AF447
Will;
First, I am not discussing the AF crew here or suggesting anything in the following points.
While I remain cognizant of the B2 accident at Guam, loss of sensors/sensor data does not, in and of itself, generally result in loss-of-control resulting in an accident. The QRH Unreliable Airspeed/ADR Failure drills are in place for such a loss and have been used to successfully maintain a safe flight path while recovering the necessary sensors. I have had this experience in a 767; there are recent incidents which attest to this understanding. Given only what we have, we can assume that the flight control computers did not stop functioning and that they were still controllable by the stick even as they reverted to alternate law even with the loss of PRIM1.
There is no special technique or training one needs for flight in alternate law; training is required for flight with unreliable speed, however, but such training, with shortened simulator times, (down to 3.5hr sessions in some cases) is rare.
In the absence of ACARS indications, we could conclude that it is not these computers which were in the cascade of failures; from what little is known from the ACARS, we can safely assume that the flight control primary and seconary computers (FCPC/FCSC), minus PRIM1, continued to function as expected at least until 02:14:59Z.
In 99.9% of all mode confusion occurrences on this and other automated aircraft, "What's it doing now?" is a statement about training and knowledge, not about the aircraft itself. Millions of hours of safe flight and millions of successful departures and arrivals attest to this. The 320/330/340 series aircraft can be hand-flown just like a 172. Not understanding what your aircraft 'is doing now' means an instant disconnection of the autoflight system until one has regained situational awareness inside and outside.
I think we probably agree if I am reading your statements as intended, that this isn't primarily an "airplane" problem. I think there are important things to say about 'pre-programmed' cascading failures but redundancy has it's own issues (as per a recent (linked) paper on the subject), as does a system which contemplates monitoring/judging like a human being to self-assess, "What am 'I' doing now?"
The apparent failure of a pitot-static system and the apparent consequent loss of possibly 3 ADIRUs (with attendant faults/failures) do not render the flight controls inoperable/uncontrollable - that's my only point. Again, I make no judgement here - I am merely unpacking the statement a bit.
Well said. That was my initial impression when I first began to fly the 320 in 1992 and, while one learns one's aircraft as thoroughly as one can and I found the Airbus series a beautiful aircraft to fly, that impression, bolstered by some experiences, never fully left me. It is why I both defend the airplane and criticize it.
I think too, that a loss of sensors as is demonstrable prior to if not a part of this accident, presents an arguably suitable example of the differences involved in manual flight and a litany of pre-programmed failures that cascade from a manageable defect into a very dangerous reluctance of the computers to perform at even a very basic level of expectation.
While I remain cognizant of the B2 accident at Guam, loss of sensors/sensor data does not, in and of itself, generally result in loss-of-control resulting in an accident. The QRH Unreliable Airspeed/ADR Failure drills are in place for such a loss and have been used to successfully maintain a safe flight path while recovering the necessary sensors. I have had this experience in a 767; there are recent incidents which attest to this understanding. Given only what we have, we can assume that the flight control computers did not stop functioning and that they were still controllable by the stick even as they reverted to alternate law even with the loss of PRIM1.
There is no special technique or training one needs for flight in alternate law; training is required for flight with unreliable speed, however, but such training, with shortened simulator times, (down to 3.5hr sessions in some cases) is rare.
In the absence of ACARS indications, we could conclude that it is not these computers which were in the cascade of failures; from what little is known from the ACARS, we can safely assume that the flight control primary and seconary computers (FCPC/FCSC), minus PRIM1, continued to function as expected at least until 02:14:59Z.
In 99.9% of all mode confusion occurrences on this and other automated aircraft, "What's it doing now?" is a statement about training and knowledge, not about the aircraft itself. Millions of hours of safe flight and millions of successful departures and arrivals attest to this. The 320/330/340 series aircraft can be hand-flown just like a 172. Not understanding what your aircraft 'is doing now' means an instant disconnection of the autoflight system until one has regained situational awareness inside and outside.
I think we probably agree if I am reading your statements as intended, that this isn't primarily an "airplane" problem. I think there are important things to say about 'pre-programmed' cascading failures but redundancy has it's own issues (as per a recent (linked) paper on the subject), as does a system which contemplates monitoring/judging like a human being to self-assess, "What am 'I' doing now?"
The apparent failure of a pitot-static system and the apparent consequent loss of possibly 3 ADIRUs (with attendant faults/failures) do not render the flight controls inoperable/uncontrollable - that's my only point. Again, I make no judgement here - I am merely unpacking the statement a bit.
