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

Date:         05 Oct 98 00:26:58 
From:         Julian Scarfe <jas1@scigen.co.uk>
Organization: Scientific Generics
References:   1 2 3 4
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John Wright wrote:
> You are absolutely right. It always *seems* counterintuitive and
> therefore difficult for even experienced pilots to do, but the way out
> of the described situation (at some larger altitude than 30 feet) is to
> push the nose down. ISTR Pete Mellor in another post saying that the
> DFDR showed the pilot *trying* to pull the nose up - in which case he
> was doing totally the wrong thing. The FCS trying to push the nose down
> was trying to do the right thing.

Is this standard behaviour of the FCS, then?  The way I understand it, in
normal law, pulling back on the sidestick commands an upwards acceleration.
If the FCS needs to push the nose *down* to achieve that acceleration because
the aircraft is flying on the back side of the drag curve, will it do so?

That might explain the apparent "opposite" reaction, as Pete Mellor described
it:

"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."

So the question then is what mode was actually selected and why?
--

Julian Scarfe