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Propellers: Powerplant practice questions

Five original questions on propellers, each with the answer, an explanation and an FAA-H-8083-32B page reference.

1. Propeller efficiency is the ratio of what?
  1. Thrust horsepower to brake horsepower
  2. Rpm to airspeed
  3. Blade angle to pitch
Show answer

A. Thrust horsepower to brake horsepower Efficiency of any machine is useful power output divided by power input.

Reference: FAA-H-8083-32B, Ch. 7, p. 7-2

2. At low speed when maximum power and thrust are needed, what blade angle gives maximum thrust?
  1. Low blade angle
  2. High blade angle
  3. Feathered
Show answer

A. Low blade angle Blade angle is increased for high-speed flight.

Reference: FAA-H-8083-32B, Ch. 1, p. 1-36

3. If propeller blade angle is increased without adding power, what happens?
  1. More load is placed on the engine, tending to slow it down
  2. Engine rpm increases
  3. Thrust drops to zero
Show answer

A. More load is placed on the engine, tending to slow it down Blade angle is a means of adjusting propeller load to control engine rpm.

Reference: FAA-H-8083-32B, Ch. 7, p. 7-4

4. Hartzell recommends a tachometer accurate within what tolerance?
  1. ±10 rpm
  2. ±100 rpm
  3. ±1 percent
Show answer

A. ±10 rpm An inaccurate tach can let the prop turn faster than rated.

Reference: FAA-H-8083-32B, Ch. 7, p. 7-21

5. Why use a constant-speed propeller?
  1. To give the required thrust at maximum efficiency in all flight conditions
  2. To fix blade angle
  3. To eliminate the governor
Show answer

A. To give the required thrust at maximum efficiency in all flight conditions It adjusts blade angle automatically.

Reference: FAA-H-8083-32B, Ch. 1, p. 1-36

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What does the Powerplant test cover on propellers?

The Aviation Mechanic Powerplant ACS lists propellers as one of its areas. The FAA reference for this material is FAA-H-8083-32B.