Re: Peruvian 757 crash -- possible cause reported

From:         dtmedin@cca.rockwell.com (David T. Medin)
Organization: Rockwell Avionics - Collins, Cedar Rapids, IA
Date:         08 Nov 96 05:24:23 
References:   1 2 3
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In article <airliners.1996.2279@ohare.Chicago.COM>, kls@ohare.Chicago.COM (Karl Swartz) writes:
|> The media has been reporting that a possible cause has been identified
|> for the October 2nd crash of AeroPeru flight 603, into the Pacific
|> Ocean near Lima, the third 757 crash.  NOTE -- this is nothing close
|> to an official determination, though it doesn't sound like complete
|> bunk as did much of the early information on this crash.
|>
|> Reportedly, maintenance crews placed duct tape over the static ports
|> (which feed the airspeed, altitude indicators, and verticle speed
|> indicators) to protect them during "polishing" of the aircraft, then
|> forgot to remove the tape.
|>
|> 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.)

The problem would not be seen in airspeed while on the takeoff roll,
as the pressure in the static system would still be that at the
ground. The static system has no significant air "moving" through it
that would be blocked.  However, the altimeter and airspeed will
distort as the plane climbs, with the airspeed showing a lower (and
lowering) airspeed than actual as the plane climbs and the altimeter
staying on the ground.

Classic ground school question... Don't worry--it gets a lot of
people. Your observation would be correct if the pitot tube were
blocked...





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       David Medin            Phone: (319) 295-1862
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