Multi Engine Theory

Question 1

Which is the critical engine on a conventional twin?

Answer 1

Left

Question 2

What is induced flow?

Answer 2

Propellers of wing mounted engines create an accelerated slipstream of air over the wings resulting in increased lift over that portion of wing.

Just as P‐factor causes asymmetrical thrust forward, it also produces the same effect in the asymmetrical airflow behind the propeller (down going blade=more slipstream)

Question 3

What three factors determine if an engine is critical?

Answer 3

1. P‐Factor
2. Accelerated Slipstream
3. Torque

Question 4

What is P­-factor? ­

Answer 4

P‐factor is where the descending propeller blade creates more thrust than the ascending blade, causing asymmetrical thrust on each side of the propeller.

Question 5

What is the effect of torque from an engine and prop rotating?

Answer 5

As the engine and propeller rotate in one direction, they, in turn, try to rotate the airplane in the other direction

Question 6

Why is failure of the left most critical with regards to torque?

Answer 6

If the left engine fails, the yawing moment from the right engine (thrust) and the total torque will both work together to yaw and roll the airplane to the left.

Question 7

What happens to Vmc as density altitude increases?

Answer 7

VMC decreases due to the fact that as density altitude increases engine power will decrease, therefore less asymmetrical thrust, meaning the yawing from a failed engine will be less

Question 8

How does a forward C.G. affect Vmc?

Answer 8

It decreases Vmc

Large arm to rudder = Larger rudder moment = Rudder more effective.