Chapter 26: Propeller Design and Effects

Question 1

Prop Design

Blade design to absorbe large shaft power (4), drawback?

Answer 1

Blade length (care ground, SS tip, more yaw of OEI)
Reduce prop efficiency (noise)
Prop solidity:
blade # (wake on next blade, limited by hub)
larger chord (more vortex)

Question 2

Contra Rotating Propellers

Answer 2

2 set blades rotating in opposite direction

Question 3

Propeller effects for RHP (Right Hand Prop) (4)

Direction of adverse effect

Answer 3

Torque Reaction (roll left, yaw left)
Slipstream (yaw left)
P factor (thurst offset right, yaw left)
Gyroscopic effect

Question 4

P factor

What is it? When is it worse (3)

Answer 4

Downgoing blade has higher AoA, thrust offset to the right, yaw to the left
Worse at low V, high AoA, high RPM (i.e. TO for exemple)

Question 5

Gyroscopic Effect

Answer 5

pitch up: yaw right
pitch down: yaw left
yaw right: pitch down
yaw left: pitch up

Question 6

Propeller Icing

Efficiency lost? Where worst?

Answer 6

10% loss efficiency up to 15 - 20%
More than 20% = cell icing
Icing worst at root (tip = too fast)