Definition
A condition in which an engine or propeller exceeds its maximum certified rpm limit. On a constant-speed propeller installation, an over-speed occurs when the propeller governor fails to keep rpm within limits and the engine and propeller turn faster than the manufacturer's maximum allowable rpm.
Plain English
The engine or propeller is spinning faster than it is designed and approved to spin.
Context Anchor
Seen during constant-speed propeller operation, especially when monitoring the tachometer after power changes, propeller control changes, or a descent.
Why Pilots Care
Continued over-speed can damage the propeller, engine, or both and requires immediate power reduction.
Grounding Statement
If the propeller is turning faster than the selected or allowed RPM, the airplane is in an over-speed condition.
Intuition Check
Over-speed does not simply mean the airplane is flying too fast. In this context, it means the engine and propeller RPM are too high.
Example Sentence 1
When the governor failed, the propeller went into an over-speed and the pilot reduced the throttle to bring rpm back within limits.
Example Sentence 2
The pilot reduced throttle to bring the over-speed condition back within limits.