AF447
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Follow on from post #2772 ( TU-154 flat spin accident).
From Air Safety Week (Sept 18th 2006), and although focused on T-tail aircraft incidents, some of the findings regarding vertical velocity/ trajectory under stall may be pertinent to the current discussion.
A Tale of Two T-Tails | Air Safety Week | Find Articles at BNET
Re: MD82 crash (Preliminary) AUGUST 2006 (WCA708)
Quote (page3):
"the engines wouldn't have recovered until gulping much denser air at the lower altitudes, shortly before impact at their descent rate of over 7000ft/min."
...."According to the Flight Recorder, WCA708 descended at a high angle-of-attack "
Quote (page 4) :
"The descent from FL330 took 210 seconds. The debris field was only 200m long and 110m wide, indicating a near vertical descent with no forward airspeed. The crew had radioed that "both engines had flamed out" but they were merely locked back at flight idle."
A Tale of Two T-Tails | Air Safety Week | Find Articles at BNET
Re: MD82 crash (Preliminary) AUGUST 2006 (WCA708)
Quote (page3):
"the engines wouldn't have recovered until gulping much denser air at the lower altitudes, shortly before impact at their descent rate of over 7000ft/min."
...."According to the Flight Recorder, WCA708 descended at a high angle-of-attack "
Quote (page 4) :
"The descent from FL330 took 210 seconds. The debris field was only 200m long and 110m wide, indicating a near vertical descent with no forward airspeed. The crew had radioed that "both engines had flamed out" but they were merely locked back at flight idle."
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As a forensic scientist, I am intrigued that there has been no reporting of any histological exams of the remains of the victims, which would conclusively show whether an inflight breakup, with a resulting ejection of occupants, occurred. Subjection to ambient temperatures in the -40C range (which would be about right for that latitude in June) and a terminal velocity in the 190mph range at 30,000-35,000 feet would have resulted in almost instantaneous tissue freezing of all exposed flesh. The formula for deriving wind chill is:
T (wind chill) = 35.74 + .6275*(ambient)-35.75V^.16 + .4275*T(ambient)*V(airspeed)^.16.If your calculator is in your flightbag, the result is a windchill of about -300C.With rapid onset cooling of that magnitude, several things would be readily apparent upon microscopic examination; e.g., water transport effects (dehydration) extracellular ice formation with mechanical crushing damage to cells, intercellular ice formation damage, cell darkening and twitching if the cooling rate was>25decC/min, which it surely would have been.
Of course, knowing the mechanism of the injury says nothing about the ultimate cause of the loss of the aircraft, but knowing might narrow the possibilities.
T (wind chill) = 35.74 + .6275*(ambient)-35.75V^.16 + .4275*T(ambient)*V(airspeed)^.16.If your calculator is in your flightbag, the result is a windchill of about -300C.With rapid onset cooling of that magnitude, several things would be readily apparent upon microscopic examination; e.g., water transport effects (dehydration) extracellular ice formation with mechanical crushing damage to cells, intercellular ice formation damage, cell darkening and twitching if the cooling rate was>25decC/min, which it surely would have been.
Of course, knowing the mechanism of the injury says nothing about the ultimate cause of the loss of the aircraft, but knowing might narrow the possibilities.
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LeandroSecundo - For one who understand french .. it's nice to read.
True, like the original bea report.
I make just one extract; which might be used as a 'health warning' for some posters....
"Nous nous contenterons donc, pour notre part, de reporter les éléments factuels que nous avons pu recueillir et de modestement proposer quelques mesures correctives ou recommandations qui, en l’état actuel de nos informations, nous sont apparues - a minima - pertinentes !"
We (eurocockpit) will restrict ourselves therefore to reporting the factual elements we have been able to gather (from the bea report) and makes some modest proposals for corrective actions which seem to us to be, at minimum, pertinant in the context of the information we presently have.
Well said.
True, like the original bea report.
I make just one extract; which might be used as a 'health warning' for some posters....
"Nous nous contenterons donc, pour notre part, de reporter les éléments factuels que nous avons pu recueillir et de modestement proposer quelques mesures correctives ou recommandations qui, en l’état actuel de nos informations, nous sont apparues - a minima - pertinentes !"
We (eurocockpit) will restrict ourselves therefore to reporting the factual elements we have been able to gather (from the bea report) and makes some modest proposals for corrective actions which seem to us to be, at minimum, pertinant in the context of the information we presently have.
Well said.
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The descent from FL330 took 210 seconds.
