AF447
If I may...
A key understanding in philosophy and to a lesser extent, linguistics is, speakers of different languages "see" the world differently - direct translation is therefore not possible - "equivalency" is not possible.
Who would have thought that what many would have considered a straightforward phrase such as "ligne de vol", (which I took literally as "line of flight" which meant a more or less flat attitude because that is the way the airplane "is" when in flight, but descending in a vertical trajectory, "stalled but with little yaw") could be interpreted in so many ways. It teaches us that language is a huge part of our "reality" and not just a tool for communication. (if that's what it is, it's doing a very poor job).
The disagreements on the BEA language, the interpretation of "spin" and "flat", the abiding reservation or assured bravery with which "facts" and causal chains are entered, all have less to with what happened than with language. In this sense, the original, French BEA is not the "defining" document but nor is any translation into any other language. It is one document written very much in the manner in which the discussion has unfolded here. We may be certain that the strong views and disagreements are solid, primary factors in this report and in any other accident report. Whether truth emerges is a matter of such dynamics, not a matter of what actually happened. We are profoundly human and cannot escape interpretation - we are always "inside" interpretation because there is no "fixed" referent outside us which language may "call upon" and upon which we would all agree.
We might say that this is trivially obvious - until we run across genuine, serious, deep disagreements on words whose only commonality is the spelling of them.
Back to lurking in the FCOM...
PJ2
A key understanding in philosophy and to a lesser extent, linguistics is, speakers of different languages "see" the world differently - direct translation is therefore not possible - "equivalency" is not possible.
Who would have thought that what many would have considered a straightforward phrase such as "ligne de vol", (which I took literally as "line of flight" which meant a more or less flat attitude because that is the way the airplane "is" when in flight, but descending in a vertical trajectory, "stalled but with little yaw") could be interpreted in so many ways. It teaches us that language is a huge part of our "reality" and not just a tool for communication. (if that's what it is, it's doing a very poor job).
The disagreements on the BEA language, the interpretation of "spin" and "flat", the abiding reservation or assured bravery with which "facts" and causal chains are entered, all have less to with what happened than with language. In this sense, the original, French BEA is not the "defining" document but nor is any translation into any other language. It is one document written very much in the manner in which the discussion has unfolded here. We may be certain that the strong views and disagreements are solid, primary factors in this report and in any other accident report. Whether truth emerges is a matter of such dynamics, not a matter of what actually happened. We are profoundly human and cannot escape interpretation - we are always "inside" interpretation because there is no "fixed" referent outside us which language may "call upon" and upon which we would all agree.
We might say that this is trivially obvious - until we run across genuine, serious, deep disagreements on words whose only commonality is the spelling of them.
Back to lurking in the FCOM...
PJ2
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The vertical G loads means it hit flat or almost flat. The flat spin theory could explain it if that is what happened but isn't it more likely with multiple instrument and autopilot failures that they ended up in a spiral dive and may have been trying to recover wings almost level and hit the water flat at a high sink rate? If that is all the data they have, high vertical G loads, the flat spin is just a possibility among others.
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Ligne de vol, an official translation:
First, let me say that as my nick says well, I'm not an airman. But I enjoyed enough this loooong thread to propose you something official about the translation of "ligne de vol" from Transport Canada, and from an officially bilingual country. From their airworthiness manual in French:
Rglement de l'aviation canadien - Partie V, Manuel de navigabilit Chapitre 525, Sous-chapitre C
scroll down the page to section 525.479. Do you see something familiar in the section's title? (and the first words of the section for that matter)
Now get back to the top of the page and click on the "English" tab. Get back down to 525.479 and now, what do you see?
OK, too lazy for this exercice? So, "ligne de vol" = "level attitude" at least to the ones making the flight rules around here.
Hoping this settles that one for good and for all.
Jean
Rglement de l'aviation canadien - Partie V, Manuel de navigabilit Chapitre 525, Sous-chapitre C
scroll down the page to section 525.479. Do you see something familiar in the section's title? (and the first words of the section for that matter)
Now get back to the top of the page and click on the "English" tab. Get back down to 525.479 and now, what do you see?
OK, too lazy for this exercice? So, "ligne de vol" = "level attitude" at least to the ones making the flight rules around here.
Hoping this settles that one for good and for all.
Jean
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En ligne de vol
This argument is getting boring.
