AF 447 Thread No. 9

[DozyWannabe]

Uh, you're making a distinction without a difference. The Airbus can NOT be flown without the computers.

Neither can the B777, and it would be a very difficult task to do the same in the B767 and B757. I apologise if I misunderstood your intent, but from my perspective it read that the FBW Airbus models were intended to be flown under automation at the expense of the flight crew.

Why? I'm not arguing that point. The pitot's iced up, therefore Garbage In, and the computed airspeeds turn to Garbage Out. Subsequently the computers give the airplane (which they can no longer fly) to the human. Leaving the human to deal with it.

Actually in the Birgenair case, the B757 FMS continued to try to fly it, pulling the pitch attitude up to the FMS limit - in that case on the very edge of stall.

The pilots were left without the vaunted computer protections...

Which they should have been trained to deal with...

while you and others lay in your warm beds dreaming about how the system really does allow pilot full control.

You tell me how the system did not allow the AF447 crew full control. The aircraft stalled because the system was programmed to give the PIC everything he or she asked for in the event of a systems failure.

You just won't give up will you? IIRC, you claim no connection to Airbus, AirFrance, etc, but you have made claims in this very quoted post to know the intent of the design. How do you know?

Because the late professor who instructed me on software engineering and reliability (who, it must be said, was a dyed-in-the-wool sceptic) banged the Airbus FBW case into our heads as the first thing he did and - despite the fact he visited Toulouse and told us everything he saw - was holding their feet to the fire until his dying day.

All true I assume. Except that your little toy computers don't seem to be able to replace humans and humans would appear to prefer a speed stable airplane.

Not all humans - unless you have evidence to the contrary.

And if you honestly think I'm pro- pilotless airliners or that I'm some kind of advocate for full automation then you clearly have not read my posts. What bothers me is the repetition and propagation of press scuttlebutt as fact. Computers are great at the dull and repetitive tasks that keep an airliner on course, but they're singularly lousy at being able to deal with situations outside of the norm.

[PS: Spinmeister? If anything I'm anti-spin! Here's the deal - the idea that the A320 was the first step towards fully-automated airliners? Spin. The idea that the Airbus FBW protections would routinely override human pilot input? Spin. The claim that a certain A320 on display "thought it was landing"? Spin. ]

[infrequentflyer789]

1) To work properly, automation and protections need reliable data.
If data are known to be corrupted the simplest thing to do would be to cancel automation : Direct law - No autotrim
Every Boeing pilot flies that way in manual flight, is it an issue ?


Yes it is an issue.

At Schipol the 737 autotrimmed into stall and trim was never touched in recovery (nor was thrust properly applied, but had it been the result might have been worse due to trim - see e.g. http://www.pprune.org/rumours-news/363645-turkish-airliner-crashes-schiphol-103.html#post4787036 ).

Ethiopian (boeing again...) at Beirut was mistrimmed, manually, into stall and crash.

At Perpipnan they did drop into direct law... and it didn't help. They were trimmed up into stall and never changed it. Had they stayed in alternate with auto trim would they have managed the recovery ? Would autotrim have helped or hindered them ?


2) ALT LAW + Autotrim amplify the severity of the stall.


Surely only if the stick is held back, which will be fatal anyway in stall ?

On the other hand if stick is pushed forward, autotrim (if trim was NU into the stall) will help to reduce AOA and reduce chance of secondary stall when compared with not touching the trim, no ?


PS : Thanks to both of you for you reply.
It is unacceptable the BEA simply ignores the matter.

There is a difference between ignoring a line of investigation and investigating, eliminating and not pursuing further. The auto trim behaviour clearly has been investigated, based on what is in the report.

Resources are finite, and I don't think the investigation necessarily has the remit to go further into things that may be interesting but not causative or relevant to the outcome of the accident. There are areas I'd have liked more depth on - but I think they've eliminated them too.

My impression looking at the HF slant in the report is that BEA have clearly focused on (1) rather than (2) from:

(1) why are crews (not just this one) stalling and pulling back in stall
(2) why is the trim following the pilot command when (1) happens


So, are they correct to prioritise (1) over (2) - which does not mean they ignore (2) - which problem needs fixing to prevent crashes ? Which problem will become a non-problem if the other is fixed ?

[Clandestino]

QF72 A330
Just short memory ... or desire to look the other way ?
BTW, still no fix, just the same OEB to try to beat the dysfunction ...

I am afraid that Australian ATSB has shown utter disregard for your ideas that fix is inadequate and in its final report of upset to A330 near Learmonth (http://www.atsb.gov.au/media/3532398/ao2008070.pdf) has found actions by Airbus quite acceptable.

So for you .. the judges have vested interests and so they will misusing the recorded data ?
That's new for me .. I suppose you have references ..Do you really think wording of Annex 13, 5.12 was pulled out of thin air?

The State conducting the investigation of an accident or incident shall not make the following records available for purposes other than accident or incident investigation, unless the appropriate authority for the administration of justice in that State determines that their disclosure outweighs the adverse domestic and international impact such action may have on that or any future investigations.

If it is just my opinion that judicial actions can have adverse effect on aviation safety efforts, how come ICAO listens to me? Perchance it's not just my opinion, eh?

Are you in disagreement here with BEA?Yes. Who said the BEA's word is sacrosanct? That other crews did react to stall warning, if not in completely perfect manner, at least in the one that kept them flying makes it hard to argue that

the conditions in which airline pilots are trained and exposed to stalls during their professional training and the process of recurrent training does not generate the expected behaviour in any acceptable reliable way.
...if we accept it to be general appraisal and not directed at one specific crew.

Well, BEA is adressing this matter again, and you disagree here again? No, I'm not saying they got it wrong, just that it's largely irrelevant. Of what use is any protection if the crew is able to control the aeroplane properly? Alpha prot is used consciously only when terrain is a factor. AFAIK, accident started to unravel at FL350 over the ocean.

Maybe there is merit in developing a system that reliably detects a stall and announces that condition unequivocally to the crew.Is this serious proposal? WTH is wrong with what we have, except it doesn't work at really extreme angles.

At best we only have a small snapshot of what occurred in the flightdeck, and can only speculate on the crew’s mental activity. Small snapshot? We have DFDR readouts and CVR transcript that clearly show crews have no clue what is going on and if anything is marginally consistent with CM2 inputs it is normal law GPWS escape. however, it was performed over the ocean, at FL350, when protections were lost. Have a look at page 96 of French report (English is botched here) to see what would have happened if both pilots went catatonic - it's the magenta line.

Here is BEA definition of the depart. Do you see any reference to STALL?Another dazzling display of failing to understand the basic aerodynamics. Departing the envelope through lift limit is called stall. Report is full of reference to stall.

Neither was there Stall Buffet sufficient to announce STALL onset. It was far more then sufficient. Test pilots say so. Page 93 refers.

There was no drastic increases in drag, in fact drag was decreasing, due to the lessening of velocity.What then did cause the aeroplane to decelerate with maximum thrust, if there was no drag? Things we discuss seriously on professional pilot's forum are sometimes unbelievable.

There is a profound difference between "loss of..."
And "Unreliable...."Who cares about the difference. Instrument rated pilots must be able to keep on flying any aeroplane (even Airbus) whether speeds are unreliable or totally lost. That's basic instrument flying.

So yes, the issue was they were lost at STALL,Main issue is that they induced stall - something no other crew succeeded.

What did the crew do that was unique? Stalled without realizing it.

If it would have been a simple stall recovery maneouvre, why did BEA use those cryptic words? Because there is nothing simple about taking the aeroplane into area which was a) never entered during flight testing b) was not required to be entered by certification requirements c) was never entered by the type during its 11 years in service, let alone getting her out of it. While there are no reliable data about exact aeroplane behaviour during recovery, it is certain very large nose down attitude would have needed to be achieved to get the aeroplane flying again.

But first things first, the BEA had to evaluate what was the influence of the autotrim in the process.Well, this time they listened to you:
Throughout the flight, the movements of the flight control surfaces were
consistent with the pilot’s inputs.

References appearing to the Airbus 'stall recovery pull-up' manouevre. Is this right?No. Maintain attitude and add power used to be low level approach to stall recovery. Maybe it still is.

According to Clandestino, Alternate Law handling is trained to assume a worst-case scenario (i.e. all protections lost).

Per company training but I can't really imagine any sensible training department teaching pilots how to use reduced protections as they are overridable. There is just one protection that is supposed to be used deliberately... I've already said that

think he was honestly trying to regain a cruise Pitch or thereabouts.17.9° is not cruise pitch. Full back stick is not hamfistedness.

At what point then do you consider the a/c STALLED?Past Clmax.

As designed, the autotrim helped to put deeper the aircraft into the stall ...What a wonderful partial view! It was always active in all other cases and helped maintain control. It would have helped the recovery if nose down was maintained.

I find the Boeings airspeed indications more damped than the ABIf it were true, the word would be "lagging", not "damped".

I would say only moderate but the speed indications would have had you believe the aircraft was out of control.I find idea that pilot would rely only on speed indication to check whether the aeoplane is out of control pretty frightening (though it might help explain somewhat Birgenair or AF447).

Why Airbus SAS design delegates to the crew UAS diagnosis?Same reason Boeing does... computer can't recognize it.

On UAS early warning: Technically speaking this is VERY EASY.You keep on saying that without offering practical solution.

Everybody in this Godforsaken business eventually hides behind the law that places final responsibility in the pilots hands.Tough. Well it's his posterior in the aeroplane so there's good reason to be responsible.

Sidestick neutral, the THS would have rolled the same way.It would have rolled the same way trying to change flightpath with 2.5G demand and maintaining 1G?!? Well if it were let go after the climb was established it would roll in the same direction but not with the same speed.

It flies just as well under Alternate Law - and unlike the Cessna, A310 or Boeing, manual trim is more difficult because - as has been said - there is no direct or artificial feedback.1. You probably meant direct law, ALT has autotrim
2. It is BS perpetuated by some. It is very easy to trim Airbus in direct law using wheel. Fact that you move stick and not just release the pressure as you trim did cause some concern to me when I read the manual. It is absolutely easy to do, folks who keep spouting it's a problem have never tried it.

The Airbus can NOT be flown without the computers.It flies very nicely without any computer intervetion, with direct stick-to-control-displacement of direct law.

Subsequently the computers give the airplane (which they can no longer fly) to the human. Leaving the human to deal with it. Per design. Big deal.

The pilots were left without the vaunted computer protections while you and others lay in your warm beds dreaming about how the system really does allow pilot full control.So were the others. What is the use of protection, anyway? Just watch CONF iture rising to bait.

Neither can the B777, She can. Why are we bringing opinions that are blatantly wrong into discussion? We are not flying passengers in bloomingly unstable Su-27!

[RR_NDB]

You keep on saying that without offering practical solution. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-51.html#post7341467)

My role here is limited. I consider first to assertively say what i am convinced, absolutely sure and this must be said. Because was important in the crash.

I am available to explain by voice the "practical solution" to an interested pprune member. Simple, just call me and i can teach what to do.

Actually most EE knows that. Simple DSP techniques used extensively in the industry.

In simple words: We need to perform a DSP of the air (analog output obviously) speed information and:

1) Inform IMMEDIATELY to the crew the UAS onset.
2) Block IMMDIATELY GI to ELIMINATE GO (GIGO played a pivotal role)

In a previous post i mentioned an Airbus SAS paper that shows the opposite: The crew must diagnose. IMO this is a serious error. In many aspects.

So important specially when you do not have redundancy at all. (Important sensors failing SIMULTANEOUSLY).

:{


Degrade a System and wait for the crew diagnose is a COMPLETE ABSURD. The chances could be dim even for a designer acting as pilot depending on behavior of the System.

The approach used is WRONG. And SHOULD be changed:

1) UAS DSP detector
2) Actions by crew/System or System/crew

[RR_NDB]

Same reason Boeing does... computer can't recognize it. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-51.html#post7341467)

We are discussing here a total failure of an Airbus SAS product.

FYI, a very cheap processor can do it EASILY.

A DSP of "audio" frequencies or less. :{

[DozyWannabe]

1. You probably meant direct law, ALT has autotrim

No - I meant Alternate Law, but the sentence that followed it referred to Direct.

2. It is BS perpetuated by some. It is very easy to trim Airbus in direct law using wheel. Fact that you move stick and not just release the pressure as you trim did cause some concern to me when I read the manual. It is absolutely easy to do, folks who keep spouting it's a problem have never tried it.

Fair enough - I was working on the assumption that it would be harer without tactile feedback, but if you think otherwise...


She can. Why are we bringing opinions that are blatantly wrong into discussion? We are not flying passengers in bloomingly unstable Su-27!

I think there's a bit of a misunderstanding going on here. The point I was making is that all modern airliners rely on computers whether being flown manually or on auto these days. If the electronics quit, it's a lot more difficult to fly them.

RR_NDB - a modern DSP will not pass certification on the basis of MTTF. As a backup it's plausible, but as aprimary replacement for pitot tubes it won't work.

[TTex600]

It flies very nicely without any computer intervetion, with direct stick-to-control-displacement of direct law.


Really? And you know this how? Are you, were you, an Airbus test pilot? Just how is a line pilot to accomplish this state of control?

[DozyWannabe]

@TTex600:

Clandestino is a former FBW Airbus line pilot, now flying ATR turboprops. Some clarification should be made in that what he is describing is Direct Law, where the computers pass the sidestick inputs direct to the flight surfaces.

The FBW Airbus models will not fly if the electrics are lost altogether - but this is also true of any other modern airliner you care to name.

[jcjeant]

Quote:
Originally Posted by BEA Final Report (English) p.22-23
At 2 h 10 min 51, the stall warning triggered again, in a continuous manner. The thrust levers were positioned in the TO/GA detent and the PF made nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) began a nose-up movement and moved from 3 to 13 degrees pitch-up in about 1 minute and remained in the latter position until the end of the flight.

That's a factual account of the THS behaviour - and the limit of what the BEA can say. Indeed this is a factual account and the limit of what BEA want to say
Conf asked about a analyze ....
I find (like him certainly) that what you quoted from the report is not a analyze ..
But maybe (or likely certainly) the BEA think that a analyze about is not relevant ...

[TTex600]

Clandestino is a former FBW Airbus line pilot, now flying ATR turboprops. Some clarification should be made in that what he is describing is Direct Law, where the computers pass the sidestick inputs direct to the flight surfaces.

The FBW Airbus models will not fly if the electrics are lost altogether - but this is also true of any other modern airliner you care to name.

So you agree with me. Without a computer, you can't fly an airbus. Again, try and stay on topic. My post didn't say that you can't fly an airbus without electricity, it said that you can't fly an airbus without computers.

I've just checked my A320 FCOM (27.40.5) and it indicates that an ELAC (that's a flight control computer just in case the peanut gallery isn't aware) provides "direct pitch and roll" along with other functions such as normal pitch and roll. If my books are wrong, please give me a link to a better, more in depth, manual. Then tell my Director of Training about it as well, as he seems to think his manuals are airbus compliant.

Edited to add: I'm still waiting for the instructions on how to put an Airbus in direct law. I'd like to try and fly it that way if I ever get assigned to a mx flight.

[DozyWannabe]

So you agree with me. Without a computer, you can't fly an airbus.

And you'll have difficulty doing so in just about any other modern airliner, because the only jetliner being made with wholly mechanical manual reversion is the B737.

Again, try and stay on topic. My post didn't say that you can't fly an airbus without electricity, it said that you can't fly an airbus without computers.

See above.

Edited to add: I'm still waiting for the instructions on how to put an Airbus in direct law. I'd like to try and fly it that way if I ever get assigned to a mx flight.

You're in Direct Law whenever you land.

If you want to force Direct Law in flight, then the only way to do so is to sabotage the systems. I don't understand why you'd want to.

[jcjeant]

What then did cause the aeroplane to decelerate with maximum thrust, if there was no drag? Things we discuss seriously on professional pilot's forum are sometimes unbelievable.Add Newton to the equation (the apple) and your explanation of the deceleration will be complete (it's not only for artillery matter)

[bubbers44]

I have never flown an aircraft, mostly Boeings, that wouldn't fly just fine with all generator power gone and 30 minutes on the standby instruments then indefinately to destination once clear of weather. Losing an aircraft at FL350 because the pitot system froze up would not be an emergency. If you follow the crazy procedure of going into a 5 degree pitch up and climb power then you will soon get an overspeed. Everybody knows that. Maybe the PF forgot he went to alt rules and reacted as he did pitching up into an impossible 14 degree deck angle because he thought Airbus said you can't stall it so just pulled back and held it for over 3 minutes.

My personal experience is once you become a monitor of automation you gradually lose your hands on flying skills. I experienced it once going from the MD80 back to captain on the 737 200 which is a baby step compared to the AB. I never let it happen again once in the 757. I kept up my hand flying skills to be safe.

[Clandestino]

My role here is limited. I consider first to assertively say what i am convinced, absolutely sure and this must be said. Because was important in the crash.Important is what happened, not what someone is convinced happened. That there exists a real world that we are dealing with in aviation is beyond doubt so flying is definitively no place for solipsists (http://en.wikipedia.org/wiki/Solipsism).

Simple DSP techniques used extensively in the industry.In washing machines and refrigerators also. It's not the digital signal processing technology, it is the algorithm what matters! No one has so far come with reliable algorithm to automatically detect and deal with UAS nor you have made any practical suggestion. Just wishes.

We are discussing here a total failure of an Airbus SAS product.Cheerfully ignoring that any aeroplane equipped with fault warning system in service today, when involved in UAS, will bombard the crews with undue warning messages.

Degrade a System and wait for the crew diagnose is a COMPLETE ABSURD.So you have noticed way things work and developed own theories about it after the system was certified and successfully flown for 20 years? What prompted you to notice?
No - I meant Alternate Law, but the sentence that followed it referred to Direct.OK - it still holds it's not difficult for someone aware what he is supposed to do.

I was working on the assumption that it would be harer without tactile feedback, but if you think otherwise...I am also not immune to buying BS occasionally. Good thing I had a chance to try it myself so rectified my opinion through personal experience.