Now, as has been asked many times in this long and sometimes exasperating thread, why? The airframe is said to have remained intact. But, after the initial burst of automated messages, there was no verbal or electronic contact from the aircraft.
We have an object that appears to have fallen from the sky with normal, gravitational terminal velocity. We have no contact from anyone or anything inside it. There was no attempt (it appears) to prepare for a crash landing in the ocean.
The only explanation that makes sense to me is that they were all incapacitated at the moment of catastrophe whilst still in the cruise.
Now, what to infer from that? I have absolutely no idea and I would suspect that no-one else has either.
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In the lights of this catastrophe, Airbus seams willingfull to enhance air-to-ground communications to reinforce "flight data recovery" as they announced yesterday.
Airbus has launched a study for reinforcing flight data recovery, including, but not limited to, extended data transmission for commercial airliners, so that in the event of accidents, critical flight information can still be recovered and released to the investigating authorities.
Tom Enders, President and CEO of Airbus commented: “Gathering information from accidents is vitally important to further improve the safety of flying. Various technical means for reinforcing flight data recovery and data transmission to ground centres are principally available. We will now study different options for viable commercial solutions, including those where our experience with real-time data transmission from our own test aircraft could support the further development of such solutions.”
The study will be conducted by Patrick Gavin, Head of Airbus Engineering, and Charles Champion, Head of Customer Services, and will need to address technological issues as well as data protection and privacy concerns. Airbus will include industrial partners, research institutions, and international airworthiness and investigation authorities in this study.
Tom Enders, President and CEO of Airbus commented: “Gathering information from accidents is vitally important to further improve the safety of flying. Various technical means for reinforcing flight data recovery and data transmission to ground centres are principally available. We will now study different options for viable commercial solutions, including those where our experience with real-time data transmission from our own test aircraft could support the further development of such solutions.”
The study will be conducted by Patrick Gavin, Head of Airbus Engineering, and Charles Champion, Head of Customer Services, and will need to address technological issues as well as data protection and privacy concerns. Airbus will include industrial partners, research institutions, and international airworthiness and investigation authorities in this study.
Last edited by stadedelafougere; 3rd Jul 2009 at 14:32.
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Follow on from post #2772 ( TU-154 flat spin accident).
From Air Safety Week (Sept 18th 2006), and although focused on T-tail aircraft incidents, some of the findings regarding vertical velocity/ trajectory under stall may be pertinent to the current discussion.
A Tale of Two T-Tails | Air Safety Week | Find Articles at BNET
Re: MD82 crash (Preliminary) AUGUST 2006 (WCA708)
Quote (page3):
"the engines wouldn't have recovered until gulping much denser air at the lower altitudes, shortly before impact at their descent rate of over 7000ft/min."
...."According to the Flight Recorder, WCA708 descended at a high angle-of-attack "
Quote (page 4) :
"The descent from FL330 took 210 seconds. The debris field was only 200m long and 110m wide, indicating a near vertical descent with no forward airspeed. The crew had radioed that "both engines had flamed out" but they were merely locked back at flight idle."
From Air Safety Week (Sept 18th 2006), and although focused on T-tail aircraft incidents, some of the findings regarding vertical velocity/ trajectory under stall may be pertinent to the current discussion.
A Tale of Two T-Tails | Air Safety Week | Find Articles at BNET
Re: MD82 crash (Preliminary) AUGUST 2006 (WCA708)
Quote (page3):
"the engines wouldn't have recovered until gulping much denser air at the lower altitudes, shortly before impact at their descent rate of over 7000ft/min."
...."According to the Flight Recorder, WCA708 descended at a high angle-of-attack "
Quote (page 4) :
"The descent from FL330 took 210 seconds. The debris field was only 200m long and 110m wide, indicating a near vertical descent with no forward airspeed. The crew had radioed that "both engines had flamed out" but they were merely locked back at flight idle."
From my days at the flying school and physics lectures, i seem to remember that these upsets are impossible to retrieve from. All T-Tail types are affected, 1-11, MD80 series etc....
I think that AF447 will not have been affect by a 'Deep-Stall', due to the airframe characteristics, but stall scenarios are not fully tested by AB, for the obvious reasons.
I think the idea that big jets cannot (mentioned elsewhere in this thread) spin, is preposterous! The fact that one wing can lose lift quicker than the other one is a factor for all types IMHO and is a function of physics, not engineering.
