Re: A-320 crash in Warsaw

From:         wangermn@phoenix.princeton.edu (John Paul Wangermann)
Organization: Princeton University
Date:         22 Oct 93 01:05:13 PDT
References:   1 2
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In article <airliners.1993.651@ohare.chicago.com>,
Robert Dorsett  <rdd@rascal.ics.utexas.edu> wrote:
>In article <airliners.1993.650@ohare.Chicago.COM> adam@kurdel.harvard.edu (Adam Dobrzycki) writes:
>>The plane happened to land during (or shortly after) a short, but very
>>heavy rain. 
>
>The initial DFDR analysis indicates they touched down at about 700 meters,
>or 1/4 down the runway.  The normal touch-down zone is 300 meters.
>
>
>>There were random gusts of wind. Some planes landed safely
>>before the fatal A-320 though, and other landed later, after short
>>(~30 min.) break caused by the crash.
>
>Provided they were on the ground, I don't think the wind was particularly
>relevant in this crash.  On the first day, an amateur organization in 
>Germany ("Cockpit") was apparently defending the airplane against early 
>suggestions that the plane had accelerated, taken off, and stalled out: in 
>an unstallable airplane, windshear seems a likely culprit.  It seems they 
>jumped the gun. :-)
>
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The conditions as described (sudden downburst, strong gusting winds in
changing directions) are usually strong indications of microburst
activity.  If a microburst is hit early in an approach, the aircraft
will balloon above the glideslope (increassing headwind).  Then as it
passes the core the headwind becomes a tailwind, the aircraft loses
airspeed and height rapidly.  While in the past, crashes have occurred
because aircraft came down early because of this effect, it is entirely
possible that as the aircraft came in to land it was still in the
headwind part of a microburst, hence ballooning above the intended
trajectory to touchdown.

Can you say why yoyu don't think the wind seems relevant in this case?
Without better information, I'd say microbursts (windshear) seem a very
prbable cause - at least of the very late touchdown.

John


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John P. Wangermann                  wangermn@phoenix.princeton.edu

Dept of Mech and Aero Eng.               (609) 258 5340
E Quad
Olden St
Princeton NJ 08544
USA
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