Did it disappear by law change or just get pushed out of view by other ecam messages ? Same effect, different reason. [I have vague recollection it was the latter, but could be wrong].

FCOM reference - section on abnormal attitude flight law. But you know that :)

The real issue is how you went into that law in sim, but DW didn't and 447 didn't.

Based on what I've read:

• 447 stayed in Alt2 because triple ADR failure meant it wouldn't switch based on airdata conditions (and g-load conditions weren't breached).
• Your sim went into abnormal law based on AOA following dual (not triple) ADR fail
• DW sim again not triple ADR failure, but I'm not sure AOA got high enough to trigger abnormal law from what he's written.

Now, can anyone provide FCOM reference for the triple adr fail caveat on abnormal law entry conditions.... I don't think it's in there.

And yes, not having "use man pitch trim" displayed in abnormal law is not logical to me either. In fact, I'm not sure why abnormal law is there at all - can't see why not use direct law for this purpose (abnormal attitude recovery). What extra authority does abnormal law give over direct ?

Green dot is not minimum clean speed. Green dot is L/D max. Considering this basic point, I fail to find it worth my time to further discuss this, or the AB with you.

Because you bring experience into the discussion, I've well more than three times the time you mention and have never NOT flown an aircraft that could simply kill me if I stalled them. But then again, I've intentionally stalled many a DC9 and am still here to tell the tale. Good day.

That is what the engineers get their pay for...making tough decisions on system design.:}

I don't design circuits for a living or write software, but I've done a fair amount of root cause analysis on defective equipment and have had pretty good exposure to same over the last 55 years. The following is a gut feeling hypothesis only so take it with a healthy dose of skepticism:

Once all 3 airspeeds become corrupted from high AOA, if any part of the primary or supporting calculations for operation of the trim rely on airspeed or its derivatives, then operation of the trim becomes compromised. Without looking at an actual complete logic diagram of how the system operates, this is difficult to analyze.. Something as mundane as a calculation of how much torque the hydraulic drive motors must generate to drive the THS (just for example) can have airspeed components in it that crash the whole logic chain for THS drive. Any reasonable software would then have error handling options for such an error. Generally the safest option would be to halt all automatic motion on error.

Now I could be seriously wrong here, but something stopped the THS from trimming nose up before it actually hit the end limits. If it was an error handling routine, it might stop nose down trim as well until some reliable airspeed information appeared. In this case you might effectively be in "Direct Law" without an indication, at least as far as THS trim goes. Elevator motion would then still be Alt2 though.

Machinbird,

without getting into the realism of your ideas - during their whole descent, they never even got to down elevator, so nothing weird is needed for the ths not to move...

Yes, the elevator never made it past neutral, but that mayonaise stirring stick did for a large number of instances. So did the LH seat stick.

You couldn't do that kind of useless rapid motion with the old irreversible hydraulic driven- cable controlled flight controls of yesteryear. The actuators generally had to move to follow up the input command. Until the cylinder followed up, you only had the limited motion.of the control valve travel available.

With a stick flailing around like that, you would have to mentally integrate your motion relative to the center detent to properly evaluate what the net effect of your control motions was. Are we sure that FBW is the better control system??:hmm:

The aircraft "knows" nothing. It relies on appropriate air data and "intelligent" pilot inputs to perform within its design boundaries.

AF447 did all it was designed to do, and when the "intelligent being" making the command inputs wanted NU, the aircraft complied.

What bothers me is the "intelligent" part of this equation was missing.

I doubt if any of the pilots on this thread would want the aircraft designers to put the "intelligent" part into the automation so that the aircraft "knows" best.

Auto trim is always available except when indicated to the contrary as detailed above.

As I have posited previously, the PF effectively spent 4 minutes battling with a compromised yaw damper that contributed to the roll and at no time was the SS left in the longitudinal neutral position. Without regurgitating the stuff long since posted (many times), if you simply don't know, the result will be equally simple.

Quite so. Concept is giving as much protection as realistically possible. With all air data gone but with reliable inertial reference, everything goes out the window except the load protection.

BEA is Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile. It is the French authority responsible for safety investigations into accidents or incidents in civil aviation. It doesn't pretend. It states so, accepting the full responsibility for its words. Where is the problem with that? You have good arguments it was otherwise? Let's see them!

It is. It wasn't applied here. No evidence so far supports the hypothesis that A330 flight controls systems prevented the application.

Nope. Even with fixed stab, elevator is trimmed for zero force, usually via tabs. I can't recall ever seeing aeroplane without pitch trim.