The point I was making is that all modern airliners rely on computers whether being flown manually or on auto these days. If the electronics quit, it's a lot more difficult to fly them.Exactly - they are not relying on computers to keep them airborne, they need it to deal with precisions of RVSM, RNAV and CAT3 but they can be safely flown without them. So what if every computer go tits-up, aeroplane is still flying and it's pilots job too keep it so until safe landing.

Really? And you know this how? Are you, were you, an Airbus test pilot? Just how is a line pilot to accomplish this state of control? Direct law is extensively practiced on initial type rating training and later it often is a part of sim refreshers and checks.

Clandestino is a former FBW Airbus line pilot, now flying ATR turboprops.1. Actually it was ATR - A320 - Q400 but even if I were 12 year old Justin Bieber fan, it would have absolutely no impact on the assertions I've made here. Ad hominem is logical fallacy no matter if we use it to discredit or support the claim.

2. As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. So if someone makes a claim he is a pilot of this or that and then goes on making absolutely false claims about the equipment he is supposes to fly on, it absolutely doesn't imply that the pilots of said equipment are not acquainted with their mount and that we should blame the manufacturers for providing inadequate manuals.

I'm still waiting for the instructions on how to put an Airbus in direct law. I'd like to try and fly it that way if I ever get assigned to a mx flight. 1. direct law is not to be activated deliberately. Failures that will cause degradation to it are comprehensively listed in FCOM
2. mx flight programme covers way to achieve direct law, if checking the handling in it is required.

You're in Direct Law whenever you land.Actually, it is only in rollout.

If you follow the crazy procedure of going into a 5 degree pitch up and climb power then you will soon get an overspeed. Everybody knows that.Let me try it this way: everybody knows that, except the test pilots developing the procedure, authorities approving it, instructors teaching it and pilots knowing their procedures. I think you should really talk to them about their fallacy. Bring some arguments along.

Add Newton to the equation (the apple) and your explanation of the deceleration will be complete (it's not only for artillery matter) Great. Now we're not just creating our own personal aerodynamics but even our personal physics. What do you believe was the reason aeroplane did not accelerate when it started falling? While gravity did help curtailing the zoom climb, original argument was directed at the notion there's not much drag when aeroplane is stalled.

Maybe the PF forgot he went to alt rules and reacted as he did pitching up into an impossible 14 degree deck angle because he thought Airbus said you can't stall it so just pulled back and held it for over 3 minutes.So that's it. He was aware what happened andof the procedure to be applied but unaware that he was flying above acceleration altitude despite taking off four hours earlier. Plausible? I don't think so.

[rudderrudderrat]

Hi Clandestino,
Originally Posted by Dozy Wannabe
You're in Direct Law whenever you land.
Originally Posted by Clandestino
Actually, it is only in rollout.
If you are going to be picky, during roll out, you are actually in a sub mode of Direct Law called Ground Mode.
http://blackholes.org.uk/PP/Flight%20Ground%20transition.jpg

It's NOT the same as the in flight Direct Law: FCOM 1.27.30 P6.
"With the aircraft in the clean configuration, the maximum roll rate is about 30° per second.
With slats extended, it is about 25° per second."

Ground mode aileron deflection, when above 80 knots, the effectiveness of roll control, ailerons and roll spoilers, is reduced by the half (e.g. aileron deflection limited to 50% of maximum deflection).
See, Report: Lufthansa A320 at Hamburg on Mar 1st 2008, wing touches runway in cross wind landing (http://avherald.com/h?article=42826d3a)

Easy for the unwary to get caught out.
Simples?

[RR_NDB]

Hi,

Clandestino

In a K.I.S.S. approach:

1) An extra resource capable to inform UAS onset would be useful?

2) Block garbage to enter System would be better?


The crew processed adequately the surprises they received?

I would prefer to be informed immediately by an UAS detector resource than to be bombarded by the results (of the UAS) in the System.

False positives would be a problem? IMO, not.

My rationale is:

I don´t like the approach to diagnose UAS by System output. As showed in an Airbus SAS paper mentioned in an earlier post. This can be improved and in AF447 case seems very important.

Thanks to mention Solipsism. Rich issue. Maybe could be applied to Laser based AS sensors. Definitively not here in processing analog information coming from current technology. This is real long time ago.

I started my career using vacuum tubes (big ones in NDB, HF gear, etc.). In the Analog world.

The inputs i prefer (for my decision making) are analog signals. Not garbage processed by Systems.

Sadly, the (non adequately trained) crew of AF447 were:

Surprised by the System output and worse: Had to process garbage generated by the System.

And failed in their decision making. Actually, worse than that, never realizing (in time) what was going on...

:{

[bubbers44]

I don't think the test pilots that approved the 5 degrees nose up and climb power tried it with blocked pitot tubes. The trapped pitot pressure and the decreasing static pressure would cause an indicated airspeed increase and at some point an overspeed warning.

[HazelNuts39]

bubbers,

In the case of AF447 the pitot drains remained open, hence the pressure was not trapped. I guess the procedure designers looked at the scenario you postulate, and decided that 5°/CLB would allow sufficient time to get more accurate settings from the QRH, or to analyze the situation and ignore the warning if necessary.

[Lyman]

HN.... Why would the boffins select a climb, at all, in the first place? If one is in that narrow band of a/s, seems like given the record, higher airspeed might be worth the risk, rather than a climb into the lid, a risk of STALL, or power and lift ceilings being passed, as 447 did? She maxed at 38K, and got their in a flash, so why not 0 degrees and no power increase, or even a reduction in Thrust.

[RR_NDB]

I don't think the test pilots that approved the 5 degrees nose up and climb power tried it with blocked pitot tubes (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-51.html#post7342249)

Even in a test environment misleading is dangerous.

I guess the procedure designers looked at the scenario you postulate, and decided that 5°/CLB would allow sufficient time to get more accurate settings from the QRH, or to analyze the situation and ignore the warning if necessary. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-51.html#post7342302)

For the sake of Graceful degradation, increasing crew chances to act precisely.

Thiels 727 is a good example of what can occur.

Ignore warnings can be lethal. Better to have decent man-machine interface behavior even during transients and anomalies.

This is possible? I think so. R&D must be done to improve current situation.

[RR_NDB]

She maxed at 38K, and got their in a flash, so why not 0 degrees and no power increase, or even a reduction in Thrust. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-51.html#post7342318)

Why not protect the plane to REC MAX apogee. Hard limit (Airbus SAS approach)

[bubbers44]

It is hard to think any pilot at FL350 would think it is a good idea to put any airplane in a 14 degree nose up attitude unless it is a fighter jet. Why?

[Lyman]

Why not descent, we know climbing is a problem, why the scared ninny overspeed?

Easier to descend than climb.

[TTex600]

HN.... Why would the boffins select a climb, at all, in the first place? If one is in that narrow band of a/s, seems like given the record, higher airspeed might be worth the risk, rather than a climb into the lid, a risk of STALL, or power and lift ceilings being passed, as 447 did? She maxed at 38K, and got their in a flash, so why not 0 degrees and no power increase, or even a reduction in Thrust.


Poor training. As I've stated more than once on this topic, my training was no better. What I know on this topic was gleaned almost entirely after AF447. My line's training dept did add the UAS scenario after 447, but it focused more on the lengthy procedure to identify suspect ADR's than flying or recognizing UAS.

A thorough reading of the UAS procedure in my FCOM shows that one should level off for troubleshooting when above circuit alt or MSA. The memory pitch and power settings no longer apply for level flight.

Which brings us back to the obvious. They never recognized UAS. They weren't trying to climb.

The key to preventing another such accident isn't in designing a better set of laws, etc, it's in designing a better way to show the crew what's truly happening.

[syseng68k]

Surprised by the System output and worse: Had to process garbage
generated by the System.

And failed in their decision making. Actually, worse than that,
never realizing (in time) what was going on...
You might be picking on detail, but the underlying sentiment and
concern about various aspects of the design is, imnsho, quite
correct. If the systems fail and give no information, then fine,
but to fail and give incorrect information is extremely dangerous
and almost certainly contributed to this disaster. The present
systems do not degrade gracefully at the edges and in fact they look
decidedly brittle. Now i'm just an engineer with some, but not
much flying experience, but I would expect any safety critical
design to be far more robust at the limit, irrespective of whether
the designers ever expected those limits to be exceeded.

But hey, let's not criticise the coffee, or cast aspersions about
any aspect of the airbus design, lest we are buried in the smoke
screen of irrelevant detail ;-)...

[Lyman]

I got the sense early on that no one had a grip on UAS, that every man jack was taking a stab at some solution....de jour. No airline, no manufacturer, no one...

The chronology was squishy, but no one has come up with any au courant syllabus that would have helped our friends that morning...

That is not cute, but when it came out that the levels of skill in high altitude manual were rock bottom, that is strike two...

After 36 close calls, finally a strike out...Not unexpected. As time went on, the standard defense of ownership of the problem becam ad nominee, repeated ad absurdum.

I have talked to many line pilots in the past three years, and though they don't know what happened, they don't take the PPRuNe attitude either.

TTex, my next door neighbor flew the 320 for ten years for the American counterpart of the legacy. He shared with me a lot of what I hear from you...
He loved the a/c, and he never had a hiccup in ten years, what's not to love?

On another note, he confessed a low level of familiarity with Alternate Law, and he had never heard of alternate Law, 2b....Don't get me wrong, this guy retired off the triple 7, and his skill was at the highest level. He was being honest, and said he would not want to face the issues 447 had, and he had some nice things to say about the AF crew that did not make it. He essentially said no one would ever know exactly what happened, and he couldn't make the call on what appeared to have happened.

Why is it the system calls everything so close? Two more weeks and the probes would have been changed out, six months more and Qantas A380 doesn't lose an engine to explosion, etc. Ba 038 was a Luckymiss, etc.

Things were coming around to a solid solution for UAS, but it seems one or two get sacrificed to the razors edge, and lazy greed.....

"The key to preventing another such accident isn't in designing a better set of laws, etc, it's in designing a better way to show the crew what's truly happening."

.......TTex600

Says it all...

[RR_NDB]

But hey, let's not criticise the coffee, or cast aspersions about
any aspect of the airbus design, lest we are buried in the smoke
screen of irrelevant detail ;-)...
(http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-52.html#post7342509)
My acid comments were directed to:

1) Lack of Redundancy (wrt AS)
2) GIGO (misleading not properly trained crew)

WRT to A330, she is an State of the art machine. That could and should be improved.

[RR_NDB]

"The key to preventing another such accident isn't in designing a better set of laws, etc, it's in designing a better way to show the crew what's truly happening." (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-52.html#post7342510)

And this is feasible! I hope it will be implemented soon. (UAS EW)*

(*) Why?

Simply because Pitot´s may fail SIMULTANEOUSLY

Simply because System contamination (misleading crew is potentially lethal)

Simply because sierra happens, independant of good designers or good pilots. Someone pay the toll.

[syseng68k]

Says it all...
Yes, it does, but corporate arrogance being what it is, it perhaps
takes 200+ innocent bystanders to lose their lives before they are
shocked out of their complacency. Give Airbus their due though, they
seemed to have made all the right moves in terms of recommendations,
but they were not legally binding. The real problem was much further
beneath the surface though, in that the system design is not robust
enough to provide consistent and accurate information at all times,
including operation beyond the limits of checklist logic and "painting
by numbers" error recovery procedures. Human error is to be expected
and must be accounted for in the design.

Of course, it's easy to say that the a/c type has millions of safe
flight hours. Doesn't mean that the design is right, just that the
edge case problems haven't showed up yet...

[RR_NDB]

Of course, it's easy to say that the a/c type has millions of safe
flight hours. Doesn't mean that the design is right, just that the
edge case problems haven't showed up yet...

(http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-52.html#post7342691)


Bold mine

[Turbine D]

Lyman,
Why would the boffins select a climb, at all, in the first place? So why not 0 degrees and no power increase, or even a reduction in Thrust.
On the A-330, there are 4 thrust lever indents:
- Idle
- Max climb
- Max continuous/flex
- TOGA
As they were cruising at Mach 0.82, 35K, A/T on, the engine N1s were 100% and lever position was in Max climb. It's the way the aircraft works.
Now, when they began to experience turbulence, they manually reduced the speed to Mach 0.80 and the engine N1s reduced to 85%.
Then the event started A/P followed by A/T shut off and they received a warning of "Thrust Lock, move the thrust levers" which they eventually did. Just because the thrust levers are in the Max climb indent does not mean the aircraft will climb like a rocket, at least not at 35K or at a 85% N1. So they weren't boffins at that point. Now if you recall, when the A/P came off, the nose went down and the plane started to bank to starboard and the pilot flying manually tried to make a correction to get the nose up and get the wings level. But, his touch was heavy attempting to do both and we know what resulted.
We have been through this pitch and power settings many times. A pitch setting of anywhere between 2.5 - 5.0° nose up would have worked and the N1 at 85% to maintain Mach 0.80 would have provided time to get out the accurate pitch and power settings base on aircraft weight.
But they didn't do that, yet they knew they had "crazy speeds" which should have lead to the UAS process defined above.
I would not think reducing power and going down would be the thing to do as the speed would rapidly increase leading to a speed-speed warning.
There are times when following directions that, or should be, the basis of the word "Aviate" are really important. This was one of those times. Now the other 33 or so crews that experienced UAS problems didn't follow the exact directions either, but they knew how to aviate and all turned out well.
On another note, he confessed a low level of familiarity with Alternate Law, and he had never heard of alternate Law, 2b....Don't get me wrong, this guy retired off the triple 7, and his skill was at the highest level.

Well, to me, this is, for lack of a better word, scary! Regardless of an Airbus or a 777, both can go into degraded laws with loss of various protections that would be nice to know, being a pilot flying, should it suddenly happen.

[Lyman]

Hiya TD..

Do you not mean "Detent"? Indent is new to me. I think you think I mean
The crew were boffins, now really, I've never met a pilot who is also a boffin.
My meaning was the procedure that should have been followed were created by boffins....

Now as to descent, it is something pilots do at least once every flight, and not too terribly scary...my comment centered round the need to stabilize things, after UAS. Tis easier to stabilize when systems are not maxed out, which for me gets my attention, and I do not need extra worry at this time, UAS?

I have seven miles below me, and as far as 447 was concerned, they had only a half mile UP...push everything to max and what, then worry immediately when to stop? Why not consider UAS an impromptu TOD? Stabilize in a shallow descent, and start trouble shooting... ICE might be a wild card as to AoA vanes, but in truth, don't you think a shallow descent at idle might work, if not, then 60? If fuel is an issue, you may not be ETOPS compliant in the first place, and .....? Now I know you will say, but they need only five degrees, and 100 percent, or a bit less, but isn't it more judicious to demand less of the airframe and engines whilst troubleshooting? Less chance of the "crazy speed?" if one can find five, can one find 0? It brackets cruise AoA?

Let me mention by way of comparison the work around for engine roll back at cruise? Losing power in both engines in a twin is seemingly a bit more worrisome, unless I misunderstand the aces present here....UAS a breeze, a 300 ton glider over the Rockies is...more stressful? Descend, you'll be descending anyway.... Didn't some of the prior crews experiencing UAS decide to descend?

[jcjeant]

Of course, it's easy to say that the a/c type has millions of safe
flight hours. Doesn't mean that the design is right, just that the
edge case problems haven't showed up yet...An easy one to compare .. collapse of bridges ..
Most of them were there for years .. and supported millions of crossing .. when one day :uhoh:
List of bridge failures - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/List_of_bridge_failures)

[Lyman]

Each flight is separate from the next, do not get too comfortable with "millions of flight hours".......how many of those flights had an abnormal? That makes the odds all of a sudden a little shorter.

[syseng68k]

RR_NDB, #1031

All engineered systems are imperfect. The old joke used to be: Cost,
performance or reliability, pick any two :-). Sometimes the
imperfections are the result of well understood tradeoffs at the
design stage, but also things which have been overlooked, or not
accounted for because the designers never expected those conditions
of operation. However, the requirements spec rules the design. If
the spec misses important issues, or there is a bias in terms of
system operation, then that's what is designed into the product.

If you consider that desktop pc operating systems and apps can take
years to get all the bugs out, I wouldn't expect something as complex
as a modern a/c to be bug free, even allowing for the rigorous design
processes. They are some of the most complex engineered systems on the
planet. Note that i'm not casting aspertions in terms of blame, it's
just the way things are.

I bet there will be loads of changes to the systems design as a result
of this and the recommendations in the report. Two additional things
that would seem to make sense are that the fd's are disabled under all
conditions of UAS and other connected faults. Also, that a clear
indication of which law the a/c is running under is displayed unambiguously
at all times...

[Lyman]

Howdy syseng68k....

"I bet there will be loads of changes to the systems design as a result
of this and the recommendations in the report."

Wait, do I have a choice? Cost, performance, and reliability?

I build airliners, I choose cost, and erm, cost...

[RR_NDB]

I bet there will be loads of changes to the systems design as a result
of this and the recommendations in the report.
(http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-52.html#post7342820)

For sure.

Two additional things that would seem to make sense are that the fd's are disabled under all conditions of UAS and other connected faults. Also, that a clear indication of which law the a/c is running under is displayed unambiguously at all times...


On Fukushima / GE:

GE Three - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/GE_Three)

Safety first?

I build airliners, I choose cost, and erm, cost... (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-52.html#post7342829)

Not just in airliners...also on "WMD" :E :}

[alph2z]

How many heated pitots are there on the upstream of each engine ? 1 or 2 ?
That would make 2 to 4 more than the existing 3 airframe-pitots for a total of 5 to 7.

This could be useful IAS data that could be made available to the Flight management computers and pilots.

Since the engines seem to have performed flawlessly at TOGA, high altitude, and at high AOA I would presume some useful data for the computers to help with valid data correlation.

[Lyman]

Different airstream, dependent on demand, not ambient velocity.

[Machinbird]

After 36 close calls, finally a strike out...Not unexpected. As time went on, the standard defense of ownership of the problem becam ad nominee, repeated ad absurdum.
I talked to a gent from the NTSB a week ago. He indicated that there were actually over 50 cases of Airbus UAS that they were able to document. With numbers like that, the odds of one landing "jelly side down" are pretty high.

