Hey FMC,
The SHUTDOWN checklist says APU BLEED AIR SWITCH 'ON'. The SECURE checklist thereafter says PACKS 'OFF'. Nothing is mentioned about the APU BLEED AIR SWITCH. So you could leave it 'ON'. AOM (FCOM) vol. 1, normal procedures.
The APU BLEED AIR VALVE is indeed pressure operated and DC controlled. When the APU is 'OFF' the APU BLEED AIR VALVE is closed (no pressure). BATTERY 'ON' is all you need to start the APU. The position of the APU BLEED AIR SWITCH has nothing to do with this, it could be 'OFF' aswell (theoratically). AOM (FCOM) vol. 2, chapter 2.
Regarding the 1 minute. After APU start it must be operating for 1 minute before switching PACK(S) 'ON', on the CLASSIC and the NG. On the NG operate the APU for 1 minute with no bleed air load (PACKS 'OFF') prior to shutting it down. AOM (FCOM) vol. 2, chapter 7. Although I got a memo, for the CLASSIC, saying something else.
All the above is not the law, but when your instructor, cpt or examiner asks, you have at least something on paper.
About the rear service door CLOSED with APU running I couldn't find anything written. I assume it is just good practice.
PS. After APU shutdown indeed wait for approx. 2 minutes (after the APU GEN OFF BUS light extinguishes) before switching the BATTERY 'OFF', on the NG. On the CLASSIC, 20 seconds (APU inlet door closed). AOM (FCOM) vol. 1, normal procedures.
Take care.
Last edited by Alaskan Timber; 11th Dec 2004 at 19:53.