Horrifying. You have no idea how difficult it is to get dried egg out of the crotch of your uniform trousers... :E

More to the point it's not a "hole in the cheese", as there is no proof that connecting the things would have made a difference, and pilots have, on several occasions, ignored a yoke that was where it shouldn't have been - they are trained to look *through* it, not *at* it.

thf:
You are addressing a bedrock CRM issue: one pilot flies, the other monitors/assists. If they were, in Airbus fashion, "fighting over the controls" ... either the controls "sum" the conflicts or the "take command" function returns to Bonin (per how AB designed the interaction between the two side sticks), then your point on Robert being cut out of the loop (and hence calling the Captain?) goes to the heart of a CRM and cockpit gradient issue far more than a flight control style issue. (That, and at least one instrument scan that was broken/behind).

More troubling for AF than for Airbus, in some ways.

The further mess of going so far into stall that stall warning was disabled (AB design feature), lack of an AoA gage (done to death back in the original threads) and the return of a stall warning when AoA was again alive ... if they even acknowledged stall warning as other than spurious ... combined with the most recent "condition/response" training for approach to stall being the "down low/near the ground" scenario ... puts a lot of conflicting and non-normal things saturating the crew's awareness at the same time in a scenario I doubt either had seen in a sim.

Small wonder that at least one of them was confused.

Captain Dubois had quite a bit to clean up and sort out when he arrived on the flight deck and tried to figure out what these two had done to his plane when he left them alone together, in cruise, straight and level, a short while before that.

@LW_50:

Hullo sir - I do in general agree with what you're saying. If you don't mind a bit of clarification though, the stall warning was not explicitly "disabled" by the logic, it was more a case that the stall warning cannot function without reliably functioning AoA vanes, and the AoA vanes cannot function reliably without at least 60kts forward airspeed. While this scenario is part of the Airbus design spec, there has been a curious level of silence from other builders with regards to whether their current systems run to a similar spec or not. One might suppose that if a better spec existed from another manufacturer, they would have said so by now.

As I recall the discussion from the earlier threads, it quickly became apparent that this particular scenario is rather difficult to solve for every possible permutation of circumstances. The concept of "no warning is preferable to a false warning" is a reasonable one, but it seems that few thought it likely that one could apparently drop below 60kts IAS in mid-air, then come back to it from behind and reactivate the warning.

As for "fighting over the controls" - the only "DUAL INPUT"s happened towards the end of the sequence. As you state and I mentioned earlier, Bonin verbally handed over control to Robert more than once and both times silently took priority back. Robert's priority button would have changed to red in that instance, but in the heat of the moment it wouldn't be a tricky thing to miss.

I ask everyone to have another look at Fig. 64 and see what they think about the following points:
http://i1088.photobucket.com/albums/...f447_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.

Penny for anyone's thoughts?

At at least 60 knots forward airspeed we can suppose that a A330 (if in the air) is stalled (or no more what is called "flying")
Can we agree on this ? (I suppose yes)
So .. why (under the reason that AoA vanes cannot function reliably at this speed) stop the stall warning alarm .. as other parameters (but maybe not show or seen by the pilots) indicate a stall condition
I don't catch the logic of this one !
As I tell already before .. this will be a debate ( like here :) ) about this (and certainly other Airbus things) .. on the trial
Wait and see for the results ...

Not too sure about that as the airplane was already stalled when Robert took control.
That being said, not knowing how Bonin was actually dealing with the sidestick, he possibly lost trust in the FCS integrity so asked Dubois to switch off or reset some FCCs.

Airbus missed the opportunity to apply that Just Culture :
http://www.pprune.org/7450265-post576.html

I doubt the designers ever envisioned a scenario where an aircraft "in-flight" could be traveling less than 60 knots (it's even hard to envision now knowing that it happened).
On some of the older Boeing aircraft the engine control uses airspeed as a defacto air/ground indication (using something like 120 knots or Mach 0.2, with hysteresis, for the threshold).

