Questions on APUs
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Questions on APUs
-- Is the APU just a turbine fan in the rear of the Aircraft
-- As I understand the jet engines are started either off the APU or off an airstart and then a crossbleed to the other engine. What initiates the APU?
-- Finally, how does an Inop. APU affect ETOPS? Can the Aircraft still fly?
-- As I understand the jet engines are started either off the APU or off an airstart and then a crossbleed to the other engine. What initiates the APU?
-- Finally, how does an Inop. APU affect ETOPS? Can the Aircraft still fly?
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1) No it is a jet engine
2) A switch which starts the starter motor
3) It is a 'no-go' for 737s (not sure whether a RAT will be acceptable on other types though)
2) A switch which starts the starter motor
3) It is a 'no-go' for 737s (not sure whether a RAT will be acceptable on other types though)
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1. The apu is in effect an centrifugal jet engine, similar to those installed in turbojet aircraft. The size of the APU will differ along with the airframe.
2. The APU is normally started by an electric starter powered by a battery. The battery may be the ships battery or a dedicated APU battery. Some aircraft (777) also have a air turbine starter powered by bleed air as the primary method of starting. The electric being a backup system. (ETOPS requirement).
3. The APU inop or with a partial starting system, will affect ETOPS but will not cause the flight to be cancelled. The APU can be started on the ground and kept running the entire flight, with no ETOPS effect, or treated as inop, kept off and limited to 120mins.
These are all based on a US carrier policies, hope this helps!
2. The APU is normally started by an electric starter powered by a battery. The battery may be the ships battery or a dedicated APU battery. Some aircraft (777) also have a air turbine starter powered by bleed air as the primary method of starting. The electric being a backup system. (ETOPS requirement).
3. The APU inop or with a partial starting system, will affect ETOPS but will not cause the flight to be cancelled. The APU can be started on the ground and kept running the entire flight, with no ETOPS effect, or treated as inop, kept off and limited to 120mins.
These are all based on a US carrier policies, hope this helps!
