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

Date:         21 Sep 98 03:57:22 
From:         rdd@netcom.nospam.com
Organization: Netcom Online Communications Services (408-241-9760 login: guest)
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In article <airliners.1998.1455@ohare.Chicago.COM> jbartolo@pacbell.net writes:
>PS2727 wrote:
>I'm not an expert on all the details of this incident, but I thought
>that regardless of the computers and flight control system, if you're at
>the far end of the power curve (max power and high AOA) the only thing
>you have left is to lower the nose to gain airspeed. If you're at 30
>AGL, you have no options.

So here's a question.  The A320's flight control computers aren't performing
finite element analysis every second of the way to determine maximum
performance (not on 386's and MC68000s, at least :-)).  They're dealing
with look-up tables, with values determined to represent maximum performance
in a laboratory.  Considering this, no doubt alpha-max is determined to be a
value *conservatively* defined NOT to be more than true alpha-max.  This
value no doubt would need to consider normal wear and tear, additional
drag sources, etc.  There will always be compromises introduced by the
flight testing and development process.

Therefore, even though, *academically*, your argument is correct, in
*reality*, there very likely was some energy to be goosed out of the
(perfectly functional and normally operating) system.

This is one reason why the solution to low-energy accidents isn't
protecting the airplane from the flight crew--it's better feedback and
control systems.  Let the crew understand what's going on and let them
do what's necessary for that situation.

But all this is speculation.  Perhaps someone from AI would comment on the
design of their higly proprietary flight control system?  No pilots:
engineers. :-)

This in no way excuses Asseline from flying the airplane in such a way
that he was so low, at such a high deck angle, that he couldn't see the
trees he was about to fly into.  Yes, the energy reserve might have been
usable.  But he shouldn't have been in that situation to begin with.
Just like the Cali 757 crash.  Who cares if the 757 doesn't have automatic
spoiler retraction on TOGA power, or whatever malicious rubbish the Boeing-
bashers were spreading around.  The root cause of that crash went to the
design and usage of the FMS and a variety of failures which resulted in
the airplane being flown on the wrong track and profile.  That's where
engineering attention should be focused.  Give the pilots the tools they need
to enhance situational awareness and provide them with standardized methods
of flying the airplane.  Heroic-measures systems should truly be the lowest
priority.

--
Robert Dorsett                         Moderator, sci.aeronautics.simulation
rdd@netcom.com                         aero-simulation@cactus.org

           "Bother," said Pooh when his engine quit on take-off.