If all the sensors are functioning normally, sure - but you have to design for the possibility that they won't be. Prior to this accident, an apparent IAS of less than 60kts would likely have been considered far more likely to be a sensor failure than an actual occurrence (as tdracer alludes to above). So, no, can't necessarily agree.

Aside from the fact that there's nothing to suggest this in the slightest on the CVR.

The majority of the contents of the "Red OEB" you say should have been published in your linked post were already covered in the UAS procedure included as part of the report (Annexe 06):
http://www.bea.aero/docspa/2009/f-cp...nexe.06.en.pdf

What difference would the OEB have made (AFAIK a "Red" OEB would have required an AD - something which AF would probably have pushed back on)?

yes, the disagreement is for compliance of the stall warning

More over, FBW algorithm does not meet the Federal Aviation Regulations Part 25 for static longitudinal stability, Therefore, for this reason, I strongly believe that the awareness of the crew with respect to the stabilizer position is vital, as well the active sidestick that provides awareness for out of trim and the mushy feeling at low speed or stall.

The simulation for hands off is highly speculative. Yes, it used the winds that the aircraft encountered (apparently) BUT the simulation results in an aircraft in a ~ 10 degree right bank on average which will have the effect of circling the aircraft back toward the storm and in any case, on a different path than AF447 took to get where it ended up.

To properly run the hands off scenario, about the best one can do is to do a long series of simulations with random turbulence injected to see where the most probable result lies. Maybe there was a fortunate circumstance in the data used to create the simulation and in reality the spiral dive would dominate the results. One thing you can hang your hat on is that the resultant flight path in Fig 64 is only a speculative path that starts with closely similar winds aloft and diverges from what would have been encountered had the hands free course been taken.

Dozy's statement that the AOA vanes cannot measure below 60 knots is not strictly correct in that it is not the vanes that are the limitation, but the down stream electronics that are processing the signal. Az33ab provided that information several times. Apparently that same box is also used on other non-AB aircraft so the problem is broader in scope than just Airbus.

With regard to Roberts lack of assertiveness, just how long did he have after being summoned back to the cockpit? Perhaps we are reading too much into his words when he said he had he had grabbed a little bit of sleep. Perhaps he had awakened out of a deep sleep and didn't really trust himself yet.
One of the things that used to scare me, (but there was nothing to be done about it) was sleeping in the cockpit while strapped in on 5 minute alert on the flight deck of an aircraft carrier. When the alert sounded, you knew that the catapult would be firing you off the deck within 5 minutes. I wasn't sure I would be up to the task but the flight schedule didn't give you sufficient opportunity to sleep otherwise. Perhaps crew members need a certain amount of time to come up to speed after they have been sleeping. Did AF have a clear cut procedure that spelled out how long must be given before putting a sleeping pilot back in control. Think of the Mangalore B-737 accident. The Captain had been sleeping in his seat for over 1.5 hours , and was awakened just in time to do the approach which he butchered and caused a high speed overrun accident.
Sleep is one of those things that is necessary but needs careful management because it has such a strong effect on human performance if mis-managed.

Hi,

Dozy
Now that all (by all I mean the entire world!) know that it is possible that pilots themselves can put a aircraft in a situation resulting a airspeed at 60 knots or even under (and with all censors working fine .. except the speed censors for a limited time) what Airbus (or regulators) will change regarding stall alarm .. as all we know that history repeats itself even in the world of aviation
A Chinese proverb says
For know your future look back :)

Machinbird
Of course but what about the "Stall Alarm" ?

Machinbird
Hand off :)
So when on a flightdeck .. begin the music (a concerto!) of alarm of all kind (like it was on the AF447) the answer is hand off ?
With insight for this particular case.. maybe yes ...
In reality .. certainly not !

@Machinbird

I tend to disagree when you suggest the hands off calculation is highly speculative.
The excellent match between DFDR and the hands on calculation shows that the wind/gust/control combination was accurately measured, and from there to a hands off state is a simple subtraction of the response to the control applied.
If AI can't calculate that accurately then you won't have any approved simulators.

