AF447 wreckage found
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Right on!! bbg (Page 51)
Didn't we go through this with the Dominica 757 crash?? Problem is the warnings don't shut up--goes back to a CV-580 crash in the midwest-they ingested a bird right at rotation and the engine autofeathered-the pilot was a veteran but the speaker was shouting "Pull Up, Pull Up................." he never got back the speed he need to recover - because?? Yea - He pulled up. I memorized the locations of the Aural and Speaker CB's on the 757 so I could shut them up and keep my head straight during what was obviously a warning malfunction. What's happening here is the Automation is not assisting pilots anymore -- pilots are trained to assist automation = Bad Formula! Standby for more of the same in the future until they get the formula changed-if ever!
Didn't we go through this with the Dominica 757 crash?? Problem is the warnings don't shut up--goes back to a CV-580 crash in the midwest-they ingested a bird right at rotation and the engine autofeathered-the pilot was a veteran but the speaker was shouting "Pull Up, Pull Up................." he never got back the speed he need to recover - because?? Yea - He pulled up. I memorized the locations of the Aural and Speaker CB's on the 757 so I could shut them up and keep my head straight during what was obviously a warning malfunction. What's happening here is the Automation is not assisting pilots anymore -- pilots are trained to assist automation = Bad Formula! Standby for more of the same in the future until they get the formula changed-if ever!
@ wallybird7
At the moment the incident began.....(from the May 28, 2011 update report)
"From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input....The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb."
As you say, no climb was planned - but that doesn't rule out an inadvertent climb induced by pulling the stick while correcting the right roll.
The report mentions the pilot raising the nose in the first seconds after taking the controls. It notes turbulence events. It doesn't mention evidence of an updraft.
At the moment the incident began.....(from the May 28, 2011 update report)
"From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input....The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb."
As you say, no climb was planned - but that doesn't rule out an inadvertent climb induced by pulling the stick while correcting the right roll.
The report mentions the pilot raising the nose in the first seconds after taking the controls. It notes turbulence events. It doesn't mention evidence of an updraft.
Last edited by pattern_is_full; 1st Jun 2011 at 06:51.
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Alan Levin's USAToday Article on AF447
I sorta took exception to the presumptive tone of the article and some private correspondence between journos in the same ilk....that I was copied in on. I decided to re-orient them (late at night after a half-bottle of brandy) - so it may not be comprehensive. If you know of any points that were missed, pls post. Apologies for length but need to be comprehensive. I'm sick of defenceless dead pilots having to carry the can.
Gentlemen
*
You oversimplify their predicament. You (and so do we all) need more data. However it's also obvious that useful data was exactly what the AF447 pilots lacked during their deep-stall descent - because of the peculiar aspects of the pitot freeze-up during high altitude cruise..... and its effect upon the subsequent post-zoom stall.
*
One of the characteristics of an approaching or incipient stall that pilots are trained to respond and react to is "low and decreasing" airspeed (even if they have no stall warning hooter or "cricket"). However they wouldn't have had any airspeed indication during their deep-stall descent with an iced pitot x 3. Nor did they have an angle-of-attack indication..... i.e. even though the A330 is equipped with an AoA vane to feed the automation (including the stall warning system), the pilots don't warrant a gauge of any sort. So what did they have for identification of (and recovery from) a stall? The real answer is precious little - by way of overt display or training fallback.
*
They had a source of pitch attitude. However consider that most approaches to the training one-g stall is made in level flight at a speed reduction rate of circa one knot per second. Thus, at the point of the incipient stall, where pilots are taught to initiate recovery (i.e. at the stall buffet), the additional cue on an ADI or visual horizon*is a high nose attitude (typically around +15 degrees).*But in a deep stall entered ballistically at high altitude post-zoom, the attitude in pitch during descent with max power (due pitch-up effect of underslung engines) would approximate the straight and level attitude of around 3 to 5 degrees nose-up. Thus they were robbed of most all cues that could clue them that they were in fact in a stall. They wouldn't have been aware that their auto-trimmed horizontal stabilizer trim was NOW unavailable - and stuck at its maximum of 13 degrees nose-up. If nothing else, it was that THS (trimmable hoz stabilizer) that would've held them in a stalled pitch attitude..... regardless of any subsequent side-stick pitch inputs. The THS has the REAL pitch-trim authority at low speed, the elevators are virtually trim-tabs for higher speed refinements.
