AF 447 Thread No. 12 [Archive] - Page 3

G0ULI

1st Oct 2014, 11:35

DozyWannabe
100% agree about flight deck commonality. I realised I forget to mention that aspect after posting. Never the less, it makes any redesign even more expensive because it has to be applied across more aircraft types.

RetiredF4
I agree that Boeing will apply lessons learned from Airbus' experience to arrive at a better system. Once any system has been proved to grant a commercial advantage, all manufacturers jump on the bandwagon. There is no doubt that sidesticks and fly by wire offer a huge reduction in mechanical complexity by avoiding the need for multiple control cable and hydraulic pipe runs to the cockpit. Problems occur when the controls are operated in a way that the designers never envisaged and instruments fail to display information because the readings are outside predicted design parameters.

Commercial aviation is very safe and ultimately any further safety improvements will need to be justified in commercial terms. It all comes down to the value placed on a human life, and it is surprising low, generally between £5,000 and £50,000 sterling per fatality. The real cost to the individuals and their bereaved families is of course incalculable.

Cool Guys

1st Oct 2014, 11:36

PJ2

Cool Guys, re, "I really think the designers of this system could of been a bit kinder to the pilots."

Well, in what way?

Maybe the design could have less things for the Pilot to think about at the point of degradation to Alt law. When Alt law is entered the pilot has to resolve the issue that caused the law degradation and he also has to change his control input method (as confirmed by Vilas in post 585).

A similar thing could be said about the unconnected side sticks. I understand after 1000s of hours flying in normal law you get used to the controls in the accompanying level of work load but what about at the point of law degradation when the workload can increase considerably? Could the tactile feedback be beneficial at this point? Is there even a slight chance this extra information could have helped Robert understand what was happening?

CONF iture

1st Oct 2014, 20:25

there are numerous clues to the condition of the aircraft still present
1- None of those clues truly reveals how flight controls are manipulated by the PF
2- Airbus suppressing one clue is detrimental to the situation awareness

Two crew members, even 3 in this case, worked on their own with different mental representations of the situation. The Airbus concept or an obstacle to an otherwise natural tool for CRM optimization.

We have more examples of control columns in the full-aft position than we do sidesticks when loss-of-control or a full-stall has occurred.
If the control columns were fully aft it was a known fact by all on the flight deck, AF447 had not that luxury, to the point that the PM had to tell to all he had been full aft for a while ...

Airbus concept contributory as it deprived the crew from that wonderful conventional way to gather information which participated to the confusion prevailing on board.

jcjeant

1st Oct 2014, 21:10

Hi,

Airbus concept contributory as it deprived the crew from that wonderful conventional way to gather information which participated to the confusion prevailing on board.
I agree

DozyWannabe

2nd Oct 2014, 01:41

@CONF, jcj - I know how you feel about the subject, I think we all know how you feel about the subject. But it doesn't make you right, and conversely it doesn't make people who think or feel differently about the subject right either.

At the end of the day we have to take the facts as we have them and make our own calls - personally I don't think there's any point in going round the houses with this particular argument again.

PuraVidaTransport

2nd Oct 2014, 02:49

What if the Egypt 767 would have been an A330? Who would have had control? What would the outcome have been??

It is obvious in AF447, having the yoke in his lap for 3 minutes would have given the PNF and the Captain (when he came back to the cockpit) a visual clue as to what was going on. Instead, after not really knowing what Bonin was doing for three minutes, Bonin finally told the rest of the crew he'd had the stick full back for a while and the realization they were stalled hit the Captain like a ton of bricks. What if, when he walked in, he saw the yoke in the laps of both pilots?? Quite a different outcome I'd bet.

I mean come on...you walk into a cockpit of an airliner that should be at 35K+ feet and you see the yolk in the laps of the pilots? You would instantly know something was very wrong. If I am wrong, please let me know when a pilot would have the control stick full back in cruise flight at 35K+ feet...

What amazes me about the BEA report is this very important point wasn't even discussed and sure wasn't made a point of failure in the cockpit CRM. To me, that smells of collusion between the BEA and Airbus. Many pilots on this forum agree it is a problem but BEA glossed right over it. Boeing felt it was important enough to justify the added weight and complexity and I agree with them.

Why would you intentionally leave a hole in the cheese?? Save a little weight, make the cockpits common?? Doesn't sound like a good enough reason to me.

tdracer

2nd Oct 2014, 03:19

I'm not going to get further into the connected yoke vs. side stick debate - I'm obviously biased (for some strange reason I think the Boeing system is better :O ). But something else keeps coming back to me.
As an engineer, the idea that you could pull back full, at any flight condition (but especially at cruise), and hold it there for more than a handful of seconds (never mind minutes) without stalling the airplane defies physics (unless you're talking a fast jet or stunt plane, which would pull a loop). So I'm left with two options:
1) Bonin honestly thought he couldn't stall an A330, or
2) Bonin lacked the most fundamental understanding of how airplanes work
Both come back to training.:ugh:

jcjeant

2nd Oct 2014, 03:56

I know how you feel about the subjectAnd I know how you feel about the subject :)
Sidestick : work as per design (pilot don't see or feel the position of the opposite one .. as per design)
Pitot tube : work as per design (freezes with ice .. as per design)
ECAM : Work as per design (not indicate a defect on pitot tubes when this happen ... as per design)
Stall alarm : work as per design (stop warning of stall even when the plane is stalled .. as per design)
So .. we can remove sidestik .. Pitot tube ECAM and stall alarm behavior as contributors to this accident .. as all work as per design
What stay to analyse ? :ooh:

vilas

2nd Oct 2014, 04:32

There it goes again the circle continues. This is what I meant. The subject has been examined thread bear. Boeing is not going to replace the yoke nor Airbus is not going to duplicate the side stick motion. All technical and human engineering aspects have been exhausted. Only thing left is the way pilots individually feel about the issue. That is not going to change. Dry fish stinks to high heavens yet many people consider it a flavour.

john_tullamarine

2nd Oct 2014, 04:42

One could, as an alternative, not read the thread were it to cause one offence ?

The specific control device is only a part of the discussion .. although, as you suggest, the sidestick is in the game to stay regardless of what individual folk think and prefer.

mm43

2nd Oct 2014, 04:48

@jcjeant, What stay to analyse ?How about the dog to warn the pilots that they are now in charge, where due reliance on situational awareness, good CRM, and their supposed knowledge of the basic laws of physics could be expected to see them (and the dog) enjoy another meal when safely back on terra firma. ;)

vilas

2nd Oct 2014, 05:17

JT
Make no mistake this thread has given me great details about Airbus FBW which even the most experienced pilots do not lay their hands on. I am just against reviving an issue that is already studied in all aspects that too with same objections. If some one has a new aspect by all means it is more than welcome.

john_tullamarine

2nd Oct 2014, 05:49

No contest.

I, for one, not having any direct AB exposure, have learned heaps from the whole saga as discussed on Tech Log. Don't claim to understand it all but I know a lot more than I did before ..

PJ2

2nd Oct 2014, 07:16

A variation on what may be a familiar flight safety approach to some here is quoted in Beyond Aviation Human Factors, (by Dan Maurino, Jim Reason, Neil Johnston & Bob Lee, 1995), is what was called the substitution test. As far as I can recall, (not far, these days), the question has not been asked on the thread.

It is a common one when doing various tests within a Just Culture, but I think it is particularly relevant here when we're trying to sort out ways of examining cockpit behaviours, ergonomics and human factors. What it helps do in normal practise of airline work is place issues succinctly before those who must manage a Just Culture on a day-by-day basis and handle events which their airline's safety and data programs present, some of them serious. They are examining the "incidents" before they occur, so to speak and this is one way to sort out which way to focus when fixing a problem that is emerging in the data.

So the context is a bit different here I know, but not that different that the question can't reasonably be asked. And it may also help some put on new glasses to see flight safety work and these programs in a new way even if in this case the accident has occurred.

The point is to consider, think and imagine a bit further than focussing too closely on this or that isolated theory, and such a question helps move one off top-dead-center, so to speak.

If someone else who had the same qualifications on the airplane and similar experience ran into the same circumstances (which weren't that unusual for the area), the question asked is, "In the light of existing knowledge and how events unfolded sequentially, is it probable that this new individual would have behaved any differently?"

thf

2nd Oct 2014, 08:06

It is obvious in AF447, having the yoke in his lap for 3 minutes would have given the PNF and the Captain (when he came back to the cockpit) a visual clue as to what was going on.

There is before the stall and in the stall.

In the stall: No one of the three uttered any word which would indicate he realized that they were stalled, despite the many visual clues present. So, it is pure speculation. If you don't know that you are stalled, does it matter what you do whith the sidestick or yoke?

Before the stall: The biggest puzzle, in my opinion, is Robert. He did notice that Bonin was behaving erratically. But he didn't follow up on that thoroughly enough. Why not? Langewiesche has the idea that, when Bonin took away his control immediately after Robert took over, Robert didn't notice this and wondered why his sidestick didn't work. Maybe that is a clue: Did he think his machine was uncontrollable even before it really was? If you want to question unconnected sidesticks, I think that would be the moment.

DozyWannabe

2nd Oct 2014, 13:27

...you see the yolk in the laps of the pilots?

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.

Lonewolf_50

2nd Oct 2014, 14:04

thf:
Before the stall: The biggest puzzle, in my opinion, is Robert. He did notice that Bonin was behaving erratically. But he didn't follow up on that thoroughly enough. Why not? Langewiesche has the idea that, when Bonin took away his control immediately after Robert took over, Robert didn't notice this and wondered why his sidestick didn't work. Maybe that is a clue: Did he think his machine was uncontrollable even before it really was? If you want to question unconnected sidesticks, I think that would be the moment.
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.

DozyWannabe

2nd Oct 2014, 20:14

@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/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.

Penny for anyone's thoughts?

jcjeant

2nd Oct 2014, 22:47

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 airspeedAt 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 ...

CONF iture

2nd Oct 2014, 22:49

Before the stall: The biggest puzzle, in my opinion, is Robert. He did notice that Bonin was behaving erratically. But he didn't follow up on that thoroughly enough. Why not? Langewiesche has the idea that, when Bonin took away his control immediately after Robert took over, Robert didn't notice this and wondered why his sidestick didn't work. Maybe that is a clue: Did he think his machine was uncontrollable even before it really was? If you want to question unconnected sidesticks, I think that would be the moment.
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.

It is a common one when doing various tests within a Just Culture, but I think it is particularly relevant here when we're trying to sort out ways of examining cockpit behaviours, ergonomics and human factors. What it helps do in normal practise of airline work is place issues succinctly before those who must manage a Just Culture on a day-by-day basis and handle events which their airline's safety and data programs present, some of them serious. They are examining the "incidents" before they occur, so to speak and this is one way to sort out which way to focus when fixing a problem that is emerging in the data.
Airbus missed the opportunity to apply that Just Culture :
http://www.pprune.org/7450265-post576.html

tdracer

2nd Oct 2014, 23:10

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 ..
I don't catch the logic of this one !

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).

DozyWannabe

2nd Oct 2014, 23:15

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 ?
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.

he possibly lost trust in the FCS integrity so asked Dubois to switch off or reset some FCCs.
Aside from the fact that there's nothing to suggest this in the slightest on the CVR.

Airbus missed the opportunity to apply that Just Culture :
http://www.pprune.org/7450265-post576.html
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-cp090601.en/pdf/annexe.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)?

_Phoenix_

3rd Oct 2014, 00:36

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)

yes, the disagreement is for compliance of the stall warning

§ 25.207 Stall warning
(c) Once initiated, stall warning must continue until the angle of attack is reduced to approximately that at which stall warning began

More over, FBW algorithm does not meet the Federal Aviation Regulations Part 25 for static longitudinal stability, which requires a pull force to achieve and maintain a steady state speed decrease relative to the trim speed and vice versa Also, after having released the stick, the speed has to return to the trim speed.

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.

Machinbird

3rd Oct 2014, 01:57

Penny for anyone's thoughts? 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.

jcjeant

3rd Oct 2014, 01:58

Hi,

Dozy
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.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
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 signalOf course but what about the "Stall Alarm" ?

Machinbird
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.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 !

Owain Glyndwr

3rd Oct 2014, 06:18

@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.

RetiredF4

3rd Oct 2014, 07:33

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.

groundfloor

3rd Oct 2014, 12:36

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.

G0ULI

3rd Oct 2014, 12:57

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.

thf

3rd Oct 2014, 14:38

Not too sure about that as the airplane was already stalled when Robert took control.

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.

Machinbird

3rd Oct 2014, 16:23

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. 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.

Machinbird

3rd Oct 2014, 17:01

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.
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?

Owain Glyndwr

3rd Oct 2014, 18:16

@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.

DozyWannabe

3rd Oct 2014, 19:39

More over, FBW algorithm does not meet the Federal Aviation Regulations Part 25 for static longitudinal stability
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/dfu/Annex-EASA-TCDS-A.015_Airbus_340.pdf
http://www.caa.govt.nz/aircraft/Type_Acceptance_Reps/Airbus_A318_A319_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/TheAvionicsHandbook_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.

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.
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.

But it sure does suggest [inadvertent back pressure].
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?

The "crazy speed" comment, followed by his attempt to deploy speedbrakes, is the most obvious indication that he's concerned about overspeed
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")
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
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
Thrust is then set to TOGA, which goes further contrary to that practice
He's a glider pilot, so how do you reduce speed? Pitch up.
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
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
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
Nevertheless, the aircraft does not climb - and furthermore, the roll control is lost again
This lack of control response is indicative of stall, but similar unusual control responses can also be indicative of overspeed
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.

ManUtd1999

3rd Oct 2014, 21:38

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.

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?

DozyWannabe

3rd Oct 2014, 22:12

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.

Machinbird

4th Oct 2014, 02:53

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.

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.

_Phoenix_

4th Oct 2014, 03:57

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

vilas

4th Oct 2014, 04:49

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

DozyWannabe

4th Oct 2014, 13:37

The BEA lexically invented these submodes.
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?

vilas

4th Oct 2014, 15:05

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.

Owain Glyndwr

4th Oct 2014, 17:16

@vilas

Could you post a URL for the article?

CONF iture

4th Oct 2014, 21:28

Aside from the fact that there's nothing to suggest this in the slightest on the CVR.
Therefore I strongly suggest you read again the CVR ...
What difference would the OEB have made
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

jcjeant

4th Oct 2014, 22:06

Hi,

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

_Phoenix_

4th Oct 2014, 23:19

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

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

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.

DozyWannabe

5th Oct 2014, 04:50

the THS is near max NU - there, they were already doomed.
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?

_Phoenix_

5th Oct 2014, 12:05

DozyWannabe,

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.

Please revise posts #528 and #528, page 27

Bill Palmer... As the airplane's flight control system continued to attempt to maintain the commanded g-load—as the airplane started to sink—the pitch trim ran to full nose-up. From that point on, recovery may have been impossible unless the crew had the awareness to reduce that manually. I've tried that in an A330 simulator. Even with full nose-down pitch command, as the airspeed built up in the recovery the nose-up trim had too much influence to overcome and the airplane would pitch up despite any action on the sidestick. Trying to decipher the last moment that the airplane could have been recovered by a pilot that had all his wits about him is futile.
The experts in the article are right. Pilots need to routinely practice hand flying with all the automation off.

RetiredF4

5th Oct 2014, 15:39

Dozywannabe
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.

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.

Bpalmer

5th Oct 2014, 17:05

Machinbird

5th Oct 2014, 20:31

In case of 3 PRIM failure the elevator is controlled by SEC 1.
Electrical control of THS is lost. THS actuation is still available through manual pitch trim
wheel control.
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.

Bpalmer

5th Oct 2014, 20:49

Actually the Elevators each have four computer control possibilities and two hydraulic drive possibilities:
http://understandingaf447.com/images/A330elevatorcontrol.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.

MrSnuggles

5th Oct 2014, 21:16

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.

MrSnuggles

5th Oct 2014, 21:59

-deleted stuff-

MrSnuggles

5th Oct 2014, 22:32

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

RetiredF4

6th Oct 2014, 07:15

BPalmer
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.

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.

OK465

6th Oct 2014, 15:28

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 (?)

Excellent post and insight into FBW, RetiredF4.

The report states that in ALT2B, pitch gains are fixed for 330 KIAS. Don't have the page ref at my fingertips, but it's in there and it's the only reference I've ever seen to this.

From the simulations I've seen, it appears that the pitch gains are permanently fixed for 330 KIAS regardless of whether the speeds become valid again or not, this as a result of ALT 2B 'latching', and the fact that 'validity' is nothing more than two ADRs being within 25 KIAS.

Though NO two ADRs within 25 KIAS starts a 10 second countdown for display of the ADR Disagree ECAM message....ALT2B with the associated fixed gains 'latches' within a couple of seconds.

Once two ADRs are back within 25 KIAS (doesn't have to be the correct speed), the countdown is terminated and reset (and the FDs return, and no ECAM message if less than 10 seconds). But the gains remain fixed for 330 KIAS. There's a simple way to check this monitoring elevator deflection on the SD Flight Control page.

I'm completely out of the business now, but with respect to all this discussion of simulator post stall behavior and subsequent recovery in a simulator, the last communication I read from a noted sim manufacturer stated that beyond a relatively early point in the sequence, as opposed to 'flying', one is simply operating a high dollar video game.

Bpalmer

6th Oct 2014, 17:10

RetiredF4First 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.
Me too. But it seemed reasonable.
The pitch response with manual trim is fairly gentle as one can only move the trim wheel about 90° at a time in the practical sense, before having to move your hand back and grip the trim wheel again (not like the Boeings with the fold out hand crank)

Winnerhofer
Disable AutoTrim in all Laws bar Normal as this is will force crew to be in the loop.
Actually that doesn't put the crew any more in the loop, as the SS remains a gload/pitch rate demand input, and gives no information to the crew as to the relationship between the stab and the elevator (like a conventionally controlled airplane way out of trim would) Neutral SS still would command essentially 1g—even though it may take full elevator to do so (if the stab is way off ).
A good example of this is a fault where autotrim fails, but manual trim is still functional. In this case the airplane appears to fly just fine, but the crew (directed by the non-normal procedure) must view the flight control page on the Systems Display-SD) and trim for neutral elevator. When this is happening, there is no feel change in the airplane, but as the stab position changes the elevator deflection necessary to maintain the commanded pitch response (i.e., 1g) changes accordingly. Obviously as the airplane slows for approach, the crew must continue this procedure, for if the didn't they run the risk of "running out of elevator" near landing as the elevator may (unbeknownst to the crew) be near full up just to maintain the approach trajectory (1g)and not have any excess for the flare.
In alternate law, as the airplane approaches stall speed, the pitch law incorporates "stabilities",which when you get right down to it is changing to direct law in pitch and allowing the natural pitch stability of the airplane to become evident. The speed at which this occurs is not indicated. The trim stops—if it didn't then the stability would not be evident!
The unfortunate part of this is (for AF447 type situations) is that indicated airspeed is required to make that change over (not just AOA). So, one must assume that in the case of invalid airspeed the SS remained a g/rate demand input.

MrSnuggles
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.

It shows Bonin's state of unawareness of the state of the airplane. The pitch had been up, they'd climbed nearly 3000 feet, the stall warning was sounding for almost a minute, Robert had been telling him to "go back down", yet he had apparently confused the significant stall buffetting with Mach buffet- as he remarked that he thought they had "some crazy speed" and at one point deployed the speedbrakes though Robert told him right away not to. The supercritical airfoil makes it easier and more efficient to go M.84, but harder and therefore less of a hazard to get to M 1.0 - without the Mach tuck threat of 707 days.

DozyWannabe

6th Oct 2014, 17:46

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.

Right - our experiment - linked here:
http://www.pprune.org/tech-log/460625-af-447-thread-no-6-a-85.html#post6793521

So, I was talking about some research this weekend. I got in touch with an old Aero Engineering pal of mine from Uni and he managed to wangle us some spare sim time at his facility in the wee hours inbetween training sessions. What we had was an A320 sim rather than an A330, which comes with some key differences - the most obvious of which is the lack of Alternate 2, the nearest equivalent being Alternate without speed stability, and a different underlying architecture past a certain point.

Due to time constraints we could only run each experiment once, preceded by some familiarisation time handling the sim manually in Normal Law, albeit at low level, following the FDs around basic turns and level changes.

The first experiment involved setting the conditions to night IMC with CBs in the vicinity, having set the autoflight to take us to 35,000ft and hold us there. We had a friend of his who is a TRE sitting in the LHS to provide guidance and monitor what we were doing. He then failed the ADCs, leading to autopilot disconnect and a drop to Alternate (without speed stability) and we tried to follow through and maintain a 15 degree pitch angle. Things we noted:
I'd suspected it would involve considerable effort to hold the sidestick there for a significant amount of time, but I was genuinely surprised at just how much.
The zoom climb occurred exactly the way we expected
The Alternate Law (no speed stability) on the A320 seems to have a hard trim limit of 3 degrees nose up
It was definitely possible to hold the aircraft in the stall with 3 degrees of nose-up trim and full back stick, but it required effort
The aircraft wanted to nose down and recover itself, and with about 10 degrees of nose-down maintained with the sidestick at the moment we passed about 30,000ft, we managed to effect a recovery with the speed coming back up to a point where we could level out safely at about 20-25,000ft judging by the standby altimeter.

