AF 447 Thread No. 12

[roulishollandais]

Hi interfrequentflyer...
When I was opening the link I found immediately the stat discussion "Averages and outliers" that I liked very much (math acuracy), despite what the author was saying was not new -Mandelbrot told that many decades ago as a part of his works on systems dynamic in finance (his work) and after that fractals- but always forgotten in actual works, airspace or finance included. and despite I did not understand why Winnerhofer gave that link in AF447.12
"We" have leaved and lost the traditional skils of aviation, but "we" did not accept the strict logic and math rules of the new IT world emerging in airspace. The result is dummy pilots who no more understand their planes and are unable to understand them. It is why I'm plaiding for a higher level in math, IT, physic in airspace, pilots included, and that has a price, the price of the modern IT world that we are not able to stop.

And I did not read "The C* continuum"... reading the comments on PPRuNe about C* I'm seeing that common acurate définitions are still missing. It is strange and paradoxal, because we see many planes are flying. In fact aswell militaries like gums or civilian like PJ2 with a great and safe experience of FBW both are flying with the very FIRST FEEDBACK used by human : Sight with eyes, on the natural or artificial horizon or Hud.
Effectively the Side stick works with Nz as the term "1/s" in the equation lets no doubt (A33Zab) , but both gums and PJ2 do not matter : the first adds the sight feedback to that équations (don't forget that the stick is always creating a transient and not a steady situation, ie starting a simple turn with bank), the second learns to do only little quiet movements giving time to the system to follow his understanding of action on the stick (still short around tenths of second).But many ordinary pilots have not that ability to counteract in fact these sytems done to correct low turbulence, and not able to correct heavy windshear (to be discussed) and are in big trouble when incidents happen.

[Machinbird]

Exactly - and that is why it has precisely nothing to do with a supposed design issue with C* in stall - they were not in C* in stall.
Would you like to check your facts sir?
The first stall occurred in Normal law and caused a drop to Direct law.
The stall at the top of the steep climb occurred in abnormal attitude law, which is also a degraded form of C* Law.
If XL (and G-THOF) illustrate any design flaw it is with underslung engines, not C* - but in my opinion every design decision has compromises, no design is perfect in every scenario, and what it really illustrates is the perils of trying to recover a pitch upset by adding thrust when your thrust line is below COG. Granted the underslung thrust line does not help the pitch up situation, but I think you are giving it too much credit. The little A-4 Skyhawk I used to fly had a THS also and it would do a dandy tailstand if the trim ran away nose up and that aircraft had the thrust line through the cg (or close enough). It is the THS being out of position that is the hazard, the underslung engines are just an additive problem. You expect the engine effects. You do not expect the unresponsive THS which may also be trimmed well away from normal airspeed range.

From what I can see, C* works a treat when it is working right. It is just that when it doesn't have correct inputs that is can be a handful to corral, particularly for the weak stick jockeys. For oldtimers such as myself, C*U is probably more intuitive, but FBW in general is extremely dependent on its data inputs for proper operation. How such degradation is detected and presented to the crew is an area that can still stand further examination and improvement.

[alf5071h]

Ian W, excellent points (#1195); you address the underlying problems.
Some further thoughts on these, but from a slightly different view.

The key point is what we assume ‘it’ be – “what’s it doing now” is generally automation focussed. An alternative is to questioning what is the aircraft is doing, what do ‘we’ want the aircraft to do (to achieve the objective), and what would the best means of achieving that; manual or auto. And if auto which modes, and are they suitable for the objective. The process is one of questioning the overall situation as opposed to accepting automation without question.

“What is it doing” implies the crew don’t understand, hold an inappropriate awareness, or are unable to relate current activity with a situation. Crews need to consider what aspects are required to understand the situation before choosing a course of action. Think before acting.
This approach would be radically different to the current mantra of ‘read the mode annunciators’.
It is impossible to gain a full understanding of what the aircraft is doing from a small set of two or three lights.

The industry has to turnaround the focal point of awareness; not autos, aircraft first, … Plane, Path, People; Aviate, Navigate, Communicate (with the autos), Manage (automation).
Older pilots may only have had one focus, the aircraft; extensive automation has turned this around, thus it’s time to rethink training and the mental approach to operations to accommodate these ‘automation’ changes.

“…automation surprise and cognitive overload” automation generated situations can be surprising, individuals will be surprise, but cognitive workload is manageable.
As above don’t attempt to determine the situation from lamps. Look at the instruments, the aircraft, the flight path, then consider automation - knowing what to look at and when – having knowledge of what is important in a particular situation.

[vilas]

Clandestino
Below is the link to SAFO on stall recovery. Actual accidents you will have to google.
FAA Issues SAFO For Practical Test Standards (PTS) Language | Aero-News Network (http://www.aero-news.net/index.cfm?do=main.textpost&id=a72cd8a0-1f80-4e52-b53c-83f42cacef6c)

[roulishollandais]

Note: I am not a pilot, nor a mechanical engineer. But I do write software and it seemed like a system of this kind could be implemented, tested, certified and put to good use by all Airbus aircraft in the future. I might have misunderstood how the fly-by-wire system works or made irrational assumptions, I am all ears to be told otherwise! Interesting that this software blogger is saying he doesn't understand how the AIRBUS FBW works:oh:

[mary meagher]

Can anyone answer my question about the PF in AF447....Pierre-Cedric Bonin.
It is often mentioned that he was a glider pilot. So am I. And glider pilots are commonly intensively trained to recognise and recover from unusual attitudes. Did Bonin hold any FAI certificates at all? where did he do his gliding? and how many hours and qualifications did he have in unpowered flight? I am not clever enough to discover the answers....perhaps someone who understands the French systems can help?

[CONF iture]

The report indicates that he had a "glider pilot's license issued in 2001", nothing more.
Apparently, part of the ab initio training at AF, the students spend one week in St-Auban.

"AF en quête de sécurité" min 41

dP_PNPhLFEs

[DozyWannabe]

I wish I could still find the page I dug up back in 2010 with the details. As best I can remember, it mentioned Bonin undergoing some kind of basic, intermediate and advanced gliding qualifications over a year or so - certainly more effort than a single week would provide.

[mary meagher]

Thanks for that, Dozy. So it wasn't just a quick ride to tick the boxes.
All the same I think a gliding background, especially the intensive practice in launch failure that should be covered before solo on a winch launch, must be a good background for understanding "what is it doing now!?" The stick is moved steadily back during the launch, but if the cable breaks, and you neglect to move the stick forward for the recovery, a stall and spin is likely.

[roulishollandais]

In the French system such informations can't be published unless the BEA report decides it is a safety clue useful to publish, or if the person himself does these information's public. Years ago they were abuses in displaying these informations, DGAC agents had been fired.

[CONF iture]

Look at the posted BEA video, how fast and gradual everything happened, bad that it does not incorporate the nz graph.
This animation has a G meter

BR5kFOHVnUU

[seagull967]

PJ2, thank you for the response.

I know this is a bit off topic, but thought I'd ask anyway. Does anyone happen to know what the F/O meant when he asked in reference to ozone "What’s that is it specific to FIT?” at time 2 h 09 min 01? What is "FIT"? I have never come across this acronym before, or maybe it is something so obvious that I am not seeing it?

[Gysbreght]

What is "FIT"?Just guessing: Front InterTropical, aka ZIC or ZCIT (Zone de Convergence interTropical) or in English: ITCZ (InterTropical Convergence Zone).

[Machinbird]

After listening to the "stall stall" part of CONF iture's sound track several times over, I've come to the conclusion that Airbus has done an excellent job of providing a warning sound that just naturally becomes part of the background commotion with repetition.:rolleyes:

Maybe they really should tell you something that you really might need to know like "Alternate Law" or as in the case of the Perpignan A320, "Direct Law." One time, clearly enunciated, should be enough.

[seagull967]

Gys,

Thank you, that is about as good a guess as any! I was wondering if it might be some local AF thing.

[PJ2]

Machinbird...regarding warnings blending with others and so on, in fact this accident is such an outlier in so many ways that the fixes applied by way of different messaging, auditory and visual alerting and so on, may rarely if ever be seen again, the risk being that, while this accident "uncovered" some aspects of the design that in these specific circumstances, crew included, we are not assured that there aren't other, different circumstances which, when they do occur and we have once again the benefit of years of analysis, new calls for design changes once again arise.

I'm not disagreeing with you so much as observing (as you have considered, I know) that the designers and the engineers must have done 99.9% of it right given the millions of unremarkable hours flown by Airbus crews, and the thirty-one A330 crews who, in the same circumstances, continued a safe flight to their destination.

The real question is, how far do we go in safe-guarding systems against inappropriate responses? What do we eliminate?...extremely rare conditions aside which potentially cannot be expected or even reasonably assumed?, more automation?, better-trained pilots? And if so, what justifies (and certifies) each response and who pays?, (because the airline passenger won't). How much can we expect (and pay for) from the designers, engineers and test pilots before we can all say, "enough has been done"?

Having watched and participated in this extended discussion on AF447 and related matters for five-and-a-half years now, I think it is important to be mindful of the very great amount of data "on the other side of the question" regarding automation, the Airbus, pilot competency and risk. I suspect it exceeds the usual 10-9 standard for engineering probabilities.

Is it "good enough"? Never, where loved ones' lives are concerned which is why accepting that 99.9% isn't good enough when statistics no longer apply...but, given how this industry does its work, will we know "not good enough" when we see it? The history of "not good enough" and the industry's response is deep in this industry which is why it has a safety record that is enviable by all other industries who must manage risk-to-life.

But it is not just not realistic to have it both ways - it is not possible to have it both ways and so the decisions on what may be reasonable to anticipate and what may be left up to resiliency, robustness, competency and probabilities remain silent until circumstances such as AF447 re-focus the discourse.

[seagull967]

PJ2-

I think the one thing that I would like to have seen done different on the design side is the installation of AoA guages.

The rest is on the training side, to include how to use the AoA guages. This crew never knew they stalled. There have been plenty of examples of other crews stalling without knowing it, and those included highly experienced pilots with aerobatic and military backgrounds. The factors that led to them not knowing are several and I know they are known to you.

Pilots are also not trained to know the automation well enough to make predictions on what it will do next, or should do next. The training in the hq in the high altitude regime is scant, and simulators do a poor job of replicating it all. Similarly, training in the hq in degraded modes, particularly at various q-factors is missing.

[PJ2]

seagull967, re, "This crew never knew they stalled.", and I think wouldn't have considered pushing the stick fully-forward and holding it there while going down.

I am beginning to appreciate more, primarily from the postings of the military guys who knew these areas and who knew full-stick deflection is always in the tool-kit, the view that even as we have four very clear metrics as to when the airplane is fully-stalled, such information is essentially unhelpful because it is benignly-given, benignly-referenced as a by-the-way in the manual, without any guidance whatsover (at the time) that fully-forward on the stick is what is required when stalled at cruise altitudes. One is not going to do this when terrified and going down - that is why stall training is necessary, but that point has been thoroughly made.

For this reason I think an AoA guage may not have helped, because "fully-forward on the stick for a full minute" would seem suicidal and certainly not natural or intuitive. From the sim experiments, (the replication was quite good even as it is extrapolation), it took 45" and 15,000ft to unload, (to use Machinbird's original term) the wing.

As an aside, you could watch the AoA on the FMC using the ACMS parameters page...but it wouldn't be helpful in these circumstances!

[seagull967]

PJ2,

I somewhat agree with you, but I think that if you saw an AoA guage with a CLEARLY defined "red zone" and you are in it, with proper training, a pilot might just do the right thing. Proper training is the key, they have to SEE it in the simulator, not just talk about it. The combination would be quite powerful, and if that does not work, there is nothing except some of the concepts of automatic stall recovery with extending vanes or something similar (not great ideas IMO).

[vilas]

seagull967 and PJ2
AF447 pilots at that point of time did not have the training and technique to deal with the situation. They put the aircraft beyond extremes of flight envelope. You cannot have training solutions to recover from that. Like the captain who barrel rolled the 747 and recovered miraculously do you need training for this how to do it? The main point of training must be that in Airbus alternate law never grab the stick and apply pitch inputs. It maintains the flight path so just look after the bank. Why does any one apply pitch input any way, to change the pitch isn't it? How can that be done without looking at the pitch? This knee jerk reaction initiated and sustained till it didn't matter anymore caused the problem. It was one off irrational act for want of procedural knowledge. You cannot keep trying it out to perfection. Just don't do it is enough.

[RetiredF4]

Although you are right for this case in following PJ2' s early recomendation to do nothing, the conclusion that training in high altitude manual handling and stall avoidance or recovery training for such events is not necessary is premature.
AF 447 could have dropped into direct law as any aircraft in the future could do as well where control in all three axis has to be applied immidiately. Another day, another situation, anouher fault and we go again.
A pilot has to be trained to be able to grab the stick and maintain the necessary attitude througout the complete flight envelope and be able to recover from situations, when this flightenvelope is exceeded by whatever cause it may be.

In the video Confiture posted just some posts before, watch the loadfactor. It is below the normal 1g for 25 sec prior the stall entry and it is nearly consecutive 60 sec below 1 g after the stall enty. Even when pulling the loadfactor was below 1 g. The human body is unfamiliar and very succeptable to reduced g loading, and it is not known to be accompanied by stall. Without physical training expierience of such a situation, with unreliable airspeed, no AOA and no loadfactor indication, how should they have been fully aware of their situation? We are talking in hindsight here, we have analysed and studied all available material, have looked at the FDR second by second, studied books and all available sources and have now a totally different knowledge base then they had during that night.
We know that they did not react to the stall like they should have, but besides the possibility that they were not able to identify in being in a stall they may have reacted on their knowledge base, but didn't know how much nose down stick input was required, how long it was required and how 0 g really feel. "I have no control......" were Bonins words.

[Goldenrivett]

vilas,
This knee jerk reaction initiated and sustained till it didn't matter anymore caused the problem. It was one off irrational act for want of procedural knowledge. You cannot keep trying it out to perfection. Just don't do it is enough.
I agree. But how do you detect it early if you don't have active side stick controls fitted? See Page 4.
http://icatee.org/wp-content/uploads/2012/06/f-zu110722en.pdf

"At 1 h 00 min 27 (point n°2), the PNF manually disengaged the AP by pressing the takeover pushbutton on the side-stick. A pitch-up input on the PNF’s side-stick going as far as 3⁄4 to stop was recorded for 6 seconds. This input was accompanied by an input to bank to the right then left. The PNF stated that he did not remember these inputs."

[vilas]

Goldenrivett
I am not against active side stick. I remember having read 7 or eight years back airbus gave very serious consideration to this but never implemented it. But the side stick is on one side so unless you kept your hand there you may still miss it. In AF447 they were flying without looking at PFD for most part and that I find very strange. It was a clear case of mental confusion may be caused by fear because they knew something was terribly wrong and were unable to figure it out. As you know average inputs into side stick are very small and a startled response in pitch has the possibility of causing excessive destabilisation. Nothing happens if you don't do anything for a few seconds to investigate.

[PJ2]

It's very old ground now, but to re-introduce the counterpoint, there is no evidence whatsoever that interconnected CCs are more likely to aid stall recovery and independent SSs.

In fact there are more fatal stall accidents in aircraft with CCs than with SSs.

A CC that is full-back-in-the-PM's-stomach is not a factor in recovery. I can't think of any such accidents where one crew member took action and pushed the stick away from his/her stomach and fully-forward to get the nose down in order to unload then unstall the wing.

In the few accidents I am aware of, the CC remained near/at full aft position until impact.

The problem is not "CC vs. SS" and therefore the solution is not the interconnection of the latter. The data just isn't there, whereas both a working stall warning throughout the entire flight regime and a THS that stops moving with the first stall warning do have data and therefore cause for further examination as does the installation of an AoA indicator.

[seagull967]

PJ2,

Absolutely. People tend not to realize the lack of salience the cc position has in a situation like this.

[Clandestino]

That is no excuse for writing an ops or a training manual that doesn't educate as well as train. You have to know how your system works to operate it professionally.

I have lost count how many times I've quoted preamble of Airbus manuals on PPRuNe; they are not intended to teach basic flying concepts. Pilot who is training on Airbus will easily relate what is written with what he experienced in sim or aeroplane. PPRuNer who has no idea about basic instrument flying, airline training and operations, after reading FCOM usually finds excuses to let his imagination run wild, resulting in spectacularly flawed and somewhat hilarious theories on how Airbus FBW works.

You are carrying the trusting public in your aluminum tubes with wings.So? Unlike PPRuNers disconcerted with Airbus flight system architecture, extreme majority Airbus pilots do understand and operate their machines correctly. If all the BS about Airbus FBW written here were true, there wold be no need for BSers to flog dead AF447 horse as there would be dozens of fresh accidents to pontificate about.

Since we are discussing AF 447, we may wish to remember that in this case airspeed indications had gone on holiday thanks to a voting procedure. (And some ice in the tubes). Granted, that eventually resolved itself but by then the crew were behind the aircraft.There is no voting procedure for speed displays. Vsw is displayed in ALT2. By the time of continuous stall warning, ADR1 was measuring correct speed for about 14 seconds. By the apogee, pitot3 was unblocked too.

It's a moot point anyway, stall warning and buffeting were very well present.

So what does explain that, in your humble opinion?It's self explanatory for anyone who has a slightest clue about flying but I guess I have to bring it down to level understandable to average PPRuNer: if one is below desired altitude, one has to climb to it. If one is above desired altitude, one has to descend to it.

The result is dummy pilots who no more understand their planes and are unable to understand them.So either the dummyness of pilots who no more understand their aeroplanes is bringing total number of fatal accidents (despite increasing number of flights) every year to record low or your comment is totally ignorant and somewhat offensive.

It is impossible to gain a full understanding of what the aircraft is doing from a small set of two or three lights. Report has made it pretty clear that left to her own devices, F-GZCP would have done nothing significant.

Below is the link to SAFO on stall recovery. Actual accidents you will have to google.No search engine can change the fact there was none as described in US.

Issue with approach to stall recovery that emphasizes minimum altitude loss is not that it's wrong (it isn't) but that it is too narrow in scope. It does not prepare one for high altitude event, full stall, or low altitude event with mistrimmed stabilizer. So my type now has universal procedure that lays burden on the pilot; thrust - as required, trim - as required. Better be sure you make it right first time.

This crew never knew they stalled.Exactly. Despite forcing aeroplane to climb at RoC and pitch dangerously unsuitable for cruise. Despite climbing high above optimum and maximum altitude. Despite losing control of the aeroplane. Despite warning systems shouting "STALL STALL" at them.

I somewhat agree with you, but I think that if you saw an AoA guage with a CLEARLY defined "red zone" and you are in it, with proper training, a pilot might just do the right thing.Say, what was the right thing done that enabled other 36 crews to survive UAS in 330/340s? They didn't have AoA gauges.

AF447 pilots at that point of time did not have the training and technique to deal with the situation. Maybe it would be useful to define "situation".

They put the aircraft beyond extremes of flight envelope. You cannot have training solutions to recover from that. So, avoid 'em.

The main point of training must be that in Airbus alternate law never grab the stick and apply pitch inputs. True but TAM A330 incident on 12 11 2003, described on the page 87 of final report proves that even extreme ham fistedness, on A330, flying at cruise level in alternate law is not necessarily lethal.


It is below the normal 1g for 25 sec prior the stall entry and it is nearly consecutive 60 sec below 1 g after the stall enty. Even when pulling the loadfactor was below 1 g. The human body is unfamiliar and very succeptable to reduced g loading, and it is not known to be accompanied by stall. Without physical training expierience of such a situation, with unreliable airspeed, no AOA and no loadfactor indication, how should they have been fully aware of their situation?For Finnegan's sake, it reaches 1.5 g in initial pullup, gets to +0.6 G minimum and then mushes between +0.75 and + 1.25 G for the rest of the flight. It's nothing unusual even for airliner!

I agree. But how do you detect it early if you don't have active side stick controls fitted?Like this:
Lufthansa A320 incident at Frankfurt. (http://www.skybrary.aero/index.php/A320,_vicinity_Frankfurt_Germany,_2001_(AW_LOC_HF))
Questions?

In AF447 they were flying without looking at PFD for most part and that I find very strange.No! Both pilots verbalized loss of airspeed indication and CM2 kept roll very well under control so he must have been looking at PFD.

[PJ2]

On salience of position...

The Airbus SS movement is measured in cm's so visual displacement cannot be accurately judged. In terms of tactile sense, if an SS is interconnected, one cannot know by feel or sight where the "null" point is. Small SS movements can result in significant changes in flight path. The initial SS displacements which occurred in AF447 to pitch the aircraft up eventually to 15deg would have been momentary, (meaning 'not steadily applied' but varying), and perhaps 2 cm's, 4 at the most. CC movement for the same result is as you say, small...may be the same numbers but in inches. Approximately...

It is only during the stalled-descent that one sees full-aft CC displacement in the accidents I was thinking of and by then if full-forward CC or SS isn't held in until the wing begins flying again, the airplane does not recover. Some call that a deep stall, but I'm old-fashioned because these stalls are recoverable whereas a deep stall is not; AF447 was recoverable; some say (and have calculated) down to FL100.

[CONF iture]

The Airbus SS movement is measured in cm's so visual displacement cannot be accurately judged. In terms of tactile sense, if an SS is interconnected, one cannot know by feel or sight where the "null" point is.

Helicopter pilots say otherwise where flight control command displacements are known to be minimal ...

It's very old ground now, but to re-introduce the counterpoint, there is no evidence whatsoever that interconnected CCs are more likely to aid stall recovery and independent SSs.
Interconnected CCs provide a first hand information to all crew members on the flight deck that Independent SSs just unfortunately suppress.

[vilas]

Clandestino
Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying? Sure in alternate law he had to do only that provided he had not given any pitch input. The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal.

[seagull967]

Ah, so easy to sit in your chair in front of your computer and think "that would not have happened to me..." Maybe you're right. Maybe. I know for a fact I could get a very high percentage to do the same thing this crew did with the right set up. Nothing like the wisdom of hindsight bias to make it all seem so obvious.

[Machinbird]

Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying? Sure in alternate law he had to do only that provided he had not given any pitch input. The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal. Vilas, that is what a roll PIO will do to a pilot. Destroy his faith in his flight control system. Mentally exhaust him. Terrify him.

All circumstantial except for one thing. Just why was AF447 oscillating in roll during those first 30 seconds?

http://home.comcast.net/~shademaker/AF447RollBehavior.png

Who here has had experience with any form of PIO?
Virtually no one

[RetiredF4]

Clandestino
For Finnegan's sake, it reaches 1.5 g in initial pullup, gets to +0.6 G minimum and then mushes between +0.75 and + 1.25 G for the rest of the flight. It's nothing unusual even for airliner!

When your management get's notice that you fly your airliner like that in daily flying, or even that it is usual for you to expose your passengers to such flying, then you get fired. If you do it in stalled situation, you might get killed.

Expieriencing continuous below one g for first consecutive 25 seconds and later for uninterrupted 60 seconds is unusual, whatever you say otherwise. And for this crew it might have been more unusual to decrease the g to 0g as needed for recovery for even longer time, as they never had been exposed to such a situation.

[vilas]

Machinbird
PIO as the word suggests doesn't happen. It is made to happen. Again we come back to the same point. First you make irrational pitch input then create PIO in roll and forget about the pitch totally and a training programme that caters for all this, You may have to select commercial pilots from aerobatic teams.

[Goldenrivett]

Originally Posted by Clandestino
Like this:
Lufthansa A320 incident at Frankfurt. (http://www.skybrary.aero/index.php/A320,_vicinity_Frankfurt_Germany,_2001_(AW_LOC_HF))
Questions?

"However, the bank angle increased continuously up to approx. 22°. With the commander’s call out :“I can’t do anything more“ the first officer took over the controls with the words “I have control“ and pressed the TAKE OVER PUSH BUTTON."

If I understand your brief explanation correctly then you are suggesting that PF keeps the PM informed of his SS movements verbally, in order to enhance their mutual SA of the control input?

If they had active SS fitted, then the cross wired controller's input would have been cancelled out by the other side's controller and the problem recognised during taxi checks with Zero roll commands. (More easily recognised than Left / Right confusion).
http://aviationweek.com/technology/active-sidestick-controls-make-commercial-debut

But you're right, why should we discuss ideas about how to improve such a perfect system.

[Machinbird]

Machinbird
PIO as the word suggests doesn't happen. It is made to happen. Again we come back to the same point. First you make irrational pitch input then create PIO in roll and forget about the pitch totally and a training programme that caters for all this, You may have to select commercial pilots from aerobatic teams. Vilas, unless you get hold of a defective aircraft, you yourself are never going to experience a roll PIO (also known as Aircraft Pilot Coupling) in your career, you already have the Low Gain touch.