*
But wouldn't the stall warning be blaring you say? Not necessarily so. It's designed to be discontinuous (a rare concession to the cacophony effect of blaring aural alerts in an emergency). In the factually sparse BEA report, that aspect isn't addressed in depth. The only trigger for the aural stall warning is the AoA and that has a set threshold both to start and to cease. Once they were at around 40 degrees AoA I'd be surprised if it was to be heard on the CVR (see later shock statement of cause of non-recovery below). What about the stick-shaker? It too has cautionary thresholds and they were soon well beneath that triggering band. The A330 wasn't tested for its high altitude ballistic stall entry characteristics - so the instrumentation wasn't available or calibrated to cope. What about the VSI or IVSI/RCDI (rate of descent indicator). It's not very attention-getting and it's probably linear (i.e.in a non-circular) presentation anyway in the A330 (I prefer the round dials for visual attention-getting). It's hard to say what it would have read in a compromised pitot-static system anyway. You must also consider what effect upon the airspeed indicators a 10,000 fpm rate of descent would have on their airspeed read-outs (think rate-of-change of static pressure). The ASI's are reliant upon both a pitot and a static pressure input feed.
*
*Would there have been any tell-tale buffeting? In a word "NO". The buffet in a one-g stall is provided courtesy of the disturbed airflow over the wing hitting the tailplane. At the BEA's stated 40 degrees angle-of-attack, the disturbed airflow would not impinge upon the tailplane. They were going down in an express elevator at around that self-same 40 degrees angle (that they were presenting to the relative airflow). I was surprised to find myself agreeing with one animated depiction on TV of the stalled steep descent event. That's how it would've been in my view - and thus the airflow and airframe buffet wouldn't have been a player in alerting the pilots to their stalled status. It was probably/relatively much quieter than the ambient noise in cruise, even with the engines at TO/GA. By design, in alternate, direct or ABNORMAL Law there is no auto-trim (it discontinued after reaching 13 degs nose-up), no ALPHA FLOOR PROT or ALPHA max (i.e. no max selectable AoA), so the aircraft can be stalled once in extremis - an aspect and consideration that's alien to Airbus pilots. AF447's stall occurred beyond the imagination (also) of the A330 designers or test pilots, at the ballistic apex of a zoom climb with lotsa power set - and at or above its ceiling for its weight.
*
But there were also other complications which I'll briefly mention:
*
a. What actually happened to initiate the sequence of failure advisories and the ACARS spew? Did the auto-pilot self-disconnect after running out of its ability to hold the nose-down force gradient of a horizontal stabilizer being trimmed by the system to compensate for the aircraft being driven ever faster in real speed terms (i.e. accelerated by the auto-thrust, to offset the perceived gradual loss of airspeed from the slowly icing pitots?). If so, then when the autopilot disconnected, the pitch-up would have been involuntary. Any evidence for that? The BEA says "the airplane's pitch attitude increased progressively and the plane started to climb. The PF made nose-down control inputs and alternately, left and right roll inputs." Reflect upon the fact that the one thing the pilot has left once he's apparently lost elevator authority in a pitch-up, is to roll the airplane in order to induce a nose-drop. It's evident IMHO that the post-disconnect pitch-up was therefore involuntary and opposed by the PF. Entry to the post-zoom stall is likely to have been automated.
*
b. A few seconds after the aircraft levelled at 37,500ft at a 4 deg AoA the BEA says: "the stall warning triggered again. The thrust levers were positioned at TO/GA and the pilot maintained nose-up inputs." No real surprise there. They'd zoomed to above their ceiling and the pilot was stick-back to oppose the tendency of the nose to drop at the unknown (to him) low speed. Unfortunately, as a result, the THS continued to trim to max nose-up and the distracted pilots then allowed the aircraft to stall. There's an indication that the lower speeds may have allowed the pitot heat to clear some of the pitot ice....i.e. the ISIS speeds becoming consonant with the recorded PF speed. Report: "As the captain re-entered the cockpit the recorded speeds became invalid and the stall warning stopped" At this point these are evident indications of now having entered into the very low IAS/high AoA deep-stall condition. Distractions of trouble-shooting are the likely cause of the PF allowing the 13 degs nose-up THS (of which he was unaware) to silently promote a stall.
*
c. If the autopilot had disconnected because of ADR disagree parameters being exceeded, then the zoom may have resulted from a post-disconnect overspeed warning and a natural pilot pitch-up response. Whatever the cause of that pitch-up, the auto-trim would've been available and so it was (BEA) - and so it did auto-trim the THS into a fateful 13 degs nose-up (whence it remained).
*
d. How did the captain's arrival upon the flight-deck affect the outcome? Firstly, in a quick urgent scan he'd not have seen the PF pilot's grip upon his sidestick (think about it and compare with what the MS990 Captain saw upon re-entering his Egyptair cockpit). He would've seen no (or low?) IAS displayed and the altimeter unwinding - yet loads of power. 20 seconds after he entered the flightdeck the throttles were placed at idle. At his command? Probably. Did he misinterpret the situation as the aftermath of a high-speed loss of control and thus did he complicate the recovery issue? Probably. Are Airbus pilots generally unfamiliar with the possibility of entering a deep-stall condition at altitude? Probably. Is it never sim practised or preached or does it not rate a mention in the Pilot's Handling Notes? Probably not.
