overspeed


Also found in: Acronyms.

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.

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.
References in periodicals archive ?
If a Fault 234: Overspeed Shutdown code shows up on the generator's digital control system (DCS) screen, take the CORRECTIVE ACTION found in WP 0010 of TM 9-6115-750-10 (Feb 11):
Identifying abnormal Nr (high or low) is the best way to differentiate between overspeed and underspeed.
Rob Double, from Pyroban, describes the overspeed condition.
Some local media said that the bus fell into a ravine after it overturned due to overspeed.
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.
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 Gulf of Mexico accident has meant that oil and gas operating companies pay more attention to the generator set overspeed problem.
Giving a witness account, Azizullah said: "Ever-since the road has been black-topped, most drivers have been resorting to overspeed.
Road near Ahmedabad due overspeed and overloading, killing 6 people while two other were taken out from the Nullah alive.
On April 12, 2001, Kylie Burley was injured while using the Overspeed Trainer, an athletic training device used for resistance and strength training that was manufactured and marketed by Kytec Innovative Sports Equipment, Inc.
The system is also designed to provide standard performance data warnings on a range of conditions, such as high/low coolant temperatures, high/ low dc voltage, low oil pressure, overcurrent, overspeed, weak battery, underfrequency and up to four customer fault inputs.
A 10 to 30-knot overspeed of the gear ain't as bad as hittin' the ground.