Trim was applied IAW control demand. Demand came mainly from right hand sidestick. "Stirring mayonnaise" and "it went forward a few times" are incomplete, therefore inaccurate and possibly misleading description of SS movement. SS traces are available in interim 3.

It isn't explicitly written, however FCOM reference is consistent with BEA explanation - since all air data were rejected neither speed<60 kt nor AoA>30° triggering condition could be met.

None. It just retains G protection.


I am sorry you feel it this way but it really is not about contest between you and me. If it were so, I'd rather go down the PM path, in the unlikely event of finding debate worth pursuing further. As this is Profesional Pilots Rumour Network, open anonymous forum, I believe that details behind your temporary loss of control would be interesting to many a reader here. So what if your company allows regular operation below green dot while my does not? Is my wrong assumption that no Airbus operator would, reason enough to withdraw and retain all the information for yourself?

Nose refusing to go down when commanded so is definitively not normal behaviour of FBW Airbus, especially as with low speed you were far from high speed protection and I really doubt you hit G protection at -1. There must have been something else.

As for hours, they were not intended to illustrate my experience but that aeroplanes that are very likely to enter really unrecoverable stall are flying around in hundreds every day and no one makes a fuss about it. Every aeroplane equipped with stick-pusher is such. Now you mention DC-9, it's good example of T-tail without pusher (Super80's hydraulic elevator ram is not true pusher as it is not activated automatically) implying that T-tailed configuration is not automatically predestined to suffer from deep stall. BTW, there is no direct link between yoke and flight controls on DC9.

Clandestino the DC9 series has cables directly connected to the control surfaces. IIRC, specifically the control tabs. The tab directly drives the ailerons and elevators. Transport category jets don't get any more direct controlled than the DirectCable9. Any other other point is purely semantics.

Probably turbulence: Transition from updraft to downdraft could very well create sufficient reduction of "gee" to satisfy the "gee" demanded by a moderate nose-down SS input, without immediately dropping the nose.

It should be the logical way, but Airbus thought otherwise as demonstrated in Perpignan.

I agree - Actually we would need less of that "intelligence" especially when some data are conflicting. After a discrepancy between AoA data + discrepancy between IAS we do not want automation to stay on the way - Autotrim is NOT welcome.

If I had to keep only one single item, I would say that autotrim has been the killer.

- the more we think we discover the worse it gets!

Pilot: I want the nose to go down

***: No! (Dave) I can achieve your demand for a change in vertical acceleration in another, far more clever way ( could even be nose up?)

Pilot: But I only wanted the nose to go down.:{

For heaven's sake - are you serious? Where have we gone wrong? (Answers on a postcard, please). When I move a control I expect a proportionate response in the desired direction.

IF789,
USE MAN PITCH TRIM is a message that appears in the PFD.
It appears as well in the ECAM as a reminder but at a later stage on the STATUS page once all ECAM actions have cleared.

For the Abnormal Attitude Laws I must admit I am not convinced by the BEA statement on page 40 :
AoA data were inertial parameters as described on the traces and they met the conditions ...

Also, as Machinbird reminded, what stopped the trim to reach the limit ?

BOAC,

Perhaps you should re-read TTex600's description of the incident in his posts #169 (p. 9) and #205 (p. 11).

:confused: It was you I quoted!

Because they were trying to get the nose down for four minutes but autotrim didn't let them?

Sorry if this is going back a few pages. I'm still trying to catch up, but had to comment on this:

NARVAL wrote:

And there was I, a very humble SLF, and happy to be abused with that name by all you god-like pilots, because I was under the impression that the reason I trusted my life to the people at the pointy-end was because they were like me, shared my fascination with things aeronautical, and had both the interest in and the knowledge of just what it is that keeps them up there amongst the clouds; that they actually understood something about the "little arrows" (underneath the wing) and the big ones (on top), and the significance of getting these the wrong way round.

And now I learn that it comes as a complete surprise to experienced 'pilots' that the flow of air over an aerofoil doesn't always produce LIFT, and that even though the nose is pointing up, you might be going down. Furthermore, I've learnt that the 'pilots' responsible for the safety of the SLF at the back of 447 hadn't actually been trained in what to do if the auntonomics dropped out and left them in control. Which makes me wonder why they were there. You could make more money by using the seats for more passengers.

Somebody please re-assure me that I'm wrong; that what NARVAL wrote, and what was so warmly applauded by quite a few 'pilots' on this forum, does not represent the average level of expertise of commercial pilots, that most of them do actually understand what keeps them in the air, because otherwise I'm sticking to sailing!