*
e. The BEA mentions that, at A/P disconnect, a sharp fall from about 275 kts to 60kts in the left primary PFD was recorded, then a few moments later on the ISIS STBY insts. Using the analogy of how hail size-growth increases exponentially in the latter part of its fall (due to an ever increasing surface area upon which moisture can coalesce), we can divine that a similar thing was happening to each of the three pitots. Thus, as soon as the pilot made his sharp nose-up side-stick input, the smooth laminar flow into the LH pitot inlet (the only one recorded) would've been disrupted by the pitot's projecting icy excrescences.... causing the 275/60 transitory hiccup. I'd further interpret this as being partial proof that the auto-pilot disconnected primarily because of the elevator (nose-) download it was carrying due to the discrepancy between the aircraft's actual speed and the system speed (for which it was being THS-trimmed). i.e. It was unlikely that they actually hit Mach Crit and pitched up because of Mach Tuck. Thus the pitch-up may have been trim-induced and not pilot-initiated. Who's to know at this stage? But what happened next (the ballistic stall entry with 13 degrees nose-up THS) surely sealed their fate. The PF was never aware of that 13 degs nose-up THS (or he may have manually trimmed it out - yet another*completely*unnatural input action for a FBW Airbus pilot).
*
f. Ultimately, what killed their chances of recovery? It's very ironic that it was likely one of the systems meant to have saved them.
i.e. The BEA Report says: "At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again."
At the sound of the stall warning, the pilot was likely deterred from any further initiatives (even though he was on the right track with his pitch-down inputs) - and he promptly then handed over the controls to his more senior PNF. A stall warning that sounds off as you exit a deep-stall condition? Not a great idea at all....... it is likely to have the opposite of the desired effect. The overwrought pilot might easily assume that his action is initiating a stall. A Doppler-based stall warning whose pitch and volume varies (dependent upon how embedded in the stall you are) would be a much safer (and saner) proposition.
It gets back to that old saw: "For the want of a nail...." Unfortunately for AF447 it was more than just a nail. It was a whole row of rivets that allowed the operation to become unglued.
So if you place a pilot in harm's way beyond his training and experience, fail a vital sub-system that then causes a failure cascade, can you really blame him for the outcome? Perhaps you should be blaming a system that's too lazy or incompetent to extrapolate failure modes into real world scenarios and identify real threats. The hazard was all too evident from all the prior Air France, Air Caribbes, NWA and other incidents (including QANTAS). Nobody acted with sufficient urgency to address the hazards. Hubris? In large measure I'd say.
*
PS Also see the attached file - revelations from a*DER Spiegel article
Gentlemen
*
You oversimplify their predicament. You (and so do we all) need more data. However it's also obvious that useful data was exactly what the AF447 pilots lacked during their deep-stall descent - because of the peculiar aspects of the pitot freeze-up during high altitude cruise..... and its effect upon the subsequent post-zoom stall.
*
One of the characteristics of an approaching or incipient stall that pilots are trained to respond and react to is "low and decreasing" airspeed (even if they have no stall warning hooter or "cricket"). However they wouldn't have had any airspeed indication during their deep-stall descent with an iced pitot x 3. Nor did they have an angle-of-attack indication..... i.e. even though the A330 is equipped with an AoA vane to feed the automation (including the stall warning system), the pilots don't warrant a gauge of any sort. So what did they have for identification of (and recovery from) a stall? The real answer is precious little - by way of overt display or training fallback.
*
They had a source of pitch attitude. However consider that most approaches to the training one-g stall is made in level flight at a speed reduction rate of circa one knot per second. Thus, at the point of the incipient stall, where pilots are taught to initiate recovery (i.e. at the stall buffet), the additional cue on an ADI or visual horizon*is a high nose attitude (typically around +15 degrees).*But in a deep stall entered ballistically at high altitude post-zoom, the attitude in pitch during descent with max power (due pitch-up effect of underslung engines) would approximate the straight and level attitude of around 3 to 5 degrees nose-up. Thus they were robbed of most all cues that could clue them that they were in fact in a stall. They wouldn't have been aware that their auto-trimmed horizontal stabilizer trim was NOW unavailable - and stuck at its maximum of 13 degrees nose-up. If nothing else, it was that THS (trimmable hoz stabilizer) that would've held them in a stalled pitch attitude..... regardless of any subsequent side-stick pitch inputs. The THS has the REAL pitch-trim authority at low speed, the elevators are virtually trim-tabs for higher speed refinements.
