# Propeller Engine Failure

> Windmilling drag, feathering, and asymmetric thrust.

- **Subject:** 081 — Principles of Flight
- **Section:** 081-07 — Propellers
- **Topic code:** 081-07-02
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/principles-of-flight/propellers/engine-failure/

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## 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.

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