The hands off simulation demonstrates two points within the initial first minute of the upset:

The pitch excursion was caused by Bonins initial pitch input
The roll excursion was worsened in frequency by Bonins attempt to level the wings.

While the pitch excursion only manifested itself for Bonin in an increased pitch indication and a steady climb rate (if he noticed those), the roll excursion was changing from left to right (like wing rocking) despite the inputs Bonin made.

That's Machinbird's point, which i share. Bonin was obsessed in geting the roll under control, causing PIO by his inputs in roll direct, and thus not gave much attention to the pitch excursion.

Pitch Versus Roll inputs.

I fly 319/320 s and have a couple of years on 340 s. During manual flight whilst Pilot not flying I've noticed some pilots inducing roll whilst intending to pitch the aircraft and vice versa. Why?

I started checking their control inputs during the control checks on the ground and every time their roll inputs also induced pitch inputs ie ailerons full left and there would be some up elevator, ailerons full right and there would be some down elevator. Once I brought it to their attention and they adjusted their hand wrist positions and tried again (calibrated their senses) so that they could make "pure pitch" and "pure roll" inputs things went a lot better during manual flight.

It would be interesting to see what the flying pilots last manually flown approaches looked like in respect of pitch and roll inputs.

For non Airbus pilots - your seat armrest position is critical so that your inputs are correct, if the armrest is forgotten up accurate inputs to the side stick are virtually impossible as you are making inputs with your arm instead of your wrist. If the armrest is down but not setup for you then it's really hard as well.

groundfloor

An excellent observation, which very plausibly might have a bearing on this incident. Pilots swap positions and/or don't bother to adjust the chair properly. Aircraft on autopilot and no expectation of having to take manual control before the next changeover. Easy to visualise this happening.

You are right, it is at 2:11:37, on the way down, not at about 2:10 as I had remembered. Shame on me for trusting a journalist.

Hi Owain,
I am not commenting on the accuracy of the measurements implied. I am commenting on using those measurements in a situation where you are computing the effects on a theoretical aircraft whose flight path diverges from the known flight path.

If the the aircraft averages ~10 degrees wing down for the duration of the simulation, then it will be flying through a different part of a turbulent air mass, and the assumptions used to develop the effect on the aircraft will diverge from what would have happened in reality as time increases.

I think everyone would be better served by a Monte Carlo simulation of the possibilities so that we could better understand the aircraft's natural tendencies and the factors required to make it diverge substantially from those natural tendencies.

Actually his inputs on the departure up to the point where A/P was engaged should be available on the DFDR record, but that was not released in the accident report.

Going back to grity's stick movement chart.http://home.comcast.net/~shademaker/StickMoves.png

The first point I would like to make is that the initial stick move which begins at 7 seconds is not just lateral but is instead diagonal to the left and aft. Sort of a wrist curl leading to a further finger push to the left. This would be too early in the event to be making a conscious decision to climb the aircraft as part of a procedure. He must have been in reaction mode, not a planning mode.



At that point in time, all Bonin knew is that the autopilot had dropped out and that the aircraft needed a roll correction to the left. The reason for the aft stick could be explained as simultaneously trying to pick up the nose to regain the indicated 300 or so feet lost when the airspeeds were rejected, but in actuality, that probably is not the reason!

Consider this. If Bonin is a stick pulse correction type pilot, why is he maintaining the stick almost exclusively in the range of 4 to 8 degrees aft stick while making mostly large (pulsing) lateral corrections?

This suggests that his inner tension was being reflected as an inadvertent aft stick pressure. (Never mind, Dozy, if it takes a fair amount of force to do this, we are talking about a guy who is really on edge already and has just fallen into an unfamiliar flight condition) The adrenaline is kicking in.

Then finally at 15.9 seconds and at 17.2 seconds, he begins making nose down pulses while traversing the stick to the right. Finally! A pitch motion that seems in character with his assumed style of flying. Does that prove the almost constant aft stick position was inadvertent. No. But it sure does suggest it.