*
But wouldn't the stall warning be blaring you say? Not necessarily so. It's designed to be discontinuous (a rare concession to the cacophony effect of blaring aural alerts in an emergency). In the factually sparse BEA report, that aspect isn't addressed in depth. The only trigger for the aural stall warning is the AoA and that has a set threshold both to start and to cease. Once they were at around 40 degrees AoA I'd be surprised if it was to be heard on the CVR (see later shock statement of cause of non-recovery below). What about the stick-shaker? It too has cautionary thresholds and they were soon well beneath that triggering band. The A330 wasn't tested for its high altitude ballistic stall entry characteristics - so the instrumentation wasn't available or calibrated to cope. What about the VSI or IVSI/RCDI (rate of descent indicator). It's not very attention-getting and it's probably linear (i.e.in a non-circular) presentation anyway in the A330 (I prefer the round dials for visual attention-getting). It's hard to say what it would have read in a compromised pitot-static system anyway. You must also consider what effect upon the airspeed indicators a 10,000 fpm rate of descent would have on their airspeed read-outs (think rate-of-change of static pressure). The ASI's are reliant upon both a pitot and a static pressure input feed.
*
*Would there have been any tell-tale buffeting? In a word "NO". The buffet in a one-g stall is provided courtesy of the disturbed airflow over the wing hitting the tailplane. At the BEA's stated 40 degrees angle-of-attack, the disturbed airflow would not impinge upon the tailplane. They were going down in an express elevator at around that self-same 40 degrees angle (that they were presenting to the relative airflow). I was surprised to find myself agreeing with one animated depiction on TV of the stalled steep descent event. That's how it would've been in my view - and thus the airflow and airframe buffet wouldn't have been a player in alerting the pilots to their stalled status. It was probably/relatively much quieter than the ambient noise in cruise, even with the engines at TO/GA. By design, in alternate, direct or ABNORMAL Law there is no auto-trim (it discontinued after reaching 13 degs nose-up), no ALPHA FLOOR PROT or ALPHA max (i.e. no max selectable AoA), so the aircraft can be stalled once in extremis - an aspect and consideration that's alien to Airbus pilots. AF447's stall occurred beyond the imagination (also) of the A330 designers or test pilots, at the ballistic apex of a zoom climb with lotsa power set - and at or above its ceiling for its weight.
*
But there were also other complications which I'll briefly mention:
*
a. What actually happened to initiate the sequence of failure advisories and the ACARS spew? Did the auto-pilot self-disconnect after running out of its ability to hold the nose-down force gradient of a horizontal stabilizer being trimmed by the system to compensate for the aircraft being driven ever faster in real speed terms (i.e. accelerated by the auto-thrust, to offset the perceived gradual loss of airspeed from the slowly icing pitots?). If so, then when the autopilot disconnected, the pitch-up would have been involuntary. Any evidence for that? The BEA says "the airplane's pitch attitude increased progressively and the plane started to climb. The PF made nose-down control inputs and alternately, left and right roll inputs." Reflect upon the fact that the one thing the pilot has left once he's apparently lost elevator authority in a pitch-up, is to roll the airplane in order to induce a nose-drop. It's evident IMHO that the post-disconnect pitch-up was therefore involuntary and opposed by the PF. Entry to the post-zoom stall is likely to have been automated.
*
b. A few seconds after the aircraft levelled at 37,500ft at a 4 deg AoA the BEA says: "the stall warning triggered again. The thrust levers were positioned at TO/GA and the pilot maintained nose-up inputs." No real surprise there. They'd zoomed to above their ceiling and the pilot was stick-back to oppose the tendency of the nose to drop at the unknown (to him) low speed. Unfortunately, as a result, the THS continued to trim to max nose-up and the distracted pilots then allowed the aircraft to stall. There's an indication that the lower speeds may have allowed the pitot heat to clear some of the pitot ice....i.e. the ISIS speeds becoming consonant with the recorded PF speed. Report: "As the captain re-entered the cockpit the recorded speeds became invalid and the stall warning stopped" At this point these are evident indications of now having entered into the very low IAS/high AoA deep-stall condition. Distractions of trouble-shooting are the likely cause of the PF allowing the 13 degs nose-up THS (of which he was unaware) to silently promote a stall.
*
c. If the autopilot had disconnected because of ADR disagree parameters being exceeded, then the zoom may have resulted from a post-disconnect overspeed warning and a natural pilot pitch-up response. Whatever the cause of that pitch-up, the auto-trim would've been available and so it was (BEA) - and so it did auto-trim the THS into a fateful 13 degs nose-up (whence it remained).
*
d. How did the captain's arrival upon the flight-deck affect the outcome? Firstly, in a quick urgent scan he'd not have seen the PF pilot's grip upon his sidestick (think about it and compare with what the MS990 Captain saw upon re-entering his Egyptair cockpit). He would've seen no (or low?) IAS displayed and the altimeter unwinding - yet loads of power. 20 seconds after he entered the flightdeck the throttles were placed at idle. At his command? Probably. Did he misinterpret the situation as the aftermath of a high-speed loss of control and thus did he complicate the recovery issue? Probably. Are Airbus pilots generally unfamiliar with the possibility of entering a deep-stall condition at altitude? Probably. Is it never sim practised or preached or does it not rate a mention in the Pilot's Handling Notes? Probably not.
