Re: 767/restrictions/Atlantic Ocean

From:         rdd@cactus.org (Robert Dorsett)
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date:         06 Feb 93 14:18:11 PST
References:   1 2
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In article <LHE.93Feb6154849@anhur.sics.se> lhe@sics.se (Lars-Henrik Eriksson) writes:
>I can think of two reasons why you would need the APU in flight
>
>* If an engine flames out, the APU may be needed for restart attempts.

Probably not--the air restart envelope is usually quite generous: the movement 
of the airplane forces airflow through the engines which cause the blades to
move, etc.  All that's needed is ignition.  In fact, engine start switches
have "flight" modes, which disengage the starter mode, and simply arm the
ignition system.  

If the blades aren't moving due to windmilling effects (say, stuck by
virtue of an encounter with volcanic dust), the APU's not going to help.


>* If an engine fails, it is possible that the remaining engine cannot
>  in all circumstances provide all electric/hydraulic power and bleed air
>  that is required. The APU would help with this.

Electric: yes.

Hydraulic: no.  Maybe electric-driven hydraulic pumps.

Bleed air: *possibly*.  I would expect engine bleed air to be sufficient,
   but I could be wrong.  This sounds like something that would vary widely,
   based on mission/design.




---
Robert Dorsett
rdd@cactus.org
...cs.utexas.edu!cactus.org!rdd