This is why I would greatly like to see the DFDR traces from the period just after the takeoff to further characterize his style. How can we get access to the initial manual flight portion of the DFDR record? Who do we write to? Is BEA free to release it or is it now up to the court?

@Machinbird


[If the the aircraft averages ~10 degrees wing down for the duration of the simulation, then it will be flying through a different part of a turbulent air mass, and the assumptions used to develop the effect on the aircraft will diverge from what would have happened in reality as time increases.]


In that of course you are entirely correct, although the major difference I think would come from the different winds at different altitudes. I do think though that there is enough meat in the simulation to show that the aircraft, left to itself, would have stayed safe, which is why, I think, the simulation was attempted.

Not in the strictest sense. In Normal Law, the aircraft has neutral longitudinal stability. Outside of Normal Law, the EFCS is configured to provide a form of longitudinal stability in concert with low energy warnings.
http://easa.europa.eu/system/files/d...Airbus_340.pdf
http://www.caa.govt.nz/aircraft/Type..._A320_A321.pdf
http://www.caa.co.uk/aandocsindex/22733/22733000000.pdf

There were special dispensations based on certification tests, which all regulators (including the FAA) approved.

There's a nice summary of the Airbus EFCS here: http://www.davi.ws/avionics/TheAvion...ook_Cap_12.pdf

Remember that the trim did not move of its own volition - it moved because the pilot input was commanding it to move. In fact, had Robert looked to his right during the minute the trim was rolling back in response to Bonin's sidestick, he may not have been able to see the latter's sidestick, but he'd definitely have been able to see the trim wheel moving. There is a trim position indicator on the wheel which would have told them their trim position had they looked.

That's one possibility, as is Franzl's suggestion regarding 'tunnel vision' on roll - but as always I'd urge caution on terms of reading too much into things. The fact is that we cannot know for certain what was going through his head, and that fact is as immutable as it is frustrating.

Again, it's possible - but as I said before though, his explicit reference to being "at maxi nose-up for some time" implies otherwise.

So what we're left with includes these possibilities (please add any I've either forgotten or don't know):
If inadvertent:

• He may have had his seat/armrest positioned badly, and induced a pitch component to the input
• He may have been "tensing up" from adrenaline with the same response

If deliberate:

• He may have been trying to follow the intermittent FDs
• He may have not heard and/or realised the consequences of Robert's "Alternate Law" callout, and assumed the hard protections were still there
• He may have fixated on the risk of excessive speed or overspeed from the outset, and been trying to mitigate that risk by using pitch to slow the aircraft

My personal opinion, for what it's worth, is that the last point (i.e that it was intentional and he was fixating on excess/overspeed risk) is the most plausible - though again, I should add the caveat that it's an educated guess and certainly not a done deal. So why do I think it most likely?

1. The "crazy speed" comment, followed by his attempt to deploy speedbrakes, is the most obvious indication that he's concerned about overspeed
2. This happens about a minute and a half into the sequence, but if you look at his comments prior to this, there's a distinct impression that he's been concerned about overspeed for some time ("We don't have impression of speed", "TOGA", "I'm in TOGA eh")
3. He's been sounding nervous about transiting the weather and potential turbulence since before Capt. Dubois went to rest - IIRC standard procedure in turbulence is to reduce thrust and slow down to reduce risk of airframe stress
4. He's likely aware that the THR LK function has been disabled with the TLs in CLB, which goes contrary to the principle of reducing thrust and slowing down
5. Thrust is then set to TOGA, which goes further contrary to that practice
6. He's a glider pilot, so how do you reduce speed? Pitch up.
7. Possibly due to concentrating on damping the roll, he seems to be unaware of the climb he began with the pitch up, and the stall regime begins to creep up just as he gets the roll under control
8. The SW sounds, but he's still in the "overspeed" mindset (similar to the case of the Birgenair 301 Captain), and either does not hear or disregards it
9. The stall condition becomes fully developed and the aircraft begins to descend. When the descent becomes established, Bonin's stick soon becomes slammed against the backstop for almost a minute
10. Nevertheless, the aircraft does not climb - and furthermore, the roll control is lost again
11. This lack of control response is indicative of stall, but similar unusual control responses can also be indicative of overspeed
12. If Bonin did not notice the extent of the pre-stall climb (which he does not mention on the CVR), but he's aware that they've been at higher than normal thrust settings for nearly two minutes (which he refers to twice on the CVR) - he's already set up his mental model with an expectation of overspeed