Instead of a 'tool' the automatics are proposed to be nothing less than a superior 'pilot', whose purpose is to 'protect' the airplane. Inherent in this language is an 'attitude' (a human one) of 'supremacy'.
Last edited by PJ2; 27th Jun 2009 at 00:56.
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PJ2
The B2 cannot be flown manually. At All. The e/series AB flies just fine by hand. Here is the dilemma: Until Flight crew are fully cognizant of the duality of the Airbus, and train its idiosyncracies, its interface with its crew will be not fully trained, a potentially hazardous situation. Knowing one's a/c is critical to safe flight. Stopping short of training criticism across different carriers, it is this flaw that needs attention.
Once that B2 pitched up past 10 degrees, the crew could have punched out without any repercussions from their commander. They stuck with it until it got ridiculous, and left the FD.
I'm sure the computers were 'puzzled', 'they' didn't know what hit 'them'.
More important than "What's it doing now?" might be: "What's it going to do?"
I appreciate your open mind as an AB pilot. It is after all a human problem.
The AB is a phenomenal a/c, what's missing is some assessment and remediation of human induced shortcomings, pilot and a/c.
Will
The B2 cannot be flown manually. At All. The e/series AB flies just fine by hand. Here is the dilemma: Until Flight crew are fully cognizant of the duality of the Airbus, and train its idiosyncracies, its interface with its crew will be not fully trained, a potentially hazardous situation. Knowing one's a/c is critical to safe flight. Stopping short of training criticism across different carriers, it is this flaw that needs attention.
Once that B2 pitched up past 10 degrees, the crew could have punched out without any repercussions from their commander. They stuck with it until it got ridiculous, and left the FD.
I'm sure the computers were 'puzzled', 'they' didn't know what hit 'them'.
More important than "What's it doing now?" might be: "What's it going to do?"
I appreciate your open mind as an AB pilot. It is after all a human problem.
The AB is a phenomenal a/c, what's missing is some assessment and remediation of human induced shortcomings, pilot and a/c.
Will
Will;
I remain an enthusiastic, open yet unconvinced (and now retired) AB pilot; my open mind is far grumpier and has been since 1992 about these broader matters than I will ever allow in my posts.
It is indeed, a human problem and it is, as I offered in the "philosophical" post, coming home to roost; it's trite to say it I know, but hubris is inappropriate where aviation is concerned.
Yes, I suspected the B2 couldnt' be flown manually given the kinds of flight controls it had and the probable need for neutral stability (making it impossible to fly without a computer), and that the guys stuck with it. I wonder though, how a potential single-point failure made it into production - almost certainly it was not an unknown.
I appreciate your open mind as an AB pilot. It is after all a human problem.
It is indeed, a human problem and it is, as I offered in the "philosophical" post, coming home to roost; it's trite to say it I know, but hubris is inappropriate where aviation is concerned.
Yes, I suspected the B2 couldnt' be flown manually given the kinds of flight controls it had and the probable need for neutral stability (making it impossible to fly without a computer), and that the guys stuck with it. I wonder though, how a potential single-point failure made it into production - almost certainly it was not an unknown.
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Would the A330 suffer Mach tuck??
Does raise a concept though, in the infamous 'coffin corner'
Assumptions
-Crew at 35k feet wouldn't have tactile sense of speed due to control forces and wind noise, assuming noise canceling headsets and tight speed range.
-Sailplane experience, (is that common in Europe starting out?), so they know what stall buffet is from thermaling.
Scenario
Pitots slowly build ice and computer advances auto throttles because computer thinks it's slowing down. Reach buffet boundary, get a split, autopilot disengages, master caution and warnings, crew notices ASI's are split, but low, confuse buffet with somehow being in a stall, advance power levers and push forward, when they're already at Vne say. Now we're hot in turbulence. Of course you were hot when the computer took you there in this scenario.
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emu787:
did the AFCS detect low speed - about to get a stall or low speed buffet boundary approaching (erroneous airspeed information) and the computer pitched the aircraft nose down and applied full power thinking this is the way to recover. This would almost certainly result in instantaneous excessive speed that would test the integrity of the airframe to its limit.
did the AFCS detect low speed - about to get a stall or low speed buffet boundary approaching (erroneous airspeed information) and the computer pitched the aircraft nose down and applied full power thinking this is the way to recover. This would almost certainly result in instantaneous excessive speed that would test the integrity of the airframe to its limit.
