Multi-Engine

Torque

The engine turns the propeller one way, so the propeller turns the airplane the other way. With clockwise props the reaction rolls you left — and left is exactly where you do not want to go with a dead left engine. Unlike the other three letters of PAST this one has no moment arm to argue about; it is a pure couple, and only its direction matters.

Rear view · looking forward

propeller rotation reaction torque—

PowerHighTorque follows the power the engine is making, so it is strongest at full throttle and low airspeed — engine-out climb, exactly when the ailerons are least effective.

Right engine rotationCounter-rotating: the right engine turns the other way, so its reaction rolls the airplane right instead of left.

Does torque help or hurt the surviving engine?

Lose left engine
(right engine working)

Lose right engine
(left engine working)

opposes the roll toward the dead engine adds to it

Torque

PAST

PP-factor
AAccelerated slipstream
SSpiraling slipstream
TTorque