Danny Dot wrote:
In about 1990 Airbus did low pass at the Paris airshow and lost the plane.
I recall it had something to do with the throttle software thinking the
pilots were in landing mode and "refused" to go to high power for the
go-around.

Yes, the computers did think the pilot was landing, but the crash was
caused by his being too low and slow. (See other posts for more info
on the latter.)

The Airbus software has modes where its flight control computer laws
are quite different. Some of those computer laws are divided into
Ground, Flight and Landing (Flare) phases.

One claim is that he was trying to demonstrate that the airplane was
unstallable. He had reportedly done this demonstration several times
before at a slightly higher altitude, and it had always worked. Why?
Because the Airbus has what's known as Alpha Protection (pitch related)
and Alpha Floor (thrust related). Too little thrust, at too high an
angle of attack (AOA), and its computers automatically kick in and
override the pilot.

The reason the automatic protection didn't work this time was because
he went below 100', so the computers switched to Landing Mode. That
doesn't mean they do an autoland. It means they think the pilot is
landing the plane and their rules change. The Alpha Floor is disabled
so that a landing is possible at all. By the time the pilot advanced
the throttles himself, it was too late.

In addition, another Landing Mode kicks in when the Bus passes below
50' going down to 30', as he did. The computer starts changing the
stick reference for landing, so that if you have the stick pulled
back', that position soon becomes the neutral spot. This is supposed
to force the pilot to pull back more for flaring.

Regards, Kev

Easy Reading Version of Airbus Flight Control Laws (for Pitch Mostly)
http://www.airbusdriver.net/airbus_fltlaws.htm

Airbus Training Details with couple of pages on Laws
http://www.chipsplace.com/helpful/Ai...320TOC.htm#TOC

FAA Special Regs Example for Laws Feedback
http://www.washingtonwatchdog.org/do...r01jy02-3.html

Interesting incidents:

.... AOA protect problem (caused constant pitch up with resultant TCAS
alert)
http://www.rvs.uni-bielefeld.de/publ...pdf_501275.pdf

.... AOA protect system stopped nose-up for go-around and allowed
aircraft to hit runway
.... Afterwards, the rate-of-AOA-change logic was removed from the
software
http://aviation-safety.net/database/...?id=20010207-0