S~
Olivier
Last edited by takata; 28th Jun 2009 at 04:38. Reason: incorrect explanation
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As a self confessed Airbus sceptic, the defenders of the genre may feel free to flame me, but . . . . last years Qantas incident made me squirm, now, after one has finally & inevitably gone in ,the pilot body and indeed the public in general, discover that we have (at least ) 2 more USA regulated incidents to be considered PLUS two more involving F-registered but not AF airframes PLUS 6 was it ? more occurences in the last year or so involving AF airframes .
So, without in any way wishing to over-emphasise due to my previously admitted bias, I must ask, for something which has in all likelihood finally come home to roost, what did Airbus previously have in mind to address the issue apart from crossing it's fingers and emphasising to crew that when the sh1t hits the fan you had better be damned good at finding and reading the right checklist/troubleshooting as your world turns inside out around you.
Very helpful or what ?
And short of a complete rethink in the control (Ha Ha
) philosophy what are they going to do now that they shouldn't already have done in response to the previous very clear warnings offered by the previous upsets.
I am very anti the USA "sue them at every opportunity " mentality, but how will it look in a court of law if & when the total lack of accurate data being displayed & acted on by the FCC's ,that is being suggested as a very likely factor here ,is confirmed to be the case.
Is this really a reasonable scenario to give a normal line crew on a dark and dirty night in the middle of the ocean?
It strikes me that Lindbergh had more useful and accurate data available than these poor guys had at their disposal.
So, without in any way wishing to over-emphasise due to my previously admitted bias, I must ask, for something which has in all likelihood finally come home to roost, what did Airbus previously have in mind to address the issue apart from crossing it's fingers and emphasising to crew that when the sh1t hits the fan you had better be damned good at finding and reading the right checklist/troubleshooting as your world turns inside out around you.
Very helpful or what ?
And short of a complete rethink in the control (Ha Ha
) philosophy what are they going to do now that they shouldn't already have done in response to the previous very clear warnings offered by the previous upsets.I am very anti the USA "sue them at every opportunity " mentality, but how will it look in a court of law if & when the total lack of accurate data being displayed & acted on by the FCC's ,that is being suggested as a very likely factor here ,is confirmed to be the case.
Is this really a reasonable scenario to give a normal line crew on a dark and dirty night in the middle of the ocean?
It strikes me that Lindbergh had more useful and accurate data available than these poor guys had at their disposal.
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So it seems the best guess at the moment is that probe icing caused all the ADCs to fail leaving the pilots with degraded flight controls and little instrumentation whilst flying through an area of active CBs at night.
Then, over the days since AF447 several other AC report of probe icing and a similar cascade of failures, fortunately with better outcomes.
I doubt heightened awareness has prompted crews to report these incidents when previously they would have said nothing - such severe systems failure would have made the headlines even before AF447.
So, why the sudden flurry of similar sounding problems - a statistical blip or is there some other factor?
CC
Then, over the days since AF447 several other AC report of probe icing and a similar cascade of failures, fortunately with better outcomes.
I doubt heightened awareness has prompted crews to report these incidents when previously they would have said nothing - such severe systems failure would have made the headlines even before AF447.
So, why the sudden flurry of similar sounding problems - a statistical blip or is there some other factor?
CC
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To complicated!!!!
I'm convinced after reading quite some comments, that the crash's cause was an inexperienced pilot. Three hours into the flight the captain was probably sleeping in the back. The senior FO ran into the WX trap. This storm was a monster. I assume around a level 5. The airplane fell apart in the storm. Nobody can expect to get out of a storm that size in one piece. I think, not being an airbus friend in general, there is no design fault and the huppla is political.
chris
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In 99.9% of all mode confusion occurrences on this and other automated aircraft, "What's it doing now?" is a statement about training and knowledge, not about the aircraft itself.
Lies,damn lies and statistics.
No interface??Plane is controlled by pilot with a controlling veto from computer.Computer downgrades/upgrades its controlling veto in 4 different sets of laws depending on system status.Computer is subject to faulty source data but still has controlling vote.Computer casts this controlling vote on a series of very complex voting algorithms which are susceptible to spiking and hysteresis.Pilot can see and feel and think without any programming but doesnt have the controlling veto.
Sounds like an interface,and a screwy one at that.Give the human final authority and give it instantly and easily(simple switch).
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I'm with you on that one. I have looked at the 330 FCC info via the Tech Log thread, and am now CONVINCED the system should be:
Full computer control UNTIL sufficient degredation of inputs etc occurs, then straight to Direct Law - not forgetting along the way to teach pilots to fly.
Too many 'options' I feel otherwise, and a significant danger in not knowing what you have got.
