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Which statement is correct regarding the gyroscopic effect of a clockwise rotating propeller on a single engine aeroplane?

I. Pitch up produces right yaw.
II. Right yaw produces pitch up.

  • A
    I is correct, II is incorrect.
  • B
    I is incorrect, II is incorrect.
  • C
    I is correct, II is correct.
  • D
    I is incorrect, II is correct.

Refer to figure.
On take-off, rotation of a single-engine propeller causes an aircraft to swing to one side, particularly those fitted with a tail-dragger undercarriage. The main causes of this are:

  • Slipstream effect
  • Torque reaction
  • Gyroscopic effect
  • Asymmetric blade effect

Gyroscopic Effect

A rotating propeller has the properties of a gyroscope - rigidity in space and precession. The characteristic which produces “gyroscopic effect” is precession. Gyroscopic precession is the reaction that occurs when a force is applied to the rim of a rotating disc. When a force is applied to the rim of a propeller, the reaction occurs 90° ahead in the direction of rotation and in the same direction as the applied force. As the aircraft is pitched up or down or yawed left or right, a force is applied to the rim of the spinning propeller disc.

Note: Gyroscopic effect only occurs when the aircraft pitches and/or yaws.

For a clockwise rotating propeller:

Pitch down - forward force on the top, force emerges 90° clockwise, left yaw.
Left yaw - forward force on the right, force emerges 90° clockwise, pitch up.
Pitch up - forward force on the bottom, force emerges 90° clockwise, right yaw. Therefore, statement 1 is correct.
Right yaw - forward force on the left, force emerges 90° clockwise, pitch down. Therefore, statement 2 is incorrect.

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