Re: ETOPS Question

Date:         21 Nov 97 01:59:52 
From:         Seth Dillon <>
Organization: Delta Air Lines
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Karl Swartz wrote:
> Obviously the APU can be used in the air if running during takeoff
> even on a 747-100.  The limitations may be similar to those you note
> for the 747-400.
> >Its doubtful it can be started in the air.
> I'm pretty sure none of the Boeing airliners have APUs certified for
> re-start once cruising altitude has been reached, primarily because
> of problems getting it lit after an extended cold-soak.  That doesn't
> imply that it *can't* be started in the air, and perhaps at lower
> altitudes it might work if you had to try it.

The Garrett GTCP 331-200ER is rated to supply pneumatic pressure up to
19,000 feet, and electrical power up to the aircrafts service ceiling.
The APU is can be started up to 43,100 feet in a cold soaked condition.
This is from the 767-300ER maintenance training manual.

On of the systems required for ETOPS is a fully operational APU, both
elec and air capability.  Our airline routinly performs in flight APU
starts after a few hours at cruise to verify the integrity of the APU.
It should be noted that this is done only on west bound legs, as we our
a US based carrier.  If the APU fails to start, the aircraft is then
downgraded to non-ETOPS until repair or replacement of the APU.