Full computer control UNTIL sufficient degredation of inputs etc occurs, then straight to Direct Law - not forgetting along the way to teach pilots to fly.
Too many 'options' I feel otherwise, and a significant danger in not knowing what you have got.
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Captplaystation
I liked this one - "It strikes me that Lindbergh had more useful and accurate data available than these poor guys had at their disposal".
Maybe not far away from truth.
Maybe not far away from truth.
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I can only speak from my own experience of flying in awful turbulence in a Cb.
All I did- after the autos jumped off- was to try and hang onto the attitude.
Couldnt read the ASI (!), but pulled some power off to slow down a bit.
Accepted the vertical speed the Cb gave us, (in our case it was downwards) and just concentrated on the attitude. Wings level, didn't trim, kept the AoA at usual value.
Hung on like crazy and waited for it to stop!
I was so maxxed out flying it was all I could do to put the 'belts' on.
I'll be amazed if these guys did anything else.
At least by having the AP and AT go off on 447, it left them with the power they had and the trim/ attitude they had. No bad thing really.
Their ASIs would no doubt have been 'all over the place' due to the big gusts/ turbulence etc but probably unreadable too. Maybe this is when the speed disagree messages were generated.
The a/c plainly then came apart either without any further input from them, which is quite plausible. Or maybe after some erroneous input from them which is also plausible and quite understandable-an attempt to maintain altitude, for example.
The big Boo-Boo was going in the Cb in the first place. Like I did.
All I did- after the autos jumped off- was to try and hang onto the attitude.
Couldnt read the ASI (!), but pulled some power off to slow down a bit.
Accepted the vertical speed the Cb gave us, (in our case it was downwards) and just concentrated on the attitude. Wings level, didn't trim, kept the AoA at usual value.
Hung on like crazy and waited for it to stop!
I was so maxxed out flying it was all I could do to put the 'belts' on.
I'll be amazed if these guys did anything else.
At least by having the AP and AT go off on 447, it left them with the power they had and the trim/ attitude they had. No bad thing really.
Their ASIs would no doubt have been 'all over the place' due to the big gusts/ turbulence etc but probably unreadable too. Maybe this is when the speed disagree messages were generated.
The a/c plainly then came apart either without any further input from them, which is quite plausible. Or maybe after some erroneous input from them which is also plausible and quite understandable-an attempt to maintain altitude, for example.
The big Boo-Boo was going in the Cb in the first place. Like I did.
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Computers
IMHO, flight computers should be treated like student pilots. Let them fly the a/c, but be able to take over (and quick...). "I've got it" means that the instructor has the controls. Take "partially" the control back is not safe, IMHO.
"Protections" should be part of the pilot's skills, it's up to him (her)to decide if a particular control input will exceed a/c limits, but maybe this particular control input can save the situation.
To have the "I've got it" switch is very important. This (switch) will put the "student computer"back in his place.
Students think they know how to fly. Computers "think" they know how to fly.
Management thinks computers know how to fly, so why "spend" more money in training pilots?
Important point to think about, IMHO, is that computers haven't mastered the "art" of flying yet, and pilots are gradually loosing their skills due to this "money saving" policy (lack of training).
Pilots have less control of their a/c, but their responsibilities are getting bigger every day...
Just a thought...
Rob
"Protections" should be part of the pilot's skills, it's up to him (her)to decide if a particular control input will exceed a/c limits, but maybe this particular control input can save the situation.
To have the "I've got it" switch is very important. This (switch) will put the "student computer"back in his place.
Students think they know how to fly. Computers "think" they know how to fly.
Management thinks computers know how to fly, so why "spend" more money in training pilots?
Important point to think about, IMHO, is that computers haven't mastered the "art" of flying yet, and pilots are gradually loosing their skills due to this "money saving" policy (lack of training).
Pilots have less control of their a/c, but their responsibilities are getting bigger every day...
Just a thought...
Rob
post 1
post 2
One thing that sticks with me so far is that the pilot comments on this thread seem to have a pretty good idea of what they would have done in the the loss of air-data turbulence scenario.
If my interpretation is correct then this is a pointer for searching for other factors.
I can only speak from my own experience of flying in awful turbulence in a Cb.
All I did- after the autos jumped off- was to try and hang onto the attitude.
Couldnt read the ASI (!), but pulled some power off to slow down a bit.
Accepted the vertical speed the Cb gave us, (in our case it was downwards) and just concentrated on the attitude. Wings level, didn't trim, kept the AoA at usual value.
Hung on like crazy and waited for it to stop!