Maybe there is an argument for can certain big-jet types flat spin, but how would we know, obv. it is not tested, and if types have spun before i could imagine the airframe not standing up to it. I think the idea, that the aircraft might have spun, should be given some creedence. Considering at one moment it was @ FL350, and within a short timeframe, in the water. This combined with BEA's fact (that is how i read it, not an assumption) that the aircraft hit the water relatively flat with a strong vertical acceleration (acceleration = rate of change of velocity over time), combined with a low forward speed, suggest's to me that a stall scenario occured.
Speculative questions from me include:
Why would a normal stall scenario cause this from FL350 or below? considering there might have been enough height to recover...IMHO there would be fugoid osscillation on attitude, splitting between excessive pitching moments in the vertical plane, possibly exceeding overspeed and stall
Given that the type possibly cannot 'Deep Stall' (given by research by test pilots on plenty of airframes), why is there less mentioned that the aircraft may have spun? See my comments above...
Just my two penneth worth...
Unc
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Reading the French report:, the a/c hit the water ‘en ligne de vol’, the English translation says ‘in a straight line’.
From my knowledge of French technical language, ‘ligne de vol’ means something similar to ‘cruise attitude’, if not even ‘horizontal flight’.
From my knowledge of the English technical language, instead, ‘straight line’ means a ‘linear ‘ movement, with no reference to attitude or altitude (i.e., an unspecified linear trajectory)
I suppose the original, non-translated ‘ French wording is to be considered but , if so, this leaves me with more doubts.
Can French and English mother-tongue friends help me on this subject?
Daniel
From my knowledge of French technical language, ‘ligne de vol’ means something similar to ‘cruise attitude’, if not even ‘horizontal flight’.
From my knowledge of the English technical language, instead, ‘straight line’ means a ‘linear ‘ movement, with no reference to attitude or altitude (i.e., an unspecified linear trajectory)
I suppose the original, non-translated ‘ French wording is to be considered but , if so, this leaves me with more doubts.
Can French and English mother-tongue friends help me on this subject?
Daniel
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Interfaces, safety, etc.
First on the interface question.... An interface is just a set of means of inputs and outputs for interaction. Every airplane has an interface which consists of its instrument system and control inputs (yoke, sidestick, etc). These interfaces ARE important and one should not ignore the problem just because the interface is standardized.
Also I think that one legitimate concern about Airbus is that they have sold increasingly complex airplanes as requiring LESS pilot training. In fact, with added complexity, I think MORE training should be required.
Looking at the statistics, it seems however that airplanes are getting safer. One cannot argue that the A330 has a bad safety record at the moment, nor do other airbus planes. Certainly all Airbus planes to date have better safety records than the B747. However, PJ2 is exactly correct that a lot of the argument is prejudice from years of PR on behalf of those opposed to the trends.
I dunno. I personally thought the possibility that a passenger might have been able to hack the flight control computers on the 787 might have removed the pilot even more from being in control..... The problem here was interfaces which should not have been available (there should be no access to flight control interfaces from the main cabin)!
Also I think that one legitimate concern about Airbus is that they have sold increasingly complex airplanes as requiring LESS pilot training. In fact, with added complexity, I think MORE training should be required.
Looking at the statistics, it seems however that airplanes are getting safer. One cannot argue that the A330 has a bad safety record at the moment, nor do other airbus planes. Certainly all Airbus planes to date have better safety records than the B747. However, PJ2 is exactly correct that a lot of the argument is prejudice from years of PR on behalf of those opposed to the trends.
Originally Posted by PJ2
This does not mean that this design, just like any other design, does not have it's compromises and problems. Every aircraft design has and it is trite to say or argue otherwise that "one design is superior to another". The record speaks for itself, and no one...absolutely no one, is casting an eye towards the most advance airliner in existence, the Dreamliner, and saying the same things and it is far, far more automated than any Airbus. Prejudice does this.
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To Daniel 11000 (and all French non-speakers)
Yesterday, I heard an interview of the BEA director on the french radio France Inter. Directly questioned by the journalist about the meaning of his wording "ligne de vol", he clearly explained that the choice of his words was probably not the best, but that he clearly ment "normal attitude" meaning with "wings level" with "no significant roll".
So to close the dabate, and with French my primary language, and having heard the explanation on France Inter directly from the guy, by "en ligne de vol" he definitely ment "normal attitude, with wings level"
Yesterday, I heard an interview of the BEA director on the french radio France Inter. Directly questioned by the journalist about the meaning of his wording "ligne de vol", he clearly explained that the choice of his words was probably not the best, but that he clearly ment "normal attitude" meaning with "wings level" with "no significant roll".
