Re: 767/restrictions/Atlantic Ocean

From:         raveling@Unify.com (Paul Raveling)
Organization: Unify Corporation (Sacramento)
Date:         11 Feb 93 01:38:12 PST
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In article <airliners.1993.150@ohare.Chicago.COM>, rdd@cactus.org (Robert Dorsett) writes:
> In article <1993Feb5.215714.7734@cs.ruu.nl> jaap@cs.ruu.nl (Jaap Romers) writes:
> >
> >Why are these restrictions for equipment, such as the APU, that is
> >only needed, when the aircraft is on the ground.
> 
> If you have a significant electrical failure (two generators is not uncommon)
> the APU is needed for in-flight power.  Battery power only lasts up to 
> 25 minutes or so for critical services--lighting and a radio bus.  You
> need constant AC power to run your CRT's so you can at least find a place
> to divert to.  Oceanic travel can get real lonely if none of your nav
> instrumentation works.

	It can also be critical for instrumentation needed to
	"keep the shiny side up".  (Actually many airline paint schemes
	call for keeping the shiny side down...)

	The first fatal airline accident at LAX was a 727 that lost
	all electrical power just after takeoff; its shiny side went
	directly into Santa Monica Bay.  My recollection is that
	they departed with one of their three generators inoperative,
	as was then allowed by their Minimum Equipment List.  On this
	departure they lost the second generator, the load transferred
	to the third, and the third went offline because it couldn't
	handle the load alone.

	The sudden loss of power was fatal problem because they were
	departing into IMC at night.  This accident prompted immediate
	attention to MELs, plus some scrutiny of load sensitivity.
	I presume the same issues have had even more intense examination
	for FBW aircraft, and would guess that they have reasonably
	sophisticated controls for automatic load shedding.  Perhaps
	someone who really knows could comment on this.


------------------
Paul Raveling
Raveling@Unify.com