I was so maxxed out flying it was all I could do to put the 'belts' on.
I'll be amazed if these guys did anything else.
At least by having the AP and AT go off on 447, it left them with the power they had and the trim/ attitude they had. No bad thing really.
Their ASIs would no doubt have been 'all over the place' due to the big gusts/ turbulence etc but probably unreadable too. Maybe this is when the speed disagree messages were generated.
The a/c plainly then came apart either without any further input from them, which is quite plausible. Or maybe after some erroneous input from them which is also plausible and quite understandable-an attempt to maintain altitude, for example.
All I did- after the autos jumped off- was to try and hang onto the attitude.
Couldnt read the ASI (!), but pulled some power off to slow down a bit.
Accepted the vertical speed the Cb gave us, (in our case it was downwards) and just concentrated on the attitude. Wings level, didn't trim, kept the AoA at usual value.
Hung on like crazy and waited for it to stop!
I was so maxxed out flying it was all I could do to put the 'belts' on.
I'll be amazed if these guys did anything else.
At least by having the AP and AT go off on 447, it left them with the power they had and the trim/ attitude they had. No bad thing really.
Their ASIs would no doubt have been 'all over the place' due to the big gusts/ turbulence etc but probably unreadable too. Maybe this is when the speed disagree messages were generated.
The a/c plainly then came apart either without any further input from them, which is quite plausible. Or maybe after some erroneous input from them which is also plausible and quite understandable-an attempt to maintain altitude, for example.
I was kicked by some guys who are still under the impression that today's "Professional Pilots" and todays training are above being overwhelmed in the cockpit to the point the pilot is just trying to manage the stick and throttle and actually perspiring too.
If my interpretation is correct then this is a pointer for searching for other factors.
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I amazes me that the pilot personality contains so much scepticism and disbelief. Since the beginning of instrument flying, pilots have encounter CB's, told the story of undescribeable turbulence and horror to anyone who would listen, yet most pilots dismiss these tales and blunder out to make the same mistake, frequently with tragic consequences.
I fully expect this type of event will repeat itself forever as long as human pilots fly airplanes, simply due to the personality traits that draw a person to a career of aviation.
Countless pilots have pentrated weak CB's successfully over periods of many years, only to re-enforce their belief that CB's aren't that bad and the horror stories of massive encounters can be dismissed as incidents told by scared wimpy pilots.
Back on the days of flying the airmail, we had pilot killed busting a line of midwestern cold front thunderstorms. He was said to be a great pilot "because he was right side up" when the cb slammed his plane into the mud.
God help any pilot who thinks they can handle a severe CB.
BFD (not wimpy but still scared of CB's since May 12, 1982 )
I fully expect this type of event will repeat itself forever as long as human pilots fly airplanes, simply due to the personality traits that draw a person to a career of aviation.
Countless pilots have pentrated weak CB's successfully over periods of many years, only to re-enforce their belief that CB's aren't that bad and the horror stories of massive encounters can be dismissed as incidents told by scared wimpy pilots.
Back on the days of flying the airmail, we had pilot killed busting a line of midwestern cold front thunderstorms. He was said to be a great pilot "because he was right side up" when the cb slammed his plane into the mud.
God help any pilot who thinks they can handle a severe CB.
BFD (not wimpy but still scared of CB's since May 12, 1982 )
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Culture?
I'm hoping for a response from someone who knows Air France, to the following. I'm not making a statement, just asking.
IF (just if) the Capt was not on the flight deck, is there any part of the AFR pilot culture which would make the two folks up front hesitant or reluctant to make a significant deviation (time & fuel implications) around severe weather without the Capt's prior knowledge?
IF (just if) the Capt was not on the flight deck, is there any part of the AFR pilot culture which would make the two folks up front hesitant or reluctant to make a significant deviation (time & fuel implications) around severe weather without the Capt's prior knowledge?
And short of a complete rethink in the control (Ha Ha ) philosophy what are they going to do now that they shouldn't already have done in response to the previous very clear warnings offered by the previous upsets.
Give the human final authority and give it instantly and easily(simple switch).
I liked this one - "It strikes me that Lindbergh had more useful and accurate data available than these poor guys had at their disposal".
Maybe not far away from truth.
Maybe not far away from truth.
"Protections" should be part of the pilot's skills, it's up to him (her)to decide if a particular control input will exceed a/c limits, but maybe this particular control input can save the situation.
To have the "I've got it" switch is very important. This (switch) will put the "student computer"back in his place.
Students think they know how to fly. Computers "think" they know how to fly.
