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 ?
Since the accident the pilot and his co-pilot have undergone training focussing on the overspeed recovery, the report said.
The report concluded: "The serious injuries suffered by a cabin crew member occurred because significant manual control inputs were applied in response to an impending overspeed, which resulted in the aircraft manoeuvring abruptly.
Sentry G3 is Sensonics latest generation of protection equipment for overspeed protection applications.
THE OVERSPEED SHUTDOWN OCCURS WHEN THE ENGINE SPEED GOES 10 PERCENT BEYOND ITS RATED SPEED.
Identifying abnormal Nr (high or low) is the best way to differentiate between overspeed and underspeed.
It features two-channel operation and can be used for standstill and overspeed monitoring of three-phase motors.
Its rigid frame is designed for stability, and a constant-force barrel/spindle mechanism has the ability to reduce overspeed errors.
In the event of an engine overspeed condition, typically at about 2,300rpm, a switch triggers both the fuel shut-off and the Pyroban air intake shutdown valve to ensure that the engine shuts down, it added.
PTC systems are used to prevent train-to-train collisions, overspeed derailments and casualties or injuries to roadway workers.
Some local media said that the bus fell into a ravine after it overturned due to overspeed. (Xinhua-ANI)
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.