[Lyman]

It would be important to assess different characteristics airframe to airframe, crew response, etc. do you know if any in-depth analysis is ongoing?

[Hunter58]

Machinbird

For most operators UAS ist NOT a reportable item and therefore the NTSB would not know about it either. To write it in plain languague. UAS is existing in aviation since the introduction of speed measurement and has not been a real problem since the effects were (and I assume still are) part of basic training, starting very early in the training of the most basic aircraft. It is not over 50 cases, it is thousands of cases. But they were not reported since they are a non-event.

[barrymah]

I wonder if the Colonel Xavier MULOT is the same one who is on now on the staff of the French Embassy in Qatar? or is it a coincidence?? I had a google but didn't find any specific on his 'demission' - different from limoge (fired)....(accents missing in the french words).

More conspiracy stuff??

[rudderrudderrat]

It is not over 50 cases, it is thousands of cases. But they were not reported since they are a non-event.
I would agree if the aircraft has natural positive dynamic stability, then it is a non event.
If left alone after a disturbance, it will naturally seek its trimmed angle of attack.

For an aircraft with neutral static stability, then it is a problem.
Any deviation must be recognised and corrected early. Once AF447 had deviated by that much Altitude, it didn't matter how hard they pulled trying to regain FL 350 - it would't work.

Edit: Typo: changed dynamic to static.
Thanks to Clandestino for pointing it out so tactfully.

[jcjeant]

I wonder if the Colonel Xavier MULOT is the same one who is on now on the staff of the French Embassy in Qatar? or is it a coincidence?? I had a google but didn't find any specific on his 'demission' - different from limoge (fired)....(accents missing in the french words).
It has certainly been promoted .. this is normal .. even the U.S. that also happens ... the morons responsible for security the 9-11 were promoted to a higher level :)
More conspiracy stuff?? :8

[Turbine D]

Originally posted by RR_NDB - On Fukushima / GE:
Highly debatable - not appropriate for discussion here - go to JB - Japan Earthquake and Tsunami where this was discussed in detail.
Originally posted by alph2z - This could be useful IAS data that could be made available to the Flight management computers and pilots.
Since the engines seem to have performed flawlessly at TOGA, high altitude, and at high AOA I would presume some useful data for the computers to help with valid data correlation.
Very, very good observation, I think this will/is being looked at, particularly the valid data correlation.
Originally posted by Lyman - Different airstream, dependent on demand, not ambient velocity.
Nonsense, see above plus I suggested this to you a few threads ago.
Originally posted by Lyman - Do you not mean "Detent"? Indent is new to me.Thanks for spotting my error, got my "I" mixed up with my "D" on the keyboard.
Originally posted by Lyman - Each flight is separate from the next, do not get too comfortable with "millions of flight hours".......how many of those flights had an abnormal? That makes the odds all of a sudden a little shorter.However you want to look at it, there are both millions of flights as well as flight hours. The occurrence of UAS is a small number from which all crews managed to recover and fly on, except for one.
Originally posted by Lyman - I have seven miles below me, and as far as 447 was concerned, they had only a half mile UP...push everything to max and what, then worry immediately when to stop? Why not consider UAS an impromptu TOD? Stabilize in a shallow descent, and start trouble shooting... ICE might be a wild card as to AoA vanes, but in truth, don't you think a shallow descent at idle might work, if not, then 60? If fuel is an issue, you may not be ETOPS compliant in the first place, and .....? Now I know you will say, but they need only five degrees, and 100 percent, or a bit less, but isn't it more judicious to demand less of the airframe and engines whilst troubleshooting? Less chance of the "crazy speed?" if one can find five, can one find 0? It brackets cruise AoA?
If a crew can't stabilize at 2.5-5º nose up how can they better stabilize in a "shallow descent? "crazy speed" was a result of pitot icing so how can there be less chance of this going down? And, how does going down result in less stress on the airframe or engines verses going up, particularly if sidestick management is heavy handed? explain?
Originally posted by Lyman - Wait, do I have a choice? Cost, performance, and reliability?
I build airliners, I choose cost, and erm, cost... Luckily, for all concerned, you don't build airliners.

[HazelNuts39]

How many heated pitots are there on the upstream of each engine ? 1 or 2 ?That question has been asked on an earlier thread. I believe the answer was that the FADEC of the GE engine receives its environmental data from ADIRU 1 & 2.

Note that in the Air Caraibes UAS event the discrepancy between the aircraft pitot pressure and the engine P2 caused the ECAM message "ENG 1(2) EPR MODE FAULT". The GE engine is N1-controlled.

[Turbine D]

Hi Hazelnuts39,

Your memory regarding the FADEC & ADIRUs 1 & 2 is correct. The suggestion of somehow using an array of pitot tubes in the engine nacelle as a backup to the normal 3 fuselage mounted pitots would apply to future developed aircraft and engines. I would guess it would depend on the ability to both correlate and then integrate them into the overall aircraft monitoring system. It would require extensive testing to determine if this "backup" system would be operational and not develop icing should the normal pitots fail for openers. I do suspect searching for a solution is being worked in the industry to prevent pitot problems leading to instances of UAS on aircraft being developed or in the conception stage.

[gums]

Thanks Turbine for the 777 poop.

Seems Boeing likes a plane that trims for speed/AoA versus one gee corrected for attitude/climb angle. And the pilot has to command a different trim speed/AoA if I read the data correctly. No automatic THS to maintain commanded gee.

Interesting that pulling/pushing the stick ( stick/yoke, what the hell) against the trim setting has increased force. So there is an artificial force feedback, huh?

I was also impressed with a fairly simple reversion sequence when the primary laws go away.

The stall protection implementation also seems very intuitive to pilots that did not grow up learning to "monitor" the Airbus system do its thing. Hmmmmm.....

Again, thanks Turbine.

[bubbers44]

A pilot should be able to fly any aircraft without needing training. Yes the training is good to teach the differences but no competent pilot should be required to know how to recognize and recover from a stall. That was taught in the first 5 hours of instruction. It is so basic, lower the nose and regain airspeed. AF had two pilots who couldn't do that. I am sure the captain could have but by the time he entered the cockpit the PF had screwed it up so bad he was even confused.

We need to not let automated airplanes make pilots monitors. They both forgot how to fly watching the magenta line.

[TTex600]

Bubbers, stop being dismayed about the pilots and start being outraged at the system that trained them and placed them there.

[bubbers44]

TT, I agree with your statement. This wasn't a problem when I started flying. It is now. Competent pilots were the only people hired when I was. Now with automation competent pilots are too expensive so they hire the cheapest pilots out of pilot school they can find. Sad but true.

[bubbers44]

Embry Riddle pumps out pilots with no experience as soon as Daddy can pay for it. Now they are qualified for a 24,000 a year job with a mere 200,000 help from Daddy. A friend of mine just funded this exact thing.

[Lyman]

TD....

Quote:
Originally posted by Lyman - Different airstream, dependent on demand, not ambient velocity.
"Nonsense, see above plus I suggested this to you a few threads ago."


"The suggestion of somehow using an array of pitot tubes in the engine NACELLE as a backup to the normal 3 fuselage mounted pitots would apply to FUTURE developed aircraft and engines. I would guess it would depend on the ability to both correlate and then integrate them into the overall aircraft monitoring system. It would require extensive testing to determine if this "backup" system would be operational and not develop icing should the normal pitots fail for openers/B]

Are you so eager to utilize the word "nonsense", that you miss the accuracy contained in my post?

By the way, I did not correct your spelling of the word "intent". The word was spelled correctly. I merely asked if you had meant "Detent" instead....

My original comment was based on data you enlarge in your retort to my succinct post. I am full of nonsense, but you think enough of it to widen the prose used to expand on it?

What's up widdat...?

[CONF iture]

I would not think reducing power and going down would be the thing to do as the speed would rapidly increase leading to a speed-speed warning.It is a safe procedure as long there's nobody below.
It has been done by a few crews.
Idle + pitch on the horizon or slighly below do just fine.
Absolutely no risk of overspeed.
Just like a normal descent from cruise level.

There are times when following directions that, or should be, the basis of the word "Aviate" are really important.
To follow directions or switch to a memory item, you need first to understand what you are facing. For them the first signal was the alarm and the red ecam for AP disconnect - Probably also a sudden drop of indicated altitude - I don't think they realized they had to deal with an UAS scenario - Among the reported events, is it possible no one called for the UAS memory item, and no one deselected the FD ?

When it was getting obvious that UAS events in altitude were adding up, it would have been very wise to simulate such scenario during recurrent training : This, is what you may encounter, there are all the associated ecam and alarms, that's what your PFD may look like : THIS IS WHAT YOU NEED TO DO.

I am a bit disapointed we still have not done it in my outfit

Everything is so much easier when you have been properly demonstrated once.

[bubbers44]

Why climb or descend with UAS? Why not stay level, use the altimiter and VSI to maintain altitude? Why bust through everybody elses altitude? I only flew Boeings and MD's but no procedure required changing altitude in cruise because of UAS. Every aircraft has an UAS checklist, get it out and stay level. Just my opinion because I stayed away from the Airbus.

[HazelNuts39]

Probably also a sudden drop of indicated altitude - I don't think they realized they had to deal with an UAS scenario - Among the reported events, is it possible no one called for the UAS memory item, and no one deselected the FD ?Is it possible that a pilot sees the IAS drop from 274 kt to 52 kt in a matter of seconds, and not consider the IAS to be unreliable?

From the Air Caraibes memo (my translation):

"Phase 4, crew reaction
Starting at 22:22:59 during 1m26s the indications of CAS, Mach and altitude are not reliable. The PF flies manually without FD, without FPV, and without A/THR. In that period the various warnings on ECAM, Master Warning, Master Caution, Cavalry Charge, Single Chime, and STALL are numerous. In this extremely charged context, the crew concentrates thus on the piloting of F-OFDF and the application of the checklist QRH 2.21 UNRELIABLE SPEED INDICATION. (...). "

I am a bit disapointed we still have not done it in my outfit

Everything is so much easier when you have been properly demonstrated once. Agreed. It is difficult to understand that this is still not being addressed in training.

[IcePack]

It is not being addressed in training as their are no algorithm's in the sims for high altitude handling. ( most only up to 14000ft) which risks negative training.

[john_tullamarine]

no algorithm's in the sims for high altitude handling

.. a matter of tweaking the box's software.

[CONF iture]

Is it possible that a pilot sees the IAS drop from 274 kt to 52 kt in a matter of seconds, and not consider the IAS to be unreliable?
But do we know what IAS2 was displaying ... ?

The last time we did practice a scenario of UAS at low level, the initial clue that something was wrong came under the warning : WINDSHEAR WINDSHEAR WINDSHEAR
My airspeed was getting in the red, which made sense to me in case of windshear.
As per SOP my call was "WINDSHEAR TOGA" which implies to follow the FD, not to turn them OFF.
That's only when I heard the instructor word : "eh guys ..." that I took a quick look at the other PFD and could remember that one of the exercises for the day was UAS not WINDSHEAR ... The appropriate call was then only made : "UNRELIABLE SPEED"

This is how things can get confusing sometimes.

It is not being addressed in training as their are no algorithm's in the sims for high altitude handling. ( most only up to 14000ft) which risks negative training.
This is not so much about the handling, but how the avalanche of warnings can just mean that : UAS, and how the energy of the PF should go on maintaining a normal pitch attitude for cruise and the energy of the PNF should go on the monitoring the PF performance. The only actions the PNF could perform would be to kill the FD and set the thrust at a normal thrust setting for cruise.

All the concentration and energy on aviate - This is not necessarily easy as the multiple warnings don't seem to stop.

This could be like suddenly switching from a walk in the park to seat in a formula one at 300 km/h

[OK465]

It is not being addressed in training as their are no algorithm's in the sims for high altitude handling. ( most only up to 14000ft) which risks negative training.

IcePack:

What's your source for that statement?

[OK465]

CONF:

It may depend on how the instructor inputs the airspeed variation.

If the indicated aircraft speed is slewed directly, you'll get an effective windshear.

Check and see if you've got a 'Variable Airspeed Drift' malfunction available in the ADIRS section.

Using this malfunction can give a nice approximation of the Air Caraibes situation with appropriate ADR disagree messages and no windshear warning.

[IcePack]

Sims are set up to meet the equivalent test schedule for the type. Most sims handle the same at 35000ft as they do at 14000ft which is definitely not the case for the aircraft. Sorry would have no idea of the source document for that.
Trouble with negative training is that it may be of benefit to get pilots to hold attitude & power but could lead them to believe that the handling is easy which in an A330 at height with an aft C of G due trim tank it is not. Hence in a surprise situation (in real a/c) they may over control or disbelieve the indications.
Whatever, the simulator industry needs to address this short coming IMHO.

[OK465]

Sorry would have no idea of the source document for that.

Then how did you find out about this?

[Lyman]

Question. The aircraft (F-GZCP) was in an airstream that was actively changing directions, from the VSI, her accelerations were brisk in the vertical. This was happening at 2:10:05, both sides. ( before and after). So since I've not seen an answer, let me ask again. The ACARS show a WindShear event of some description. Is there a possibility Bonin was reacting to this? Was there no W/S alert on the ECAM? Seems to me WindShear can cause discrepancies in Pitot reporting, sufficient to not only cause autopilot to drop out, but to degrade the Control Law as well....

[EMIT]

Lyman,

Answers to your 4 questions:

NO
NO
NO
NO (actually the answer may be wrong, 'cause it might just be that to you it really seems so)

By the way, windshear cautions or warnings show up where they belong, on the pilots' Primary Flight Displays (same in Airbus as in Boeing).

[CONF iture]

IcePack,
I cannot tell about the 14000ft stuff, you may be right, but I can tell it is still pretty easy to over control at 35000ft in a simulator. IMO the handling would still require a LOT of attention.
For the record, despite the fuel in the tail, the CG for AF447 was still very much fwd compared to the ideal target for fuel saving.

OK365,
You are most probably correct.
I'm not too aware of the different possibilities for the sim as I have never occupied that back seat. What I can tell is that the instructor seemed surprised too.

[HazelNuts39]

The ACARS show a WindShear event of some description.The ACARS message you're referring to has the Meaning (ref. Interim#1, p.49):
"This message indicates unavailability of the reaction to windshear detection function"

[RetiredF4]

IcePack
Sims are set up to meet the equivalent test schedule for the type. Most sims handle the same at 35000ft as they do at 14000ft which is definitely not the case for the aircraft. Sorry would have no idea of the source document for that.
Trouble with negative training is that it may be of benefit to get pilots to hold attitude & power but could lead them to believe that the handling is easy which in an A330 at height with an aft C of G due trim tank it is not. Hence in a surprise situation (in real a/c) they may over control or disbelieve the indications.
Whatever, the simulator industry needs to address this short coming IMHO.

Read it somewhere, however couldn´t find it. Stumbled on another pdf though.

Validation of stall recovery technique and training from Airbus March 2011 (http://www.scribd.com/doc/71805049/Validation-of-Stall-Recovery-Technique-and-Training-Claude-Lelaie)

edit: another look from april 2012
aviation week (http://www.aviationweek.com/Article.aspx?id=/article-xml/BC_04_01_2012_p34-432588.xml&p=1)

[CONF iture]

I am afraid that Australian ATSB has shown utter disregard for your ideas that fix is inadequate and in its final report of upset to A330 near Learmonth has found actions by Airbus quite acceptable.
Where did I write inadequate ?
It is only a temporary fix where the pilot needs to be quicker than the malfunction to badly bite one more time.
But as usual you redirect the subject as you cannot assume your writing :
Many a claim was made on this rumour network that oh-so-complicated-Airbus-took-the-controls-away-from-me-when-it-shouldn't-have. None of them were substantiated except St.Johns and Bilbao - that's fixed now.

[Lonewolf_50]

CONF iture

Same reply that 1) The conservative approach would be to make sure that automation stays out of the way when data are identified as unreliable.
I can see the appeal of that (as I am very much a fan of stick and rudder flying). I think henra's response answers some of the "why" the system is as it is.

TTex

Make sense to who, or better said, to WHAT?
In this accident we have an aircraft designed to be flown by computers that suffers a GIGO computer issue that convinces the computers to give up on their job.
Which leaves the pilots with a system designed to be flown by computer and they now have no computer or at least not all of the computer.
BUT, it still wants to be flown like it is a computer because only PART of the computer system gave up, the rest is still working and it only knows computer sense.

I ask again, make sense to who or what?

Forgive my english/grammar, Texan is my native language and i'm in a hurry.

I understood you perfectly. :ok:
It makes sense to whomever bought the plane with the objective being a smooth ride in a modern airliner. I will suggest to you that, for the most part, as evidenced by most of the 228 casualties being strapped in, that even as it fell from the sky it was a smoother ride than one might expect for out of control flight. (Then again, many of those strapped in might have strapped in, and then dozed off, a buffet here or there not noticed, be it turb or stall ... )


The Airbus flies already very well under Direct Law, and manual trim is part of that direct, just like the Cessna, or the Airbus 310

The only question I'd have on that is: how often do you get to practice that?

Lyman

Easier to descend than climb.
Gravity assisted flying! What will they think of next! :-)

Sorry for that, I could not resist.

[Clandestino]

If you are going to be picky, during roll out, you are actually in a sub mode of Direct Law called Ground Mode.Thank you for being nitpicky for me.

I don´t like the approach to diagnose UAS by System output. Neither do I. BEA is also unhappy but it issued no recommendation on fixing it. What you fail to understand is...

Block garbage to enter System would be better?...the pressure that hit the total pressure sensor was not the real one due to clogging of the pitot, but such reduced pressure resulted in calculating airspeed of about 52 kt at the minimum and this is valid speed during t/o run or landing roll and cannot be rejected by simple algorithm! This is not readily identifiable to computer as a garbage! It can be identified as such only by someone who has a whole picture of the aeroplane state in his CPU and can recognize that sudden drop from 270 kt to 52 without aeroplane starting to fall or being torn apart in severe turbulence actually means speed display is totally wrong and we call that entity "a pilot". You just can't teach the computer to compare all the parameters and come to intelligent solution, if you try, you can only end up with set of instructions so convoluted its execution will be totally unreliable. Farthest Airbus came is displaying "CHECK GW" message when computer detects discrepancy between input weight, airspeed and AoA - it can not determine which is which so output is made to warn about the most common failure, to input wrong weight into FMGS. A lot of guesswork but it's best that can be done for the time being.