Management thinks computers know how to fly, so why "spend" more money in training pilots?
Important point to think about, IMHO, is that computers haven't mastered the "art" of flying yet, and pilots are gradually loosing their skills due to this "money saving" policy (lack of training).
Pilots have less control of their a/c, but their responsibilities are getting bigger every day...
To have the "I've got it" switch is very important. This (switch) will put the "student computer"back in his place.
Students think they know how to fly. Computers "think" they know how to fly.
Management thinks computers know how to fly, so why "spend" more money in training pilots?
Important point to think about, IMHO, is that computers haven't mastered the "art" of flying yet, and pilots are gradually loosing their skills due to this "money saving" policy (lack of training).
Pilots have less control of their a/c, but their responsibilities are getting bigger every day...
I suspect (and in a few cases, know) that there are some highly experienced people making these points who have made exceptional contributions to this and many other discussions.That is why I think it is important to attempt once again to make something as clear as possible, recognizing that the human, pyschological phenomena called "prejudice" is very much alive and well in this discussion. There are many here making pre-judgements about the airplane without ever having flown it or even understanding it.
In discussing these I believe that the understandings and explanations are crucial to an understanding of this accident and the only reason I bring these notions up at all is I think we all wish to target our energies.
I think further, that anyone who thinks that "the computers" caused this accident through removing control of the aircraft from the pilot without offering the pilot any alternative except the "Spam in a can" position, (a phrase correctly used by John Glenn to NASA when they were designing the Mercury space capsule) has not flown the Airbus or doesn't understand it or have knowledge of the relevant systems.
Pilots of an Airbus A320/A330/A340 are not relegated to observer status when things go seriously wrong and "the computers won't do what the pilot wants".
What is happening here is "groupthink" - through past prejudices (absence of knowledge but a strong opinion regardless), or through reading comments about "computers" and parroting it back in their own words, everyone has jumped on this bandwagon. It reminds me exactly, of the nature of the discourse on the Habsheim accident where people STILL think that "the computers did it".
Like so many occurrences that happen when in a crowd, this prejudice has become an irrational rallying cry and has achieved a life of it's own without anyone doing any thinking or questioning.
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.
If you have read this far and haven't thrown up your arms and dismissed this as just another Airbus apologist's diatribe, you will know and hopefully appreciate that I am making a plea for understanding, not a plea to "accept" the Airbus as a design. If one is to criticize with any credibility at all, one must criticize from knowledge, not blind prejudice, (unless one simply wishes to do so, in which case, there is no dialogue, or learning, possible).
The argument;
All posters quoted are arguing that "the computers" somehow removed control from the pilot. This is not the case and up until 02:14:59Z, that was not indicated in the ACARS messages we have. The ACARS messages indicate that the crew had full control over the aircraft up to the point where the messages stopped.
The crew almost certainly did not have speed or possibly altitude information due to the loss of pitot (and possibly static) probe data which in turn, caused the loss, possibly of all three, of the ADRs computers. This is indicated in the ACARS messages - "NAV ADR DISAGREE" is a relatively serious fault.
The ADIRS are not flight control computers. They are a combined Air Data Computer and Inertial Reference Unit into one computer/control panel. I supplied a schematic of the pitot-static system some time ago to help others understand the inputs to the ADR computer.
The ADIRS have nothing to do with the flight controls. The airplane can be flown under complete pilot control (and was) with all the ADIRUs lost. It would be extremely challenging with a high probability of loss of control if the aircraft entered a large CB.
Loss of the ADR computers is a serious abnormality but it will not automatically result in loss of the aircraft. The QRH Unreliable Airspeed procedures, which are memory items and not a "pull out the checklist" item, provide pitch and power data to keep the aircraft within a nominal speed until recovery or other crew action takes place.
Loss of the IRS's is a far more serious emergency if one is in cloud or is flying at night with no visible horizon. But this is not a flight control computer problem - this is a problem which could occur in any airliner design and not just this one.
In at least four cases now, the processes which were created after the Birgenair and Aeroperu B757 accidents occurred, worked, and saved the aircraft.
Failure of the pitot/static system is not a flight control problem.
With the A330 and A340 design, there are three Primary Flight Control Computers and two Secondary Flight Control computers. The aircraft can be flown, under full control, with the loss of all but one of these flight control computers.
The loss of flight data from the pitot-static system will not render any of these five computers unserviceable. Nor do any computers "make up their mind" or "control the aircraft" beyond the pilot's wishes. That simply does not happen and it is time to set the record straight so that it will be possible to comprehend really happened to this aircraft.
