# Power Absorption Design

> Increasing solidity to absorb high engine power.

- **Subject:** 081 — Principles of Flight
- **Section:** 081-07 — Propellers
- **Topic code:** 081-07-03
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/principles-of-flight/propellers/design-features-for-power-absorption/

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## The Problem
Powerful engines (turboprops) need to convert huge horsepower into thrust without the propeller tips going supersonic (which kills efficiency and creates noise).

## Solutions
1.  **Increase Solidity**: Ratio of blade area to disc area.
    *   **More Blades**: move from 3 to 4, 5, or 6 blades (e.g., C-130J has 6 blades).
    *   **Wider Chord**: Broader blades.
2.  **Scimitar Blades**: Swept-back tips to delay compressibility effects at high tip speeds (like a swept wing).
3.  **Contra-Rotating Propellers**: Two propellers on the same axis rotating in opposite directions.
    *   **Advantage**: Cancels torque, recovers energy from the slipstream (swirl), allows smaller diameter.
    *   **Disadvantage**: Complex, noisy.

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