So to close the dabate, and with French my primary language, and having heard the explanation on France Inter directly from the guy, by "en ligne de vol" he definitely ment "normal attitude, with wings level"
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T-tail
From my days at the flying school and physics lectures, i seem to remember that these upsets are impossible to retrieve from. All T-Tail types are affected, 1-11, MD80 series etc....
the outside of the engine cowling's i.e. to be able to handle or avoid a deep stall.
Again my problem with the subtle translation differences by whom ever between french and english leave me with questions.
1) I accept that the flight path of the aircraft could/would have been in a straight line for most of its descent . Does this match what the BEA meant?
2) I accept that the damages seen to the floating parts imply that they were within the fuselage section when it hit the water. Does this match what the BEA said?
3) I agree that the aircraft struck the water on its belly. Does this match the BEA report?
4) I can not conclude any words attributed to the report what the pitch, roll or actual heading of the aircraft was from the english words. Am I missing something? or are some posters assuming these axis?
5) Inspite of item (2) above is it possible that the aircraft might have broken into two or more large fuselage sections at altitude before hitting the water or do the BEA words preclude this?
1) I accept that the flight path of the aircraft could/would have been in a straight line for most of its descent . Does this match what the BEA meant?
2) I accept that the damages seen to the floating parts imply that they were within the fuselage section when it hit the water. Does this match what the BEA said?
3) I agree that the aircraft struck the water on its belly. Does this match the BEA report?
4) I can not conclude any words attributed to the report what the pitch, roll or actual heading of the aircraft was from the english words. Am I missing something? or are some posters assuming these axis?
5) Inspite of item (2) above is it possible that the aircraft might have broken into two or more large fuselage sections at altitude before hitting the water or do the BEA words preclude this?
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The ventral fins (strakes) were not new on the MD-80. They were first fitted on the DC9-50, for stability at cruise. All DC-9 are subject to deep stall. The DC9-80 was fitted with a stick pusher after it became uncontrollable in a deep stall in flight test, and they had to deploy the parachute to recover.
AF447 cg was near the aft limit. It is unknown what would have triggered its apparent flat spin, but it may have not taken a large event in severe turbulence.
Maybe a spin chute could have saved AF447..
GB
AF447 cg was near the aft limit. It is unknown what would have triggered its apparent flat spin, but it may have not taken a large event in severe turbulence.
Maybe a spin chute could have saved AF447..
GB
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ttcse,
one more 02.07 hours image for you/
This is the map of cloud tops with temps -75C or colder. France Meteo's analysis is that there were a few temps of -80C, which would correlate with CB cloud tops of 50,000 to 52,000 feet.
"On constate qu’à 2 h 07 les températures les plus froides sont de l’ordre de
-75 °C à -80 °C, alors que la tropopause se situe entre les FL500 et FL520,
avec une température voisine de - 80°C"
one more 02.07 hours image for you/
This is the map of cloud tops with temps -75C or colder. France Meteo's analysis is that there were a few temps of -80C, which would correlate with CB cloud tops of 50,000 to 52,000 feet.
"On constate qu’à 2 h 07 les températures les plus froides sont de l’ordre de
-75 °C à -80 °C, alors que la tropopause se situe entre les FL500 et FL520,
avec une température voisine de - 80°C"
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First I would wait the official results from the necropsies made by the Brazilian pathologists. Nothing has been made public officially, as far as I know.
Second, you find water in the lungs only if the person was breathing when submerged; they could have been killed instanly when the aircraft impacted. (and yes, I am an MD)
Second, you find water in the lungs only if the person was breathing when submerged; they could have been killed instanly when the aircraft impacted. (and yes, I am an MD)
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Even if alive when hitting the water, a laryngeal spasm in reaction to the water can keep water from entering the lungs. That spasm can last quite some time. In the forensic sciences, we have a saying: "The absence of evidence isn't necessarily evidence of absence.
Dani;
Correct. That's exactly what the BEA is trying to convey: level aircraft attitude, vertical trajectory with possible slight forward and perhaps even aft, trajectory, (possible explanation of the condition of the one spoiler found - torn out by reversed airflow, as someone posited a thousand posts ago) - not a straight line down, in other words.
The following are some considerations of other system faults which would likely have developed in any such stalled condition. There is no evidence for these assumptions but they are reasonable, given the vertical descent scenario described by the BEA.
