Air Data Instruments Questions and Answers

Answer: A

The first is correct and the second reverses the physics: stalling speed rises with weight and load factor, while the stalling angle of attack stays essentially fixed. That is precisely the argument for sensing the angle rather than the speed.

Answer: B

Correct answer: Both Statement I and Statement II are correct

Both are true and the second explains the first. The instrument compares the pressure in a capsule with that in a surrounding case vented through a calibrated leak, and the difference between them is a measure of how fast static pressure is changing. Because the case takes time to equalise, the reading lags a change in vertical speed by several seconds - useful for holding a rate, misleading for starting one.

Answer: C

Each step removes one distinct physical effect, and the order is fixed because compressibility is defined relative to calibrated airspeed. Applying density before compressibility gives a wrong answer at high speed and altitude.

Answer: D

Correct answer: 1, 2, 3, 4, 5

The two pressures must be sensed before they can be differenced, so the pitot and static inputs come first, in either order. Their difference then deflects the capsule, a linkage scales that deflection according to the calibration, and the pointer displays the result. The instrument is entirely mechanical, which is why it can be treated as a standby when everything electrical has failed.

Answer: A

QFE reads zero on the aerodrome, QNH reads the aerodrome elevation, and the standard setting is used above the transition altitude for mutual consistency. The three answer different questions rather than being alternatives of equal merit.

Answer: B

Correct answer: 1, 2, 3, 4, 5

With both the inlet and the drain blocked, the total pressure in the line is sealed at whatever it was at the moment of blockage. As the aircraft climbs the static pressure falls, so the difference across the capsule grows even though the aircraft has not accelerated, and the indicated airspeed rises. Read as a genuine overspeed it invites a pitch-up that can approach the stall - a sequence that has caused fatal accidents.

Answer: C

Mach number comes from pressures alone, but converting it into knots needs the speed of sound and therefore the static temperature. The ram rise must be removed first because it depends on the Mach number just computed.

Answer: D

Correct answer: Only three

The first three are right: the altimeter uses static alone, the airspeed indicator the difference between total and static, and the vertical speed indicator the rate of change of static. The machmeter is the odd one out - it forms a ratio from total and static pressure and needs no temperature input at all, since the temperature terms cancel.

Answer: A

The first three are correct and cover the three datums an altimeter can be set to. QDM is a magnetic bearing to a station and belongs to radio navigation, having nothing to do with the pressure datum the altimeter references.

Answer: B

Correct answer: Only three

The first three pair correctly: position error arises because local pressure at the port differs from the free stream, the compressibility correction accounts for air not behaving as an incompressible fluid, and the density correction converts to true airspeed. Ram rise has nothing to do with wind - it is the temperature increase from bringing the air to rest at the probe.