From this point on, the lack of cohesion on the flight deck becomes terminal. Bonin clearly thinks they're in overspeed, but Robert, in choosing to wait for the Captain, is second-guessing his own SA by the time he returns. Neither Robert nor Dubois offer an alternative explanation for the situation to Bonin, so in the back of his mind he may still be thinking "overspeed" and reacting accordingly.

This is all supposition on my part, but it seems like a fairly logical progression.

@Winnerhofer - there is no useful "car" analogy to that situation. ABS works by using sensors to detect zero wheel rotation when braking is applied at any speed.

I'm not a pilot and this could be a load of rubbish, but perhaps the control laws play a part as well. You're taught on 'traditional' aircraft which require back-presure (pitch) to maintain altitude when rolling. Maybe this sub-conciously transfers over to the Airbus?

I'd have thought that type conversion training would take care of that tendency. More to the point, if I recall my Chippy days correctly you only need apply backpressure when rolling into a turn. I don't think it should be necessary just for levelling the wings.

Dozy,
Remember that whatever Bonin was doing, it was logical to him to be doing that at that time. He was not a stupid person. You don't make it into a cockpit if you are stupid. (foolish is different:}). The problem is that our hind sight bias blinds us to understanding these perfectly logical steps that Bonin took.

The art of hand flying an aircraft has certain elements to it that are common across a wide range of aircraft. Sometimes by looking in great detail at the problems an accident pilot faced, we can begin to understand why, at the detail level, he did what he did. This can be the key to understanding the larger context. Is it a perfect technique? No, of course not, but when your analysis of what was done begins to make sense, then you have to be getting close to what must have happened.

Please do not trot out that over-repeated phrase of Bonin's that he had been at maximum nose up for some time. The flight conditions had changed considerably from when he first took contol and he must have made 200 to 500 small decisions about handling details of his control problems before he made that statement. To try to apply that statement to the beginning of the manual control period is reeeeaaaally a long stretch. You can just about see when he implemented that decision, and it was much later from what I can see.

DozyWannabe, interesting suppositions about the back pressure reasons

However, I would not stick with only one possibility

1. initial climb was deliberate, as stated in CVR, his intention was to climb over the weather, but in the same time he had difficulties in controlling the roll, he over-controlled, because of surprise effect and direct law for roll, at high speed. The travel of sidestick in roll is larger compared to pitch direction, therefore by applying large movements on lateral he might applied more back pressure than intended

2. He followed the FD. At 2:10:50, stall alarm goes off, but aircraft was still in climb for next 20 seconds, Bonin pitch command looks erratically, mostly NU input, but if graph is correlated with FD order, it seems he was actually chasing the horizontal line (Final report, figure 28 correlated with figure 69)

3. Inadvertent pull, at 2:11:30 roll command is at max left, but the aircraft continued to roll towards right. He was fighting with roll control, for next 10 seconds, slowly and inadvertently, the sidestick moved from 9 o'clock position to 7 o'clock (dead stop for both roll&pitch)
Bonin might lost the reference of sidestick fwd-aft and left-right. He exits from 7 o'clock corner directly in the opposite corner full right-ND, the opposite combined stop. Then he might re-position his hand, but already was too late... the irreparable damage for THS position was done.

4. overspeed fear - I would just add the aerodynamic noise combined with misleading stall alarm, Bonin might believed that stall warning comes on because the airflow is disrupted when aircraft is approaching the sound barrier

Dozy
This is off topic my apologies for that. I would like to hear about Airbus elevator integrator function from you. Thanks.

