Post by John R. Levine
Don't recall whether this has been mentioned here, but this Popular
Mechanics article has extensive transcripts from the pilots' conversation.
From the BEA web site (this is in french only. The BEA issued a press
release on Oct 13:
13 octobre 2011
A la suite de la publication du livre "Erreurs de pilotage, Tome 5",
signe? par Jean-Pierre Otelli, le BEA a constate? qu'un chapitre sur
l'accident de l'A 330- 203, vol Rio-Paris, AF 447 survenu le 1er juin
2009, comportait une partie dune transcription litte?rale de
l'enregistrement phonique dans le cockpit (CVR).
Le BEA condamne fermement la divulgation de cette transcription qui est
une violation de l'article 14 du re?glement europe?en en date du 20
octobre 2010, entre? en vigueur le 2 de?cembre 2010.
The BEA strongly condemns the publication of transcripts which violates
article 14 of the european rules/laws....
What that popular mechanics site does not mention is the fact that the
"stall" alarm came on and off multiple times. At first, because pitots
were in the process of failing. Once they were declared failed, the
alarm ended. Then, pitots became operational again, and stall alarm
sounded again (likely announcing a real stall, but likely dismissed as
another false alarm).
The BEA is correct in complaining that this excerp of transcripts
doesn't contain the whole story. Discussions on th failed pitots would
be very important since they may confirm that they would igore all stall
warnings because of the unreliable pitots, or perhaps provide insight on
whether they were aware that climbing a few more thousand feet would
bring aircraft dangerously close to ts limits based on current weight.
In fact, the conversations prior to the first alarm are more important,
trying to understand why they decided to gro through instead of go
around the storm(s).
In the official preliminary reports, there was discussion about climbing
to avoid upcoming turbulence and a mention that it was too cold to climb
yet. Not sure what temperature has to do with how high a plane can fly
at a certain weight. But it *seems* to indicate they were aware aircraft
was near its limit for current weight.
If they couldn't trust the stall alarm because the pitots had gone
wacko, then the PNF should have been monitoring altitude gauges all the
time, especially since it appears they knew they were taking the
aircraft higher than it should have.
So it *appears* that they ignored the aircraft's performance limits, and
underestimated the dangers of taking an aircraft to higher altitude
especially once your lose instruments and end up in alternate law.
Perhaps this is a danger of automation where pilots forget about their
plane's limits, expecting the computer will protect the plane from those
Whether the training issue is imilited to AF or is the shape of things
to come with a new generation of pilots who never flew old manual
aircraft like 737s will be interesting to see. Either way, there may be
some interesting recommendations on changes to pilot training.
The fact that one of them even lowered thrust from TOGA to idle midway
during the fall also indicates they didn't consider "stall" to be an
issue. Maybe they thought they could reduce effects of turbulence by
slowing down. Maybe they really thought it was a big downdraft that was
bringing them to lower altitude.
I don't think that the Boeing vs Airbus FBW philosophy is at issue here.
In both cases, loss of valid pitot data would prevent the computer from
detecting stall and/or issue spurious stall alarm.
Having said this, I am not a pilot, but I know that if you are unable to
maintain altitude with nose up altitude, you have to bring nose down and
increase airspeed. Why thrust was lowered to flight idle midway through
the fall is beyond me.
What I find astounding is that neither pilot realised they were
stalling, and their comments were akin to "why the heck is happening".
Also not mentioned in that popular mechanics article is that the plane
was "violently" swaying left and right. Was this due to the fall, or was
it due to the storm ? Pilots may have though it was the storm. And this
would have also caused them to focus on stabilising aircraft in a 2D
mode instead of thinking about drop in altitude.
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