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DGCA Technical General · 32 questions

Propellers: DGCA Technical General Questions and Answers

32 practice questions on Propellers with answers and explanations, plus the key concepts and formulas, from the TrueHeading question bank.

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About this topic

Use this page to revise Propellers for the DGCA Technical General paper. Below are the key ideas first, then 12 practice questions with answers and explanations, picked from the 32 questions in the TrueHeading bank for this topic.

In short: A governor changes blade pitch to keep RPM constant.

Open the full set in the student zone to answer every question, track your accuracy and take timed mock tests.

Key concepts: Propellers

4 ideas to know cold.

Constant-speed propeller: how does it work?

A governor changes blade pitch to keep RPM constant.

  • Fine pitch (low angle): high RPM, take-off
  • Coarse pitch (high angle): low RPM, cruise
  • Feathering: blade turned to about 90° to stop windmilling after an engine failure

Propeller effects on handling?

Torque, slipstream, P-factor and gyroscopic precession all produce yaw or roll tendencies.

  • P-factor: descending blade has a bigger angle of attack at high nose attitude, so yaw to the left for a clockwise-rotating propeller
  • Greater at low speed and high power

What is the difference between fixed and constant speed propellers?

A fixed pitch propeller has a fixed blade angle. A constant-speed propeller changes its pitch to keep a selected rpm.

  • Governor controls oil to the hub
  • Fine pitch: take-off; coarse: cruise
  • Feathering stops drag after engine failure

Propeller torque and gyroscopic effects?

Torque rolls the aircraft opposite to the rotation. Slipstream swirls to the fin. Gyroscopic effect yaws when pitching. P-factor yaws at high alpha.

  • Most pronounced at high power and low speed
  • Right-hand rotation (viewed from the cockpit) yaws left on take-off
  • Correct with rudder

Practice questions: Propellers

Tap “Show answer” after you have tried each one.

Q1A propeller of diameter 1.8 m turns at 2400 rpm. The tip speed (rotational only) is approximately:

  1. 711 m/s
  2. 113 m/s
  3. 226 m/s
  4. 452 m/s
Show answer

Answer: C. 226 m/s

Tip speed = π D N / 60. Tip speed is limited to keep the tips below the critical Mach number.

Q2A propeller of diameter 2.0 m turns at 2400 rpm. The tip speed (rotational only) is approximately:

  1. 503 m/s
  2. 790 m/s
  3. 126 m/s
  4. 251 m/s
Show answer

Answer: D. 251 m/s

Tip speed = π D N / 60. Tip speed is limited to keep the tips below the critical Mach number.

Q3A propeller of diameter 2.2 m turns at 2000 rpm. The tip speed (rotational only) is approximately:

  1. 724 m/s
  2. 230 m/s
  3. 461 m/s
  4. 115 m/s
Show answer

Answer: B. 230 m/s

Tip speed = π D N / 60. Tip speed is limited to keep the tips below the critical Mach number.

Q4An aircraft flying at 120 kt with the propeller at 2400 rpm advances (effective pitch) about how far per revolution?

  1. 3.09 m
  2. 0.77 m
  3. 1.54 m
  4. 2.31 m
Show answer

Answer: C. 1.54 m

Advance per rev = speed (m/s) / rev per second.

Q5An aircraft flying at 160 kt with the propeller at 2600 rpm advances (effective pitch) about how far per revolution?

  1. 2.85 m
  2. 1.90 m
  3. 0.95 m
  4. 3.80 m
Show answer

Answer: B. 1.90 m

Advance per rev = speed (m/s) / rev per second.

Q6Propeller pitch is the:

  1. distance the propeller would advance in one revolution if it moved through a solid
  2. tip speed
  3. blade length
  4. actual distance advanced per revolution
Show answer

Answer: A. distance the propeller would advance in one revolution if it moved through a solid

This is the geometric pitch.

Q7In a constant speed propeller, increasing the pitch lever (RPM lever) setting:

  1. increases the selected rpm (blades move to a finer pitch)
  2. locks the blades
  3. feathers the propeller
  4. decreases the rpm
Show answer

Answer: A. increases the selected rpm (blades move to a finer pitch)

High rpm = fine pitch; low rpm = coarse pitch.

Q8A coarse pitch is used for:

  1. low speed climb
  2. take-off
  3. engine start
  4. cruise at high speed
Show answer

Answer: D. cruise at high speed

It maintains efficiency at higher airspeed.

Q9The purpose of propeller reverse pitch is to:

  1. increase take-off thrust
  2. reduce noise
  3. produce a braking thrust on landing
  4. feather the propeller
Show answer

Answer: C. produce a braking thrust on landing

Blades are moved to a negative angle.

Q10Gyroscopic precession of a propeller causes a yaw when the aircraft is:

  1. pitched up or down
  2. taxied slowly
  3. rolled
  4. flown straight and level
Show answer

Answer: A. pitched up or down

A force applied to the rim acts 90° later in the direction of rotation.

Q11The propeller efficiency is the ratio:

  1. torque to thrust
  2. TAS to rpm
  3. thrust power divided by shaft (engine) power
  4. shaft power to thrust power
Show answer

Answer: C. thrust power divided by shaft (engine) power

η = T × V / P.

Q12A turboprop engine produces its thrust mainly from:

  1. the afterburner
  2. the exhaust jet
  3. the fan
  4. the propeller
Show answer

Answer: D. the propeller

The exhaust provides only about 10 %.

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