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(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.


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.
References in periodicals archive ?
Rob Double, from Pyroban, describes the overspeed condition.
Within two minutes, the autopilot disconnected, and five seconds later, pilots began receiving spurious cockpit alarms and alerts about stalling and overspeed warnings, along with fluctuating airspeed and altitude readings.
The overspeed light does not momentarily blink when the battery switch is turned on.
Plungers of both materials were tested to determine the effects of side loading forces, overspeed and overpressure conditions, and low lubricity.
Other features include automatic rotor recognition, overspeed protection and rotor imbalance detection.
Heading mode gives basic compass directions and overspeed mode offers additional warnings when approaching speed detection devices.
This is tricky since the U-2 is dynamically unstable, and the difference between stall and overspeed (and aircraft break-up) is only 15 knots at altitude.
You'll also find light sensitive headlamps, rain sensitive windscreen wipers and an overspeed warning to avoid any nasty confrontations with the boys and girls in blue.
In wrap configured, traction-driven slitters, attempting to overspeed the lower slitter system to compensate for upper blade speed loss is impractical.
A combination of a fully adjustable steering wheel, height adjustable front seats, remote control switches for the stereo system, a sensor that switches on the hazard warning lamps under emergency braking and an overspeed warning system make this a class leader in no uncertain fashion.
The accident may have been prevented if maintenance had not been recently scaled back, and the overspeed trip had been periodically tested for proper operation.
For example, a coach may train athletes with speed chutes (resisted training), but fail to employ a complementary overspeed training method such as downhill running.