As you don't agree on vocabulary / semantics, take this example ( I am French, a pilot and teach flying,. that should do to my credentials, right ?)
Take a tail dragger just before it starts its takeoff roll ; it sits on its tailwheel.
Now, accelerate, the pilot will give a forward control column movement ; the tailwheel raises and the pilot stops the movement there : He's now accelerating and he has put his aircraft "en ligne de vol".
That, and only that aspect is "en ligne de vol".
Another aspect of this discussion that's getting silly is people beating to death the different and seemingly contradictory aspects of the debris to promote their own ideas (and bashing the BEA at the same time).
Considering that the airplane is some 60 meters long - or 200 feet -, is it really difficult to understand that the same forces were not seen throughout the whole structure : some parts hit first (whether the airplane was en ligne de vol or not), that initial impact forces might have been seriously diminished through the energy absorption of the first "hits", including the dissipated energy through structural failures or breakages and finally that it would be surprising that we won't see some whiplash effects.
To think that the aircraft hit the water verically in a flat attitude, meaning that the impact was a single one and concerned the whole structure at the same 1,000,000 th of a second is silly and denotes an astonishing misunderstanding of dynamics.
As you don't agree on vocabulary / semantics, take this example ( I am French, a pilot and teach flying,. that should do to my credentials, right ?)
Take a tail dragger just before it starts its takeoff roll ; it sits on its tailwheel.
Now, accelerate, the pilot will give a forward control column movement ; the tailwheel raises and the pilot stops the movement there : He's now accelerating and he has put his aircraft "en ligne de vol".
That, and only that aspect is "en ligne de vol".
Another aspect of this discussion that's getting silly is people beating to death the different and seemingly contradictory aspects of the debris to promote their own ideas (and bashing the BEA at the same time).
Considering that the airplane is some 60 meters long - or 200 feet -, is it really difficult to understand that the same forces were not seen throughout the whole structure : some parts hit first (whether the airplane was en ligne de vol or not), that initial impact forces might have been seriously diminished through the energy absorption of the first "hits", including the dissipated energy through structural failures or breakages and finally that it would be surprising that we won't see some whiplash effects.
To think that the aircraft hit the water verically in a flat attitude, meaning that the impact was a single one and concerned the whole structure at the same 1,000,000 th of a second is silly and denotes an astonishing misunderstanding of dynamics.
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A Word About Languages and Translations
I've noted with great interest the topic of languages and translations and the
consequence of losing "meaning" in translation.
My native language is American English. However, I am bi-lingual in that I can speak, read, write AND UNDERSTAND, in German as well as in American English. (I spent 12 years of my life living with the natives in Germany!)
Whilst learning German, slowly at first, I came to the realization that some thought processes must also be modified somewhat when speaking, and listening, in a non-native language. To impart an idea or thought sometimes requires the adjusting of the mental processes involved in speech and understanding the intent behind that speech. Sometimes that which is intended in speech is not "correctly" understood by the recipient without a reciprocal adjustment in thought process as to the intended meaning being conveyed.
So, yes PJ2, I fully understand your excellent synopsis above.
consequence of losing "meaning" in translation.
My native language is American English. However, I am bi-lingual in that I can speak, read, write AND UNDERSTAND, in German as well as in American English. (I spent 12 years of my life living with the natives in Germany!)
Whilst learning German, slowly at first, I came to the realization that some thought processes must also be modified somewhat when speaking, and listening, in a non-native language. To impart an idea or thought sometimes requires the adjusting of the mental processes involved in speech and understanding the intent behind that speech. Sometimes that which is intended in speech is not "correctly" understood by the recipient without a reciprocal adjustment in thought process as to the intended meaning being conveyed.
So, yes PJ2, I fully understand your excellent synopsis above.
rgbrock1;
Fascinating comment from one who experiences what I can only write about, thanks.
Under the heading of "and now for something completely different", the notions and ideas of Jacques Derrida, (Fr. philosopher, d. 2004) express profound observations, and posit fundamental differences with the way language is comprehended "ordinarily", (as does Martin Heidegger). 'nuff drift. Thanks again.
I fully understand your excellent synopsis above.
Under the heading of "and now for something completely different", the notions and ideas of Jacques Derrida, (Fr. philosopher, d. 2004) express profound observations, and posit fundamental differences with the way language is comprehended "ordinarily", (as does Martin Heidegger). 'nuff drift. Thanks again.