*
e. The BEA mentions that, at A/P disconnect, a sharp fall from about 275 kts to 60kts in the left primary PFD was recorded, then a few moments later on the ISIS STBY insts. Using the analogy of how hail size-growth increases exponentially in the latter part of its fall (due to an ever increasing surface area upon which moisture can coalesce), we can divine that a similar thing was happening to each of the three pitots. Thus, as soon as the pilot made his sharp nose-up side-stick input, the smooth laminar flow into the LH pitot inlet (the only one recorded) would've been disrupted by the pitot's projecting icy excrescences.... causing the 275/60 transitory hiccup. I'd further interpret this as being partial proof that the auto-pilot disconnected primarily because of the elevator (nose-) download it was carrying due to the discrepancy between the aircraft's actual speed and the system speed (for which it was being THS-trimmed). i.e. It was unlikely that they actually hit Mach Crit and pitched up because of Mach Tuck. Thus the pitch-up may have been trim-induced and not pilot-initiated. Who's to know at this stage? But what happened next (the ballistic stall entry with 13 degrees nose-up THS) surely sealed their fate. The PF was never aware of that 13 degs nose-up THS (or he may have manually trimmed it out - yet another*completely*unnatural input action for a FBW Airbus pilot).
*
f. Ultimately, what killed their chances of recovery? It's very ironic that it was likely one of the systems meant to have saved them.
i.e. The BEA Report says: "At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again."
At the sound of the stall warning, the pilot was likely deterred from any further initiatives (even though he was on the right track with his pitch-down inputs) - and he promptly then handed over the controls to his more senior PNF. A stall warning that sounds off as you exit a deep-stall condition? Not a great idea at all....... it is likely to have the opposite of the desired effect. The overwrought pilot might easily assume that his action is initiating a stall. A Doppler-based stall warning whose pitch and volume varies (dependent upon how embedded in the stall you are) would be a much safer (and saner) proposition.
It gets back to that old saw: "For the want of a nail...." Unfortunately for AF447 it was more than just a nail. It was a whole row of rivets that allowed the operation to become unglued.
So if you place a pilot in harm's way beyond his training and experience, fail a vital sub-system that then causes a failure cascade, can you really blame him for the outcome? Perhaps you should be blaming a system that's too lazy or incompetent to extrapolate failure modes into real world scenarios and identify real threats. The hazard was all too evident from all the prior Air France, Air Caribbes, NWA and other incidents (including QANTAS). Nobody acted with sufficient urgency to address the hazards. Hubris? In large measure I'd say.
*
PS Also see the attached file - revelations from a*DER Spiegel article
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Somebody reaasure me please that there wasnt some automated voice screaming in the PF's ear saying " pull - up, pull - up" when his AoA was 40 degrees or whatever it was....with a 10,000 fpm ROD.
I shudder at the bit where the poor sods finally decide to push the nose down, only to have the stall warning reactivate........
I shudder at the bit where the poor sods finally decide to push the nose down, only to have the stall warning reactivate........
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I read NOT that they climbed, but they ascended, or, they were pushed, or, caught a severe updraft, and then wound up at 38,000 in a nose up condition, at below 60kts and thus literally out of control because at that time the controls would be inneffective.
The report is not that clear about how much time the pull-up lasted, nor how much time the PF later spent trying to push the nose back down again, so it is also possible that when the AP dropped out, the nose rose on its own, and the PF was trying to counteract that tendency, and was pushing down. I would have thought that the report would have mentioned that sequence of events if it happened that way, since it would have been readily seen on the DFDR. However, the report is very thin, so much could have been left out.
Will have to see the final report to see what might have given the pilot the impression he needed to pull the nose up, or if he was reacting to the effects of the AP dropout. That would also explain his mindset, and perhaps help explain why he didn't later put the nose down to recover, other than for a few short attempts.
The fact that the aircraft lost as much speed as they did also supports the fact that the the climb was due to a nose-up command, since it takes energy to climb, and if an updraft provided the energy, they wouldn't have lost as much speed as they did in the process.
Note that the aircraft didn't drop as low as 60 kts in the climb. That was an erroneous speed displayed in front of the pilot, and recorded on the DFDR, presumably as a result of the blocked pitot tubes. The report suggests that the aircraft's actual speed only dropped to about 185 kts, which is what two separate speed indicators said when they came back into correspondence, meaning the blockage in the pitots had likely cleared again at that point.
Last edited by ST27; 1st Jun 2011 at 07:32.
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Effect of the position of the THS
From 38 000 ft down to 0, the trim/THS was at 13° nose up.