It is a matter of some consequence...."Flight Law changed at approximately 2:10:05...." per BEA.

This is a word that invites doubt, and conjecture. It is an inappropriate statement, and not consistent with accepted levels of research. Alone, the phrase is amateurish, and there is no further refinement.

What prompted the statement? How was it derived? What is the Data referenced to prompt this speculation?

The only data I can find re: the LAW degradation is by the pilot, PNF.

"We have lost the speeds, ALTERNATE LAW."

Which ALTERNATE LAW? It remains unreported by the crew, or referenced by BEA per DFDR. The comment was made sixteen seconds later, after loss of A/P and A/THR.

Of some importance would be the record of airspeed loss, rate and value.

I continue to doubt ICE. A sudden loss of all three ADRs means simultaneous blockage. This is preposterous. A more probable problem would be turbulence, by way of windshear, or blanking of probes similar to a WS alert. OR AoA excursion WITH ROLL.

Clandestino: The fact remains, PF input a PITCH motive, and this defines PITCH, as in PITCH/POWER. It is most definitely possible his stick at two seconds after loss a/p was a preface to P/P. No?

idle bystander. You misunderstand. It is only remotely likely that these pilots were unqualified. By law, they were. This accident is not understood, and do NOT form conclusions as to safety from what you read here. There are perhaps a half dozen events that happened in the correct sequence that downed this a/c. Not that they happened at all, but that the sequence itself occurred. Incredibly remote. You may not believe, but knowing what I know now about 447, I would board with comfort this same flight, pursuant only to the fact that this crew also knew what happened.

The Devil has surprised us all. He saves up for generations to ennable such a catastrophe.

Lyman
Though I am not inclined to blindly trust the reports that come from a French organization (because of France's huge investment in AI), I'm waiting for the final report before I'd judge that items are missing.

And, I don't understand your term, "inappropriate statement." Isn't that event documented be ACARS?

In which we find that OF is not finished yet
 

Lyman
Then the legal definition of 'qualified' was sorely lacking and needs revision, as has already been officially acknowledged. Agree that there are many questions and factors, though.

The Russian pilot who let his son 'steer' that A300 was 'qualified' too, and yet everybody died.

The DFDR includes two discrete parameters: Control normal law in pitch engaged/not engaged, and Altenate law engaged/not engaged (see page 107 of Interim #3). There is also an ACARS message to that effect.

Airspeeds 1 and 3 are recorded and shown in Interim #3.

The FCPC's use the mean of AoA1 and AoA2 to eliminate effects of roll and sideslip.

Mr Idle B - your plea appears to have gone un-noticed. Yes, there are many of us who understand the arrows and hooks and keeping 'rubber side down'. The problem we are facing here is that a particular system of flight (NB no names) appears to engender in some the chance to forget all this and become reliant on the system to look after them. I think you can be assured that many of these have gone away scratching their heads and may now be a little less relaxed about this and hopefully the manufacturers and training systems will also adjust. You will for example, note that the 'drill' taught for stall recovery has been changed following the accident and that I'm sure one large airline will be reviewing the abilities and training of its pilots. Looking at your location I would suggest you have a good chance of being behind someone 'wot knows'.

No.
Because once trimmed the airplane was looking quite comfortable in a stalled status.
But before it started to autotrim :

• 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
• The nose wanted to come down naturally if I released pressure for even a split-second.

dixit DozyWannabe.

As one who has spent my entire career working on, designing and programming simulators (admittedly my "bit" is the sound and comms bit, just so you get the full picture), any assumption regarding a specific edge-case operation should not be trusted on the sim until verified and checked against aircraft operation OR double-checked against aircraft data (assuming doing it on the plane is either dangerous or really difficult). I routinely find issues on certified and in-service-for-years simulators that were not caught or identified during routine operation and certification testing.

While the manufacturer of any simulator will aim for 100% accuracy, the available data is routinely found lacking, hence my cautionary note above. What may seem surprising to some is the fact that the data package supplied by the airframe manufacturer will vary from one customer to another - I recently worked two 737 platforms for different customers, and received different data from each, for the same system. Not entirely different, but 5% was. Eventually I was able to get the same consistent data, but I was lucky since I had access to two sources.

Aside from those parts of the sim using rehosted aircraft code (which has it's own issues), the device trusted for training is the result of hundreds of thousand of lines of code from a motley collection of software engineers, that typically do not follow anywhere near the same rigid procedures and practices employed when writing aircraft-bound code (costs alone would not permit). This is not to say they are not doing a great job, but trusting the sim blindly, in particular in areas extrapolated beyond the aircraft data or figured out by analysis of airframer supplied data, warrant second and third opinions before assuming the behavior is correct.