I would offer the view that anyone who has prejudged this aircraft likely will be unable to come to further understanding as to what really happened in this accident and it will be the work of others to determine what really occurred. That is what prejudice does - blind one to 'undesired' knowledge, here, and in other human endeavours as well.
Summary;
- failure of the pitot-static system and, consequently, failure of the ADIRS does not affect the ability of the pilot to fly the aircraft using the sidestick.
- failure of the ADIRS does not by itself lead to loss of pilot controllability of the 330/340.
- Failure of the IRSs can result in loss of the aircraft through absence of attitude information but as any pilot knows, this can occur in any aircraft, (and does, in general aviation all the time when pilots not qualified on instruments fly into cloud).
- The A330/A340 aircraft's five flight control computers would not be disabled by the loss of pitot-static data. Any one of these computers alone, will provide full controllability of the aircraft "directly", (in Direct Law, in short, an ordinary airplane), just like the B777 will when its flight control computers degrade, for whatever reason, the Direct "law", (Boeing doesn't call it a "law"). The "big switch" in the 777 permits the pilot to manually switch to Direct control but control is still electronic and not "cable-and-pulley". I can supply the schematic, if anyone wishes to compare systems).
- The question of loss of all five flight control computers via the loss of all ADIRS input is not answered in the information I have available. However, loss of all five flight control computers, (by whatever reason), results in a heavily degraded controllability through rudder, THS, (Trim Horizontal Stabilizer) and engine thrust; more control than the Sioux City DC10 but not sufficient controllability to withstand entry into a thunderstorm.
My sole intention here is to educate, not to criticize points of view. I know there is a delicate balance in a discussion with other professionals.
I think there are good reasons to base criticism of the 320/330/340 design philosophy upon, but citing notions that "the pilot has no control over the airplane", or that " 'the computers' have taken control" is not a solid, nor informed basis for such criticism.
BOAC;
Full computer control UNTIL sufficient degredation of inputs etc occurs, then straight to Direct Law - not forgetting along the way to teach pilots to fly.
Your remark concerning training is absolutely spot-on. Forces beyond our immediate control but seripticiously with our compliance, have tried to "remove us from the cockpit", so to speak, downplaying experience, training and all else a pilot does, legitimized by the impression that "pilots are expensive". As I said to Will Fraser in agreeing with his views on the hubris of automation, the philosophy engendered by the advent of the first fbw design does have a basis for criticism and I and many of my colleages said so and did so at the time we were being checked out. I recall when the 320 had no such thing as VNAV and we flew it with either "Open Descent", (FlCh for Boeings) or Vertical Speed and nothing else. When the "Full Standard" was introduced, we were handed a 300-page "FMGS Pilots Guide" and told to learn it on the job. No training, no guidance. This was in the days just after the Madras and Strasbourg accidents where mode confusion was still a new thing and no one knew. That was the approach taken and I have to observe that it hasn't changed much in twenty years. I think it is about to.
lomapaseo;
One thing that sticks with me so far is that the pilot comments on this thread seem to have a pretty good idea of what they would have done in the the loss of air-data turbulence scenario.
If my interpretation is correct then this is a pointer for searching for other factors.
If my interpretation is correct then this is a pointer for searching for other factors.
I sense, (and that's all it is) that this is an extremely complex accident and hope that this is both understood and appreciated by the BEA and all other flight safety organizations.
PJ2
Last edited by PJ2; 27th Jun 2009 at 20:03.
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"All I did- after the autos jumped off- was to try and hang onto the attitude.
Couldnt read the ASI (!), but pulled some power off to slow down a bit. Accepted the vertical speed the Cb gave us, (in our case it was downwards) and just concentrated on the attitude. Wings level, didn't trim, kept the AoA at usual value."
Well, somebody finally said what I've been wondering for 123 pages of posts. Back in the Dark Ages when I learned to fly (mid-1960s), we were taught that what you did if you flew into Cunim was 1/maintain attitude and wings-level, 2/hold pretty much the power you've got, and 3/ignore altitude. Nobody ever said much about airspeed, which took care of itself if you did 1, 2 and 3.
Couldnt read the ASI (!), but pulled some power off to slow down a bit. Accepted the vertical speed the Cb gave us, (in our case it was downwards) and just concentrated on the attitude. Wings level, didn't trim, kept the AoA at usual value."