BTW, I think your statement about the irrational pitch input is backwards with the creation of roll PIO. In AF447, The roll PIO started immediately. The pitch excursion followed in the next few seconds.

There have been videos of other Airbus pilots who have a large amplitude (High Gain) control technique that may well be a hazard when suddenly confronted with an unexpected drop to a roll direct condition-particularly if it happens in cruise. I do not know for a fact that this is an actual problem, but logic tells me that it should cause those people problems in that circumstance.

To suggest that a Pilot In the loop Oscillation (PIO) is made to happen is deceptive. Yes the pilot is driving the oscillation due to his control inputs.
No he is not doing it deliberately. He is merely using the controls in the manner that he has been accustomed to and is getting an unexpected and undesired result. The unusual behavior grabs your full attention. This attention grab pulls the pilot out of his trained response pattern. It is as if a poisonous snake has suddenly been dropped onto your flight deck-it demands your full attention.

If you have never experienced a PIO, count yourself fortunate. They are rare but dramatic. The A320 has experienced roll PIO resulting in a missed approach on several occasions. I would not be surprised if the FCS has subsequently had its software modified in subtle ways to reduce the likelihood of future occurences.

Stopping a PIO is usually easy-just get out of the loop-let go of the controls. Then when the aircraft stabilizes, gently apply only the minimum control input necessary to achieve your objective. Has anyone reading this actually received training in this subject?

From what I am able to observe. the subject of PIO/APC is an aviation myth to most pilots. Something they will never confront and do not need to know about. Trying to explain PIO to professional aviators who have never seen it is like talking in a vacuum.:sad:

[Clandestino]

But you're right, why should we discuss ideas about how to improve such a perfect system.It's not perfect. As any aeronautical system, it has its compromises and drawbacks. Yet, despite many PPRuNers claiming otherwise, it is well understood and service proven.

What is the point of the discussion? If those who are making bold statements about it have no idea about: aerodynamics, aeroplane systems, aeroplane performance, instrument flying, multi-crew operations, state of the pilot training today, that moderate turbulence starts at 0.5G so 0.25 is light or that ten degree roll is really insignificant even in transport aeroplane terms, then it really says a lot about the participants in the discussion but not much about the subject matter.

If I understand your brief explanation correctly then you are suggesting that PF keeps the PM informed of his SS movements verbally, in order to enhance their mutual SA of the control input?Of course you don't. Point is that LH captain clearly stated he lost control and FO has promptly and correctly taken over. Completely unlike AF447 where airspeed indication failure was quickly recognized but nothing was done about it, right copilot stated he lost control but would not let one in the LHS to try to regain it and CM1 anyway instead of taking over and returning the aeroplane to its level, couldn't think of anything better than calling the captain from the bunk to sort out the mess. Nobody said anything about any warning. No "disregard" or "non standard" could be heard. As very wise man once said:

Communication, an utterly vital element to Crew Resource Management regardless of aircraft type. Whenever we find ourselves in a situation of ‘unease’ we need to be vocal about what we are thinking but also what we are doing. Once others are aware of your concerns they can be addressed.

Another point that in modern MRJT or LRJT, what your significant cockpit other as PF, AFCS or even you yourself are doing with controls is of no interest to you as long as the aeroplane follows the desired flight path. Whether control input is appropriate is checked on PFD, not by looking at or touching the yoke.

You may have to select commercial pilots from aerobatic teams.SilkAir used to employ former Black Knights pilot.

Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying? Correct, but this strangeness is not limited to instrument flying. A pilot that forgets the basics, tries to make the aeroplane climb where it just can't and holds the yoke/stick into the stall which is only interrupted by ground collision was described by Wolfgang Langewiesche in 1944.

The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal.Absolutely! Asimov has called it "reptilian brain", Kahneman "system one" but they agree when it takes over, any rational thought gets sidelined.

Ah, so easy to sit in your chair in front of your computer and think "that would not have happened to me..." It is easy and absolutely wrong, that's why I did not and will not say that. Experience of the latest confirmed victims of the impossible climb syndrome among ATPLs is as follows:

RHS: 6900 hrs, 6064 on type
LHS: 14 268 hrs, 6161 as captain on type, type rating examiner.

What little we know so far is that it can happen to anyone.

[wiggy]

Who here has had experience with any form of PIO?
Virtually no one

Well there's at least one here who has, on a FBW type, on finals:eek:..and the big clue as to WTF was going on and what to do about it was the position of the control wheel verses the aircraft's behaviour.....

Not sure if that's going to further the debate or not......;)

[Machinbird]

Care to elaborate a bit?
Were you the oscillator or the oscillatee?:}

[seagull967]

Machine,

RE APC, well put. It has even caught low gain pilots off guard, particularly when coupled with a startle situation or a sudden ramp up in a tight tracking task. Flight test pilots have seen it, and the NRC even stated that there has not been one FBW or augmented hq aircraft that has not had at least one APC event during either flight test or in operation.

[Goldenrivett]

Originally Posted by Clandestino,
Another point that in modern MRJT or LRJT, what your significant cockpit other as PF, AFCS or even you yourself are doing with controls is of no interest to you as long as the aeroplane follows the desired flight path. Whether control input is appropriate is checked on PFD, not by looking at or touching the yoke.

Better tell BAE they are wasting their time then.

"The biggest drawback of the “passive” sidesticks now used in civil aircraft is the lack of control feedback from the aircraft or the other pilot."
"This ensures both sidesticks move together in response to both pilot and autopilot commands, providing crew situational awareness equivalent to conventional pilot controls, says BAE."
"But the biggest advantage claimed for active over passive sidesticks is that both pilot and copilot controls track each other at all times. “This provides good situational awareness between the pilots—they can both see and feel their sidesticks moving,” says Taylor."

Active Sidestick Controls Make Commercial Debut | Technology content from Aviation Week (http://aviationweek.com/technology/active-sidestick-controls-make-commercial-debut)

Originally Posted by Clandestino
If those who are making bold statements about it have no idea about: ...... multi-crew operations,
Do you have any idea about multi-crew operations?

[CONF iture]

Communication, an utterly vital element to Crew Resource Management regardless of aircraft type. Whenever we find ourselves in a situation of ‘unease’ we need to be vocal about what we are thinking but also what we are doing. Once others are aware of your concerns they can be addressed.
That's where Control Columns have the advantage to tell the PM what the PF is trying to achieve.

Whether control input is appropriate is checked on PFD, not by looking at or touching the yoke.
What happens on PFD is not necessarily the consequence of a control input.

[wiggy]

Machinbird

Care to elaborate a bit?
Were you the oscillator or the oscillatee?

:bored: I was an interested "bystander/bysitter" ....but not for long :eek:

Can't say much...but

FWIW, me PM, PF is handflying. On final the aircraft starts abruptly oscillating in roll...Your's truely thinks "WTF" ? Wake vortex/Flight Control problem? Are we controlling the aircraft or not? ... I then see, out of the corner of my eye, the magnitude and phase of the control wheel inputs being applied....Seeing the control wheel fully over with the aircraft already rolling back through wings level and heading towards the control input is a heck of a stimulus/big clue, even I can pick that one up... Roll inputs terminated..;) Aircraft stops oscillating and subsequently lands OK.

FDR trace examined by various interested parties. PIO most definitely diagnosed.

Now I'll admit to being an ex "basic" QFI which kind of also colours my POV but there's no doubt in my simple mind that being able to see your colleagues control inputs and see/feel the aircraft's response to the same might sometimes be of just a little use.....:ok:, but having never flown an "A" I'm not really able to objectively enter the A vs. B debate...

[Qantas_A380]

Why does sidesticks keep getting brought up in the debate about AF-447?

Panic Pull is a syndrome that affects all types of flight control interfaces. I'm just a small time private pilot and it was drummed into us during training to trust the aircraft and don't fall back on your instincts.

I have an idea - what about a stall warning system that gets progressively louder & louder the longer pilots fail to heed it? It might just be enough to get a pilot to "snap out of it" when they've gone into instinctive mode and push the nose down when in a stall.

Also, in Colgan 3407 the stick shaking caused the pilot flying to instinctively pull up and stall. So in some situations a yoke may help the other pilot identify a stall there are other situations where it may actually cause a reflex panic pull. Both systems are completely safe and are equally as prone to "panic pull" type stall situations as we've seen on both types in the past.

[CONF iture]

Panic Pull is a syndrome that affects all types of flight control interfaces.
Except that there is no panic pull in AF447, all the time the right seater has been verbalising his concerns, trying to understand the situation.
The time all on board have been fully pulling the sidesticks is at the GPWS warning ... and this is part of the Airbus procedure.

[Machinbird]

:bored: I was an interested "bystander/bysitter" ....but not for long :eek:Wiggy, your description of that PIO incident is fairly typical. It usually takes a second person freezing the yoke to stop a PIO because the the flying pilot is too immersed in the problem to realize what is going on.
Afterwards, your PF was probably very confused about what had just happened, right?
How big were the roll oscillations?

About all a PNF on an A type aircraft can do is take control. PF will probably be so highly stressed that his/her ears may not work.

FWIW, you are only the third person I've encountered who has seen a PIO up close and personal. Thank you for taking the time to respond.

[wiggy]

Afterwards, your PF was probably very confused about what had just happened, right?

Yep, just a bit...:ooh:

How big were the roll oscillations?

That, in hindsight, was the interesting bit :uhoh:...The trace showed a max on the final excursion of merely a tad over 10 degrees, but given the circumstances (night, somewhere on finals) and above all the abruptness of the control reversals it felt like a heck of a lot more....I would hate to experience a roll PIO that really got going...

[Lonewolf_50]

Clandestino: Wing Commander Spry's point is of course agreed. In other news, fish swim.

As to your bit about manuals, you can't have it both ways.
Either is it "too complicated to explain" or it isn't. Make up your mind.

Thanks you for the usual Clandestino style in playing the internet argument game.
As to your last point: it could happen to anyone.
Indeed.
In other news, fish swim.

[roulishollandais]

As already said in a AF447 thread, I'm interested by degenerating dutch roll since 1979, and was creating only in 1992 a method to stop it with greater efficiency than just put hand off the stick and feet on the floor. I recovered with bank never more than 30°, lost less than 1000 Ft, in less than 30 seconds (MD83 Sim in Helsinki).
Before that, the other crew -6000 hours on type- lost 11000 Ft, understood nothing, flying right and left on the back, with overspeed, alarms and tutti quanti. The instructor -in flight instructor too- was not able to comment, and rejected the idea to ask me how I had done, himself had many thousands hours flying Learjet....
I never found an editor to publish my method.

1. As Machinbird said it, in AF447 the roll oscillation started immediately, and we know it was after the law change, where the roll rate has been modified (increased with facto 4 if I remember well) and get different from pitch rate.

2. In that situation no need of panic or starttle factor to think " I will immediately get level again pulling the stick right or left to stop the roll" and attention is immediately captured forgetting to watch the pitch. In that bank correction the good pilot is the quickest to counteract the bank change... Imagine your body being suddenly at 10° from vertical ! You think only to get vertical again and don't fall (I liked Machinbird's snake comparison!)
Since that first moment, if never trained to that situation in the Sim and theory of systems, you are on the bad way...

The crash of the KC-135 in Kyrgistan in a dutch roll shows that roll PIO was not enough taught..… when taught - in airlines it is never taught.

[Machinbird]

How big were the roll oscillations? That, in hindsight, was the interesting bit :uhoh:...The trace showed a max on the final excursion of merely a tad over 10 degrees, but given the circumstances (night, somewhere on finals) and above all the abruptness of the control reversals it felt like a heck of a lot more....I would hate to experience a roll PIO that really got going... I would like to point out to the casual observers here, that the PIO here that Wiggy described was less in amplitude than the AF447 initial roll excursions (if I correctly understand the meaning of the 10 degree roll readout of Wiggy's example.)

One way a problem can occur is when the flying pilot tries to zero the roll rate rather than just bring the wings back to level. When the roll rate is high enough, the eye is drawn to the motion and it is easy then with a large, inherently slow rolling aircraft to predict the roll rate and provide a synchronous opposite phase aileron input. When you start responding to rate signals though, you advance the timing of your control inputs by 90 degrees of phase angle and this has the effect of driving an oscillation. You can see this effect in the chart I posted here: http://www.pprune.org/tech-log/539756-af-447-thread-no-12-a-63.html#post8868131

There have been tests run on the threshold roll rate needed to trigger a roll rate cancelling response from a pilot. From memory, it is in the 10-11 degrees per second rate which AF447 achieved in its initial roll oscillations.

I would hate to experience a roll PIO that really got going.. I would like to echo that comment. Until you have experienced a PIO/APC event, you cannot imagine the impact it can have on your ability to control the aircraft.

[seagull967]

Machinbird,

Excellent post. Do you happen to have a pointer to the research on role rate threshold to gain that pilot response? Anything you might recall would be helpful.

[roulishollandais]

Hi Machinbird,
In your figure the roll rate is maximum/minimum when the roll angle is zero (wings passing the level position).
The important is to train roll oscilations in simulator.as well as law of flight transitions .:)

[Jimmy Hoffa Rocks]

Interesting to note that the FAA places more emphasis on jet upset recovery than in the EASA and in Europe.

Airbus does little training on recovery from unusual attitudes, re PIO, etc, in their Type Rating as well.

This should be improved on in Europe. no ?

[gums]

Not sure if we all understand the "feel" of the roll/pitch commands in most FBW implementations, and what you see and get when stirring the stick.

The best I can find is the majority of FBW jets command roll rate with yokes or sticks or sidesticks. Not bank angle, but roll rate. Anybody else here with a different experience?

The Viper roll rate could be trimmed, as could the gee command for pitch. Airbus appears to be pure roll rate for lateral stick and the gee command is corrected for pitch with fore/aft stick( and you can't trim for roll rate or gee). The 'bus also stops you at certain bank angles if in the various laws above "direct".

So if you let go of the stick you are gonna get a zero roll rate command for the 'bus and trimmed rate command for the Viper. You may not maintain your bank angle, but the system is giving her all it can. With my leading edge flap failure configuration I could not trim out for roll. But could trim yaw. I had to hold 16 - 17 pounds of left stick until I landed.

So to help roll problems or roll rocking you relax pressure/degrees of stick displacement and then go from there. The computer will try to keep you at the trimmed roll rate - zero for the 'bus. If the bank angle keeps increasing or decreasing, then you have problems with the control surfaces or a truly screwed HAL. The exercise is even easier than with the old conventional controls whether direct from cables or hydraulics.

You only get into trouble trying to deal with unusual roll rates ( and maybe some yaw back and forth). We saw that with the 'bus outta JFK when the tail came off and the KC-135 in one of the 'stans.

I can understand the inertia effects for a big jet like the 'bus or 777 or .... Even if HAL is doing its best, roll may take a second or two or three to stop. I bet it also took a second or two to establish a high roll rate, huh?

enuf of flight control laws and implementations from this old fart...

[Machinbird]

enuf of flight control laws and implementations from this old fart... As one old fart to another :p, roll direct is not a roll rate law. I know you know this, but it somehow got omitted in your story.

That is one of those step changes that can happen when control laws change and that the pilot flying had better be aware of.

Problem is, the law changes are not enunciated verbally by the aircraft system, and if the aircraft suddenly rolls sharply in response to a now excessive pilot roll input, the pilot may not see the annunciation on his PFD for a long time which can allow other significant problems to develop.:eek:

Instead the aircraft seems to prefer to play C chords and shout loud Stall-Stall warnings that are rapidly tuned out by a crew that needs a quieter environment to figure out WTF just happened.
Anyone else think there might be room for improvement in the annunciation of Control Law changes?

[roulishollandais]

The Viper roll rate could be trimmed, as could the gee command for pitch. Problem is, the law changes are not enunciated verbally by the aircraft system, and if the aircraft suddenly rolls sharply in response to a now excessive pilot roll input, the pilot may not see the annunciation on his PFD for a long time which can allow other significant problems to develop. Wonderful Viper's systems ! And, of course, pilots were trained to use these trims :D Airbus may Copy better and learn from our dear old farts

[Clandestino]

Better tell BAE they are wasting their time then.

"The biggest drawback of the “passive” sidesticks now used in civil aircraft is the lack of control feedback from the aircraft or the other pilot."
"This ensures both sidesticks move together in response to both pilot and autopilot commands, providing crew situational awareness equivalent to conventional pilot controls, says BAE."I don"t and have never intended to. If technology in 2010s can render force feedback sidesticks as useful and reliable as artificial feel systems of 1960ies or no-feel sidesticks of 1980ies - good for everybody. That they will provide better SA is marketing hype as much as "My concierge can fly it" or "Our aeroplanes feel natural to pilots" were.

Do you have any idea about multi-crew operations?I am not subject of this thread. Do you have any relevant question?

Originally Posted by ClandestinoI made it pretty clear who originally posted it so I object your misattribution.

What happens on PFD is not necessarily the consequence of a control input.Ah, we are getting somewhere. So why would F-GZCP first follow the stick inputs, then abruptly stop following them?

FDR trace examined by various interested parties. PIO most definitely diagnosed.Were interested parties interested enough to provide report?

Except that there is no panic pull in AF447,

After autopilot disconnection the nose-up inputs produced a load factor of up to
1.6 g, that’s to say 1.4 g if the turbulence component is excluded. Maintaining a
high pitch attitude first resulted, when the aeroplane had sufficient speed, in a fast
climb speed (up to 7,000 ft/min) and then in a rapid increase in the angle of attack.

There are couple of videos with stick positions around, if someone finds graph-reading too strenuous.

As to your bit about manuals, you can't have it both ways.
Either is it "too complicated to explain" or it isn't. Make up your mind.That's not the way things work in the real world. Whether message is understood largely depends on receiving side too. Manual explains it very adequately for someone who will later go on and try it in aeroplane. Whoever tries to malign Airbus FCS without ever experiencing it must indulge in proclaiming the manual incomprehensible because its content do not support the claim that FBW really is dangerous per se.

As already said in a AF447 thread, I'm interested by degenerating dutch roll since 1979, and was creating only in 1992 a method to stop it with greater efficiency than just put hand off the stick and feet on the floor. I recovered with bank never more than 30°, lost less than 1000 Ft, in less than 30 seconds (MD83 Sim in Helsinki).
Before that, the other crew -6000 hours on type- lost 11000 Ft, understood nothing, flying right and left on the back, with overspeed, alarms and tutti quanti. The instructor -in flight instructor too- was not able to comment, and rejected the idea to ask me how I had done, himself had many thousands hours flying Learjet....
I never found an editor to publish my methodSorry to disappoint you, you can get no patent on this one. DP Davies was here before.

I would like to echo that comment. Until you have experienced a PIO/APC event, you cannot imagine the impact it can have on your ability to control the aircraft.And if you read about PIO in relevant publications, you can see that your interpretation of roll disturbances after AP threw the towel in as serious PIO are extreme exaggerations.

Interesting to note that the FAA places more emphasis on jet upset recovery than in the EASA and in Europe.
Because you say so or you have references?

Airbus does little training on recovery from unusual attitudes, re PIO, etc, in their Type Rating as well. Airbus does type ratings?!? Will I be asked again if I know something about airline ops?

Not sure if we all understand the "feel" of the roll/pitch commands in most FBW implementationsI am sure you all don't. See examples:

The best I can find is the majority of FBW jets command roll rate with yokes or sticks or sidesticks. Not bank angle, but roll rate.Every aeroplane commands roll rate with lateral yoke/stick displacement. Difference on FBW Airbi is that it is constant with displacement and independent of speed/config/loading.

The 'bus also stops you at certain bank angles if in the various laws above "direct"."Alternate", not "direct".

Airbus appears to be pure roll rate for lateral stick and the gee command is corrected for pitch with fore/aft stick( and you can't trim for roll rate or gee). Gee command in Airbus is also corrected for roll up to 33 deg bank.

You only get into trouble trying to deal with unusual roll rates ( and maybe some yaw back and forth). We saw that with the 'bus outta JFK when the tail came off and the KC-135 in one of the 'stans.Could you please explain how can one manage to find unusual roll rates in the accidents of AA587 and Reach 806? Before airframe failures, that is.

The Viper roll rate could be trimmed, as could the gee command for pitch.

Wonderful Viper's systems ! And, of course, pilots were trained to use these trims Airbus may Copy better and learn from our dear old fartsG trim is useful as one can trim it to 1 for patrol and 0 to achieve instant unloading during ACM by letting go of stick. Roll trim is nice to have when your external stores get asymmetric. Lack of these features will surely prevent Airbus 330 from ever getting accepted as an air superiority fighter.

[roulishollandais]

Clandestino
No patent wanted for safety !
It seems Learjet did not consider Davies had the solution to divergent dutch roll when they taught rapid pedal sharing , the lethal method used in AA587 against wake turbulence oscillations.
And airlines did never teach Davies' method, AF nor others. The AF447 crew did not seem to know it.

[Machinbird]

Quote:
Originally Posted by Machinbird
I would like to echo that comment. Until you have experienced a PIO/APC event, you cannot imagine the impact it can have on your ability to control the aircraft.

And if you read about PIO in relevant publications, you can see that your interpretation of roll disturbances after AP threw the towel in as serious PIO are extreme exaggerations.
Words of a gentleman who has obviously never experienced a PIO event.

[vilas]

Dutch roll on B707 has no similarity in Airbus. 707 was notorious for that and whatever little time I had on 707 I experienced it on a commercial flight, yaw damper failure kept causing vicious yaw and turn till I think the weight and altitude reduced to a certain level. I was trained for yaw damper failure in A310 simulator and it was nothing as compared to 707. Airbuses are not prone to this. So KC 135 comparison is futile.

[Lonewolf_50]

That's not the way things work in the real world. Whether message is understood largely depends on receiving side too. Manual explains it very adequately for someone who will later go on and try it in aeroplane.
In your own words (http://www.pprune.org/tech-log/539756-af-447-thread-no-12-a-61.html#post8859210).
It's the place in manuals where "needs to know" meets "unable to understand". Suggest you learn what a training audience is. Your cavalier assertion, underlined, is at odds with good training methodology. Caveat: if your assertion behind that line is that one or two of the three in that AF crew were unworthy of certification and unable learn this oh so complicate thing, but became regular crew at AF, that is another matter. Is that your position?

Your point on the dubious percentage of retention of whatever training was indeed received by the flight deck crew in AF 447 is not entirely masked by your failure in argument. As you noted previously, a significant number of other crews had similar problems and sorted things out.
If Aırbus wrote "maintains vertical flightpath" instead of "maintains 1G corrected for pitch up to 33 deg bank", already high number of confused manual readers would increase even more. In training, you first learn it in the book and other ground based instruction, then these days you seem to try it out in a sim, and then later you may experience it in an aircraft. Or you may not be permitted to try it out in the aircraft. Reasons for that vary. So why did Airbus made the system that is so difficult to describe? To make it simple to operate! Your logic failure is highlighted in bold. That cause and effect you assert is neither necessary nor sufficient. Making something simple to operate does not require it to be difficult to describe. Note: your assertion comes across that it is somehow necessary to make it too hard to understand. If that wasn't your intended meaning, then perhaps what you meant to say didn't come across.

Enough carping, thanks for the usual.

[Clandestino]

If that wasn't your intended meaning, then perhaps what you meant to say didn't come across.

True. Point I tried to make gently but unsuccessfully: intended public of manuals is pilots who fly or will fly Airbi and they do understand their FCS enough for everyday use and abnormals. Participants in anonymous fora and bloggers who complain about it have to demonstrate they don't, in order to make their unrealistic ideas look plausible. That's all there really is to it.

if your assertion behind that line is that one or two of the three in that AF crew were unworthy of certification and unable learn this oh so complicate thing, but became regular crew at AF, that is another matter. Is that your position? No. This is very crude (and unsurprising) falsification of my position.

AF crew was qualified and experienced on 330, thence they must have known something about their flight controls and apply it in practice to be let to play with their aeroplanes and then survive flying them. Issue is that at the crucial moment they forgot everything they learned not just about A330 but about basic aerodynamics and performance also and that's what killed them. BEA's report does not hide modern psychology's helplessness when faced with task to explain a pilot who suddenly tries to unreasonably go against the fundamental laws that keep him aloft, with inevitably tragic outcome.