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If I may...
I noticed that there is a debate on the BEA report and the vertical acceleration and flight attitude at impact.
Post #3331 has a good point about linguistic considerations.
As a French native speaking, I feel that the key sentence in the BEA report is quite odd, grammatically incorrect. In contrast the rest (whole) of the document is quite well written and clear.
"l’avion a vraisemblablement heurté la surface de l’eau en ligne de vol, une forte accélération verticale." would translate as "the plane likely hit the water surface 'en ligne de vol', a strong vertical acceleration". (sic)
Again as a native French speaking it sounds like the author was not confident in this specific phrase or didn't understand what (s)he was writing.
Maybe you should get back to the hard facts (splatten things photos) and disregard this particular odd sentence.
Excuse my french, hope this helps, just my two cents...
I noticed that there is a debate on the BEA report and the vertical acceleration and flight attitude at impact.
Post #3331 has a good point about linguistic considerations.
As a French native speaking, I feel that the key sentence in the BEA report is quite odd, grammatically incorrect. In contrast the rest (whole) of the document is quite well written and clear.
"l’avion a vraisemblablement heurté la surface de l’eau en ligne de vol, une forte accélération verticale." would translate as "the plane likely hit the water surface 'en ligne de vol', a strong vertical acceleration". (sic)
Again as a native French speaking it sounds like the author was not confident in this specific phrase or didn't understand what (s)he was writing.
Maybe you should get back to the hard facts (splatten things photos) and disregard this particular odd sentence.
Excuse my french, hope this helps, just my two cents...
Last edited by abricot; 8th Jul 2009 at 20:12. Reason: excuse my french
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abricot - 'sound' advice. I would also ask that the welter of posts about stalls/'flat' spins/whatever is tempered by the fact that neither we, nor, I believe, BEA, ACTUALLY know how it hit or what made it fall from the sky, so to get to minutiae at this stage is rather pointless. Trying to determine failure and impact events from jpegs on the web is also a rather daunting task.
I watch this thread for 'news' and have become jaded by the intensity of to-ing and fro-ing here about what I feel are inessentials.
Anyone got any NEWS - or perhaps some more 'good advice' for the younger pilot and design generation instead?
EDIT: Regarding Heidegger - his writings are 'notoriously difficult'
I watch this thread for 'news' and have become jaded by the intensity of to-ing and fro-ing here about what I feel are inessentials.
Anyone got any NEWS - or perhaps some more 'good advice' for the younger pilot and design generation instead?
EDIT: Regarding Heidegger - his writings are 'notoriously difficult'
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Hyperveloce:
about the "unreliable airspeed" procedures, when the flight safety is impacted, as they are applied by the operators (at the date of the accident) and as they appear in the latest version of the Airbus QRH (at the date of the accident): the instruction to take in account the stall alarms in the operator procedure is no longuer visible in the Airbus QRH.
about the "unreliable airspeed" procedures, when the flight safety is impacted, as they are applied by the operators (at the date of the accident) and as they appear in the latest version of the Airbus QRH (at the date of the accident): the instruction to take in account the stall alarms in the operator procedure is no longuer visible in the Airbus QRH.
I wonder if you fully understood the sense of this paper. What is written is that the memory item from Air France QRH "IAS Douteuse" (in French) slightly differed from official Airbus QRH (in English) concerning the "respect the stall warning". Then Air France informed its A330/340 crews of a change after June 5th. Nothing changed in "Airbus QRH" and it is not what you wrote above.
S~
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Why no lifejackets on passengers
The ditching stall scenario is being discounted mainly because there were no lifejackets on the passengers. I would put forth the explanation that there was no time to do this and to do so would require taking off the seatbelt which would be the last thing wanted of the passengers in what seems to have been an extremely fast and turbulent descent.
Last edited by Grayengineer; 8th Jul 2009 at 21:46.
Grayengineer;
I think so. Descent rates in the order of a hundred knots, plus-or-minus, for a fully-stalled, 205T high-drag, nutating mass would not be unusual. There would be planform (flat plate) resistance to higher speeds. The turbulence and the ride down would be quite violent given the massive amounts of air being displaced and resulting forces at work over different areas of the entire structure.
in what seems to have been an extremely fast and turbulent descent.
