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Air France Jet Crash

by DaivdBender
Tags: crash, france
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Mech_Engineer
#19
Jun3-09, 10:14 AM
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Whatever happened to the plane, it had to have been so chatastrophic that all communications and flight controls failed such that the pilots could not control the plane AND could not radio out a mayday. Possibly massive wind shear causing the airframe to break apart, but it seems to me that lightning is unlikely due to the number of double and triple redundant systems governing critical systems such as flight controls.
mgb_phys
#20
Jun3-09, 11:26 AM
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Quote Quote by Vals509 View Post
also just as a guess. could the plane have suffered engine failure while in the storm. after all, there were electrical problems and i think the engines provide some power and also the engines i believe maintained presurisation and it is thought that there was a cabin loss of pressure
The engines normally provide all the electrical power, there is an emergency wind powered generator that deploys automatically if they fail. Losing both engines in cruise isn't a disaster - a 747 glided for 15minutes after losing all 4 engines when flying through a dust storm. Another A330 that ran out of fuel flew for 20 minutes before landing in the Azores.
The engines are used to pressurize the cabin and provide the heating and AC but the air doesn't suddenly rush out if they stop.

The sequence of events and debris look like it broke up at altitude but it's going to take the recovery of more evidence to work out why.
Borg
#21
Jun3-09, 04:55 PM
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Quote Quote by mgb_phys View Post
The engines normally provide all the electrical power, there is an emergency wind powered generator that deploys automatically if they fail. Losing both engines in cruise isn't a disaster - a 747 glided for 15minutes after losing all 4 engines when flying through a dust storm. Another A330 that ran out of fuel flew for 20 minutes before landing in the Azores.
The engines are used to pressurize the cabin and provide the heating and AC but the air doesn't suddenly rush out if they stop.

The sequence of events and debris look like it broke up at altitude but it's going to take the recovery of more evidence to work out why.

I agree. The plane that crashed into the Hudson in January lost both engines but that didn't stop them from performing a controlled crash landing and communicating with the control tower.

I've read reports that the automated messages from 447 were sent over a 4 minute time span. But, I've only read that the plane depressurized and had electrical failure - nothing about the order or timing. Has anyone heard anything more about the sequence, timing and content of the messages?
Borek
#22
Jun3-09, 05:13 PM
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According to Polish media (they claim to quote some Brazilian media) pilot reported that they are going through thunderstorm. 10 minutes later plane systems reported that autopilot has been switched off, reserve power system has been engaged and systems required for plane stabilization have been damaged. Other reports followed. Three minutes later came report about pressure loss and electrical failures.

Note that this was first translated from Spanish to Polish, then from Polish to English, and neither translation was done by someone aware of proper terminology.
Borg
#23
Jun3-09, 05:19 PM
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Quote Quote by Borek View Post
Note that this was first translated from Spanish to Polish, then from Polish to English, and neither translation was done by someone aware of proper terminology.
My wife is Russian. I definitely know how things get lost in translation...
mgb_phys
#24
Jun3-09, 05:31 PM
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Quote Quote by Borg View Post
I've read reports that the automated messages from 447 were sent over a 4 minute time span. But, I've only read that the plane depressurized and had electrical failure - nothing about the order or timing
from http://aviation-safety.net/database/...?id=20090601-0
starting at 02:10 UTC, a series of ACARS messages were sent -automatically- from the plane. The first message indicated the disconnection of the autopilot followed and the airplane went into 'alternate law' flight control mode. This happens when multiple failures of redundant systems occur.
From 02:11 to 02:13, multiple faults regarding ADIRU (Air Data and Inertial Reference Unit) and ISIS (Integrated Standby Intsruments System) were reported. Then on 02:13 the system reported failures of PRIM 1, the primary flight control computers that receive inputs from the ADIRU and SEC 1 (secondary flight control computers). The last message at 02:14 was a 'Cabin vertical speed' advisory.
The ACARS is a SMS message like system that reports flight information and all sorts of diagnostic and system status messages. It lets the airline know of any technical problems that might need looking at when the plane lands. It's completely automatic and each short message only takes a fraction of a second to transmit so it could have managed to send messages as long as the systems had backup power and the antennae was connected - even if the plane was in pieces.
Borg
#25
Jun3-09, 06:08 PM
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Thanks for the great link. This link from that page states that the final 'cabin vertical speed' message indicates that the plane was mostly intact at that time.
Air France Flight AF447. The Last 4 Minutes. / Tim Marshall

