Overspeed is a condition in which an engine is allowed or forced to turn beyond its design limit. The consequences of running an engine too fast vary by engine type and model and depend upon several factors, the most important of which are the duration of the overspeed and the speed attained.

What causes engine overspeed?

Overspeed is any speed beyond the operating range specified by the engine manufacturer. Very often overspeed leads to serious damage, not only to the engine itself, but also to generators and gears. There are several reasons for overspeed, but the most common is malfunction of the governor or fuel oil pumps.

What's the meaning of overspeed?

: to cause (as an engine) to run at an excessive speed. intransitive verb. : to run at an excessive speed.