Discussion:
What happened to AF 447
(too old to reply)
John R. Levine
2011-12-12 01:35:18 UTC
Permalink
Don't recall whether this has been mentioned here, but this Popular
Mechanics article has extensive transcripts from the pilots' conversation.

Summary: an inexperienced junior officer misunderstood what the
instruments were telling him, and stalled and crashed an entirely flyable
airplane. Read all about it.

http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877-2

Regards,
John Levine, ***@iecc.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. http://jl.ly
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JF Mezei
2011-12-12 08:53:26 UTC
Permalink
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.
http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877-2
From the BEA web site (this is in french only. The BEA issued a press
release on Oct 13:

http://www.bea.aero/fr/enquetes/vol.af.447/com13octobre2011.pdf


##
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 d’une 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.
##

Short translation:

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
limits.

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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Miles Bader
2011-12-13 00:31:35 UTC
Permalink
Post by JF Mezei
I don't think that the Boeing vs Airbus FBW philosophy is at issue here
One scary exception that I saw pointed out on a G+ thread:

At one point during the AF447 event, the two co-pilots were apparently
pushing their joysticks in _opposite_ directions (one up, the other
down), but:

(1) the airplane _averaged_ the two joystick inputs (resulting in
basically nothing happening in this case)

(2) ... but there's no tactile feedback from the joystick that
indicates what the other pilot is doing, so the pilots may not even
realize this is happening

Supposedly (according to the thread comment) the Boeing yoke design,
even in a FBW aircraft, is much more similar to a mechanical control,
in that the yokes are linked somehow, resulting in obvious mechanical
feedback on what the other pilot is doing.

[I certainly can't vouch for the technical accuracy of this;
corrections obviously welcome.]

-miles
--
Resign, v. A good thing to do when you are going to be kicked out.
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JF Mezei
2011-12-13 07:00:59 UTC
Permalink
Post by Miles Bader
(1) the airplane _averaged_ the two joystick inputs (resulting in
basically nothing happening in this case)
Baed on my understanding, this is false. It is one or the other. There
is a clear change of "command" when you press a button, you get control.
And piots will verbally announce they are taking control. (and this was
annoucned at one point according to the BEA transcripts).

This forces pilots to communicate their intentions to pilot.
Post by Miles Bader
(2) ... but there's no tactile feedback from the joystick that
indicates what the other pilot is doing, so the pilots may not even
realize this is happening
You're supposed to always have only one pilot flying. And a clear change
of responsability when it changes. If the PNF is not happy with the PF,
he needs to talk to the PF to tell him what to do, or announce he is
taking the controls.
Post by Miles Bader
Supposedly (according to the thread comment) the Boeing yoke design,
even in a FBW aircraft, is much more similar to a mechanical control,
in that the yokes are linked somehow, resulting in obvious mechanical
feedback on what the other pilot is doing.
It ia reproduced by motors, not mechanical linkages. I am not sure
about the philosophy of who is in control though. Is one master and the
other slave (with a switch similar to the airbus concept that switches
naster/slave) or are both yokes always "masters" with one pilot able to
push in the opposite direction of the other to counter his actions ?

Based on the snippets from the popular mechanic article, it appears both
pilots were clueless and neither suggested ending the nose up attitude.
After a while the captain did verbally advise nose down but I guess it
was too late.

I'd have to review the BEA report to see if they did detect nose down
command towards the end.



The popular mechanic article certainly paints a cockpit environment that
was not described in the "factual" BEA reports. Interesting that the
BEA chastises the author for publishing incomplete transcript taht
gives incomplete pictire, but the agency is equally guilty of choosing
what factual information to omit in order to NOT paint an accurate
representation of what happened.

In particular: captain entering and asking what is happening, and both
stating that they are losing/have lost control of aircraft, and later,
captain ordering nose down. And one pilot realising they will crash.

BTW, they expect to produce another interim report focusing on human
factors sometimes in december.


From a systems point of view, I could see them suggesting that the 3
pitots be declared "mission critical" and be of at least 2 different
brands so that a design problem of one brand wouldn'r leave pilots
without any speed information.