No, they'll be internal designations used within Airbus for certain configuration types. The FCTM does mention that in some Alternate modes, roll will be direct, and either some or all "soft" protections will be missing.

@vilas - I'm not the person to ask about that really, but I'll try to find out. What specifically did you want to know?

Dozy
I have an article that explains it as a circuit in FBW flight control. I have some idea of its function but it say terms like "feed forward gain" and response error over time. As I understand it moves the control first till auto trim catches up. I thought you could give better explanation.

@vilas


Could you post a URL for the article?

Therefore I strongly suggest you read again the CVR ...
The difference between the crash and a crew who knows what's going on and how to deal with the situation more elegantly ...
http://www.pprune.org/7450265-post576.html

Hi,

Tragic animation indeed .... show more than all graphics and curves !

Winnerhofer, Thank you! I heard about this simulation:ok:

Indeed, I'm amazed how fast the time elapsed. We zoom in graphics, but actually, in reality, in about 90 seconds (at 1:30 in video) the THS is near max NU - there, they were already doomed. More than first half of this period of time, Bonin learned to fly the plane at high altitude, he was absorbed by roll control.
As I read somewhere (sorry I don`t remember the article, please correct me or confirm), for both PFDs of simulation, the inputs are from captain's DFDR data, we will never know what Bonin saw on his display.
We can see better from his point of view if hide the imagine of stalled plane (i.e. a notepad window) and try to ignore THS and AOA indications.

By the way, if aircraft has been equipped with those instruments, AF447 would still fly today.

Edit:
An interesting result for combination of simulation video with sound of the reconstruction in link below, start at time 3:24
https://www.youtube.com/watch?v=dKT3dd_ko8E#t=204

I watched them in parallel, then I realize that my post #649 makes a lot of sense.

Not necessarily - if the sim experiments are anything to go by, then there was at least a minute after the THS hit the nose-up stop in which full nose-down could have remedied things.

@CONF - I see nothing that relates to any reset of the system. Where do you see that happening?

DozyWannabe,
Please revise posts #528 and #528, page 27

A theoretical assumption.

In the animation video
at 2h:11m:55s the pitch is -10°, AOA is 38°
at 2h:12m:08s the pitch is -10°, AOA is 41°
at 2h:12m:52s the pitch is - 8°, AOA is 36°

The decrease in pitch did not do that much in decreasing the AOA.

Now take your guess how far the nose has to be stuffed down to reduce the AOA to below stall AOA, how long it will take, and how much time and altitude a cautious recovery to level flight will chew up without risking secondary stall.

In hindsight with the FDR data and with this animation we know how high the AOA really was, the crew did not and therefore did not react in an apropriate way.

A successful stall recovery after 2h:12m without the knowledge part of the flying community gained from AF44 is out of my imagination.

Recoverable ?
 

My own A330 simulator trials of recovery after the stab trim was full nose up and the stall fully developed was that a prolonged nose down input did help—but only initially. However, as the angle of attack reduced and the speed increased, apparently the full nose up stab was more than the elevator could overcome and the airplane pitched up regardless of the nose-down stick position.

It's not clear if the autopitch trim was operational with questionable airspeed inputs, but despite high bank angles in an attempt to keep the nose low, recovery was not achieved until I reduced the stab trim manually. Once trim was reduced manually, pitch control resumed and recovery was possible.

I cover this in more detail in my book "Understanding Air France 447", including what would have been necessary to recover from each point in the scenario. Essentially, the less skilled they were getting in to the stall, the smarter they had to be to get out of it. As we all know, had Bonin simply attempted to maintain a normal 2.5–3° cruise pitch attitude for 40 seconds (the total pitot tube incapacitation time), they would have survived just like the other crews that encountered the same phenomenon and made it OK.