I found this page that describes what Alternate Law means:
http://www.airbusdriver.net/airbus_fltlaws.htm
Phrak
#26
Jun3-09, 06:24 PM
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Quote Quote by Borek View Post
Can't find it - can you please give more detailed pointers?
Sorry about that Borek. It's the same wikipedia article that borg has in post #34.

According to the article, which I've reformatted:

The last contact with the aircraft was at 02:14 UTC, four hours after take-off, when its avionics automatically transmitted several messages via ACARS indicating multiple systems failures.

1) The first of these messages, at 2:10 UTC, reportedly indicated that the autopilot had disengaged and the fly-by-wire computers had switched to an alternate program used in the event of multiple system failures.

2) Next, the aircraft transmitted several messages indicating failures of

A) the Air Data Inertial Reference Unit,

B) the Integrated Standby Instrument System (a backup system providing basic flight instruments), and

C) the master units of the primary and secondary flight control computers.

3) The final message received, at 02:14 UTC, indicated a possible cabin depressurization at location 334′40″N 3022′28″W / 3.5777N 30.3744W / 3.5777; -30.3744.
Phrak
#27
Jun3-09, 06:29 PM
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What elecrical failure?? The first fault transmitted by ACARS, according to the Wikipedia article, was multiple subsystems failures. This appears to have morphed into “electrical circuit malfunction.” For all we know the tail was ripped off along with it's remote sensors.

Edit: OK, nevermind the tail ripping off. These subsystems are probably located in the bays beneath the cockpit.
FredGarvin
#28
Jun3-09, 08:22 PM
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It all fits pretty well into an extremely unlucky lightning strike scenario....except the cabin depressurization.

No one has mentioned the "B" word yet.
mgb_phys
#29
Jun3-09, 08:29 PM
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Quote Quote by FredGarvin View Post
It all fits pretty well into an extremely unlucky lightning strike scenario....except the cabin depressurization.
The message could mean the airframe had broken up .

No one has mentioned the "B" word yet.
Especially since it's about the only other cause of no-warning loss of an aircraft in cruise.
russ_watters
#30
Jun3-09, 09:59 PM
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Quote Quote by FredGarvin View Post
It all fits pretty well into an extremely unlucky lightning strike scenario....except the cabin depressurization.
What about the wind shear and breakup idea? Would the tail ripping off (like that one in 2001) cause such flight control failures? Are these flight control failures certain computer failures or could they be the computer's necessary reaction to a change in aircraft controllability or loss of sensors (whether electrical or physical)?

From what I understand, there are two debris fields, several miles apart. And 4 minutes to crash from 35,000 feet is pretty quick, about 100 mph. That's probably about the terminal velocity of a falling chunk of airplane. Could wind shear have torn off the tail or a wing (or two?)?
No one has mentioned the "B" word yet.
Due to the weather element, I don't know that it needs to be part of the discussion (yet). The media has shown unusual restraint.
FredGarvin
#31
Jun3-09, 10:02 PM
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The storm causing a break up is a good idea considering what happened in the Rockaways to an A320. That happened due to rapid course corrections. I wonder what they think could happen with 100 mph shear winds hitting the tail section?

I don't know that aircraft's systems at all. I wonder what systems are routed through the tail end.

