Prop/asy

Question 1

What is better for asymmetric flight? Gear up or down? (In terms of preventing yaw)

Answer 1

Down as stabilising effect.

Question 2

What is used to determine Vmca?

Answer 2

Full power live engine
Rear most CoG
Gear up
T/O config
Windmilling engine 
Must not exceed 1.2Vs

Question 3

Why is rudder/aileron combo best?

Answer 3

Rudder counteracts yaw and ailerons to counteracts side force

Question 4

Explain torque effect

Answer 4

CW spin means left yaw so left CE

Question 5

Define blade angle, helix, AoA

Draw a diagram

Answer 5

Blade angle is the angle between the plane of rotation and surface of prop (chord line).
Helix (angle of advance) is the angle between plane of rotation and RAF.
AOoA is the angle between RAF and chord line.

Question 6

Describe the POF behind a windmilling prop.

Draw a diagram

Answer 6

Thrust acts in the opposite direction (windmill drag) and Ptq acts downwards (same as Etq) and is essentially which drives the engine.
Therefore TR acts in opposite direction.

Where Ptq is the resistance to motion in the plane of rotation and Etq is the force to overcome this. They must match for constant RPM.

Question 7

Describe a feathered propellor.

Draw a diagram.

Answer 7

Blade is coarsen Ed so not net Ptq is formed as it faces into the RAF. Hub of blade will have +AoA and tip -AoA so net 0. TR acts to produce minimal drag.

Question 8

Describe the centrifugal twisting moment.

Draw a diagram.

Answer 8

Acts from the centre of rotation acting on all parts of the blade.
Force in line of span acts to pull blade from socket, force at right angles to pitch change axis act to pull blade into fine… hence the CFT moment.
Is a greater force when in coarse.

Question 9

Describe aerodynamic twisting moment. Draw a diagram.

Answer 9

Occurs when the TR does not act through the pitch change axis.
In normal ops this TR (acts through CoP) lies fore of PCA so acts to coarsen pitch. Is weaker than CTM to partially offsets it.
In a windmilling prop it acts in the same direction as CTM to fine pitch… potentially with RPM over speed.

Question 10

What is the asymmetric blade effect? How does this affect the critical engine?

Answer 10

In level flight the RAF meets both the up/doing going blades at the same angle. When tilted, RAF becomes different (smaller on upgoing and greater downgoing).
Ie) if tilted upward, downgoing blade advances by forward speed + amount of tilt so greater AoA and more thrust.
This means for CW rotating engines, the left engine is critical.