[roulishollandais]

Dutch roll on B707 has no similarity in Airbus. 707 was notorious for that and whatever little time I had on 707 I experienced it on a commercial flight, yaw damper failure kept causing vicious yaw and turn till I think the weight and altitude reduced to a certain level. I was trained for yaw damper failure in A310 simulator and it was nothing as compared to 707. Airbuses are not prone to this. So KC 135 comparison is futile.Dutch roll is a normal oscillation regulated by yaw damper. Divergent dutch roll is another thing, one way among others toward PIO/APC on three axis, who have a great variety of causes and dynamic, often aggravated by unadapted pilot's response.
Learning from any of these accidents or incidents is never futile !
Switching the yaw damper to ON if OFF, or OFF if ON is far to be enough following a correct rapid diagnostic.
Pilots are mostly untrained to reduce or stop oscillations in their actual and always surprising form. A whole culture to understand unsteady dynamic is missing to pilots. Engineers building Y/D and Stability Augmentation systems who have that closed loop culture don't imagine all the cases of oscillations -rarely pure sinusoids- involving pilots by actions or only effects in flight in real and short time.
That must be improved and cooperation and communication between pilots and aeronautic and systems engineers enhanced and not limited to test flights. The solution is not replacing true test pilots and test flight engineers by airline pilots. Oscillations need to be studied by pilots in many forms.
Military are concerned as well as civilian pilots, both have their flight envelope limit where understanding a little more in the marge may switch life to death.
Of course it has a cost, not decreased by ultra-modern FBW or aging planes. But accidents have greater cost.

[Lonewolf_50]

True. Point I tried to make...Thank you for explaining what you meant.

Points raised on training, proficiency, and currency in the original threads I won't repeat here.

The "why" of the crew's decision and actions remains up in the air, unlike the aircraft and the souls who were traveling from Rio to Paris.

[DozyWannabe]

'Ullo, everybody...

Maybe they really should tell you something that you really might need to know like "Alternate Law" or as in the case of the Perpignan A320, "Direct Law."...

The Flight Control Law shouldn't really matter that much. In real terms, Alternate Law means "take extra care with your inputs, as it's now possible to stall your aircraft" and Direct Law means exactly the same with the addition of "...and you have to do the trim yourself". No matter what control law one is in, you should never deflect your stick to the stop unless you've got a damned good reason to do so.

All circumstantial except for one thing. Just why was AF447 oscillating in roll during those first 30 seconds?

http://home.comcast.net/~shademaker/AF447RollBehavior.png

Didn't we cover this a few months ago?

http://i1088.photobucket.com/albums/i331/turricaned/af447_fig64.png
It may be possible that the roll direct aspect of Alt2B might have thrown Bonin initially, but consider these points:

Bonin had *no* training or experience in high-altitude manual handling in Normal Law, let alone any of the Alternate configurations - how could he have known what to expect (put another way, how could he be 'thrown' or 'confused' by the control law change when he had no prior experience with which to compare it)?
Take a close look at the "Lateral Wind" graph alongside the pink trace on the "Roll Attitude" graph. At the moment Bonin took manual control, a 25kt right crosswind with an updraft component suddenly dropped sharply. The pink trace indicates that even with no input, the simulated aircraft actually rolls about 2 or 3 degrees to the left from inertia.
The right crosswind returns and averages around 30kts for the next 12 seconds, but at this point, Bonin's initial overcontrol to the left has him disorientated and making input reversals.

No matter what control law you are in, or even if you're in a type with traditional controls, I'd imagine that kind of initial quick reversal would be very tricky to damp out manually, and practically impossible if you've just been handed control from the AP with little warning. The return of a near-constant right crosswind for the next 12 seconds can only complicate matters further.

Better tell BAE they are wasting their time then.
...
"The biggest drawback of the “passive” sidesticks now used in civil aircraft is the lack of control feedback from the aircraft or the other pilot."
Of course, being sales literature, they don't enumerate the potential benefits (e.g. what happens when someone wires one side up backwards?)

PJ2 has the right of it here, and so (for the most part) does Clandestino.

[Uplinker]

Having flown a number of different piston, turbo props and jets in my time, I am a big fan of the Airbus FBW philosophy. It does not react as a conventional aircraft does, but I have personally adapted, and have no problems with that - I prefer it actually.

However, I think that where Airbus FBW IS deficient is that the side sticks are not mechanically or otherwise linked.

This causes problems with CRM and SA, and for example training cadets to flare and land. With ever other type I have flown, I have been able to "follow through" by softly holding the controls to learn what inputs the Trainer was making at each stage of the flare and landing. However, with the Airbus FBW, this is not possible. It is difficult to even see the side-stick on the other side of the cockpit, let alone assimilate what inputs are being made.

Those poor b@stards in AF 447 never really had the chance to realise what Bonin was doing, (and why the hell was he doing it anyway?), but with linked side sticks, they could have.

[TyroPicard]

Linked side sticks
S/S inputs are summed. PF moves his, if linked PM's moves as well, doubling the input.
To avoid doubling the demand, software is required to recognise when a sidestick is being moved by the pilot, and when it is being moved by the linking mechanism. Anyone fancy writing that, or explaining how they can be linked?

[Goldenrivett]

Anyone fancy writing that, or explaining how they can be linked?

Just a guess but how about something like:

When both Active Side Sticks move together, the inputs are summed and the controls move the normal amount (full & free).
If the override button is pressed, the side sticks become passive. The take over side's input is then doubled (full and free controls again) and the locked out side's input is ignored.

[TyroPicard]

Forget the override button... I will rephrase the question...

I move my sidestick. If the other one moves because they are linked, how will the FCS know it should ignore the input, yet not ignore the input when the other pilot moves that sidestick?

[Goldenrivett]

If the other one moves because they are linked, how will the FCS know it should ignore the input, yet not ignore the input when the other pilot moves that sidestick?
I will rephrase my answer.
The FCS doesn't ignore the input - it sums both active side sticks (which are moving together) it doesn't matter if the other pilot is moving the side stick or not.

[vilas]

We recently had an experience in A330 SIM when ADRS were blocked for unreliable speed pilot raised the pitch to deal with increasing airspeed. The aircraft went in deep stall and the nose dropped. The aircraft went in dive and could not be pulled out as the elevators had lost their effectiveness. it shook up the pilots but then we realised unless the data of that specific manoeuvre flight path is in the software the SIM behaviour cannot be taken as realistic of the aircraft flight path. So using SIM for AF447 type testing will be erroneous.

[Machinbird]

The Flight Control Law shouldn't really matter that much. In real terms, Alternate Law means "take extra care with your inputs, as it's now possible to stall your aircraft" and Direct Law means exactly the same with the addition of "...and you have to do the trim yourself". No matter what control law one is in, you should never deflect your stick to the stop unless you've got a damned good reason to do so.
Dozy, as you intimated, mostly the flight control law doesn't matter that much with respect to the way you make your control inputs.

When you start getting into Direct modes such as Alt 2B with Roll Direct, or into full Direct Law that assurance breaks down. If your attention is directed elsewhere (like outside the aircraft or at controlling a roll oscillation) you might well be setting off down a wrong path in controlling your aircraft.

In Bonin's case, he began flying with one set of roll gains expected and experienced a much higher roll gain with lessened damping than he was accustomed to. If the aircraft had the ability to enunciate: Alternate Law-Roll Direct, right at the A/P drop, that would have helped his situational awareness.

In the XL Airways A320 at Perpignan, that Captain needed to know that his aircraft had dropped to: Direct Law-Manual Trim in the initial stall, but he was looking out the window at a rapidly rising nose, holding the stick full forward and waiting for the automatic trim to lighten the load on the stick.

Maybe we need an automated Flight Engineer in the Airbus that you can talk to and which will inform us of changes to aircraft status by the verbal channel instead of the highly loaded visual channel. Might help in the Boeing as well.

There is no doubt that the Airbus human interface is eminently flyable, but it could probably be improved.

[DozyWannabe]

In Bonin's case, he began flying with one set of roll gains expected and experienced a much higher roll gain with lessened damping than he was accustomed to.
With respect, riddle me this; how do you expect Bonin to have a feel for what the "normal" roll gains are and therefore be thrown by the difference in Alt2B when it is on record that he had no training and likely little or no experience in manual handling at high altitude?

It's a logical certainty that one cannot be wrong-footed by a change in response when one has no experience of what the normal response is, surely?

[CONF iture]

RAF transport plane nose-dived 4,400ft leaving dozens injured | Daily Mail Online (http://www.dailymail.co.uk/news/article-3007690/Dozens-injured-RAF-transport-plane-nose-dived-4-400ft-27-seconds-Captain-took-photographs-left-Nikon-camera-joystick-stuck.html)
That's interesting ... Any official report somewhere ?

[A33Zab]

Investigation and final reports incident involving Voyager ZZ333 9 February 2014 (https://www.gov.uk/government/publications/service-inquiry-incident-involving-voyager-zz333-on-9-february-2014)

[Machinbird]

riddle me this; how do you expect Bonin to have a feel for what the "normal" roll gains are and therefore be thrown by the difference in Alt2B when it is on record that he had no training and likely little or no experience in manual handling at high altitude?Dozy, very simple. He was expecting a Normal Law type roll response. What he received was very different and much more vigorous. The scanty information I've seen on his training indicated that he had never flown in Alternate law at altitude. That does not exclude flying in Normal law at altitude. I would also expect Normal law at altitude to fly about the same as Normal law at lower altitudes due to the intervening computer magic.

Bonin began flying when the autopilot dropped, before he knew the nature of the causal malfunctions and their implications.

[DozyWannabe]

Dozy, very simple. He was expecting a Normal Law type roll response.
How could he have been expecting a Normal Law roll response when he had no experience of what that response was?

The scanty information I've seen on his training indicated that he had never flown in Alternate law at altitude
What I've read suggests that he had no training or experience whatsoever on high altitude handling in any flight law.

[Mr Optimistic]

Has the replacement pitot programme completed yet? Were there any other changes, eg to the stall warning logic?

[Machinbird]

How could he have been expecting a Normal Law roll response when he had no experience of what that response was?
Dozy, you are making this more complicated than it is supposed to be. In Normal law, Full lateral stick is supposed to deliver 15 degrees/second roll rate, period. See FCOM. The computer magic makes it seem to roll the same everywhere, even though you are up at altitude. The roll damping even seems to be the same. When you neutralize the controls the roll rate stops the same way up high and down low.
When you are in a roll direct law, Your control deflection is proportional to stick deflection. When you neutralize the stick, the aircraft roll momentum keeps it rolling dependent upon its roll rate damping factor and you actually have to make a counter roll input to stop it. That is a big difference, but if you have flown that type system before, the adjustment is quick.
(From FCOM)
LATERAL NORMAL LAW
When the aircraft is on the ground (in "on ground" mode), the sidestick commands the aileron and roll spoiler surface deflection. The amount of control surface deflection that results from a given amount of sidestick deflection depends upon aircraft speed. The pedals control rudder deflection through a direct mechanical linkage.
When the aircraft is in the "in flight" mode, normal law combines control of the ailerons, spoilers (except N° 1 spoilers), and rudder (for turn coordination) in the sidestick. While the system thereby gives the pilot control of the roll and heading, it also limits the roll rate and bank angle, coordinates the turns, and damps the dutch roll.
The roll rate requested by the pilot during flight is proportional to the sidestick deflection, with a maximum rate of 15° per second when the sidestick is at the stop.
When the aircraft is in "flare" mode, the lateral control is the same as in "in flight" mode.This is not to say that making a turn at altitude is identical to making a turn down low. At altitude, you are going much faster and Mach effects reduce the available AOA. You also have less reserve thrust available. The result is that turns at altitude are less aggressive than turns down low. You have to use lesser bank angles at altitude if you are going to avoid the stall boundary and maintain airspeed.

[DozyWannabe]

This is not to say that making a turn at altitude is identical to making a turn down low. At altitude, you are going much faster and Mach effects reduce the available AOA. ... You have to use lesser bank angles at altitude if you are going to avoid the stall boundary and maintain airspeed.

Which is kind of the point I was trying to make. Far from making things more complicated, I think my position is fairly simple - namely that the lack of training or experience in high-altitude manual handling *in any law* had a far greater impact on Bonin's ability to control the aircraft than the difference in roll response in Alt2B vs. Normal Law.

Fundamentally, whether you're getting 15 degrees/sec roll rate, or whatever you get when stick input commands deflection, the point is that the aircraft must be handled differently at altitude than it does closer to the ground. Bonin's inputs in roll were excessive from the get-go, and I think the control law would have made little difference in how he perceived the aircraft's reaction.

[vilas]

Lack of high level handling is the common feature in commercial flying for all aircrafts. Actually non FBW are more tricky to handle as they are very sensitive at altitudes. FBW aircrafts high altitude handling does not differ in pitch in normal and alternate law. In alternate roll is conventional but when aircraft holding the flight path it becomes easier. The point is roll or rate of roll was not the cause. The aircraft was pitched up and held there otherwise there is sufficient margin from VSW even at FL350 for the rock n roll.

[Machinbird]

The point is roll or rate of roll was not the cause. The aircraft was pitched up and held there otherwise there is sufficient margin from VSW even at FL350 for the rock n roll. Vilas,
What you say is absolutely correct as to the overt behavior of the aircraft and apparent reason for the AF447 pitch up. As you probably know, some of us have been looking at roll PIO as a possible causative human factor in the otherwise inexplicable piloting failure that caused the AF447 accident.

Very few airline pilots have ever experienced any form of PIO event, and the mental effects on a pilot trying to fly during such an event are definitely under-appreciated.

Anyone wishing to expand their knowledge of PIO (also known as APC) would do well to obtain a copy of Aviation Safety and Pilot Control: Understanding and Preventing Unfavorable Pilot-Vehicle Interactions by Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety |The concepts are understandable without having to be proficient with the associated mathematics.:ok:

[john_tullamarine]

Following on from Machinbird's post, the paper is available for complimentary download from the NAP website (http://www.nap.edu/openbook.php?record_id=5469).

[roulishollandais]

only the regulator can ensure basic flying experience levels rise. In France at least it was the regulator who decreased the basic flying level since 1979 and deregulation - it is the true and official name of that movement- didn't work for low cost airlines first but for Air France competitors to destroy the SNPL power... These airlines at the beginning were not low cost in the today's sense but they only decreased the bill cost by flying only the trips where Air France and Air Inter were full of passengers (Paris-Antilles, Paris-Nice, Paris-Toulouse, aso) or low level fuel price trips (Marc Rochet).

The decreasing level of formation started with A320, remember the strikes of AEROFORMATION FTEs unhappy to have no more enough time for basic and classical flights, they had to use the time to teach B.A.BA of FBW button pushing.

Low cost airlines could only emerge in France when it was no more mandatory that a French airline used a French registered plane, and leasing helped to share benefits in one hand, financial risk in another... and fisc didn't see the loss of money and corrupted people organised financial worldwide Mafia hidden behind the ICAO flag.

[vilas]

Again and again inexperience in cockpit comes under scrutiny while in many accidents experienced pilots were handling the plane. A fat logbook is not a safety barrier and does not compensate for lack of required skill. 5000 command hrs. on a medium range automated aircraft like A320 simply translates into 2 1/2 thousand times switching the AP ON and OFF for landing. We have to understand that in aviation it is not be possible to learn everything in air by personal experience and practice. High altitude handling, practicing alternate/direct law is not possible. Pilots are retiring without having experienced an engine failure. That doesn't mean one should be unable to handle it. Some theoretical understanding and simulator practice is the only answer. Type rating needs to be expanded more at least for the beginner. Airbus has expanded the type rating for the beginners by eight sessions of handling as entry level training/MCC course in fixed base trainer but airlines have got around this by adapting a mini version in a procedure trainer which defeats its purpose. Accident due to the inability of an experienced pilot to do a visual approach shows that those thousands of hours was merely a delay in aligning of the Swiss cheese. The required skill was never acquired. Understanding the behaviour of the aircraft like Airbus FBW where there is never a requirement of knee jerk reflex on the side stick can win half the battle for you. Perhaps with declining profit margins airlines have become like other businesses, more of a commercial strategy than anything else.

[VNAV PATH]

For those having nostalgy of good regulatory overview, good experienced pilots and good leather cabin seats: 67 ft RA over outer marker.


http://www.bea.aero/docspa/1997/f-mc971123a/pdf/f-mc971123a.pdf

[DozyWannabe]

...FBW button pushing...
You'd sound more credible if you'd get the terminology right - "button pushing" is a feature of autoflight, *not* FBW. FBW and automation are categorically not the same thing.

[roulishollandais]

Point for you !
Edit add :
These students did not know the difference between automation and systems : They did not read that wonderful book cited by Machinbird and John Tullamarine : one of the best (or best !) Book to read to understand dynamic systems and feedback in aircraft's a control and design.
Unless you understand that everything is pushing button !

[roulishollandais]

VNAV PATH,
terrifying drift in crew management during that "autoland", and teaching in flight !
That captain thought he was a god and he was building followers not pilots.
No amazement from AOM/Air Lib ! The good cabin leather cabin seats with caviar were their best performance...

[NeoFit]

AB anyone ?

I agree with this very interesting post (http://www.pprune.org/rumours-news/553569-air-asia-indonesia-lost-contact-surabaya-singapore-167.html#post9000956)

Here (http://imgur.com/m1LytPD) is evidence of rudder efficiency

[DozyWannabe]

@NeoFit - As Machinbird points out, that post is not entirely correct. The PIO began long before the aircraft entered into the stall regime, and the YD was doing its best to correct for it.

[Winnerhofer]

Appeal Court invalidates Airbus' Counter-Report.
Crash du Rio-Paris : la justice annule un rapport d?experts défavorable aux pilotes d?Air France, Tourisme - Transport (http://www.lesechos.fr/industrie-services/tourisme-transport/021485988820-crash-du-rio-paris-la-justice-annule-un-rapport-dexperts-defavorable-aux-pilotes-dair-france-1175992.php)
https://www.francebleu.fr/infos/faits-divers-justice/crash-rio-paris-une-contre-expertise-annulee-le-dossier-relance-1447764309
http://www.mediapart.fr/files/AF447_Contrex_1_0.pdf
http://www.mediapart.fr/files/AF447_Contrex_2_0.pdf

[Winnerhofer]

A new book by an AF Captain with many years blames Airbus' Neutral Stability as totally counter-intuitive.

He quotes page 193 of BEA report which says that Airbus' Neutral Stability should have NEVER been certified as it is contrary to the most basic of aviation tenents.

Lorsque plus aucune protection n’existe, l’avion ne possède pas de stabilité statique longitudinale positive même à l’approche du décrochage.
Cette absence se traduit en particulier par le fait qu’il n’est pas nécessaire d’avoir ou d’augmenter une action à cabrer pour compenser une perte de vitesse en maintenant l’avion en palier.
Ce comportement, à basse vitesse, même s’il peut paraître contraire à certaines prescriptions du règlement de base, a été jugé acceptable par les autorités de certification par prise en compte de conditions spéciales et interprétations particulières ; en effet, la présence de protections d’enveloppe de vol rend tout à fait acceptable une stabilité statique longitudinale neutre.
Pourtant, la stabilité statique longitudinale positive d’un avion peut s’avérer utile car elle permet au pilote d’avoir un retour sensoriel (via la position du manche) sur la situation de son avion en terme de vitesse par rapport à son point d’équilibre (trim) à poussée constante.
En particulier, l’approche d’un décrochage sur un avion classique est toujours associée à un effort à cabrer de plus en plus prononcé.
Ce n’est pas le cas sur l’A330 en loi alternate.
Il en résulte notamment que dans cette loi de pilotage l’avion, mis dans une configuration où la poussée n’est pas suffisante pour maintenir la vitesse sur la trajectoire, finirait par décrocher sans action sur le manche.
Il apparaît que cette absence de stabilité statique positive a pu contribuer à l’absence d’identification par le PF de l’approche du décrochage.

Page 186 (English)
When there are no protections left, the aeroplane no longer possesses positive longitudinal static stability even on approach to stall.
This absence specifically results in the fact that it is not necessary to make or increase a nose-up input to compensate for a loss of speed while maintaining aeroplane altitude.
This behaviour, even if it may appear contrary to some provisions in the basic regulations, was judged to be acceptable by the certification authorities by taking into account special conditions and interpretation material.
Indeed, the presence of flight envelope protections makes neutral longitudinal static stability acceptable.
However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust.
Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input.
This is not the case on the A330 in alternate law.
The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick.
It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall.
============================================================ ========================================
By A Special Contributor:
He's technically correct but that's why Airbus tells pilots, in nice big bold letters, that you have reduced protections in those modes.
I'm not sure why this is an AF447 comment...if the pilot had left the stick alone, neutral stability would have saved his butt.
It was pulling nose up that really got them in trouble, and would have on an airplane with positive or neutral stability.

[A-FLOOR]

He's technically correct but that's why Airbus tells pilots, in nice big bold letters, that you have reduced protections in those modes.
I'm not sure why this is an AF447 comment...if the pilot had left the stick alone, neutral stability would have saved his butt.
It was pulling nose up that really got them in trouble, and would have on an airplane with positive or neutral stability. The assumption that simply letting go of the stick would have saved them does not appear to hold up to scrutiny. I found this particular gem by OK465 in the A320 OEB thread from one year ago:


All we're saying is that once this energy decay situation is established, there is no need to hold the SS aft, for the sequence to play out. Hands-off will do the trick BECAUSE of the FCS flight path stability attempt.

In ALT, from 265 or so KIAS, manually fly your A330 level D simulator to a 10 degree flight path angle at 35,000', at TOGA power if you like, and then take your hands off the SS. Watch the THS trim and sit back and enjoy (:eek:) the ride, remain totally hands off at this point. (Monitor the FPV and SD Flight Control page for additional information.)

The THS will reach 13 ANU and AOA will reach 40+ hands-off. If you have the simulator Input Guidance capability selection at the instructor station, you can monitor AOA through-out on the VOR DME readout.I'm afraid I do not have an A330 sim at my disposal to replicate his finding, but the way he describes it is exactly the way I would test this myself.

The behavior he witnessed however should not be called neutral stability. It is the definition of negative stability! The fact that the aircraft keeps trimming up silently well past the stall warning is extremely worrying.

[Winnerhofer]

Aftermath: It Just Doesn't Compute | Flying Magazine (http://www.flyingmag.com/aftermath-it-just-doesnt-compute)
https://disqus.com/by/disqus_hkf2Up0sbq/

[Winnerhofer]

Video - Ejectable floating black boxes - Aviation industry - Aeronewstv (http://www.aeronewstv.com/en/industry/research-innovation/3404-airbus-ejectable-black-boxes-interview-of-charles-champion.html)

[Winnerhofer]

From A Safe Pair Of Hands:
I have backed off from these discussions as I feel I am too much out of date.
I retired 18 years ago as a B743 Captain after a long career, 43 years, in all sorts of roles: Navy pilot, then Exec of Squadron, followed by an airline career piloting Viscounts, DC9s, F27,B727s, A300, in roles usually as a check airman or Flight Superintendent Training before management for five years.
As an old timer, I was very sceptical of FBW new aircraft coming in.
I felt there was not enough redundancy, e.g., an old control tab until converting pilots got the full experience.
My view was that converting pilots were to be hanging in there by their fingertips for quite some time, scared of their careers coming to an end in midstream and actually without a full understanding of the complexity of the equipment.
Manufacturers' salesmen had convinced management that the aircraft were safe, "Could not crash" and no need for so much training.
Kids were learning to fly in simulators, not all of good quality, and getting Airline jobs without 'Airmanship'.
I was pleased to see revival of common sense with the American Airlines video, "Children of the Magenta".

[RetiredF4]

Years after ..........., at last.

Understanding The Angle-Of-Attack Indicator | Business Aviation content from Aviation Week (http://aviationweek.com/business-aviation/understanding-angle-attack-indicator)

When I and others raised this topic on the various AF447 threads, we earned only rolling eyes...

[vapilot2004]

If only the gents on AF447 had such an instrument at their disposal...

[DozyWannabe]

When I and others raised this topic on the various AF447 threads, we earned only rolling eyes...
With respect, I remember it a bit differently. I think the consensus was that in theory it's a good idea, however in the case of this particular accident the crew missed so many cues from the instruments they did have that having an AoA indicator on top of those likely wouldn't have made much difference.

[Goldenrivett]

the crew missed so many cues from the instruments they did have that having an AoA indicator on top of those likely wouldn't have made much difference.

The crew were certainly very confused but I believe the Captain would have recognised that they were stalled if the aircraft had this new FWC installed.

"STALL WARNING enhancement: Stall warning will work when:
Undetected erroneous computation of pitot
Pitot out of the airflow
Pitot obstructed by ice or any foreign material at any speed (function now possible below 60 kts)"

@ DozyWannabe. I seem to remember that you argued the AoA probes would be unreliable if the IAS indicated less than 60 kts despite being airborne.

