Avionics Questions and Answers for Entrance exams on “Traffic Alert, Collision Avoidance System & Weather Radar”.
1. The time between the collision of two aircraft on a collision course is called _____
a) Differential time
b) Tau
c) Traffic time
d) Collision time
Answer: b
Clarification: Tau is the range of the other aircraft with respect to an aircraft divided by range rate. Range divided by range rate is time-essentially the time that would elapse before a collision.
2. What does the threshold number for Tau depend on?
a) Speed of the aircraft
b) Size of the aircraft
c) Experience of the pilots
d) Maneuverability of the aircraft
Answer: d
Clarification: the threshold number for Tau, whether it is 10 sec or 100 sec depends on the ability of the aircraft to maneuver and avoid a collision.
3. What is the surveillance range of a general TCAS system?
a) 30 sec
b) 20 min
c) 2 min
d) 4 min
Answer:d
Clarification: The range of a general TCAS system is around 4 minutes before collision. At 45 seconds before collision TCAS gives traffic advisory and at 25 seconds before collision provides resolution advisory.
4. TCAS I provide proximity warning only.
a) True
b) False
Answer: a
Clarification: TCAS I provide only proximity warning and aids the pilot in visual identification of potential threat aircraft.
5. Whisper shout is used to avoid garble in TCAS.
a) True
b) False
Answer: a
Clarification: TCAS uses two different methods to avoid garbling. One is whisper shout and the other is using directional interrogations.
6. What is the range of typical weather radar?
a) 500 nmi
b) 50 nmi
c) 5 nmi
d) 200 nmi
Answer: d
Clarification: The use of airborne weather radar is one method of storm avoidance. A weather radar system can show centers at a distance of up to 200 nmi.
7. What is the frequency of operation of weather radar?
a) 1000 MHz
b) 500 kHz
c) 9375 MHz
d) 548 kHz
Answer: c
Clarification: The weather radar operates at a frequency of 9375 MHz, corresponding to a wavelength of 3 cm. This small wavelength gets easily reflected from clouds containing high water concentrations.
8. What is the gain required by a weather radar antenna?
a) 65 dB
b) 50 dB
c) 25 dB
d) 5 dB
Answer: c
Clarification: The signal strength of echoes from storms located at a distance from the aircraft is very low, which requires the transmitter to operate at very high power levels and that the antenna have a gain of more than 25 dB.
9. A power of 5 kW to 50 kW is required even when using narrow beams.
a) True
b) False
Answer: a
Clarification: Even with narrow beamwidth antennas, the radar transmitter requires from 5kW to 50kW of output power. When coupled with an antenna of 25 dB, this combination can result in an effective power more than a million watts.
10. What is the minimum safe approach distance for a radar system operating in excess of 5kWhr?
a) 100ft
b) 10ft
c) 17ft
d) 4ft
Answer: d
Clarification: With radar system operating in excess of 5kW output, the minimum safe approach distance to weather radar is about 4ft.
Avionics for Entrance exams,