Re: Peruvian 757 crash -- possible cause reported

Date:         10 Nov 96 04:52:42 
From:         Keith Barr <barr@nilenet.com>
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In article <airliners.1996.2279@ohare.Chicago.COM>,
Karl Swartz <kls@ohare.Chicago.COM> wrote:
>This would explain the complete instrumentation failure, though it
>fails to explain why the pilots did not recognize a problem with the
>airspeed indicator during takeoff and either abort the takeoff or
>immediately return to the airport.  (The pilots first reported
>problems and requested a return to Lima about five minuts into the
>flight.)

A pitot-static system failure in a large aircraft should not be an
occurance that causes an accident.

You can live without your airspeed indicator by knowing what power settings
and approximate pitch attitudes will give you what you are looking for
(i.e.: set 2800 pounds fuel flow, 5 degrees nose up, flaps 15, and you get
170 knots and level flight--these are for a 737-200 in the low 90,000 pound
range at 7000 feet MSL).

In a 757 you have a radar altimeter, which should be enough to keep you out
of the water anyway.  RA's generally don't work very high (although the one
on the DC-8 I have spent a lot of time on was accurate into the 30,000 foot
range).

You can live without your vertical speed indicator.  Your power and pitch
settings will tell you what you need to know (from the above example, if
you go to flaps 30, gear down, you will slow to about 145 and you will be
decending at about 750 feet per minute).
--
Keith Barr                                     COMM AS&MEL/IA/A&IGI AERO/EIT
barr@aerosys-eng.com                               AeroSys Engineering, Inc.
http://www.nilenet.com/~barr                      Westminster, Colorado, USA