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language/culture my last digression
Yes rgbrock1 and P2. As a Frenchman living and working in the UK for many years I can feel the differences everyday. There are more than words in a language, there is culture so no translation can match that. I too can notice my "thinking process" changes from one language to the other. We are very lucky people so we should be very nice to those who believe "their" language and culture are "the" language and culture...
abricot: Agree with you the sentence you quote is incorrect ("avec" is missing) and if you are French you know this has nothing to do with not being confident or not understanding what (s)he was writing it is just a mistake in the typing: a word was omitted and nobody noticed it. I didn't notice it either when I read the report the first time... and on page 72 it is correctly typed. "pas de quoi fouetter un chat..."
Will Frazer: I was trying to help by explaining what a frenchman can read between the lines. It was not my intention to validate the BEA report I have no qualification for that, however I am not dumb and I know what is at stake in the report... I have a lot a relatives and friends in the Airbus and Air France environments I suppose that is as good as your friend with a PhD in French...
My sole intention was to help, I will remain silent.
abricot: Agree with you the sentence you quote is incorrect ("avec" is missing) and if you are French you know this has nothing to do with not being confident or not understanding what (s)he was writing it is just a mistake in the typing: a word was omitted and nobody noticed it. I didn't notice it either when I read the report the first time... and on page 72 it is correctly typed. "pas de quoi fouetter un chat..."
Will Frazer: I was trying to help by explaining what a frenchman can read between the lines. It was not my intention to validate the BEA report I have no qualification for that, however I am not dumb and I know what is at stake in the report... I have a lot a relatives and friends in the Airbus and Air France environments I suppose that is as good as your friend with a PhD in French...
My sole intention was to help, I will remain silent.
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Originally Posted by HarryMann
FWIW
In free fall in a stable flat attitude at 205t, terminal velocity could be in the region 200 ft/s ~ 300 ft/s - at sea level density. (obviously back of a fag packet calculation, but might give an idea)
Thats as little as 2 minutes from cruise altitide
In free fall in a stable flat attitude at 205t, terminal velocity could be in the region 200 ft/s ~ 300 ft/s - at sea level density. (obviously back of a fag packet calculation, but might give an idea)
Thats as little as 2 minutes from cruise altitide
Last edited by HarryMann; 8th Jul 2009 at 23:35.
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Also...
Do we even yet know if the Captain was definitely resting and if so, whether he even made it back to the flight deck..
If he was and the answer was no, could current and past A330 flight crew confirm he would likely have been called back if there was time to focus on such things.
If this could be shown we perhaps could say with more certainty that this a/c did indeed meet its sad demise after one rapid fall from cruise altitude
Do we even yet know if the Captain was definitely resting and if so, whether he even made it back to the flight deck..
If he was and the answer was no, could current and past A330 flight crew confirm he would likely have been called back if there was time to focus on such things.
If this could be shown we perhaps could say with more certainty that this a/c did indeed meet its sad demise after one rapid fall from cruise altitude
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Abricot:
As a French native speaking, I feel that the key sentence in the BEA report is quite odd, grammatically incorrect. In contrast the rest (whole) of the document is quite well written and clear.
"l’avion a vraisemblablement heurté la surface de l’eau en ligne de vol, une forte accélération verticale." would translate as "the plane likely hit the water surface 'en ligne de vol', a strong vertical acceleration". (sic)
Again as a native French speaking it sounds like the author was not confident in this specific phrase or didn't understand what (s)he was writing.
Maybe you should get back to the hard facts (splatten things photos) and disregard this particular odd sentence.
As a French native speaking, I feel that the key sentence in the BEA report is quite odd, grammatically incorrect. In contrast the rest (whole) of the document is quite well written and clear.
"l’avion a vraisemblablement heurté la surface de l’eau en ligne de vol, une forte accélération verticale." would translate as "the plane likely hit the water surface 'en ligne de vol', a strong vertical acceleration". (sic)
Again as a native French speaking it sounds like the author was not confident in this specific phrase or didn't understand what (s)he was writing.
Maybe you should get back to the hard facts (splatten things photos) and disregard this particular odd sentence.
Sorry but no. Be sure they do know exactly what they were talking about and this "little syntaxical blunder" (a comma instead of a coordination agent) may be explained if the text was edited at the last minute. Either they removed something in the description of the impact, either they added the last part of the sentence ("une forte accélération verticale).
