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WSJ article: AF447

Old 05-31-2011, 06:02 AM
  #31  
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Originally Posted by dojetdriver View Post
Agree. And my airline, who has proven to be SLOOOOOWWWWW to change, has done just that. It's no longer the standard PTS stalls with minimal loss of altitude, or gain of altitude in the (recovery), etc. It's real world training and recovery. One at high altitude (mid 30's), one on an approach (similar to the Colgan), and one on Take off with with a hard turn and trust reduction to initiate it.

Also, it's no longer a "checked" event on a PC/LOFT with the check airman debriefing how you "lost altitude in the setup and screwed you up in the recovery" or because you didn't complete the maneuver back to a specific heading/altitude/speed, etc. It's a trained maneuver, with the student being allowed to do what it takes to get the plane flying again without crashing. It's light years ahead of what I did previous at this airline, as well as my former.
This is what everyone needs to move to. I've been railing on this for years - a stall in a transport IS an emergency (given that you should never be there in the first place), and should be dealt with as such. To train otherwise is insane. It's been almost 30 years since Air Florida, and we as an industry still have learned nothing from these accidents, and still have people riding flyable airplanes into the ground.
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Old 05-31-2011, 08:15 AM
  #32  
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I doubt we will ever hear it but I would like to hear the CVR. I just find it hard to believe that 3 pilots were there and pulling back on the joystick and no one was yelling for throttles and or "forward on the stick".
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Old 05-31-2011, 09:56 AM
  #33  
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Originally Posted by Zoot Suit View Post
I doubt we will ever hear it but I would like to hear the CVR. I just find it hard to believe that 3 pilots were there and pulling back on the joystick and no one was yelling for throttles and or "forward on the stick".
Well, that's a good point. But remember, they were getting the crap kicked out of them in the ITCZ, it's night time, they have multiple failures going on, etc.

They may not have been able to tell what the airplane was "trying" to do, nor if the flight controls laws were behaving properly by their assessments, etc.

The PNF may have been task saturated with the ECAM. And the most important thing, where is the "stick" in the Airbus? It's not in the best view of the PNF. Also, since the other stick doesn't move, he (the PNF) has no visual cues as to how the flight controls are being displaced, or what the other guy is doing with the stick, etc aside from turing his head 90 degrees, while getting bounced up and down etc. Like I said, combine that with the rest of the fecal cinema they were in and it's probably not as easy to comprehend EXACTLY what was going on.
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Old 05-31-2011, 01:22 PM
  #34  
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Originally Posted by dojetdriver View Post
Well, that's a good point. But remember, they were getting the crap kicked out of them in the ITCZ, it's night time, they have multiple failures going on, etc.

They may not have been able to tell what the airplane was "trying" to do, nor if the flight controls laws were behaving properly by their assessments, etc.

The PNF may have been task saturated with the ECAM. And the most important thing, where is the "stick" in the Airbus? It's not in the best view of the PNF. Also, since the other stick doesn't move, he (the PNF) has no visual cues as to how the flight controls are being displaced, or what the other guy is doing with the stick, etc aside from turing his head 90 degrees, while getting bounced up and down etc. Like I said, combine that with the rest of the fecal cinema they were in and it's probably not as easy to comprehend EXACTLY what was going on.
Excellent points, especially the turbulence factor, it is entirely possible that the ADI was difficult to comprehend due to eyeball bounce, that is where the turbulence is so bad that one's vision isn't clear due to the eyeballs shaking inside the eyesockets. It is known to make reading instruments difficult to impossible... The lack of "cross feedback " from the sidestick system also a likely big factor.
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Old 05-31-2011, 02:33 PM
  #35  
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I fly the 320, which is the same control system laws as the 330.

There are several issues here. They are in a dark cockpit with multiple warnings, visual and audio. The ECAM must have been going crazy and there is little tactile feel in the Bus. Not that the Bus is a bad system, it is not, in fact it is very good. BUT, the MD or the Boeing you know what is happening (or at least have more data) because the control column moves with direct or at minimum direct/artificial feel. In this case, the other two pilots might not have even known that the PF was pulling full back. Then again, they may have all known. If their instruments are failing (perhaps more going on than we know) and they have no visual reference outside, they may not have realized what was happening. I imagine that they would have seen (and perhaps felt) the massive drop in altitude, but in the Bus world, you are supposed to be able to pull full aft and the plane will always climb. The stall protection operates perfectly, in NORMAL LAW. But these poor guys were in Alternate or perhaps even Direct law. This in Bus speak means there is limited or no protections available to the pilot. However, if you are trained on the Bus, you may not think about nose down and throttle on, because you are ingrained to rely on the prots for survival. Not saying it is right, just saying it is the way things are trained in the Bus.