Well, somebody finally said what I've been wondering for 123 pages of posts. Back in the Dark Ages when I learned to fly (mid-1960s), we were taught that what you did if you flew into Cunim was 1/maintain attitude and wings-level, 2/hold pretty much the power you've got, and 3/ignore altitude. Nobody ever said much about airspeed, which took care of itself if you did 1, 2 and 3.
stepwilk;
That's classic SOP for inadvertent CB entry and is standard kit for an airline pilot. Perhaps it wasn't discussed because of this, but it's good to see it said. They're essentially the same items as handling an unreliable airspeed indication except a couple of pitch-power memorized items to stabilize the aircraft for troubleshooting.
As has been pointed out here many, many times now - doing both, (failure of all flight data and possibly attitude information while inside a CB), would have a very low possibility of a successful outcome, in any aircraft.
That's classic SOP for inadvertent CB entry and is standard kit for an airline pilot. Perhaps it wasn't discussed because of this, but it's good to see it said. They're essentially the same items as handling an unreliable airspeed indication except a couple of pitch-power memorized items to stabilize the aircraft for troubleshooting.
As has been pointed out here many, many times now - doing both, (failure of all flight data and possibly attitude information while inside a CB), would have a very low possibility of a successful outcome, in any aircraft.
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PJ2
You have claimed that I, as a member of the group of 'all other posters', hold that the computers somehow prevented the pilots from controlling the a/c in some way.
My position is exactly the opposite. Given the regime at the beginning of the ACARS, a/p flying, cruise alt, pilots monitoring, etc. I have held that given the parameters allowed the a/p, the flight crew were satisfied with the situation (this is of course assumed). The a/c experiences some turbulence or other challenge the a/p is unable to track, and it trips off.
Following directly its disconnect is entry into Alternate Law. It is at this point things begin to go pear, or so we can entertain, given the messages on the data sheet.
In some as yet unknown sequence, multiple failures are reported, and experienced as warnings, flags, and multiple displays. I would suggest that it appears the PF and PNF were 'startled', first by the disconnect, then by the computers programmed responses such that they were possibly overwhelmed; it is at this juncture that an untrained for and (perhaps) deliberately ignored result may have eliminated any possibility of recovery. As per the other (and recent) unreliable AD incidents show, to recover demands a crew be incredibly sharp, profusely trained, and able to selectively ignore some of the computer's conclusions. On this night it wasn't to be, or so we can propose.
As I have said, the Airbus330 is a phenomenal a/c, no one can deny it. What might be lacking is a recognition of, and training for, some blind spots in programming, and a hard look at the imperfections in the interface between FBW and the pilots. As far as that goes, the only real difference so far making the AB unique is Alternate Law; it is as you say quite possible no a/c could have escaped the fate of 447.
Loss of all pitot/statics has been discussed, it might have caused an overreaction in the software (perhaps not), and an underreaction in the pilots. If this is true, we need to put pilot and FBW back on the same page.
cheers, Will
You have claimed that I, as a member of the group of 'all other posters', hold that the computers somehow prevented the pilots from controlling the a/c in some way.
My position is exactly the opposite. Given the regime at the beginning of the ACARS, a/p flying, cruise alt, pilots monitoring, etc. I have held that given the parameters allowed the a/p, the flight crew were satisfied with the situation (this is of course assumed). The a/c experiences some turbulence or other challenge the a/p is unable to track, and it trips off.
Following directly its disconnect is entry into Alternate Law. It is at this point things begin to go pear, or so we can entertain, given the messages on the data sheet.
In some as yet unknown sequence, multiple failures are reported, and experienced as warnings, flags, and multiple displays. I would suggest that it appears the PF and PNF were 'startled', first by the disconnect, then by the computers programmed responses such that they were possibly overwhelmed; it is at this juncture that an untrained for and (perhaps) deliberately ignored result may have eliminated any possibility of recovery. As per the other (and recent) unreliable AD incidents show, to recover demands a crew be incredibly sharp, profusely trained, and able to selectively ignore some of the computer's conclusions. On this night it wasn't to be, or so we can propose.
As I have said, the Airbus330 is a phenomenal a/c, no one can deny it. What might be lacking is a recognition of, and training for, some blind spots in programming, and a hard look at the imperfections in the interface between FBW and the pilots. As far as that goes, the only real difference so far making the AB unique is Alternate Law; it is as you say quite possible no a/c could have escaped the fate of 447.
Loss of all pitot/statics has been discussed, it might have caused an overreaction in the software (perhaps not), and an underreaction in the pilots. If this is true, we need to put pilot and FBW back on the same page.
cheers, Will
Last edited by Will Fraser; 27th Jun 2009 at 19:21.