Re: FLY-BY-WIRE (AIRBUS vs. BOEING)

From:         "peter (p.j.) ashwood-smith" <petera@bnr.ca>
Organization: Bell-Northern Research Canada
Date:         17 May 95 01:06:23 
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>
>As the Boeing 777 prepares to enter service, I've been reading alot about the
>differences in philosophy behind the fly-by-wire concepts at  Boeing and Airbus.
>The more I read, the more I start to feel that Airbus may have gotten it wrong.
>Does anyone have thoughts on this.
>
>FYI:  Fly-by-wire types: A319/A320/A321, A330, A340, B777, Concorde, IL-96
>Are there any others?

   Its not the fly by wire that is the problem, hell planes have been fly by
oil for a long time. The problem is what is done with the signal that is sent
by the pilot to the control surfaces. When you start seriously altering the
output from the intended input this is where things can go wrong. Simply
stated Airbus believes that the computer knows best and its fly by wire systems
do not allow the plane to be flown outside the proper flight envelope by
the pilot, no matter what mode the software is in. Boeing on the other hand
knows the pilot is in charge and once the auto pilots are disengaged the
pilot has full control of the plane. There are two problems with the Airbus
approach. First is that the "proper flight envelope" is determined by a host
of sensors and God help you if you if they give off false signals. A faulty
AOA indicator starts to have deadly consequences. Second is that sometimes,
just sometimes the improper flight envelope is what saves your ass. Who
knows, perhaps stalling the plane with the gear up 10 feet off the ground
is the best anybody could do but the software would prevent it ...

  I have no problem with the computers doing landings/take-offs navigating
and controlling all aspects of the flight but they must be able to
be demoted to the point where they do what they are told. We are not
good enough at writing software yet to even hope to be able to produce
systems reliable enought to do the entire job properly and a human is
still necessary.

  Peter