S~
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Merci cousin
NOTanAM
In Canada all officials documents are issued/published in both languages. Now that we hold what might be a valid official translation, I think that can be stopped all the brain storming to scan, analyse, interpretate and translate in the best way possible the terms "ligne de vol" don't you think? Or should we have to start an endlessly discussion on how to translate "level attitude" in French?
It doesn't mean that I endorse the fact that this aircraft hit the sea in a level attitude or not (I don't know) but if you agree to this translation, it might be accepted by all of use once and for all?
First, let me say that as my nick says well, I'm not an airman. But I enjoyed enough this loooong thread to propose you something official about the translation of "ligne de vol" from Transport Canada, and from an officially bilingual country. From their airworthiness manual in French:
Rglement de l'aviation canadien - Partie V, Manuel de navigabilit Chapitre 525, Sous-chapitre C
scroll down the page to section 525.479. Do you see something familiar in the section's title? (and the first words of the section for that matter)
Now get back to the top of the page and click on the "English" tab. Get back down to 525.479 and now, what do you see?
OK, too lazy for this exercice? So, "ligne de vol" = "level attitude" at least to the ones making the flight rules around here.
Hoping this settles that one for good and for all.
Jean
Rglement de l'aviation canadien - Partie V, Manuel de navigabilit Chapitre 525, Sous-chapitre C
scroll down the page to section 525.479. Do you see something familiar in the section's title? (and the first words of the section for that matter)
Now get back to the top of the page and click on the "English" tab. Get back down to 525.479 and now, what do you see?
OK, too lazy for this exercice? So, "ligne de vol" = "level attitude" at least to the ones making the flight rules around here.
Hoping this settles that one for good and for all.
Jean
It doesn't mean that I endorse the fact that this aircraft hit the sea in a level attitude or not (I don't know) but if you agree to this translation, it might be accepted by all of use once and for all?
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Hyperveloce, regarding SatCom the simplest pattern is a slightly pinched bubble. A dimple in the direction of aim is "way off base" as does a null at zenith. There are steerable null antennas that can do this. There's no utility for such technology with Inmarsat.
And for reference Inmarsat runs in the 5.5GHz to 8GHz region. I believe exact frequencies are on their website (or Wakipoodle.) Up there St Elmo's fire static would have some presence but not very much, I believe. My experience is that the EMI effects of static discharge go down somewhat with frequency above VHF. But I suppose it's a good option for the outage period if there might have been some discharge at that time on the probably track the plane took.
JD-EE
And for reference Inmarsat runs in the 5.5GHz to 8GHz region. I believe exact frequencies are on their website (or Wakipoodle.) Up there St Elmo's fire static would have some presence but not very much, I believe. My experience is that the EMI effects of static discharge go down somewhat with frequency above VHF. But I suppose it's a good option for the outage period if there might have been some discharge at that time on the probably track the plane took.
JD-EE
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Originally Posted by ”PJ2”
The ability to take the Airbus into Alternate or Direct Law resides within the design of the autoflight system but is a profoundly non-standard approach with this design and is entirely within test-pilot territory.
Originally Posted by ”PJ2”
I state this strongly because it is not even in the realm of an "ad-hoc, emergency response" to a badly degraded aircraft or flight control system. I could not see this kind of system intervention condoned or even considered by any Airbus pilot nor can I see it as a legitimate response in the present discussion.
I believe I understood the difference between the ABI concept and the Boeing concept prior to your post. I just wasn’t certain if there was some acceptable method for the crew [other than a switch] to bypass the other modes/Laws and go to Direct Law in a single step. I now understand there is not.
I understand that in the Boeing actual control of the servos is still achieved by wire as it is in the Airbus when in Direct Law/C* Law. I know that there are no cables, pulleys or push rods. Both airplanes are still controlled “by wire”. It is not a major issue for me, just a difference in philosophy.
I am not challenging that difference in philosophy here as I do not think it relevant to the accident. They were not in a Boeing and there is no point in debating any subtle differences that may exist nor the different thought processes of the respective manufacturers.
The essential decision by the design and engineering people is, because the autoflight system is beyond it's design capabilities either during a serious system failure (hydraulic, electrical or data-loss) or a "jet upset", (> 10deg ND, 30NU, 50deg roll, approximately), it can no longer reference and interpret the situation the aircraft is in and necessarily hands control over the flight crew.