[DozyWannabe]

@ DozyWannabe. I seem to remember that you argued the AoA probes would be unreliable if the IAS indicated less than 60 kts despite being airborne.
Well, I'd imagine they'd be reliable if the vertical airflow in a stall situation was > 60kts, but on the other hand that's a situation that no-one in their right mind would want to be in!

[CONF iture]

With respect, I remember it a bit differently. I think the consensus was that in theory it's a good idea, however in the case of this particular accident the crew missed so many cues from the instruments they did have that having an AoA indicator on top of those likely wouldn't have made much difference.
It is too easy to crucify the crew for "missing so many cues"
Instruments were providing confusing informations for the 3 min the airplane was fully stalled.
A simple AoA indicator would have told the true story with consistency from the highest point to sea level. Maybe just what was missing to both copilots and the returning captain to properly analyse the situation ...

[galaxy flyer]

What's so confusing--nose above the horizon, altitude decreasing at a vicious rate means huge AOA problem. An AOA indicator, based on present training syllabi, wouldn't have helped them as they missed the huge clues, why would they have figured with one rather subtle clue?

[vilas]

There is nothing left to milk the thread except perhaps having one last parting shot. Most have left. Those who are still there nothing will change for them.

[safetypee]

vilas, ' nothing more to milk'; depends what you look for, what you have learnt or are prepared to learn.
Any 'new' aspects may be far removed from the previous discussion on what happened or AoA displays.

However, there is one related aspect of AoA which the regulators / manufacturers may be considering.
Most commercial aircraft use AoA for stall warning and identification; a key area is where these functions are not available. Conventional warning and identification is not required in envelope 'protected' aircraft, but with the unavailability of that protection, the alternative warnings / alerts may not be as good as standard systems, e.g. stick shake / stick push are more effective than a voice call.
Whilst any of these systems might not be available during some extreme speed excursions, they are normally available during the approach to and transition from safe flight to an upset, i.e. the avoidance - preventative functions still work.

The particular issues in this accident were the 'immediate loss of protection', voice stall warning, and no equivalent stick push. These were compounded by trim interaction.
Safety solutions may consider retaining the protections longer during a malfunction, and/or strengthening alternative alerting; enhancements to speed awareness are already in place.

All of the above are preventative, - avoidance; whereas the recent suggestions to use pure AoA displays are reactive.
The reactive approach requires good situation awareness and recognition so that an appropriate course of action can be considered - use AoA display. Unfortunately, as in this accident, if crews have insufficient awareness or understanding to appreciate an audio stall alert or consider attitude to effect a recovery, then a new AoA display may not be any more effective.
Look for the assumptions in change proposals. Also see surprise and cognitive workload as discussed in Emirates 777 thread.

As for other lessons, look further afield. Every day CRM for storm avoidance, UAS checklist and training, methods of simulation, and as to why additional refresher training was required at all; what was the alternative.

[CONF iture]

What's so confusing--
Yes, confusing informations :

Nose was also 10 deg below horizon
V/S showed also zero
And of course when "the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning triggered again."

It is simplistic to state "they missed huge clues" but you was not there.
If an AoA indicator had indicated they were all the time above 35 deg, I would not call that a "subtle" indication, especially for the returning captain.

[Chris Scott]

Whether jet-transport pilots should have an AoA indicator or not - and I must admit I'm inclined to think that they should, even if it is only to be used as a last resort for stall diagnosis in the event of loss-of-control following UAS - the issue remains of the perceived validity of AoA indications when the IAS is genuinely lower than that needed for sustained flight.

When the AD design team for Airbus FBW at Saint Martin-du-Touch (?) decided in the mid-1980s to opt for invalidating AoA data at IAS < 60 kt (assuming my memory serves), were they:
(1) just playing safe, i.a.w. normal engineering practice;
and/or
(2) influenced by the assumption that such an airspeed would only be indicated when the a/c was on the ground, and the vanes on either side of the fuselage would therefore be susceptible to crosswind and shielding effects (for want of a better description).

In any case, the possibility of a large jet transport achieving a genuine IAS of less than 60 kt when airborne, even with the grossest mishandling, seems too remote to merit consideration. However, one would have to consider the reliability of the AoA vanes in conditions that had already caused UAS due to freezing of pitot-head(s).

[Owain Glyndwr]

When the AD design team for Airbus FBW at Saint Martin-du-Touch (?) decided in the mid-1980s to opt for invalidating AoA data at IAS < 60 kt (assuming my memory serves), were they:
(1) just playing safe, i.a.w. normal engineering practice;
and/or
(2) influenced by the assumption that such an airspeed would only be indicated when the a/c was on the ground, and the vanes on either side of the fuselage would therefore be susceptible to crosswind and shielding effects (for want of a better description).

or
(3) abiding by the vane manufacturer's DDP which gave the limits on output validity for the vanes?

[vilas]

Only thing I don't understand is how AOA display will prevent bizarre application of flight controls which created the need for all that? AF447 didn't have speed but five and half years later after learning everything about it in QZ8501 despite having everything the initial action that started the disaster and continued to the crash was exactly same. With introduction of BUSS you can survive without speed below FL250 provided you don't do something above 250 that makes BUSS irrelevant.

[Chris Scott]

Quote from Owain Glyndwr:
"or
(3) abiding by the vane manufacturer's DDP which gave the limits on output validity for the vanes?"

Thank goodness for the presence of an engineer to remind one of the obvious! In which case, perhaps the vane manufacturer might be politely asked to reconsider the DDP and/or review the design?

Hi vilas,
I entirely share your reservations about the chances of the AF 447 crew having benefited from an AoA indication that morning. The actions of the PF in making or allowing the a/c to climb from a stable cruise regime were so bizarre that the inclusion of another parameter to those currently available to him is perhaps unlikely to have improved his situational awareness. There remains a slight possibility, however, that the presence of an AoA gauge might have informed the captain of the deep-stall regime that was in force when he entered the cockpit during the descent. Whether there was sufficient altitude to effect a recovery at that stage, given the application of immediate and correct action, has been the subject of some speculation previously.

CONF_iture reminds us of the anomaly by which the stall warning is inhibited when the AD detects an IAS below 60 kt, which may or may not be false. That is something that needs to be addressed.

Another problem is that, on any type of a/c, the trouble with aural/tactile stall warnings is that they remain at the same intensity regardless of how much the stall AoA has been exceeded. I'm wondering if the sudden appearance of an AoA indicator showing clearly how much the AoA is above the stall might be useful.

In the case of AF 447, there would have been periods of stall warning activity where such an AoA gauge could have shown the crew that the stall AoA had already been exceeded by a very large amount. This MIGHT have finally alerted one of the pilots to the developing situation. Whether that would have resulted in his taking the correct recovery action is, of course, another matter.

[vilas]

When looking for possible improvements of the equipment we should look to future and not bring in AF447 because how an insufficiently trained crew would have used that enhancement is impossible to guess.

[gums]

With all respect, Vilas, training has almost certainly improved since AF447 data was revealed.

Instrumentation might also have been improved, but the basic cause of the crash was aircrew error. Control inputs were a factor. Stall recognition was a factor. The 'bus FBW degredation modes were a factor. It was a perfect storm.

The AvWeek thread about AoA is a lot less thoughtful than here.

I was and still am convinced that some AoA indication could have helped AF447 even if the sucker had a red flag saying it was unreliable. The jet did not instantly go into a deeply stalled condition, and apparently the AoA sensors were valid until the jet got very slow or the AoA was far in excess of what was designed.

As most here know, ya gotta use all the indicators and sensors you have available.

As one of the AvWeek references makes some good points about speed and AoA, I am here to add to his examples. I had a rainy night landing in my A-7D and once the flap handle was down and the speed versus AoA looked good I followed the AoA bracket and the indexers ( we had the Navy-style HUD). Bad news was that the flap handle had a "beep" function once "around the horn". So you could stop full deployment of the trailing edge flaps. Dunno why, but that night I inadvertantly bumped the handle and my trailing edge flaps were about half or less than desired. The AoA bracket looked good, and the leading edge flaps had deployed per the book. I was going maybe 15 or so knots too fast!!!

I had anti-skid cycling and finally lowered the hook to take the cable at far end of the runway. Lesson learned!!! Cross check all the gauges and there's no serious penalty for a "bolter" whether on a boat or a 9,000 foot runway.

I later flew the first fully FBW jet as most here know. Our AoA display was only there with the gear handle down, although the flight control computers used multiple AoA sensors to keep the pointy end forward all the time.

I really like the AoA for approaches once cross checking with estimate of speed for weight and such. My Sluf barrier exercise made that a rigid entry on the mental check list.

I like the idea of an aural warning of the AoA, but seems the 'bus has a lotta aural stuff already, ya think?

[vapilot2004]

Originally Posted by Jimmy Hoffa Rocks
Interesting to note that the FAA places more emphasis on jet upset recovery than in the EASA and in Europe.

Because you say so or you have references?


The FAA mandated upset recovery training in 2010. EASA decided to expand their requirement in May 2015. Article linked below accessible for subscribers describes the recent stall requirement differences between the two regulators.

EASA Opposes Full Stall Simulator Training Upset Training - Aviation Week (http://aviationweek.com/commercial-aviation/easa-opposes-full-stall-simulator-training-upset-training)

Discussed to some degree here. (http://www.pprune.org/tech-log/583792-737-stall-training-alaska-airlines-sim.html)

For those interested in implementation standards and practices:
IATA - Guidance Material and Best Practices for
the Implementation of Upset Prevention
and Recovery Training (https://www.iata.org/whatwedo/ops-infra/training-licensing/Documents/gmbp_uprt_2015.06.23.pdf)

[RetiredF4]

@all

nice to see you guys back, I actually missed you all!
And nothing has changed concerning the individual assesment concerning AOA!

Keep happy!

[galaxy flyer]

Ah yes, flame out the tail, he's in burner; flames out both ends, he has suddenly became very predictable and a target.

Yes, the G6000 with Collins has a small AOA gauge on the PFD, I use it but most guys wouldn't know much about it as the AFM gives zero guidance on recommended AOA readings for specific regimes. I watched the AOA on the C-5 like a hawk in the pattern or when in any unexpected situation, say holding for the tanker at max formatting altitude. I was Board President for the Diego Garcia crew.

Rapidly unwinding altimeter, without a corresponding nose position should be a big clue. Regarding the 60 knot stall warning cut-out, I believe that is pretty common, it is in all Bombardier planes.

OK465

Did you post something on the reaction if an Airbus put into a steepish climb, watch the THS roll nose up and see how it reacts in the sim?

[safetypee]

Without knowing the crew's thoughts, it's almost impossible to understand why the crew acted as they did; any other view is supposition.
However, generic answers might be identified by taking a wider view. We normally act as we see a situation, where perception is an amalgamation of sensed information and that stored in memory. Thus actions can be influenced by how something is sensed and what we have experienced before; this is the basis of training, - how to influence behaviour for future activity.

Thus we might improve our understanding of accidents by identifying potential contributory factors.There is no certainty that these were influential in this accident, but by considering possible effects, then other events might be avoidable.
In this accident. What was simulated, how; how checklists are formed and used, and threat knowledge.

Did UAS simulation just remove the airspeed display; or were all the effects of an ADC system malfunction on other systems accurately represented - the surprise factor - no simple clue to the problem.

Did the checklist have a condition statement before memory items; 'if an emergency then memory items', if not, read the followup actions. An 'emergency' is subjective according to experience.
If the checklist was drafted to differentiate the dynamics of a situation - takeoff, climb, descent, cruise, then the cruise condition would not require memory action, only the followup items. Had that aspect been trained, was the training related to the real threat (ICI), did the crew, simulator, operator know.

Did operational procedures require the Captain (P1) to handle the aircraft in an emergency; thus the basis of the PM's experience was only by reading the check list. Were the followup items considered; shortage of simulator time, handling more important than reading lists. Would a PM gain sufficient experience to qualify as a relief PF, enabling judgement of an emergency, and in handling the aircraft with abnormal feel.

It is difficult to answer these questions based on what has been reported about this accident, but we can look at current activities to learn about what happens now, and perhaps avoid similar incidents.
It is also essential to continue questioning, to consider any other influencing factors.
Why require refresher training for UAS; the threat was ice crystals. It would be more logical to train avoidance of CBs - ICI, radar handling, calculating larger miss distances, threat knowledge; opposed to reactive actions for UAS, which should have already been trained in basic training.

None of this requires AoA; except a gauge of how we think about accidents.

[vilas]

I was surprised to read in airbus Safety First December 2007 issue a detailed discussion about Unreliable Speed, exactly one and half years before AF447. It included Effects and consequences in the cockpit, Identification and handling of UAR situations, Procedures and BUSS. It didn't seem to have caught anybody's fancy. The crew that night was simply ambushed. It is amply clear that they didn't have the knowledge or training to identify what was happening and apply appropriate procedure. UAR is very serious situation to identify and correct and in my opinion something that was not going to happen by accident. In a habitat that is not human confronted with a situation you feel inadequate can trigger extreme fear leading to hyperventilation which can wipe any semblance of rational thought. What difference another instrument would have made is impossible to predict. Airbus did give a thought to AOA indicator but didn't consider favourably. In a conference in 2010 airbus had stated the following:



Even if the AOA is the key parameter, we do not intend to equip our aircraft with AOA indicator for 2 reasons: first this would require a specific training, and second the stall AOA varies from low to high Mach number so that it is not a constant value.

[Uplinker]

AF 447
This was done to me recently in the SIM. I did not know what was coming or what to expect. I probably should not admit to it, since it reveals several mistakes on my part, but for the greater good, here we go.

It was night time. There were no clouds or any weather visible from the cockpit. There was no moon or stars or horizon. The Captain actually got out of his seat; saying he was "going to the loo". After he had gone, I was given a climb from FL350 to FL370. I initially declined the climb, since REC MAX on the PROG page was only showing FL370, however, they insisted, so for the purpose of whatever it was they wanted to demonstrate, I complied. As the aircraft climbed, the airspeed very slowly increased. I thought odd - perhaps an Auto-thrust or speed control fault? Both speed tapes were showing exactly the same thing however, I thought odder still.

I was starting to think about unreliable speed when the over-speed warning went off. I tried to ignore the warning and work out what was happening. Both speed tapes were still identical and steady. The Airbus overspeed warning is extremely loud, extremely insistent, and does not stop (and I forgot how to cancel it). After a few moments of apparently being in overspeed, and the very loud, very insistent warning going, I deployed the speed brakes to no avail. I then pulled the thrust levers to idle. Soon after that, the nose dipped. I thought ah, now I know what they are doing to me; Abnormal V alpha prot. So I followed the OEB for V alpha prot and turned off two ADRs.

This did not help and they froze the SIM with a V/S of -14,000'/min showing.

Now, you are probably all way ahead of me here, but there I was holding full back stick and descending at 14,000 a minute and not understanding what was going on. Sound familiar?

Once they explained what had happened, they released the SIM, and I pitched forward to unstall the wing, added power and safely levelled off.

I was very shaken by this demonstration, in particular how I had ended up holding full back stick having stalled the aircraft.

Several points and recommendations:

1. I did not recognise unreliable speed, or the fact that both the Captain's and F/O's pitots had frozen up simultaneously during the climb. I did not follow the unreliable speed drill.

2. I did not recognise that the aircraft had stalled. This was in the SIM, and there was no airframe vibration or reduction in external wind noise to give clues about reducing airspeed. Nevertheless, I did not recognise the stall, despite the sudden nose drop.

2a. When they froze the SIM so we could see what was going on, I agreed with their diagnosis but said, 'but the audible "stall stall" did not go off'. They said "yes it did". So it was sounding but I literally did not hear the audio saying "stall stall".

3. I, like many at the time of AF447, said that I would never be stupid enough to hold full back stick. But that is exactly what I did - thinking I had a V alpha prot problem.

4. Unreliable speed does not necessarily manifest itself as one wildly fluctuating or stuck speed tape while the other one moves normally - which was the only demonstration of unreliable speed that I had previously been shown.

5. The over-speed alarm is far too strident. It blocks the brain, preventing sensible thought. It should not be a continuous repetitive chime. Overspeed of a few knots is not going to kill anyone, or even damage the plane actually.

6. If the aircraft stalls, there needs to be haptic (vibrating) feedback from the side-stick, like a stick shaker, and all other audio needs to be suppressed except just the "stall stall".

~ According to human factors research, our hearing is the first sense to shut down when we become overloaded. So there needs to be a physical vibrating feedback to alert the pilot, and the amount of audio alerting needs to be kept to a minimum - only the most important thing at any point should sound.

7. It is high time and extremely important that a method of measuring airspeed is urgently developed that is not susceptible to interference or incorrect reading under icing conditions.


I made mistakes during this SIM demonstration and missed cues and clues that I probably should not have missed. But in my defence, I have never seen them in the form they were presented to me. It is one thing to read about failures in a book, but one should really experience the most safety threatening failures. I am not proud about this but I am hopefully a better pilot now. In future, if anything on the PFD ever looks unusual, (or even impossible !), I will take out the autopilot and the auto-thrust and set 2.5 degrees up and around 83% N1 (in the cruise). This will keep us safe and flying normally while we work out what has gone wrong.

I take back anything I might have said about the crew of AF 447.

[CONF iture]

Vert interesting Uplinker, and thank you for sharing.

Even if the AOA is the key parameter, we do not intend to equip our aircraft with AOA indicator for 2 reasons: first this would require a specific training, and second the stall AOA varies from low to high Mach number so that it is not a constant value.
1- They still provide some aircrafts with the BUSS that should also require a specific training ...
2- Whatever the Mach, at 30deg of AoA, you're stalled, Top Priority is to urgently reduce it !

[galaxy flyer]

Very enlightening to someone not on the 'Bus. I have a much better understanding of what might have happened that night now and you have removed my prejudices of the plane and crew.

[gums]

TNX, Link.

I, too, can cut some slack WRT the crew, and seems I gave them a just a tad back when we were in the height of our analysis here and found out about all the aural warnings.

I will still support my belief that a HUD would have helped as much as AoA indication. Most have some type of aircraft reference line symbol and the difference between it and the flight path marker is your "overall" AoA, right? So AF447 crew would have seen the FPM caged at the bottom of the HUD, indicating an extrmely high AoA plus the precipitous descent even with the nose pointing above the horizon.

All this available WITHOUT air data!!! All inertial. And seems like many HUD scales have an instantaneous vertical velocity option in addition to the baro VV.

All that being said, some training is required to fully exploit the display(s), though I transitioned in a minute or so when first checking out in the A-7D with the Marconi HUD.

Finally, I wholeheartedly agree with "link" about tactile feedback. In the fighter community there can be a lotta audio from systems and other pilots/control agencies. And we fly looking outside a lot more than the commercial folks. I flew two jets with pitch "limiters" - neither vibrated or anything. At max AoA the flight control system just kept you from pulling more, and the Viper stick moved too little to tell max input and was a force input, not angle/position-related. The A-7D had no limiter, but the rudder pedal(s) vibrated enuf to warn you of impending loss of control.

And good to see so many familiar folks - what a wealth of experience and knowledge here.

[RetiredF4]

@uplinker

Very interesting expierience, thank you for sharing it!

And fully agree, reading of FCOM does not make a pilot, and reading up on emergency procedures does not prevent from acting differently in real live.
Fly safe.

[vilas]

reading of FCOM does not make a pilot, and reading up on emergency procedures does not prevent from acting differently in real live Sure! That is why you need to do something more. But I also definitely know ignorance of FCOM did not help pilots of EK521 either, the recent Dubai 3rd August. One needs what they call KSA. Knowledge, Skill, Attitude.
I was starting to think about unreliable speed when the over-speed warning went off.If so then why on earthI deployed the speed brakes to no avail. I then pulled the thrust levers to idle. After 17634 posts and in excess of 2.7 million views on AF447 what happened to pitch and thrust? Everyone feels sorry for loss of lives and anyone can make a mistake but the way you expressed your contrition it seemed to suggest that occurrence of UAR is a death warrant. Is it?

[vilas]

CONF iture
I just posted airbus views about AOA. Not necessarily mine.

[CONF iture]

But I also definitely know ignorance of FCOM did not help pilots of EK521 either, the recent Dubai 3rd August.
How can you definitely know something that has not even been mentioned yet ... ?

(3) abiding by the vane manufacturer's DDP which gave the limits on output validity for the vanes?
According to A33Zab the vane in question has a limit close to 90 deg on the positive side, a A330 falling flat like a rock, so I think there was still some margin before invalidating the output.

I just posted airbus views about AOA. Not necessarily mine.
Not mine at all - I think their justifications are poor.
Like are their justifications for not thinking about linked sidesticks ...

[Uplinker]

Quote:
I was starting to think about unreliable speed when the over-speed warning went off.
If so then why on earth
Quote:
I deployed the speed brakes to no avail. I then pulled the thrust levers to idle.
After 17634 posts and in excess of 2.7 million views on AF447 what happened to pitch and thrust? Everyone feels sorry for loss of lives and anyone can make a mistake but the way you expressed your contrition it seemed to suggest that occurrence of UAR is a death warrant. Is it?

Vilas, I am just about to go flying so don't have time for a detailed answer, but please read my post again.

No the situation is not a death warrant. I was trying to explain that the situation is very subtle - it initially looked like an autothrust fault - and the overspeed warning is so loud and distracting that I did the wrong thing in the SIM - I tried to stop the noise by slowing the aircraft out of overspeed (compounded by my thinking it was a V aplha prot problem). I have admitted that I made this mistake in the SIM and shared it here, so I do not expect criticism thanks. 'Why on earth' you say, and I totally agree - I can't believe I did it myself, and my reason for posting was to give some insight into perhaps why the AF447 pilots got confused and did what they did.

I think it was an extremely valuable exercise the TRE and Captain gave me, - very subtle unreliable speed at max altitude - and I think we should all experience it WITHOUT prior knowledge of what is going to happen.

[vilas]

Uplinker
I was trying to explain that the situation is very subtle . Sure it is. Read my post UAR is very serious situation to identify and correct and in my opinion something that was not going to happen by accident. As you found it. It only means proper training which the 447 crew didn't have. And in absence of that I had said When looking for possible improvements of the equipment we should look to future and not bring in AF447 because how an insufficiently trained crew would have used that enhancement is impossible to guess. But I definitely have problem with reading of FCOM does not make a pilot, and reading up on emergency procedures does not prevent from acting differently in real live.
Fly safe. To fly safe without knowledge needs lots of luck which the unfortunate crew of 447 and EK521 didn't have. If the pitots had not frozen that fateful night or had the crew of 521 not decided to GA after touch down they may have retired peacefully after 20 years without knowing what they would have done on those occasions. But lesser mortals need to survive through knowledge which may keep them alive through the experience should it happen.

[vilas]

Uplinker


“I AM A HISTORY MAJOR. I BELIEVE THAT THE PAST IS PROLOGUE. BUT MOST AIRCRAFT ACCIDENTS ARE NOT ACTS OF GOD. WE TAKE WHAT WE LEARNT SO IT DOESN’T HAPPEN AGAIN. BUT THAT AIN’T GONNA HAPPEN IF NOBODY SAYS ANYTHING.THAT’S THE DARN TRUTH.” JAMES HALL, NTSB
How true!

[Owain Glyndwr]

@Confiture

If you read Chris Scotts posting 1107 you will see that the discussion related to the 60kt validity limit not the maximum angle the vane could read so your remarks aren't really relevant to Chris's point.

[Lonewolf_50]

@Uplinker: thank you for sharing your experience. That sim you were on was a training event, and I tip my cap to the Captain and TRE who provided you with a training opportunity.


In one of the early threads I asked "what did they see?" meaning the two in the two seats of AF 447. You have given me an idea of what they saw, but more importantly, what they heard and what they didn't hear. I think your sim experience on a surprise UAS confirms a suspicion a lot of people had (in the early discussions) that in the back of PF's mind was the idea to not overspeed the aircraft.
But that may have been somewhere more than the back of his mind: if the aural warning just would not stop, what he heard, and what he didn't hear, might be just as critical to understanding how that event played out as it did. (Points made above about audio channel saturation will not be repeated.)

Thank you, again, for sharing your training experiences. :ok:

[RAT 5]

that in the back of PF's mind was the idea to not overspeed the aircraft.
But that may have been somewhere more than the back of his mind: if the aural warning just would not stop, what he heard, and what he didn't hear, might be just as critical to understanding how that event played out as it did.