Ugh. What a way to go.
russ_watters
#32
Jun3-09, 10:03 PM
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Quote Quote by mgb_phys View Post
Especially since it's about the only other cause of no-warning loss of an aircraft in cruise.
Given that the lightning stike thing thing hasn't happened in 40+ years, any other resonable scenario must be considered. There are at least a couple of other reasons why a plane might suddenly plummet from a seemingly normal cruise:

-Fuel tank explosion, a la TWA 800
-Fire, a la ValuJet
russ_watters
#33
Jun3-09, 10:09 PM
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Quote Quote by FredGarvin View Post
The storm causing a break up is a good idea considering what happened in the Rockaways to an A320. That happened due to rapid course corrections.
...breaking off the vertical stabilizer.
I wonder what they think could happen with 100 mph shear winds hitting the tail section?
I'm also wondering if a microburst hitting a plane at cruising speed could cause enough of a vertical (negative) g-force to rip off the wings. That would have the effect of a sudden -20 degree angle of attack change.
I don't know that aircraft's systems at all. I wonder what systems are routed through the tail end.
Certainly sensors associated with rudder and elevator position at the very least. If the flight control computer doesn't see an input from one of them, could it revert to another operating mode?
mheslep
#34
Jun3-09, 10:35 PM
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Quote Quote by FredGarvin View Post
...No one has mentioned the "B" word yet.
I thought the fact that the flight avionics had the opportunity to radio home about several electrical problems made that somewhat unlikely.
russ_watters
#35
Jun3-09, 11:03 PM
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Quote Quote by mheslep View Post
I thought the fact that the flight avionics had the opportunity to radio home about several electrical problems made that somewhat unlikely.
Not really - the ones that have happened before haven't completely torn apart the plane, just damaged it enough to make it unflyable. Ie, Pan Am 103.

[edit] Just read up on TWA 800. That one was apparently, that catastrophic: the plane just abruptly disappeared, electronically. The flight data recorders were intact and simply stopped recording and the transponder stopped tranmitting.

For Pan Am 103, I was wrong, though: the wiki says that while the explosion only punched a 20 inch hole in the fuselage, but the secondary effects, structural damage and aerodynamic forces were enough to rapidly tear apart the plane... but not violent enough to kill the passengers. It's a little disturbing to think about, but in most such cases (and in the Shuttle Challenger!), the passengers were almost certainly killed by impact with the ground, not by the explosion/breakup of the aircraft.

[edit2] TWA 800 was particularly gruesome. Though the explosion was much bigger than Pan Am 103's, the damage was more localized and complete -and not huge, meaning the damage didn't affect the rest of the plane at all. Ironically, this led to a very similar crash scenario: the nose separated from the fuselage and fell intact and the body with the wings continued intact in a separate piece. Most of the passengers surely survived the explosion and those in the back 3/4 of the plane rode a burning but still flying piece of airplane until it pitched up enough to rip off the wings (probably only a few seconds), then fell, in flames. It must have been horrible.
mgb_phys
#36
Jun3-09, 11:05 PM
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What about the wind shear and breakup idea? Would the tail ripping off (like that one in 2001) cause such flight control failures? Are these flight control failures certain computer failures or could they be the computer's necessary reaction to a change in aircraft controllability or loss of sensors (whether electrical or physical)?
Flight587 was an airbus A300. The pilot used full rudder in flight which you aren't supposed to do, the vertical stabilizer failed at about twice it's design load. After this Airbus fitted software to all it's fly by wire systems which stop the pilot breaking the aircraft. This is a little controversial as some traditionalist pilots claim it could stop them recovering in a very extreme situation.

From what I understand, there are two debris fields, several miles apart. And 4 minutes to crash from 35,000 feet is pretty quick, about 100 mph.
4 minutes is the time between error messages, ie between the autopilot disengaging and the assumed failure of the cabin. The time to impact is unkown

I thought the fact that the flight avionics had the opportunity to radio home about several electrical problems made that somewhat unlikely.
Not necessarily, if something ripped a hole in the body destroying major bits of the avionics+control system the system could have sent the error messages before the cabin lost pressure and the ACARS failed.

I'm also wondering if a microburst hitting a plane at cruising speed could cause enough of a vertical (negative) g-force to rip off the wings.
Microbursts don't rely stress the airframe like that. If a bunch of air the plane is sitting in suddenly accelrates downwards the airframe goes with it there is no net stress on the wings. Microbursts are only a danger when you are near the ground - where suddenly being thrown down 1000ft might be bad news if you are only 900ft up!

Wings can also take a lot of stress, 787 wing being loaded to 150% of it's maximum design load


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