The PNF would not know that the PF was pulling full aft unless he looked directly at the control stick, opposite his position AND it is dark on the deck in turb..... really bad situation. However even if the PNF knew that climb was being requested, he may not know they were in a stall. In the Bus world, you are not able to stall in Normal Law. However, these guys were in Alternate or my guess maybe Direct Law and that is an entirely different expectation to what one would consider at altitude on the Bus. When they state there are "no indications", I wonder if they had PFD or not. There were multilple failures including all three ADIRUs. What did they actually know? Was only their speed display unreliable or did they have "NO indications"? In the dark, in ITCZ, warnings on ECAM and training of Normal Law prots probably all worked agains these pilots. The throttle levers on the Bus do not work like a Boeing, so there is minimal to no feedback. However, I do believe they likely knew their thrust request but they may have believed they were in an overspeed condition. There is so much more to this story we have yet to learn.
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Old 06-01-2011, 11:19 AM
  #36  
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Originally Posted by UAL T38 Phlyer View Post
Because if you hit, say, mountain wave suffiecient to initiate Alpha Protection (ie, a stall warning), the autothrottles would go to TOGA. However, that might make you go faster than Mmo, and the jet would pitch-up to arrest the over-speed. This would re-trigger the alpha-prot, and round and round it goes. AND, you could go above max-rated altitude.
Just curious, but it that what was determined was going on where that Airbus was caught on video somewhere in Europe in a series of aggressive pitch ups, followed but pitching down, etc?
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Old 06-01-2011, 08:00 PM
  #37  
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Found this on Pprune:

AF447 wreckage found - Page 31 - PPRuNe Forums

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 donít 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 enginesí N1ís 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.
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Old 06-07-2011, 12:44 PM
  #38  
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Originally Posted by SparKen View Post
One question, does the AB have an AOA indicator?
Yes . . . and no. The plane has 3 AOA probes and uses AOA data for computations, but none of this information is presented to the pilots in an AOA indication.

Originally Posted by ImTumbleweed View Post
Based on your knowlege, did the crew have some sort of reliable (backup) indications of airspeed, altitude, attitude, and vertical speed.

Would the backup systems work?
Hard to say, with the known facts.

02:11Z:
Failure of all three ADIRUs
Failure of gyros of ISIS (attitude information lost)


The ISIS is the 'standby attitude indicator' on the Airbus. So, no back-up attitude. The pitot probes are also likely gone too (ADIRU = Air Data and Inertial Reference Unit), So, at least @ 02:11z, the back-up indications all 'appear' to be totally unreliable.

It's important to understand what an ADIRU is to an Airbus. There's 3 of them. Each is made up of the Air Data Reference (barometric altitude, airspeed, mach, angle of attack, and overspeed warnings) and the Inertial Reference (attitude, flight path vector, track, heading, accelerations, angular rates, ground speed, and aircraft position). Go here for a look @ some airbus manuals on the subject, though they discuss the old standby instruments, not the ISIS system.

That's an excellent analysis of the unspoken issues from PPRuNe, BTW, particularly the discussion of the impact of a fully deflected THS (trimmable horizontal stab) in the nose up position. Thanks for posting it here, 'Zoot'. It's a shame that the media is simply going with 'pitching up in a stall = pilot error', though I'm surprised to see so many posters on this forum so easily coming to the same conclusion. There is much more to this accident potentially than one sees @ first blush.
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Old 06-07-2011, 07:55 PM
  #39  
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I just have one question: if all backup instruments failed, how does the FDR know that they climbed 3000 feet before stalling? What altitude reference did the FDR use and was that available to the crew? I guess that was two questions.
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Old 06-08-2011, 08:29 AM
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Originally Posted by Singlecoil View Post
I just have one question: if all backup instruments failed, how does the FDR know that they climbed 3000 feet before stalling? What altitude reference did the FDR use and was that available to the crew? I guess that was two questions.
Warning: pure speculation!

The static ports would sense ambient pressure, ie, altitude.

It is theorized that the pitot ports iced up, but the static ports did not. Hence, you'd appear to have reliable altitude, but not airspeed. What exactly happens to an electronic standby instrument (the ISIS) when you 'fail' all three ADIRU's (or merely just the AD part, not the IR part), block up all the pitot ports, and spin down the gyro is not discussed in Airbus manuals.

Like I said, pure speculation. Hopefully, the official report will discuss what exactly it is theorized the pilots actually might have seen on their primary and standby instruments.
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