Re: The Scoop on the A330 Accident.

From:         Peter Ladkin <Peter.Ladkin@loria.fr>
Date:         09 Jul 94 16:58:51 
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>>  This is the
>> first case, to my knowledge, in which this has been proved to have
>> happened to Airbus aircraft, without any concomitant pilot error.
>
>Warsaw? 

At Warsaw, the pilots landed with over 20 kts of excess speed,
although still within range, in part because of the meteo.
Furthermore, according to David Learmount they greased it on, rather
than thumping it on which would have compressed the squat switches and
probably spun the wheels up, thus triggering the braking system. Maybe
not pilot *error* as such, depending on your point of view, but pilot
decisions certainly contributed. But in Toulouse on Jun 30, not.

>> At about
>> 90 kts, 28kts less than V_{mca}, the aircraft departed [`part en
>> decrochage'] to the left with an angle of roll [`angle de roulis']
>> which attainted 110 degrees.
>
>At about 90 kts, 28kts less than V_{mca}, the aircraft stalled to the left 
>with a bank angle which attained 110 degrees. 

It rolled and probably yawed to the left (that's not in the article),
and at least one wing stalled. The phrase `stalled to the left' has no
meaning. A stall is a loss of lift. The initial movement during a
stall is called a `departure' or a `break'.  To be accurate (and
pedantic), one should say `departed [broke] to the left in a stalled
configuration'.

>"decrochage" = "stall". Typically, when an aircraft stalls, due to random 
>asymmetries of attitude, etc., one wing goes first. It looks as though the 
>left went first in this case. 

It's not quite accurate to say that `typically one wing goes first'.
Both commercial air transports and small planes may stall either
straight ahead, or drop off one wing first, depending mostly on
aircraft type.  In flight tests of commercial transports, one often
reads of aircraft dropping straight ahead in a power-off stall.  In
the case of the A330, the reasons why the left wing dropped off first
are (a) there's a `blown-wing' effect on the right wing, a faster
airflow, caused by the airflow around the right engine which was at
full power; and (b) there's a huge yawing moment caused by that BIG
engine on the right at full power, and the yawing motion means the
left wing is moving more slowly than the right wing. I would guess
that (a) is more significant.

Cheers,
Peter.