The second experiment was the same as the first, but as my pal had noted, the A320 has a hard limit of 3 degrees NU trim available via autotrim in the secondary Alternate Law. We tried again, this time winding in full nose-up trim manually just prior to the point of stall. This time:
The aircraft seemed more willing to hold pitch with the trim at full-up, but to hold it at 15 degrees still required considerable effort
We had to add a touch of rudder (on the TRE's advice) to control the roll.
Despite full nose-up trim, we elected to start a recovery as we came down through about 35,000ft this time, just to see if it was possible using sidestick only
Following the same 10 degree nose-down sidestick demand as before, the trim rolled forward with the sidestick demand, returning to around neutral within about 5-8 seconds, and we came out of the stall as before.

Based on this, as far as the A320 is concerned at least, recovery is possible using autotrim via sidestick only even when the trim has been manually wound fully nose-up. Given more time we'd have liked to see what happened attempting recovery at lower altitudes, but the general take-away seems to be that with sufficient forward sidestick demand it is possible to recover from stall even with trim forced to where it's not supposed to be.

Of course, these were purely technical experiments. Not only was this a sim session with only pride at risk, but we all knew what was coming and had a pretty good idea of how to get out of it. This does not and cannot compare to a situation where you're trying to get out of it for real, especially with the added handicap of limited manual flying experience.

Whether the A330 behaves differently I don't know, but I've called in my favours for now and am eternally grateful to the people who made it possible. Someone else is going to have to take that on.

As far as I know, a UAS condition similar to AF447 - i.e. equivalent to double simultaneous ADR fail with the third following - is *not* enough to take the aircraft out of Alternate Law and into Direct, which means that autotrim would stay on.

In your experiment, did you fail all 3 ADRs at the same time? This would put the aircraft into Direct Law and fail the autotrim - which might explain why your trim wheel didn't roll forward with sustained nose-down stick in the way ours did.

@Winnerhofer - they're pilots, not dogs. You can't force behaviour just by making things more difficult for them. The THS position would have been a moot point if the PF hadn't made significantly inappropriate pitch inputs for that phase of flight.

DozyWannabe

6th Oct 2014, 19:03

@OK465 - Really? Fair enough. I'd swear I remember something like that in my reading though... I know you lose Yaw Damping with triple ADR failure. I guess I'm just trying to figure out why the trim rolled forward in our experiments and not in Brian's.

EDIT : Ah - Failing all three IRs get you Direct Law, not the ADRs.

jcjeant

6th Oct 2014, 19:04

Dozy
The THS position would have been a moot point if the PF hadn't made significantly inappropriate pitch inputs for that phase of flight. The main thing is how to achieve that a pilot does not make an inappropriate action in certain phases of flight
The only solution other than use his brain is physically preventing a way to do this action (as is sometimes done in the industry in general .. restricted movement of limbs or safety guards .. barriers) which is virtually impossible in aviation
On the other hand one can also ask the onboard artificial intelligence to play the role of safety guard
For example .. why embedded intelligence leaves THS do what he wants (following a bad pilot action) that is to say foster the rise ... while she know that the airplane is near its maximum allowable alltitude (from some parameters ... weight .. engine power altimeter .. air temperature .. etc. ..) and when that maximum height is reached ... she keeps in position THS to continue climb

DozyWannabe

6th Oct 2014, 20:19

@jcj: The system is not intended to be of the level of complexity required to determine "bad" inputs from "good" ones. The whole ethos of the Alternate Law system is to give the pilot as much control as possible while keeping as many systems online as it can. The A320 appears to have a limit on trim travel in Alternate Law, but - possibly as a result of press/professional backlash at maintaining authority, the A330's THS system gives the pilot complete authority at all times. One can't have it both ways.

@Winnerhofer: Perpignan isn't really comparable - in that case the AoA vanes failed due to water ingress from improper cleaning methods, which froze at altitude. The acceptance pilots also broke from the specified procedure when testing the safety features. In the case of AF447, every component in a technical sense (bar the problematic pitot tubes) was working correctly.

RetiredF4

6th Oct 2014, 20:48

OK465, thank you for providing some answers to my questions.

OK465
From the simulations I've seen, it appears that the pitch gains are permanently fixed for 330 KIAS regardless of whether the speeds become valid again or not,

If the fixed gains are for 330 KIAS and the jet is in a low speed situation, then the resulting flight control deflections would be minimal in relation to that if the gains would be set for the actual slower speed. Did i get that right? In consequence, the aircraft would maintain its agility in the roll channel (roll direct) and would be slow to react on pitch inputs. In the sequence of events the preset gains for 330 KIAs were close to the initial speed, thus pitch command sensibility was close to mormal, and then decresed with decreasing airspeed.

OK465
I'm completely out of the business now, but with respect to all this discussion of simulator post stall behavior and subsequent recovery in a simulator, the last communication I read from a noted sim manufacturer stated that beyond a relatively early point in the sequence, as opposed to 'flying', one is simply operating a high dollar video game.

That part made my day! Hope, Dozy reads it as well.

DozyWannabe

6th Oct 2014, 21:00

That part [sim stall behaviour not necessarily following the real aircraft] made my day! Hope, Dozy reads it as well.
I knew that already. The only aspect we were checking in our sim experiment was the behaviour of the autotrim system in the alternate/stall scenario with the stick held forward.

gums

6th Oct 2014, 23:20

Good to see the old denizens of this thread at it again. And I welcome Mssr Palmer ( wish he was here years ago).

- Good posts, Retired. And I hope the bus drivers that took issue with me years ago about gee command versus pitch command note your post and Palmer's.

Viper "standby gains" were maybe a consideration by the 'bus folks in their design stage. We had a similar speed as the 'bus with gear up and something like 180 knots CAS with gear handle down.

- the gee command in the 'bus has a pitch attitude compensation, right? So neutral stick might be commanding other than 1 gee ( Nz), unlike our system ( simple and many less degraded modes and sub-modes). So maybe this function was in play, as the nose was fairly high all the way down. Thots Mssr Palmer?

- I agree with Winner about a simple degredation sequence. I would guess most 'bus drivers do not know all the stuff that continues and changes to stuff until they get to "direct" laws.

- I agree that the overspeed concern is not warranted. The jet design seems very good, witness the stall with no violent wing rock or shaking or.... So I feel it could easily get up to 0.9 or a bit above without a flutter problem or even aileron reversal ( spoilers a big help in that regime).

jcjeant

7th Oct 2014, 00:06

@jcj: The system is not intended to be of the level of complexity required to determine "bad" inputs from "good" onesCause my impaired technical faculties .. can you explain me the complexity for a system like one aboard Airbus aircraft for understand ( or know) that the aircraft have reached his maximum ceiling altitude (for some reasons) and for automaticaly forbid anything ( EG trying climbing more) that will put the aircraft and the people in a very dangerous situation
What is the disadvantage (or danger versus the existing system ... THS stay full climb) of establishing such an automatic ?
Is a automatism could decide the fate of the aircraft before the laws of physic ( Newton law is one) "take command" ?

vilas

7th Oct 2014, 03:13

I find some doubts being expressed on auto trim function during unstalling the aircraft. AF 447 remained in alternate2 and never went into direct law so auto trim will function. In Perpignan crash after the crew dropped the speed(purposely for test) it changed to direct law as they lowered the gear and since AoA were frozen they gave erroneous inputs it had trimmed full up. This would need manual forward trim to unstall.During stall exercise with gear down in direct law you do not trim below Vls for the same reason.As they were only at 4000ft and were under lot of pressure they didn't figure that out. In AF447 the stick input to reduce the pitch was never sustained for any length of time. His actions were more like he believed in displayed vertical speed.He would push forward for whatever reason but watching the VS would pull back. So the stabilizer would stay up. He seems to have taken stall recovery action as taught that time with emphasis on minimum loss of height, rather than unreliable speed procedure. It is apparent he never looked at the PFD otherwise he would have lowered the nose at least on the horizon and let it be there for a while.

Volume

7th Oct 2014, 07:12

otherwise he would have lowered the nose at least on the horizon and let it be there for a while.The nose was down 10° at least twice, so well below the horizon, but with a flight path angle below -25° (obviously the limit of the FDR) that still gives an AoA beyond stall. Unfortunately many pilots do not understand, that AoA and Pitch can differ more than 30° in a stall situation...

PJ2

7th Oct 2014, 18:27

Hello Mr Palmer;
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. With the stick held in the full-ND position, did the THS never begin to move towards normal, (from -13 to around +2 or so)? It should have, so that's a bit odd that it didn't move.

In my own sim trials the elevators were sufficient to initially achieve about a 10-deg ND pitch attitude, and the THS always began returning to normal when the stick was held full-ND. I agree that recovery was probably not possible unless/until the THS returned to a normal setting.

A manual setting of the THS was always available to the AF447 crew but it would have returned to the NU position once the manual rotation of the wheel stopped - by that time, they may have got the wing unstalled. In our trials it took about 20,000ft, about 45 seconds.

DozyWannabe

7th Oct 2014, 21:56

In my own sim trials the elevators were sufficient to initially achieve about a 10-deg ND pitch attitude, and the THS always began returning to normal when the stick was held full-ND.
Yup, that's what we saw too. I said it took about 5 to 8 seconds for the trim wheel to roll back to neutral after the stick was pushed ND (initially fully-forward, then maintaining about 10deg ND). The variance is based on the fact that I was counting the seconds rather than using a stopwatch (my hands being somewhat full at the time).

A manual setting of the THS was always available to the AF447 crew but it would have returned to the NU position once the manual rotation of the wheel stopped
As far as I know, there's nothing stopping a crew member from holding the wheel in position once rolled forward (and thus negating autotrim) until recovered.

Correct me if I'm wrong, but I think trim logic is set by stick demand, attitude and time, so as long as the stick was held forward while the trim wheel was rolled forward, I don't think you'd see a significant return to NU.

PJ2

7th Oct 2014, 23:48

Dozy;

In the small amount of research I did a while back I had the impression that so long as the airplane wasn't in Direct Law, and the auto-trim system was functioning normally, one could set trim using the wheel because the system senses a manual input and releases the brake on the hydraulic motor driving the THS. Once that motion was no longer sensed, to me it was logical that the system would return to normal and try to satisfy whatever orders were being received by other systems. Some have said that order is the 1g order and so we may have seen a return to the -13deg setting, or, if the stick had been full-forward for sufficient time, it would have returned enough to provide elevator authority sufficient to reduce the AoA and unstall the wing.

All theory of course...

In direct law we know it is a different story; that's why the red ECAM warning.

The design seems to boil down to the engineers imagining and expecting this scenario. Hindsight being what it is, we can now say something but I'll bet anyone here that no one imagined such a scenario to the point where the design would have been changed - certainly not the certification people.

Just my personal opinion but to me that is entirely crystal ball territory. One of course cannot imagine and account for everything and still get the machine off the ground.

RetiredF4

8th Oct 2014, 06:43

DozyWannabe
Correct me if I'm wrong, but I think trim logic is set by stick demand, attitude and time, so as long as the stick was held forward while the trim wheel was rolled forward, I don't think you'd see a significant return to NU.

That logik would not work.
THS trim afaik is not driven by SS, but by elevator position.
The SS demands a load factor change or a loadfactor of 1 g if stick is in neutral position. The Computers transfer this demand to an elevator deflection. The THS trim then moves to zero out this elevator deflection to restore the full elevator authority in both nose up and nose down direction. As ever there will be limits when this action starts, but i have these not handy.

It would not be logical that the trim would start to move nose down when the elevator deflection is still in the nose up region, as was the case in AF447 for those moments when the crew made nose down inputs. Due to the increasing sinkrate the loadfactor was most times already below 1 g, therefore a small elevator change from full nose up elevator was enough to further decrease the loadfactor.

I really would like to hear from AB what kind of input / maneuver would have been necessary to get this aircraft safely out of this well developped stall. Then we would have hard facts instead of reliance on some individual sim experiments, which might behave differently and lead to wrong conclusions. AB must have done those tests as well, where are the results?

PJ2

8th Oct 2014, 07:25

RetiredF4;

I understand your caution on sim experiments. However, I don't think we can dismiss simulator experience and performance entirely, out-of-hand.

To focus on the item under discussion, the THS does not change its behaviour in a stall; it is responding to orders as before. I think it is reasonable to assume, (until proven otherwise by AB, an AMM or a true authority on the A330), that the simulator replicates the THS behaviour accurately.

On the sink-rate 'g', I think it was very close to 1g all the way down - isn't that the definition of "falling"? Other than slight changes in pitch slightly increasing or decreasing 'g', why would it be "most times below 1g"?

RetiredF4

8th Oct 2014, 09:10

Hello PJ2,
yes i'm very cautious to the sim experiments, and especially due to the facts that such experiments or their results are not known from BEA or AB or from the main players in Simulator software or applications. There should be reason that they are not confident in the validity of any results after the stall was beyond its initial state.

PJ2
To focus on the item under discussion, the THS does not change its behaviour in a stall; it is responding to orders as before. I think it is reasonable to assume, (until proven otherwise by AB, an AMM or a true authority on the A330), that the simulator replicates the THS behaviour accurately.

I have no doubt that the simulator will react on SS inputs like the real jet, but only in those regions where the input datas are known and programmed into the data base. If those important values are not known and therefore are not in the database, then some default values would be used that the system is not going to tilt. Let me make an example concerning AOA (There would be more to it for sure):). We know, that AF447 encountered AOA up to 50°, and that there are no real air datas available for such extreme AOAs and the behaviour of the airframe under such conditions. As nobody expected such kind of extreme AOAs would be possible for more than few seconds in an air transport catagory aircraft and no legal regulation requests for sampling data for such situations, the default value for the sim software in order not to crash the sim would be some default value. I have my optimistic day today, so let us assume the default would be something like highest tested and confirmed stall value + 10°, let's again assume that value would then be an AOA of 20°.
If that would be the case, and i do not know if it is, then you would start your sim experiment stall recovery always with the same default data of 20°AOA and not from actual AOA. That is the typical "garbage in, garbage out" case.

OK465
I'm completely out of the business now, but with respect to all this discussion of simulator post stall behavior and subsequent recovery in a simulator, the last communication I read from a noted sim manufacturer stated that beyond a relatively early point in the sequence, as opposed to 'flying', one is simply operating a high dollar video game.

For me that sums it up pretty well.

PJ2
On the sink-rate 'g', I think it was very close to 1g all the way down - isn't that the definition of "falling"? Other than slight changes in pitch slightly increasing or decreasing 'g', why would it be "most times below 1g"?

Good point, i should have been more specific.

From 2:10:27 until 02:10:50 (zoom phase) and from 02:11:03 until 2:12:00 the loadfactor was below 1 g. The timeframe with the positive g (02:10:50 until 02:11:03) kicked AF447 into the stall by some noseup stick and TOGA thrust. At 02:12:00 the jet was falling through FL 310 with an AOA of 45° After that point the loadfactor varied around 1 g.

The sinkrate was increasing until passing FL 310. In normal flight that would be longitudonal acceleration, with high stall AOA it is sensed as vertical acceleration. If my math is right, then with AOA 30° sinus is 0,5 and with AOA 60° sinus is 0,866. Therefore increase of descent rate and increase of AOA both contributed to the loadfactor below 1g.

I hope that clears up my wrong statement "all the way down".

PJ2

8th Oct 2014, 15:56

Hello RetiredF4;

We're on the same page I think, in fact I recall arguing against simulation of the stall for diagnostic purposes in the original threads for the very reasons described - there's no data and it is "here be dragons" land...as you say, GIGO, (however, I think that is changing).

That said, I considered that the behaviour of the THS in response to orders from the stick, (which in turn was ordering the elevators) would not be affected by the stall and that is the only point I'm making.

The THS would still respond "normally" to inputs on the stick, in other words, regardless of AoA, rates of descent, etc., etc. Also, it would still respond to manual input using the two wheels on the pedestal.

Yes, your remarks regarding 1g clear that up, thank you.

PJ2

8th Oct 2014, 20:36

OK465;

Hear you...can't claim either "record" - did the exercise almost two years ago and that was that. There are sim guys out there whose company operates A330s who've done this tons of times because they're now teaching it and they're realizing the value of hand-flying in automated transports - a couple of good things to come out of all this.

As for the rest, so long as the major factors which lie behind this accident are recognized, understood and the teaching has changed, then I believe the argued points are less critical. Beyond such understanding and change, it's our passengers who should "win".

CONF iture

8th Oct 2014, 21:04

I have seen THS action vary from run to run on a given day
Could it be dependant on the fact that Abnormal Attitude Law is active or not, probably in relation to the 30 deg value for the AoA ?

Mr Optimistic

8th Oct 2014, 21:28

Option 1: don't disturb anything.
Option 2: in that fully developed stall tell the Captain what happened, put the nose to 40 degrees down and throttles to idle and fly from there.

Mr Optimistic

8th Oct 2014, 21:41

Any chance of a summary in English for us linguistically challenged anglos?

Clandestino

8th Oct 2014, 22:28

Side stick controls meant the cockpit could be made smaller allowing a bit more room for the passenger cabin and an extra row of seats.That would explain why 320's cockpit is smaller than 737's except for the fact it isn't.

But if the pilot is incapacitated, in a spiral dive 4g+, with thumb on priority switch.....then you are discussing something which has never happened, is unlikely to happen and has no relevance to AF447.

In an aircraft with traditional controls, Robert would say "My airplane", then he would notice the colum moving in his lap. Probably he would say "listen Bonin, trust me I know what is wrong, give me the controls!"
In aircraft with traditional instruments and controls there is procedure for pitch + power flying when all air data gets shot up. Position of controls never comes into play. It's the same with A330 and was the same at the time of AF447. Surprise, surprise.

Why the designers could get away without adding haptic feedback is a mystery and dual input is a hilarious stupidity.The system is certified and very well proven, both in everyday use and in unreliable airspeed situations. There might be some hilarious stupidity around but not within FCS designers' circles.

Boing is sticking to the old layout with tactile feedback. To assume they did it due to personal oppinion of their engineers or their pilots falls short considerably.Yup, it ignores marketing.

The Airbus concept or an obstacle to an otherwise natural tool for CRM optimization.That would explain why other 40-something 330/40 crews (including AF ones) faced with loss of airspeed indication in cruise, AP trip off and degradation to ALT law ended up similarly to AF447 except for the fact they did not.

Bonin lacked the most fundamental understanding of how airplanes workBoth pilots lacked it... at 4:00 AM in cruise. If you could travel in time an tell them (or any other pilot that never put down his last flight in the logbook) about the way they would meet their demise, I'm pretty sure the least reaction you would get is offense at the suggestion they might be so dumb to do that. Discussing aerodynamics and performance here is pretty easy exercise. Remembering any of it at 4AM when scared witless is not quite so.

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 liesAnd there I was thinking that the proper simulation is about getting inputs as close as the real ones. Real turbulence was pretty well recorded so this is:

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....untrue and massively ignorant at the best.

the roll excursion was changing from left to right (like wing rocking) despite the inputs Bonin made. That would explain why the roll wasn't following pılot's inputs except for the fact it did.

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.Horrible PIO! Convergent and with maximum pre-stall amplitude of 11 degrees! That would explain why Bonin didn't change the pitch except for the fact he was steadily decreasing it from 12 to 6 degrees ANU as soon as he got roll under control but pulled to 17.9 when stall warning fired again.

The art of hand flying an aircraft has certain elements to it that are common across a wide range of aircraft. The first and foremost thing about IFR flying is attitude! Who gives a PPRuNe about how much one displaces stick or yoke with what force! One uses it as much as needed to get desired attitude - which can be easily read out from big EADIs on PFD.

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. How did THS behave in real world FBW Airbus stall incidents and accidents?

If the fixed gains are for 330 KIAS and the jet is in a low speed situation, then the resulting flight control deflections would be minimal in relation to that if the gains would be set for the actual slower speed. Did i get that right?Nope. See here:

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. As RetiredF4 has correctly observed, Airbus FBW gains are related to G/pitch change, not controls deflection.

the gee command in the 'bus has a pitch attitude compensation, right?Not just that, up to some bank (33 IIRC) it has roll compensation too! So how does this super-duper-complicated-magic work? By programming FBW to keep stable vertical flightpath. What is commonly and wrongly referred to 1.2 G demand is actually 0.2 G demand superimposed on current normal acceleration. So how does average Joe the pilot cope with super-duper-complicated Airbus FBW and its reconfiguration laws? Well that's the beauty of it; he does not need to know anything about it to fly. No matter what law one is in, stick forward brings the nose down, stick back brings it up, stick left brings left wing down and right stick brings it up - unless one has stalled his Aırbus, that is.

AB must have done those tests as well, where are the results?It has never done it nor there is any need for doing them.

DozyWannabe

9th Oct 2014, 15:14

Hey all - sorry, been a bit unwell the last few days.