Sadly, the (non adequately trained) crew of AF447 were:Question of adequate training is another can of worms. How come other AF crews dealt without much fuss with UAS if AF training is inadequate? It is not just about training, it is also about selection. Starting from the first flight in glider, ending when the logbook is closed for good.

I don't think the test pilots that approved the 5 degrees nose up and climb power tried it with blocked pitot tubes. Do you have a slightest idea who writes and approves the procedures?

The trapped pitot pressure and the decreasing static pressure would cause an indicated airspeed increase and at some point an overspeed warning So it would! So freaking what? Pilot who would seriously consider acting IAW overspeed warning in UAS situation must be totally "destructured", to use BEA term.

HN.... Why would the boffins select a climb, at all, in the first place?Panic, caused by sudden realization that something is wrong but one has no clue what it is or what should be done. So doing first thing that crosses his mind and disregarding absolutely every clue it wasn't good idea in the first place.

R&D must be done to improve current situation. What situation?

Why not protect the plane to REC MAX apogee. Hard limit (Airbus SAS approach) I have read many a misconception about Airbus protection, this one goes into top tier. No altitude protection is offered ever on Airbus as AoA makes it irrelevant. No hard air data based protection is available in alternate laws as there's no sufficient redundancy to guard against the unwarranted activation of the protection.

Poor training. As I've stated more than once on this topic, my training was no better.How come other 36 crews went through UAS ordeal unscathed? Better training than yours?

If the systems fail and give no information, then fineSo it is. No electronic part of the system failed in AF447 case. It just wasn't fed the right pressure.

but to fail and give incorrect information is extremely dangerous Problem is that many a PPRuNer has noticed it is dangerous only when it resulted in 228 deaths and all of a sudden there are righteous demands, very similar to ones made by certain young F/O

Captain Hughen, this is all an anachronism. We belong in the modern world and should therefore be secure. Please arrange a remedy for this grievous mistake at once.
At least he was so forthright to humour himself once the fright loosened his grip.

Simply because Pitot´s may fail SIMULTANEOUSLYSo what? I have flown aeroplane with single pitot and then it got blocked. There's always way out.

I would agree if the aircraft has natural positive dynamic stability, then it is a non event. If left alone after a disturbance, it will naturally seek its trimmed angle of attack. I have to warn everyone that trying to explain some aspect of Airbus FBW while not being versed in basic aerodynamics tends to produce entertaining, if not true or otherwise useful , results. What you are referring to is static stability and that airbus lacks it in normal and alternate law is total non-event.

Any deviation must be recognised and corrected early. Once AF447 had deviated by that much Altitude, it didn't matter how hard they pulled trying to regain FL 350 - it would't work. What?!? AF447 did regain FL350 by pulling, if only fleetingly as it passed through it on her final descent! Now, if only they pushed...

Bubbers, stop being dismayed about the pilots and start being outraged at the system that trained them and placed them there. If we assume that Airbus is dangerous by design, shouldn't we be praising the system for always putting the super-pilots in the cockpit that made it home and failing just once? Of course not.

I don't think they realized they had to deal with an UAS scenario You are right. How could they realize when they were suddenly faced with 200+ kt drop in IAS?



But do we know what IAS2 was displaying ... ?
BEA does. 88, 93, 94.

It is only a temporary fix where the pilot needs to be quicker than the malfunction to badly bite one more time.Dear CONF iture, by know you should have really known better than assuming I would link to the report without reading it. So: 1. QF72 was single occurrence in 28 million hours of flight 2. temporary fix of switching off the faulty ADIRU was later supplemented by rewriting the FCPC algorithms. I will suggest you should stop burying yourself, just because I know you will not listen to me.

[RetiredF4]

Another read i could find concerning Loss of Control in Flight
Training Foundations and Solutions (http://iaftp.org/wp-content/uploads/papers/Brooks-Loss_Of_Control_In_Flight_Training_Foundations_And_Solutions .pdf).


Some bits out of it:

What Changed: Uncovering the Problem
Part of the predicament has nothing to do with LOC-I at all; in fact it is the reduction of other accident causes that left LOC-I as one of the last remaining causal factors to be “tamed”. To be clear, the overall number of accidents and fatalities due to LOC-I have not been increasing. It is the improvement in other accident categories that has resulted in the emergence of LOC-I as the leading cause of fatal accidents in air transportation worldwide. It’s as if when the “swamp” of the aviation accident pool was drained of other causal factors, the “snakes” of LOC-I were exposed. It is only in the past five years that LOC-I has overtaken Controlled Flight Into Terrain (CFIT) as the leading fatal accident category among airline
aircraft worldwide. While other accident areas have improved, LOC-I has stagnated at an unacceptable rate.


The lack of improvement in LOC-I is evidenced by it’s relative contribution to the overall fatality rate. From the period of 2001 to 2008, LOC-I experienced a 29% increase in the contribution of this category
towards the overall fatal accident rate. For the ten year period ending in 2008 the next closest accident category was CFIT, at 20% (roughly one half of LOC-I fatalities).


Loss of Control in Flight as a percentage
of Overall Fatalities:
Year percentage
2001 30.4%
2006 30.6%
2008 39.5%


The Relative Threat: Higher risk, less effective training
To get a perspective on whether or not we should be concerned about a reduction in all-attitude experience in the cockpits of the world’s airliners, we will examine the relative statistical threat of a fatal accident from several categories of accidents.

The worldwide chances of an LOC-I death by comparison to other accident categories

Runway Excursion (Combined Take Off & Landing): x 2.3
Non-engine systems failure: x 5.6
Runway Incursion (By a Vehicle, Aircraft, or Person) : x 9.1
Engine Failure: x 879.5

[RetiredF4]

Clandestino: What you are referring to is static stability and that airbus lacks it in normal and alternate law is total non-event.

You should tell BEA. They obviously dont know about it.

BEA Final report
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.

Clandestino: You are right. How could they realize when they were suddenly faced with 200+ kt drop in IAS?

You should have helped BEA with their report. They got it wrong again.

BEA Final report 2.1.2.4 Identification of the situation
Three seconds after the autopilot disconnection, the ECAM displays no information that is likely to point to a speed indication problem:
The ECAM mentions a maximum speed that should not be exceeded but does not mention a minimum speed. This could lead crews to suppose that the main risk is overspeed. In the absence of any reliable speed indication, this might lead to a protective nose-up input that is more or less instinctive.

..........
Thus, having identified the loss of airspeed information, the PNF turned his attention to the ECAM, undoubtedly in an attempt to refine his diagnosis and to monitor any actions displayed. He started to read the messages, and consequently called out the loss of autothrust and the reconfiguration to alternate law. The successive display of different messages probably added to the confusion experienced by the crew in its analysis and management.
In the absence of a specific message expressing detection of unreliable speed by the systems, the crew was unable to identify any logical link between the symptoms perceived and these ECAM messages. The impression of an accumulation of failures created as a result probably did not incite the crew to link the anomaly with a particular procedure, in this case the “Vol avec IAS douteuse” procedure.

[syseng68k]

The last time we did practice a scenario of UAS at low level,
the initial clue that something was wrong came under the
warning : WINDSHEAR WINDSHEAR WINDSHEAR

My airspeed was getting in the red, which made sense to me
in case of windshear.

As per SOP my call was "WINDSHEAR TOGA" which implies to
follow the FD, not to turn them OFF. That's only when I heard
the instructor word : "eh guys ..." that I took a quick look
at the other PFD and could remember that one of the exercises
for the day was UAS not WINDSHEAR ... The appropriate call was
then only made : "UNRELIABLE SPEED"
So, in the case of UAS, you could get a windshear warning and / or
a stall warning. Neither of which are correct. Wonder what else ?.

In the case of uas, one would think that the warning system would
at least consult the IRU and other available sources to correlate
the data before presenting it to the crew.

I guess that's all ok though, yes ?...http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/eek.gif

[bubbers44]

I flew with pilots that would not have done what they did. I wouldn't. If we lost airspeed we would maintain pitch and cruise power as they should have. Get out the UAS checklist and press on. No stall, no panic, but they didn't. Experience helps when you didn't spend your whole short career monitoring an autopilot.

[RR_NDB]

Hi,

Clandestino:

Originally Posted by RR NDB
I don´t like the approach to diagnose UAS by System output.

(http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-54.html#post7346073)

I put:

I don´t like the approach to diagnose UAS by System output. As showed in an Airbus SAS paper mentioned in an earlier post. This can be improved and in AF447 case seems very important.

In an earlier post i observed:

In this paper one member of Airbus SAS design team sez the pilots are responsible for the UAS diagnosis. (http://alexandreg.blog.lemonde.fr/files/2012/07/Safety-First5.Jo%C3%AAlle-Barthepdf.pdf)

IMHO this is dangerous. Digital signal processing of air speed analog data can inform UAS onset to the crew before System start to process garbage.

Neither do I. BEA is also unhappy but it issued no recommendation on fixing it. What you fail to understand is...

The recommendations will generate a better design. I hope an UAS DSP subsystem will be eventually used.

Please could you explain: "What you fail to understand is...". What you mean?


Question of adequate training is another can of worms. How come other AF crews dealt without much fuss with UAS if AF training is inadequate? It is not just about training, it is also about selection. Starting from the first flight in glider, ending when the logbook is closed for good.

:ok:

Even morons could deal with UAS if are trained to use a DSP UAS detector. :)

(Air speed is important. Pitot´s seems obsolete. Thales version used in F-GZCP was obsolete)

Air speed anomalies are frequent and potentially affect the stability of the System. The current situation is not good.

The 3 redundant (Pitot´s and subsystems, CPT, FO and Stand By) System elements failed SIMULTANEOUSLY. No redundancy, therefore. Better to use a single element. :} :{

On the REC MAX protection please don´t consider it so seriously. Actually good pilots can unload the wing above REC MAX and save the day.

[RR_NDB]

Hi,

bubbers44:

Experience helps when you didn't spend your whole short career monitoring an autopilot.
(http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-54.html#post7346225)

:}

[Lyman]

BEA...

"Thus, having identified the loss of airspeed information, the PNF turned his attention to the ECAM, undoubtedly in an attempt to refine his diagnosis and to monitor any actions displayed. He started to read the messages, and consequently called out the loss of autothrust and the reconfiguration to alternate law...."


In the prior paragraph, they reference a three second interval post a/p loss, and note the ECAM has not displayed the Law reconfig. It was sixteen seconds later the PNF called "Alternate Law".

Three seconds after the autopilot disconnection, the ECAM displays no information that is likely to point to a speed indication problem:

What is the point of This timeline, and the two time intervals? Thay mention the possibility of nose up, but make no inference other than, "possible confusion..."


The ECAM mentions a maximum speed that should not be exceeded but does not mention a minimum speed. This could lead crews to suppose that the main risk is overspeed. In the absence of any reliable speed indication, this might lead to a protective nose-up input that is more or less instinctive.


Sensory overload? The pilots? Or BEA? What a jumble...

[RR_NDB]

BEA Final report 2.1.2.4 Identification of the situation
Three seconds after the autopilot disconnection, the ECAM displays no information that is likely to point to a speed indication problem:
The ECAM mentions a maximum speed that should not be exceeded but does not mention a minimum speed. This could lead crews to suppose that the main risk is overspeed. In the absence of any reliable speed indication, this might lead to a protective nose-up input that is more or less instinctive.

Thus, having identified the loss of airspeed information, the PNF turned his attention to the ECAM, undoubtedly in an attempt to refine his diagnosis and to monitor any actions displayed. He started to read the messages, and consequently called out the loss of autothrust and the reconfiguration to alternate law. The successive display of different messages probably added to the confusion experienced by the crew in its analysis and management.
In the absence of a specific message expressing detection of unreliable speed by the systems, the crew was unable to identify any logical link between the symptoms perceived and these ECAM messages. The impression of an accumulation of failures created as a result probably did not incite the crew to link the anomaly with a particular procedure, in this case the “Vol avec IAS douteuse” procedure. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-54.html#post7346116)

K.I.S.S. has it counterpart: Keep It Complex Stupid :}

Question: How they could diagnose the UAS? (The so called, non event)

:mad:

We still today have two problems:

1) Important (redundant) elements prone to fail simultaneously
2) Diagnosability of UAS

[Lyman]

RR, this is BEA's answer to your question:

"In the absence of a specific message expressing detection of unreliable speed by the systems, the crew was unable to identify any logical link between the symptoms perceived and these ECAM messages. The impression of an accumulation of failures created as a result probably did not incite the crew to link the anomaly with a particular procedure, in this case the “Vol avec IAS douteuse” procedure."

That takes us to 2:10:22, with PF's "protective Nose Up", and half way to STALL.

Without Artificial Horizon, his confusion re: Pitch, airspeed, and Vs plus his preoccupation with a very real roll, and an imaginary overspeed, and STALL is creeping up quite close.

[RR_NDB]

Lyman, (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-55.html#post7346292)

Surprised til the end...

Simple: UAS must be informed immediately. Before any System processing.

(Why not by a dedicated "processor", a retrofit?)

[Lyman]

Hi Mac

All things considered, it would be safer to take all probes off line and extinguish IAS displays, followed by a message on the PFD. "airspeed INOP".

It wouldn't matter whether it was real or not, if real, the message on the ECAM is [/B]UAS / SET PITCH / MONITOR POWER[/B] if it is not real,

TEST/ONLY.... Three's your startle "drill" for the trip!!

[CONF iture]

BEA does. 88, 93, 94.

You are correct - Thank you for the head up.

Dear CONF iture, by know you should have really known better than assuming I would link to the report without reading it. So: 1. QF72 was single occurrence in 28 million hours of flight 2. temporary fix of switching off the faulty ADIRU was later supplemented by rewriting the FCPC algorithms. I will suggest you should stop burying yourself, just because I know you will not listen to me.
was ?
will is more accurate as the RED OEB is still applicable.
But why bother with a RED OEB and a rewriting of the FCPC algorithms after all as the occurence is behind us.
I think I could take that OEB out of my QRH and you should talk to the QF72 crew and also to the pax who made that mess :

http://i35.servimg.com/u/f35/11/75/17/84/af447_10.png (http://www.servimg.com/image_preview.php?i=153&u=11751784)


I will suggest you should stop burying yourself, just because your ego prevents you to acknowledge how your comment is uninformed :
Many a claim was made on this rumour network that oh-so-complicated-Airbus-took-the-controls-away-from-me-when-it-shouldn't-have. None of them were substantiated except St.Johns and Bilbao - that's fixed now.

[TTex600]

Quote:
Originally Posted by TTex600
Poor training. As I've stated more than once on this topic, my training was no better.
How come other 36 crews went through UAS ordeal unscathed? Better training than yours?

Apples to Oranges. I've never had a UAS ordeal, so we just don't know. I should have included the qualifier that my Airbus training was no better. My other jet training was superb.

But to answer your question, I'll take a guess that most of the 36 other crews were flying the 330 as their second/third/fourth etc, transport category swept wing jet. Maybe their Bus training was inadequate, may not. But they likely had previous experience to fall back on either way. If I read the BEA report correctly, the two guys at the controls for AF447 were essentially Airbus only.

To address your other claim, I'm not arguing that the Airbus design is "dangerous by design". Your confusing me with some of the other multitude of people you've argued with these last six years.

[bubbers44]

I'll take a guess that most of the 36 other crews were flying the 330 as their second/third/fourth etc, transport category swept wing jet. Maybe their Bus training was inadequate, may not. But they likely had previous experience to fall back on either way. If I read the BEA report correctly, the two guys at the controls for AF447 were essentially Airbus only.


Exactly, the other 36 crews would not have pulled up to 15 degrees for no reason. They knew how to fly an airplane with no airspeed. These two didn't.

[jcjeant]

Panic, caused by sudden realization that something is wrong but one has no clue what it is or what should be doneYou been very explicit, but you do not deliver us all your thoughts ..
What you said ( if I read between the lines .. "a grand art" ) is that the person in charge had not to be there because it is incapable of knowing what is happening or know what to do ...
If it was a truck driver who has had his place .. it would be understandable that he does not understand what happend when the autopilot is going off
This is not the case .. this pilot ( driver ?) is an employee of Air France .. selected by Air France and trained in his trade and followed by assessments made ​​by Air France and under the supervision of regulators rules
Why Air France or the regulators in the first place let fly an A330 by a truck driver ?
That's not funny for the people at the rear ... when they hear a hostess ask if there is pilot in the cabin ...

[BOAC]

Without Artificial Horizon, his confusion re: Pitch, airspeed, and Vs plus his preoccupation with a very real roll, and an imaginary overspeed, and STALL is creeping up quite close. - have I missed something or are you starting a wild hare running?

[henra]

Without Artificial Horizon, his confusion re:

What do you assume was displayed on the PFD????
The local TV channel? :E

All that nice coloured lines and bars and vectors aside, what do you assume does the blue and brown indicate?

[CONF iture]

The only question I'd have on that is: how often do you get to practice that?

Time to time as the malfunctions activate the direct law, manual trimming is necessary.
Also, some exercices as manual back up and lost of elevators put manual trimming as the main source for pitch control.
Trimming remains natural for a pilot, and also a source of satisfaction in the way to handle manual flying. It is almost disturbing the first time you experience the Bus in manual flight, and that possibility to trim is taken away from you.

But to answer your question, I think that for every recurrent we should be given a 15 minutes period in direct law with no FD and practice some basic exercices. I hope this will come.

[Lonewolf_50]

Lyman:
Without Artificial Horizon, his confusion re: Pitch, airspeed, and Vs plus his preoccupation with a very real roll, and an imaginary overspeed, and STALL is creeping up quite close.
Per BOAC and henra: whence comes this assertion? I thought we put that to bed a while back, when I wandered off the reservation on the 'tumbling gyros' jag and was reeled back in by some kind contributors here.
The Rolling Stones will supplement the sound track with an excerpt from the unreleased album, Exile From Tolouse Street:

"You got me ro-oh-oh-lin, call me the Tumblin' Gyyyy-ros!"