- GY :eek:

This is certainly true, but BEA has tested every steering input on AF447 against the real aircraft parameter and has come to the conclusion that they are completly consistent. There was nothing wrong with the way the aircraft behaved like this, it was the steering input that was wrong, i.e. they pulled too long and pushed too short. Simple as that. If they had pushed as long and as hard as they had pulled, the THS trim would have gone certainly back to a normal position.

You are hitting the wrong sack if you want to blame the autotrim. Autotrim is a perfect tool. They shouldn't have pulled into the stall.

Where does this leave us?

BEA only tells us, that the flight control inputs in the simulator produced comparable outputs to the flight controls and caused comparable flight behaviour. Nothing more, and nothing less.

To read into those words that the aircraft is sanctioned and freed from having contributed in some way to the outcome looks a bit bold. A systemic inbuilt problem like unwanted behaviour of the THS autotrim (i´m not saying that it is one or isn´t one) would show in the aircraft as well as in the simulation. Only malfunctioning systems in comparison to non malfunctioning systems in the simulation would show as difference.

Where does it leave us then?
It only proves, that concerning the flight control system the aircraft had no malfunctions and that another A330 with the same crew (or with a different crew performing the same inputs) at the same place in the same environment would have ended in the drink too. This recognition might cause more headache for a manufacturer than finding the cause in one faulted part.

franzl

Maybe. But please don't disregard the THS arriving at the stops was preceded by almost a minute of ignoring a stall warning as well as what most would have considered basic airmanship...

Dani and GY were discussing the fidelity of simulators. Nothing more, and nothing less. ;)

Quote:

---

 up to the exit from the flight envelope, the airplane’s longitudinal movements were consistent with the position of the flight control surfaces,

---

(my bold above)

So that although the movements of the control surfaces were consistent with pilot inputs throughout the entire event, there is no direct statement of finding to the effect that after the aircraft exited the flight envelope the aircraft longitudinal movements were still consistent with these pilot inputs even though control surface positions were. Nor does this appear to imply anything further.

I would imagine this is still being investigated.

this sentence does not mean that they don't know the correctness of flight control surfaces movements, but: You simply cannot predict the flight path in a stall anymore, the aircraft is not behaving "aerodynamically correct" or "like designed". It rather moves in a random pattern, depending on chaotic aerodynamic laws, not predictable and not rationally explainable (unless many more factors would be taken into play, in a much bigger "resolution" of values and mathematical formulae).

On the contrary, it did trim up, but it hit a limit of 3 degrees nose up. So we re-ran the test by winding in full nose-up trim manually and even with full nose-up trim the sim pitched down successfully on elevator deflection alone before the trim started rolling forward (although the autotrim did respond very quickly - I made a point of adding it into my scan once we started recovery).

There's a little-known coda to that accident, and that is the story of how the pilots successfully recovered the aircraft from the initial stall, but overcorrected by pulling up too long and caused a second stall that sealed their fate. What the investigators discovered in the sim was that if the pilots had simply let go of the control columns, the A310's protections would have stabilised and righted the aircraft on their own. Sadly, the Russian pilots were not trained on this feature of the A310's design.

I suspect that this is simply an acknowledgement of the fact that they can't replicate the behaviour of the actual aircraft in the stall without stalling the aircraft and measuring it (any test pilots want to volunteer?). By it's very definition, stall is a regime that is out of controlled flight and there are myriad forces acting on the airframe that are not easily modelled.

Dani, I would normally fully agree with your assessments, but the autotrim you know and love in Normal law is not the same autotrim in certain critical respects when in ALT2 law.

Ninety-nine point nine nine nine percent of your flight time or more has been in Normal Law. Just because your regular autotrim has been so sweet doesn't mean she does not have an ugly sister.:ooh:

Zorin75

The THS did not travel to (-) stop. It stopped short, something less than a degree. Neither did it "start" after one minute of SW.

Take a look back at Takata's pic of the Recovered THS. Note the damage to the NU end of the screw. Impact? Possibly. But the damage suggests collapse of the thread collar opposite the implied direction of travel at water impact. Something like an airload, not a water contact.

