Which statement about a propeller is correct?
I. Asymmetric blade effect is unaffected when engine power is increased.
II. Asymmetric blade effect is independent of the angle between the propeller axis and the airflow through the propeller disc.
Refer to figures.
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
Asymmetric blade effect
To analyze these effects, consider a right-handed propeller, which rotates clockwise as viewed from the cockpit.
The Asymmetric blade effect is more significant in situations of high power (RPM) and low forward speed, such as take-off or low speed climbs. Therefore, statement 1 is incorrect.
This effect occurs when the axis of rotation of the propeller is inclined to the direction of flight. For example, when the tail wheel on a tail-dragger type aircraft is in contact with the ground, its longitudinal axis inclines above the horizontal. Therefore, statement 2 is incorrect.
This causes the down-going blade to have a greater effective angle of attack than the up-going blade, thus developing greater thrust.
The thrust asymmetry between the two blades causes the aircraft to yaw to the left on take-off. Conversely, if an aircraft is flying yawed, then the asymmetry of the thrust causes a pitching moment.
Your Notes (not visible to others)
This question has appeared on the real examination, you can find the related countries below.
Use Keyboard Shortcuts