A pilot uses more than one sense. Under stress it is usually the sound (ears) that gets filtered out first and sight takes over. Sight can then become very tunnelled and all other things are shut out. PM is shouting at you WTF; then they are trying to give guidance about how to escape the problem: all to no avail as you do not hear them. Neither do you see all the other information that is screaming (visually) at you. You are focused on the PFD because that is what you have always done.
Time to pause and realise that the senses do not combine into common sense. Something must be wrong; it does not compute. High attitude at FL370 means an impossible over speed. The warning must be false. So what is correct? Difficult at 3000', but 37,000. That's a lot of time.
There was a B727 (Air Peru I think) that had a faulty static line at medium level. (not the B757 with blanked static ports during takeoff). The guys pushed & pulled believing the altimeter and ASI; but of course they were acting in the opposite sense. I'm not sure power/attitude entered the analysis. They were in an idle descent I think.
At soem point there needs to be a pause, back to basics, and then an analysis with all senses to discover what you can trust. In AF it's curious that the sound over-rode the visual.
I've seen RTO's in the sim, with the crew calling Mayday to ATC with the fire bell still ringing.

There were many human factors at play, plus training factors.

[CONF iture]

If you read Chris Scotts posting 1107 you will see that the discussion related to the 60kt validity limit not the maximum angle the vane could read so your remarks aren't really relevant to Chris's point.
And I question that 60kt validity limit.
Why CAS measurements should invalidate AoA values and shut down the stall warning ?
That aircraft was in an airflow of 100kt, ample airflow for the AoA probes to positively confirm the stall.
Just when the captain enters the flight deck, the stall warning quits. For him if stall there was, it is not anymore. His mental perception of the situation is send on erroneous tracks.
As Uplinker mentioned in his experiment, when you start thinking in one direction, it is hard to turn back.

[vilas]

Uplinker
VIRTUALLY ALL AVIATION ACCIDENTS ARE CAUSED BECAUSE SOMEONE DOES TOO MUCH TOO SOON, FOLLOWED VERY QUICKLY BY TOO LITTLE TOO LATE. Steve Wilson, NTSB 1996This can happen with any abnormality and unless it is recognised you will only insulate yourself against UAR. Airbus climbing to REC MAX over speed is the last thing likely to happen. Unable to cancel over speed warning, application of speed brake in climb, not noticing increase in VLS and thrust lever to idle, stall and application of Abnormal Valphaprot was it or abnormal Vls to a stalled aircraft, didn't hear stall warning which goes on and on with a priority over other warnings and at the end of it you suggested radical changes to aircraft systems such as over speed warning, stall warnings with hepatic feed back, changes to Pitot static concept of speed measurement, you forgot to ask for AOA gauge may be you are not sure you would have noticed it anyway. On top of everything you said you were going on a flight I thought a vacation to an exotic south Pacific island was a better option. All that happened was due to a wrong diagnosis, no corroboration due to fixation, confirmation bias only looking for evidence to confirm the faulty decision and rapid application of inappropriate corrective actions. all forms of UAR are already explained at length, stall warning already has priority over others.
Cheers and happy flying.

[Owain Glyndwr]

I agree with you that the airspeed was well above 60 kts and that the AOA signals were in reality valid. My point is that if the vane manufacturers had declared their equipment to be reliable only above 60 kts then AI had no choice but to use that value in their logic.

>And I question that 60kt validity limit.

Only the vane manufacturers could tell you why 60 kts real airspeed was the limit.

>Why CAS measurements should invalidate AoA values and shut down the stall warning ?

Because nobody is going to certify a system that continues to work normally even though it knows (or is being told) that its input data is wrong - in old computer terms garbage in, garbage out. The fact that there is a cross linking between the CAS/EAS relationship and very high AOAs complicates matters

That being said, there is a simple change in the logic which would eliminate the problem - the stall warning, having been activated by a valid AOA signal should remain latched until is receives a valid signal that AOA has reduced to below the stall trigger value

[Uplinker]

I echo Lonewolf and I did thank my SIM TRE and Captain that day. The scenario was the Captain's idea - he is a TRE as well. I am not the only line pilot to have become trapped by this - he said that everyone he has done this to in the SIM have reacted in the same way I did, (apart from the V alpha prot OEB).

I am a normal line pilot with experience of basic turboprops as well as basic jets and of course Airbus. My reaction to this scenario in the SIM was terrible and I am of course very embarrassed, but I had not actually seen this demonstrated, and the lead-up to the event is very subtle. I posted my SIM experience so that other normal line pilots like myself could be made aware of how subtle this can be - I don't think there is enough training in this area.

Vilas you seem to suggest that I SHOULD have heard the "stall stall", but the point I am making is that I am telling you that I didn't, and those poor sods on AF447 obviously didn't either. You might think it is impossible not to hear the spoken warning, but my brain blocked it out, that's what I am telling you. You also suggest I should have a vacation and your implication is a vacation from flying - well that is charming, but no thanks.

I did not have to tell everybody how I :mad: up - I could have kept quiet, but I thought it was more important to post my experience for the greater good.

As I said: if ever the speed tapes are doing something that seems even slightly unusual, no matter how slowly or gently they move or how much they might agree with each other : follow the unreliable speed drill. Both tapes may well appear to be perfectly normal and both may seem to indicate the same speed and speed changes.

Be aware that the overspeed alarm may well sound and remember it can be cancelled by using the emergency cancel button; something I temporarily forgot.

[Chris Scott]

Uplinker,

As some others have already said, your experience has given much food for thought, and FWIW I raise my hat to you for bravely sharing it with us.

Good flying!

[safetypee]

Uplinker, thank you for sharing your experiences.
The greatest experiences are those which are learnt, better still when shared, and of even greater value when heeded by others.

[CONF iture]

That being said, there is a simple change in the logic which would eliminate the problem - the stall warning, having been activated by a valid AOA signal should remain latched until is receives a valid signal that AOA has reduced to below the stall trigger value
But isn't it already exactly what the official documentation pretends to be doing :
When the threshold is reached, a permanent aural alert (“STALL, STALL” synthetic voice then cricket) is triggered until a correct angle-of-attack is recovered.

How 60kt can be a limit for the stall warning when officially unreliable speeds do not affect that stall warning ???
Unreliable speeds can be anything, from high numbers to zero.
Rely on the stall warning that could be triggered in alternate or direct law. It is not affected by unreliable speeds, because it is based on angle of attack.

I do question the Airbus documentation ...

[Owain Glyndwr]

The bold wording describes how the system operates when supplied with valid aoa data.- as I am sure you understand very well. A stall warning system that uses aoa as a primary input cannot function if deprived of that data, which is also something I think you understand.
But we are going over old ground and I see little point in repetition

[alf5071h]

Uplinker, :ok:
Take care not to extent your experience too far. Detecting unusual speed tape behaviour depends on having a datum; what is 'unusual', when to act, the dividing line between normal and abnormal.

EFIS sensor failures are usually clear cut - blank display / red flag. Another form of failure is the state of 'no computed data', where the sensor is working but not outputting valid data.
In all of these cases the manufacturer has to undertake a risk assessment and only then as necessary provide a crew drill for rectification or risk mitigation.

However, in the event of unusual system behaviours without alerts or warning (very very unusual, i.e. low risk) then crew intervention might be required; but given system reliability and certification requirements it would be more likely that the situation has been miss assessed;- "what have I misunderstood or not seen".

Most abnormal drills only apply to the situation as defined by the manufacturer; do not attempt to fit a procedure to a situation.
Infrequently pilots will encounter situations where their assessments are inaccurate and thus choose an inappropriate procedure; a situation and reasoning which you eruditely recalled from your simulator experience.

The lesson to be learnt is to reassess a situation, particularly if the chosen drill is ineffective.
But how long to wait, how much time is available, what else to check, ... such is the pilots burden, experience, knowledge, judgement.

But all is not lost; with diligent observation pilots can store knowledge of what is 'normal' (a datum), which can help in the very rare situations.
We would be unfortunate to encounter one of these in a career ... except those, in one form or another, which do exist, more often generated by ourselves; and because of this they involve mind numbing surprise and reluctance to change.

[Mr Optimistic]

Pax so free to ignore. OG, re the stall warning, I think the point about latching the warning is that the system alarmed on valid data, the data then went invalid (as it happens because of the scenario which generated the alarm) and the system logic gave priority to the validity limit. So the system discounted it's previous diagnosis which was based on data it judged valid and just shut up. The logic designers missed this in my view; at the least some warning that the system was off line could be generated ie you might be stalled but I can't tell, best check yourselves!

Edit: mind you if the environment is such that you don't register the aural alarm, as witnessed above, perhaps other design changes are needed first. Perhaps the mitigation claimed in the safety case by raising an aural alarm needs to be factored if other alarms are sounding concurrently.

BTW, wasn't Uplinked case a bit more insidious than AF ? They had the a/p drop out, not the slowly developing situation in Ups case. Mind you, the captain absenting himself could have been a clue that something was afoot :)

[Clandestino]

nice to see you guys back

I second that!

No, really. I am glad that due to lack of fresh Airbus accidents, most of you are reduced to flogging the largely decomposed horse of AF447 threads with same old unrealistic theories and not quite believable "look what happened to me" stories.

Point about "I didn't hear stall warning so it should be made stronger and work below 60 kt" was covered in Final report, 1.16.2 and Appendix 7 to Interim2. 40-odd recorded events of pitot blockage and degradation to alternate law on 330/40ies ended uneventfully. Except AF447. Whoever got stall warning, heard it and pushed. Except that one crew. BEA was unable to explain what made AF447 case unique, or rather very rare, as similar stuff of pulling till impact in stall happened on DHC-8 and MD-80 before and A320 after the crash.

With 40 other similar cases on the type ending without scratch (except maybe TAM), it would be very brave to stake one's reputation on the claim "Aeroplane did it!" without protection of PPRuNeanonimity.

[vilas]

Clandestino
I agree with you.

[Mr Optimistic]

Pax again. I am surprised by this. The system is crew+ aircraft and it failed. From this rare accident, in the context of the very low probability targets used by the industry, I do not know why the conversation has ended here.

[Chris Scott]

Quote from Mr Optimistic:
"...I think the point about latching the warning is that the system alarmed on valid data, the data then went invalid (as it happens because of the scenario which generated the alarm) and the system logic gave priority to the validity limit. So the system discounted it's previous diagnosis which was based on data it judged valid and just shut up. "

Yes, that's a fair description. Owain's suggestion that the stall warning should be latched on until the system receives a valid non-stall AoA from the AoA sensor is a good one, IMO. That clearly was not the case in AF447 but - assuming he is quoting the relevant Airbus documentation correctly, without significant omission - Confit rightly points out that the Airbus documentation can be interpreted as promising that it would. Quote from AI documentation via CONF_iture:
"...a permanent aural alert (“STALL, STALL” synthetic voice then cricket) is triggered until a correct angle-of-attack is recovered."

I would define that as the first aspect of Airbus FBW stall-warning logic that might be reconsidered. The second area that concerns me was also applicable to the stall-warning systems on most of the six swept-wing transport types I've flown. As I commented recently here in post 1110 (http://www.pprune.org/tech-log/539756-af-447-thread-no-12-a-56.html#post9520773), the warning signals operate at a constant intensity regardless of how much the stall AoA is being exceeded. When the warning results from intermittent exceedances, perhaps with phase-advanced warnings in turbulence or wind-shear, the pilot may infer that the degree of exceedance, while unacceptable and demanding immediate recovery-action, is low. In the case of AF447, however, the intermittent nature of the warnings persisted (for reasons that, with the benefit of hindsight, are well understood) despite the stall becoming deeper and deeper. This could happen again.

However, moving away from the specific example of AF447: if a crew was suddenly provided with an AoA indicator on each PFD that appeared only when the stall warning was activated, and if that AoA clearly showed the degree of AoA exceedance, any subsequent removal of it due to sensor invalidation - announced with a suitable failure caption - would be far from ideal. But at least the pilot would have been given a good idea of the depth of the stall during the period of validity of the system.

The inclusion of an AoA indicator would demand initial and recurrent training in the simulator, of course, during which recoveries from low-altitude shallow stalls and high-altitude stalls, both shallow and deep, would be practised in Alternate or Direct Law. Simulators would need to be improved in the high AoA, high altitude regimes, assisted to some extent by data from AF 447.

The third area where I would suggest change relates to handling practice. On revenue flights airlines have increasingly discouraged, if not forbidden, flight without AP and FD, as well as the use of manual thrust, particularly at high altitudes. Pilots are expected to spend many thousands of mind-numbing (on long-haul) hours simply monitoring AP and A/THR, only to perform safely on the once-in-a-career occasion that one or both of them fail.

Although it would have to be in Normal Law, regular practice of handling cruise flight, including step climbs and descents, at least puts pilots in a stronger position to handle abnormalities such as befell AF447. Easy to read that a pitch change of one degree represents a VS change of about 800 ft/min at Mach 0.8; quite another to be in regular practice at doing it. Thus, the management of pitch & thrust become second nature, instrument scan is improved, and the panic factor in failure situations significantly reduced.

[Goldenrivett]

I would define that as the first aspect of Airbus FBW stall-warning logic that might be reconsidered.

AI has already considered the problem and is trialling new FWC software:
See post #1100

"STALL WARNING enhancement: Stall warning will work when:
Undetected erroneous computation of pitot
Pitot out of the airflow
Pitot obstructed by ice or any foreign material at any speed (function now possible below 60 kts)"

[A33Zab]

"STALL WARNING enhancement: Stall warning will work when:
Undetected erroneous computation of pitot
Pitot out of the airflow
Pitot obstructed by ice or any foreign material at any speed (function now possible below 60 kts)"


Actually the logic isn't changed, the AoA sensor information is fed trough the IRU part of ADIRU i.s.o. the Air Data part, resulting in the AoA data remaining available to FWC in case of Airspeed < 60 kts.

This kind of system updates depend on the modification status of the particulair aircraft/fleet.

AFAIK If you didn't opt for de BUSS enhancement you won't have the quoted "STALL WARNING enhancement"

Besides this there are more updates since the event.


BUSS(before event) and further enhancement >Reversible BUSS.
Hybrid FPA.
Visible Red 'STALL STALL' warning on PFD.


Related to the Blocked AoA sensor issues:

Separate AoA sensor monitoring.
Replacement of all UTAS sensors by Thales sensors.

[CONF iture]

Sorry Goldenrivett, I don't know why I didn't pay attention to the post #1100 (http://www.pprune.org/tech-log/539756-af-447-thread-no-12-a-55.html#post9518563) initially.
So I can see things have been moving on the software side and our concerns were well justified after all ...

[Lonewolf_50]

Clandestino, I invite you to visit the thread about the Egyptian A320 that recently fell from the sky between Crete and Cairo. Plenty of discussion of AB features there, though with the various tidbits and clues, at least UAS isn't in the list of factors felt likely so far.

[Chris Scott]

Hi Goldenrivett,

Apologies for overlooking your post #1100, and thanks for the heads-up on mods. Must admit, however, that - assuming your quote is verbatim - the AI information on the logic changes could be more specific and more informative.

Quote from A33Zab:
"Actually the logic isn't changed, the AoA sensor information is fed trough the IRU part of ADIRU i.s.o. the Air Data part, resulting in the AoA data remaining available to FWC in case of Airspeed < 60 kts."

Thanks for that, from which I infer that the minimum figure of 60 kt (sensed) IAS for validity still applies to all AoA data except that used for the stall warning?

[vilas]

A33Zab
Actually the logic isn't changed, the AoA sensor information is fed trough the IRU part of ADIRU i.s.o. the Air Data part, resulting in the AoA data remaining available to FWC in case of Airspeed < 60 kts.
When BUSS was installed it needed switching off all three ADRs and with that Stall warning would have disappeared, that is why they brought in a mod that gets AOA data through IRs, that's all. Whatever was happening through ADR now happens through IR. I do not think it has any connection to invalidity below 60kts. Yes you need BUSS for this MOD. The FPA has been modified through
MOI: 153528/P12909 (A320FAM)
Where with all ADRs loss baro-inertial vertical parameters are replaced by hybrid GPIRS parameters. As a result Bird is available and should be used in Unreliable speed situation.

[Chris Scott]

Quote from A33Zab (my emphasis):
"Besides this there are more updates since the event.
BUSS(before event) and further enhancement >Reversible BUSS.
Hybrid FPA.
Visible Red 'STALL STALL' warning on PFD."

The problem with a simple "STALL, STALL" warning on the PFD is that it is qualitative, but not quantitative. How is the pilot to decide what degree of pitch-down to apply?

In the past on swept-wing jets, we have been advised on the receipt of a stall warning to pitch down a relatively small amount AND apply TOGA thrust. While that technique has recently been rightly criticised (not least on this thread and its predecessors), it would probably suffice in most cases if the first activation of stall warning has happened immediately the stall AoA is exceeded - as would normally be the case on final approach. But in the event of UAS, the stall warning may not occur initially because of the consequent invalidation of AoA data. In that case the first stall warning activation may not take place until the a/c is already in a well-developed or even deep stall.

That is why I'm suggesting consideration be given to the provision of an AoA indicator that would appear on the PFD only in the unique situation of stall-warning activation. The degree of exceedance of stall AoA could be approximated in a clear graphic on the indicator, giving the pilot a good cue as to what kind of pitch-down may be required to start the recovery. I say "approximated" because some data needed to calculate the precise stall AoA may be unavailable or unreliable, but the stall warning system itself must be using a credible value.

After the initial pitch-down, a secondary stall could be more easily avoided in the subsequent pull-up if the AoA indicator remained displayed until the AoA (and perhaps pitch-attitude) returned to within normal ranges.

Yes, I realise this would increase the airlines' training costs...

[safetypee]

Chris your argument for a dedicated AoA display makes several assumptions.
First that attitude is proportional to the indicated AoA; this might not be true for large values, or a range of configurations, wt, cg, and in this instance gross mis trim.
Might there be a difference between a recovery using the alpha gauge only (military pilots?) vs the AoA value having to be interpreted to cue an attitude change; the latter being important re roll attitude.

Second, it is assumed that the crew will 'see' the indicator, comprehend its meaning, and act accordingly. EFIS aircraft already have forms of AoA displays, e.g. min speed and barbers pole, providing the ASI is working. Any new display could add workload in an emergency situation.
Where new displays have been introduced to minimise risk after a primary system failure; they are located in similar (logical) task related positions as those in normal operation.

A key aspect in this and similar accidents is that crews were apparently unaware of the situation and 'puzzled' by indications and cues already available; thus an important quality of any new display / warning is to trigger a change in perception, together with high quality information, - not necessarily about what is happening, but what to do.
This is a demanding design task, particularly as in the 'highlight' accidents, the crews put the aircraft into the stall, thus there was a strong belief that their awareness and actions were correct.

Also, with the thread continuing focus on recovering from an extreme situation, the problems of awareness preceding the event and methods of stall avoidance are being overlooked. How did the crews get into these situations, what was the basis of their awareness.
This accident involved a complex interaction and degradation of several systems, hence the concepts of BUSS and FPV using existing display location for 'failure' conditions, which appear to be have been chosen to provided a degree of normality for stall avoidance and recovery, not an extreme 'one off' accident.

A further area for consideration is whether protected aircraft generate crew dependance on the protections, vs indicators and crew action for non protected aircraft; which crew would have the better awareness. If this is the case then crews in protected could suffer the greater surprise, adding complexity and difficulty in comprehending the situation when the protections degrade.

[Uplinker]

Some good points, safetypee, and well put.

My personal experience combined with what we know about human performance factors suggests that the brain will ignore hearing in a crisis and therefore the audio "stall stall" is too subtle and might not be even noticed.

A visual warning on the PFD might work, but if the PFD is already confusing the pilot, then it might only cause more confusion. As a civilian pilot, I have never flown with an AoA gauge, so cannot comment. All the Cessnas, Pipers, Shorts, Dashs, and BAe146s that I flew previous to the Airbus have some sort of shaking felt through the controls as a stall is approached - either actual shaking of the horizontal stabiliser felt through the yoke, or an artificial stick shaker.

As a previous electronics engineer, it would seem to me a simple matter to make the Airbus side-stick vibrate in order to warn of an impending stall. A vibrating element such as the type used in mobile phones could be fitted into the side stick - in place of that oval panel on the top, and a small electronic driver circuit the size of a matchbox to convert the already present stall warning into pulsing the vibrating element on and off could be constructed for a few pounds. The wires feeding the vibrating element would route through the same channel in the side-stick as the wires to the PTT switch. So it would be a very simple retro fit.

Then, no matter how much the pilot's hearing had shut down, and no matter how confusing the PFD might be, the pulsed vibrating of the side-stick in their hand would warn of a stall, and should provide an instinctive un-stall reaction.

Some might say that I should not be thinking of modifying the aircraft, but this problem has killed people, so something should be done.

[safetypee]

There is always something to learn from an accident, providing we identify relevant issues.
In complex accidents it is difficult to identify clear safety benefits of technical solutions, particularly those events involving errant human behaviour; engineering arguments often revert to 'more training' or draft another SOP.
The industry needs a measure of the effectiveness of technical interventions being able to influence human behaviour; this cannot be absolute, only a judgement.

Stick shakers have demonstrated a high level of effectiveness. The 146 was particularly good because the stick was mounted on the 'floating' cockpit floor, so there was an enhanced effect which alerted pilots when the autos were engaged (although IIRC the 146 autos disengaged at Vss).
It would be interesting to investigate the effectiveness of floor or seat mounted shakers in sidestick aircraft for improving awareness and stall avoidance.

Thinking further afield, some notable stall accidents involved generic issues related to the operators training. Colgan had recently focussed on tail stall (requiring the crew to pull up), which was not applicable to the type. The A330 required refresher training for loss of airspeed, where memory items required an initial high nose attitude, which did not apply in the cruise.
As discussed previously, closer monitoring of training practices might help, so too an understanding of why regulators believed that these training programmes were necessary.

Much of what has been discussed and done for safety improvement focuses on a single event which rarely applies across the industry or for future 'unforeseeable' events; we tend to fix the last problem and overlook generic items because it is difficult to agree on the judgement of their projected effectiveness.

[Chris Scott]

Hi safetypee,
Thanks for your thoughtful responses and criticisms. Having been accustomed to them on five jet transports until I flew the A320, I agree that some form of stick-shaker should be considered. Just a few points to clarify.

Quote:
"Chris your argument for a dedicated AoA display makes several assumptions.
First that attitude is proportional to the indicated AoA..."

Presumably you are referring to the amount of pitch-down required for initial recovery? In fact I was careful not to suggest that if the AoA indicator showed the AoA was x degrees above the stall the pilot would simply need to reduce the pitch-attitude by the same amount. This is what I wrote:
"The degree of exceedance of stall AoA could be approximated in a clear graphic on the indicator, giving the pilot a good cue as to what kind of pitch-down may be required to start the recovery."

Clearly I'm not prescribing a technique for stall recovery. But I am suggesting that an AoA indicator would provide: (a) information on the degree of stall, particularly important if the initial warning has been delayed by UAS; and (b) a tool to be used during the recovery to help the pilot avoid a second stall during the pull-up.

On your second point: yes, I am assuming that the pilot "will 'see' the indicator, comprehend its meaning, and act accordingly." In any case, if the pilot isn't looking at the PFD, (s)he has little chance of effecting a recovery... The appearance there of a large AoA indicator, maybe accompanied by a flashing "STALL" caption, should grab the attention. The design would be as simple as possible consistent with showing clearly the degree of exceedance.

The problem with using the existing minimum-speed marker-bugs on the ASI (such as Alpha Max or Vsw) is the enormous variation of Vs with normal G. Any bug allowing for that would go down and up like a yo-yo during the recovery. And with UAS, IAS is not a usable tool.

Perhaps one of our ex-military guys will comment on the practicalities of using an AoA gauge for stall recovery.

Quote:
"Much of what has been discussed and done for safety improvement focuses on a single event which rarely applies across the industry or for future 'unforeseeable' events; we tend to fix the last problem and overlook generic items because it is difficult to agree on the judgement of their projected effectiveness."

That's generally true, but this being an AF447 thread we are bound to consider the combination of a UAS followed by a stall - in which the first stall warning may be inhibited while the stall develops steadily.

[Owain Glyndwr]

@ Chris Scott, safetypee

Interesting discussion but don't forget

JAR 25.207 Stall warning

(a)
(b) The warning may be furnished either through the inherent aerodynamic qualities of the aeroplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual warning device that requires attention of the crew within the cockpit is not acceptable by itself. ........................
(c)

[Chris Scott]

Thanks Owain,

From which I infer that the current Airbus FBW provision to comply with the JAR is the aural element.

A stick shaker or vibrator of some kind seems worthy of consideration, but would have no tactile effect unless and until the pilot took hold of the side-stick. So the initial warning would remain aural. (I'm not sure that a chair-shaker would be either acceptable or efficacious!)

safetypee writes of the BAe 146, and the stick-shaker/vibrator would not be greatly different from traditional types with which I'm familiar (VC10, B707, BAC 1-11, A310, DC10), except that the sidestick is so much smaller than their control-column/wheel combination.