Anyhoo - I found A33Zab's post from back in the fourth thread, which I hope can shed some light on the THS question. Link here:
http://www.pprune.org/tech-log/454653-af-447-thread-no-4-a-17.html#post6532375

It's worth having a look at the whole thing, but the interesting bit that I recall is this:
From study material and answer to Machinbird's question:

"An override mechanism, which is installed in the PTA (Pitch Trim Actuator),
makes sure that the mechanical control through the trim wheels cancels the electrical control.
When a manual command is made with the trim wheels, the override
mechanism gives priority over the electrical command from the FCPCs.
It mechanically disconnects the PTA output from the mechanical input (via
electro-magnetic clutch) and also operates the overriding detection
switches which in turn signal the FCPC's to stop any electrical command
from the FCPC's."

So, near as I understand it the PTA override mechanism detects mechanical resistance to the electrical motion and disengages the electrical system via a clutch mechanism. I would imagine that both holding the wheel (static resistance) and rolling the wheel (dynamic resistance) will disengage the electrical system until the resistance goes away - i.e. the wheel is released.

As to the other question - i.e. what the FCPC is doing with the various inputs (elevator position, stick input etc.) while the trim is being controlled manually - either it continues computing where it wants the THS to be while the wheel is under manual control - in which case the electrical system will attempt to re-acquire that on release, or it does not - and simply starts calculating from the point the wheel is released. In either case it will not attempt to roll it back to the last known position, and in the former case it will not roll it all the way NU unless the sidestick has been commanding that position while the wheel has been under manual control.

DozyWannabe

9th Oct 2014, 17:23

@Winnerhofer - appreciate the enthusiasm, but it might be worth checking to see if the subject of AoA gauges has been brought up in the previous threads before posting it again (for the record, it has)...

roulishollandais

9th Oct 2014, 17:54

Thus, human error is reconfirmed as the prime cause of the accident because the pilots failed to identify and properly manage a problem already known to exist in such conditionsErrors, mistakes, faults, or success have all an origin, a reason, a cause.
John Tullamarine's excellent document about human factor, or part of the USAF KC-135R report refering to human factor (excellent too) are going to the deep of human factor definition, very far from the pseudo-philosophical and pseudo-scientific readings i.e. that quotation and other VF!

Lonewolf_50

9th Oct 2014, 20:46

Clandestino:
Good to see you back in the scrum. :ok:

Just a thought here ...
Remembering any of it at 4AM when scared witless is not quite so. Based on the limited evidence available to us, which is some of the CVR transcript, I'll suggest that neither Bonin nor Robert ever got to the "frightened" stage. They remained in the "what is going on?" stage, though Robert seems to have been more aware of the aircraft's flight condition than Bonin, coupled with frustration and confusion.
Captain DuBois may have been indicating fear with his "it's not possible" remark, but he just as likely to have been in a different mode of problem solving as he tried to get a grip on what those two had done in his absence ... and correct it. His instructions to Bonin on using his rudder to help his roll control strikes me as being in a problem solving mode, not in the "I am scared" mode as he tried to get the situation back to something like normal.

The above considered, we can't be sure since we can't read minds through a CVR, and can't read minds beyond the grave. We'll never know if they were frightened or not. I don't think they ever got to that point.

gums

9th Oct 2014, 23:38

Wrong, Winner. The pitch law is not for an attitude. The attitude resulting from a stick input and then neutral is due to the pitch gee factor that the engineers programmed.

Our primitive Viper law was all AoA limit and gee command. At 45 degrees of pitch, a neutral stick had about 0.707 gee thru your feet, but the jet kept trying for one gee Nz, and you kept getting more nose up attitude and the dreaded THS autotrim. The 'bus corrects for that in "normal" law ( and maybe one of the sub-laws). It also puts in a gee command for pitch when rolling into and continuing a turn.

My opinion is too many protections and "aids" once the primary law is gone. Sheesh. Put a big light up and say "you are in back-up flight control law, and fly stick and rudder!"

We don't need to go to "direct law" willy nilly. But trying to keep all the "protections" until finally in "direct" seems to create confusion for we pilots.

DozyWannabe

9th Oct 2014, 23:57

My opinion is too many protections and "aids" once the primary law is gone. Sheesh. Put a big light up and say "you are in back-up flight control law, and fly stick and rudder!"

That's kind of what it's doing anyway. There are some folks working on translating the second Judicial Experts' Report, particularly with reference to Section 2, which covers the flight tests performed to assess aircraft capability in that scenario:

Alternate law was activated by cutting ADR3 and activating ADR2 which was blocked (double ADR failure). The ALTN2B law triggered when the speed seen by Pitot 2 (via the drainage orifices) passed a certain breakout and the three ADRs became incoherent. This transition to ALTN2B being irreversible the valid speed information on PFD2 required for the rest of the flight was obtained by reactivating ADR3.

2.1.3.1.1 principal tests made and comments
...
2. Hand flying evaluation of flying qualities in ALT2B around 0.81M between 35000 and 38000 ft

Pilot comments: ALTN2B didn't present any major difficulty of piloting. The control of attitude is pictures practically identical to that in normal law. The control in roll seems astonishingly more precise than normal law and the aircraft demonstrates a good and proper stability. When are more aggressive roll inputs are made there is a perception of lateral accelerations which could be interpreted as yaw. In summary, this ALTN2B law is not a factor which could justify a tunnel vision occupying all resources of the pilot.

I didn't see any difference in the longitudinal control; the response to commands is correct; without action on the stick attitude remains stable

Interesting stuff...

DozyWannabe

10th Oct 2014, 01:40

The translation's rough and ready, admittedly - but it gives a reasonable overview for the most part. I think they actually physically blocked one of the pitot tubes before departure.

This was an A330-200 aircraft, and the report makes reference to using it to make certain that any claimed differences between that and the A340 previously tested would be nullified.

Owain Glyndwr

10th Oct 2014, 07:11

I'm afraid Dozy rather jumped the gun there - my unpolished translation was a PV not intended for general consumption - well not yet anyway.

The complete, relevant French version is this: native French speakers feel free to correct my approximations!

2.1.3.1 Vol sur l’A330-243 MSN 1496 F-WWTP, le 10 février 2014 à Toulouse, en partie de nuit.

Configuration particulière avion:

(photo of blocked pitot)

Tube de Pitot no2 bouché et son dégivrage inhibé pour tout le vol

Configuration systèmes:

ATA 27: FCPC P7/M16
ATA 31: FWC T1

La loi ALTN a été activée en coupant l’ADR3 et en activant l’ADR2 qui est boucheé (double panne d’ADR). La loi ALTN2B s’active alors lorsque la vitesse vue par le Pitot 2 (via les orifices de drainage) dépasse un certain seuil et que les 3 ADR deviennent incoherent. Cette transition en ALTN2B étant irreversible, on retrouve des informations de vitesse valable au PFD2 pour le bon déroulement des essaises, en réactivant l’ADR3

2.1.3.1.1. Essais principaux réalisées et commentaries

2. Prise en mains, evaluation des Qualities de Vol en loi ALTN2B, autour de M=0.81, entre 35000 and 38000ft.

Commentaires pilotes: <<La loi de vol ALTN2B ne présente aucune difficulté majeure de pilotage. Le contrôle en assiete est pratiquement identique à celui de la loi normale. Le controle en roulis semble étonnament plus précis qu’en loi normale et l’avion fait preuve d’une bonne stabilité proper. Lorsque des impulsions plus aggressive en roulis sont effectuées, il en résulte une perception d’accélerations laterals pouvant etre interpretées comme des mouvements de lacet. En résumé, cette loi ALTN2B n’est pas un facteur pouvant justifier une <<vision tunnelisée>> accaparant toutes les resources du pilote,>>

<< Je n’ai ressenti aucune difference s’agissant du contrôle longitudinal, la réponse à la demande est correcte; sans action sur le manche, l’assiette reste stable.>>

roulishollandais

10th Oct 2014, 09:10

When […] more aggressive roll inputs are made there is a perception of lateral accelerations which could be interpreted as yaw.If Bonin had that perception we can imagine his trouble : Yaw is heading change, not lateral acceleration perception.
Bonin was discovering that unknown law and that sudden law change and that behaviour dissimetry of the plane in pitch and roll. He was not informed -unlike the pilots of Toulouse's february 2014 flight- before the facts happened and was not a test pilot.
Did anybody found objection in AF447's FDR/CVR?

jcjeant

10th Oct 2014, 09:21

En résumé, cette loi ALTN2B n’est pas un facteur pouvant justifier une <<vision tunnelisée>> accaparant toutes les resources du pilote,>>Exact in the test conditions (the pilots know what will happend .. and they knows the BEA final report and more)
In the reality ... over the sea at night in the AF447 .. the conditions were not the same .......
If you take all the events separately ... it's not so busy workload ...
When you mix all the events in a short lap of time ... this is different .....
If you make a reenactment of the battle of Waterloo (with all the insight) maybe Napoleon will win !

DozyWannabe

10th Oct 2014, 15:50

Bonin was discovering that unknown law and that sudden law change and that behaviour dissimetry of the plane in pitch and roll.
I've pointed this out before, but how could any law change have caused Bonin problems, when he didn't even have any experience of how the aircraft handled at high altitude in Normal Law?

Sounds like making excuses to me...

roulishollandais

11th Oct 2014, 08:58

@DozyWanabee
The situation was lost after :
-1 high altitude stall
-2 wrong pitch-power used
-3 inability to decide action after UAS
-4 Autopilot missing
-5 Captain leaving
-6 Puzzled brain in a complex situation
-7 Crew's Robert/Bonin bad coordination
-8 Bad health/rest before the flight
-9 ITZ
-10 Missing stall test of airliner
-11 etc.
-12 Cadet training

From my experience as airline pilot in a french airline, I would like to point the second and the fourth items. Really I only met people giving no importance to knowledge of some important ref pitch&power, included chief-pilot, instructors, etc. One of our CPL lost his ATPL check after being unable to continue safe MD83 ILS flight after he had to fly with Pitch and Power. It showed a gap of our pilots' team, but nothing was done. It was not only in high altitude. It is then that I revised for my own the page full of numbers and discovered the MacDonnell mistake N2% dicreased from 76 to 66 at 3000 Ft...
It seems the wrong figure existed since 13 years, for 165 airlines... Happily nobody needed it. Perhaps the fact that the need of Pitch&Power seldom happens explains the deny of needing acurate knowledge, despite it is taught in old time french IFR BASICS ...

DozyWannabe

11th Oct 2014, 23:23

@roulis:

Perhaps I should clarify. When I say "making excuses", I don't mean for the crew - I mean making excuses to blame the aircraft and systems.

Of course being handed control via AP disconnect in cruise at night over the ocean and in turbulence is going to be a fairly difficult scenario for the pilot - even more so if that pilot has never been trained in or experienced handling the aircraft manually at that altitude. But that would be true of any aircraft type you care to name - whether the control layout is conventional or not, or whether the systems are electro-hydraulic or FBW (or indeed what control law one is in, in the latter case).

The practice whereby pilots were routinely put into the flight deck in this phase of flight despite neither of them having any experience of manual handling in that scenario absolutely deserves close scrutiny - in real terms, it shouldn't really have been allowed to happen.

What I was getting at was that it doesn't make sense to claim that the change in control law had any effect on the way he handled the aircraft (particularly in roll), or the way in which he perceived the aircraft to be handling - because he had no experience of what it was like normally with which to compare it and thus be "confused". Yes, it was probably frightening and yes it was difficult - but that was because of the scenario in which he found himself, not because of the change in control law.

Does that make sense?

PJ2

12th Oct 2014, 00:50

Dozy;

Re, "Of course being handed control via AP disconnect in cruise at night over the ocean and in turbulence is going to be a fairly difficult scenario for the pilot"

The following actually goes to your point regarding scrutiny, etc...

Regarding being handed the airplane when the autopilot disconnects, no, it is not difficult at all, not even a bit. I've had the autopilot disconnect, (over both oceans...didn't seem to matter) and the first thing one does is leave it alone and do nothing, but (for those who desire to know what "do nothing" means), by all means maintain altitude and keep the airplane stabilized - most of the time it does that on it's own for a half a minute or so which is way more than one needs to assess the situation and get comfortable. Then try to re-engage the AP and if no joy, fly the airplane...tiny, gentle squeezes on the stick or column to correct little divergences.

Hand-flying the aircraft in cruise IS difficult for anyone who hasn't done it or who doesn't have a lot of experience, and therein, as you say, is what needs scrutiny. In fact they shouldn't be in the cockpit but I recognize that I'm growing older and automation, (which I always thought was wonderful) is here to stay. I heartily agree that putting inexperienced (cadets?) people up front needs scrutiny - it's a money thing and is today somehow an acceptable risk).

BTW, "...over the ocean" makes no difference, neither should night-time if one is an instrument pilot; the Airbus handles turbulence well when hand-flown in Normal law, (in fact you don't move the stick at all, really, until the airplane diverges from what one wants), and in Alternate law one is gentle with the airplane as a pilot would be with slightly more sensitive roll and at high altitudes. I have to say I've hand-flown the A330 & A340 in cruise, sometimes for an extended time, (not in RVSM airspace of course) and it's a delight aircraft to fly.

The DC8 was a bit more of a handful in the sense that one was always "working the control column a tiny bit to maintain one's altitude, but it was just another airplane, difference was these aircraft have a lot of mass so they're slower to change, slower to return - one has to wait, then make a change, wait...

They're all very stable and not difficult at all to fly. Flying them has less to do with training than one's experience - you can't "train" everyone to fly...that I know from experience, but if they can fly, then "training" would consist of little hints here and there regarding handling because you'd be expected to be able to fly an airplane. DP Davies was superb in the advice he offered.

I tend to agree with you - an autopilot disconnect for someone without experience would be disconcerting and distracting. I think this is where the rubber meets the road, so to speak, in the way the industry has gone, and its already addressing the problem.

DozyWannabe

12th Oct 2014, 01:31

@PJ2:

We're basically "singing from the same hymn-sheet" here. What I was getting at was the modern condition - that even a pilot with some experience of manual handling at high altitude may initially balk if it hasn't been practiced in a while. A pilot who has no such training or experience has every reason to feel genuinely scared.

WRT "over the ocean/at night" etc. I was referring to the complete lack of outside reference for attitude, which I would imagine is a big deal in the event of an apparent instrument failure because it erodes trust in all the instruments, even those which are working.

Anyways - all good... :ok:

PJ2

12th Oct 2014, 07:20

Not sure it's a "big deal" - it doesn't necessarily "erode trust in all the instruments" [my italics], especially not in those that are working - reason is, if you know they're working it is reasonable and probable that they can be trusted so you use them.

We experienced steadily diverging airspeed indications on a B767, (winter, in cloud, night, in the climb above FL200). We had to decide whether it was the captain's ASI or mine, as mine was getting lower and lower while he was maintaining a steady climb speed. Mine agreed with the steam-standby; the hiss of air noise wasn't normal. I wasn't flying at the moment so I don't know how the airplane felt - he began using the standby and as his ASI increased past the barber pole we waited for the overspeed warning - it never came, but an EICAS message came on regarding the ailerons and a speed limiting function, (I can't recall it now - it was amber). We took a look at the IRS/FMC groundspeed. He gave me control and we finished the flight uneventfully - the ASI returned to normal in warmer air during descent.

No one here should mistake this for a hero story because it isn't - it's what's done very likely hundreds of times a day around the world in commercial transports- not this of course, but certainly something. It isn't thought of as "scary" or "difficult" - it's a problem to solve and with both good training and lots of time in, it usually works out. One should rarely if ever be scared in an airplane when s. happens but deeply respectful of what it may do to one if one provides it with an opening.

When someone would ask how much airline pilots make, the joke was $100,000 a minute but you'll never know which one. Thing is, airlines aren't paying this anymore and now it's showing up, only occasionally so far, but as the cadets move to the left seat and the other seat is a 250hr guy or gal who's never just about killed themselves at least once, they're not up to snuff when things really get difficult.

We live in an age that I call the "illusion of technique" because people who run things at airlines can be buffalo'ed into thinking technique is everything and neither experience nor intuition count for much anymore. I prefer to think of automation as the greatest assistant I've ever had except my First Officer and the two Relief Pilots - the machines are brilliant, but the guys and gals have eyes and got time in the old fashioned way and when their time comes they'll make great captains. I care very much about this profession and I don't like the trends; been writing about them for about twenty five years now - spit in the wind, and I'm a pilot who I loves automation.

Judd

12th Oct 2014, 09:28

I care very much about this profession and I don't like the trends; been writing about them for about twenty five years now - spit in the wind, and I'm a pilot who I loves automation.
I have been an avid reader of aviation safety reports for years. So much can be learned from them and retained for future events. Having also been in the simulator training game also for many years I have discovered that many pilots undergoing type rating training or re-currency lack interest or the motivation to study the various flight safety hand-outs I offered them. These are incident, technical articles and accident reports very much applicable to the type they will be flying.
Understandably these pilots just wanted to get through the course with the minimum of study and hand-outs which were not part of the course for a type rating were seen by many of them as unnecessary. I recall talking to one pilot who told me he felt that old accidents were no help in passing the course and ticking the boxes.

There is no excuse for lazy pilots many of whom are happy to spend hours of their time on social media but who seemingly couldn't give a rats for technical information that should be a part of their professional lives. With the advent of Pprune there is a plethora of excellent information on every facet of incident and accident studies especially through the hundreds of links. Yet I very much doubt that lazy pilots study these reports even though they may be flying the specific aircraft type.

OK, this rant has probably nothing to do with the Air France A330 tragedy but believe me there are pilots out there who couldn't care less about their own professional development as long as their automatic pilot works as advertised.

roulishollandais

12th Oct 2014, 10:31

@DozyWanabee
I used an ellipse of Law of flight change to emphasise the fact that the change of law is a worthful possible situation aswell as the other contexts from my list drifting tothe final minutes.

vilas

12th Oct 2014, 12:40

Generally it is believed that lack of experience is the problem. In this topic of stall alone we have seen that both experienced and inexperienced pilots have not only stalled the aeroplane they have not been able to apply correct recovery procedures. Experience is a very vague word. Mostly we log uneventful thousands of hours and that's how it should be otherwise the technology needs another look. But this innocuous experience does not give any confidence in dealing with abnormal situations. In aviation one does not learn through one's mistakes. So when it happens it is always first time. The confidence comes out of basic flying ability which does not require thousands of hours but sufficient practice depending on individual ability and good knowledge of abnormal procedures. Since we as a specie have no instincts in the air procedures are the only thing which saves the day for us. Everything we do in the air is acquired skill nothing is natural. There are experienced pilots who find it tough to do raw data ILS and there are others who cannot do visual approaches. It is because they never acquired the scan or the judgment. It all starts with simulator training. If not properly trained you cannot do it on line. If the SFO pilots would have tried as practice a visual approach some where else the result may have been same. With autopilot you are not handling the controls but scan is no different than manual flying. In some airlines with seniority pilots reach non judgmental stage where their checks become an exercise in ticking boxes. Nobody tells them anything anymore. Also with financial pressures airlines are reluctant to spend money on training. After all it is a business. Best airline is the one that stays afloat.

PJ2

12th Oct 2014, 15:09

Judd, villas, well said and I think on-topic insofar as we are digging around in human performance aspects of aviation accidents, which AF447 is, (again emphasizing that blame is not a part of this kind of examination). In this there are perhaps some commonalities between this and the Colgan accident at Buffalo, (I know this has been broached previously...just making the connection on "Thread 12").

A technical question regarding the Airbus which may have been answered in the other threads - IIRC there was mention that the stall warning could or should inhibit movement of the THS - I believe there was something in the Perpignan accident report about this. There is lots to think about in such a design - should it do so in Normal Law as well as the two Alternate Laws? However, were it to do so, would it limit elevator authority if it did not move in response to elevator demand as ordered by the stick? Would there be a need in "normal" flight for a THS setting of -13°? ...in Alternate Law?

It is hard to think of such a case at cruise altitudes, but what other considerations might there be that makes it a better idea to place limits on THS movement in certain phases of flight?

These questions will have been thoroughly thought through of course even if some might consider the design puzzling in the hindsight of the accident.

BOAC

12th Oct 2014, 15:34

IIRC there was mention that the stall warning could or should inhibit movement of the THS - hi - missed you around here. Way back I suggested that THS movement should be STOPPED at some suitable angle and require an over-ride to continue trimming, this in the hope that 'automatons' might notice all was not well. I still think it is good idea. The over-ride option would cater for your concerns, I feel? It (the 'wake-up call') might have gone a long way to preventing the Turkish 737 AMS crash.

Owain Glyndwr

12th Oct 2014, 16:07

The Airbus FCOM says, for normal law [1.27.20 p2]

<When angle of attack protection is active, THS is limited between setting at entry in protection and 2 deg nose down (i.e. further nose up trim cannot be applied).>

The question is WTH was this not carried over to Alternate laws??? I believe it is carried over on the A320.

rudderrudderrat

12th Oct 2014, 17:38

Hi Owain,
The question is WTH was this not carried over to Alternate laws??? I believe it is carried over on the A320.
I believe you are correct: FCOM OP-020, Flight Controls, Alternate Law
"At the flight envelope limit, the aircraft is not protected, i.e.:
In high speed, natural aircraft static stability is restored with an overspeed warning
In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G."

