Propeller Engine Failure

Windmilling

When an engine fails, the airflow drives the propeller (it acts like a turbine).

• Drag: Creates massive drag because the propeller is taking energy from the airflow to spin the dead engine.
• Effect: Severe yaw towards the dead engine and reduced performance.

Feathering

Rotating the blades to a high pitch angle (~90°) so the leading edge faces the airflow.

• Purpose: Stops rotation and minimizes drag. Essential for multi-engine safety.

Asymmetric Thrust (Multi-Engine)

Failure of one engine creates a yawing moment ($Thrust \times Distance\ from\ CG$) towards the dead engine.

• Critical Engine: The engine whose failure results in the most adverse effects on handling and performance (usually the left engine on clockwise props due to P-factor).
• Vmca (Minimum Control Speed Air): The lowest speed at which directional control can be maintained with the critical engine failed.