Starting around 2 h 12 min 17, still well above 10000 ft, there was an apparent attempt to get out of stall: nose down stick with engines around 55% N1. It did not work out. I'm trying to understand how the position of the THS is related to that failure.
Questions:
- Can it be determined what the flight law was during that nose down input?
- Is this mode consistent with the THS remaining static?
- Does this mode allow full deflection of the elevator?
- Was getting out of stall feasible despite the position of the THS?
- Do procedures to get out of stall, as (I guess) practiced in simulator, include manual action on the trim to get the THS back to neutral or nose down (or on the contrary is it customary to assume autotrim will take care of the THS)?
- Do these standard procedures include extending flaps to some degree, which is not mentioned in the BEA report?
Full disclosure: I'm not a pilot; I'm an engineer working on systems where security (not safety) is critical, and I like to understand by myself how failures happen.
Starting around 2 h 12 min 17, still well above 10000 ft, there was an apparent attempt to get out of stall: nose down stick with engines around 55% N1. It did not work out. I'm trying to understand how the position of the THS is related to that failure.
Questions:
- Can it be determined what the flight law was during that nose down input?
- Is this mode consistent with the THS remaining static?
- Does this mode allow full deflection of the elevator?
- Was getting out of stall feasible despite the position of the THS?
- Do procedures to get out of stall, as (I guess) practiced in simulator, include manual action on the trim to get the THS back to neutral or nose down (or on the contrary is it customary to assume autotrim will take care of the THS)?
- Do these standard procedures include extending flaps to some degree, which is not mentioned in the BEA report?
Full disclosure: I'm not a pilot; I'm an engineer working on systems where security (not safety) is critical, and I like to understand by myself how failures happen.
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Could it be that the pull up by the PF was purely to follow his flight director cues that were demanding a pitch up due to an overspeed condition as well?
Could the FD have been commanding a pull up caused by the aircraft sensing an overspeed condition that arose either by the rapid increase of mach no. from hitting the relatively hot air in the top of or leading the top of a very active itcz night time thunderstorm, and/or positive local thunderstorm wind vectors?
I know of two jet aircraft that have lost control in the tops of tropical TS due to being put outside the envelope suddenly in warm TS air at altitude.
And by the way - great post Hundredpercentplease at #1179 - hats off!!
Could the FD have been commanding a pull up caused by the aircraft sensing an overspeed condition that arose either by the rapid increase of mach no. from hitting the relatively hot air in the top of or leading the top of a very active itcz night time thunderstorm, and/or positive local thunderstorm wind vectors?
I know of two jet aircraft that have lost control in the tops of tropical TS due to being put outside the envelope suddenly in warm TS air at altitude.
And by the way - great post Hundredpercentplease at #1179 - hats off!!
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HundredPercentPlease wrote:
"I too shall declare my interest: A320 Captain.
I really don't know where to start with this thread. So much noise, so little signal. The number of red herrings and long irrelevant side tracks is so great that no one can even start to address them.
The PF quickly and correctly diagnosed the situation. Loss of airspeed indication, resulting in AP/AT off and Alternate Law. He then incorrectly pitched up to 10° until the AoA was just 2° from the stall.
In this perilous position, the AoA increased again to 6° and the aircraft stalled. The response was incorrect with TOGA + pitch up.
So, two apparent errors. So much has been said about the wrong procedure being used (TOGA + pitch up is used in many other procedures) and a lack of training that I won't bother. But here is something frightening:
Most older Airbus pilots have done their time in cranky old jets and turboprops, where you fly by pitch. Everything is done by pitch settings - choosing, setting, adjusting, waiting and so on. However, in the world of the safety committee it is fine to pluck young lads straight from a Seneca and place them into an Airbus. To mitigate the risk, the flight director must be on at all times. Now all the cadet has to do is put the square in the centre of the cross. Never has a pitch been noticed nor noted.
I asked 5 first officers in the cruise to look me in the eye and tell me what pitch we were at (2.5°). 4 cadets answered between 5° and 10°
, and one ex TP guy answered correctly at 3°. Not much of a sample, but indicative I suspect.
The Airbus is a fine aircraft. It is conventional, and simple. On top is a thick layer of cotton wool, that should protect us from our silly mistakes.
Once the cotton wool is removed, we are back into a simple jet. The snag is that with the current drive to train/recruit people as quickly and cheaply as possible, not one of the recent arrivals has ever flown in "simple jet mode" (by pitch and thrust). Incredibly in our airline it is now even prohibited to take off with the flight directors off.
I feel sorry for the two FOs on the flight deck. Without the FD they will have been in new territory. Without the airspeed, it is no time to have to guess pitch settings and develop a strategy to keep the thing in the air.
I hope the airlines have a good think about this. I imagine the safety departments will, but nothing will happen due to the cost of recruiting people with experience on conventional types.
