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What does an APU do on an airplane?
An Auxiliary Power Unit or APU allows an aircraft to operate autonomously without reliance on ground support equipment such as a ground power unit, an external air-conditioning unit or a high pressure air start cart.
Does the APU start the main engines?
The auxiliary power unit (APU) is a small gas turbine engine mounted in the tail cone of an aircraft to provide autonomous electrical and mechanical power for the following: Starting power for the main engines.
Is it safe to fly without an APU?
Yes, you can operate without an APU. If the APU is inoperative you will need to write it up and coordinate with maintenance and dispatch to operate under the stipulations of the MEL.
Why did Sully turn on the APU?
In its report on Flight 1549, the US National Transportation Safety Board said that Captain Sullenberger’s decision to start the APU was “critical because it improved the outcome of the ditching by ensuring that electrical power was available to the plane.”
Can a plane fly without an APU?
Without an APU an aircraft would depend on GSE only for starting one engine with pressurized ground supplied air. Aircraft are allowed in general to fly without an APU. Exceptions are flights with two-engined aircraft and long routes over water or terrain without an alternate airport – so called ETOPS flights.
Does the APU stay on during flight?
In most cases, the APU is shut down before takeoff and reignited when the aircraft clears the runway after landing. While most of an APU’s active service life occurs as the aircraft sits on the ground, in some instances the APU is used as an emergency electrical power source while the aircraft is airborne.
What kind of Apu does a Boeing 737 have?
There are many different APU’s available for the 737. The most common is the Garrett GTCP (Gas Turbine Compressor [air] Power unit [electrics]) 85-129. This was standard for the series 1/200 but when the -300 was introduced it was found that two to three times the energy was needed to start the larger CFM56 engines.
Why are APUs not enough to maintain level flight?
Practically speaking, APUs are not sufficiently powerful to provide the thrust necessary to maintain level flight. It is an issue of power (as well as having that power effectively converted to thrust).
What does the APU do on an airplane?
The APU is designed to provide electrical, bleed air (for environmental control, and for starting other engines), and in some cases they may run other accessories. It may be possible to have more power available to the main engine (s) if the APU is used for electrical, bleed air, etc. Normally, this is not done in most aircraft.
How much thrust does a Boeing Airplane have?
Engine Thrust Hazards in the Airport Environment Boeing commercial airplanes are equipped with engines rated from 18,000 to nearly 100,000 lb of thrust. Such thrust levels provide for safe takeoff, flight, and landing over a wide range of temperatures, altitudes, gross weights, and payload conditions.