Perhaps the stick vibration could be made to increase if the pilot pulls up... :}

[RAT 5]

Slightly expanding; and I ask from a human performance perspective. Do you think the outcome would have been the same in VMC daylight?

[IcePack]

Interesting in what uplinker states Soon after that, the nose dipped
We now know the simulators are not demonstrating the true nature of an A330 high altitude stall. AF447 nose did not dip! I had been flying the 330 for about 2 years when AF447 happened. Up to then all training in the sim demonstrated that the aircraft had conventional stall characteristics. So on the sim even if you held on back stick the nose would eventually drop/dip after some buffeting.
After all this time negative training is still alive & well. "Criminal IMHO"

[safetypee]

Chris, thanks for your reply #1157.
I had overlooked the first point, but the recovery technique is important and is directly associated with perception.
Much of this thread has been concerned with 'why didn't the crew know that they were stalled' - disbelief, biased by hindsight, and now because 'we' know the aircraft was stalled, all that is required is recovery.
RAT 5 - I judge not, why would VMC change the crew's perception, would this be sufficiently attention-getting to change the focus of attention - would the crew have looked out given the mental workload and puzzling flight deck warnings?

Uplinker's experience demonstrates the difficulties in understanding the situation.
Classic certification requires stall warning and then stall ident. 'Warning' (stick shake) requires interpretation for awareness, but 'Ident' (stick push)- after Vss awareness, is a direct indication of recovery action, don't interpret; act.
I suspect that Airbus argued that in protected aircraft these functions are not required, and/or the EFIS display supplemented awareness, particularly if the protections degraded. However, neither were available/reliable in this accident, thus the modifications primarily address awareness.
I don't know the details of the Airbus AoA - speed computation, but other systems (MD 80, Avro RJ) were sufficiently accurate for awareness, and that the computation accommodated different weights and 'g', but neither were the primary reference for certification.

My dated military AoA experience suggests that it was primarily a warning opposed to stall identification, not used to direct recovery; constant AoA for approach, or maximising performance, do not exceed the limit ... ... loss of control, losing the fight.

[safetypee]

IcePack, what you report might not be negative training, instead it reflects the choice of scenario and training expectation.
The simulator may well replicate a 'normal' stall, it would be surprising if it did not; however if you wish to replicate AF447 then the abnormal aircraft state has to be considered, particularly the trim setting, systems operation, and control input.

As discussed this is an example of point specific training - a stall as per AF447, opposed to training for low speed awareness, stall avoidance, or identification that the aircraft has stalled because of a surprising upset or self inflicted manoeuvre..

Most refresher stall training, simulator or real aircraft, adds little training value for minimising the risk in surprising upsets. In most scenarios the situation is 'framed' - i.e. 'stall training'; there is no difficulty or ambiguity in establishing the situation because you have already have the expectation of the event. Hence the value of Uplinker's 'surprising' experience

[vapilot2004]

Slightly expanding; and I ask from a human performance perspective. Do you think the outcome would have been the same in VMC daylight?

As pieces of the puzzle go, the horizon is a fairly good bit to have.

[RAT 5]

Regarding the VMC question: I doubt, in a low-level stall, it would have had much effect; time would have been very compressed and attention fixed inside. At FL350 there is plenty of time to allow you attention to search for all clues available. A V.2004 says the high nose attitude might have been easier to understand with an horizon in your peripheral vision. It would have been an extra sense when you could use all the help you could get in a moment of confusion.

[PEI_3721]

The horizon provides a reference for attitude, it does not indicate a stall. Depending on aircraft flap, cg, thrust, the aircraft can stall at a range of attitudes, e.g. normal training stall against the AF447 stall, or a stall in a climb (nose high attitude) with a high thrust setting opposed to an approach stall (nose low attitude).

[roulishollandais]

Probably you will find that post unrealistic and excessive but I try it to suggest more imaginative solutions to blocked situation and discussion . Sorry.
We are worrying from no real inflight stalls by test pilots. But the aircraft seems able to stall without damage. Why couldn't the manufacturer build a mimick without pilot to achieve these stalls until we learn enough to fly the plane like former wholly tested planes ? Perhaps my suggestion is crazy:} So I already apologize...

[Mr Optimistic]

Clouds going upwards at 12000ft per minute would have been another clue in daylight :)

[Chris Scott]

Hello RAT 5 and vapilot2004,

IIRC, both VMC and horizons are fairly nebulous concepts at FL350. Ever tried flying straight and level at that altitude without an artificial horizon?

What I would say is that perhaps one is more susceptible to panic in darkness, particularly in the early hours. And yes, as Mr Optimistic implies, clouds can be more helpful than empty space.

[RAT 5]

What I would say is that perhaps one is more susceptible to panic in darkness, particularly in the early hours.

That was exactly my point. I would expect some pilots to be more calm in daylight than others. Calmness might help solve the dilemmas in time.

[PEI_3721]

Roul, you suggest that no stall tests were conducted for the accident configuration; you may be right.
This accident appears to have been beyond anything foreseen by both the manufacturer and regulator, yet with hindsight, imagination - stating the obvious, it is suddenly easy.
The lack of foresight probably involved similar mental processes as the crew's inability to comprehend the situation; the regulators had several years to think about this, the crew much less.

There is no guarantee that even the highest standard of aircraft certification or an exceptional crew will prevent all accidents. Aircraft certification and crew regulation depend on judgement of reasonably low risk; aircraft system failures use probability (e.g. 10-9), but human performance and training is much more subjective; these aspects include awareness and decision making.

[gums]

From request by Chris:

The problem with using the existing minimum-speed marker-bugs on the ASI (such as Alpha Max or Vsw) is the enormous variation of Vs with normal G. Any bug allowing for that would go down and up like a yo-yo during the recovery. And with UAS, IAS is not a usable tool.

Perhaps one of our ex-military guys will comment on the practicalities of using an AoA gauge for stall recovery.

So your friendly Viper pilot answers.......

- The stall AoA when "clean" does not vary with gee or attitude, as most here already know, hence

- Our AoA indicators were primarily for the approach configuration, although we could use AoA when clean if it was displayed. The early Vipers did not display AoA unless gear was down. The A-7 displayed it all the time in the HUD and using the indexer lights. The VooDoo I flew in the 60's had a large round indicator with two needles - one for the stall/pitchup and the other for existing AoA ( that sucker was notorious, but McAir put a stick pusher on it and also an AoA limiter you could use that took over 60 pounds of force to override, then the 28 pound pusher! Heh heh).

- Stall in the Viper was almost impossible, but it could be had and exactly the way 447 did - keep nose higher than necessary and slow down quickly before the limiters prevented a stall AoA.

- Stall recovery using AoA was very simple, as the stall AoA was independent of attitude or gee ( previously asserted).

PUSH FORWARD OR RELAX BACK STICK/YOKE!!!

The small jets I flew showed an immediate reaction. The heavies take time due to inertial and possibly less sensitive aero reactions to control inputs. We saw a few posts from folks that duplicated the accident in the sim and it took thousands of feet to get flying again.

- I do not feel a lotta training is required to learn about AoA versus attitude vs speed versus control inputs. The key is representing the AoA with respect to one of those, and additionally WRT actual flight path in the inertial frame of reference. Our AoA "bracket" in the HUD was a no-brainer. Push the bracket down to reduce AoA, pull back and it went up. Sheesh. The position of the bracket WRT the flight path marker showed high or low or "just right" AoA for your configuration. The 777 prang at SFO was a great example of not having and using an effective AoA indication and/or HUD.

- I really support those that wish a tactile indication of AoA. We could have used one in the Viper, but the designers said we could just pull and roll as hard as we wished and nothing bad would happen. You know, like the 'bus, "you can't stall this jet". We did not lose anyone due to a deep stall back in those early years, but we had ejection seats!! Training and iproved flight control laws reduced incidents to nearly zero, best I can determine.

[roulishollandais]

@PEI_3721
" aircraft system failures use probability (e.g. 10-9), but human performance and training is much more subjective; these aspects include awareness and decision making"
With my math hat I have to say that use of numbers (e.g. 10-9) is often an illusion!
And human performance may be more objective that numbers if you use experience from professional guys like you. At least experience is the only way to validate numbers and system models ! (Descartes said that already)

[Chris Scott]

Quote:
"Stall recovery using AoA was very simple, as the stall AoA was independent of attitude or gee ( previously asserted)."

Thanks gums: knew I'd get a clear view of practical experience from you. So would it be fair to propose that, having stalled the a/c, one simply pushes to achieve an AoA of a few degrees below the stall, and then maintains that AoA as accurately as possible during the recovery from the dive? Once the a/c is climbing again, the pull-up can be eased to maintain a suitable pitch and the AoA will gradually reduce as the IAS or IMN rises to the desired climb speed. At that stage the stall recovery itself will have been completed.

I'm likely to get some stick from the likes of yourself, Owain and others, but at high altitude the stall (or low-speed buffet) AoA is much lower than low-down, due to compressibility effects, and therefore varies also with Mach. So I'm guessing that would have to be taken into account when choosing a recovery AoA?

Normally, the Airbus FACs (augmentation computers) or whatever would be able constantly to calculate and display the stall AoA, but in UAS that would not apply. So a ball-park, conservative figure of stall AoA would need to be displayed to enable the pilot to choose a safe target AoA for the recovery profile.

In either case, if terrain clearance was critical, the pilot might have to shoot for a higher AoA (i.e., a lower margin below the stall AoA displayed).

Does that make any sense?

[gums]

TNX for nice words, Chris.

Due to the mach relationship with the stall AoA, the numbers may vary but the procedure does not. The 447 accidenty had unreliable air data, so allowing for the mach effects was not possible. Nevertheless, you can see the change in AoA when you pull or push most of the time.

In AF447 the inertia and THS trimmed position would not show a quick change in AoA but it WOULD SHOW a high, stalled AoA!! In the A-7 HUD you would see the flight path marker off the bottom and the AoA bracket way up at the top. In the Viper you would only have the FPM, as AoA was not displayed in the HUD with gear up ( "you can't stall this jet", heh heh).

As far as physical stall indications go, the 'bus seems to have a really good "approach to stall" feeling. So good that you can fly thru the protections and have decent roll authority and no gross buffet.

Hope that helps....

[Winnerhofer]

https://fightersweep.com/6296/angle-of-attack-how-to-lose-a-bfm-engagement/
AOA vs Critical AOA
AOA systems have been on fighters for decades, and on heavy transport planes as well. But AOA has only recently gained more attention from the FAA and legislators for applications in General Aviation (GA) and business aircraft. One such highly publicized event that highlighted the significance of AOA was the crash of the Air France flight 447 Airbus in June 2009 that killed all 216 people on board.
Investigators concluded that the aircraft’s airspeed probes had iced over providing erroneous indications to the pilots, and that the AOA system and it’s “gauge” was not available to pilots in the cockpit. They also concluded that having an AOA gauge could have saved the stricken crew.

[gonebutnotforgotten]

All this discussion of the merits of an AOA presentation in the AF447 accident is interesting and doubtless instructive, but the fact is surely that once the aircraft got to 40+ deg AOA, there was precious little chance of any stall recovery. Theoretically a sustained pitch down... to -30 deg or so... would have been effective, but who on earth would ever have done that in a large civil transport at night, AOA presentation or no AOA presentation? The authorities would be far better employed thinking how to ensure that crews have the required skills to keep the aircraft straight and level in all circumstances where controls are effective, than running down the UPRT road. The crew spectacularly failed on that flight and any suggestion that a crew with that skill set could cope successfully with UPRT is ridiculous IMHO.

Yes there are additional measures that could conceivably be taken to further improve the stall warning system on the A330, but as an old boss of mine once said in a slightly different context 'this [wind tunnel] is fool-proof, but it's not bloody fool proof'. Most improvements come at the expense of further complexity, which brings its own problems.

[gums]

Hate to disagree, "gone", but you do not need to get the nose down well below the horizon to break the stall.

- problem is pitch authority. In our little jet we simply ran out of pitch authority and the sucker also had a point on the pitch moment curves due to our ceegee where we would settle into a nice stall and the FLCS kept commanding "nose down" even tho "nose up" stabilator command still had some authority. So they put in a pure manual override feature and we could "rock" the sucker outta the deep stall.

The 447 jet was in a "deeply stalled" condition ( not classic "deep stall") and the THS and elevators were still capable of inducing a nose down pitch moment or at least reducing what existed.

- By manually trimming nose down and holding nose down stick, 447 would have reduced AoA and maybe sooner than most folks think. No need to have the nose down 10 or 15 degrees or more. Hell, prolly could have broken the stall with 4 or 5 degrees nose down, It's the AoA!!! It is not the pitch attitude.

The folks here that duplicated the accident in sims knew what they had to do and still took over 10,000 or 15,000 feet to recover. I think a good test pilot could beat that, but you have to play the cards you are dealt with the crew.

- The trimmed THS played a large role, IMHO. We had the same problem in the Viper, but we could use our trim roller wheel and the coolie hat to help. Nevertheless, we did not have a clear indication that the FLCS had trimmed to the max position for the stabilators, and I am not sure the 'bus does either.

Oh well, .......

[vilas]

Buss trim wheel will show it is full up but crew is not expected to look there nor there is a need. It is the pitch. Keep it sufficiently below the horizon and if it doesn't stay there use the trim to keep it there it will work fine. Full up THS in Perpignan caused the problem because of low altitude it became impossible to do anything.

[gonebutnotforgotten]

Gums,

Thanks for those thoughts - I've not seen a thorough analysis of the dynamics of 447 post stall, maybe there is a link somewhere in this thread and I missed it, but it's surely not just a question of adequate pitch authority. I know that the aircraft was, as you say, merely deeply stalled, not deep stalled, and so it was capable of being pitched down, had the crew ever tried to do so. But that doesn't alter the fact that its flight path angle was very very negative and even going to say 5 deg nose down would still have left it fully stalled with massive AOA and drag. I don't know how realistic simulators are in that area, not very I suspect, so assertions that the sim recovered are not totally convincing. I believe Airbus stopped at about 20 deg in their flight test... and I thought they deserved a medal for going that far.

[RAT 5]

Would this A330 have been able to roll out of the stall to gain some pitch authority later on as the stall was broken?
If so, and considering SA parameters would be improved in daylight, you'll understand my earlier thinking about what effect night had on this scenario. The high nose attitude, i.e. seeing only sky, IMHO might have helped them understand where they were and what they were doing and thus hinted to stop doing it. Ultimately they might have sensed what to do and how to do it and appreciated they had lots of air underneath them and where the horizon was. In the dark, and a panic sets in and takes over, that loss if visual sense surely did not help any.

[Linktrained]

What was the THS showing on Uplinker's demonstration on #1119 as frozen ? AF447 was fully NOSE UP, if I remember correctly.
WHO DOES EVER LOOK?

Could somebody say what the NORMAL range of THS could be expected in CRUISING flight ?
( I would not look normally,either, but I am not AB rated.)

As a trainee I had tried using the Trim wheel on an AS Oxford in 1949 at Hamble to round out... It looked professional, I thought.

My Instructor said " Don't do that... Think about a possible Overshoot. " I never did THAT , showing off again.)

[vilas]

How will Daylight make any difference if the visibility is poor? Isn't instrument flying done with reference to attitude? A pilot at high altititude has to have some idea of attitude even if you want to climb.Airbus supposed to have good roll control in stall.

[Turbine D]

RAT 5,
Would this A330 have been able to roll out of the stall to gain some pitch authority later on as the stall was broken?
Going back to AF 447 Thread No. 9, here is some information of one of the two sim exercises that indicated recovery from a full stall could be possible. The comments on the sim exercise below was done by PJ2, a former A-330 captain, now retired.
In the sim exercises, the SS was held full forward to achieve about 10degND pitch. The THS followed up on the command and returned to about a -3deg position. Recovery took about 40 seconds. (Note for others: I realize the sim cannot replicate full-stall conditions due absence of data but neither is the behaviour completely irrelevant).

For the exercise anyway and from my pov, there was sufficient elevator available to get the nose down, and the job was made easier by the THS following up the SS ND commands.

There was another sim trial which gave basically the same result and there was a analysis of data the indicated AF 447 could have been recovered by pushing the SS forward and holding it.

As I recall from a stall at 35,000 Ft., recovery was achieved around 20-25 thousand feet. As I recall, there was caution at the recovery point to take care in introducing nose up for fear of creating another stall.

[Linktrained]

Further to #1182

IF THS is usually " 5 units Plus or Minus 2 units" .... But is seen to be outside this range ... THAT might make a Pilot suspect that something might be WRONG.


There were THREE pilots on AF447. ( Just ONE on the Sim )


" Our HEARING is the first SENSE to be shut down." #1136
I am not sure that this was known when a Potential Chief Pilot for a new Airline was being checked by our Fleet Manager was FAILED for failing to " Stop for an Engine Fire before V1... "

He was sent home.

( Some years later our Fleet Manager asked me if I felt that he had done the right thing.. With the THEN knowledge.. I felt that he had done the right thing. The FIRE Warning Had been close to the Potential Chief Pilot's left ear... And he had done NOTHING.

[Chris Scott]

Quote from Linktrained:
"IF THS is usually " 5 units Plus or Minus 2 units" .... But is seen to be outside this range ... THAT might make a Pilot suspect that something might be WRONG. "

Not having flown the A330, I stand to be corrected, but I think 2 deg NU plus-or-minus 2 deg might be nearer the norm in high altitude cruise. It varies, as you would appreciate, with CG position, weight and speed.

In AF447, the PF's inputs on the sidestick resulted in the THS correctly auto-trimming ultimately to its nose-up trim-stop of about 13 deg NU. This could have been reversed, of course, by sustained forward command on the sidestick, as PJ2 demonstrated in the simulator (see quote by Turbine D, above).

[vilas]

After having held the stick back till THS went full up, the recovery is faster if you manually trim forward while holding the nose down. Our HEARING is the first SENSE to be shut down." but the iris opens full wide to gather maximum light to help you see provided you look at the PFD to see the attitude and not speed which was unreliable anyway. This is a case as I quoted the NTSB guy someone doing too much too soon followed by too little too late.

[Linktrained]

Chris,
Thanks,

I used "units" because I too have not flown the A330. Your "2 deg NU plus-or-minus 2 deg " looks like what I was trying to say.

But to fly very much out of this kind of range without good reason - and apparently without noticing or comment...

My fairly ordinary car has an oil pressure gauge which is backed up with an oil-pressure warning light. This would come on if the oil pressure fell below a certain figure. The system was installed when the car was made.

(As a York F/O I could notice an increase of 1 or 2 Kts when the Captain went back to the rear toilet, when hand flying with A/P U/S-, Captains weighed more as a percentage of A.U.W., then .)

[RAT 5]

How will Daylight make any difference if the visibility is poor? Isn't instrument flying done with reference to attitude?
but the iris opens full wide to gather maximum light to help you see provided you look at the PFD to see the attitude

In daylight, if you look out the side window (ok you can't see the wing tip) as you pull up for the loop you will have no doubt what your attitude is. However, here was a case of not keeping the G on over the top. ;)

[vilas]

Uplinker
AF447 has run the whole gamut but I am not sure whether this article on use of simulators from airbus FAST publication of 24May1999 was discussed. It raises a question mark on credibility of simulator behaviour outside the flight envelope. Produced below:


USE OF SIMULATORS


We manufacturers were very concerned over the types of manoeuvres being flown in simulators and the conclusions that were being drawn from them. Simulators, like any computer system, are only as good as the data that goes into them. That means the data package that is given to the simulator manufacturer. And we test pilots do not deliberately lose control of our aircraft just to get data for the simulator. And even when that happens, one isolated incident does not provide much information because of the very complicated equations that govern dynamic manoeuvres involving non-linear aerodynamics and inertia effects.
The complete data package includes a part that is drawn from actual flight tests, a part that uses wind tunnel data, and the rest which is pure extrapolation. It should be obvious that firm conclusions about aircraft behaviour can only be drawn from the parts of the flight envelope that are based on hard data. This in fact means being not far from the centre of the flight envelope; the part that is used in normal service. It does not cover the edges of the envelope. I should also add that most of the data actually collected in flight is from quasi-static manoeuvres. Thus, dynamic manoeuvring is not very well represented. In fact, a typical data package has flight test data for the areas described in Table 1. In other words, you have reasonable cover up to quite high sideslips and quite high angles of attack (AOA), but not at the same time. Furthermore, the matching between aircraft stalling tests and the simulator concentrates mainly on the longitudinal axis. This means that the simulator model is able to correctly reproducethe stalling speeds and the pitching behaviour, but fidelity is not ensured for rolling efficiency based on a simplified model of wind tunnel data) or for possible asymmetric stalling of the wings. Also, the range for one engine inoperative is much less than the range for all engines operating and linear interpolation is assumed between low and high Mach numbers.Wind tunnel data goes further. For example,a typical data package would cover the areas described in table 2. In fact, this is a perfectly adequate coverage to conductall normal training needs. But it is insufficient to evaluate recovery techniques from loss of control incidents. Where as, the training managers were all in the habit of demonstrating the handling characteristics beyond the stall; often telling their trainees that the rudder is far more effective than aileron and induces less drag and has no vices! In short, they were developing handling techniques from simulators that were outside their guaranteed domain. Simulators can be used for upset training, but the training should be confined to the normal flight envelope. For example, training should stop at the stall warning.They are “ virtual” aircraft and they should not be used to develop techniques at the edges of the flight envelope. This is work for test pilots and flight test engineers using their knowledge gained from flight testing the “ real”aircraft

[IcePack]

Vilas thanks for that. As I said AF447's nose did not dip/drop.

[Uplinker]

Thank you vilas.

[IcePack]

Also those that have hand flown a 2000 ft climb in a real A330 at high altitude 38to40g. & have done the same in the sim; will appreciate the " vast " difference in how the aircraft handles. Now think what the real aircraft handles like in alternate law at high altitude. Well their are not many pilots who know/ experienced that.
Whatever hindsight says the pilots of A447 were in unknown/untrained territory so some sympathy should be awarded.
Those that say they could have done better, maybe should think about their experience of handling Airbus FBW aircraft in alternate law at high altitude.

[Uplinker]

My thoughts exactly, Icepack.

Also: these days in the SIM we are told about a particular thing, maybe given a presentation in the briefing room, then we go straight into the SIM and do it. So we know what is going to happen, we are expecting it, and unsurprisingly we know how to deal with it.

Things such as this need to be sprung on us without prior warning to ensure we are robust enough - and if not, then more training is required*. If we have just been told about something 30 minutes ago, 99% of pilots will be able to recognise it and recover correctly !

I would also like to see in the SIM the full lead-up to and all the warnings and mode reversions etc. of recent accidents and every OEB that is published. Words on a page are all very well, but until you actually see what they saw and experience what they experienced, it is not easy to fully appreciate and assimilate all the issues.


*Yeah, I know: it costs too much money blah blah.

[RAT 5]

Also those that have hand flown a 2000 ft climb in a real A330 at high altitude 38to40g. & have done the same in the sim; will appreciate the " vast " difference in how the aircraft handles.

I wonder how many pilots of any modern jet a/c have hand flown their steed at high FL's. During LT I always used to introduce the student to such a heresy. You could sense the pitch response in <100' deviation to avoid apoplectic ATC queries, and somewhere en-route, if you're lucky these days, there might be a track change sufficient to feel the roll sensitivity.
If cruising below RVSM it was also interesting, and if ever you found an opportunity above, it was more so.
Most enjoyed the experienced; some were nervous as a turnip on Halloween and even declined. To my knowledge it is not a standard LT item. However, when asked why do it; I replied that a u/s AP was not a reason to ground the a/c. It would still fly and be controllable. An old friend of mine, TRE A340 Air Mauritius, had to do just that after airborne from LHR all the way south. Shock horror HAL had gone AWOL at 1000'. The pilots swapped PF roles at sensible intervals. Wide eyed amazement by the F/O and all on the ground at home base.

[Chris Scott]

Quote from RAT5:
"I wonder how many pilots of any modern jet a/c have hand flown their steed at high FL's. During LT I always used to introduce the student to such a heresy. You could sense the pitch response in <100' deviation to avoid apoplectic ATC queries, and somewhere en-route, if you're lucky these days, there might be a track change sufficient to feel the roll sensitivity.
If cruising below RVSM it was also interesting, and if ever you found an opportunity above, it was more so.
Most enjoyed the experienced; some were nervous as a turnip on Halloween and even declined. To my knowledge it is not a standard LT item. However, when asked why do it; I replied that a u/s AP was not a reason to ground the a/c. It would still fly and be controllable."