Tex
But to answer your question, I'll take a guess that most of the 36 other crews were flying the 330 as their second/third/fourth etc, transport category swept wing jet. Maybe their Bus training was inadequate, may not. But they likely had previous experience to fall back on either way. If I read the BEA report correctly, the two guys at the controls for AF447 were essentially Airbus only.
This is where "the industry" may need to speak up. Maybe only the pilot's Associations are in a position to do this. (Quite possibly I am off the reservation on this as well. Reel me in, if need be, Tex).

CONF iture

Time to time as the malfunctions activate the direct law, manual trimming is necessary.
Also, some exercices as manual back up and lost of elevators put manual trimming as the main source for pitch control.
Trimming remains natural for a pilot, and also a source of satisfaction in the way to handle manual flying. It is almost disturbing the first time you experience the Bus in manual flight, and that possibility to trim is taken away from you.
But to answer your question, I think that for every recurrent we should be given a 15 minutes period in direct law with no FD and practice some basic exercices. I hope this will come.


Thank you for that concrete and informative reply. :ok::D

[Lyman]

Lyman:


Quote:
Originally Posted by Lyman
Without Artificial Horizon, his confusion re:

What do I base my assumption on? Eyewitness testimony.

What do you base yours on?

[bubbers44]

Reading thousands of comments here I don,t recall one saying all attitude indicator were inop, even one. VSI wasn't, inop either.

[Lyman]

I don't either bub, but that isn't what we're talking about...

EG: it was the 'group' that decided he hadn't lost his vario, though he said it wasn't working. We decided it was working fine, but pegged.

Ballsy, eh?

[DozyWannabe]

What do I base my assumption on? Eyewitness testimony.

OK - where does anyone say "we have no ADI"?

Bet they don't.

Bet you're making it up.

[jcjeant]

OK - where does anyone say "we have no ADI"?I agree ... in the CVR .. it's no stance like "we have no ADI"
Nevertheless ... it's a captain stance:
2 h 12 min 23,0
The wings to flat
horizon the standby
horizon
Why tell to use the "Standby Horizon" instrument ... if you have a ADI ( certainly more accurate and easy to read ? )
Or captain believe the ADI's are no more reliable (by comparing the 3 instruments reading ?)

[DozyWannabe]

Maybe a reference to the fact that they're all showing the same thing?

I realise this is my own reading, but I have to say I think it would be unusual for the captain to repeatedly point out and make reference to devices that weren't working without saying they weren't working. Especially in the context directly following an order to arrest roll oscillation.

[Lyman]

Jcjeant...


Quote:
OK - where does anyone say "we have no ADI"?


Hi dozy. Proof? Unlike your request re : stick visibility, which was discredited, I have proof the possibility exists, sufficient to claim something like....

"We have no indications"'. "Standby horizon, wings level"

It was the actual text of the Pilot, not a surmise from me? In the presence of actual proof that the panel was goofed, you claim the ADI was fine, simply because it wasn't singled out? What unmitigated, or ignorant, gall.

Ever the optimist, I will wager this: when the rest of the CVR is known, I'll bet dollars to doughnuts we will grasp what is not known about many things.

Are we on?

Was Captain saying the Standby should be followed? Or that he considered it goof? Oh, "my vario is not working...". Captain: "OK....." (SIC)...

The text creates questions, to claim otherwise is outrageous....

"Horizon was fine, of course, it must have been....". Excuse Me?

[DozyWannabe]

Hi dozy. Proof? Unlike your request re : stick visibility, which was discredited, I have proof the possibility exists, sufficient to claim something like....

"We have no indications"'. "Standby horizon, wings level"

Here you're conflating two utterances in the CVR transcript which are over 20 seconds apart. The PF's reference to displays is at 02:12:01. The Captain's statement, which in the English version reads:

"The wings to flat horizon the standby horizon"

does not occur until 02:12:23.

Why would the Captain order his crew to arrest roll oscillation ("wings to flat") and make immediate reference to the horizons if the horizons weren't working?

It was the actual text of the Pilot, not a surmise from me? In the presence of actual proof that the panel was goofed

Proof? It looks more like a subjective reading of the CVR transcript to fit your own prejudice.

you claim the ADI was fine, simply because it wasn't singled out? What unmitigated, or ignorant, gall.

No, I'm saying that at no point are the ADIs referred to as not working, and in fact it makes more sense to suggest that they were working given the Captain's orders. I'm not saying I'm right, but a dispassionate reading of the transcript is more in favour of the ADIs working than not.

[Lyman]

Dozy,

Why would the Captain order his crew to arrest roll oscillation ("wings to flat") and make immediate reference to the horizons if the horizons weren't working?"

"Why would the Captain order his crew to arrest roll oscillation ("wings to flat") and make immediate reference to the horizon(s) if the horizon(s) weren't working?

He did not refer to the plural, did he? Yet you would have us believe he did? That is simply dishonest.

On this,

"No, I'm saying that at no point are the ADIs referred to as not working, and in fact it makes more sense to suggest that they were working given the Captain's orders. I'm not saying I'm right, but a dispassionate reading of the transcript is more in favour of the ADIs working than not."

No more questions......you have said well what I struggled to say...

Who wants favour? Who wants the truth?

[DozyWannabe]

Who wants favour? Who wants the truth?

Everyone wants the truth*, but in some cases the best that can be managed is an informed supposition.

In this case, the Captain's order to level the wings followed by reference to the horizons is neither followed by a comment to the effect of "but we have no horizons" from the crew, nor does the Captain say that the horizons are out. We know that the altimeter was working from the callouts and we know that it's likely that attitude indications were displayed too ("you're going up so go down"). The idea that the flight deck displays went entirely dark is not supported by the evidence we have.

He did not refer to the plural, did he? Yet you would have us believe he did? That is simply dishonest.

Not at all - we have an earlier instance of his speech pattern where he refers to things sequentially : "There I don’t know there it’s going down". If he'd been implying that either or both the PFDs were unreliable then he'd likely have mentioned the ISIS ADI only. Instead he says "the horizon the standby horizon". I ask again - if any of the ADIs weren't working, why did he or either of the F/Os not say so?

CVR reading can be a very subjective game, which is why the people that do it tend to specialise in that area to the exclusion of all else. Picking the AF447 CVR apart is relative child's play compared to a case like TE901, in which two very different readings have split opinion on the accident for decades, or Palm 90 - where the NTSB's specialist spent literally months trying to determine whether the response to the Engine Anti-Ice call-out was "On" or "Off" (eventually it was determined to be "Off").

[* - EDIT : not only including me, but *especially* me. Given that 99.9(rec)% of all the flying I'll ever do is as SLF it is not in my interest to defend a problematic or dangerous design on the part of any manufacturer. This is one of the reasons I get extremely vexed when I'm accused of "defending" Airbus.

But at the same time I have no truck whatsoever with the propagation of misinformation and falsehood for the sake of political point-scoring, and the fact is that the amount of hot air I've seen talked about Airbus over the years would be enough, were it to be harnessed and pumped into the fuselage, to put every airframe they ever made into the stratosphere in perpetuity.]

[bubbers44]

I guess if you stalled and were in a 40 + degree nose attitude down when the captain got there he would have a hard time trying to figure out where the blue sky was on the attitude indicator. It wasn't visible. The attitude indicator is made for competent pilots not these guys.

[gums]

I am becoming increasingly disturbed by some of the assertions here regarding the longitudinal static stability characteristics of the 'bus.

From every document I can find, I see that the jet has a decent positive static stability characteristic. In short, the jet wants to achieve a trimmed AoA except for the actions of HAL. I see a feature that allows moving fuel aft to get a better configuration that relieves the HS/elevators from exerting a donward force. So we get lower "trim drag", and it's a good thing a lot of the time.

The cee gee of AF447 was nowhere near the aft cee gee that results in an unstable longitudinal static stability condition.

Thanks to Turbine, I have a limited explanation on the B777 control law philosophy. The thing seems to be more biased to AoA than to a gee command corrected for pitch. So this provides the "feelings" that many of us learned to deal with long ago. Trimmed for a low AoA and holding backstick, then release the stick and the sucker goes nosedown. And vice versa.

The actions of a cosmic FBW system that overcomes the basic aero characteristics of the jet can be neat, but can be fatal.

I can only speak from my experience in the first fully FBW jet to be fielded in more than a handful of airframes or test vehicles. The Earth was still cooling. Anybody else here with such experience would be welcome to contribute to this discussion.

As with the 'bus, our FBW system was heavily biased toward gee command. We didn't see a significant AoA contribution unless pulling hard and getting slow. So we were basically speed neutral in level flight and only basic aero drag kept us from getting faster and faster or or vice versa. No big deal, as we didn't spend hours of "monitoring" the computers.

The gee command of the 'bus is a major factor in moving the THS. The system tries to reduce the pilot stick pressure for the commanded gee. NOT THE AoA!!!!! Boeing seems to like the AoA for trimming.

So the BEA report correctly points out that the jet would have gone into test pilot conditions with the pilot commanding neutral stick once the pitch attitude and power setting allowed it to enter a stall.

The 'bus FBW laws' emphasis upon gee command and the lack of attention to AoA inputs was a major contribution to this incident. I completel;y agree with the others here that holding initial attitude and power for "x" seconds would have saved the day.

I would hope that the major carriers would try to expose their pilots to some of the edges of the envelope either in the sim or the actual jet.

[john_tullamarine]

40 + degree nose attitude (I presume your reference to "down" was intended to be up for the pitch attitude but down for the resultant path vector ?)

I don't think that your observation is quite right .. although I may have missesd a subtlety in your point along the way ..

I would have to wade back through eternity to find the numbers from earlier posts but, as I recall,

(a) the aeroplane was moderately nose up in pitch attitude

(b) the ball would have looked reasonably normal-ish albeit much too nose up compared to normal flight and pitch values

(c) the flight path vector (again I can't recall the specific term for this aeroplane) was showing a steep descent ..

(d) and the two, taken together, gave an approximation of alpha .. which was the relevant 40-odd degrees measure.

That is to say, presuming that the instrument was presenting a picture, the ball indication would have been instantly obvious to any competent I/F pilot and the Commander probably (? - just my thoughts) read the ball right straight away but, with the overall bizarre situation for an airline pilot .. it was going to take him a little while to figure out just what in the blue blazes was going on and where his sidekicks had got the aeroplane to in the few minutes that he was out of the cockpit.

.. it was a great tragedy that the situation didn't give him the time he needed to

(a) figure out the story, and

(b) fix it

before the pond cut short his options.

In which case we wouldn't have this marvellously huge expanse of threads and posts on a single topic.

[rudderrudderrat]

Hi John,
the flight path vector (again I can't recall the specific term for this aeroplane) was showing a steep descent ..
I don't think the flight path vector (bird) was ever displayed. The HDG/VS TK/FPA button on the FCU needs to be pushed in order to bring up the display. I can't find any reference saying they did.

Normally a crew would ask for "FDs off, bird on" - but this crew kept their FD switches on, and seem to have been trying to follow erroneous FD commands (e.g. VS +1400/min during the descent Page 96 Final report).

[HazelNuts39]

Question for our french-speaking posters:

2 h 11 min 42,5 bruit d’ouverture de la porte du cockpit
2 h 11 min 42,5 CPT: eh qu’est-ce que vous (faites)
2 h 11 min 46,7 bruit similaire à la fermeture de porte
2 h 11 min 52,6 CPT: alors tiens prends, prends ça
2 h 11 min 55,0 PNF: prends ça là prends ça (*)
2 h 11 min 57,0 PNF: essaye de prendre ça
2 h 11 min 58,2 PF: Je… j’ai, le problème c’est que j’ai plus de vario là

Looking at the picture of the standby instrument posted in Turbine D's post #923:
Are the captain and the PNF pointing at the standby instrument, and is the PF replying that his problem is that the standby instrument doesn't have a VSI?

Turbine D post #923 (http://i1166.photobucket.com/albums/q609/DaveK72/PastedGraphic-1SB.jpg)

[john_tullamarine]

I don't think the flight path vector (bird) was ever displayed.

I would have to wade back into the depths of the threads to establish that .. perhaps I had misread that the indication was there. However, if not, then I would have expected the Commander to have asked for it once he figured out the lilkely scenario .. the pond cut his opportunities short ...

[HazelNuts39]

JT,

From the final report, paragraph 1.16.5.6:
It should however be noted that an error was made in the analysis of the “FLAG FPV ON PFD CAPT (F/O)” message. This had been explained by the combination of two conditions: that the TRK-FPA mode had been selected by the crew, and that the FPV was unavailable. In fact, the first of these conditions is not taken into consideration when sending the message to the CMC. The fact that the status of the FDR parameter, which indicates the transition from HDG-VS mode to TRK-FPA mode, did not change during the flight confirms that the crew did not at any time select TRK-FPA mode.

[john_tullamarine]

Thank you, kind sir.

[CONF iture]

Are the captain and the PNF pointing at the standby instrument, and is the PF replying that his problem is that the standby instrument doesn't have a VSI?
That could make sense, I agree.
But due to the position of the ISIS on the dash, it is usually the job of the guy seated on the captain's seat to assume the controls. Telling the guy who is seated on the right side to fly on the instruments facing the guy seated on the left side is not logic, especially when the comment is also from the guy seated on that left seat.

But the comments following yours are also very interesting :
2 11 58 PF: le problème c’est que j’ai plus de vario là
2 12 01 CPT: d'accord
2 12 01 PF: j'ai plus aucune indication
2 12 02 PNF: on a aucune indication qui soit valable

The vertical speed indicators when indicating something were probably not indicating a steady 10000 feet/min in descent. In relation to the roll of the aircraft, those indications were vastly varying between themselves. How were the altitude indicators ... ?

[Lyman]

Is there a possibility that Captain was reading and prompting PF with ISIS due PF's horizon was n/a, INOP?

[bubbers44]

john, you are right, 40 + angle of attack after the pitch went from +15 degrees to about - 10 degrees. Unless the captain saw how they managed to put them selves in that position he would have difficulty sorting it out initially not having ever seen it before.

The flight recorder shows their IAS dropping off drastically when they pitched up. Wouldn't their flight instruments tell them the same thing with a frozen pitot tube? Did they just follow the FD? If so maybe being an old farght isn't so bad after all.

[BOAC]

http://img.photobucket.com/albums/v293/boacphotos/TheOozlumbird.jpg

[CONF iture]

At Schipol the 737 autotrimmed into stall and trim was never touched in recovery (nor was thrust properly applied, but had it been the result might have been worse due to trim - see e.g. Turkish airliner crashes at Schiphol ).
But at least the rule was clear and unambiguous : Under manual flying it is the pilot job to trim.
Under manual flying by Airbus it is different, sometimes I trim for you, sometimes I don't, and sometimes I even won't tell if I don't : Perpignan

Surely only if the stick is held back, which will be fatal anyway in stall ?
Once again, the stick was NOT held back for the period of time the THS rolled back.

IMO there is something very critical here :
Regarding the specificity of the flight law, for the THS to stop rolling back, even a push on the sidestick (G demand below 1) should have been greater or in this case lower that the measured G for the period and that measured G was already below 1.0
In other words, even a push on the sidestick, if it was not strong enough, could have seen the THS still moving further up.

RRR Gums and RF4 may have made comments in that direction earlier. Tell me if I have misunderstood you please.

The auto trim behaviour clearly has been investigated, based on what is in the report.

Far from it, very far.

Resources are finite, and I don't think the investigation necessarily has the remit to go further into things that may be interesting but not causative or relevant to the outcome of the accident.
The position of the THS is absolutely relevant to the outcome of that flight.
It is also part of the cause.

[gums]

@ Conf

Way I read it is that the 'bus is primarily a gee command, so pulling or pushing commands the gee. Not like the gee command we had in the Viper, which had an AoA limit input, but a one gee command corrected for pitch attitude. So at any attitude except zero, the gee command is less than one gee.

I shall admit that pitch rates and gains are in the mix, but not AoA unless in the primary control law. And this disturbs me.

No doubt that the THS trim logic "helped" to keep the nose up attitude of the jet all the way down. Even releasing the stick would have kept the THS full nose up, and the BEA report mentions this aspect of the flight control laws.

I highly respect all the "heavy" drivers here, and I have learned a lot from the last two years of dialogue. I agree with Bubs and JT, et al, that the Captain could not figure out how the jet got to its condition without going thru the whole sequence. Just ran outta time.

I would not expect the average "heavy" driver to figure out the problem in a few seconds. No offense to most of you, but realize that the two folks up front were born and bred in the 'bus, and "you can't stall this thing", right?

I shall still maintain my position that the 'bus control laws need a heavier emphasis upon AoA, much like the B777 laws I saw in Turbine's link. It is not hard for HAL to see the AoA inputs and use them to help with the flight director displays and the "protections", regardless of the impact pressure on the pitot tubes. There are too many sensors on the jet to use for graceful degredation, IMHO.

As in my last post, I see a super aero design in the 'bus, and it has no pitch co-efficient problem that results in the classic "deep stall". In short, the jet would have recovered given the proper control commands. But ya gotta realize what is happening, ya think?

Lastly, I doubt that the current 'bus drivers will ignore the AF447 incident's lessons. YOU CAN STALL THE THING if in a reversion control law. If AP disconnects then hold what ya got for a while until you figure out what is happening. Don't depend upon HAL to correct for any of your incorrect commands, but think like you are flying a Cub or Cessna. And the beat goes on.

[DozyWannabe]

Once again, the stick was NOT held back for the period of time the THS rolled back.

Er - the trend over time (which is the criterion for autotrim movement of the THS) shows that the stick was held at least half-back for the majority of time the THS moved to the full-deflection position, and it was the 35 seconds it was held fully-back which kept it there:

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

[CONF iture]

No doubt that the THS trim logic "helped" to keep the nose up attitude of the jet all the way down. Even releasing the stick would have kept the THS full nose up, and the BEA report mentions this aspect of the flight control laws.
I would go further than that :
Even releasing the stick would have brought the THS further nose up.