Since the aircraft is no longer "protected" in Alt Law, how did the certification process of A330 satisfy:
Section 5. Stability
26. Static Longitudinal Stability and Demonstration of Static Longitudinal Stability -
§§ 25.173 and 25.175. ?
http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2025-7C%20.pdf

Owain Glyndwr

13th Oct 2014, 05:58

Hi rrr,

Since the aircraft is no longer "protected" in Alt Law, how did the certification process of A330 satisfy:
Section 5. Stability
26. Static Longitudinal Stability and Demonstration of Static Longitudinal Stability -
§§ 25.173 and 25.175175. ?
http://www.faa.gov/documentLibrary/m...2025-7C%20.pdf (http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2025-7C%20.pdf) Well of course the document you reference is an AC not a requirement, but the answer to your question I think is that there is a Special Condition for A330/A340 certification against JAR 25.173 and 25.175 (EASA TCD A015 Annex; Special Condition F3):

The aircraft shall be shown to have suitable stability in any condition normally encountered in service, including the effects of atmospheric disturbances.

Interpretative material:

The evaluation of the aeroplane's static longitudinal stability characteristics shall be by flight and simulator tests. Control laws that result in neutral static stability throughout most of operational flight envelope may be accepted in principle subject to:

- adequate speed control without excessive pilot workload

- acceptable high and low speed protection

- provision of adequate cues to the pilot of significant speed excursions beyond VMO/MMO and below take-off and landing scheduled speeds.

The following considerations will be relevant to the evaluation:

- accurate speed control will be particularly relevant in the full range of operating speeds including low speeds (scheduled speeds at take-off and landing with or without engine failed) and high speeds for each configuration including VMO/MMO

- Since conventional relationships between stick forces and control surface displacements do not apply to a manoeuvre demand control system, longitudinal static stability characteristics will need to be determined on the basis of the aeroplane's response to disturbances rather than simply on the basis of stick force versus speed gradients.

- Adequate high or low speed cues may be provided by a strong positive stability gradient and/or alerting system.

- A force gradient of 1 lb for each 6 knots, applied through the side-stick, shall be considered as providing this strong stability

infrequentflyer789

13th Oct 2014, 09:58

Exactly, so the question is does it meet the special conditions for certification.

The BEA had what I thought were some very interesting comments on this in the final report (had me chasing off for references), along with what I thought was a veiled / sarcastic criticism. However, I am reading that from the English, since my French (and knowledge of French diplomacy) isn't good enough to pick up the nuances in the original.

Since then I haven't seen the issue raised anywhere (not sure even on these threads) and notably not in any of the various presentations / articles from those who want to blame-the-plane, many of which have been linked here. Since most of those are in French, I have started to think it is either an artefact of my imagination, or one of translation. Even Winnerhofer's annotated BEA report didn't seem to pick up on it.

So the next question is why did you highlight (bold) the bit of the special condition that you did and not the, er, other bit ?

Owain Glyndwr

13th Oct 2014, 10:57

@infrequently flier

Exactly, so the question is does it meet the special conditions for certification.

Well obviously the certificating authorities (all ten of them together IIRC) thought so!

So the next question is why did you highlight (bold) the bit of the special condition that you did and not the, er, other bit ?

Er - which other bit?
I highlighted the bold bit simply to emphasise that the stick force vs speed characteristics described in the FAA document rrr cited are not relevant to A330 certification

rudderrudderrat

13th Oct 2014, 11:33

Hi Owain,
Thanks for pointing out that you think there is a Special Condition for A330/A340 certification against JAR 25.173 and 25.175 (EASA TCD A015 Annex; Special Condition F3): which explains what the final (report Page 187) was referring to.

"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."

I just wonder why the A330 in ALT Law wasn't designed to have the same positive static stability of the A320.

infrequentflyer789

13th Oct 2014, 12:54

Final moments of Air France Flight 447 revealed | Daily Mail Online (http://www.dailymail.co.uk/news/article-2790768/f-dead-pilot-shouted-air-france-jet-plunged-atlantic-final-moments-doomed-flight-447-two-sleeping-pilots-revealed.html)

Sorry, but no, it's not complete DCVR. Daily Mail is just referring to the Vanity Fair article already linked on this thread. No new information.

G-CPTN

13th Oct 2014, 20:02

Apologies if already posted.

Capt Marc Dubois, 58, was sleeping off a night out with his girlfriend
I do not believe it was fatigue that caused him to leave. It was more like customary behaviour – part of the piloting culture within Air France.
Co-pilot David Robert, 37, was also dozing – leaving just crew ‘baby’ Pierre-Cedric Bonin, 32, at the controls.
If the captain had stayed in position through the inter-tropical convergence zone, it would have delayed his sleep by no more than 15 minutes, and maybe the story would have ended differently.

From:- 'F***, we're dead': Cried Air France pilot minutes before plane crash on flight between Rio de Janeiro and Paris | Metro News (http://metro.co.uk/2014/10/13/f-were-dead-cried-air-france-pilot-minutes-before-plane-crash-4904751/)

Wedge

13th Oct 2014, 20:24

I think that story arises out of this big feature in this month's Vanity Fair magazine.

Interesting stuff.

Should Airplanes Be Flying Themselves? | Vanity Fair (http://www.vanityfair.com/business/2014/10/air-france-flight-447-crash#)

gums

13th Oct 2014, 20:49

I think I get what the "report" was getting at, but I also think it does not apply in direct law.

With gee and pitch rate components of the other laws, the jet is basically "neutral" for speed stability ( no "trimmed" airspeed as we old farts remember). So slowing up does not lower the nose as we were used to. And the converse for application of power regardless of engine mounting - you won't climb to maintain the "trimmed" speed ( actually AoA).

But this is the first I have seen for the jet not having positive static stability. I mean basic aerodynamic stability, unfettered by computers using rate and gee and air data sensors. My trusty Viper was no kidding statically unstable until above 0.9 M. We also did not have the plethera of alternate modes and sub-alternate modes - it was gee and AoA protections only. But like the 'bus, we were neutral WRT speed stability. Sucker would hold the trimmed gee until it reached 27 degrees AoA ( remember, we could trim for a gee).

Need Mssr Palmer here, or someone else to try "direct law" and set the THS, then let go of the stick.

infrequentflyer789

13th Oct 2014, 22:48

@infrequently flier

Well obviously the certificating authorities (all ten of them together IIRC) thought so!

Yes, and that is what the BEA more or less said - the behaviour is not compliant with the regs, but it is ok (implied) because the certification authorities said so, based on special conditions.

I found it slightly odd that they put the onus on the opinion of the certifiers rather than say something more definite like "it is ok because it complies with special condition XY which replaces regulation Z", and it was that that had me going off looking for the actual special conditions when I read it.

Er - which other bit?
I highlighted the bold bit simply to emphasise that the stick force vs speed characteristics described in the FAA document rrr cited are not relevant to A330 certification

My bad - I confess I skipped the detail from rrr's post because my understanding is that anything in that section of the regs is inapplicable because the whole section is replaced by the special condition - unsuprisingly because it is all around positive static longitudinal stability, which the fbw 'bus does not have.

The bit of the special conditions that got my attention was this:

Control laws that result in neutral static stability throughout most of operational flight envelope may be accepted in principle subject to:

- adequate speed control without excessive pilot workload

- acceptable high and low speed protection

ALT2B is, however, neutral stability and without speed protections, is it not ? BEA seems to think so, at least to my reading of 2.2.5 in the report (p186-7 in English pdf). Condensing a bit:

Protections are lost.
...
When there are no protections ... <behaviour> ... judged to be acceptable by the certification authorities by taking into account special conditions and interpretation material material; i.e. that the presence of flight envelope protections makes neutral longitudinal static stability acceptable.

I've substituted "; i.e. that" for ". Indeed" at the end there, because it is one sentence in the original French and I think the intended sense is that they are specifying what the special condition is.

So, essentially, the behaviour of the a/c without protections was accepted by the certification authorities because of the protections. Now I thought that was a rather odd statement and possibly a veiled criticism of said certification authorities, but maybe I am the only one who reads it that way.

jcjeant

13th Oct 2014, 23:03

If it's one thing remind (and this is actually the most important) is that Airbus (or any other manufacturer) had not made for fun to show they can do it .. but for sale
Having known that .. so they will make all this is necessary to achieve that goal even if it is necessary to take steps to adapt the certifications rules to their products (and so for the "derogations")

Gysbreght

14th Oct 2014, 09:19

So, essentially, the behaviour of the a/c without protections was accepted by the certification authorities because of the protections.
No, that is not correct. You have to distinguish normal operation and operation with system failures. Alternate law is a rare failure condition which, by design, does not occur more often than once in 100,000 flight hours. At that level of probability, no airplane is required to meet the flying characteristics requirements of Subpart B. Those requirements, and the special conditions you reference, apply for the airplane systems functioning as designed, without failures.

jcjeant

14th Oct 2014, 11:41

Alternate law is a rare failure condition which, by design, does not occur more often than once in 100,000 flight hours

Those requirements, and the special conditions you reference, apply for the airplane systems functioning as designed, without failures. Seems to me (from the BEA report) that the AF447 was all the way down ( the loss of speed indication was short) a airplane with all systems functioning as designed without failures even in alternate law
Alternate law is not a failure

Owain Glyndwr

14th Oct 2014, 12:19

think I get what the "report" was getting at, but I also think it does not apply in direct law.
Gums, I agree – in direct law the conditions that gave rise to the special condition do not apply so the aircraft has to meet JAR25.173 and 25.175 as written. It is certificated, so it must meet those requirements, but this is not strictly relevant to the present discussion.
I must admit I struggle to get my head around statements like:
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
I think I understood it eventually, but at first it seems counterproductive to apply a nose up command to compensate a speed loss.
But this is the first I have seen for the jet not having positive static stability. I mean basic aerodynamic stability, unfettered by computers using rate and gee and air data sensors
I think the problem in part arises from the labelling of the FAR/JAR paragraph. When “static stability” comes up my mind (and maybe yours gums?) goes to considerations of short period response and return to the trimmed AOA after a disturbance. I don’t think there is any doubt that the ‘bus is stable or strongly stable in this respect in ANY law.
The FAR/JAR wording however relates solely to speed variations seen through stick movements and which involve excitation and damping of the long period (phugoid) dynamic characteristics. But the ‘g’ feedback in normal and alternate laws controls the aircraft to a steady flight path which takes away one degree of freedom and the phugoid disappears to be replaced (in speed stability terms) by a one degree of freedom convergence or divergence depending on where the aircraft sits on the (thrust – drag) curve. The conventional stick/speed relationships then do not apply; hence the SC, which says that:
longitudinal static stability characteristics will need to be determined on the basis of the aeroplane's response to disturbances
Because of compressibility effects the (T-D) profile of a modern airliner in cruise is more like a bathtub than the classic parabola. At the high end of the speed range, where the aircraft is hovering on the edge of drag rise, the response to a speed disturbance will be stable. From there down to the minimum operational speed (say 1.3Vs) the aircraft will be marginally stable. It would be not until one gets below that that instability creeps in.
This might be seen as weasel wording, but given the probability of dropping to ALTN law (most pilots will never see it throughout their career we are told), a marginally stable aircraft which meets the book (just) in normal operating speed range might be considered acceptable even without protections.
Below 1.3Vs the aircraft is speed unstable and this is where the BEA comment to the effect that the aircraft might drift to stall even with zero stick input becomes valid. However, if one puts some real numbers into the equations one finds that in level flight it would take about twenty minutes to decelerate from 1.3Vs down to Vs. Put some mild climb demand into the sums so that the initial thrust deficit is greater and a very different story emerges – that deceleration could take twenty seconds rather than minutes. [My numbers might be challengeable, but I think the principle holds – if you start from a speed yielding nearly neutral stability the initial divergence rate will be very low]
So the ‘hole’ in the certification would appear to be that the static speed stability in a combination of alternate law and flight outside the normal flight operational envelope was not checked. [But note that FAR/JAR 25.175 does not apply to speeds less than 1.3VSR1 so if this philosophy was carried over to the SC there would be no hole].
The point I am trying to make is that an aircraft may be neutrally speed stable in response to stick inputs but might still be speed stable in response to atmospheric disturbances and it is this latter that is used to define whether the requirements are met.
Gysbreght, I agree that according to JAR principles the full handling requirements might not be applicable in a failure case (and jcjeant, ALTN is a consequence of some sort of failure so the probability principle applies) but you cannot abandon the handling requirements altogether, so there must be something there appropriate to the failure probability level. Since there are no specific requirements relating to ALTN, my guess would be that the normal requirements were applied, albeit with some less stringent interpretation. Others may wish to comment on the probity of more relaxed interpretation of the rules at a time when things are getting difficult!
I have some difficulty with the logic of the final BEA sentence in:
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."
He might have been unaware that the aircraft could be driven towards stall without any input from him, but why would he not be aware that maintaining up elevator for a prolonged period would drive the aircraft towards stall?

Gysbreght

14th Oct 2014, 13:55

you cannot abandon the handling requirements altogether, so there must be something there appropriate to the failure probability levelI must admit that I'm not expert on this, but I believe system failures are addressed in FAR/JAR 25.1309. The general principle is that there must be an inverse relationship between the probability of a failure condition and its effect on 'continued safe flight and landing' of the airplane. This implies that an assessment must be made of the ability of the pilot to deal with the effects. The FAA and EASA have both published extensive guidance material on how this principle is to be applied.

Owain Glyndwr

14th Oct 2014, 14:10

@Gysbreght

That is essentially what I am saying - handling qualities must be matched to probability and seriousness of failure consequences

RetiredF4

14th Oct 2014, 14:10

Owain Glyndwer
He might have been unaware that the aircraft could be driven towards stall without any input from him, but why would he not be aware that maintaining up elevator for a prolonged period would drive the aircraft towards stall?

That is a vital question. I think it is a mix of not sufficient knowledge about general aerodynamic matters and missing energy awareness. In all our discussions there surfaced another obvious fact, that the normal documentation does not contribute to the knowledge level. The manuals are comparable to instruction manuals without comunicating the basic knowledge layer behind those instructions.
I do have no knowledge if the quality of the manuals for pilots, instructors and maintenance is part of the certification process, but there should be at least a minimum standard established for those documents and i would wish that this standard is above that one which it seems to be now.

The manuals i was used to in the military were gold compared to the dust of the AB manuals i could get my hands on.

CONF iture

14th Oct 2014, 14:28

He might have been unaware that the aircraft could be driven towards stall without any input from him, but why would he not be aware that maintaining up elevator for a prolonged period would drive the aircraft towards stall?
He is aware of maintaining some back pressure on the stick, information positively known only by him due to the SIDESTICK concept by Airbus.
At no time it is getting tougher for him to maintain back pressure due the auto operation of the THS.
That THS operation has been a main actor in the fatal ending of AF447.

DozyWannabe

14th Oct 2014, 14:41

I have some difficulty with the logic of the final BEA sentence...
They're probably just trying to be thorough - obviously in this case the stall was preceded by distinct NU input on the stick, but they're probably asking for some clarity on what should happen if that isn't the case, and how the special regs conditions deal with that.

Regarding Direct Law, as it essentially bypasses all the rate demands and the automatic trim, would it not be the case that the jet does have longitudinal static stability around the current trim setting, as would any other airliner in that configuration?

That THS operation has been a main actor in the fatal ending of AF447.
You can only reasonably make that claim if there was a distinct and obvious effort to recover from the stall and the THS position prevented it - this wasn't the case. Furthermore, the THS was in that position because the pilot put it there, knowingly or not. Robert might not have been able to see Bonin's SS, but if he'd looked across, he'd definitely have seen the trim wheel rolling backwards.

Owain Glyndwr

14th Oct 2014, 16:07

@RetiredF4
there should be at least a minimum standard established for those documents and i would wish that this standard is above that one which it seems to be nowThere is a problem in that the manuals are not issued to the crew by Airbus.
In that “Counter Experts” report you will find the following (my apologies for leaving it in French, but I don’t want to get into any hassles over mistranslation)

au cours de nos recerches nous avons trouvé dans le FCTM original mis à disposition des compagnies, dans sa version JAN09/07, une description exhaustive de la procedure <<Unreliable Airspeed>> selon la denomination Airbus (Annexe 5.2-A).
Ce document traite des raisons et des consequences d’une <<Unreliable Airspeed>> dans different cas de figure et surtout inclut un chapitre détaillant la méthodologie à appliquer pour cette procedure.

Ne connaisant pas la méthode utilisée par AF pour faire connaitre ce contenu à ses pilotes, nous avons pose la question suivante:

<< Comme était utilise le FCTM (Flight Crew Training Manual) chez Air France à l’époque de l’accident du vol AF 447? S’il n’était pas remis aux pilotes, comment le contenu pédagogique de ce document spécifique a chaque type d’avion était-il tranmis auxpilotes?>>

La réponse d’Air France:

<< Le FCTM du constructeur n’était pas remis aux equipages de la compagnie à l’époque de l’accident. Il était utilise par les rédacteurs des manuels TU et les rédacteurs des services de formation qui en extrayaient les éléments pertinents pour la redaction des manuels tells que le manuel de formation et d’ éntraîinement A330/340 et les livrets de briefing des ECP.

Le contenu du FCTM sort du strict cadre de la formation et de l,éntraînement. Sa date de parution (janvier 2005) est largement postérieure a la sortie du TU et du manuel de formation de la compagnie. AIR FRANCE n’a pas jugé utile de l’adapter car il n‘apportait pas d’éléments nouveax aux contenus des manuels de la compagnie. Dans tout les cas, il ne pouvait etre utilise en etat car le FCTM repose sur une doctrine d’exploitation AIRBUS qui implique l’utilisation du FCOM et par consequent une repartition des tâ ches proper au constructeur. AIR FRANCE avait sa proper doctrine d/exploitation qui était commune pour tous les aviona en service a la compagnie. Pour des raisons de coherence et de claret avec le TU AF, le FCTM du constructeur ne pouvait etre utilise directement par les equipages AIR FRANCE>>So there you have it – there was a more complete guide to the situation, but AF management declined to send it on to the people who might benefit from it.

@Dozy
Regarding Direct Law, as it essentially bypasses all the rate demands and the automatic trim, would it not be the case that the jet does have longitudinal static stability around the current trim setting, as would any other airliner in that configuration?

Reread the first and third paragraphs of my posting #752. I think you will find the answer there.

gums

14th Oct 2014, 16:38

Thanks, OG and Retired.

The thing I have been trying to get across since I was accepted by this august body is the underlying control algorithms and their implementation are not clearly explained in the FCOM's that I have ( flare mode one exception, maybe).

I still see pilots talking about the pitch attitude implementation as if the control law was only a rate command. As Winner and Palmer pointed out, the jet uses both rate and gee to get the nose moving. Once you let off the stick, the jet adjusts the rate/gee command "corrected for pitch attitude" . You get what seems to be attitude hold, and until you have several failures you stay at the last pitch before releasing the stick. Would seem to me that a pitch rate command of zero would apply when not pulling or pushing the stick. You would still get actual movement of the elevator, and then the THS to maintain zero rate, however.

That surface movement was what I demonstrated to all my students. Our rate function was minimal at normal speeds, so it was almost all the gee. Since we could trim for a gee, we would move the manual trim wheel all the way back for about 3.5 gees command while holding forward stick. At a realistic speed we neutralized the stick and the jet would do a beautiful loop. As speed slowed, AoA went up and stopped at the limit. We then rode the AoA limiter over the top and down the back side until 3.5 gees. All the while you could look back and see the horizontal tail "trimming" until it reached the mechanical stop, then going back to its original position as speed increased on the back side.

So that's what happened to the 'bus, Doze. The THS would have kept moving even with a neutral stick ( pitch) to reduce elevator position. I don't feel the elevator would have to be "maxed out", but the system would try to reduce its position just like we used to do with manual trim wheels and actual mechanical "feel" to our yoke/wheel/stick.

The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player. And no AoA protection!!! So the jet flew right into the stall once at the pitch attitude, and the pilot's pitch inputs might only have been important if nose down for several seconds ( as we have seen by those here in the sims).

Glad to see enough here understand the longitudinal stability issues.

BOAC

14th Oct 2014, 17:06

So, we are back to having something saying "That's enough mose-up THS, boys and girls - if you really want more push this over-ride button" - what is wrong with the concept?

EDIT For 'mose' read 'nose':D

DozyWannabe

14th Oct 2014, 17:07

So that's what happened to the 'bus, Doze. The THS would have kept moving even with a neutral stick ( pitch) to reduce elevator position.

Only below 1.3Vs, if I understand OG correctly. The pitch/power settings in the supplementary UAS procedure would have kept them above that, had AF thought to provide that information.

Regardless of this factor, the DFDR trace clearly indicates that the THS position change was neither gradual nor "insidious" - it was a direct response to repeated NU demands from the SS, including the slam against the back stop.

@BOAC - the A320 has a trim limit in Alternate, and according to OG it will also halt further NU trim in the event of a Stall Warning. Why this wasn't carried over to the A330/340 is a question for Airbus.