PS: Below 60 knots I imagine the stall warning is inhibited because there is not enough airflow over the AoA vane to make it accurate and trustworthy.
PPS: Has any Airbus pilot here ever actually heard the stall warning in the sim? "
My interest: 36 years flying militarily and commercially, 90 aircraft types as PIC, expertise in flight instruction, experimental flight test and more. Management degree in air transportation.
You are essentially right on the money! I do however think that the layer of cotton shouldn't be there at all, assuming the pilot in command is qualified, by my standards. FD is an aid only at pilot discretion, pencil pushers should be kept out of such decisions. From what I read here and other threads, and my study of NTSB accident reports, it is risky to fly as passenger nowadays, without a solution in the horizon. Until people like us both with our qualifications make the call on how to run an airline.
"I too shall declare my interest: A320 Captain.
I really don't know where to start with this thread. So much noise, so little signal. The number of red herrings and long irrelevant side tracks is so great that no one can even start to address them.
The PF quickly and correctly diagnosed the situation. Loss of airspeed indication, resulting in AP/AT off and Alternate Law. He then incorrectly pitched up to 10° until the AoA was just 2° from the stall.
In this perilous position, the AoA increased again to 6° and the aircraft stalled. The response was incorrect with TOGA + pitch up.
So, two apparent errors. So much has been said about the wrong procedure being used (TOGA + pitch up is used in many other procedures) and a lack of training that I won't bother. But here is something frightening:
Most older Airbus pilots have done their time in cranky old jets and turboprops, where you fly by pitch. Everything is done by pitch settings - choosing, setting, adjusting, waiting and so on. However, in the world of the safety committee it is fine to pluck young lads straight from a Seneca and place them into an Airbus. To mitigate the risk, the flight director must be on at all times. Now all the cadet has to do is put the square in the centre of the cross. Never has a pitch been noticed nor noted.
I asked 5 first officers in the cruise to look me in the eye and tell me what pitch we were at (2.5°). 4 cadets answered between 5° and 10°
, and one ex TP guy answered correctly at 3°. Not much of a sample, but indicative I suspect.The Airbus is a fine aircraft. It is conventional, and simple. On top is a thick layer of cotton wool, that should protect us from our silly mistakes.
Once the cotton wool is removed, we are back into a simple jet. The snag is that with the current drive to train/recruit people as quickly and cheaply as possible, not one of the recent arrivals has ever flown in "simple jet mode" (by pitch and thrust). Incredibly in our airline it is now even prohibited to take off with the flight directors off.
I feel sorry for the two FOs on the flight deck. Without the FD they will have been in new territory. Without the airspeed, it is no time to have to guess pitch settings and develop a strategy to keep the thing in the air.
I hope the airlines have a good think about this. I imagine the safety departments will, but nothing will happen due to the cost of recruiting people with experience on conventional types.
PS: Below 60 knots I imagine the stall warning is inhibited because there is not enough airflow over the AoA vane to make it accurate and trustworthy.
PPS: Has any Airbus pilot here ever actually heard the stall warning in the sim? "
My interest: 36 years flying militarily and commercially, 90 aircraft types as PIC, expertise in flight instruction, experimental flight test and more. Management degree in air transportation.
You are essentially right on the money! I do however think that the layer of cotton shouldn't be there at all, assuming the pilot in command is qualified, by my standards. FD is an aid only at pilot discretion, pencil pushers should be kept out of such decisions. From what I read here and other threads, and my study of NTSB accident reports, it is risky to fly as passenger nowadays, without a solution in the horizon. Until people like us both with our qualifications make the call on how to run an airline.
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Hi,
In most of the reports of accidents involving Airbus aircraft there is a constant:
Whenever it appears that some actions of either system (resulting themselves by actions of the pilot) have not been seen or understood by the pilot
It also appears that some informations (which could be very useful to the pilot) concerning malfunctioning or status of certain commands or automation are not show evidently to the pilot
This does not mean that Airbus is not a good aircraft (other reports about other planes were also reveals flaws) .. but he is cautious about this to become a constant
In most of the reports of accidents involving Airbus aircraft there is a constant:
Whenever it appears that some actions of either system (resulting themselves by actions of the pilot) have not been seen or understood by the pilot
It also appears that some informations (which could be very useful to the pilot) concerning malfunctioning or status of certain commands or automation are not show evidently to the pilot
This does not mean that Airbus is not a good aircraft (other reports about other planes were also reveals flaws) .. but he is cautious about this to become a constant
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TheShadow
from what I can judge, you seem to have a fairly consistent story there.
If, and it's of course all still speculation, but if you're right, then there's a number of things to be addressed in the aftermath.
