Its not a stupid question at all. ETOPS rules required that the APU be "started and ready for immediate use" before entering the ETOPS operation area, and remain that way until you've exited the ETOPS operation area. Its for added redundancy for both an electrical source and bleed air source in the event you lose a engine GEN or bleed (or just an engine all together) while flying under ETOPS. From the manual....APU OPERATION-ETOPSThe 737NG certification requires the APU to be operating during the portion of the flight conducted in the ETOPS area (EEP to EXP). ETOPS flights will not cross the EEP without the APU running and the APU Generator available for immediate operation. If the APU fails prior to the EEP, the Flight Crew will divert back to the departure airport or an adequate alternate. Anyone let me know if I've missed something, but I think that's it.

Thanks for the info.Well I guess I'll have to start turning on the APU when I do the KSEA - PHNL run in an Alaska Air 737-800. But, while I really get the need for the redundancy how much extra fuel burn does that redundancy cost.

Thanks for the info.Well I guess I'll have to start turning on the APU when I do the KSEA - PHNL run in an Alaska Air 737-800. But, while I really get the need for the redundancy how much extra fuel burn does that redundancy cost.

Well I'm looking at an old release for a SEA to KOA flight, and they've got the total APU fuel burn down as 582 lbs. That's not much considering the total pre-taxi fuel load is 45,523 lbs.

Thanks for the great info and insight to some of ASA's ops. Without violating any NDA's or Corp policies, is there a generic manual / procedures as a resource on how to calc the minimum fuel for an ETOPS flight? Am I correct that you have to calc half the flight at FL100 to account for a possible loss of cabin pressure?RegardsMK

Good questions, I'll have to look into both. Give me a time to research it and I'll see if I can come up with, or just do a simple write up based on whats in the ETOPS planning section if the FOM. ETOPS fuel planning is just FAA regulatory dispatch stuff, nothing really top secret. If our friends at PMDG wouldn't mind, I'd still love some feedback on the original question of this tread.

You can input the special custom waypoints yeah - MD-11 had the ability to do this too btw. (guessing not a lot of people have ever used that function)

That's great!!!! Thanks Ryan.