# Secondary Propeller Effects

> Undesired aerodynamic and gyroscopic effects of rotating propellers.

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

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## 1. Torque Reaction
Based on Newton's 3rd Law.
*   **Effect**: The engine turns the prop Right -> The aircraft tends to Roll Left (in the air) or Yaw Left (on the ground due to tire friction difference).

## 2. Slipstream Effect (Corkscrew)
The slipstream spirals around the fuselage.
*   **Effect**: Hits the **Left** side of the vertical fin.
*   **Result**: Pushes tail Right -> Nose Yaws **Left**.
*   **Correction**: Right Rudder (mostly at high power/low speed).

## 3. Gyroscopic Precession
A force applied to a rotating disc is felt 90° later in the direction of rotation.
*   **Tail Up (Takeoff)**: Force applied to TOP of prop arc -> Felt at RIGHT side -> Yaws **Left**.

## 4. Asymmetric Blade Effect (P-Factor)
Occurs at high Angles of Attack (Climb/Takeoff).
*   **Descending Blade (Right side)**: Has higher effective AoA and speed -> Produces MORE Thrust.
*   **Ascending Blade (Left side)**: Has lower AoA -> Produces LESS Thrust.
*   **Result**: Center of Thrust moves to the Right -> Yaws **Left**.

*Note: All examples assume a standard clockwise-rotating propeller (viewed from behind).*

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Free study notes from pilotsyllabus.com. Not a substitute for training at an approved ATO.