Re: ETOPS Question

Date:         20 Nov 97 02:53:41 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>One other point.  The APU cannot be operated in the air on the
>B747-100/200 series...of running during takeoff, the APU on the B747-400
>can be used upto approx 15-20,000 ft.

The first part of the definitely is not true.  From the NTSB report on
the February 24, 1989, UA 811 accident, which involved a 747-122:

   The auxiliary power unit (APU), which was used during the takeoff,
   was shutdown shortly after making the initial power reduction to
   climb thrust.

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.

Karl Swartz	|Home
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