As you say, this seems to be regarded as a heresy today, yet the lack of a serviceable AP is not necessarily a no-go item (admittedly, I don't have an A330 MMEL to hand). Yet an A330's flying characteristics at M0.82 at FL350, for example, are not much different from first or second-generation jets at the same speed and altitude. The difference is that C* presumably makes pitch control much easier on the A330 than on traditional types, as it certainly does on the A320.

On one flight in the 1970s when I was on the B707-320, the single AP went u/s in the climb out of Caracas for London. (No A/THR on that type, although the F/E would assist.) The skipper and I shared the handling, including step-climbs eventually to FL410. No RVSM in those days, admittedly, but handling to within plus-or-minus 100 ft was quite feasible for about 20 minutes at a time.

It's worrying that handling skills and practice have allegedly lapsed to a point where most pilots regard cruise flight as being beyond their remit except, of course, in a very-rare failure case. As I wrote in post #1146:
"...Although it would have to be in Normal Law, regular practice of handling cruise flight, including step climbs and descents, at least puts pilots in a stronger position to handle abnormalities such as befell AF447. Easy to read that a pitch change of one degree represents a VS change of about 800 ft/min at Mach 0.8; quite another to be in regular practice at doing it. Thus, the management of pitch & thrust become second nature, instrument scan is improved, and the panic factor in failure situations significantly reduced."

I could have added that using manual thrust at the same time would be useful training for the UAS case - in terms of both throttle handling and observing power settings.

[RAT 5]

I remember in my naive enthusiastic sponge sucking days as a RHS HS-125 flying the tiny jet from Stavanger- LHR FL410 manually the whole way, at night, while the boss did business down the back until TOD. No big deal, and a great learning period.

[Winnerhofer]

https://www.youtube.com/watch?v=WqxzpGJbzmI

[Concours77]

From what I recall of the CVR, the narrator must be mistaken, when he says: "Here, the Captain declares, 'STALL', descend...." At 2:13 of the CVR?

I remember there is no mention of Stall in the CVR?

[Winnerhofer]

Well spotted!
Shame that the narrator got that one wrong.

[vilas]

Not only that he mentions the cause of stall as running out of oxygen in the atmosphere.

[Concours77]

Tragic it wasn't so simple as loss of cabin pressure.
Also tragic three qualified pilots mentioned not once the actual STALL, or the warnings.

What puzzles, is if they were disregarding purposely the SW, there is no aural record of their reasoning to not heed it. (CRM)

Especially when PF says, "yes climb, we are at four thousand" (sic)

Next narrator mistake: my recall of CVR has Bonin recognise altitude prompting his response to "Pull...." when they were at ten thousand?

Also, my memory has their last words, in chorus: "Tire....Tire....Tire". Video shows these were not last words.....


"Tire.... French for command, "Pull!" ?

So much unknown....

[Winnerhofer]

tire = pull.

[IcePack]

& at one point "we have no indications" wonder what was meant?

[Concours77]

"Indications" suggests (minimally) no "indicated" air speed(s). Possible loss of both PFDs?

Probably, since these words were spoken to Captain as he entered (?) it was offered to support the statement "we have lost control"? Later statement by Captain: "Here, Here, and here...." Might be his gestures in attempting to help PF understand his attitude? Also "Watch your lateral" likely spoken at the verge of worse upset. In the challenging situation, he was not likely to be suggesting the Rudder bar to merely "fine tune the ride". (?)

[artee]

From the Guardian:
https://www.theguardian.com/world/2016/dec/20/mh370-new-report-proposes-shifting-plane-search-to-unexplored-area

"The Australian authorities leading the search for MH370 have a “high degree of confidence” that the plane’s wreck is not to be found in the expanse of Indian ocean they have spent more than two years searching."

"New analysis of the satellite data, combined with drift analysis, has identified the most likely point that MH370 hit the water as being close to the so-called “seventh arc”, north of the current search zone. Experts have identified a new area of approximately 25,000 sq km as “the area with the highest probability of containing the wreckage of the aircraft”, given the 110,000 sq km that have been eliminated."

[Winnerhofer]

https://criticaluncertainties.com/2015/02/20/unreliable-airspeed-we-can-do-better/
More:
https://criticaluncertainties.com/2010/04/14/the-airbus-a330-aircraft-system-safety/

[Concours77]

AoA wasn't available to the crew, except in an obscure way: it can be calculated using the FD, and the "bird" (FPV?). Frustrating their decision making, especially after the Stall established, was the Pitch wasn't crazy, even when the AoA reached 40+.....it was 10-15 degrees, actual. None of the three had experienced a mushing Stalled trajectory, except perhaps Bonin the glider pilot.

[EMIT]

In an airliner, at flight levels in the 350 to 380 numbers, a pitch angle of 10 to 15 degrees IS RIDICULOUS!!!

The usual pitch angle for level flight is between 2 and 3 degrees and the angle for a sustainable climb is one half to one whole degree higher. More performance is not available in an airliner at high level.

[Concours77]

I think you are correct. But I used the word "crazy" meaning "impossible".
Of course they were at cruise, initially, but once they lost control, their perception undoubtedly altered, with unusual cues, one blank panel, etc.

"Crazy speed" is a clue to what I perceived to be a very confusing set of sensory inputs....

They likely never knew the AoA was that high, though it was accurate? How would they know, they had no instruments to tell them AoA. But Pitch at 10-15 degrees they experienced at least once per launch, right?

We weren't there. But they endured four minutes of "Pitch" that was "ridiculous" all the while trying to arrest a descent by pulling up......

At the last: "Pull, Pull, Pull....."


Give them a break?

[roulishollandais]

"Indications" suggests (minimally) no "indicated" air speed(s). Possible loss of both PFDs?

Probably, since these words were spoken to Captain as he entered (?) it was offered to support the statement "we have lost control"? Later statement by Captain: "Here, Here, and here...." Might be his gestures in attempting to help PF understand his attitude? Also "Watch your lateral" likely spoken at the verge of worse upset. In the challenging situation, he was not likely to be suggesting the Rudder bar to merely "fine tune the ride". (?)
ACARS showed that both PFD were lost very quickly

[Concours77]

Has anyone ever assembled a chronology based solely on what the pilots had to work with?
It has always bothered me "...pulled the whole time into Stall...." When they may have had little or no data?

Synchronized with g, controls, attitude (from FDR), and itinerant CVR comment, it would be instructive?

My conclusion from what I have read is that they had no idea they were descending (at up to 17000 rpm), even after the 10000 foot alert, and GPW? All three still wanted to pull....at four thousand feet (where did they get that?)

"Crazy Speed. We have no indications. We've lost control..." Once there, (and they got there fairly quickly), how many ace pilots here care to explain what they think happened in the seven mile descent?

Any out there who have stabilized a Stalled A330 into a mushing, reasonably level aspect for seven miles of descent in turbulence at night without instruments?

[Winnerhofer]

40 pre-AF447 incidents had occurred with the A330.
All had recovered.
Again many factors FCOM and QRH were different at AF compared for example with LX regarding Memory Items in 2009.
These keep on chopping and changing as there also software and hardware upgrades.

[KayPam]

Has anyone ever assembled a chronology based solely on what the pilots had to work with?
It has always bothered me "...pulled the whole time into Stall...." When they may have had little or no data?


In my opinion, a pilot pulling on their stick during cruise should have no trouble imagining that they will climb, at first.
And they should be very well aware of the fact that they could very rapidly climb above their performance ceiling as well. (as other problems)

This problem is much more common than you'd imagine.
Differently put:
Angle of attack protection laws (or systems) are activated unvoluntarily much more often than you'd imagine !

[RAT 5]

It was true then, it is true still. Push stick forward houses get bigger; pull stick back houses get smaller; keep pulling back houses get bigger again.

It's late at night, tiredness has crept in and this discussion is years old. Sorry for being simplistic.

[Winnerhofer]

No news on the long-awaited trial.
In France, it takes 10 years for cases of big accident/incidents to end up in court.
This has also been slowed by terrorism which takes up all the resources.
France only spends a measly 1% GDP on justice.
I would guess in 2018 at the earliest as France has Presidential elections coming up.

[Concours77]

Rat5

"....Push stick forward houses get bigger; pull stick back houses get smaller; keep pulling back houses get bigger again....."

Stick needs a pull, the aircraft was seven degrees low at loss of a/p. Then the displays went dark. After sixteen seconds the FO declared alternate law. Then THS cranked in full NU. Until impact. No Pitch, no AoA, dark, (no houses in sight), Roll Direct, difficult (if not impossible) to drop the nose.

Yes, eight years on... And still people make simple minded judgments. Mine too, I suppose.

Winnerhofer: Does France "Apportion" responsibility in its verdicts?

[RAT 5]

Thanks Concours. I must have missed something in the fine detail, and I admit to being KISS minded. I defer to those more knowledgeable of this particular beast.

[Winnerhofer]

Judicial Action in the Aftermath of Aviation Accidents:
A Global Perspective

“The first thing we do, let’s kill all the lawyers.”
Henry VI, Part 2 Act 4, scene 2

In the United States the acts or omissions that cause or contribute to aviation accidents are ordinarily not the subject of criminal investigation and prosecution. However, in many other countries around the world, criminal prosecution has become a nearly automatic response to aviation accidents. This “criminalization” trend in aviation affects not only pilots but maintenance personnel, owners and operators, OEMs and even air traffic controllers. Accidents by definition are just that, unforeseen and unintended events. In the case of intentional acts resulting in an accident prosecution could be warranted in any country.

Accident investigation and criminal prosecution

A fundamental tension exists between accident investigations and the potential prosecution of the actors involved in an airplane accident. “The sole purpose of the investigation of an accident shall be the prevention of accidents and incidents. It is not the purpose of this activity to apportion blame or liability.” ICAO Annex 13. However, an accident investigation in its effort to uncover the facts, determine the probable and contributing causes and when appropriate make safety recommendations runs headlong into criminal investigations and potential prosecution utilizing some or all of an agency’s findings to apportion blame or liability.

While the frequency of aviation accidents declines, the frequency of criminal prosecution appears to be on the rise. In the 43-year period from 1956 through 1999, criminal investigations of 27 aviation accidents were conducted. In the succeeding decade there have been more than 28 criminal investigations.

Legal systems compared

Criminal justice systems differ among various countries around the world. Following are some broad comparisons among the predominant systems: common law and civil law.
Common law systems, exemplified by the United States and the United Kingdom, are adversarial-based where the accused is represented by an attorney from the beginning. This system relies on prior court decisions to establish legal precedent. In the United States there exists an entire body of law devoted to criminal procedure establishing how criminal laws are to be enforced, especially with regard to a defendant’s Constitutional rights. Defendants can demand their rights to due process, exercise their right to remain silent, require a speedy trial and be represented by legal counsel.
Conversely, under the civil law system such as those in France, Germany and Japan an accused typically receives fewer rights in comparison. The civil system adopts an inquisitorial model where the sovereign’s search for justice is guided by strict application of written law. An examining, or investigating, judge conducts an inquiry into a possible crime where the accused is charged only after the inquisition phase--questioning witnesses, interrogating suspects—is completed. The goal of the criminal investigation is to gather evidence, whether incriminating or exculpatory, and is only conducted with the authorization of the prosecutor’s office. If the examining judge finds a valid case against a person, the accused then has to stand trial.
While the accident investigation agencies take a safety-based approach, the judicial investigation takes an assign-blame approach. Nonetheless, the vagaries of the criminal (and civil) legal process will depend on the country in which it is conducted.
Selected aviation accident criminal prosecutions worldwide

The following accidents are a representative sampling of those for which flight crews, owners and operators, air traffic controllers and others have been prosecuted within the past several years.

Olympic Airways, Romanian airspace, September 1999

On September 14, 1999, a Falcon 900B operated by Olympic Airways for the Government of Greece, experienced a series of pitch oscillations during a descent while enroute from Athens, Greece, to Bucharest, Romania. There were 13 persons aboard, of whom 7 were fatally injured and 2 seriously injured. The flight crewmembers were uninjured. The crew attempted a manual override of the autopilot while leveling the aircraft at an intermediate altitude during the descent into Bucharest. The aircraft landed at Bucharest.

The Romanian Ministry of Transport, Civil Aviation Inspectorate investigated and determined the cause to be pilot error: inadequate assessment of the PITCH FEEL malfunction, overriding of the autopilot in the pitch channel, inappropriate inputs on the control column at high speed and with Arthur unit failed in “low-speed” mode leading to Pilot Induced Oscillations and seat-belts not fastened during descent flight phase.

The Greek public prosecutor brought manslaughter charges against the two pilots for causing the passengers’ deaths and eight Olympic Airways ground engineers for failing to repair the pitch feel system. In 2002, after a lengthy criminal trial in Athens, the captain was found to be criminally liable for the deaths and injuries to the passengers. The first officer and engineers were acquitted. The captain received a five year prison sentence, reduced to three years on appeal. A further appeal to the Greek Supreme Court remains pending.

Criminal charges were later brought against the OEM, Dassault Aviation, and a verdict concerning which also remains pending.

Concorde, Paris, July, 2000

A Concorde, Air France flight 4590, enroute from Paris Charles de Gaulle to JFK caught fire on takeoff and crashed near Le Bourget at Gonesse on July 25, 2000. All 109 persons on board perished along with four on the ground. The immediate cause of the fire was a blown tire that caused a fuel tank to rupture and the ensuing fire resulted in loss of control.

The BEA investigation found that the Concorde was overloaded for takeoff, one tire was cut by a metal strip from a just-departed Continental DC-10, a high speed abort above Vr was untenable, and the subsequent fire and resulting structural damage was so severe that the ensuing crash was inevitable. Several months after the BEA report was released a criminal investigation began in March 2005.

Three years later the public prosecutor brought criminal negligence charges against the former head of Concorde division of Aerospatiale and the Concorde chief engineer. Likewise, manslaughter charges were brought against a Continental mechanic and a maintenance manager, an Aerospatiale manager and a French airline regulator. Pretrial attempts to dismiss or reduce the charges failed.

Almost 10 years after the accident, trial began in Pontoise Criminal Court located in a Paris suburb in February 2010. After a four-month trial and months of deliberation, the three-judge panel returned a judgment on December 6, 2010. They found Continental criminally liable and fined it €200,000 and ordered it to pay Air France €1 million. The Continental mechanic received a 15-month suspended sentence while the other employee was acquitted as were the other four defendants. In addition Continental was ordered to pay 70% of compensation payments made by Air France to the victims. Continental is appealing the judgment.

Crossair, Zurich, November, 2001

Crossair Flight LX 3597 was an Avro RJ100 regional airliner on a scheduled flight from Berlin, Germany to Zurich, Switzerland that crashed during its approach to land at Zurich Airport on November 24, 2001. Twenty-four of the thirty-three people on board were killed. Those who died were the cockpit crew of two, one flight attendant, and twenty-one passengers.

The investigation conducted by the Swiss Aircraft Accident Investigation Bureau concluded that the accident was controlled flight into terrain (CFIT) caused by a series of pilot errors and navigation mistakes that led the plane off-course. No fault was found with the airliner itself.

The Swiss public prosecutor brought criminal charges against six Crossair executives. The trial began on May 5, 2008, six and one-half years after the accident. Among other arguments the prosecutor blamed the Crossair management for maintaining a culture of fear, preventing pilots from reporting incidents and encouraging them to take risks rather than choosing safe–but more costly–procedures.

On May 16, 2008 the Swiss federal court acquitted the Crossair chairman, its CEO and four other former airline employees of negligent homicide. The prosecution had requested suspended sentences for the six defendants ranging from 12 months to two years.

DHL/Bashkrian mid-air, Southern Germany, July 2002

On July 1, 2002, Bashkrian Flight 2937, a Tupolev Tu-154M, carrying 57 passengers and 12 crew, collided in mid-air with DHL Flight 611, a Boeing 757-23 APF, a cargo jet with just two pilots aboard. Both aircraft were flying at approximately 36,000 feet MSL in German airspace and were under the control of Skyguide. Only one air traffic controller was handling their airspace because the other duty controller was resting. Thus one controller was controlling two sectors simultaneously and he failed to recognize the proximity of the two airplanes. When he did, he instructed the Bashkrian pilot to descend 1,000 feet. Seconds later, the Bashkrian’s TCAS commanded a climb. Those pilots complied with the controller’s instruction to descend. At this moment, the TCAS of the DHL aircraft commanded a descent and the pilots did so. The two aircraft collided at 34,890 feet MSL. Upon impact, the B757’s vertical stabilizer sliced through the Bashkrian’s fuselage, causing an explosion, breaking the Tu-154M into several pieces scattering debris over a large area. The B757 crashed shortly thereafter in an uncontrolled descent. All of the 71 persons on board both airplanes died.

The German Federal Bureau of Aircraft Accidents Investigations (BFU) determined that the causes of the accident were “managerial incompetence and systems failures” attributed to Skyguide and failure of the TCAS systems.
A criminal investigation was initiated as to Skyguide in May 2004. On August 7, 2006, a Swiss prosecutor filed manslaughter charges against eight Skyguide employees. After a lengthy trial three of the four Skyguide managers were given suspended prison terms, the fourth was ordered to pay a fine. The other four Skyguide employees were found not guilty.


Platinum Jet, Challenger 600 accident, Teterboro, February, 2005

On February 2, 2005, a Bombardier Challenger CL-600 ran off the departure end of runway 6 at Teterboro Airport, New Jersey. The crew abandoned the takeoff when the airplane failed to rotate. The airplane sliced through a perimeter fence, crossed a six-lane highway, and rolled through a parking lot before coming to rest partially inside a building. The pilots were seriously injured, as were two occupants in the vehicle struck by the airplane on the highway. The flight attendant, eight passengers, and one person in the building received minor injuries. The airplane was destroyed.

The NTSB determined the probable cause of the accident to be the pilots’ failure to ensure that the airplane was loaded within certified weight-and-balance limits and their attempt to take off with the center of gravity beyond the forward limit, which prevented the airplane from rotating at Vr.

Criminal charges for conspiracy, fraud and endangering flight safety by falsifying flight logs and overloading airplanes with fuel were brought against the pilot and the executives and directors of flight charter and maintenance. Verdicts were returned after a one-month trial in U. S. District Court for New Jersey. The jury convicted the pilot and one of the owners and founders of the company.

Excelaire Embraer Legacy and GOL B-737 over Amazon, September 2006

September 29, 2006, a Gol Boeing 737-800 was en route from Manaus, Brazil to Rio de Janeiro, when it collided with an Embraer Legacy operated by Excelaire. All 154 passengers aboard the Boeing 737 were killed. The 7 occupants of the Legacy survived. The collision occurred approximately midway between Brasilia and Manaus at 37,000 feet. The B 737 suffered major structural damage, losing nearly half of its left wing causing it to nose-dive and enter an uncontrollable spin. The Legacy, despite serious damage to the left horizontal stabilizer and left winglet, was able to continue flying. The crew landed the aircraft at a large military complex of the Brazilian Air Force (BAF) about 100 miles from the collision point.

The crew of the Legacy were detained and questioned relentlessly by the BAF and Agencia Nacional de Aviacao Civil (ANAC). The crew maintained that at the time of the collision they had lost contact with Brasilia ATC and the Legacy’s TCAS did not alert them of any traffic.

Four days later, the Legacy’s captain and first officer were ordered to surrender their passports pending further investigation. The prosecutor had made the request because the possibility of pilot error could not be ruled out. Later on December 5, 2006 a Brazilian federal judge effectively overruled the surrender order. However, prior to pilots’ departure the Brazil Federal Police formally charged the crew with “endangering an aircraft” which carries a maximum 12-year prison term. The pilots agreed to return for trial.

Formal investigations were conducted by Brazil’s Aeronautical Accidents Investigation and Prevention Center (CENIPA) and the NTSB. These agencies agreeing on most facts arrived at different conclusions. CENIPA concluded the accident was caused by mistakes made by both air traffic controllers and by the Legacy pilots, whereas the NTSB focused on the controller and the ATC system. The NTSB found that both flight crews acted properly, but were placed on a collision course by ATC.

On June 1, 2007 the two Legacy pilots and four controllers were indicted and charged with “exposing an aircraft to danger.” The negligence charges against the pilots were dismissed and reverted to charges of “imprudence.” All charges against two controllers were dismissed and reduced charges against the other two. A fifth controller was indicted. In January, 2010 the negligence charges against the pilots were reinstated. In October of 2010, a military court convicted one controller but he appealed and then was acquitted.

Ultimately in May, 2011, the Legacy pilots were sentenced to 4 years, 4 months in prison but the sentence was commuted to community service to be served in the United States. The Judge sentenced one controller to a prison term of up to 3 years, 4 months but found he was eligible to do community service in Brazil instead.
What we learn from these investigations and prosecutions

Criminal investigation and prosecutions can be based on a wide variety of factors. Among these factors are statutory mandate as a result of a criminal inquest, magnitude of accident such as number of airplanes and fatalities, and the notoriety of persons on board. Intent is irrelevant. Criminal investigations can and do use the output of accident investigations to prepare indictments.

Prosecution targets include pilots, maintenance and other line personnel, managers, executives, retirees, air traffic control and controllers, OEM’s and owners.
The defense of criminal prosecution is time-consuming and disruptive. Not only must the individuals accused become embroiled in the legal process, often in a country with which they are unfamiliar, but corporate defendants are also exposed. It is not uncommon for legal action, both criminal and civil, to extend well beyond 10 years post accident.
An individual’s personal liberty and perhaps his pocketbook are at risk. In some cases, pilots have been detained, imprisoned without a hearing or clear explanation of the reasons. A corporation’s resources can be taxed whether it is an owner or operator of the accident airplane or the manufacturer. Maintenance and operations do come under strict scrutiny.
A response from the international aviation community

Strong, thoughtful and persuasive responses have come from the international aviation community to the increasing criminalization of aviation accidents in recent years and these have not yet had the impact over a state’s accident investigation or legal system one would have hoped. For example the Joint Resolution Regarding Criminalization of Aviation Accidents, dated October 17, 2006 declared that “Criminal investigations can and do hinder the critical information gathering portions of an accident investigation, and subsequently interfere with successful prevention of future aviation industry accidents.” Importantly the signatories declared that “criminalization of aviation accidents is not a deterrent or in the public interest.”


What else can be done?

Certain actions and countermeasures may be used to protect pilots, owners, operators, and others related to the accident. Actions can be taken in advance and post-accident in order to minimize or eliminate the risk of criminal prosecution or to mount a sturdy defense if indicted and tried. The following are equally applicable to owners, operators, pilots/crew members and even OEM management and employees:

• Become familiar with the law and legal precedents, if any, in the countries of operation and the accident investigation agencies.
• Implement or revise an Emergency Response Plan to include a prompt response to accidents or incidents occurring outside the United States.
o Identify legal counsel in potential jurisdictions.
o Retain experienced aviation counsel in advance.
o Identify competent aviation consultants in areas such as operations and accident reconstruction.
o Be certain to secure all pertinent documents, electronic and otherwise.
o Notify insurers, of course. Payment of defense may be available.
• Cooperate with the accident investigation authority
o Obtain pre-interview advice and counsel from competent counsel in the jurisdiction.
o Provide all requested documentation, paper and electronic.
o Attend and participate in any hearings with counsel.
o Contest final accident report probable cause when appropriate.
• Obtain experienced trial counsel if prosecuted.

Persevere. There is light at the end of the tunnel.

Conclusion

Criminalizing of unintentional, negligent conduct does not improve aviation safety nor does it provide relief to the accident victims. The fear of criminal prosecution – the criminalization of aviation accidents – can impede the investigation and undermine the cooperation of flight crews, mechanics, and manufacturers.

[KayPam]

Rat5

"....Push stick forward houses get bigger; pull stick back houses get smaller; keep pulling back houses get bigger again....."

Stick needs a pull, the aircraft was seven degrees low at loss of a/p. Then the displays went dark. After sixteen seconds the FO declared alternate law. Then THS cranked in full NU. Until impact. No Pitch, no AoA, dark, (no houses in sight), Roll Direct, difficult (if not impossible) to drop the nose.

Yes, eight years on... And still people make simple minded judgments. Mine too, I suppose.

Winnerhofer: Does France "Apportion" responsibility in its verdicts?

Sir.. The basics of the A330 TR (or basic thinking after having learnt the AGK-instruments ATPL theory course) inform us that there are at least two independent GYRO sources for attitude as well as a standby source.
(I'm not sure whether IRS3 feeds the standby horizon or not)

The gyrolasers do not freeze ! So pitch information was of course available.
AoA was available, and is not related to Pitot probes, so even though the value was not displayed (which is very debatable in my opinion), the stall warning was reliable*. Again, basic TR knowledge..
And engine instruments do not freeze as well.
That's it, that's the minimum you needed.