[DozyWannabe]

I would go further than that :
Even releasing the stick would have brought the THS further nose up.

It depends how long for, and what attitude the aircraft was at when the hypothetical stick release happens.

It went all the way back in this case because the elevators were no longer sufficient to maintain the requested attitude as the speed bled off. The THS had moved approximately 5 degrees nose-up at the apogee of the climb. From that point onwards, the stick is held halfway back by the PF for a further 15 seconds, released for about 4 seconds with a small "blip" forward and then slammed against the back stop for an eye-watering 34 seconds. In short, the THS went where it was told to go by the PF. If he'd released the stick prior to the apogee, it would likely have stayed at a max of 5 degrees NU.

Put another way, the pitch command ratio (NU:NEUTRAL:ND) over the 53 seconds following apogee/stall is approximately 49:3:1 in seconds - which is an overwhelming trend towards nose-up.

Now - an interesting sim test would be to try stick-neutral just prior to the apogee, at the apogee and after the apogee (at the point where the PF slams the sick against the back stop) and see what the autotrim system makes of it. I'd be very surprised if the BEA haven't done precisely that, but a second opinion is always useful.

[gums]

C'mon, Doze, the pilot does not "command" the THS. The THS moves to reduce stick inputs for the commanded gee. HAL does this, not the pilot unless in one of the myriad of control laws.

As I recounted in an earlier post, our primitive FBW system was a gee command like the 'bus until we hit the AoA bias/limit. You could "trim" for two gees and due to the awesome visibility look back to see what the hizontal stabs were doing. The suckers would tilt down to get the nose up, then settle out until reaching the AoA limit ( "protection", if you will). In short, we had a full-time THS that tried to get to our trimmed gee, not AoA. At the AoA limit the stabs would then move the other direction to keep the AoA under 27 degrees or so until they were fully deflected for nose down pitch. Result was trimmed gee or one gee and max AoA, and falling like a rock.

My feeling is that all 'bus drivers need to see what HAL is doing to "help" them from getting into problems. All the "help" can hurt you when flying where you are not used to.

[DozyWannabe]

C'mon, Doze, the pilot does not "command" the THS. The THS moves to reduce stick inputs for the commanded gee.

Normal and Alternate Law pitch commands are for *flight path*, not G.

(which is, I believe, the crux of CONF iture's idea behind the THS trying to maintain flightpath even if the PF let go - in all honesty the answer to that is outside my sphere of knowledge)

HAL does this, not the pilot unless in one of the myriad of control laws.

The computers can't do it unless the pilot tells them to.

(and in this case the pilot was still trying to command a climb for almost a minute after the aircraft had stalled and begun to descend - the computers were simply trying to comply because they weren't specified with this scenario in mind)

My feeling is that all 'bus drivers need to see what HAL is doing to "help" them from getting into problems. All the "help" can hurt you when flying where you are not used to.

You can see what autotrim is doing at any point by looking at the trim wheel. Of course, that's no good if the pilot hasn't been told where to look...

[Turbine D]

Hi Gums,

Here is an article by Boeing where they discuss high altitude handling and stability in general terms.

High-Altitude Handling (http://boeing.com/commercial/aeromagazine/aero_02/textonly/fo01txt.html)

It does describe the differences between the B-777 and the MD-11 in terms of longitudinal static stability and how it is achieved in both aircraft.

[henra]

Now - an interesting sim test would be to try stick-neutral just prior to the apogee, at the apogee and after the apogee (at the point where the PF slams the sick against the back stop) and see what the autotrim system makes of it. I'd be very surprised if the BEA haven't done precisely that, but a second opinion is always useful.

Given that Airbus is using C* based laws it would have tried to keep attitude. If the last commanded attitude was 10° NU, it would have tried to keep the nose there, if not corrected even into the stall.

This is confirmed in the report on page 187 (chapter 2.2.5.)



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.

and


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.


Simply levelling off and then letting the stick go should have helped until a speed of ~Mach 0,65 (Figure 65 in the report). After that even at level attitude the FCS would have started to trim into the stall once the propulsive limit had been exceeded. At that point sustained ND input would have been required.

[HazelNuts39]

Put another way, the pitch command ratio (NU:NEUTRAL:ND) over the 53 seconds following apogee/stall is approximately 49:3:1 in secondsPut still another way: If one removes the 'grass' or 'mayonnaise stirring' from the trace, the sidestick was at an almost constant 21% nose-up position between 02:10:50 and 02:11:30, i.e. the time the THS was moving.

[jcjeant]

Simply levelling off and then letting the stick go should have helped until a speed of ~Mach 0,65 (Figure 65 in the report). After that even at level attitude the FCS would have started to trim into the stall once the propulsive limit had been exceeded. At that point sustained ND input would have been required. Two stupidities were combined to put in water AF447
That of the pilot ( pull the stick as a mad with a continued stall warning )
That of the Airbus system (hold the trim in up position when knowing this was a continuous stall)
If Airbus was in full manual both stupidities to put the plane into the water should have been made ​​by the pilot
Pull the stick and put together manually the trim full up position
So I conclude that the auto trim really helped to put AF447 in the water because the system worked as per design

[DozyWannabe]

Simply levelling off and then letting the stick go should have helped until a speed of ~Mach 0,65 (Figure 65 in the report). After that even at level attitude the FCS would have started to trim into the stall once the propulsive limit had been exceeded.

I'd like to see an experiment proving that before we make a definitive call - at this juncture we're into systems behaviour as yet untested, and unless we have someone from Airbus to confirm or refute that theory, your guess is as good as mine.

At that point sustained ND input would have been required.

Which is, after all, the correct response to recover from the onset of stall and has been since aircraft were made out of wood, doped fabric and twine.

That of the Airbus system (hold the trim in up position when knowing this was a continuous stall)

Ah, but the flight control computers are not programmed with the concept of stall and to the best of my knowledge never have been.

The stall warning parameters are encoded into the annunciator system, but the flight control computers are oblivious to stall in Alternate Law - and most would say rightly so, because for the computers to be able to override the human when in a degraded state would open the aircraft's safety to significant risk if the computers get it wrong (not to mention the fact that the backlash from the Airbus-sceptic brigade would be deafening if this were the case!).

The point is that outside of Normal Law, the systems are designed to defer to the pilot's inputs - no matter what those inputs are - for better or worse. This is based on the reasonable assumption that the human pilot will have a much better ability to adapt to circumstance than the computer ever could. In this case the crew were clearly overwhelmed and not only made mistakes, but repeated the same mistakes over and over again with tragic consequences.

[RetiredF4]

DozyWannabe
It went all the way back in this case because the elevators were no longer sufficient to maintain the requested attitude as the speed bled off. The THS had moved approximately 5 degrees nose-up at the apogee of the climb. From that point onwards, the stick is held halfway back by the PF for a further 15 seconds, released for about 4 seconds with a small "blip" forward and then slammed against the back stop for an eye-watering 34 seconds. In short, the THS went where it was told to go by the PF. If he'd released the stick prior to the apogee, it would likely have stayed at a max of 5 degrees NU.

You still have not fully understood the autotrim, THS, NzLaw without protections. Unfortunately BEA has not added normal acceleration in the graphs of the final report, therefore we have to deal with the bad graphs from Interim report 3.

From 02:10:25 until 02:10:50 the normal acceleration was below 1g. When PF after the stall warning 2 selected TOGA, the normal acceleration increased for a short time of about 10 seconds above 1 g. From that point on the normal acceleration was uninterrupted below 1 g until 02:12:00. When PF applied SS full NU at 02:11:40, the THS had already reached near full NU limit and the elevators moved now full NU. Despite those NU commands and despite the position of the THS the normal acceleration stayed below 1 g for another 20 seconds, until 02:12:00.

During all those times, where the aircraft was not able to maintain even 1 g, (and that started already before the apogee of the climb) the trim and the elevators would have moved on their own to achieve this 1 g with hands off SS neutral= 1g.

To stop the trim from further traveling, the SS would have to be moved and held at the present normal aceleration (which was below 1 g). To get the trim moving ND, the SS would have to be held to demand a g value well below the present normal aceleration.

Interesting, after PF started putting the SS to the NU stops and reduced the power at the same time to idle, the pitch of the aircraft decreased from +15° to -10° within 10 seconds. Power change and maybe the elevator deflection to full NU changed the forces of the airframe. What that did to the mental picture of the PF would be interesting to know. If PF would have gone to full ND at that point, the he might have had a chance to initiate recovery.

After the aircraft dropped outside the flightenvelope, which happened after the stall warning 2, any command except a definite ND command was bad, but the amount and the duration of the NU input or even a SS neutral input would not have saved the day and did not agrevate the NU travel of the trim. and the elevators. Because those were already maxed out by trying to maintain 1g.

BEA FR 2.1.3.2 Exit from the flight envelope
Subsequently, the position of the sidestick, maintained in its nose-up or neutral position, continued to exacerbate the situation and made the recovery uncertain, even impossible.

BEA FR 2.1.3.5 End of the flight
At about 2 h 12, descending though FL 315, the aeroplane’s angle of attack was established around an average value of about 40 degrees. Only an extremely purposeful crew with a good comprehension of the situation could have carried out a manoeuvre that would have made it possible to perhaps recover control of the aeroplane. In fact, the crew had almost completely lost control of the situation.
Up until the end of the flight, no valid angle of attack value was less than 35°.

[RetiredF4]

Henra
Given that Airbus is using C* based laws it would have tried to keep attitude. If the last commanded attitude was 10° NU, it would have tried to keep the nose there, if not corrected even into the stall.
NO, you are wrong there. It does maintain attitude, when autothrust is available. Without autothrust, when speed is decreasing, the aircraft trims to maintain the flightpath which is roughly 1 g. To maintan level flight when speed decreases, the attitude has to change, pitch has to increase, leading to a further decrease in speed and finally to stall. In your example the 10° pitch would have to increase.

You would be correct however, when low speed stability protection is available, which was not in AF447 case in Alt2b law.

This is confirmed in the report on page 187 (chapter 2.2.5.)

Quote:

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.
and

Read it again please. BEA speaks from maintaining altitude. They talk about a level flight there. To maintain the altitude, 1 g flight is mandatory, the attitude has to change to maintain this 1 g for level flight.

Come on guys, we have been through this for years.

[DozyWannabe]

@franzl

I'm not disagreeing with your hypothesis in the slightest, I'm just saying we're so far outside of normal operational parameters that I'd like to see supporting experiments to attempt to prove it.

I suspect that the PF could have rescued the situation with full nose-down held as late as 02:12:20, but I can't prove it.

[henra]

NO, you are wrong there. It does maintain attitude, when autothrust is available. Without autothrust, when speed is decreasing, the aircraft trims to maintain the flightpath which is roughly 1 g.

What you describe would be a pure C law. My understanding is that Airbus uses a C* law. A C* law will progressively switch from g command to pitch rate command when the speed decreases, i.e. at the stall it will be mainly pitch rate. That means if no SS inputs are made it will keep pitch rate 0 which means constant attitude.
If SS is left neutral it should keep constant attitude throughout. That is also what BEA considers neutrally speed stable.

Could you point me to any source that states that Airbus instead is using a pure C law?

Edit: Altitude is not a parameter in any FCS law. So FCS alone will probably not chase altitude. It may chase g or pitch or pitch rate or speed. That is what distinguishes C from C* and C*U (B777).
Altitude is only an A/P parameter.

[RetiredF4]

I suspect that the PF could have rescued the situation with full nose-down held as late as 02:12:20, but I can't prove it.

You might be the best engineer or pilot, you will never be able to prove it. When BEA would have been able to prove it they would have done it. And they had more tools available than you or we will ever get our hands on.

[RetiredF4]

What you describe would be a pure C law. My understanding is that Airbus uses a C* law. A C* law will progressively switch from g command to pitch rate command when the speed decreases, i.e. at the stall it will be mainly pitch rate. That means if no SS inputs are made it will keep pitch rate 0 which means constant attitude.
If SS is left neutral it should keep constant attitude throughout. That is also what BEA considers neutrally speed stable.

Could you point me to any source that states that Airbus instead is using a pure C law and that BEA (and myself) are wrong?

We had this before.

As i understand it it only references the value to change, in low speed the reference will be pitch change, in other cases g command. But stick neutral it will be 1 g.

During all those threads i copied following sentence, source now unknown:

G command’ which is a desirable capability at high speeds, means that for a particular amount of control column force, you get (available energy permitting) the same ‘g’ regardless of prevailing airspeed. Similarly, in a pitch-rate command system, you get the same amount of pitch rate for a given control column force regardless of prevailing airspeed.

[jcjeant]

Ah, but the flight control computers are not programmed with the concept of stall and to the best of my knowledge never have been.

The stall warning parameters are encoded into the annunciator system, but the flight control computers are oblivious to stall in Alternate Law - and most would say rightly so, because for the computers to be able to override the human when in a degraded state would open the aircraft's safety to significant risk if the computers get it wrong (not to mention the fact that the backlash from the Airbus-sceptic brigade would be deafening if this were the case!).

The point is that outside of Normal Law, the systems are designed to defer to the pilot's inputs - no matter what those inputs are - for better or worse. This is based on the reasonable assumption that the human pilot will have a much better ability to adapt to circumstance than the computer ever could. In this case the crew were clearly overwhelmed and not only made mistakes, but repeated the same mistakes over and over again with tragic consequences. I thought of everything and so I had to raise troops for mount a counter attack :)
In normal law (autopilot engaged or not) the automatic trim is a must and a great help in flying the aircraft (thank's also to the protections)
In alternate law .. things are not all the same
With the autopilot off (the pilot fly manually) .. alternate law says there is no more pitch protection ..
But still .. auto trim remains active
piloting in manual (pitch matter) is using the stick and the trim (the pilot is using both hands)
Not with Airbus ...
The pilot does not control the trim .. and this one continues to act as in normal law .. but then it is no longer active protection ....
To me this is a bad design .. the pilot don't control (full manual control) entirely the pitch ...
In alternate law the auto trim is not a help ... instead it's like throw a lead buoy at somebody drowning

[DozyWannabe]

@franzl:

I know for a fact I'm neither, nor am I likely to be!

Incidentally, the "Normal Acceleration" parameter is very much present in Annex 3 of the BEA's final report - on pages 1-6.

[gums]

I beg your pardon, Doze, but this is what my copy of the FCOM states:

http://www.sluf.org/misc_pages/a330_flight_mode.jpg

The attitude correction for the gee command ( load factor) provides an apparent "attitude" command, but it just ain't exactly the way HAL is working to "help" you. Additionally, this implementation also provides apparent "neutral speed stability". The basic aero of the jet still has positive speed stability, and positive longitudinal static stability, but HAL is trying to "help" you.

Only place I can find anything other than a gee command is in Direct Law.

show me how I am not getting my view of the control law from the text above from the FCOM.

As you, Doze, have pointed out many times, the primitive FBW system I flew back in the stone age would not be recommended for a commercial airliner EXCEPT FOR THE AoA LIMIT/PROTECTION!!! We also had a heavy AoA bias with the gear down to make the thing seem more like a "normal" jet.

Our gee command/AoA curve was designed for sustained turn rate at moderate gees - figure 5 or 6 gees. Think 25 degrees per second sustained rate with no loss of energy. And at 9 gees we got more than that for about two seconds until the AoA function kicked in - eat your heart out, heh heh.

For one more time, I iterate that I flew a no-kidding electric jet that did not have inherent static stability below 0.95 mach, yet had the apparent neutral speed stability that the 'bus has ( except when gear was down). We did not have the attitude gee correction for obvious reasons. We had no "direct law" except the manual pitch override deal when AoA was above 30 degrees and we were in a no-kidding deep stall, and that only gave us direct control of the horizontal tail. The 'bus has a lot more going for it and its pilots than the Viper, but ya gotta understand how the thing works and have some basic piloting skills.

[RetiredF4]

Retired F4;

I agree with everything you have written in your last post, but don't grasp the point you're making.

Its the exchange with DW and his continued saying, that the THS was driven by the NU SS input of the crew. And that is not correct, imho it had no effect at all, because only a continued SS ND input would have prevented the THS from moving NU.

The exit of the flightpath was the failure of the crew, a following prolonged and prominent ND input could have corrected this failure in the early flight envelope extension.



I would agree even with your last quote from the Human Factors part of the BEA report, if you remove the words "an extremely purposeful".

It´s not in the section of the HF group, and i dont have the authority to change the wording of BEA. It would be nice toi know, what caused this marvalleous sentence.

[DozyWannabe]

piloting in manual (pitch matter) is using the stick and the trim (the pilot is using both hands)

In more traditional designs this is the de facto state of affairs, but this design is different.

Not with Airbus ...
The pilot does not control the trim .. and this one continues to act as in normal law .. but then it is no longer active protection ....

The pilot controls the trim via the sidestick, just as in Normal Law - presence or lack of protections dont' come into it.

To me this is a bad design .. the pilot don't control (full manual control) entirely the pitch ...

An opinion to which you are welcome, but looking at it from an engineering point of view, does it not make more sense to have the aircraft behave as close as it can to how it behaves when not in a degraded state?

In alternate law the auto trim is not a help ... instead it's like throw a lead buoy at somebody drowning

Not at all - it behaves as it does in Normal Law, which makes sense - the loss of hard protections is a moot point. You can't blame the design for the fact that at least one member of the crew consistently applied inappropriate inputs.

[henra]

G command’ which is a desirable capability at high speeds, means that for a particular amount of control column force, you get (available energy permitting) the same ‘g’ regardless of prevailing airspeed. Similarly, in a pitch-rate command system, you get the same amount of pitch rate for a given control column force regardless of prevailing airspeed.


That is the description of a G command law vs a pitchrate law.
It does not describe the switching from one to the other which is happening with a C*.
When switching to the other prevailing command law it will do so also for stick neutral, i.e. it will keep pitch rate constant if SS is neutral.
Otherwise it would still be a G command law. However I'm not aware that the laws switch depending on SS deflection.
My understanding is the following:
At higher speeds (lets say above 230kts) it will keep 1 g at stick neutral and when deflecting the g load will always be the same for a certain stick position, independent of the speeds (so at 280 kts the same deflection will yield the same g as at 230kts).
Below a certain threshold (which was still quite a bit above stall speed IIRC) the law blends over to a pitch rate law. I.e. at SS neutral pitch rate is 0, thus pitch constant.
A certain deflection will always yield the same rate of pitch change once this law is the dominant one.