Owain Glyndwr

14th Oct 2014, 17:21

No Dozy, the THS will move to reduce sustained elevator deflection at any speed

DozyWannabe

14th Oct 2014, 17:27

No Dozy, the THS will move to reduce sustained elevator deflection at any speed
Right, but isn't a neutral stick effectively zero elevator demand? I'm probably missing something here...

Owain Glyndwr

14th Oct 2014, 17:39

No its not. If the pilot makes a change of state that requires elevator deflection and then releases the stick the elevator will remain at the deflection required to maintain the new flight condition until the integral term causes the THS to move and replace the elevator with THS deflection. Neutral sidestick would be zero elevator in long term but not transiently

BOAC

14th Oct 2014, 17:48

the FCS will comandeer the elevator to do the THS job, i.e. flight path stability and thus reduce residual elevator available to the pilot or auto-pilot for maneuvering.- perfect! So, 2 things will happen

1) The crew will know they have reached a practical, 'sensible' limit

2) 447 would have eventually run out of nose up elevator and the nose would have dropped.

Bingo!

BOAC

14th Oct 2014, 19:02

It doesn't even get close to full FCS elevator deflection at approach speeds if stopped at 2 ANU, - are we talking deflection or effect? I have no knowledge of AB THS angles, but what would full deflection at 2ANU achieve? I see mention of THS 13 in AF447 - is that 'sensible'? Presumably CofG and other factors could be used to compute a sensible limit? Remember I am arguing for a 'wake-up call' to the driver, and would full back stick still produce the expected response if the THS had been 'stopped'? There apparently needs to be some way of alerting a crew that auto-trim has gone beyond reasonable bounds and that shirley summat must be wrong?

PS I now have a line in spring-loaded boxing gloves if you want any.:)

DozyWannabe

14th Oct 2014, 22:31

@Winnerhofer - Boeing's "Synthetic Airspeed" is essentially the same deal as Airbus's BUSS system, presumably with the same or similar limitations.

Bpalmer

14th Oct 2014, 22:43

With gee and pitch rate components of the other laws, the jet is basically "neutral" for speed stability ( no "trimmed" airspeed as we old farts remember). So slowing up does not lower the nose as we were used to. And the converse for application of power regardless of engine mounting - you won't climb to maintain the "trimmed" speed ( actually AoA).

Yes! That's a point that is often missed and underemphasized in learning to fly the bus. The airplane is essentially point-and-go. If you pull back on the stick for a few seconds and let go, the airplane pitch will stay there. If you're in cruise flight (that's a lot of forward energy), you can easily be going up at 6,000 feet per minute quite quickly. (this happened in another very interesting—yet non-fatal incident between an A330 & A340 in October 2000 (http://www.rvs.uni-bielefeld.de/publications/compendium/incidents_and_accidents/ACAS-AAIB-dft_avsafety_pdf_501275.pdf) where " the aircraft climbed rapidly (reaching a peak rate of about 6,000 ft/min) due to the increase in lift created by the flight control system's capture of alpha prot. " Now, normally the protections will prevent you from getting into trouble as a result, (with rare exceptions like the above where it was arguably the cause of the trouble, but if the protections are degraded reduced (to stabilities) or absent (versions of alternate 2: AF447), then it's all up to the pilot to establish a reasonable pitch attitude. The natural aerodynamic stabilities will not do it.

But this is the first I have seen for the jet not having positive static stability. I mean basic aerodynamic stability, unfettered by computers using rate and gee and air data sensors. My trusty Viper was no kidding statically unstable until above 0.9 M. We also did not have the plethera of alternate modes and sub-alternate modes - it was gee and AoA protections only. But like the 'bus, we were neutral WRT speed stability. Sucker would hold the trimmed gee until it reached 27 degrees AoA ( remember, we could trim for a gee).

Need Mssr Palmer here, or someone else to try "direct law" and set the THS, then let go of the stick.

Direct law is much more like a 767. But the stick forces are light - they are always the same with the same displacement from center as there is no artificial feel system. Flying in direct law is a matter of using the trim to avoid having to hold the sidestick out of the neutral detent. It's like some cars that have the power steering set so it has virtually no feel and takes no effort on the wheel. It handles fine, you just use the trim wheel manually so that you can have the stick neutral as you fly. (though still primarily controlling pitch with sidestick)

It's also interesting note that in alternate law the stabilities are actually the airplane's natural stabilities. The pitch is in essentially direct law. The effect is subtle—due to the absence of an artificial feel system requiring tens of pounds of force one might call them "weak"—but at least there is a tendency to pitch to the trimmed airspeed—which would theoretically be higher than the airspeed that results in trouble—but who can guarantee the crazy scenarios one might conjure up. But, the activation of those stabilities is based on airspeed as a trigger. So, when airspeed is thrown out of the equation as it was in AF447 (due to disagree and a change rate that was deemed invalid), the stabilities aren't allowed to become part of the flight control law and stall prevention and recovery is all up to the pilot again. G-load demand is a crappy flight control law to be in for stall recover. When the airplane starts to fall (accelerate downward G <1.0) the airplane's reaction to maintain a neutral-sidestick command of 1.0g is up elevator, followed by nose-up stabilizer. ooops.

gums

14th Oct 2014, 22:59

Awwwwww, man! After all these years I read from an esteemed contributor

Right, but isn't a neutral stick effectively zero elevator demand? I'm probably missing something here

In these cosmic FBW jets, the control surfaces move wherever they have to in order for the jet to achieve the "trimmed" or "desireable" gee. Not attitude or bank angle or speed, but a mix of rates, gee and maybe AoA.

Okie has tried to explain a lot of this with a mix of pilot lingo and engineer stuff ( and I think he had some Bk 10 Viper experience). I tried from first seeing the wreckage photos and then data recorder traces. Looked like a classic deep stall impact. The c.g. charts I then got showed it was damned near impossible to get into a "deep stall". "deeply stalled" was possible when in reversion modes such as AF447.

So I abandoned the "deep stall" line of reasoning and tried to see how to stall the jet that many believed could not be stalled. Turned out to be the same techniue as with the Viper. Achieve a decent pitch attitude, run outta airspeed faster than the manual or "protected" laws and control surface deflections can work to achieve the desired gee/rate and voila!

P.S. @Winner synthetic speed and use of AoA indications prolly shoul be on thread of its own.

g109

14th Oct 2014, 23:49

Excellent article.
..... The airplane was in the control of the pilots, and if they had done nothing, they would have done all they needed to do.....

Should Airplanes Be Flying Themselves? | Vanity Fair (http://www.vanityfair.com/business/2014/10/air-france-flight-447-crash#)

CONF iture

15th Oct 2014, 01:10

2) 447 would have eventually run out of nose up elevator and the nose would have dropped.
That would be still pitch under alternate law but without any THS involvement.
What would be sensible is pitch under simple direct law where the pilot has to force to keep the nose up and any release of the stick would let the nose drop.

The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player.
Very big indeed

jcjeant

15th Oct 2014, 02:57

g109
Excellent article.
..... The airplane was in the control of the pilots, and if they had done nothing, they would have done all they needed to do.....Except Derosay (Pilot Airbus Industrie) .. what is the pilot that will touch nothing ... when the autopilot turns off .. the pilot finds by instruments that the plane suddenly lost altitude and that he quickly takes a tilt
At Airbus we already had Ziegler as saying that the plane could be flown by his concierge .. and now we have Derozay who said in a documentary .. the pilot must touch nothing ...
I hope that the pilots are not going to learn from these two ridiculous comments

Volume

15th Oct 2014, 03:59

would have eventually run out of nose up elevator Sorry for spoiling the discussion with facts from the FDR...
For the first 30 Seconds of the event, nose up eleveator never exceeded 1° nose up. (full would be 30°)
For the first Minute of the event, nose up eleveator never exceeded 5° nose up.
Only when allready in full stall and THS already at almost full nose up, the elevator for the first time was fully deflected nose up (and then left there for around 45 seconds with the THS at the full nose up stop as well by that time).
During the first more than 90 seconds the aircraft never "ran out of nose up elevator", it was using less than 30% of the available elevator deflection. It was perfectly possible to fully stall the aircraft using less than 30% of available elevator deflection, but a lot of THS.

tartare

15th Oct 2014, 04:29

G109 - that is a brilliant article.
How terrifying.
I just read through this:
http://aerosociety.com/Assets/Docs/Publications/SpecialistPapers/Aeroplane_Upset_Recovery_Training.pdf
Have followed the whole `children of the magenta line' loss of basic stick and rudder skills debacle for some time now.
A layman's question.
To what extent do airlines practise jet upset recovery training or jet upset scenarios in simulator check-rides that would mitigate the AF447 circumstances?
Is it standard practise / has it been for a long time?
Does it vary from carrier to carrier?
Are there any today who are considered best practise in simulating extreme jet-upsets.
I had just assumed that it'd be standard practise - even allowing for iced pitots (aka partial panel failure exrecises in steam cockpits).
Nasty old check-ride Captain puts the 30 degrees nose in a bank up right near coffin-corner and then smiles and says "Open your eyes - you have control..."

roulishollandais

15th Oct 2014, 04:34

Boeing's Synthetic airspeed, Airbus BUSS, safe USN's AoA, or Klopfstein's old inertial HUD.

Volume

15th Oct 2014, 05:38

To what extent do airlines practise jet upset recovery training or jet upset scenarios in simulator check-rides that would mitigate the AF447 circumstances?Can a simulator accurately "simulate" what no test pilot ever dared to fly? Post Stall behaviour of aircraft is very hard to predict. Detached airflow is beyond any CFD capability. Reynolds numbers will make wind tunnel model testing invalid as well. And which combinations of system failure and upset do you want to simulate?
Philosophy today ist to avoid getting there, not how to survive once being there.

jcjeant

15th Oct 2014, 06:44

Philosophy today ist to avoid getting there

I think this philosophy is in force since the flight of Wright brothers

RetiredF4

15th Oct 2014, 07:25

BPalmer
The airplane is essentially point-and-go. If you pull back on the stick for a few seconds and let go, the airplane pitch will stay there.

This statement is esentially misleading and not completely correct. Correct would be the airplane will maintain a loadfactor of 1g. Correct would be if you add ....... if the autothrottle takes care of the speed. What's the difference some might ask.

Otherwise without the autothrottle (that droppped out at AF447 right at the beginning) the aircraft will decelerate in a climb or accelerate in a descent, and the computers would increase the pitch ( if in a climb) or decrease the pitch (if in a descent) to maintain the one g flightpath.

That mindset "set the pitch and it will stay there (and go there) might have influenced Bonins actions with the SS.

Gysbreght

15th Oct 2014, 08:51

Can a simulator accurately "simulate" what no test pilot ever dared to fly? Post Stall behaviour of aircraft is very hard to predict. Does it have to be 'accurate'? As long as it indicates to the pilot in a reasonably realistic manner that the airplane is stalled, and elicits the proper response from the trainee, it would perform its intended function. No need to go beyond conditions that 'no test pilot ever dared to fly'.

tartare

15th Oct 2014, 10:12

It's an interesting point.
Philosophically the more one thinks about swept wing high subsonic airliners the more one realises they are designed to climb benignly, cruise in a stable configuration and descend gently.
Big, vulnerable ocean liners of the sky that are pretty much optimised to point directly into a high mach airflow, and stay there.
A great over simplication of course, but makes you realise how perilous things get very quickly when they are outside that envelope.

Jwscud

15th Oct 2014, 10:31

I thought it might be an interesting addition to the discussion to note that Gulfstream has just launched the new G500 and 600 with full FBW akin to the 650, but with linked and fully back driven side sticks.

bubbers44

15th Oct 2014, 13:52

How dare Gulfstream take all the challenge out of FBW by letting both pilots know what the PF is doing with the SS?

The next thing Gulfstream will do is put a big yoke in front of the pilots so even the jump seater can see what they are doing.

CONF iture

15th Oct 2014, 14:02

And they call them Active control sidesticks :
Active control sidesticks replace the control columns, creating more space and better comfort for pilots. The sidesticks are digitally linked to provide the same response and control of a traditional pedestal-mounted yoke to ensure that both pilots see and feel every maneuver and control input the other pilot makes.

Gretchenfrage

15th Oct 2014, 14:14

I wouldn't ridicule this bubbers. I think it's great.

Small manufacturers or those not depending on solely profit orientated, cynical airline managers, can change design to reach the modern optimum. A optimum defined by experience and listening to research. For such manufacturers the slogan "we strive for utmost safety" is not only a hollow commercial.

I welcome a moving side-stick, just as i welcomed a moving auto-throttle.
Both systems allow the pilots to instantly be part of the modern fly-by-wire system, to act in a symbiotic partnership and, if needed, to act as last authority (at least if minimally trained, but that's another story).

The two biggies in the airline market are cornered in their geriatric philosophy due to silly commercial statements of their CEO's, or due to looming lawsuits if they would change only the slightest small design flaw (thanks to the cynical lawyer brigade).

One of them could easily revert to the originally intended design and relieve us from the stumbling block between our legs for 16 hours, the other could finally admit that there are still humans at controls and such creatures work better with all their senses than if deprived by some.

Again, i welcome the design by Gulfstream, their cockpit reflects what should be in any Airbus or Boeing. :ok:

BOAC

15th Oct 2014, 15:27

I saw it, OK, before you were 'trashed':ok:

To cut a long story short - has anyone - FAA/CAA/EASA/Airbus/Boeing come up with a solution to what appears to be a burgeoning 'blackman in the woodpile' - Autotrim?

DozyWannabe

15th Oct 2014, 16:19

Again, i welcome the design by Gulfstream, their cockpit reflects what should be in any Airbus or Boeing. :ok:
Until some tired spanners wires them up the wrong way - then you have one side electronically forcing opposite motion into the correctly-wired side.

As has been stated before (and not just by me) there are pros and cons to all the existing control philosophies - obviously pilots of the old-school will prefer the closest possible mimicking of traditional behaviour, but that does not necessarily mean traditional is either better or better for everyone.

@BOAC - I still think the autotrim situation is being rather over-emphasised by those who want to redirect blame to the control philosophy and the manufacturer more than they want to do anything else (including solving the actual problems that led to this accident).

BOAC

15th Oct 2014, 16:37

@BOAC - I still think the autotrim situation is being rather over-emphasised by those who want to redirect blame to the control philosophy- it is not a 're-direction'. It is a contributary factor. Without it one hopes this deficient crew (and THY at AMS, and TOM at BOH and........and....) would have noticed the need to keep trimming?

DozyWannabe

15th Oct 2014, 16:50

- it is not a 're-direction'. It is a contributary factor. Without it one hopes this deficient crew (and THY at AMS, and TOM at BOH and........and....) would have noticed the need to keep trimming?
I'm not going to say the crew were "deficient", in this particular instance some bad choices were made and, as with a lot of CRM-centric accidents, they never managed to work as a team. They were let down much earlier in the chain by their airline and the regulator, however, and yes - there are some questions about the aircraft systems behaviour.

Autotrim is a fundamental aspect of how the Airbus FBW system operates normally, and causing it to drop out in an abnormal situation when there's nothing stopping it from working is probably overkill. The way it behaved is a contributory factor in this instance, however I have trouble accepting this behaviour:

http://i1088.photobucket.com/albums/i331/turricaned/fdr-munge.png

as "insidious". It is a clear and definite response to the SS input, going from -3deg to -13.5deg in around 45 seconds.

Theoretically there may be an issue with a small climb component causing the THS to trim NU in a less obviously-perceptible way, but that's not what happened here. Re-instating the limits apparent in the A320's system would probably help matters - either limiting to a smaller NU trim in Alternate or halting NU trim entirely with the stall warning (which you can see coming on just as the THS starts rolling NU).

BOAC

15th Oct 2014, 17:03

It is a clear and definite response to the SS input- precisely. It does, however, hide from a crew that extra cue that the speed is reducing when it should not be. In 'the old days', you would need to keep applying back stick until you ran out of it, and trim the THS to restore elevator margin. This system allows the concierge to blythely point the aeroplane at the stars and not worry about a thing while the speed heads rapidly south - without any cues.

In order to 'dumb down' the art of flying an aeroplane the manufacturers have created large blinkers for crew to wear.

DozyWannabe

15th Oct 2014, 18:04

In order to 'dumb down' the art of flying an aeroplane the manufacturers have created large blinkers for crew to wear.
The design is not about "dumb[ing] down", and never was. If you look at things with that assumption then aspects of the design will look that way - but that assumption was applied after the fact by pilots who took too much notice of BZ and not enough of Gordon Corps.

Autotrim exists in this system primarily for the very reason you describe - namely the passive sticks. Before we get away from ourselves, it's worth bearing in mind that it has worked just fine for millions of flights over 26 years in service. We are looking at a single anomaly here, and one in which the controls as applied were *way* outside what should have been attempted even in an emergency situation.

Perhaps it should become an early "must-know" aspect of Airbus FBW conversion training (if it isn't already) that when you're using the stick to fly the aircraft manually, you're affecting trim as well as elevator position.

Circling back to the initial point, the design was not an exercise in "dumbing down", it was simply one possible solution for aircraft control when given the opportunity of a "clean room" design. In a hypothetical scenario where aviation began in 1983 rather than 1903 (and materials/computing tech were unaffected), what the '80s Wright Brothers may have come up with would not look like the 1903 Flyer - it'd probably be a carbon-fibre job festooned with digital technology and operated in an entirely alien manner. With autotrim we're looking at an aspect of the Airbus design (specific to the A330/340 in fact) that *may* have made things a little more difficult, but has done so only once in however many million hours of flying the type has done. Seems a little excessive to say the overall design was a mistake based on that single incident, does it not?

BOAC

15th Oct 2014, 18:20

With autotrim we're looking at an aspect of the Airbus design - don't Boeings have it too?

rudderrudderrat

15th Oct 2014, 18:52

Hi DW,
Before we get away from ourselves, it's worth bearing in mind that it has worked just fine for millions of flights over 26 years in service.
Agreed. Normal Law with its protections is very good.

But even you may be persuaded that ALT Law (without protections but with auto trim continuing beyond the stall warning) doesn't have a good record.

As Bpalmer says in post #773 "G-load demand is a crappy flight control law to be in for stall recover. When the airplane starts to fall (accelerate downward G <1.0) the airplane's reaction to maintain a neutral-sidestick command of 1.0g is up elevator, followed by nose-up stabilizer. ooops."

DozyWannabe

15th Oct 2014, 19:10

- don't Boeings have it too?

The FBW models (777/787) do, but I believe it operates differently. Tdracer's probably the best bet to go into detail there.

But even you may be persuaded that ALT Law (without protections but with auto trim continuing beyond the stall warning) doesn't have a good record.
"Even" me? Fie, sirrah - I'm just trying to be even-handed and not get carried away. What you say may be true, but I don't have a list of all incidents where Alternate Law was activated to make a call there...

As Bpalmer says in post #773 "G-load demand is a crappy flight control law to be in for stall recover. When the airplane starts to fall ... the airplane's reaction to maintain a neutral-sidestick command of 1.0g is up elevator, followed by nose-up stabilizer. ooops."
From what I've read it's not a straight g-load setup, but I'll defer to those who know better. Your A320 seems to have a safeguard against NU trim when the Stall Warning sounds, and why this isn't the case for the later widebodies is absolutely a question that should be put to Airbus.

However - in a stall recovery scenario (as opposed to the avoidance scenario), there's no way the SS should be neutral - it should be commanding ND in order to effect a recovery.

Lonewolf_50

15th Oct 2014, 19:37

Dozy:
Without getting into the point of "don't stall a passenger liner, that isn't what the passengers paid for with their ticket" ...
However - in a stall recovery scenario (as opposed to the avoidance scenario), there's no way the SS should be neutral - it should be commanding ND in order to effect a recovery.
Or maybe the pilots should be doing that. ;) So long as HAL doesn't obstruct that action, HAL will at worst be neutral, and more probably helpful with all of the features in his kit.

DozyWannabe

15th Oct 2014, 20:06

Or maybe the pilots should be doing that. ;)
Indeed - and it's the only way the SS will give that order is if the pilot commands it. I'd hoped that'd be obvious! :ok:

PS. Gums will know all about this, but I've always tended to wince a little at the "HAL" analogy. HAL was a state-of-the-art artificial intelligence (and a fictional one at that), whereas the computers used in the FBW Airbii are roughly as "intelligent" as the controller chips in your washing machine.

Lonewolf_50

15th Oct 2014, 20:26

Dozy:
I find your objection rather empty.

HAL (a fictional computer meant to work on a fictional spacecraft) served the same function as an autopilot does, which is to relieve the crew of X amount of tedious functions in pursuit of their mission being. HAL is used metaphorically, as a symbol of the dangers of overreliance on automation. (Who the hell is flying the plane: the pilots or HAL?)

Early autopilots were often referred to as "George" for a reason that I think goes to slang of the time: "Let George do it" was a throwaway phrase from about the time my dad was in college, 40's - 50's. Are you going to object to that as well?

Note: overreliance on automation has come to the attention of the FAA, in a negative sense, of late ... I'll suggest to you that AF 447 is a fruit from the tree of the overreilance on automation, which seems to have at its root a non trivial number of airline company SOPs.

