APU Question

[Radio Homer]

ok so ive just been reading a check list for a b737-800
in the check list it says you need to run the apu before start-up (this i know)
now i carried on reading and on the approach check list it also states that you need to run the apu?
i thought the apu was only used when on the ground and the main engines are off??

can anyone help with this?

[LoupJr]

I'm a dispatcher for a large regional airline. I can't speak to the 737. However on the CRJ-200 and -900 we fly the APU can be used at anytime up to FL370. I suppose that the info you read meant that crews MUST operate the APU on takeoff and landing. But here's a question...what if the APU is inop? We fly with inop APUs a lot.

[Radio Homer]

i dont know thats why im asking
i know that the apu needs to be used whilst on the ground and the engines are off but not when landing or on approach as the check list suggests

[alrot]

I made some airplanes for FSX and I needed a while ago information about it to set them into my airplane models
I don't know if this may help you ,but there's information about it in this post I made last year

http://205.252.250.26/cgi-bin/yabb2/YaB ... 1289584753

[Capt.Propwash]

I'm a dispatcher for a large regional airline. I can't speak to the 737. However on the CRJ-200 and -900 we fly the APU can be used at anytime up to FL370. I suppose that the info you read meant that crews MUST operate the APU on takeoff and landing. But here's a question...what if the APU is inop? We fly with inop APUs a lot.

having worked for Delta Airlines, and Us Airways on separate occasions, most airports are equipped with "Ground Power Equipment" or power from the terminal, and "JET START" equipment.

[Radio Homer]

I'm a dispatcher for a large regional airline. I can't speak to the 737. However on the CRJ-200 and -900 we fly the APU can be used at anytime up to FL370. I suppose that the info you read meant that crews MUST operate the APU on takeoff and landing. But here's a question...what if the APU is inop? We fly with inop APUs a lot.

having worked for Delta Airlines, and Us Airways on separate occasions, most airports are equipped with "Ground Power Equipment" or power from the terminal, and "JET START" equipment.

[Capt.Propwash]

Ground Power and Jet Start machines



Ground Power connected to C-17



Jet Start connected to C17

[EVVFCX]

Hi all, doesn't the apu also provide hydraulic pumps as a backup, or at least power to run the hydraulic systems.

See the shutle landing at nightime, you can see it's apu exhaust port lighting up, otherwise daytime you can usually hear it.

[Rocket_Bird]

Not sure if its for electrical failures....

The purpose of the APU is to provide pneumatic air to the aircraft engines for engine start-up and also provide electrical power in absence of running engine-driven generators (i.e., when engines are off), and when there is no ground power provided from the ramp.

[Wildrat]

I thought the apu's on the shuttle were run with hydrazine?

[brett]

The APU was the most important switch that Captain Chesley "Sully" Sullenberger immediately pushed after hitting a flock of birds during takeoff of US Airways Flight 1549. When the engines started losing power, one by one, he did not wait for the checklist from the co-pilot to do so but pushed it because of his years of experience. This switch allowed him to control the aircraft untill final ditching.

[Rocket_Bird]

The APU was the most important switch that Captain Chesley "Sully" Sullenberger immediately pushed after hitting a flock of birds during takeoff of US Airways Flight 1549. When the engines started losing power, one by one, he did not wait for the checklist from the co-pilot to do so but pushed it because of his years of experience. This switch allowed him to control the aircraft untill final ditching.

Good fact.

I believe the on board RAT should have been able to provide him with basic controls, since it still powers the hydraulic pumps, assuming that it was working.  This was primarily how the pilots controlled Air Transat 236 (Airbus A330) when they ran out of fuel and lost both engines.  Its either through the RAT or the the APU.  Having a running APU probably helped tremendously too. 

[Capt.Propwash]

if you have the fuel, run the APU, if not... go for the RAT. Both provide limited Electrical power for the avionics, communications, and hydraulics.  then again, while Capt. Sully was trying to fly (crash) the plane, the copilot might have been trying to restart the engines..  but then again, Sully already knew what happened, and knew that a restart would be useless.  Save the people, screw the plane.