[gums]

Thanks, Retired, I think we are on the same page.

OTOH, I still believe the crew could have saved the day even after entering the stall. May have taken 15,000 feet, but a constant nose down command and manual trim should have done it.

The crew did not understand what was happening, and besides, "you can't stall the Airbus" mentality could have been at play.

I pray that many 'bus drivers are reading our excellent recap of the accident and all the ideas we have expressed to prevent a future repeat.

[RetiredF4]

DozyWannabe
Incidentally, the "Normal Acceleration" parameter is very much present in Annex 3 of the BEA's final report - on pages 1-6.

You are correct, but they are the same as in IR3. I should have said that i was looking for high resolution pictures.

The normal acceleration in the following graph would be helpful.

http://www.bea.aero/fr/enquetes/vol.af.447/imageshr/figure.28.jpg

[HazelNuts39]

Its the exchange with DW and his continued saying, that the THS was driven by the NU SS input of the crew. And that is not correct, imho it had no effect at all, because only a continued SS ND input would have prevented the THS from moving NU. I think it is both: The THS movement was driven by the continued NU SS input, and (after the stall) only a continued SS ND input would have stopped or reversed it.

[DozyWannabe]

Cheers HazelNuts39,

All - the point I'm trying to get across is that we're in the realms of theory here, and there are too many variables about which we are unsure to be able to make a definitive assertion one way or the other. For example, we know the speeds came back at about 02:10:35 (shortly into the zoom climb) - did this affect the C*/pitch angle transition at any point?

My personal assumption is that the THS may have continued to trim NU to maintain the commanded FPA or pitch angle, but I think it was the continued attpemts to pull up during this process that caused it to happen so quickly.

[RetiredF4]

@ henra

See gums post, according to that it maintains 1 g with hands off, which would not be the case if it would maintain pitch.

G command--Pitch-axis control law by which the pilot gets the same "g" for a particular amount of stick force, regardless of speed (energy permitting)

Pitch-rate command--Pitch-axis control law in which the pilot gets the same pitch rate for a particular amount of stick force (or deflection in some designs), regardless of speed.

henra
My understanding is the following:
At higher speeds (lets say above 230kts. it will keep 1 g at stick neutral and when deflecting the g load will always be the same for a certain stick position, independent of the speeds (so at 280 kts the same deflection will yield the same g as at 230kts).
Below a certain threshold (which was still quite a bit above stall speed IIRC) the law blends over to a pitch rate law. I.e. at SS neutral pitch rate is 0, thus pitch constant.

If you would be right, BEA has it wrong:

BEA FR
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.

This aircraft would under your definition of the NZ law maintain pitch attitude, but go into an descent to compensate for the loss of speed. It would be partial speed stable. It would not stall from level flight and it would not try to maintain altitude.

From FCTM Cathay Pacific:
Flight Mode
In pitch, when an input is made on the sidestick, the flight control computers
interpret this input as a “g” demand/pitch rate. Consequently, elevator deflection is not directly related to sidestick input. The aircraft responds to a sidestick order with a pitch rate at low speed and a flight path rate or “g” at high speed. When no input is made on the sidestick, the computers maintain a 1g flight path.

[BOAC]

Putting to one side the ineptitude of this crew, what worries me is that after 1100+posts (and several years) we still cannot really establish what does what and when in an Airbus control system. It kind of takes away the chances of 'Mr Average' getting a 'feel' for it, doesn't it?

Many years ago, I think after the very early Indian AB crash, someone told me that 23 different control modes were effective in pitch between cruise and touchdown - all 'un-announced', of course.

[DozyWannabe]

@BOAC

We're talking about how the system is likely to behave in extremis based on the information we have - to be certain we'd need to have an Airbus insider to spell it out.

But in the same breath, a pilot didn't have to understand the inner workings of the artificial feel system in older aircraft to be able to fly the things. As you've pointed out, all this technical back-and-forth is rendered somewhat moot by the fact that the initiating event was sustained and repeated control inputs which were thoroughly inappropriate for the conditions.

As to your other point, the fact that there are only 6 control laws in the A320 causes me to question your source.

[jcjeant]

An opinion to which you are welcome, but looking at it from an engineering point of view, does it not make more sense to have the aircraft behave as close as it can to how it behaves when not in a degraded state?
So I ask the question:
Who is piloting a Airbus A330 .. the pilots or those who engineered the system ?

[DozyWannabe]

@jcj:

OK, so let's look at it this way. As a pilot, do you want your aircraft to behave as it does more than 99.9(rec)% of the time if something goes wrong, or to throw you into a control regime with which you've had little hands-on experience since converting to the type on top of the failure that caused it?

[Lonewolf_50]

Dozy, BOAC said "modes" and you responded with LAWS.
I'd read more carefully.

I refer you to the table (matrix) of A330 flight laws that was quite popular, though it is vintage 2005, as discussions on this mishap began.

I'd invite you to look at that chart again.

There is an interaction between behaviors a laws and which protection does or doesn't turn on or off or is modified, see the notes.
These modes include all that ... with varied PROTECTIONS

PITCH ATTITUDE
LOAD FACTOR
AOA
HIGH SPEED
LOW ENERGY
LOW SPEED STABILITY
HIGH SPEED STABILITY
ANGLE OF BANK
MAN’UVER LOAD ALLEVIAT-ION
TURBUL-ENCE DAMPING
YAW DAMPING
TURN COORD
NORMAL LAW
ALTERNATE LAW 1
ALTERNATE LAW 2 (with subtle degrees ...)
DIRECT LAW
MECH BACKUP

If BOAC had meant "laws" I suspect that's what he'd have said.

The picture he was trying to paint was of the complexity of what a pilot faced in knowing what he can expect his plane to do, or to be able to do.

That's how I read it anyway.

[DozyWannabe]

As I understood it, the crash in India was a case of FMC-based mode confusion similar to that which caused the Air Inter crash in the Vosges - flight control laws and modes never really came into it in terms of the priamry factors behind the accident.

[PuraVidaTransport]

Looking at the graph Dozy posted, noticed something I guess never computed before and apologize if it's been discussed to death and it just didn't make an impression. From 2:12.32 until about 2:12.49, pilot sitting in the right hand seat had predominately nose down inputs, with the first input going to the stop in the nose down direction. For this entire 17 seconds the elevators only moved to 15 degrees nose up from the bottom line of 30 degrees. The THS never moved.

Way too late, when the pilot in the left hand seat was finally given control, he input nose down almost to the stops from 2:13.45 to 2:13.52 so a total of perhaps 7 seconds until the dual inputs from the other guy evened out the inputs to around neutral. So full nose down for 7 seconds only moved the elevator to 15 degrees nose up and again, the THS never moved.

Just how long would a nose down input have to last to finally get the THS to full nose down? Took about a minute to roll to full nose up after predominately nose up side stick inputs from 2:10.47 to 2:11.45. Seems like an awful long time to have to wait in an emergency situation.

So can someone explain why it takes so long to get control surfaces to give the actions requested by the pilot. As I see it, the pilot wanted the nose down for 17 seconds and got nothing more than 15 degree nose up then the other wanted FULL nose down for 7 seconds and the computers once again only gave him nose up elevator. Does this have something to do with the cumulative inputs? Can a set of bad inputs cause the airplane to not respond quickly as was needed in this case??

[jcjeant]

OK, so let's look at it this way. As a pilot, do you want your aircraft to behave as it does more than 99.9(rec)% of the time if something goes wrong
No .. that I would not want that ..
The 99.9% is the behavior of the aircraft in flight which is operated by automatic systems , FBW and autopilot
The aircraft behave automatically .. that's is not of any help as experience when I must put my hand on the stick for fly it in another law than normal
When I have a problem (meaning that the flight management system is not more reliable at 100%) .. I'd rather manage myself (and with crew) and not have a hybrid system .. that can execute commands (eg trim auto) in my place
Hence the words many time hear when something go wrong:
It's my aircraft

PuraVidaTransportSo can someone explain why it takes so long to get control surfaces to give the actions requested by the pilot. As I see it, the pilot wanted the nose down for 17 seconds and got nothing more than 15 degree nose up then the other wanted FULL nose down for 7 seconds and the computers once again only gave him nose up elevator. Does this have something to do with the cumulative inputs? Can a set of bad inputs cause the airplane to not respond quickly as was needed in this case??Go in direct law (full manual) .. and problem solved even with no elevators ( if you are enough quick to move manualy the trim :) )

[CONF iture]

PuraVidaTransport,
In both cases the ND inputs were not strong enough and sustained in the time to allow the elevators to go from 30 deg UP to a DOWN position.
For the second case, the ND input by the PNF was weakened by the NU input made by the PF.

[CONF iture]

the sidestick was at an almost constant 21% nose-up position between 02:10:50 and 02:11:30, i.e. the time the THS was moving.
So 1/5 only of the full stick deflection, pretty far from "the stick was held at least half-back for the majority of time the THS moved to the full-deflection position" stated earlier by DozyWannabe.

I think it is both: The THS movement was driven by the continued NU SS input, and (after the stall) only a continued SS ND input would have stopped or reversed it.
The THS movement only really started with Stall Warning 2.

[CONF iture]

If Direct Law rules after AP disconnect, the worst case scenario is the PF is still full back stick when the CPT is back, but the THS is still at 3 degrees, so the stall is not that developed and the stall warning keeps warning ...

Captain, what do you think now ?
I think we're in a stall. Sure I could guess better if I could see you are pulling like mad on your controls ...

[mm43]

Just to keep the Oozlum Bird from disappearing "you know where", the following extract(s) from the Airbus A330 Instructor Support Manual provide the following:-Characteristics in pitchWhen acting on the stick the pilot commands a constant G load maneuver and the aircraft response is G Load / Pitch rate. The pilot order is therefore consistent with the aircraft response "naturally" expected by the pilot, Pitch rate at low speed / Flight Path rate or G at high speed.

Hence STICK FREE, the A/C maintains the flight path even in case of speed changes. Furthermore, STICK FREE in case of Configuration changes, or thrust variations, etc… the pitching moment effects are reduced by the feedbacks in the control law itself and compensated for by precommands. With STICK FREE in turbulence, small deviations do occur on the flight path but with a tendancy of the A/C to regain a steady condition.
As a consequence the A/C is a STABLE PLATFORM and AUTOTRIMMED; it needs to be flown with minor corrections from the pilot on the stick, when the A/C deviates from its intended flight path.

Don’t fight with the stick; if you feel you overcontrol, release the stick.

Indications
The degradation of control laws is indicated on ECAM as well as on PFD.
- On ECAM
in ALTN: ECAM EW/D FLT CTL ALTN LAW (PROT LOST)
MAX SPEED 305/.82As an aside, the PNF must have said, "Alternate law, protections lost."

[BOAC]

As I understood it, the crash in India was a case of FMC-based mode confusion- while your contributions are important, DW, please read posts carefully. I made no comment on the cause of the accident.

[RetiredF4]

PuraVidaTransport
So can someone explain why it takes so long to get control surfaces to give the actions requested by the pilot. As I see it, the pilot wanted the nose down for 17 seconds and got nothing more than 15 degree nose up then the other wanted FULL nose down for 7 seconds and the computers once again only gave him nose up elevator. Does this have something to do with the cumulative inputs? Can a set of bad inputs cause the airplane to not respond quickly as was needed in this case??

That question was asked before, and i hoped the final report would answer this quetion. Bottom line is, that you have to ask the automation logic, because the SS only orders a change of g. How much change was ordered with full ND SS? I dont know, there are tables with g values corresponding to respective SS deflection, but i dont know wether there are speed gains involved or wether the load factor protection could have played a role in this.
Load factor protection was the only protection left, and again, i dont know wether it has some speed dependent gains as well.

Maybe an overlay of the graph you mentioned with actual normal acceleration values would shed some light.

[HazelNuts39]

The THS movement only really started with Stall Warning 2. Right, and that came within a second after the PF started to pull.

[henra]

This aircraft would under your definition of the NZ law maintain pitch attitude, but go into an descent to compensate for the loss of speed. It would be partial speed stable. It would not stall from level flight and it would not try to maintain altitude.


Hmmm, I don't see the disagreement with BEA in my post. If you put the aircraft in an attitude where the thrust is not sufficent to sustain the speed it will progressively continue into a stall. That is what BEA basically says.

Edit: Maybe just to clarify: When I say attitude I refer to pitch and not to AoA.

edit2: I assume the notion of Flight Path in BEA's description might be a traslation thing. Per my understanding the FCS does not care about Flight Path in the proper sense. That's the FMS which does that. FCS cares about behaviour relative to the air, not navigational.

Let's assume you place the nose 10° above the horizon. My understanding is it will try to keep the nose pointed at 10° no matter what the AoA. Given the fact that thrust will not be sufficient at that altitude to maintain speed in that attitude and given the progressively increasing drag with decreasing speed it will go into the stall and will resist any natural tendency to drop the nose with elevator and once its authority limit is reached it will call the trim for help.

Could you point my to where my assumption differs from BEA's?

[HazelNuts39]

Let's assume you place the nose 10° above the horizon. My understanding is it will try to keep the nose pointed at 10° no matter what the AoA. The lift, and hence normal acceleration, is a function of AoA. If normal acceleration differs from 1g, pitch will change towards 1g with stick neutral.

[Lonewolf_50]

HN, franzl, henra:

As this discussion of C* and its nuances progresses. I begin to get the impression, that attitude flying isn't an allowable mode in the A330, unless you transition to Direct Law. Or, in the case of pitch control, force the issue by use of Trim Wheels.

That does not make sense to me, and means that I misunderstand something essential. Also, based on the comments of those who fly Airbus aircraft, I infer that you can fly the A330 like any other aircraft.

As noted a few posts up, when PNF made a significant nose down input, and it was reduced in scope by PF coming back onto the controls, we have a non trivial CRM issue: two pilots fighting over the controls.
I have the controls
You have the controls

Not sure if PNF (LHS pilot) would have saved the day had his inputs not been interfered with, but I don't care what kind of aircraft you are flying in: If there are two pilots, and two sets of controls, and there are two people making inputs in opposition to one another, the odds of it all ending in tears goes up by orders of magnitude. :(

[Lyman]

Quote:
A homogenous law, ensuring aircraft behaviour independent of the flight conditions and, in particular, independent of the centre of gravity location, is achieved by tabulating the gains as a function of the computed airspeed, high-lift configuration and centre of gravity location.


When the THS started to trim NU along with the pilot's NU command, can it be said that for whatever reason, they were both trimming into STALL?

Pilot error, and, what..... Program error? Blame aside, they both had their reason, both faulty.

[roulishollandais]

As I understood it, the crash in India was a case of FMC-based mode confusion similar to that which caused the Air Inter crash in the Vosges

In the crash of Air Inter in the Vosges (near the Mont Sainte Odile on the mountain BLOSS) there has never been a FMC-based mode confusion. The family of victims would have wanted it would be said to get more money... from AIRBUS of course. I showed the prosecutor the two approach charts problems (Bloss altitude decreased to 2500 FT, and "FAF" missing) with copy to BZ !

You see I am independant from the A/B fight !

[DozyWannabe]

@roulishollandais:

The approach chart problems probably negated a legal avenue for compensation, but the fact is that the incorrect mode *was* set, and Airbus/Honeywell changed the FPA/VS display on the FCU panel accordingly.

Of course, that wasn't the first time that particular problem had arisen (although it was the first fatal accident) - the first time it reared it's head almost resulted in an A320 on approach to Gatwick landing on Crawley High Street!

The point I was trying to make was that there is a very important distinction that must be made between automation (i.e. autopilot/autothrust/FMS/FMC) and FBW - and that extends to modes. In the case of the Indian Airways accident, the mode problems were related to autoflight (incorrect FMC settings for approach resulting in autothrust going into Open Descent rather than the managed approach path) and not the flight control computers/FBW aspect, which is under consideration in this accident.

Believe it or not, I have no dog in the A. vs. B. hunt either - I just don't like opinion masquerading as fact, and I especially don't like lazy assertions that have no basis in fact (examples of which include "The [Habsheim] A320 thought it was landing", "The FBW Airbus design process excluded pilots", "FBW is the first step towards pilotless airliners" and "Boeing's latest models do not rely on computers for control") being repeated in the public domain.

[rudderrudderrat]

Hi DozyWannabe,
I especially don't like lazy assertions that have no basis in fact (examples of which include ..... Boeing's latest models do not rely on computers for control
It depends on how you define rely. They can be flown in "Direct" without any PFC computers. Airbus only allows Direct Law when the gear is down.

"What should be noted, however, is that none of these features limit the action of the pilot. The 777 design utilizes envelope protection in all of its functionality rather than envelope limiting . Envelope protection deters pilot inputs from exceeding certain predefined limits but does not prohibit it. Envelope limiting prevents the pilot from commanding the airplane beyond set limits. For example, the 777 bank angle protection feature will significantly increase the wheel force a pilot encounters when attempting to roll the airplane past a predefined bank angle. This acts as a prompt to the pilot that the airplane is approaching the bank angle limit. However, if deemed necessary, the pilot may override this protection by exerting a greater force on the wheel than is being exerted by the backdrive actuator. The intent is to inform the pilot that the command being given would put the airplane outside of its normal operating envelope, but the ability to do so is not precluded. This concept is central to the design philosophy of the 777 Primary Flight Control System."

"Direct
—In the ‘‘Direct” mode, the ACEs do not process commands from the PFCs. Instead, each ACE decodes pilot commands directly from the pilot controller transducers and uses them for the closed loop servo control of the actuators. This mode will automatically be entered due to total failure of all three PFCs, failures internal to the ACEs, loss of the flight controls ARINC 629 data busses, or some combination of these failures. It may also be selected manually via the PFC disconnect switch on the overhead panel in the flight deck. The airplane handling characteristics in the “Direct” mode closely match those of the ‘‘Secondary” mode."

http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_11.pdf

[DozyWannabe]

Interesting stuff rudderrudderrat!