BEA tells us on p.41 of IR#3:
This could be a computer simulation rather than one in a fixed-base or moving-base flight simulator.
That statement presupposes knowledge of the aerodynamic characteristics outside of the envelope where these characteristics have been established by flight test, perhaps extrapolated using wind tunnel data. If these characteristics were known, it would not be particularly difficult to model them (at least for the longitudinal motion), and to use them in a simulation to produce your statement.

Maybe, I still don't see where autotrim was to blame in AF447's case. It did autotrim what the PF ordered. Autotrim has no artificial intelligence to know what's in a pilot's mind. It stupidly does what it has been told: When you pull for a long time it trims this position to zero force. That's the definition of trim. What's wrong about this function on AF447? If only he would have pushed the stick as long as he pulled it, autotrim would have ordered THS back, this I'm pretty sure.

What is the purpose of "zero force"? Pilot feels nothing anyway, and the elevators can sustain and withstand the forces on their own. What the THS adds is lethargy when perhaps an abrupt input is necessary.

It's great for cruise. What is the need in ALTERNATE LAW?

Does the computer get sore muscles?

Zorin_75:
Correct - my point really was that jumping in the next available A320 or A330 simulator and wringing the cr*p out of it into an upset condition (outside of flight data) puts you entirely at the mercy and competency of the individual simulator engineer responsible for that aspect of the simulator performance - so in the case of flight modeling you might happen upon a model built with sensible extrapolations and cleanly interpolated behavior, while other models may simply 'straight-line' the performance once the flight test data runs out. It is unlikely such a flight regime was tested beyond a joy ride or unintended upset from the less capable engineers testing the sim - the last thing on a persons mind at that point is the accuracy of the simulation. The same would be true of any other aspect of the modeling, be it hydraulic systems, electrical or whatever.

So, taking the trim behavior in a simulator, once into an upset condition, with possible invalid airspeed, etc, probably shouldn't be regarded as definitive. I'm one of those engineers and I wouldn't trust it. As noted before, the sound models I produce would NOT include a vertical speed component as a contribution to the aerodynamic noise 'hiss' model. I have not data to model it and would be guessing. I could probably make a pretty good guess and have something representative, but:
(a) I've never been asked for it
and
(b) I'll bet if I ask 3 pilots for a subjective assessment, I'll get at least 4 opinions....

I suspect the Airbus "simulator" referred to in the interim report was an engineering simulator based on flight modeling the aircraft behavior versus control inputs, not what we all know as a full flight sim - perhaps the final report will define this more specifically.

- GY

no, it trims not for zero force, it trims to maintain or achieve an ordered load factor.

As we know, autotrim not works on behalf of the SS inputs, but on the order of the FCPC, which has an ordered load factor of 1 g (no SS input) or a change (decrease or increase ) of this loadfactor (SS input).

Example (and this is not far away from AF447):
When in ALT2 and the aircraft is in a climbing trajectory (make it shallow or steep, the difference is only time) and the speed decreases (no autothrottle), the FCPC´s will position first the elevators and then the THS in order to maintain 1 g in the climb to compensate for the decreasing speed, even when SS is in neutral / untouched position.

Without preotections in ALT2 THS trim might even drive NU with a SS-ND input, if the increase in descent rate (like in the stall of AF447) decreases the loadfactor more than a small SS ND command would demand and elevators are already full NU.

Therefore machinebird got it right:
franzl

In terms of 'stops', isn't it usual to have software stops somewhat in advance of any mechanical stops. Is there really a discrepancy ?

Are you implying a suspicion that Auto Trim was misbehaving in ALT2, i.e. the systems functioned in a degraded manner as per the XL Airways / Air NZ A320 accident?
I feel that NOT calling and clearing the ECAM messages and following the UAS QRH procedures introduced so much fog into the situation, that a failure to notice the Trim Wheel turning sits equally in this patch of fog.

In short, the Human Factors were dominate in this accident.

I don't agree. The whole AI's fbw system is made to maintain or achieve an ordered load factor. Not the trim sub system.

Remember: You give a sidestick input, that's the load factor you order. Now fbw computers calculate the necessary load factor. When you release your side stick (normal law), you maintain the ordered load factor.

What trim does is that it "neutralizes" long term load factor orders, so the flight control surfaces can go to neutral position.

Originally Posted by Organfreak
The Russian pilot who let his son 'steer' that A300 was 'qualified' too, and yet everybody died.
Dozy:
Oh, it was an A310? My mistake.
But I wouldn't call that detail "little-known." Hell, I saw it on Air Emergency on the idiot box just the other night! But, in their defense, they never knew what was wrong in the first place. I doubt they would have trusted (my speculation) the protections at that point. Did the A310 really have that feature?