We don't have evidence but may surmise that with such high angles of attack, the engines would have flamed out, (for those not familiar with this and would question this, flameout would be due to the extreme angle between the engine intake cowling and the air passing "upwards" almost at right angles to the axis of the engine. As such, air would not enter the engine in a smooth path).
Therefore, (again an assumption based upon the BEA's scenario), once the stall was fully developed and as engines flamed out, electricity and hydraulics would be lost except for what was available from the two batteries. The APU which has it's own battery could nevertheless not be started both given the time available and the highly disturbed airflow which would obtain in the BEA scenario, (again, roughly perpendicular to the axis of the aircraft).
Under such circumstances (loss of electrical generation on both AC buses), the RAT would deploy but would not supply emergency hydraulic pressure for flight controls or the emergency generator due to the direction of the airflow.
Providing the DC Essential bus was powered by the batteries, the cabin pressure controller would be powered. I can't find in the AMM what powers the outflow valves themselves but one could assume it would be from either the AC or DC essential buses. Perhaps someone can determine this.
With a flameout, airflow from the engines to the two packs would be lost and the cabin altitude would, after some time had passed, slowly begin to climb.
Please NOTE: I doubt very much whether the "Cabin Vertical Speed" ACARS message was generated as a result of engine flameout and consequent loss of airflow to the cabin. Flameout would be an event which would have occurred much later in the accident sequence after the stall was fully developed, again as envisioned by the BEA. (to lay the logic of this out fully...loss of both engines does not cause an immediate loss of pressurization, nor does it even result in a high cabin rate of climb. By the time any significant cabin rate of climb obtained, the capability of sending ACARS messages would have long been lost).
NOTE: These are some considerations of other system faults which would likely have developed in any such stalled condition. There is no evidence for these assumptions but they are reasonable, given the vertical descent scenario described by the BEA.
Originally Posted by Dani, post 2868
It's very unlikely that they ditched. It's very unlikely that they glided towards the water for any reason.
The following are some considerations of other system faults which would likely have developed in any such stalled condition. There is no evidence for these assumptions but they are reasonable, given the vertical descent scenario described by the BEA.
We don't have evidence but may surmise that with such high angles of attack, the engines would have flamed out, (for those not familiar with this and would question this, flameout would be due to the extreme angle between the engine intake cowling and the air passing "upwards" almost at right angles to the axis of the engine. As such, air would not enter the engine in a smooth path).
Therefore, (again an assumption based upon the BEA's scenario), once the stall was fully developed and as engines flamed out, electricity and hydraulics would be lost except for what was available from the two batteries. The APU which has it's own battery could nevertheless not be started both given the time available and the highly disturbed airflow which would obtain in the BEA scenario, (again, roughly perpendicular to the axis of the aircraft).
Under such circumstances (loss of electrical generation on both AC buses), the RAT would deploy but would not supply emergency hydraulic pressure for flight controls or the emergency generator due to the direction of the airflow.
Providing the DC Essential bus was powered by the batteries, the cabin pressure controller would be powered. I can't find in the AMM what powers the outflow valves themselves but one could assume it would be from either the AC or DC essential buses. Perhaps someone can determine this.
With a flameout, airflow from the engines to the two packs would be lost and the cabin altitude would, after some time had passed, slowly begin to climb.
Please NOTE: I doubt very much whether the "Cabin Vertical Speed" ACARS message was generated as a result of engine flameout and consequent loss of airflow to the cabin. Flameout would be an event which would have occurred much later in the accident sequence after the stall was fully developed, again as envisioned by the BEA. (to lay the logic of this out fully...loss of both engines does not cause an immediate loss of pressurization, nor does it even result in a high cabin rate of climb. By the time any significant cabin rate of climb obtained, the capability of sending ACARS messages would have long been lost).
NOTE: These are some considerations of other system faults which would likely have developed in any such stalled condition. There is no evidence for these assumptions but they are reasonable, given the vertical descent scenario described by the BEA.
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Interesting (to some) though the minutiae of drowning and/or asphyxiation may be we're heading too far into non-PPRuNe territory. Before I start hitting the 'Delete' and 'Thread Ban' buttons would somebody like to try getting this thread back on track?
Duck
Duck
Impressive report; equally impressive how many people who were originally convinced that it must have broken up at altitude as a result of evil european computers, yadda yadda, are now even MORE convinced of this after it becomes clear that it didn't break up...all that cognitive bias stuff must be true after all.