The appalling thing is that the stall warning was going on for over 50 consecutive seconds (plus significant aerodynamic buffet), and the only thing done to recover from it was to apply TOGA power (which at that altitude gives very little additional power over normal cruise setting and zero additional power over climb thrust). I attribute this to training stall recoveries only at low altitude with an emphasis on "minimal altitude loss." This amounts to applying TOGA thrust and reducing the pitch only slightly—what AF447's crew did. But when the airplane was falling at 10–20 thousand feet per minute about the only thing Bonin could think of was pulling back to make the airplane stop descending. For that is where his training of sticking a low-time pilot in the seat and tell him to just follow the flight director did all 228 a great injustice.

The PRIMs have AOA inputs. With NCD AOA info, do the PRIMs still work?:confused:
We have had discussions about this before but I no longer remember the outcome.

Elevator Control
 

Actually the Elevators each have four computer control possibilities and two hydraulic drive possibilities:
http://understandingaf447.com/images...torcontrol.JPG

Control priority for each elevator and associated hydraulic system for each respective actuator is as follows:
Left Elevator:
PRIM 1: green
PRIM 2: blue
SEC 1: green
SEC 2: blue

Right Elevator
PRIM 1: green
PRIM 2: yellow
SEC 1: green
SEC 2: yellow

Stab trim is driven by blue and yellow hydraulic driven actuators (usually simultaneously), If one is out, then the other can drive it independently.
Hydraulic power to the two motors can be controlled by any one of three electric motors or mechanically through cables from the pitch trim wheels. The three electric motors are each controlled by a different PRIM.

This is a fascinating accident indeed. So many levels of wrong in such a short period of time.

What I fail to comprehend is how a trained pilot can completely disregard the information "nose up input" and "spinning altimeter" and "STALL STALL". I read some posts ago that maybe Bonin was afraid of an overspeed situation. While that is a serious concern I can not see it was in any way applicable here.

Could someone please enlighten me as to why Bonin might have thought it was an overspeed? I really don't get it. He should have been aware of the stall buffet waaaay before starting at Air France.

-deleted stuff-

Mods: Feel free to put this post in the bin.

First I'm cautious concerning the extent of reality of present flight sims concerning stall behaviour and reaction of the sim on flight control inputs in this untested flight regime.

But looking from a logical point, why should the THS trim start running nose down right away after applying SS nose down?

The position of the SS commands a loadfactor (g) demand, not a pitch demand. With SS neutral the value is known to be 1 g. SS Nose down demands less than 1 g, SS nose up demands more than 1 g. At low speeds the command is a pitch rate change. AFAIK we still do not know, what the preset rates for those changes are per unit SS deflection, and how the speed changes the preset gains. In case of lost speeds, what value of speed is used by the FBW system to transfer a SS command to the appropriate elevator deflection? And does it change again when the speeds are valid again? Was the FBW system using low speed gains during the stall, high speed gains or preset gains, did the SS stick command a loadfactor or a pitchrate change during stall, or was it a mix with changing gains?

Looking at the FDR and the simulation video i would assume the result was more loadfactor than pitch rate driven. Look at the g values during the stall, due to the increasing sinkrate the value was less than one g most of the time, despite the full nose up elevators and despite the nose up driving THS trim. Both inputs could not arrest the descent and thus could not deliver 1 g or more with full deflection.

SS nose down would command a value of less than one g, or if low speed gains would be used a pitchrate change to nose down. I am pretty sure that the system is set up very sensible for nose down inputs to not spill coffee and bisquits all over the place during normal operation, and it would not know that the aircraft is stalled and therefore a quick change is necessary. As the loadfactor was already below 1 g most of the time, small elevator deflection to less than full nose up elevator would be sufficient to decrease the loadfactor within the allowed gains and values. That's what happened when the SS was kept forward and the elevators went from full nose up to about 1/2 nose up. The THS trim would only react with a Nose down travel to remove a prolonged nose down elevator position, which never happened. It would happen in the end if the SS is held down long enough, but imho that time was very quickly running out.

To expedite the process of reducing the AOA in the available time would only be to use manual nose down THS trim, thus avoiding the comfort gains of the FBW system. How cautious this has to be done in order not to overstress the airframe in the low g or even negative g region i dont't know.