Gyroscopic Instruments Questions and Answers

Answer: A

Correct answer: Both Statement I and Statement II are correct

Both are true. A ring laser gyro has no rotor, so there is nothing to spin up and the instrument is available immediately.

It works by the Sagnac effect: two laser beams travel in opposite directions around a closed path, and rotation makes their effective path lengths differ, producing a frequency difference proportional to the rate. The absence of moving parts also removes bearing friction, so real drift is very much smaller than in a spinning mass gyro.

Answer: B

Correct answer: Statement I is incorrect but Statement II is correct

The second statement gives the relation correctly, and it refutes the first. Since the drift is \( 15\sin\phi \), the sine is zero at the equator and one at the poles.

Apparent drift from earth rate therefore vanishes at the equator and is greatest at the poles - the opposite of the assertion. Physically, at the equator the local vertical is perpendicular to the earth's axis, so rotation about that axis produces no apparent movement in azimuth.

Answer: C

The loop deliberately exploits precession rather than fighting it, applying torque in the axis that produces the wanted motion. Because the sensor cannot tell gravity from acceleration, the same loop generates the turn and acceleration errors.

Answer: D

The failure is gradual rather than abrupt, which is exactly what makes it dangerous: the instrument keeps producing a plausible indication while becoming steadily wrong. Splitting instruments between air and electrical drive exists to break that chain.

Answer: A

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

The order follows from the compass's limitations. Steady level unaccelerated flight comes first, because the magnetic compass suffers turning and acceleration errors and is trustworthy in no other condition.

The compass is then allowed to settle, since it oscillates after any disturbance. Only then is the heading read and the gyro set to it. The repetition at intervals - conventionally about fifteen minutes - is what keeps accumulated drift within a degree or two.

Answer: B

The progression runs from a rotor driven by a vacuum pump to one driven electrically, then to optical devices with no moving parts at all. Each step removed a class of failure and drift that the previous one could not eliminate.

Answer: C

The design combines the compass's north-seeking property with the gyro's steadiness, applying the correction slowly enough that turns and accelerations average out. That slow slaving rate is what keeps the compass errors from reaching the display.

Answer: D

Correct answer: Only three

The first three are correct: the attitude indicator's spin axis is vertical, the directional gyro's is horizontal, and the turn indicator's is horizontal and lateral.

The fourth is wrong on a more basic point. The slip indicator has no gyro at all - it is a ball in a curved liquid-filled tube, responding to the resultant of gravity and centrifugal force. It shares a case with the turn indicator, which is why it is often assumed to share its mechanism.

Answer: A

Correct answer: Only three

The first three classify their causes correctly. Bearing friction applies a real torque and produces real drift; the earth's rotation and the aircraft's movement over it both produce apparent drift, the axis staying fixed while the reference frame turns.

The fourth is misclassified. Rotor imbalance applies an actual torque to the gyro, so it causes real drift. The test is whether the axis genuinely moves: a torque means real, a rotating reference frame means apparent.

Answer: B

Correct answer: Only three

The first three are right: rigidity in space is the axis holding its direction absent a torque, precession appears 90 degrees from the applied force, and the rate is torque divided by angular momentum.

The fourth reverses the dependence. Rigidity increases with rotor speed, since angular momentum rises with it and precession for a given torque falls. A slowing rotor is a less rigid one, which is exactly why a failing vacuum pump degrades an instrument progressively.