DozyWannabe

15th Oct 2014, 20:46

HAL (a fictional computer meant to work on a fictional spacecraft) served the same function as an autopilot does...
Sure - but I thought we were talking about the EFCS, which is a very distinct concept from autoflight...

(Though autoflight computers aren't that smart either...) :ok:

mm43

15th Oct 2014, 21:04

I welcome a moving side-stick, just as I welcomed a moving auto-throttle.
Both systems allow the pilots to instantly be part of the modern fly-by-wire system, to act in a symbiotic partnership and, if needed, to act as last authority (at least if minimally trained, but that's another story).There's nothing wrong with that statement, but in the case of AF447, Bonin was aware the A/T had dropped out, and he used the thrust as and when he wanted.

The 'Elephant' in the cockpit was in fact the biggest piece of control equipment on the flight deck - the THS Wheel, which was designed to perform two functions,

(1) Give a visual feedback of the THS position, and
(2) Provide a direct means of manual control of the THS, if and when required.

I venture that (1) was not noticed, because the THS isn't/wasn't a normal part of the crew's scan, and secondly I have the distinct impression that in the cruise its movement was small and only becomes active in the non cruise sectors of a flight. Under NL that is a given, and the THS just moves to neutralize elevator demand as required (the simplistic explanation).

This brings me back to Bonin's actions with the SS, and his apparent disregard for the NU demands he was making and the NU attitude that he must have seen on the PFD. I venture that he was schooled to believe that under NL the aircraft was unstallable, and SS ANU commands would be modified by the UNoverridable protections. That being the case, it probably goes without saying that (2) never featured in his training.

However, the 'Mammoth' in the cockpit was ALT2b, where a hand on the THS at the appropriate time could have prevented most of what happened. Though, when you don't appreciate how to manage the aircraft energy at FL350+, then there is little left to be said.

Owain Glyndwr

15th Oct 2014, 21:08

Your A320 seems to have a safeguard against NU trim when the Stall Warning sounds

Dozy I have an apology and a confession to make:http://www.pprune.org/images/editor/smilie.gif
You have mentioned several times recently that the A320 has a feature where NU THS movement is inhibited in Alternate when Stall Warning is triggered. Since you got that from me I thought I should check my source,and to be blunt I can't trace where I got it from. There IS a normal law feature on both A320 and A330/340 where NU THS movement is limited to the existing value when alpha protection is triggered (and THS limited to 2 deg ND); i.e. no further NU trim is allowed when there is a potential incidence problem looming, but I can't find any reference to a similar feature in Alternate (possibly worked off stall warning).

That being said, it seems to me that such a function would fill what BOAC is looking for rather well, and I can't see any particular reason or difficulty to prevent it.

Sorry!

DozyWannabe

15th Oct 2014, 21:15

@OG:

No apology necessary. Regardless of where your info came from, my experience in the A320 sim (presuming that the systems behaviour was accurate) showed that NU trim was indeed inhibited shortly after we began the NU SS input. Whether that was linked to the SW or a feature of that control law on the A320, the trim nevertheless stopped of its own accord.

However, the 'Mammoth' in the cockpit was ALT2b, where a hand on the THS at the appropriate time could have prevented most of what happened.
With respect, how does that work? Regardless of the THS position, Bonin was still pulling NU fairly consistently all the way down. They're at about 28,000ft at the point he releases the SS from the back stop - even with that much to play with, it doesn't leave much time for recovery...

mm43

15th Oct 2014, 22:20

With respect, how does that work? Well, to start with the THS wouldn't have added the extra 10° NU and any ND on the SS would have been more effective. Possibly the change may have been noticed - in time?

Ideally, the hand should have been on the THS Wheel from the moment ALT2b was established, which would mean that the implications of Alt2b and the THS behaviour were known. In this case, they weren't.

DozyWannabe

15th Oct 2014, 23:23

Well, to start with the THS wouldn't have added the extra 10° NU and any ND on the SS would have been more effective.
In terms of recovery, the THS position wouldn't have made that much of a difference until sufficient forward airspeed was gained. Even if our experiment (in which the SS was held against the forward stop and only relaxed when 10deg ND attitude was attained) represents a "best-case" scenario for SS input rolling the THS back to neutral (i.e. in under 10 seconds), the situation might still have been recoverable. Even if it was only possible to recover by rolling the trim wheel forward manually, it would still take several seconds to stabilise the attitude at 10deg ND with the SS.

Possibly the change may have been noticed - in time?
Debatable (see above)...

Ideally, the hand should have been on the THS from the moment ALT2b was established.
Why? The THS position was OK at AP disconnect - it didn't start rolling back significantly until the stall was developed...

Linktrained

15th Oct 2014, 23:43

The "elephant", the THS, was not noticed because it was not in the normal scan. It appears to be painted in black and white segments.

If the colours could be replaced for those areas which are not seen in cruising flight, this movement might have been noticed by one of the pilots.

I recall having seen this done on one type of aircraft, where a bright RED was used.

mm43

16th Oct 2014, 00:16

Why? The THS position was OK at AP disconnect . . I'm not arguing that, but trying to make the point that once in ALT2b the FCS will seek to maintain 1g, and if the THS Wheel starts to move backwards (NU) the likely reason is the IAS is dropping, and/or you are holding the SS in NU position. Take your pick.

tartare

16th Oct 2014, 00:38

Bpalmer

16th Oct 2014, 00:47

From what I've read it's not a straight g-load setup, but I'll defer to those who know better. Your A320 seems to have a safeguard against NU trim when the Stall Warning sounds, and why this isn't the case for the later widebodies is absolutely a question that should be put to Airbus.

yes, correct. It is normally a mix of g-load and pitch rate. More pitch rate at slower airspeeds, more g-load at higher airspeeds, with a crossover point where both influences are equal at an unpublished speed - probably somewhere around the greendot–250 kts range.

However - in a stall recovery scenario (as opposed to the avoidance scenario), there's no way the SS should be neutral - it should be commanding ND in order to effect a recovery.
And in Normal law it does. But this was a degraded flight control law with no protections (except g-load) left. Normal law would prevent the need for a "recovery". Due to some questionable design choices, AOA was deemed unusable with indicated airspeed below 60KIAS—so, there's nothing left to drive that pitch down except a pilot's training. (but when that pilot's training for stall recover consists only of full power application during stall training at 5,000 ft—there's not much there to help either!)

Bpalmer

16th Oct 2014, 01:02

From RetiredF4:
BPalmer
The airplane is essentially point-and-go. If you pull back on the stick for a few seconds and let go, the airplane pitch will stay there.

This statement is esentially misleading and not completely correct. Correct would be the airplane will maintain a loadfactor of 1g. Correct would be if you add ....... if the autothrottle takes care of the speed. What's the difference some might ask.

Otherwise without the autothrottle (that droppped out at AF447 right at the beginning) the aircraft will decelerate in a climb or accelerate in a descent, and the computers would increase the pitch ( if in a climb) or decrease the pitch (if in a descent) to maintain the one g flightpath.

That mindset "set the pitch and it will stay there (and go there) might have influenced Bonins actions with the SS..

Well, yes, of course —"point and go" wasn't meant as a technically complete description as you must know. But this is still essentially correct and opposite of the behavior one would expect from an airplane that is not essentially neutrally stable.

And you are correct about the need for a pitch change to maintain that trajectory with speed change, and that's what I meant. A conventionally controlled airplane (or one with C*U) will change not only its pitch but also its trajectory to achieve speed stability vs. the Airbus trajectory/g-load stability. This is evident to Airbus pilots when flap settings are changed- the pitch will self adjust to maintain the trajectory/g-load.

But my main point with the "point and go" comment was that if you displace the ss and let go, the pitch is reasonably stable. UNLIKE speed stable aircraft which would in rather short order begin to pitch down for a speed-seeking fugoid.

DozyWannabe

16th Oct 2014, 01:04

I'm not arguing that, but trying to make the point that once in ALT2b the FCS will seek to maintain 1g, and if the THS Wheel starts to move backwards (NU) the likely reason is the IAS is dropping, and/or you are holding the SS in NU position. Take your pick.
I'll be careful in an attempt not to put my foot in my mouth, but the "maintaining 1G" (or thereabouts) applies in both Normal and Alternate laws. If I recall correctly, the A320's EFCS would interpret that more-or-less literally, and manual S&L flight would actually induce an (extremely) gradual altitude gain (on the level of a few feet per hour) under manual control. This was compensated for and corrected in the A330/340.

I digress - anyway, as I understand it, the deal with ALTN2B is that the "low speed stability" function (i.e. "soft" protection) doesn't work, which means that theoretically:
Below 1.3Vs the aircraft is speed unstable and this is where the BEA comment to the effect that the aircraft might drift to stall even with zero stick input becomes valid.
This has nothing to do with autotrim or THS. Every point made in this regard thus far appears to be educated guesswork. The only way to know would be to take an A330-200 up and try the theory out. A level-D sim might get close to it, presuming that the emulation is correct.

...will the EFIS in an airliner simply peg out at around 40 degrees nose up?
No. Not in the least. Which part of the article are you referring to?

Due to some questionable design choices, AOA was deemed unusable with indicated airspeed below 60KIAS
Well, hold on a minute there. If the manufacturer of the AoA vanes specifies that their output is unreliable below 60kts, how else are you supposed to implement the system? Remember that the A330 and 340 were originally certified with the Goodrich pitot tubes (never known to suffer a dual/triple failure), and the Thales AA fit was an option later in the type's lifecycle.

Bpalmer

16th Oct 2014, 01:33

If I read that Vanity Fair article correctly, it suggested that at certain points the EFIS did not display correct values because the jet's pitch, and/or roll exceeded what it could measure.
I had assumed that like a fast jet panel, an airliner EFIS would display values even if they were way outside the recommended operating envelope.
So if you are 60 degrees nose up (extremely high alpha) will the EFIS in an airliner simply peg out at around 40 degrees nose up?
If - apologies to Tex Johnson - you flew a barrel roll in an A320 for example, or were able to fly a loop would the EFIS display flip and display inverted pitch or roll values as it does in a jet fighter, or is it simply not programmed to do this, because it's not expected, and therefore would be an unnecessary complication/and or cost to add?

AF447 did not reach an unusual attitude at any point. The only parameter that could have triggered the unusual attitude law would have been the 45° AOA.

The EFIS is certainly capable of displaying the full range of attitudes (having done them in the simulator).

However, there is some anecdotal evidence of loss attitude display in similar incidents, detailed in my book. AF447: "we have not more usable displays" (certainly open to interpretation)—which AB says refers to airspeed and vertical speed indications since there is no good explanation why attitude should be lost in such a situation, and a Mihin Lanka flight whose pilots "reported the loss of both attitude displays on their Primary Flight Displays (PFDs) for up to 20 seconds." It is for this reason that the BEA recommended that there be some visual recording of what is actually displayed on the EFIS, instead of only recording the raw data.

_Phoenix_

16th Oct 2014, 03:57

Why? The THS position was OK at AP disconnect - it didn't start rolling back significantly until the stall was developed...

Apart of SS position, why THS did start rolling back while Stall was online? What's the logic in this, if any?

jcjeant

16th Oct 2014, 04:39

If the manufacturer of the AoA vanes specifies that their output is unreliable below 60kts, how else are you supposed to implement the system?Ok that's fine
But why stop the alarm when stall speed is well over 60 knots and certainly under 60 knots !!!!
This does not correlate with the vanes certification
What would be the point that they are certified to 30 knots or 80 knots
The fact is that 80 or 30 knots forward speed .. A330 aircraft is no longer in normal flight .. and the first thing that comes to mind .. is that this airplane is stall
Again and again .. why stop the stall alarm at 60 knots ????
Same question here:
What's the logic in this, if any?
At 61 knots .. stall alarm warn the pilot .. your plane is in stall
At 59 knots and under .. no more stall .. that's the Airbus magic .....

rudderrudderrat

16th Oct 2014, 06:29

Hi DozyWannabe,
If the manufacturer of the AoA vanes specifies that their output is unreliable below 60kts, how else are you supposed to implement the system?
You simply make the stall warning invalid below 60 kts AND on the ground (to prevent false nuisance stall warnings during the early take off roll).

However, when you are airborne, if the angle of AoA sensors think you are stalled and even if you have less than 60 kts indicated forward airspeed - then you are definitely stalled. Therefore remove the 60kt logic once airborne.

@ Owain Glyndwr but I can't find any reference to a similar feature in Alternate (possibly worked off stall warning).
A320 FCOM OP-020, Flight Controls, Alternate Law
"At the flight envelope limit, the aircraft is not protected, i.e.:
In high speed, natural aircraft static stability is restored with an overspeed warning
In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G."

alexd10

16th Oct 2014, 07:24

Originally posted by DozyWannabee
Well, hold on a minute there. If the manufacturer of the AoA vanes specifies
that their output is unreliable below 60kts, how else are you supposed to
implement the system?

... Perhaps adding a few lines of code and computing the "true" airspeed in the vane? (like dividing by cos(AOA))??, tis would give a speed of ~73kts for a 60KIAS and 35° AOA !!

or.... taking into account the vertical speed and computing the resultant speed?,

Or.... clearly indicating SW disabled, not simply silencing it like in a normal exit from the stall??

It is verry possible that a more inspired design of stall warning could saved the day, taking into account that at the return of capt on flight deck the SW was just silenced..

BOAC

16th Oct 2014, 07:26

That being said, it seems to me that such a function would fill what BOAC is looking for rather well, and I can't see any particular reason or difficulty to prevent it. - agreed, but if I may make a plea - while this thread is about 447, it should really be expanded to cover all instances of autotrim which have caused numerous LOC incidents. It appears that we can no longer expect pilots to monitor airspeed (where available) nor to monitor aircraft attitude, so something surely needs to stop HAL or whatever we choose to call the system from trimming to absurdity. Again, a 'stop' at a sensible limit with a 'conscious' over-ride option for when the horses in the hold break loose would do it, would it not? The bonus is that we don't need any 'sophisticated' software with its inherent traps to do it - a simple position transducer triggering a switch with a 're-close' button would be fine.

WRT Airbus in particular, rrat at post #818 with an 'AND' switch is the answer plus inhibition of autotrim in ALL modes following the subsequent stall warning, and this should go a long way to helping those are not skilled pilots.

Not forgetting, of course, for all types, a seismic shift in training policies.:ugh:

Owain Glyndwr

16th Oct 2014, 07:46

posted by BOAC

Again, a 'stop' at a sensible limit with a 'conscious' over-ride option for when the horses in the hold break loose would do it, would it not?

Maybe, but a sensible limit would be "configuration conscious". 2 or 3 ANU might be fine for cruise, but full flap, extreme fwd CG and Vref with a modest allowance for a steady turn might need 12 deg or so.
Possibly one simple solution might be to have THS deflections limited according to the slat/flap selection (with no over-ride - anything beyond that limit would have to be held by elevator deflection)

BOAC

16th Oct 2014, 07:53

with no over-ride - anything beyond that limit would have to be held by elevator deflection) - not easy with that - I would like the option to trim for a one-off really extreme condition, but in your latter case there should indeed be no problem having to hold back stick for the duration of the turn, although how that would fit with the computer operators....................

Owain Glyndwr

16th Oct 2014, 08:20

OK, but remember that the pilot won't be the one to hold the elevator, the EFCS will do that - you just won't get it bled off by THS movement

BOAC

16th Oct 2014, 08:58

I assume that is AB? It certainly would be the 'pilot' in a 737. So, for AB, a limit of less than 12 could be used but it might require a positive action to over-ride in some situations - eg your example? Would that be a problem?

I am having trouble trying to imagine any 'normal' pilot in 447 running out of back stick due to this 'limit' trying to hold 10 degrees nose-up whilst zooming up above max alt and thinking "Oh yes, I need to over-ride this THS limit or the nose will drop".:confused: One would hope that that and rrat's continuous stall warning might have some effect?

CONF iture

16th Oct 2014, 13:58

A320 FCOM OP-020, Flight Controls, Alternate Law
In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G.
In these conditions, the automatic pitch trim operation would also stop on the 330 in ALT1, but not in ALT2 with failure of 2 ADRs.
Don't you have that ALT distinction on the 320 ?

AF447 did not reach an unusual attitude at any point. The only parameter that could have triggered the unusual attitude law would have been the 45° AOA.
Speed below 60kt in another one.

It appears that we can no longer expect pilots to monitor airspeed (where available) nor to monitor aircraft attitude, so something surely needs to stop HAL or whatever we choose to call the system from trimming to absurdity. Again, a 'stop' at a sensible limit with a 'conscious' over-ride option for when the horses in the hold break loose would do it, would it not? The bonus is that we don't need any 'sophisticated' software with its inherent traps to do it - a simple position transducer triggering a switch with a 're-close' button would be fine.
Has been effectively required for ages, the presence of a simple DIRECT switch to get rid of any sophistication or protection on demand.

BOAC

16th Oct 2014, 16:59

the presence of a simple DIRECT switch - I say! Steady on! You'll be expecting crews to actually fly the aeroplane next................

DozyWannabe

16th Oct 2014, 20:32

- agreed, but if I may make a plea - while this thread is about 447, it should really be expanded to cover all instances of autotrim which have caused numerous LOC incidents.
Such as? I'm pretty sure this is the only one.

There also seems to be a continuing misinterpretation of the B777's bypass switch (aka "Big Red Button") - it needs to exist in the B777 design due to the software-driven force-feedback. If that subsystem goes and provides misleading control response to the crew, things could get ugly very quickly - so the bypass acts as a "failsafe" for that scenario. Airbus's system doesn't use force-feedback, so there's no need for that kind of failsafe requirement.

Interestingly, the B777 bypass mode has never been used, even though there have been a couple of incidents where it could have come in handy (e.g. Malaysian 124 out of Perth [IIRC] springs to mind). The crews in the incidents didn't take advantage of it.

Lonewolf_50

16th Oct 2014, 20:48

Winnhofer, I understand your point on flying is suboptimal conditions. It can raise the pucker factor, to be sure.

One of the things that you rely on it situations that begin to go pear shaped is training. I had a few brown flight suit nights over the dark, no horizon oceans that all worked out in the end ... not because I was some sky god or some super pilot, not hardly. It worked out because we were trained, had procedures for dealing with things going wrong, and the crew (both pilots and the crew in the back) worked together to get us back to the ship in one piece.

As I commented to Clandestino, I get the impression from the transcripts we have available that the flight deck crew were in a problem solving mode (though it seems that they were behind the aircraft), and grew frustrated as well. I don't get from that limited representation of the event sequence the symptoms of fear.

But it may have played a part. We don't know.

If it did, that's another area of concern for Air France, in terms of training, and possibly at other airlines.

What do you have to fall back on when things begin to go wrong?
Your training and proficiency are key resources at such times.

BOAC

16th Oct 2014, 21:37

Such as? - try post #792. Your focus is too narrow. In each autotrim caused major problems.

DozyWannabe

16th Oct 2014, 21:50

Those two (TC-JGE and G-THOF) are autoflight-related issues, both involving the Boeing 737. Autotrim in the Airbus sense is not a part of the autoflight system, but a component in the EFCS setup.

BOAC

17th Oct 2014, 07:10

As I said, narrow focus. My suggestion was to limit autotrim, full stop.

roulishollandais

17th Oct 2014, 08:01

I agree with Lonewolf50.

Winnerhofer,you are writing some fantasy

Bpalmer

17th Oct 2014, 15:55

Then they did stupid pilot stuff and rode a perfectly good airplane 35000 ft in a stall with the stall horn going
Is that distracting enough to forget there is GPS groundspeed and an iron gyro AI available for cross reference before (inexplicably) yanking and banking on the joystick?

GPS Groundspeed...Really?
Try this on your next flight. Tell your fellow airman to close his eyes and tell you what the GPS groundspeed was sometime in the last minute. Try to mentally correlate that to airspeed and make appropriate adjustments to keep your aircraft within the narrow indicated airspeed window—all when your struggling to keep things right side up. In the fear mode we don't think well.

The far better answer, one that is the standard official technique when encountering severe turbulence, is to try to hold a normal ATTITUDE. Don't chase the altitude or the airspeed (if it's working). That is much easier to grab on to, and requires no mental math. Do you really want someone jockying the thrust levers to chase a GPS groundspeed? Compound that with the fact that if you are in this situation you're probably in an area where the wind is changing and what was a good GPS groundspeed 10 minutes ago is now 50 knots too fast or too slow—either one of which critically dangerous.

If the AF447 crew had done that, had Bonin resumed the normal pitch attitude when Robert was telling him to "go back down," we never would have heard of them.
The question is did Bonin even know what the normal attitude was without the aid of the flight director? That's where a bit of regular "turn it all off" pays dividends. If you're hand flying with the flight director on it's like typing a dictated story thinking you're coming up with all the good ideas.

DozyWannabe

17th Oct 2014, 16:13

As I said, narrow focus. My suggestion was to limit autotrim, full stop.
Why? What good would it do?

I'd dispute the "narrow focus", the scenarios are completely different and completely unrelated - other than the point that the crews involved didn't keep an eye on their trim status when they should have done so.