One sentence I heard during a conversation between confirmed engineers was the following :
"According to regulations, this type of situation [not AF447, something completely different] should be completely manageable without requiring exceptional piloting skills. In this case [not AF447], doing nothing was a perfect solution. And doing nothing absolutely does not require *exceptional piloting skills*"
* : in English whereas the rest was in French
It caused a huge laughter in the room.

But it seems that in this case (AF447), doing nothing would have required some skills (or SA)


To finish with, even if you're going to do change your altitude, why climb ?
To get higher up into the coffin corner ? To get above the performance ceiling ?

*Up to the point where CAS decreased below 60kt, which is, I was told, illegal, but is again TR knowledge.

[Concours77]

KayPam:

"To finish with, even if you're going to do change your altitude, why climb ?
To get higher up into the coffin corner ? To get above the performance ceiling ?"

1. From DFDR, the a/c attitude at loss of a/p was four degrees nose down and ten degrees right roll. The PF immediately pulled on the stick, to regain level flight (from BEA Interim)
2. The aircraft did not climb immediately, it started climbing ten seconds after pilot input. (Also BEA)
3. The a/c was in Roll Direct as it had changed law to AL2b. So initial left correction started a roll input chase of neutral/level. Some over control, PIO occupied the PF, who was also trying to listen to PNF's anxiety about altitude not pitch. "Go Down!!"
4. We do not know which ADIRU was in control, which had succumbed to "outlier". Do we?
5. There have been incidents in which this type has climbed without pilot input, and remained unresponsive to attempts to descend....(Air Caraibes?)
6. Aren't Pitch (inertial) and AS (computed) latched together in each of the ADIRUs?
7. Where was Pitch displayed? On the two inop PFD' s? On which FD, which are supposed to be switched OFF in UAS?

I apologize for continuing comment after eight years...it seems unfair to the crew to judge them based on information we Know they did not have, and some of which we are not sure.
My intent as always is to help people avoid "going simple" in such a tragic and absolutely complex accident....

Thank you for your kind response....

[KayPam]

1. Yes, I think BEA indicated a possible reason for wanting to climb : the degraded altitude calculation indicated 400ft under target altitude. One must reckon that at this time, its unlikely that any pilot would consider themselves in an emergency and therefore would feel free to descend without proper ATC authorisation
2.
3. You mean that the PF climbed against the PNF's recommendation ?
I read the original transcripts (not translated) and the main problem with them is that the oral tone is lacking, hence it is impossible to know whether some sentences were comments or order. "You are descending now" and "you must descend" are two equally likely translations of "tu descends, là". Impossible to decide between them without hearing it, and even when hearing it it's likely that one could not decide which it was.
We even can read things like "là tu montes, donc tu descends" (literally "here you climb so you descend" which makes no sense in English, again translation problem and tone required)

4. I can bet (and probably could verify if I had time) that all artificial horizons were correct. About the indicated speeds, one should check parameters IAS1, IAS2 and ISISIAS in the recordings, but I believe these were indeed all lost (?) temporarily

5. An aircraft not responding to control inputs would be classified as a catastrophic failure and should not occur more than once per billion flight hours. It was not the case this night.

6. I don't know that for sure, but it does seem a bit stupid to lose the ground indications (GS, attitude, position) of a perfectly working IRS just because the pitot has frozen. So my guess is that Airbus engineers aren't that stupid ?

7. I think nobody knows for sure what was displayed on the PFDs, but there should have been at least an attitude indication on the emergency horizon.
I don't think it would be wise to follow the FDs in an abnormal situation.. And they should switch off on their own if the APs switch off due to lack of information I don't see how FDs could compute orders if the APs cannot.

I'm not appointing blame on anyone here (someone was asking if the French jurisdiction was doing it, just on the preceding page), just pointing out a few basic theoretical facts that imho should be kept in mind in case of such an incident. (because it starts with a simple incident : pitot information loss)

Don't you think the PF could have decided between high speed stall and low speed stall by looking at his GS ? Even with wind, the difference between the two should be in all cases sufficient to decide between high speed and low speed.

We should learn from accidents and try to improve safety. I would suggest these
1. The creation of a color code for each displayed parameter :
- white - normal, confirmed by multiple sources
- other color - abnormal, at least one source disagreeing significantly
- other color - abnormal, no redundance
- red - unreliable or unavailable information
1bis. there could be a new status page indicating which sources are known to be unreliable (e.g computer sending error signals), which sources are feeding information where, and if this information is consistent with other sources
2. The improvement of the standby instruments systems towards a very high reliability even at the cost of a slightly lower precision. For example, maybe the precision of modern DGPS could allow to compute a reasonably accurate attitude indication (with 7 receivers on each extreme point of the aircraft).

My (debatable) idea is that GPS would help confirm values computed by the usual way.
e.g if you measure a -8000fpm GPS descent rate, a -10000fpm indicated VSPD would be confirmed but if 0 fpm was displayed on the PFD, it would trigger an alarm (and color coded indication) (as well as the contrary)

[Uplinker]

The idea of a computer Status page might be useful, but could risk adding further confusion when basic flying skills were all that were needed.

See post #1119 on page 56, which although I had the added (self induced) complication of a suspected V Alpha prot event, really showed me how AF447 could have occurred, and in particular that the "STALL STALL" was continually sounding, but I did not hear it.

I really think we should all be allowed to regularly practice far more basic flying and basic instrument failures in every one of our regular 6 monthly SIMs.

For example

Partial panel work, e.g. loss of two ASI, or V/S, or ALT, or ATT, and flying by reference to what you have left.
Unusual attitude recovery.
Unreliable airspeed but not necessarily a madly varying speed tape, instead more subtle failures.
High altitude handling, including stalls and TCAS RAs.
Engine failures not only at V1, but in the intermediate climb, cruise, approach, or Go-around.
Memory drills.
More Go-arounds and windshear events.
Flying by sole reference to pitch and power.


We are always briefed to use the automatics, and a large amount of SIM time is taken up with learning all the automatic modes and functions. But we should NOT allow ourselves to get so rusty that we don't actually dare take the automatics out and fly manually when they are not providing the solution.

Busy line flying often means that we don't have the chance or don't want to risk screwing up an approach by flying fully manually, (AP and A/THR off), but if the CAA mandated three fully manual approaches every six months - as they used to for autolands - it could provide just enough of a jump-start start for the collective pilot confidence and skills to return.

[Concours77]

"2. The aircraft did not climb immediately, it started climbing ten seconds after pilot input. (Also BEA). Could this have added some urgency to the NU input? Not unresponsive but "lackluster response."? Or could this be data input problem that caused a too extreme Pitch target? see below, g value?

"3. You mean that the PF climbed against the PNF's recommendation ?"
That's hard to say. I did not read (certainly did not hear) "Unable" from PF. I am concerned that the PNF is seemingly quick to abandon his alarm about the ascent; did he suss PF situation (as it was perhaps) the A/C would not Pitch down, at least not sufficiently to arrest or reverse the ascent?

"5. An aircraft not responding to control inputs would be classified as a catastrophic failure and should not occur more than once per billion flight hours. It was not the case this night."
Not my inference, only that the A/C was initially slow to respond to NU. This would be important as it may have set the stage for over control in Pitch, as we see with Roll?

Not discussed, but is it agreed that Automatic Trim might well be inhibited with the loss of A/P and UAS? It seems to me a straightforward and (existing) trim value should be sustained? The goal in manual flight is maneuverability? Not Trimmed cruise or a not necessary pitch bias? It turned out the trim ended up biased fully NU, eliminating any sense of a neutral point with the stick? It resulted (imo) in giving the PF a confusing input as to stick position, and authority? He was concerned with Overspeed, ("do you think we have some crazy speed?") not likely to push the stick forward to the stop and sustain it there?

That's pretty much what I have... The responses have been gracious, and illuminating.

Thank you to Winnerhofer, KayPam, and Uplinker

[KayPam]

I really think we should all be allowed to regularly practice far more basic flying and basic instrument failures in every one of our regular 6 monthly SIMs.


I agree.

But I don't think the general public will agree to buy more expensive tickets, in order to allow for that supplementary training.

Concours77 : just regarding the overspeed issue : yes he did think he was in overspeed (at least it seems so). He was worried about high speed stall
But aircraft do go up to VD without high speed stalling..
Who even knows, beyond themselves, how far Airbus test pilots and engineers push the airplanes in the high speed range ? I read somewhere that the A380 went up to M0.99.
Given the sound barrier (ultra sharp increase of Cx at M1) it's unlikely to go beyond it, and so a high speed stall seems very unlikely with a A380.

Maybe pilots should be given more theoretical knowledge about the real limits of their aircraft ?

This would allow for a better "overview" of the system used, would not allow any voluntary exceedance of the parameters, but could prove useful in extreme situations.
This could help in situations like AF447 :
I am unsure whether I am stalling or high speed stalling. If I was high speed stalling, could I destroy my aircraft by pushing down to a -10° pitch ?
If a pilot knows for sure the answer to this question, he can make a more rational decision.

[Winnerhofer]

https://www.youtube.com/watch?v=VBNZ46zxY5E

[Concours77]

Is that audio an actual portrayal of the CVR? That contains a great deal more pilot discussion than I read from the report? Also the ambient noise adds a lot, if constructed from the actual data?

There was a time I could have translated that....that time is passed. Is there an English translation?

[KayPam]

You may or may not have noticed that much of the speech is told by the off-screen narrator. He should have a distinctive voice.
Regarding the text said by the pilot, I think it is accurate for the most part. But there are differences with the CVR transcript.

If you used to know French, you can probably still read the text in the BEA report and compare it with the audio.
https://www.bea.aero/docspa/2009/f-cp090601/pdf/annexe.01.pdf

BUT the tone is not available ! And that would be very useful to understand the meaning of many sentences.
I really don't understand why the CVR recordings are never released.
Anyone has an idea ?
Is it just the privacy of persons who have passed ? or is there any more obscure reason ?

[Concours77]

Three confused pilots in high anxiety, piloting a 100M jet, with 228 souls on board descending into the sea. Can't be good for business.

The interface is the bottom line...man/machine.

Contain, Control, Manage... Damage control...

[Winnerhofer]

The DCVR released by the BEA is hashed.
There's no way that when Dubois asked Bonin if he had licence, that the latter just answered "Yes".
There's more that came after that "Yes".
A source claims that a brief argument ensued as Robert entered.
The source claims that Bonin's spouse was on the flight deck all the time which explains the mysterious fourth voice.
Why was Dubois standing?
Why were Robert and Bonin not strapped properly?

[KayPam]

I do believe that the no good for business argument might be the most important one
Does Pprune know about the Habsheim crash ?
A 320 pilot, we're told, crashed his aircraft in the forest at the end of a short runway where he was making a low pass, with the utmost incompetence.
In practice, we can clearly see different markings on the DFDR photographed just after the crash, and the DFDR presented to the press when the judges seized it ten days later.
There are also gross unconsistencies in the BEA report including the DFDR data.
So in my humble opinion of 20-year late observer, there is at least something wierd with this case. If any one would like to discuss it further we could find a place to do it.

Back to AF447, there was an article in vanity fair which "revealed" supposedly secret conversations.
We learnt tremendously interesting details, like that a flight attendant was allegedly carrying brasilian meat in her hold luggage !

What does the D stand for in DCVR ? Digital like in DFDR ?

According to a French commentator, Dubois was standing because he did not have the **** "to grab one of his subordinates by the collar and throw him away from the controls". One will or will not subscribe to this analysis.

Why would you think that the copilots were not strapped properly ?

Regarding the "are you full ATPL" question, there are (...) just after it in the CVR transcript so that might be the following discussion about it.
Or, the discussion could have taken place in the full two minutes before the "yeah" and the next line transcripted.

[Concours77]

Why did Robert give up on trying to get Bonin to descend. What did he find out that satisfied him that Bonin could not descend? He made no effort to take control.

Why did Bonin reach for spoilers?

Did he really say "Eh, what are you doing?" That implies he assumed pilot error....then he stands in the middle, giving silent assent (as did Robert) that Bonin should continue to try to regain control.

The "sense" of CRM conveyed from the comments in the report is....bizarre.

A question about stick position? With full NU Trim, does the stick neutral point remain centered? If so and with full back stick, is the back limit (stop) sensed or displayed? Felt? How would a pilot trying to descend acclimate to a stick with Full NU bias? Does ND require more travel than when Trim ="0".? It would with full NU trim, no? Is authority a function of stick travel?

[KayPam]

An airbus in alternate law should keep its attitude stabilization. In direct law this will be lost (USE MAN PITCH TRIM)
But I'm not sure whether af447 was in alternate or direct law, but it's obvious that a full nose up THS will highly reduce your authority to pitch down, should you want it.

I do not understand all of your questions.
However you might be interested in this :
The airbus stick always feels the same, +/- 18° forward and backward, +/- 20° laterally.
Then the computers do all sorts of computations before transmitting them to the servocontrollers

[Concours77]

The a/c switched from Normal Law to Alternate Law 2 (b) @ 2:10:07.

That means Roll goes to Direct, Pitch remains g load. The Rudder switched to RTLU 2 degrees each way? Four degree sweep. The heading after loss of a/p drifted @ 1.5 degrees per second turning right....pretty sure that's correct.

Thanks.

[alf5071h]

There has been time to reflect on this accident and consider what has (has not) been learnt.
Although surprise, startle effect, was considered it was not rated particularly highly.
The effects of startle have been discussed more recently in http://www.pprune.org/rumours-news/572882-crj-down-sweden-17.html#post9613307.
Most of the points in the link could apply to AF447; unable to comprehend, communicate, no CRM ..., and an instinctive reaction. Also that startle applies to both crew, each independently, attempting to understand the situation. Furthermore, the surprise condition could continue, refreshed or renewed as other warnings and alerts occurred, and particularly that the situation was not improving with actions which were believed to be correct.

The last point might be debatable, but similar inappropriate actions can be identified in other so-called LoC accidents, e.g. Colgan, CRJ. In all of these accidents including AF447, the crew manoeuvred the aircraft into an upset condition.
The industry should consider the effect of training for one scenario on other situations, the possibly of inappropriate instinctive response.
Colgan had recently trained for 'tail stall' where the recovery required a sharp pull-up and flap retraction; the aircraft encountered a conventional stall, but the crew's actions were for a tail stall.
The CRJ suffered an IRS failure which resulted in an erroneous nose-up ADI indication. The PF appears to have taken upset recovery actions with a quick nose down control response.
In AF447 the crews actions were consistent with the memory items for dynamic UAS, whereas the situation required the follow-up actions applicable for level flight.

Did the then recently required UAS refresher training consider these different conditions?
The checklist differentiated between memory items and follow-up drills by an unusual qualification of 'safe conduct of the flight', which was not defined. Was this difference explained during training?
Would the relief PF had any experience of handling the UAS conditions; do operators' SOPs require the Commander to take manual control in all emergencies?
Did the most recent training consider alternative drills for 'loss of airspeed', together with multiple and confusing distractions of the ADC problems, systems reversion, and the First Officers' experience limited to reading the memory items of the abnormal drill.
The crew did exactly what they were taught; they were incapable of detecting the error, or consider other actions, or communicate due to the effects of surprise. 'Last practiced, best remembered'; particularly if surprised.

If the industry continues to believe that there is no limit to training, that humans can always be improved, without considering the situations human have to manage, and the limitations of human performance, then we may continue too encounter these rare and surprising accidents.
Surprising to us, but are the regulators also too surprised to realise? Knee-jerk reactions for LoC recovery training - instant reactions and action, whereas nowadays there is more emphasis on awareness and avoidance, but what about situational surprise.

[Concours77]

The Stall recovery training (more specifically approach to Stall) for this aircraft involved "limit altitude loss". That has some obvious drawbacks once the airframe is actually stalled. The Captain, Melvin Renfro, was surprised by an initial, and "spurious" Stall warning. He had left wing anti ice ON, which elevated the onset of the aural Stall Warn by twenty knots. It was, essentially, a fatal response to a bug speed. Lack of SA, hair trigger neuronal, male ego, etc.?

His initial Pull may have been related to either Tail Stall training, or "limit altitude loss". In either case, the unnecessary pull was the proximate cause of the actual Stall. Once Stalled, the aircraft was lost. I remember the altitude on long final at the time as about 1000 feet. He continued to pull on the column, overcoming the pusher, which requires seventy pounds pull to be defeated.

Muscle memory? Training? Inexperience? Lack of sterile cockpit?

In some cases too fine a point is put on "causes" that are irrelevant?

In 447, we actually are aware of the PF's concerns: "What's that smell?..."
"Do you feel crazy speed?" "Maybe spoilers...." "Mais non...." No mention of Stall Warn (seventy actuations continuous in the descent). As far as we know, right?

We are missing the most important (CVR) data available, not even CAM airstream signature is released? No intonation, no rebukes, no questions, no aural record. That is a disgrace.....

[PEI_3721]

Concours77, you appear to believe that its is a given right to hear the CVR; for you to interpret as you wish, or judge crew thoughts based on your experiences and knowledge, often limited to national and cultural norms. Whatever you might conclude is unlikely to change aviation; self-satisfaction is not always the best way forward for safety.
The world-standard for accident investigation and publication of data has been discussed previously.
The accident investigators report their findings and recommendations, the industry judges and heeds their advise. Operators and individuals are free to make their own interpretation, discuss aspects from unique viewpoints, and perhaps improve their sector of aviation, but don't expect everyone to agree.

[Concours77]

I take your point. I do not believe the data should be published without regard to its audience.....I do however take note of who is first on scene, who decides a course of action, and who are the "invited parties."

Government agencies, airframe manufacturers, engine manufacturers, end of.

All of the above have varying degrees of conflict. From the outset of most accidents, conflicts are rampant. To say that the usual agencies have no bias, and are completely objective, is to invite a chuckle.

I don't speak for any other than myself, but it occurs to me the occasional "ombudsman" would be welcome.

Boeing/pencil whipped skin inspections. Boeing/confidential logs: lithium batteries
Rolls Royce/test bed explosions: Trent. Airbus/ g data Habsheim.

Incomplete data relative to any accident invites suspicion... Transparency and disclosure are missing; the customer is compelled to "Trust, don't verify".

My position is not a popular one...or not?

[Winnerhofer]

https://www.youtube.com/watch?v=ZFyrTUN5_as

[Concours77]

Many mistakes made in that video. Many wrong statements. The scapegoat is identified.

Timing of first Stall warn is quite wrong. Last words of crew was not Bonin asking what's wrong. Bonin is not "Captain". "Perfectly good airplane"? Aircraft did not do as described.

Captain's first comments are wrong, etc. Even from the limited CVR data released, that depiction is nonsense, though undoubtedly "sufficient" for public consumption....

[Machinbird]

At present, the most critical element in an aircraft is the man/woman in control. How he perceives, how he analyzes, what he does, is under control of a brain that has been hard-wired to handle fear since before we became men. Some of the things that are hard wired in stressful, fear-inducing conditions are contrary to common sense and survival while in control of an aircraft.

How do we train to understand the effects of fear?
How do we train to handle the flow of chemical signals that are awash in the body during fearful incidents? Isn't the simulator an imperfect tool for inducing fear?
Where is the human operating manual that documents what the effects of of extreme fear are and how to handle fear? Have you seen one?

As an old Navy jet carrier pilot, I have seen fearful incidents. They can last for fractions of a second, several seconds, or a large number of minutes. With experience, you learn to gain control of your mind and your body and to perform at a high level.

But how do we teach new aviators to handle fear without undergoing actual fearful experiences?

Should we just assume that a pilot who is trained to fly in the center of his aircraft's performance envelope is going to somehow be ready to handle fear in an unusual situation where things suddenly go pear shaped? Does the simulator adequately train pilots to handle fear?
I don't think so.

Fear is the factor that is not adequately addressed in AF447 and the other accident that alf5071h mentions.

I think we had better find ways to address the fear factor effectively or else we will find pilots removed from the cockpit by automation that cannot become fearful.

[Concours77]

@machinbird

"At present, the most critical element in an aircraft is the man/woman in control. How he perceives, how he analyzes, what he does, is under control of a brain that has been hard-wired to handle fear since before we became men. Some of the things that are hard wired in stressful, fear-inducing conditions are contrary to common sense and survival while in control of an aircraft."

'Twas ever so....

I need to post one last comment..... Air Indonesia, MetroJet, AF.

Different types, but All Airbus.

1. Normal cruise established, or normal climb (Metro)
2. Abnormal, leading to loss of a/p (and Normal Law) (pitch remains in normal law)
3. Crazy Climb, not consistent with pilot's limited Pitch authority: g load factor.
4. Loss of control.
5. Loss of aircraft.

Each climb was beyond "robust" and imo, exceeding pilots limited stick due Normal Law pitch prohibitions at elevator.

In AF447. Climb reached 7000fpm, and "maximum" g load of +1.75

In Perpignan, we know also the airframe limited pilot's authority. (Is gload available in report?)

I submit that even if duBois was present at the beginning of the abnormal (a/p loss) and 'Commanded' Bonin to climb at the demonstrated rate, he could not.

The Airbus will not allow the pilot to climb in that fashion.

Unfortunately, that may introduce another look at the aircraft?

[KayPam]

3. I do not think so... Full back stick will give you +2.5G in normal law, that's more than enough to "satellize" you in a very short time.

Are you implying that Airbus makes aircraft that climb without being asked ? or that climb more than they're asked ?

And the pilot IS able to command +2.5G or alpha max, in normal law : he just has to maintain his full back stick input.

[Winnerhofer]

https://www.theguardian.com/technology/2016/oct/11/crash-how-computers-are-setting-us-up-disaster

[PEI_3721]

Mach, #1241, :ok:

fearful, surprise.

http://www.icao.int/Meetings/LOCI/Presentations/Managing%20Startle%20Individual%20Crew%20and%20Organizationa l%20Strategies.pdf

http://www98.griffith.edu.au/dspace/bitstream/handle/10072/54072/82496_1.pdf?sequence=1
N.B. Fear-potential startle.

Many aspects of the industry's response to accidents, and seen in this thread, is that the focus of safety activity is based on the outcome of events.
' The aircraft was out of control and crashed because the pilots could not recover ' and with all of the suppositions in that line of thought the focus is on recovery.
By considering why the crew manoeuvred into the upset condition would provide and alternative view which would focus on how to avoid these conditions.

A wider view still would include all of the 'inappropriate control actions' **. Similarly why these accidents also report poor or no CRM. All of these are features of surprise, the inability to understand, communicate, and 'acute stress response' activity.

** remember the safety initiative " Engine malfunction and inappropriate crew response " many years ago. There were many LoC outcomes, primarily because the crew failed to understand the situation and / or the control actions were inconsistent for the condition.

[Winnerhofer]

https://www.contrepoints.org/wp-content/uploads/2014/10/pilote-air-france-rené-le-honzec.jpg

[Winnerhofer]

Agree or disagree but commit at Agile Bodensee (http://pt.slideshare.net/pragmaticsolutions/agree-or-disagree-but-commit-at-agile-bodensee)

[markkal]

I have read somewhere that Fear is the leprosy of aviation. How does training handle it ? Will Uprt-Loc training adress it ?

[Machinbird]

I have read somewhere that Fear is the leprosy of aviation. How does training handle it ? Will Uprt-Loc training adress it ? Thinking back on my own military training, the key element is to take pilots well out of their comfort zone and teach them how to succeed despite adversity.
Example: All attitude jet unusual attitude recovery using nothing more than needle ball and airspeed and altimeter while flying under "the bag". (There was no peeking out from under the bag.)

[KayPam]

I have read somewhere that Fear is the leprosy of aviation. How does training handle it ? Will Uprt-Loc training adress it ?
In the only one "emergency" event that I had to manage, I was able to do the right thing in only a few seconds, thanks to "reflex actions" that we're taught.

However I do believe that military pilots who have to handle fear on a daily basis are much better equipped than us civilians to manage emergencies.

[Concours77]

jmo....

Fear is not a disease. Fear is a naturally occurring emotion that has kept the species alive lo these thousands of generations.

Courage is not fearlessness. If one's fear is so unmanageable that it turns often into panic, one should not risk another's life on his mental state.

Fear can be healthy. Panic is never positive. Panic is our makers last resort to keep us alive. Freeze, and maybe be unseen by the monster....

Cultivating the only defense against fear is a lifelong goal. That defense is Confidence, based on experience, alluded to by Mr. Machinbird...Phantom?