Definition
A condition in which the propeller and engine rotate faster than the maximum rpm allowed by the engine or propeller manufacturer. In a constant-speed propeller installation, over-speeding occurs when the propeller blades cannot move to a coarse enough pitch to absorb the power being produced, allowing rpm to climb past the red line. Causes include governor failure, oil supply problems to the propeller hub, low pitch stop issues, or pilot mismanagement of throttle and propeller controls.
Plain English
The engine and propeller are spinning faster than they are built to handle. The system that normally holds rpm steady is no longer keeping it under control, so rpm runs up past the safe limit.
Context Anchor
Encountered during constant-speed propeller operation, especially when discussing propeller governor control and RPM limits.
Derivation
“Over” means beyond or too much, and “speeding” means moving or turning fast. In this aviation use, the word points to a rotating part going beyond its safe speed limit.
Why Pilots Care
Uncorrected over-speeding can cause propeller blade failure, engine damage, or loss of aircraft control.
Intuition Check
Over-speeding does not mean the airplane is flying too fast through the air. Here it means the engine or propeller RPM is too high.
Example Sentence 1
When the propeller governor failed, the rpm climbed rapidly and the pilot reduced throttle to prevent over-speeding the engine.
Example Sentence 2
A governor malfunction during descent can allow the propeller to begin over-speeding if blade pitch is not increased in time.