In fact the two B737 incidents began with failing to monitor airspeed and thrust settings on approach - the trim situation was an afterthought. I'm pretty sure I remember reading that SOP in a B737 go-around scenario from autoflight involves adjusting the trim to a setting commeasurate with go-around, because approach trim configuration isn't going to work there.

AF447 wasn't caused by the automatic trim, and unlike the B737 incidents, the trim was effectively set by the pilot's commands - not autoflight.

Those are pretty different scenarios no matter which way you slice it.

BOAC

17th Oct 2014, 16:27

other than the point that the crews involved didn't keep an eye on their trim status when they should have done so. - starting to widen? In terms of the 'big picture' it is a lot worse when autotrim takes you out of 'acceptable' areas when flying manually as with Airbus, but still bad when it does it in autopilot in any type.

DozyWannabe

17th Oct 2014, 16:48

it is a lot worse when autotrim takes you out of 'acceptable' areas when flying manually as with Airbus...
Well, it's interesting you should say that. Let's not forget that when the A320 was launched, there was a very vocal group of pilots who were up in arms about letting the technology decide for them what was "acceptable" and what wasn't.

So for whatever reason, the A330/340 implementation of autotrim always defers to the pilot as to what is "acceptable" when the systems are in a non-normal configuration. Again - intentionally or not, the THS was *commanded* to that position by the pilot flying.

@Bpalmer - re: pitch/power/attitude - absolutely right, and the correct pitch/power settings were in that supplementary FCTM sheet that AF apparently didn't deign to pass on to the pilots.

BOAC

17th Oct 2014, 17:11

the A330/340 implementation of autotrim always defers to the pilot as to what is "acceptable" when the systems are in a non-normal configuration - you are still 'missing it'! Not in the case of 447, it didn't. The pilots had no idea what they were doing, coupled with a design fault in the stall warning logic, so the system just carried on willy nilly as programmed - and to call that 'deferring' is sad. It is like holding up 4 fingers to a blind man and asking him how many.

Anyway, Dozy, we are entering Oozlum bird land, so I'll sign off with you.

DozyWannabe

17th Oct 2014, 18:31

- you are still 'missing it'! Not in the case of 447, it didn't. The pilots had no idea what they were doing, coupled with a design fault in the stall warning logic, so the system just carried on willy nilly as programmed - and to call that 'deferring' is sad. It is like holding up 4 fingers to a blind man and asking him how many.
With all due respect, I don't accept that. SS input affecting both elevator position *and* THS position has been "baked in" to the Airbus EFCS design since day one. It's one of the aspects of flying a FBW Airbus that is somewhat different from the traditional setup, and as such should be one of the fundamental things understood as part of conversion/type rating training. There should be no excuse for crews not to have that in the back of their mind when manipulating those controls.

The technology can't know whether the pilots know what they're doing. It isn't psychic - hell, it isn't even that "intelligent". The point is that you can either design a system which constrains the pilots on that basis, or you can design it on the basis that assumes the crews will know what they're doing and have it follow suit. The A330 autotrim design seems to have erred more toward the latter than the former. I don't know why - it just seems to have been that way.

Furthermore, calling the SW behaviour a "fault in logic" is a bit harsh in my book. For one thing the problem is quite complex in nature (as we hashed out in the older threads) - SW relies on data from the AoA vanes, so how do you deal with a situation where the AoA data may be suspect? What makes it extra complex is that finding a solution to one scenario may potentially cause problems elsewhere - for example if you take rrr's suggestion:

You simply make the stall warning invalid below 60 kts AND on the ground (to prevent false nuisance stall warnings during the early take off roll).

However, when you are airborne, if the angle of AoA sensors think you are stalled and even if you have less than 60 kts indicated forward airspeed - then you are definitely stalled. Therefore remove the 60kt logic once airborne.
There's still a potential "false negative" scenario where the AoA vanes are frozen in a "non-stall" condition.

Then there's XL888 and MH124 both showing the potential consequences of allowing "bad" AoA data through to the EFCS - another thing that must be borne in mind.

Anyway, Dozy, we are entering Oozlum bird land, so I'll sign off with you.
That's a shame - I think it's perfectly reasonable for two people to have differing opinions and accept that to be the case.

I do, however, suspect that there's a bit of a double standard at work here. I was just having a look at the R&N thread about the Thomas Cook B757 incident at Newcastle in which it appears the PIC messed up a go-around by pushing the wrong button and following the (incorrectly configured) FDs immediately afterwards. There seems to be no shortage of posts giving the pilot a shellacking - but I can't help but think that had it been an A321, there would have been a much more concerted attempt to blame the technology.

As long as the "Airbus FBW was designed to patronise pilots" meme holds some belief (even though it's bobbins), that''ll be the case - and I think it's a bit sad that we're in this position after 26 years of the things flying safely.

CONF iture

18th Oct 2014, 00:18

Interestingly, the B777 bypass mode has never been used, even though there have been a couple of incidents where it could have come in handy (e.g. Malaysian 124 out of Perth [IIRC] springs to mind). The crews in the incidents didn't take advantage of it.
You still did not get what happened to that 777 ...
http://www.pprune.org/7022213-post1332.html

Airbus's system doesn't use force-feedback, so there's no need for that kind of failsafe requirement.
And you still did not get what would be the purpose of a DIRECT switch for the Airbus.
Some crews would have loved to have one :
http://www.pprune.org/tech-log/502079-a330-a340-ead-aoa-probes.html

More on the new Gulfstream :
GULFSTREAM INTRODUCES NEW AIRCRAFT FAMILY | Gulfstream Newsroom (http://gulfstreamnews.com/news/gulfstream-introduces-new-aircraft-family)
The industry-first ACSs (active control sidesticks) offer enhanced safety and situational awareness over passive sticks through tactile feedback. With electronic linking of the ACSs, the pilot and co-pilot can see and feel each other’s control inputs, which helps improve pilot coordination in the cockpit.
“The active control sidesticks enable both pilots to be consistently on the same page, enhancing safety”
Common sense, but Airbus didn't think so ...

DozyWannabe

18th Oct 2014, 01:22

You still did not get what happened to that 777
http://www.pprune.org/7022213-post1332.html
Bad data got through to the EFCS and AP, causing an uncommanded pitch up and climb.

You say:
For the 777 the AP then the pilot followed unrealistic FD commands.
The report :
http://www.atsb.gov.au/media/24550/aair200503722_001.pdf

says different. More to the point, it doesn't alter the fact that the bypass mode was not used by the crew.

And you still did not get what would be the purpose of a DIRECT switch for the Airbus.
Some crews would have loved to have one :
I don't see anything in that thread from crews clamouring for such a switch - just the same old arguments we've always had.

More on the new Gulfstream :
...
Common sense, but Airbus didn't think so ...
"Common sense" is your opinion - I have yet to see any evidence that confirms or refutes that position. Furthermore this is just marketing bumph - they've decided to backdrive their sidesticks, therefore they're hardly going to say that doing so might be pointless. I'm not going to waste my time enumerating the accidents in which the linked yoke position was nevertheless ignored/disregarded, nor those in which the supposedly superior "tactile" stick-shaker was also ignored/disregarded - but the record speaks for itself.

Cool Guys

18th Oct 2014, 06:09

Originally Posted by Dozy
I have yet to see any evidence that confirms or refutes that position

This is your opinion. In some other peoples' opinion AF447 is one piece of evidence.

is just marketing bumph

I doubt that. I am sure there are some very smart pilots in Gulfstream that consider tactile feed back is superior

I'm not going to waste my time enumerating the accidents in which the linked yoke position was nevertheless ignored/disregarded, nor those in which the supposedly superior "tactile" stick-shaker was also ignored/disregarded - but the record speaks for itself.

What about enumerating the numerous instances where tactile feed back saved the day... oh, you cant, because by nature they were non events, so there is no record.

jcjeant

18th Oct 2014, 09:03

Embraer:
Embraer?s big bet on its largest airplane yet | Leeham News and Comment (http://leehamnews.com/2014/10/13/embraers-big-bet-on-its-largest-airplane-yet/?utm_source=dlvr.it&utm_medium=twitter)
Flight laws are similar to the Airbus FBW but with two distinctions: throttles are back-driven and the side-sticks are electrically inter-connected, meaning a instructor can see on his side-stick and feel what the trainee is doing with his side-stick. The FBW goes in and trims out the yaw imbalance after the loss of an engine after a slight delay. The trim delay is deliberate so that the pilot is fully aware that he has lost an engine and which side is affected. It was easy to fly the KC-390 with all engines operative or when one engine was inoperative.

DozyWannabe

18th Oct 2014, 16:32

This is your opinion. In some other peoples' opinion AF447 is one piece of evidence.
Fair enough, but I'm not the only one of that particular opinion either.

I am sure there are some very smart pilots in Gulfstream that consider tactile feed back is superior
Just as there were very smart pilots at Airbus who felt differently.

What about enumerating the numerous instances where tactile feed back saved the day... oh, you cant, because by nature they were non events, so there is no record.
I think you're missing the cut of my jib. I'm not saying tactile feedback is never beneficial, I'm just illustrating the point that it doesn't always make a difference (and furthermore that there have been cases where connected controls have hindered things).

You pays your money and takes your choice, but it's foolish to state that one method is definitively better than the other.

rudderrudderrat

18th Oct 2014, 18:51

Hi DozyWannabe,
More to the point, it doesn't alter the fact that the bypass mode was not used by the crew.
It was a good job that this alert crew invented their own "bypass mode switch".
Link (https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCEQFjAA&url=http%3A%2F%2Fxa.yimg.com%2Fkq%2Fgroups%2F23414347%2F4910 20246%2Fname%2FA320-A330-A340-OEB45-BlockedAOAprobes.pdf&ei=VLxCVIKpI6H17AahoIDgAg&usg=AFQjCNHgyGTq9Fprqwr2POfbnsmnotRJ9A&sig2=Si3gbxb6wbhuyRrblG4ddA&bvm=bv.77648437,bs.1,d.d2s)
see slide 7

"With pitch attitude continuously decreasing, PF reacted by applying permanent (for about 20s) sidestick order in the full backward position.
• Pitch angle continued to decrease and AC to descend"

infrequentflyer789

18th Oct 2014, 22:32

And you still did not get what would be the purpose of a DIRECT switch for the Airbus.
Some crews would have loved to have one :

I have always wondered why there wasn't one - there is no engineering difficulty as it is there on test flights (they always start test flight program in direct and then add FCS laws in).

I wonder if it has to do with certification, in response to one of my previous posts some have suggested that the reversion laws are not tested in compliance with the regs (and special conditions) but only as failure conditions. If so, maybe putting it there as a pilot option makes the certification more complicated. Note: that would all be stupid IMHO, but then I thought that each reversion law would have meet certification standards in itself.

If it was there, I am not sure it would help much though - the Boeing one is apparently little used if ever - and it might just become another way to put blame back onto the pilot. After all (thinking about LOC with a flyable aircraft), if the crew punches out to direct law and still crashes it will be their fault, while if they could have done but didn't, and it might have helped, then same again.

More on the new Gulfstream :
GULFSTREAM INTRODUCES NEW AIRCRAFT FAMILY | Gulfstream Newsroom (http://gulfstreamnews.com/news/gulfstream-introduces-new-aircraft-family)

Common sense, but Airbus didn't think so ...

I think you are being unfair on them there. I am pretty sure that Airbus at the time thought that contemporary engineering technology wasn't up to it. I have seen other research that concludes that that was still the the case some years later. I am pretty sure that what Airbus thought was that the benefits of sidestick and C* fbw would outweigh that disadvantage. In terms of accident rates, I would suggest that time has proved them correct in that (or at least that there was no significant overall safety disadvantage).

The developer of the new sidestick is BAE Systems, by the way, and if you go back 30 years, guess which commercial aircraft consortium they were part of ? What is happening with sidesticks now is exactly what Airbus did then - contemporary military tech is being migrated to civil, but when Airbus did it, contemporary was passive.

At some point Airbus will need to weigh catching up with the rest of the world against maintaining interface compatibility across its model range (which it has made a big selling point) - perils of being a first-mover. Boeing will need to too, because if I had to bet I'd say the future pilot interface looks like (better) sidesticks, fbw, and moving thrust levers - and neither A or B called it totally right.

Most interesting thing (and it is difficult to judge for a few pictures) for me is that the active sidestick units look to be physically smaller than the Airbus passive spring units - probably due to major advances in actuator tech. If so, given that the rest of the puzzle is software, a retrofit might even be possible - from an engineering POV, I doubt it ever will be from commercial.

_Phoenix_

19th Oct 2014, 01:37

the Boeing one(DIRECT Switch) is apparently little used if ever - and it might just become another way to put blame back onto the pilot

Would be something new to hear about Airbus accused of an accident or incident. Isn't it?
Apparently nobody can touch the arrogant nose that keeps pitching up
VqmrRFeYzBI
uZdk6Td6DNc

gums

19th Oct 2014, 02:04

Let's face it, Doze is a die hard engineer that designs and implements systems that may or may not have been tested or designed by the end user - the pilots. "Works according to the spec". So I throw the B.S. flag.

Many features of the 'bus system seem very logical and could/should reduce workload ( whatever that is for pilots). However, there comes a time or situation that the basic flight controls and aerodynamic response to control inputs and such must revert to basics that we saw a hundred years ago.

I do not feel we should go to a "direct" law post haste, as even that requires electrons from the flight controls to the control surface actuators. But the plethora of modes and sub-modes on the 'bus puzzle me. I can understand the argument that the system would degrade gracefully. But the reality is some things work, some don't and some can't. Sheesh. Give me a back up mode I can trust and not go thru ten pages of manuals, footnotes and .....!!

Tust me, I am not a dinosaur. I flew the first FBW jet produced in significant numbers ( no offence to Concorde folks). We learned a lot about the failures of the "engineers" that could not fathom the unplanned tests we normal pilots would expose to the jet to, heh heh.

I enjoyed the opportunity to fly the neat little jet, and I knew deep down that we would find some things that the engineers never thought of. And we did.

DozyWannabe

19th Oct 2014, 06:14

It was a good job that this alert crew invented their own "bypass mode switch".
Right - though technically that was a drop to Alternate Law, not Direct. The crew observed Rule No. 1 - "know your aircraft".

I have always wondered why there wasn't one
Because as originally designed and certified, it's not necessary. See my previous post re: B777 force feedback.

I am pretty sure that Airbus at the time thought that contemporary engineering technology wasn't up to it.
I don't think it was a case of the tech not being up to it, so much as it would effectively double the complexity of the required software systems and add complexity elsewhere to little real benefit - again see previous posts re: fully hydraulic controls - two pairs of hands on the controls wouldn't make any difference in the way it used to.

@_Phoenix_ : The A310 has a completely different flight control system, and furthermore the pilot in the Orly incident pulled up in response to the SW. The XL888 accident grew from improper cleaning/maintenance procedures causing failure of the AoA vanes.

Let's face it, Doze is a die hard engineer that designs and implements systems that may or may not have been tested or designed by the end user - the pilots.
You misjudge me - and furthermore ignore the fact that the Airbus FBW control system was designed by pilots.

...must revert to basics that we saw a hundred years ago.
Why? I don't understand this need to hold aviation development hostage to a de facto standard that dates back to (and is derived from the limitations of) pre-WWII technology. Among other things, we've been to the moon and back eight times since then (in a lander that used passive sticks, no less).

We learned a lot about the failures of the "engineers" that could not fathom the unplanned tests we normal pilots would expose to the jet to, heh heh.
Fair enough, but remember that the lead pilot engineer on the A320 project was the test pilot who succeeded D.P. Davies (of "Handling The Big Jets" fame) at the ARB.

roulishollandais

19th Oct 2014, 09:45

Dear gums, your post is the first specification for every aeroplane. Pilots to survive need to live. Your important message facing a large business is a life's philosophy, and the message of your Country choices, success, before, during and after WWII and how Freedom may change the World. Not only the "free" (? I doubt) decision of a little team, or one pilot put alone, but the freedom degrees let to every pilot in emergency in the sense of mechanic laws, and freedom in the human natural sense, and confidence in well selected, taught, trained pilots who are considered as Men, not throwable things designed by stats and without ejection seat!
Thank you so much, gums.
:D

Cool Guys

19th Oct 2014, 14:51

Hi Gums,
While I feel quite humble comparing my experience to your time developing the F16 FBW, I have to agree with your sentiment regarding the complexity of the FBW law degradation. With one of my first projects as a young engineer I happened to be working with an old guy (who would be deemed a dinosaur in PRRUNE) who said to me “Whatever you do keep it simple” as he proceeded to literally throw in the bin an extraneous controller (PLC) that had been causing us no end of trouble. I have applied this for the last 30 years and it has never let me down. This does not mean “don’t use automation” but it means “do not over use automation.”
While I haven’t flown a modern jetliner from what I have read the automation seems excessively complex, and I’m not referring to just AB products. Complex things confuse people and confused pilots don’t fly planes very well. Yes, I know pilots should be trained adequately but training can fail just like a pitot tube.

gums

19th Oct 2014, 14:59

No problem, Doze. I feel we both appreciate the opportunity to exchange opinions and lifetime experiences regarding engineering. I was fortunate to be on both ends of the process as an end user and a designer/tester on the other end.

My main concern is we seem to be assigning more and more "operation" to the machines at the expense of human judgement and decision-making and experience. How do we "train" a machine to handle an event that has not been anticipated by the design engineer? And worse, how do we design a machine to anticipate unusual human actions and "protect" them ( God, how I hate that term, and prefer "limit")

Gotta think about this more, so gone for now......

Cool Guys

19th Oct 2014, 15:30

I don't understand this need to hold aviation development hostage to a de facto standard that dates back to (and is derived from the limitations of) pre-WWII technology.

This is a very good question. Perhaps because the “de facto standard” is based on the laws of physics which are constants, people can learn them starting from primary school, become familiar with them in many areas of life, discuss them freely, they are the same for newbies and dinosaurs, they remain the same from one century to the next, they are natural. The more software you get between the pilots physical senses and the control surfaces the more it flies based on how some one believes it should fly. This is very fluid, the persons inventing it may not document it adequately, other inventers may disagree with it and design theirs differently, it can change between America and Europe and from year to year, as technology changes people may discover it actually is not the best way and a change is necessitated. It may actually not be the best way of controlling the plane.

rudderrudderrat

19th Oct 2014, 18:11

Hi DozyWannabe,
Among other things, we've been to the moon and back eight times since then (in a lander that used passive sticks, no less).

I think you'll find there was only one control stick - hence active feed back not necessary. Also the Lunar module is unstable in flight and must be computer controlled - hence no "Direct Law" so side stick control is a perfect solution.

the moon - Why did Armstrong pilot the LM, when Aldrin was tasked as Lunar Module Pilot? - Space Exploration Stack Exchange (http://space.stackexchange.com/questions/4325/why-did-armstrong-pilot-the-lm-when-aldrin-was-tasked-as-lunar-module-pilot)
"According to Tales From The Lunar Module Guidance Computer by Don Eyles, Armstrong and Aldrin never switched places during the LM powered descent and landing phase. Armstrong was on the left side of the LM cockpit where the manual controls were, and Aldrin on the right and responsible for working the DSKY (Lunar Module Display and Keyboard Unit), essentially instructing the flight computer."

More fascinating info on the software programming here:
Apollo 11 and Other Screw-Ups (http://www.doneyles.com/LM/Tales.html)

_Phoenix_

19th Oct 2014, 22:47

@DozyWannabe,
and furthermore the pilot in the Orly incident pulled up in response to the SW. The XL888 accident grew from improper cleaning/maintenance procedures causing failure of the AoA vanes.

Are you kidding me? Watch again the video. It includes the actual CVR. The Stall Warning came on at 1:06, during recovery phase!!! No stall warning during vertical climb or at peak point.
Funny thing, the aerobatic maneuver starts at 0:10 with captain's question : Hé ! qu'est-ce qu'il fait !?
see CVR transcript, page 53 of report below, the stall warning at 10h:44m:44s
http://www.bea-fr.org/docspa/1994/yr-a940924/pdf/yr-a940924.pdf

https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/info/all_infos/media/2008/FSAT9513.pdf

About XL888, of course, if isn't the pilot then must be the mechanic...

CONF iture

20th Oct 2014, 03:26

I have always wondered why there wasn't one
We have to remember what is the Airbus leading concept :
Our technology is here to save the pilot from his own mistakes, not the opposite ...

I think you are being unfair on them there. I am pretty sure that Airbus at the time thought that contemporary engineering technology wasn't up to it.
I don't think to be unfair, had it been really important for them, they still would have had the possibility to adopt the coupled control columns we saw a few years later on the 777.
Now, it will be interesting to follow up on the Airbus position after the Gulfstream and Embraer announcements ...

Right - though technically that was a drop to Alternate Law, not Direct. The crew observed Rule No. 1 - "know your aircraft".
You are totally beside the point - the crew applied an unpublished procedure to take back control over a mad system that was supposed to protect them.

_Phoenix_

23rd Oct 2014, 00:35

Winnerhofer,

In alternate law automatic pitch trim is available.
The THS was moved at constant rate of 1deg/6 seconds, SW online

rudderrudderrat

25th Oct 2014, 09:07

Hi CONF iture,
Now, it will be interesting to follow up on the Airbus position after the Gulfstream and Embraer announcements ...

