Avionics online quiz on “Temperature, Angle of Attack and Angle of Side Slip Measurements”.
1. What is the temperature of the air surrounding the aircraft called as?
a) Stagnation temperature
b) Static temperature
c) Total temperature
d) Overall temperature
Answer: b
Clarification: The outside air temperature is also called the static air temperature and is necessary for computing various parameters such as true airspeed, air density and for fire control aiming solutions.
2. What is the temperature measured by a probe on the exterior of a moving aircraft?
a) Static temperature
b) Stagnation temperature
c) Free stream temperature
d) Constant temperature
Answer: b
Clarification: The temperature measured by the temperature probe on the exterior of a moving aircraft is called the stagnation temperature. It is always higher than the static temperature due to the heating effects of compressing air at higher speeds.
3. Why is a hole required at the rear end of the temperature probe?
a) Dual measurements
b) Redundancy
c) Reduce time lag
d) Convective cooling
Answer: c
Clarification: To avoid time lags in the temperature measurements, a leakage hole at the rear end of the probe allows for rapid exchange. For redundancy, multiple temperature probes are placed in different parts of the aircraft.
4. Which is the optimum place for a temperature probe?
a) Landing gear
b) Inside cockpit
c) Exit of engine
d) Tip of vertical tail
Answer: d
Clarification: Probes may be mounted on the wing tips, vertical tail, forward fuselage or other areas where the local mach number is the same as the free stream mach number for all expected flight altitudes and speeds.
5. The recovery factor for computing the static temperature does not account for _____
a) Friction heating
b) Re-radiation
c) Nonisentropic compression
d) Isentropic compression
Answer: d
Clarification: The recovery factor of the probe corrects the original measured temperature readings for frictional heating in the skin, re-radiation from the aircraft to the flow, and nonisentropic compression of air. It is given by η and is measured empirically.
6. The temperature is probe is actually an electric coil whose resistance varies with temperature.
a) True
b) False
Answer: a
Clarification: The temperature probe mounted on the outside of the aircraft is usually a small coil of wire whose resistance varies with temperature. Electric heaters used for deicing must be isolated from thermometer element.
7. What error will a 10°C error in temperature shown in true airspeed?
a) 10 Knots
b) 20 Knots
c) 0.2 Knots
d) Greater than 1 Knot
Answer: d
Clarification: A 10°C error in the temperature will result in a true airspeed greater than 1 knot at a typical transport aircraft flight conditions.
8. The angle between the relative wind and the longitudinal datum line on the fuselage is called as?
a) Flight path angle
b) Glide angle
c) Relative angle
d) Angle of attack
Answer: d
Clarification: Angle of attack is the angle, in the normally vertical plane of symmetry of the aircraft, at which the relative wind meets an arbitrary longitudinal datum line on the fuselage. Angle of attack, is important as it corresponds to the amount of lift produced and the dangerous condition of stall.
9. Which flight critical system is the angle of attack indicator a part of?
a) Stall warning system
b) Airspeed indicator system
c) Landing system
d) Rate of climb indicator system
Answer: a
Clarification: When angle of attack sensors are installed on an aircraft they are usually apart of an independent stall warning or stall control system. Since such systems are flight critical, redundant sensors are usually installed.
10. Sideslip sensors are only used in experimental aircraft and not in general aviation or commercial aircraft.
a) True
b) False
Answer: a
Clarification: Sideslip sensors are usually used only in developmental flight test instrumentation and experimental aircraft. In commercial and general aviation aircraft, sideslip is approximated by a body mounted accelerometer and displayed on the pilot’s ball bank indicator.
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