From a training point of view, if 2 pilots failed to detect a stall
condition, there is something very wrong. It is quite possible that
because they are trained to avoid storms, they may have insufficient
experience dealing with flying through a storm.

And when flying through bad conditions, I would expect the PNF to look
at gauges and verbally report status to PF, ESPECIALLY when there is
some instrument failure.
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Miles Bader
2011-12-13 08:10:40 UTC
Permalink
Post by JF Mezei
Post by Miles Bader
(1) the airplane _averaged_ the two joystick inputs (resulting in
basically nothing happening in this case)
Baed on my understanding, this is false. It is one or the other. There
is a clear change of "command" when you press a button, you get control.
According to the story, there are various modes, and ... for whatever
reason, it was in "average" mode; I dunno what the default would be.

[Actually as long as they're following normal operating procedures,
with only one person flying at a time, an "average mode" would work
pretty well, as it would allow the pilots to switch roles without
flipping a switch, and that ability might be important in an
emergency.]
Post by JF Mezei
And piots will verbally announce they are taking control. (and this was
annoucned at one point according to the BEA transcripts).
This forces pilots to communicate their intentions to pilot.
Post by Miles Bader
(2) ... but there's no tactile feedback from the joystick that
indicates what the other pilot is doing, so the pilots may not even
realize this is happening
You're supposed to always have only one pilot flying. And a clear change
of responsability when it changes. If the PNF is not happy with the PF,
he needs to talk to the PF to tell him what to do, or announce he is
taking the controls.
That's what you're _supposed_ to do, but it's pretty clear that when
things started to get hairy in the AF 447 incident, this regime broke
down. Maybe because of the intense stress of the situation, maybe
because there were two co-pilots flying rather than a clear pilot and
co-pilot, etc.

Having an obvious and intuitive physical/tactile indication seems the
sort of thing that would be advantageous in precisely this sort of
stressful and unexpected situation.
Post by JF Mezei
It ia reproduced by motors, not mechanical linkages. I am not sure
about the philosophy of who is in control though. Is one master and the
other slave (with a switch similar to the airbus concept that switches
naster/slave) or are both yokes always "masters" with one pilot able to
push in the opposite direction of the other to counter his actions ?
I'm not sure, but my impression is that it is the latter. That would
seem to make it sort of similar to Airbus's "average mode," but with
tactile feedback to make conflicts obvious.
Post by JF Mezei
BTW, they expect to produce another interim report focusing on human
factors sometimes in december.
Hopefully that will shed some additional light on these matters.

-Miles
--
「寒いね」と話しかければ「寒いね」と答える人のいるあったかさ [俵万智]
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matt weber
2011-12-13 22:35:51 UTC
Permalink
On Mon, 12 Dec 2011 03:53:26 -0500, JF Mezei
Post by JF Mezei
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.
http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877-2
From the BEA web site (this is in french only. The BEA issued a press
http://www.bea.aero/fr/enquetes/vol.af.447/com13octobre2011.pdf
##
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 d’une 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.
Temperature is indeed involved, but it is in the opposite direction. I
don't think it can ever be too cold to climb in the temperate
latitudes and below. Lower temperature means reduced density altitude,
i.e. the aircraft will behave as if it is LOWER than it actually is.

This is sometimes a problem in Anchorage, where the low temperatures
and a strong high pressure system can push the barometric pressure
above the limit you can dial into an altimeter. When it happens, the
airport has to close.

A few years ago an A340 took off from a taxiway at ANC in winter. The
only reason they got away with it was between the barometric pressure
and the temperature, the density altitude was about -3500 feet! On a
standard day they would ended up in the water off the end of the
runway.Aircraft (at least the engines) generally perform much better
at low temperatures.

It can be too hot to climb however. About 20 years ago I was on the
flight deck of a 747-200 over the Madagascar Channel at the maximum
altitude for the weight (FL390), and we ran into some very bad
weather. Between the downdraft we hit, and the sudden temperature
increase (about 15C), we fell several thousand feet in a very short
time.
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