overspeed

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Overspeed

 

(or racing), an abrupt spontaneous increase in the rate of shaft rotation of an internal-combustion engine that can lead to destruction of the engine. It is caused by a substantial increase in the supply of fuel-air mixture or fuel to the engine’s cylinders with light external loading, which occurs upon failure of the throttle valve in carburetor engines or of the high-pressure fuel injection pump in diesel engines. In two-cycle supercharged diesel engines, overspeed can also occur when the amount of oil entering the cylinders from the air filter is increased.

At the first signs of overspeed, the fuel supply is cut off and a load is applied to the engine; some diesel engines are equipped with an emergency-stop device, which shuts off the air supply to the cylinders.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

overspeed

i. A condition in which an engine has produced speed greater than its design speed.
ii. The condition in which the actual engine speed is higher than the designed engine RPM as set on the propeller control by the pilot. This condition is prevented by an overspeed governor. See overspeed governor.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved