Re: Habsheim accident (was: Re: Airbus Safer?)

Date:         09 Sep 98 04:12:19 
From:         Pete Mellor <pm@csr.city.ac.uk>
References:   1 2 3 4 5 6 7
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proctor@sequence.stanford.edu (Michael Proctor) wrote on 02 Sep 98 01:07:54:-
> > I seriously doubt you can produce any evidence to substantiate this
> > theory.  The pilots waited too long to pull up, but to blame it on their
> > ignorance of the terrain is neither credible nor consistent with any of
> > the reports on the accident which I've encountered.
>
> I always wonder about the argument that, if there hadn't been computer
> aided control of the aircraft, the pilots efforts to pull the aircraft up
> would have most likely caused a stalled resulting in a much more
> destructive accident then the controlled descent into some trees, that
> resulted in only three deaths.

That is the official view of Airbus Industrie, as published in their
own reports issued in response to public criticism. AI claim that the
aircraft was in alpha-protection mode, which would prevent the pilot
increasing the AOA beyond a certain limit. Asseline claims that, having
(unknown to him) passed below the 50 foot AGL, the A/C was in landing
mode, in which the programmed flight laws impose a certain rate of
derotation, which the pilot has to counteract to achieve flare.
Nobody knows for certain which mode it was in, since the mode changes
are not recorded on the DFDR.

It is not disputed that, in the final few seconds of flight, the pilot
was applying nose-up stick while the FCS was simultaneously applying
nose-down elevators. This is apparent from the DFDR trace in the
accident report.

The main point about the presence of the on-board computer-based
flight control system is that, without it, nobody would have
ever dreamed of trying such a stunt, which was performed precisely
in order to demonstrate the safe flight envelope protection features
of the FCS.

Peter Mellor, Centre for Software Reliability, City University, Northampton
Square, London EC1V 0HB, UK. Tel: +44 (171) 477-8422, Fax: +44 (171) 477-8585
E-mail: p.mellor@csr.city.ac.uk, Web: http://www@csr.city.ac.uk/
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