It seems that automation, albeit no doubt helpful and safe in most cases, was a factor here, or rather: the way the automation behaves when pushed outside the anticipated envelope (Stall warning silenced / reappearing)
Another factor is the question what parameters are available to the pilots in those extreme situations. I wonder what the rationale is not to have an AoA display, even in situations when the AoA is clearly way out of the normal. (btw, how many AoA vanes are there on a 330? I know I've seen three on Boeing types)
Training of extreme situations is yet another area that will have to be revisited. Have airlines become overly confident that automation will keep the plane inside it's operatinal envelope at all times? After all, the most important function of the guys and gals up front is to save the day in the (unlikely) event of the automation "losing situational awareness" and handing the whole mess over to the humans.
Lastly, I still think that Airbus might have gone too far in removing tactile clues such as coupled movement of the side sticks (how does the PNF know what the PF is doing on the stick in extreme situations like this?) and, albeit not relevant in this case, tactile feedback on the thrust levers. Eyes and ears are limited bandwidth channels and to forego the additional, very direct, tactile channel does seem to be a less than smart engineering decision.
[edit]
so I just found that the A330 has three AoA vanes just as any other self respecting jet. Makes me wonder even more why it's not displayed everywhere since traditional logic would say "one for the CPT, one for the FO and one for the backup instruments". Oh well.
from what I can judge, you seem to have a fairly consistent story there.
If, and it's of course all still speculation, but if you're right, then there's a number of things to be addressed in the aftermath.
It seems that automation, albeit no doubt helpful and safe in most cases, was a factor here, or rather: the way the automation behaves when pushed outside the anticipated envelope (Stall warning silenced / reappearing)
Another factor is the question what parameters are available to the pilots in those extreme situations. I wonder what the rationale is not to have an AoA display, even in situations when the AoA is clearly way out of the normal. (btw, how many AoA vanes are there on a 330? I know I've seen three on Boeing types)
Training of extreme situations is yet another area that will have to be revisited. Have airlines become overly confident that automation will keep the plane inside it's operatinal envelope at all times? After all, the most important function of the guys and gals up front is to save the day in the (unlikely) event of the automation "losing situational awareness" and handing the whole mess over to the humans.
Lastly, I still think that Airbus might have gone too far in removing tactile clues such as coupled movement of the side sticks (how does the PNF know what the PF is doing on the stick in extreme situations like this?) and, albeit not relevant in this case, tactile feedback on the thrust levers. Eyes and ears are limited bandwidth channels and to forego the additional, very direct, tactile channel does seem to be a less than smart engineering decision.
[edit]
so I just found that the A330 has three AoA vanes just as any other self respecting jet. Makes me wonder even more why it's not displayed everywhere since traditional logic would say "one for the CPT, one for the FO and one for the backup instruments". Oh well.
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Corporate myopia
Everyone here agrees the pitots were flawed.
Everyone agrees AF process was flawed in not enforcing substitution.
Everyone here agrees the Airbus automation is flawed in the way it handles bad sensor input.
No one here will admit that the pilot training may be deficient too.
Corporate myopia?
Everyone agrees AF process was flawed in not enforcing substitution.
Everyone here agrees the Airbus automation is flawed in the way it handles bad sensor input.
No one here will admit that the pilot training may be deficient too.
Corporate myopia?
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FD is an aid only at pilot discretion,
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Delta T, the Lufthansa at 350 that preceded AF447 by 20 minutes on UN873 deviated 10 NM to the west. The Iberia following AF447 by 12 minutes was at 370 and deviated by 30 NM to the east. AF459 (an A330-203) following the Iberia by 25 minutes deviated first by 20 NM to the west, and then 70 to 80 NM to the east of the track, and was given permission to climb to 370. Neither the Lufthansa or Iberia deviations would have significantly affected fuel consumption.
AF459 at the time of its deviation would have been unaware that various centers were trying to contact AF447. (DAKAR contacted AF459 at 0411 asking it to try and contact AF447.)
AF459 at the time of its deviation would have been unaware that various centers were trying to contact AF447. (DAKAR contacted AF459 at 0411 asking it to try and contact AF447.)
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From what I read here and other threads, and my study of NTSB accident reports, it is risky to fly as passenger nowadays, without a solution in the horizon. Until people like us both with our qualifications make the call on how to run an airline.
Having said that....
I agree 100% that people with your experience, should be a voice in the aviation industry. The issue I see is a over-reliance on the "cotton". Automation and pilots must find the "comfortable" interface that advance the industry to even higher safety records. If you and your colleagues can help....than you should.
Originally Posted by Edmund
No one here will admit that the pilot training may be deficient too.
Training of extreme situations is yet another area that will have to be revisited.
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opherben -- We are getting to the stage where electronic instrumentation and control will be more reliable than humans. We are not there yet...too many things that can go wrong. Mechanicals, electricals, electronics, passengers(!) and GPS which is only available to us at Uncle Sam's pleasure. It will happen in time even if none of us reading this are alive to see it happen. So might we not expect this to be introduced by evolution while de-skilling pilots?