NBAA: Safran reveals active sidestick development project - 10/22/2014 - Flight Global (http://www.flightglobal.com/news/articles/nbaa-safran-reveals-active-sidestick-development-project-405051/)
http://www.safran-na.com/spip.php?article3249&lang=en

"The dual sidesticks are also electronically linked, so the co-pilot’s stick imitates the movements of the pilot’s control inputs. In a sense, it reintroduces the aircraft feedback loop normally associated with mechanically-linked control systems into a new generation of fly-by-wire aircraft.

At the moment, Sagem has not signed up any customers, although it has briefed Dassault, Airbus, Boeing and the French air force, says Phillippe Arnaud, senior vice-president of sales and marketing for Sagem."

"Incorporating a number of proprietary Sagem innovations, this side stick controller features very high dispatch reliability, a robust design that stands up to all types of contingencies and an optimized architecture supporting the real-time adjustment of force feel laws. Thanks to its stick shaker / Stick pusher function and the fine synchronization between all side stick units, this system greatly facilitates pilot/co-pilot coordination and the management of stressful situations."

Clandestino

25th Oct 2014, 21:34

Done .. JTThanks! :ok:

IIRC OG suggested that the system will then 'see' the g is not as commanded and then continue to increase elevator deflection to eventually match the commanded or available g for a much lower speed than 330 KIAS. (My observations showed some number of seconds involved)While precise and correct answer could be provided only by Airbus FBW experts - and I strongly suspect any of them reading AF447 threads must be howling with laughter - I find such interpretation quite implausible because:

1. certifying the FCS that significantly increases your pitch rate over couple of seconds while holding the constant stick deflection would be waaay too much even for the most corruptostupid aerogovernmental people inhabiting the imagination of PPRuNe's resident Airbus bashers.

2. From my 320 initial training I remember that FBW was trying to mask the fact it was losing control authority as much as it was practicable. Stabilizer lost or one elevator on vacation with other limited to 50% throw not to overtorque the empennage? No problem or perceptible difference as long as the speed was up. Maneuvering for approach with two hyds shot up felt normal enough but when abrupt maneuver at low Q needed to be performed, i.e. last moment go-around, it tended to turn quickly into wrestling match with the aeroplane.

3. Final report says:

In alternate 2 law, the longitudinal control law remains a load factor law and the
lateral control law is a direct law. In the specific case of alternate 2B law, some
coefficients used in the longitudinal flight control law become speed-independent
and are set for the maximum speed for the aeroplane configuration (330 kt in clean
configuration). This hardly modifies the behaviour of the aeroplane in comparison
to normal law, but can nevertheless induce an unusual response dynamic when the
aeroplane has an abnormally low speed for the configuration.

Was the risk adequately appreciated?Yes. Thirty cases with not as much as scratch to anyone or anything were appreciated enough... till the 20-20 hindsighters took over.

Based on the limited evidence available to us, which is some of the CVR transcript, I'll suggest that neither Bonin nor Robert ever got to the "frightened" stage. They remained in the "what is going on?" stage, though Robert seems to have been more aware of the aircraft's flight condition than Bonin, coupled with frustration and confusion. Oh, they quickly went from frightened to completely shocked. They were climbing with 7000 fpm, above their performance ceiling and could not connect the fact with blaring stall warning. It's textbook panic - very unlike the Hollywood one.

"...over the ocean" makes no difference, neither should night-time if one is an instrument pilotWoCL is a four lettered word.

The question is WTH was this not carried over to Alternate laws??? Because ALTN laws are made (inter alia) for cases of air data getting screwed up! It would be no good if false data unnecessarily rob the pilot of control authority. No matter what John Cashman, Bernard Ziegler or CONF iture might say, in FBW Airbi pilot still has the ultimate responsibility to recognize the problem and more than enough control to solve it properly.

The manuals are comparable to instruction manuals without comunicating the basic knowledge layer behind those instructions. How many times have I posted the disclaimer from the very beginning of Airbus manual in previous AF447 threads? IIRC at least three.

The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player.Not in AF447 case as it didn't pitch up with neutral stick.

So, we are back to having something saying "That's enough mose-up THS, boys and girls - if you really want more push this over-ride button" - what is wrong with the concept?Maybe not completely wrong but surely it's spectacularly incongruent to bash Airbus FBW for taking away the full control authority from pilot and then cry: "Help automatic trim cut-out, save us from ourselves!"

Boeing's Synthetic airspeed, Airbus BUSS, safe USN's AoA, or Klopfstein's old inertial HUD....can not alter the fact the unreliable airspeed procedures work when applied even with no alpha gauge, HUD, BUSS or whatever.

Correct would be the airplane will maintain a loadfactor of 1g. It would be correct except for the fact it isn't.

That mindset "set the pitch and it will stay there (and go there) might have influenced Bonins actions with the SS.So, he was desperately trying to achieve 20 degrees pitch on cruise level?

Big, vulnerable ocean liners of the sky that are pretty much optimised to point directly into a high mach airflow, and stay there.'Tis a miracle thousands of them keep themselves pointed into high mach airflow day after day, year after year and survive despite their vulnerability.

I do not feel we should go to a "direct" law post haste, as even that requires electrons from the flight controls to the control surface actuators. But the plethora of modes and sub-modes on the 'bus puzzle me. You are puzzled because you have never tried them, in the sim at least, but rather built up your misunderstanding of Airbus FBW on usual PPRuNe mix of prejudice, ignorance and outright libel.

Safran’s exhibit featured a two-seat cockpit simulator with sidesticks on either side. Unlike passive sidesticks found commonly on Airbus commercial airliners, the active system integrates a digital feedback loop. It allows pilots to feel how the aircraft responds to control inputs. As control forces climb higher, for example, the stick feels heavier. Over-speeding the aircraft triggers a vibration in the control stick to warn the pilot.Stickshaker as overspeed warning.... now that makes almost as much sense as 12 threads on AF447 here.

Now back to our usual reaction eliciters.

jcjeant

26th Oct 2014, 06:01

Clandestino
Now back to our usual reaction eliciters.
I will be the first :)
Yes. Thirty cases with not as much as scratch to anyone or anything were appreciated enough... till the 20-20 hindsighters took over.Indeed but incomplete ...
30 cases with different A330 model as the 200 (this is a difference between 200 and other when AP disconnect due to bad speed reading by Pitot tube)
Not in AF447 case as it didn't pitch up with neutral stick.Indeed he pitched down when AP disconnected (virtually indicated on instrument)
30 cases with no scratch by luck (pilots not followed the procedures in force)
Luck = not a factor of security
How many in the 30 cases happened at night ? (different environment)
What about the Pitot problem ? (ice problem) well appreciated or not ?
till the 20-20 hindsighters took over. 30 cases = also hindsight .. no ?
Why the case 31 was needed ?

roulishollandais

26th Oct 2014, 06:08

...and add a Nz control on the the top of the stick like gums'jet (controllability),to don't be glued in nz=1 by the THS, and improve he observability of the trim wheel ...

roulishollandais

26th Oct 2014, 06:13

1 case for 30 is a very very high rate and it could happen the first time

Owain Glyndwr

26th Oct 2014, 07:58

Originally posted by Clandestino

Quote:
Originally Posted by Owain Glyndwr
The question is WTH was this not carried over to Alternate laws???

Because ALTN laws are made (inter alia) for cases of air data getting screwed up! It would be no good if false data unnecessarily rob the pilot of control authority. No matter what John Cashman, Bernard Ziegler or CONF iture might say, in FBW Airbi pilot still has the ultimate responsibility to recognize the problem and more than enough control to solve it properly
OK, my original wording was not very clear. What I had in mind was that in alternate this THS movement inhibition could be triggered by stall warning rather than alpha protection. Only AOA data involved there, no false airspeeds; and I can see no good reason to trim into a stall situation.

rudderrudderrat

26th Oct 2014, 08:43

Quote:
Originally Posted by gums
The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player.
Clandestino
Not in AF447 case as it didn't pitch up with neutral stick.

Better tell BEA that they have this analysis wrong then.

Final report page 187,
"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."

CONF iture

26th Oct 2014, 14:48

Now, it will be interesting to follow up on the Airbus position after the Gulfstream and Embraer announcements ...
Not Airbus yet for now but Dassault :
NBAA: Dassault's Trappier pokes fun at rival Gulfstream - 10/22/2014 - Flight Global (http://www.flightglobal.com/news/articles/nbaa-dassault39s-trappier-pokes-fun-at-rival-gulfstream-405100/)
“And we are pleased to see that our friends in Savannah have finally decided to move towards sidesticks.”
But Trappier obviously avoids mentioning how the sidestick concept adopted by Gulfstream is different ...

It would be no good if false data unnecessarily rob the pilot of control authority
1- In which way not to have auto trim under manual flying rob the pilot of control authority ... ?
2- False data unnecessarily rob the pilot of control authority here (http://www.caa.co.uk/docs/33/20121204EASAAD20120258E.pdf) but you're nowhere to comment.

gums

26th Oct 2014, 15:13

I agree with the report. You just have to define "stability".

In "normal" the AoA/stall protections are in place. But as the report says, in that particular alternate law that night ( or anytime) there was no AoA/stall protection, but the system still tried to achieve one gee corrected for pitch attitude, regardless of speed or AoA. In other words,the plane has no significant positive static stability that we normally think of.

It doesn't have a conventional "trimmed" state until in direct law and that's because once there it does not keep trying to reach the default gee and its basic aerodynamic design takes over, which apparently is damned good and exhibits good static stability and exceptional directional stability ( if you ask me). It tries to reach the trimmed AoA according to its c.g., center of pressure and the state of all the control surfaces. Get slow and it will nose over and get fast it noses up.

Hope I am making my position clear, and it was harder us to duplicate the AF447 scenario since our pitch law included a stong AoA limiter - 15 degrees at 9 gees then almost linear function until 27 degrees and 1 gee. If we got real slow in level flight it would eventually nose over to maintain the trimmed gee, not an AoA. With gear down, we added the AoA to the mix and could actually trim for an AoA.

_Phoenix_

26th Oct 2014, 21:52

Originally Posted by Clandestino
While precise and correct answer could be provided only by Airbus FBW experts - and I strongly suspect any of them reading AF447 threads must be howling with laughter

I only agree with first sentence

It's nothing to laugh about, but answers must be drawn

Hé ! qu'est-ce qu'il fait !? here
Ja it's pitching up all the time!!!
But what is happening? here

waaay too much even for the most corruptostupid aerogovernmental people inhabiting the imagination of PPRuNe's resident Airbus bashers
...be careful not to sprain your tongue

Originally Posted by Owain Glyndwr
... in alternate this THS movement inhibition could be triggered by stall warning rather than alpha protection. Only AOA data involved there, no false airspeeds; and I can see no good reason to trim into a stall situation.

Yes, it make sense. For all laws, THS function must include AOA. It's inadmissible THS's roll back under stall warning and AOA over 40deg.
THS position instrument and AOA indicator must be part of any cockpit instrumentation, with improved awareness for extreme positions.

jcjeant

27th Oct 2014, 22:37

AF447 : un accident d'une extraordinaire complexité (http://avia.superforum.fr/t1517-af447-un-accident-d-une-extraordinaire-complexite#50938)
certification:
BEA:
The A330 meets the requirements of the regulations in force at the time of application for the license type, namely the JAR 25 change 13 or 14 and the special conditions issued by the DGCA.
...
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.

ECAM on the AF447, for 2 minutes and 39 seconds there was no message NAV ADR DISAGREE or NAV ADR DISCREPANCY.

It is these messages that moving towards doubtful IAS, procedure adapted to the situation

A33Zab

29th Oct 2014, 00:09

ECAM on the AF447, for 2 minutes and 39 seconds there was no message NAV ADR DISAGREE or NAV ADR DISCREPANCY

an ADR is rejected by the EFCS if the CAS difference > 16kts for 10s compared to the median value.
The remaining ADRs are compared to the average value > 16kts for 1s.
If true then the NAV ADR DISAGREE is set.

Since the message was only set after 2 min 39s this means that the above values were not exceeded before.
Remember the RH display was switched to ADR 3 at 02:10:40.

NAV ADR DISCREPANCY does not exist.
a DISCREPANCY message is preceded by a parameter, e.g. NAV IAS DISCREPANCY or NAV AOA DISCREPANCY.
The availability of this message (IAS) depend of the installed FWC standard.

jcjeant

29th Oct 2014, 07:39

So we agree that nothing indicated a speed value problem on ECAM before 2 min 39s after the AP disconnected

And JAR 25
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.
Is 2 min 39S is a acceptable delay for indicate such problem ? (speed reading)

A33Zab

29th Oct 2014, 10:03

Within that time period of 02:39, during the 'STALLSTALL' ADR1 and ADR2 were consistent and accurate for at least 1:04s.

means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.

They already noticed the speed difference because they switched RH display to ADR 3, unfortunately the most deviating and faulty source at that time.
i.e. they took action before the announcement.

Is 2 min 39S is a acceptable delay for indicate such problem ? (speed reading)

Do you consider 16kts difference for 10s from median value acceptable?

Do you agree that an aircraft, which purpose is to transfer humans, should always be modified to the highest standard?

jcjeant

29th Oct 2014, 11:21

Do you consider 16kts difference for 10s from median value acceptable?
I can only answer by :
Do you agree with JAR 25 or not ?
JAR 25
In particular, they state that:
... Systems and associated alarms must be developed to minimize the risk of error by the crew;
means of information must be set up to alert the crew of the occurrence of a failure and enable them to take appropriate action.

A33Zab

29th Oct 2014, 12:10

Do you agree with JAR 25 or not ?

I do agree, it doesn't say to prevent a crew to make inappropriate actions.

There are 7 lines of ECAM messages in view, in priority NAV ADR DISAGREE is only #114th.

#48 F/CTL ALTN LAW (PROT LOST) was always in view, (PROT LOST) = NO PROTECTIONS = keep away from limits!

Audible STALLSTALL means something and requires an appropriate action.

jcjeant

29th Oct 2014, 14:04

roulishollandais

30th Oct 2014, 03:11

The abiliy of pilots to be concerned with the good priorities is overloaded in flight by sofware variety and imagination. Their world of lift gets a cold untasted soap impossible to drink.

A33Zab

30th Oct 2014, 09:36

We know that the failure was Pitot tubes
The AP was alerted of this failure and so he disconnected
The FBW system was alerted and so go in alternate law
Is the crew was alerted of this failure (for take appropriate actions .. so follow the procedure in force for IAS) and when in the time scale of the event ... ?

The AP in FMGEC was disconnected by 2 by 2 comparison of the speed data from ADIRUs.
The PCPCs reverted to ALTN LAW by comparison of the median/average value of the speed data from ADIRUs.

The crew is alerted by comparison of the speed displays (NAV IAS DISCREPANCY) if the a/c was updated to the highest standard available (we know it is was not!).
The message NAV ADR DISAGREE didn't show up in phase 1 of the event because -unfortunately- it didn't exceed the delta/time limits.

This crew at that time needed to do the comparison themselves and take the appropriate action (pitch and power) like it was done for many years.

An exact failure description is simply not feasible, even the ADIRUs don't know the PITOT icing, the only know (by comparison) that Pt is not equal.
Above that all pitot failures will lead to the same appropriate action: pitch and power.

jcjeant

30th Oct 2014, 10:28

An exact failure description is simply not feasible, even the ADIRUs don't know the PITOT icing, the only know (by comparison) that Pt is not equal.
Above that all pitot failures will lead to the same appropriate action: pitch and power. So we can agree that this system no comply with JAR 25

Above that all pitot failures will lead to the same appropriate action: pitch and power.

Indeed .. when pilot know it's a Pitot failure

A33Zab

30th Oct 2014, 10:46

No we don't agree, pitot failures are clustered and result in NAV ADR DISAGREE (if value and time constraints are exceeded).
As such it is certified by the authorities so it complies to JAR 25 or FAR equivalent.

Name one A/C manufacturer who do announce PITOT ICING by means of message, warning light or such.

jcjeant

30th Oct 2014, 15:28

Name one A/C manufacturer who do announce PITOT ICING by means of message, warning light or such. Well .. it's not really a argument
If not all follow a regulation or make respect a regulation that does not mean they are therefore correct

JAR 25
"Systems and associated alarms" must be developed to minimize the risk of error by the crew

Pitot is not a new technology .. icing and deicing of Pitot is not new knowledge
I think this was enough time for find a system for alert the crew that a Pitot is out of use .. by audible or visible alarm

A33Zab

30th Oct 2014, 19:55

Well .. it's not really a argument

It would be very quiet in the air if they all fail to comply to your definition of JAR 25.

Pitot is not a new technology .. icing and deicing of Pitot is not new knowledge

True and as just being a simple heated tube it can ice up upstream the drain hole; downstream the drain hole and at the drain hole itself.
All will result in 3 different erroneous Pt measurements.

I think this was enough time for find a system for alert the crew that a Pitot is out of use .. by audible or visible alarm

If the heater fails this is announced otherwise freezing is only a temporary issue.

Apart from icing it could be blocked and/or damaged by other means (bugs/birds/radome/mechanical damage).
It would need additional sensors (which are pronounced to fail by itself due to the severe environment) and computers to supply an reliable specific PITOT failure message, and - once again - all failures would lead to Pitch and Power.

DozyWannabe

31st Oct 2014, 02:59

In my 42 year career as first a fighter pilot, than an airline pilot, and then a corporate pilot I encountered multiple airspeed indicator problems.
Er....

Winnerhofer/Join Date: Oct 2013/Location: Wengen/Age: 44/Posts: 281
I feel fairly certain that I'd probably have read about someone selected to fly fighters in the Schweizer Luftwaffe at the age of two. Either your profile age is dodgy, or there's something else fishy going on...

A computer did not cause this accident- the copilot did...
While I agree that this accident relates more to human factors than technology (despite conceding that there were contributory technological factors), the above point is simply not accurate. As with all aviation accidents there was a complex chain of events involved, and seeking to determine "blame" gets us nowhere.

Basic CRM doctrine says that the crew were supposed to act as a team - working together to solve problems, and they did not. AF - aware that their A330 fleet used Thales AA probes - were supposed to pass relevant info regarding UAS procedures to their crews and they did not. Airbus may have dropped a failsafe point on THS movement between the A320 and A330 design. The only important question is why.

_Phoenix_

31st Oct 2014, 04:09

Originally Posted by DozyWannabe>

Either your profile age is dodgy, or there's something else fishy going on...
...either he retired two years ago, at age 42 of career, either there is a slight dysgraphia symptom

Airbus may have dropped a failsafe point on THS movement between the A320 and A330 design. The only important question is why.

Here you're talking, so why? Why the THS and AOA indicators are not mandatory?

roulishollandais

31st Oct 2014, 06:45

Usual Winnerhofer's quotation signs and ref mssing
Problem!

CONF iture

31st Oct 2014, 12:20

No we don't agree, pitot failures are clustered and result in NAV ADR DISAGREE (if value and time constraints are exceeded).
Apparently value and time constraints have been exceeded long enough to command the AP and A/THR to quit and the FCS to switch to a bizarre ALTN LAW but not to announce the reason why, be it NAV ADR DISAGREE ... !?

This crew at that time needed to do the comparison themselves and take the appropriate action (pitch and power) like it was done for many years.
That's far to easy to state as you were not on the hot seat.
This crew, as anyone who actually fly the thing, just needed the good honest briefing (http://www.pprune.org/7450265-post576.html) that Airbus missed the opportunity to publish ...

TTex600

1st Nov 2014, 00:41

Winnerhofer, read the previous umpteen thousand posts before coming to the conclusion that the pilots were incompetent, please!

Now back to looking for Spaceship Two info.

alf5071h

1st Nov 2014, 01:25

jcjeant, considering the various regulations; a requirement for an indication of failure is not the same as an indication of system state. The pitot did not ‘fail’, the problem was that the data was not reliable.
Similarly before considering the ‘risk of error’, what is an error? A system should be designed to minimise risk, but it cannot ensure that there is no risk, nor any error.

Winnerhofer, irrespective of your experience with ASI problems, what was the experience in unusual ice crystals. And please do read a HF reference on the limits of human performance.

As per CONF iture’s link, Airbus had associated the pitot deficiency with ice crystals. Unfortunately, the manufacturer, regulator, operator, or all, continued to focus on the pitot system as the threat (flight with UAS) instead of the conditions which triggered the system problems.
Looking at this accident with hindsight, and with a ‘safety 2’ view (resilience – the human as a help not a hazard), a backward search can identify a situation where a crew’s normal behaviour could have avoided the pitot ‘failure’ situation – by avoiding ice crystals / cbs. The normal everyday behaviour, opposed to LoC recovery, would be using Wxr to deviate around cbs, with a greater distance margin due to an awareness of the ice crystal threat.
Comparing flight paths with other aircraft this operation might be questioned, as might the crew’s knowledge of the ice crystal threat as above.
Thus the safety weakness was with an incorrect choice of threat, possibly aided by considering the human as a hazard, requiring refresher training.