That’s good information and part of what I was getting at, perhaps too indirectly by not trying to ruffle any feathers. My apologies if you felt your's were.
I knew that there had to be limits to the autoflight system, I just didn’t know what they were. Now that you’ve told me, it fits right into my theories regarding the possible cause of the event. I am not implying nor did I mean to imply that the upset was caused by the autoflight system. In fact I think that whatever happened to the airplane was the cause of all those messages sent after it occurred and during its duration. I believe that the upset would just as readily have occurred in a B777 as it did in the A330 given the identical scenario. Whether or not it affected the recovery attempts that must have followed is wholly unknown and I’m not speculating that it did or didn’t.
In and encounter with extreme turbulence the aircraft could easily, in my opinion, exceed 10deg ND, 30deg NU, or even 50deg of roll (although not so likely the latter) in either type. If that should happen you say it “hands control over to the flight crew”. I assume that means it reverts (or degrades as you put it) to the equivalent of Direct Law. Is that correct?
Any one of five flight control computers on the 330 will provide full use of all flight controls without restrictions.
Excellent and just as I surmised; there is a great deal of redundancy. Redundancy is required in all critical systems, including flight control computers. The more a particular failure mode is considered to be possible or likely, the greater the redundancy provided. Next question: What happens should all five computers become inoperative at once or in rapid succession? I think I know but I would like you to tell me.
I have to emphasize that there is nothing in the A330 design in terms of pilot interventions that were not available in the B707/DC8 design. The flight control computers do not mysteriously "modify" pilot input to do what the engineers and designers really want but haven't told the flight crew.
That is understood and in fact I took it for granted. It could hardly be otherwise or you would need astronaut training and have to revert to the phrase: “Houston, we have a problem”.
Whether or not what “they told the flight crews” has been adequate, or said crews got the ‘memo’ is another matter. Given the many recent “incidents” and the changing procedures, it appears it may not have been. When there is much complexity and information is inadequate the otherwise benign can readily become the mysterious. Like it or not, pitot failures will cause loss of data but should not create pitch-overs or other erratic behavior. The fact is they appear to have done just that.
To be clear because there is a question, in Alternate law 1 & 2, pitch law is referenced to 'g' loading, (same as Normal law). The AOM does not specify that Pitch Alternate Law restricts 'g' loading to "2.5" but I suspect they do. In Direct Law, the aircraft is a "DC8".
The essential question is, "can the pilot get whatever 'g' s/he can pull above certification limits (2.5 positive, 2.0 negative, flaps up)? The answer is, yes in Direct Law and likely no, in pitch alternate laws 1 & 2, (1 is the same as 2 in pitch).
I don’t need to know the intricate programming of the software, I just need to know – what will it do - in a given set of circumstances – and what will it not do. You have been of great help. You answered my question and you also confirmed the beliefs I already had.
In other words, there are indeed limits to the capabilities of Normal Law, as well as Alternate law 1 & 2. Whether they are measured in terms of “g” or in terms of pitch up, pitch down, and roll, those limits CAN be exceeded, perhaps not by the pilot, but by other forces – such as extreme turbulence.
Although I may not have stated it with sufficient clarity, that’s been my premise all along and the reason for my queries. If I understand you correctly, that does NOT mean that the pilot is suddenly handed an unflyable airplane. It just means that he is now flying it in the equivalent of Direct Law. The fact that the signals to the actuators/servos are by wire, rather than by cables or rods is irrelevant.
In the event of a total electrical failure (not relevant to AF447 IMO) and/or loss of hydraulic pressure from the engine driven source, the pilot would still have ship’s battery to the ESS Bus (or whatever you call its equivalent) and hydraulics and electricity both from the RAT – if it deploys and functions. The airplane is controllable for at least battery life (I guess about 30 min) while the crew restores a better source of electrical power and/or relights and engine that supplies hydraulics. The airplane must have at least 3 hydraulic sources [A, B, & C or whatever nomenclature is used.], which is quite standard. Since it is a twin, either engine running would be sufficient as a source of both electrical and hydraulic power.
If total electric power is lost and cannot be restored or provided by the RAT, when the ships battery dies the ability to operate the servos ends and control would be lost. Likewise, If hydraulic pressure cannot be maintained by the RAT, or all fluid is lost, functional servos cannot direct non existent pressure to any control, and control is again lost.
