image array glide slope systems depend on reflections from the ground in the direction of approaching aircraft to form the radiation pattern.
9. What is the radiation pattern of the marker beacons?
a) Triangle
b) Circle
c) Square
d) Fan shape
Answer: d
Clarification: Marker beacons provide pilot alerts along the approach path. Each beacon radiates a fan shaped vertical beam that is approximately ±40° wide along the glide path by ±85° wide perpendicular to the path.
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