My main point is: In extreme turbulence the limits of pitch, bank, roll, yaw, speed and “g” associated with Normal, Alternate 1 & Alternate 2 “LAWS” can, one or all, be exceeded in short order. I suspect that such exceedence, if experienced, would most probably trigger a host of warnings and flags in rapid succession – just as it triggers AP and A/THR disconnect.
If the airplane is heavy and already flying at or near is maximum altitude, an extreme updraft could easily place it above that maximum altitude and take it into the “corner”. In that case it will upset. Whether or not it could be recovered from the upset is pure conjecture. Such an updraft followed by a similarly severe downdraft could fail the horizontal tail surfaces or the fin, or the entire tailcone. In other words, extreme turbulence is the equivalent of “Tilt” in a pinball machine. Game over.
Feel free to correct me please, if you find any of this thinking to be off-the-wall. I’m not talking about a bump or two here or even about severe turbulence. I’m talking about extreme turbulence – which is essentially an unknown quantity – greater than severe. I’m not aware of any transport that has survived an encounter with extreme turbulence. Correct that too if you have knowledge of such and instance.
Did it happen like that? I do not know. I just know that AF447 was lost. We owe it to our brothers who flew it and those who rode on it to leave no stone unturned until we know why – that it may not be repeated if humanly possible. This I believe necessary even if one or more of the overturned stones happens to reveal unpleasantries.
I hope this is of some help - I'm being a bit "direct" only to save space and not to dismiss concerns. This is the way the system works - there is only complexity, but not mystery.
I say again, I have no problem whatever with your being “direct” and hope that you have no problem with my being equally direct.
Agreed, I see complexity, perhaps more complexity than truly necessary, but I do not see mystery.
In very broad terms, I see FBW as necessary in military applications. The maneuverability of a modern fighter cannot be achieved unless it is inherently unstable and inherent instability cannot be controlled without the aid of computers.
In transport aircraft that is not the case; they are inherently stable. We have it and are expanding its use because it is supposed to provide greater efficiency, less weight and save money. Does the cost of all the bells and whistles actually justify the effeciences gained? I don’t really know but I suspect not.
Me thinks the ultimate goal of automation is the eventual elimination of piloted aircraft. Think of the money that would save and you’ve just justified the cost. We’re a very long way from that but eventually it will be achieved and passengers will be quite happy with it assured as they will be that absolutely nothing can go wrong, go wrong, go wrong.
Meanwhile I will hope that an A380 doesn’t vanish in the night on its way to Perth while its crew leafs through the QRH in search of some obscure procedure, or fall victim to a disgruntled Bedouin with 500 souls on board. I hope too that the Dreamliner’s resin doesn’t become unglued or succumb to an undetected invisible crack in its fail-safe fuselage, or that its multiple electric motors that replace the hydraulics will not mysteriously fail when needed. We live in interesting times.
What happened to AF447 after 0215Z is immaterial in terms of systems design, aircraft response and crew handling.
That’s a pretty strong statement to make given the data currently available. Is there something you know that the rest of us don’t, or is that just your version of conjecture?
I note that the shuttle accidents are referenced in comparison to automation accidents regarding "tons of money" etc.
You misread my intent. The reference to the Shuttle bears but one resemblance to AF447 and it is this: Humans are not infallible at any level and neither is the technology they develop. Technology is also not superior to the forces of nature. The technology did not fail in the Shuttle losses; humans failed. As Robert Burns would say:
"But, Mousie, thou art no thy lane,
In proving foresight may be vain;
The best-laid schemes o' mice an 'men
Gang aft agley,
An' lea'e us nought but grief an' pain,
For promis'd joy!"
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ttse:
Well, there are a couple problems with that, still. Note, I am not discounting entirely the possibility of a spin. I am just saying it is not consistent with the findings of the report.
If you had a spin from altitude, I would expect the plane to hit at a near vertical vector with very little forward/backward acceleration. Also unless the rotation was very, very slow, the sideways inertial forces would still be a major (rather than minor) component to the tail failure. However the report found that the rudder failed forward with a slight left-ward twisting element (it is possible that this element could have been sufficient to throw it clear of the fuselage).
At 4 secs per rotation in a flat spin from altitude, I would expect sideways and forces to be a substantial fraction of the vertical forces and the forward deceleration to be negligible. Hence the VS would have failed sideways (perpendicular from the fuselage) with perhaps some other slight vector added representing what little was left of the original fight vector. Remember that the VS is close to the extremity of the spin, so the centrifugal forces are very high there.
On the other hand, in a low altitude stall, we would expect strong forward and vertical forces, along with some minor twisting as the airframe hits the water not quite level (due to wind). This seems most compatible with the findings to date. Not that the findings are infallible at this juncture.
The basic issue is that, absent air resistance, an unpowered fall from a specific vector will be largely parabolic (roughly comparable to a plane in flat spin, though a spinning aircraft, depending on wind, might generate sideways Magnus-effect lift, changing trajectory, but shouldn't be that substantial in a large airliner). However air resistance flattens this parabola, resulting on an even more vertical impact and less forward velocity. I would expect that if you dropped a rock out of a plane at FL350 and mach 0.8, it would impact the ground nearly (though not quite) vertically.
Hope this helps.
Depends entirely on the type of spin and rate of rotation. A deep-stall with slow rotation (i.e. flat-spin already discussed lots)could be a better all-around fit.
If you had a spin from altitude, I would expect the plane to hit at a near vertical vector with very little forward/backward acceleration. Also unless the rotation was very, very slow, the sideways inertial forces would still be a major (rather than minor) component to the tail failure. However the report found that the rudder failed forward with a slight left-ward twisting element (it is possible that this element could have been sufficient to throw it clear of the fuselage).
At 4 secs per rotation in a flat spin from altitude, I would expect sideways and forces to be a substantial fraction of the vertical forces and the forward deceleration to be negligible. Hence the VS would have failed sideways (perpendicular from the fuselage) with perhaps some other slight vector added representing what little was left of the original fight vector. Remember that the VS is close to the extremity of the spin, so the centrifugal forces are very high there.
On the other hand, in a low altitude stall, we would expect strong forward and vertical forces, along with some minor twisting as the airframe hits the water not quite level (due to wind). This seems most compatible with the findings to date. Not that the findings are infallible at this juncture.
The basic issue is that, absent air resistance, an unpowered fall from a specific vector will be largely parabolic (roughly comparable to a plane in flat spin, though a spinning aircraft, depending on wind, might generate sideways Magnus-effect lift, changing trajectory, but shouldn't be that substantial in a large airliner). However air resistance flattens this parabola, resulting on an even more vertical impact and less forward velocity. I would expect that if you dropped a rock out of a plane at FL350 and mach 0.8, it would impact the ground nearly (though not quite) vertically.
Hope this helps.
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Memory item versions about stall alarms
Hi Jeff,
I wonder if you fully understood the sense of this paper. What is written is that the memory item from Air France QRH "IAS Douteuse" (in French) slightly differed from official Airbus QRH (in English) concerning the "respect the stall warning". Then Air France informed its A330/340 crews of a change after June 5th. Nothing changed in "Airbus QRH" and it is not what you wrote above.
S~
Olivier
I wonder if you fully understood the sense of this paper. What is written is that the memory item from Air France QRH "IAS Douteuse" (in French) slightly differed from official Airbus QRH (in English) concerning the "respect the stall warning". Then Air France informed its A330/340 crews of a change after June 5th. Nothing changed in "Airbus QRH" and it is not what you wrote above.
S~
Olivier
Well, in the operator procedures you find the instruction to take in account stall alarms even in the case of unreliable airspeeds (AoA based), and not in the aircraft manufacturer's QRH. Strange to term it a "slight" difference since the two versions could induce two opposite behaviours for crews facing both stall alarms (and possible ECAM status messages of "risk of undue stall warnings"). Sounds also weird that there can be two "slightly" different versions of a same memory item at the same time ? the BEA report page 67 states that the two slightly different memory item were both the versions in force for the operator and for Airbus at the date of the accident. The note of Air France of the 5th of June does not seem to be to inform crews of a change after June the 5th, it is a reminder of the procedures already in force (*). Is it a correct understanding ?
Jeff
(*) "Sans attendre les premieres recommandations du BEA et/ou du
constructeur et sans prejuger de leur contribution a la sequence des
evenements, il nous parait important de rappeler a tous les pilotes Airbus
que..."
evenements, il nous parait important de rappeler a tous les pilotes Airbus
Last edited by Hyperveloce; 8th Jul 2009 at 22:05.