My knowledge of the B777 is very patchy, so that's one for the memory banks. Having said that, I should have made clear that I was referring to a specific conversation I was involved in (many moons ago!) where one of the guys asserted that Boeing never implemented FBW at all, and that the 777 used higher-tech versions of the electromechanical connections in the 75 and 76.

It appears that Boeing opted for defence-in-depth at the electro-mechanical level, whereas Airbus opted to do it at the software level (2 separate and distinct "clean room" implementations per computer etc.). In layman's terms, Boeing opted to have a mode that bypasses the computers entirely in the case of a triple failure, whereas Airbus opted to make it harder for the computers to fail in the same way. Both completely valid ways of solving the problem - and it's a testament to both builders that neither scenario has been put to the test.

[CONF iture]

Airbus, with reason, put in place some restriction to not autotrim all the way when everything works fine, but decided autotrimming all the way was the way to go when data acquisition was known as deficient …

I don't see what's graceful in such degradation ?

I question Airbus on such 'logic' ?

But more than anything, I do question the BEA on their apparent lack of curiosity ?

[RR_NDB]

I don't see what's graceful in such degradation ? (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-59.html#post7351516)

It seems to me this important System design principle was not properly used.

I question Airbus on such 'logic' ?

Logic?

But more than anything, I do question the BEA on their apparent lack of curiosity ?

My boss always told me: Not just bureaucrats. Low level bureaucrats.


Who cares?

It seems, just the pilots.

The UAS incidents before F-GZCP were registered. 50+ OR MUCH MORE

[RR_NDB]

...whereas Airbus opted to make it harder for the computers to fail in the same way. Both completely valid ways of solving the problem... (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-59.html#post7351516)

Question:

Graceful degradation is the same in both?

FM (frquency modulation) has the so called "threshold effect". Up to a certain level, everything is fine (excellent Signal to noise ratio).

Below a certain level worms, dominate the scene. So aviation uses AM.

Doppler effect also was a factor in the selection

[DozyWannabe]

Airbus, with reason, put in place some restriction to not autotrim all the way when everything works fine, but decided autotrimming all the way was the way to go when data acquisition was known as deficient …

Incorrect. Autotrim is never inhibited or restricted directly (on the A330 at least), it is subject to the protection limits in the same way that autoflight or human pilot input is in Normal Law. Take away those protection limits (i.e. in any law below Normal) and any of the aircraft's controls (including trim) has full authority.

I don't see what's graceful in such degradation ?

I question Airbus on such 'logic' ?

That's because it's what you want to see. You're so invested in the idea of Airbus's logic being wrong and that their intent was to restrict pilots that you can't see the wood for the trees - in this case the design is intended to give full authority to the pilot in every axis precisely because "data acquisition was known as deficient".

If the pilot mishandles the aircraft outside Normal Law then the chances are good that something's going to go amiss, but that's true of every aircraft flying, not just Airbus.

I repeat - autotrim only worked against this crew because their control inputs were inappropriate, and if they'd realised their situation and applied corrective inputs then autotrim would have helped them get stable - until quite late in the sequence.

Now - I can see either putting an extra alert or (in extremis) limiting the autotrim angle being a possible option, but as studi pointed out:

There is a term for this in flight safety: black swan event. They are so random and so unpredictable, that if you start to adapt technology to the specific event, a totally different unexpected thing will happen and fail your adapted technology.

this comes with a risk - especially when such a change is in response to a single incident that was way outside the bounds of acceptable aircraft handling.

But more than anything, I do question the BEA on their apparent lack of curiosity ?

And again - just because it does not mention a specific item in the report in the way you want it to (because trim response to SS input is covered in the sequence in some detail) does not mean that the investigators didn't look into it.

Question:

Graceful degradation is the same in both?

They can't be, because the control philosophy is different. Airbus used advances (in 1982 terms) in technology to rework the concept of an airliner cockpit from the ground up. Boeing used the fact that their technological starting point was later (about 1988-89) to create a more complex system that restores a more traditional feel through artificial means.

FM (frquency modulation) has the so called "threshold effect". Up to a certain level, everything is fine (excellent Signal to noise ratio).

Below a certain level worms, dominate the scene. So aviation uses AM.

I'm a little lost by this - if we're talking code complexity here, the Airbus logic is actually incredibly simple (in software terms), even by the standards of the time.

[TTex600]

I just don't like opinion masquerading as fact, and I especially don't like lazy assertions that have no basis in fact


Do you mean statements like this? One of the biggies for me is conflating FBW (which is the technology used in the flight control systems of the A320 through A380, as well as the B777 and B787) with FMC/FMS (which has been a standard component of every major airliner for the last 3 decades or more). The latter of which is essentially a fancy term for advanced autopilot and is the exclusive domain of the "what's it doing now?" problem.

FMC/FMS is not a fancy term for an advanced A/P, and they are not the exclusive domain for the "what's it doing now" problem.

BTW, why will my MCDU not accept the speed I program in it for a apeed/altitude crossing restriction? Sometimes it does, sometimes it doesn't. Why not? For example, a fix (jingl for example) must be crossed at 280 kts/17000ft but the FMC will not accept 280kts. I enter 280/17000, but it only gives me 275/17000.

Why will the 320 fly 260kts when the FCU is selected to 250kts in managed speed? (it's not a weight issue)

NOTE
Edit: the last sentence should reference selected speed not managed. That's what I get for posting after a red eye trip.

[LandIT]

Lonewolf
I don't care what kind of aircraft you are flying in: If there are two pilots, and two sets of controls, and there are two people making inputs in opposition to one another, the odds of it all ending in tears goes up by orders of magnitude.


I agree forcibly. The only thing I can expand on this is if the two pilots have different ideas (which I think we see in AF447), the odds go up even more!

[CONF iture]

And again - just because it does not mention a specific item in the report in the way you want it to (because trim response to SS input is covered in the sequence in some detail) does not mean that the investigators didn't look into it.
That specific item is a flight control in a stall scenario.
It deserves a paragraph in Aircraft information 1.6 ... where is it ?
It requires also a full analysis of its operation during the event ... where is it ?

Incorrect. Autotrim is never inhibited or restricted directly (on the A330 at least), it is subject to the protection limits in the same way that autoflight or human pilot input is in Normal Law. Take away those protection limits (i.e. in any law below Normal) and any of the aircraft's controls (including trim) has full authority.
... that's what I say, you too need a good presentation on the THS operation ... Ask the BEA.

[DozyWannabe]

FMC/FMS is not a fancy term for an advanced A/P, and they are not the exclusive domain for the "what's it doing now" problem.

FMS/FMC is the automation component regardless of FBW - "advanced A/P" (when compared to, say, the old Sperry and Smiths units) is as good an analogy as any.

I'm perfectly happy to be corrected by the way - can you name an incident where "what's it doing now"? was related to the FBW and not the automation?

BTW, why will my MCDU not accept the speed I program in it for a apeed/altitude crossing restriction? Sometimes it does, sometimes it doesn't. Why not? For example, a fix (jingl for example) must be crossed at 280 kts/17000ft but the FMC will not accept 280kts. I enter 280/17000, but it only gives me 275/17000.

I can't help you there I'm afraid - however there are many on here who can (I'd suggest A33z or rudderrudderrat).

Why will the 320 fly 260kts when the FCU is selected to 250kts in managed speed? (it's not a weight issue)

My guess would be an external factor in the managed flightpath - does it maintain 250 in selected mode?

[TTex600]

FMS/FMC is the automation component regardless of FBW - "advanced A/P" (when compared to, say, the old Sperry and Smiths units) is as good an analogy as any.

You're incorrect and I've already given the reason. An FMC/FMS is not an advanced autopilot.

I'm perfectly happy to be corrected by the way - can you name an incident where "what's it doing now"? was related to the FBW and not the automation?

I refuse to argue from your position. If you want to discuss in context, 'll be glad to do so. Actually, I'll help you - again. The context was this: pilots do not always know exactly what an airplane is doing. Go back and read post 649 from the "AF447 Report Out" thread Rumours and News. Here, I'll make it easy for you Who conflated anything? I told an old joke in the context of an Airbus pilot who might not know exactly what his machine was doing at all times. A3-TWENTY said this. "Note:I fly the airplane for almost 10 years and like it , but I assume it has imperfections.". jcjceant answered with this, "I hope you will not have to suffer the imperfections that you assume exist on the Airbus .. for to assume means not knowing exactly who they are and therefore you risk finding yourself in a situation that you will not understand ..".
I followed with an old joke to illustrate that pilots do not always know what the airplane is doing. Nothing in that joke denigrates Airbus. If anything, it's pilots laughing at each other.

We could probably get along well if you could find it in yourself to answer what I write instead of trying to use my words tomorrow further your jihad against what you judge to be misinformation.

Regarding the questions I asked. I know the answers......because.......... I actually operate the airplane.

[wozzo]

Regarding the questions I asked. I know the answers......because.......... I actually operate the airplane.
So you know the answers, but you won't tell us, because Doze was mean to you?

[DozyWannabe]

You're incorrect and I've already given the reason. An FMC/FMS is not an advanced autopilot.

You've yet to tell me *why* though - it'd be very helpful!

If you want to discuss in context, 'll be glad to do so. Actually, I'll help you - again. The context was this: pilots do not always know exactly what an airplane is doing. Go back and read post 649 from the "AF447 Report Out" thread Rumours and News. Here, I'll make it easy for you

Thanks - OK.

So, my position - which happens to be fact - is that FBW is not automation. Never has been. FBW relates purely to the link between the control inputs (whether they be manual or automatic) being digital in nature and being passed through a computer, rather than through electro-mechanical or pure mechanical means - to the flight surface actuators.

To my knowledge, the "what's it doing now?" incidents (i.e where "pilots do not always know exactly what an airplane is doing") are FMC/FMS rather than FBW-related. If you disconnect the FMC/FMS and fly an A320 manually, the computer will do everything you ask of it - up until the point where alpha max is reached or the G loading exceeds the level where structural damage is likely.

The only instance of a grey area that I can think of was the Habsheim crash, where it was not so much a case of "what's it doing now?" as "why won't it give me more nose-up?". The answer to that question was "because if it did, you'd have stalled - and you disabled autothrust so alpha-floor can't help you".

So - as to your earlier point:

BTW, why will my MCDU not accept the speed I program in it for a apeed/altitude crossing restriction? Sometimes it does, sometimes it doesn't. Why not? For example, a fix (jingl for example) must be crossed at 280 kts/17000ft but the FMC will not accept 280kts. I enter 280/17000, but it only gives me 275/17000.

Why will the 320 fly 260kts when the FCU is selected to 250kts in managed speed? (it's not a weight issue)

These are questions relating purely to automation - FBW doesn't come into it.

We could probably get along well if you could find it in yourself to answer what I write instead of trying to use my words tomorrow further your jihad against what you judge to be misinformation.

Believe me I'm trying my best - it does none of us any good to be combative!

I'm just trying to set a baseline for discussion based on what I know and that is that FBW and FMC are completely separate and distinct systems.

Regarding the questions I asked. I know the answers......because.......... I actually operate the airplane.

I'd be really happy to know - do tell! :)

So you know the answers, but you won't tell us, because Doze was mean to you?

Mean? I've never been anything less than honest, enthusiastic and hungry for information! If I've come across as mean at any point, please accept my humble apologies... :O

That specific item is a flight control in a stall scenario.

As I said before, the flight control computers have no concept of "stall". They "know" about alpha max, however. In Alternate Law the computers allow a pilot to exceed alpha max (as well as the load limits) if sufficient control force is applied.

Come on - you're well-read on Habsheim. When the Captain tried to pull past alpha-max the computers didn't simply disregard the pitch command, they held the aircraft just shy of alpha-max, including ND elevator commands where necessary. The reason for this is that the hard protections aren't part of the system which controls the surfaces, they are a separate system that monitors the aircraft's position relative to those limits and will maintain those limits until such a time as the command in the opposite direction is given.

Think of it as a bounding cuboid around the aircraft, constantly changing in dimension based on the aircraft's pitch, bank, AoA and speed data. In Normal Law, there isn't a bit of logic that says "Don't move THS/elevator/aileron beyond this position" - the logic says "if these limits are reached or exceeded, use all the flight controls to remain stable at this limit". A drop from Normal Law to Alternate 1 replaces the "do not exceed" logic with "return to this limit when controls are released". A drop to Alternate 2 and beyond removes it entirely.

[CONF iture]

You're incorrect and I've already given the reason. An FMC/FMS is not an advanced autopilot.
DW has been answered on that point (http://www.pprune.org/6760675-post280.html) already after he made similar comments (http://www.pprune.org/tech-log/466259-af447-final-crew-conversation-thread-no-1-a-14.html#post6760643) ...

[DozyWannabe]

Gah - semantics! FMC/FMS relates to automated flightpath management whether A/P is engaged or not.

It's an advanced FD/autopilot combination - is that any better?

In any case, the point is that it's a separate and distinct system to FBW, which relates solely to digital interpretation of flight control input.

[TTex600]

Thanks CONF iture.

And I apologize to everyone. After reading tens of thousands of posts, I guess you all already know the foibles of the main characters. And I don't intend to become known as just a pedantic jackass. You men obviously don't need me to point out others issues, sorry and I'll try to avoid getting pissy in the future.

[CONF iture]

As I said before, the flight control computers have no concept of "stall". They "know" about alpha max, however. In Alternate Law the computers allow a pilot to exceed alpha max (as well as the load limits) if sufficient control force is applied.

And your point is ... ?
Does it disqualify the THS as a flight control surface ?
What is the THS operation under Normal, ALT1, ..........................., ALT2B Law ?



Please, Habsheim for another thread ... when time permits.

[DozyWannabe]

CONF - read what I'm saying carefully. The limiting protections are not assigned to each of the flight controls in turn, the flight control computers simply command a flight path, and when an axis limit is reached, maintain the flight path in said axis. The THS (and for that matter elevators, ailerons etc) are not prescribed movement limits in real-time (which would be inefficient and unnecessarily complex), they are set to follow the commanded flightpath, whatever that may be.

When the protections are inhibited in Alternate Law 2, the pitch axis is still controlled by the commanded flightpath, but the flightpath no longer has a hard or soft limit. As such the THS and elevator will follow any command given from the stick, which makes sense as long as you're willing to trust the pilot.

So - on that basis, the systems designer faces a dilemma. Do they add an autotrim limit or warning based on the current status of the aircraft? Would doing so run the risk of making things worse? Is it worth taking that risk on the basis of a single incident where the control inputs made by the PIC were woefully inappropriate?

At the risk of repeating myself, the autotrim would have assisted in the recovery if the PIC had ordered sustained and consistent nose-down. It would have stopped dead and slowly recalibrated itself if he'd levelled off at any point prior to the apogee and stall.

Even if autotrim was limited or disabled in Alternate, the end result of AF447 would have been the same because the fact we cannot escape from is that the PIC pulled up at the onset of UAS, continued pulling up during the climb, and kept pulling all the way thorough stall and descent to the ocean.

PS. I wasn't bringing up Habsheim to talk about Habsheim, I was simply drawing your attention to the behaviour of the flight surfaces in that incident to illustrate my point. I did so because I know you're very familiar with it.

[jcjeant]

So - on that basis, the systems designer faces a dilemma. Do they add an autotrim limit or warning based on the current status of the aircraft? Would doing so run the risk of making things worse? Is it worth taking that risk on the basis of a single incident where the control inputs made by the PIC were woefully inappropriate?
This can be interpreted from another point of view ...
If this amendment would have existed before the accident .. the accident would perhaps not have the same end
Exactly as for pitot .. if they had been replaced by .. lots had the accident less likely to occur

[DozyWannabe]

This can be interpreted from another point of view ...
If this amendment would have existed before the accident .. the accident would perhaps not have the same end

How can you say that with a straight face? He pulled up almost all the way down!

Let's be clear here - the THS position didn't help matters once stall had been established, but correcting that was a simple matter of pushing the stick forward and holding it there for about 8 seconds. The elevators would have overcome the THS force even before that. They had approximately 70 seconds from apogee until the stall became effectively unrecoverable.

This is like getting hung up on the rivets on the Titanic - OK, so they may not have been the best possible composition, but what made the ship sink was hitting a ^&*$ing iceberg. Even the best rivets might have only bought them a little more evacuation time at best. This aircraft crashed because the crew handled the aircraft inappropriately and stalled it.

[HazelNuts39]

Exactly as for pitot .. if they had been replaced by .. lots had the accident less likely to occur You really should read the report. The replacement pitots have fallen in disgrace since. It is not certain, not even probable, that they would have made any difference in the particular conditions encountered by AF447.

[jcjeant]

You really should read the report. The replacement pitots have fallen in disgrace since. It is not certain, not even probable, that they would have made any difference in the particular conditions encountered by AF447.
I try to understand the meaning of your message ...
This would mean that the replacement of pitot is a sham (or smokescreen) and that the risk is exactly the same as before AF447 ... and yet the planes continue to fly happily because a procedure is available in case of pitot problems

It's just like if you buy a car that has the latest technical refinements
But the salesman informs you that from time to time (often when it rains) the brakes (pitots) are no longer available (short-term phenomenon)
It does not matter because you will see a warning on the dashboard telling you that the brake assist is no longer available
In addition the manufacturer shall have available a brochure (procedure) explaining how to do in case of brake failure
Do not leave the road
Avoid obstacles
Try to stop with other methods
Furthermore the seller'll reassure you because he saw that you are a good driver for your drivers license has more than 20 years .. so no problems
Will you buy this car and take your family to a certain death ?

[DozyWannabe]

And... Just in case people missed it earlier, the Thales pitot tubes were an optional fit. The standard was 3x Goodrich.

The Thales AA type are the only model known to have suffered a triple failure. The Thales AB type have suffered single and double failures, but not triple. The Goodrich probes have suffered single failure only.

There is no such thing as a perfect pitot tube design for weather conditions of that type.

[CONF iture]

The THS (and for that matter elevators, ailerons etc) are not prescribed movement limits in real-time (which would be inefficient and unnecessarily complex), they are set to follow the commanded flightpath, whatever that may be.
You are misinformed Dozy.
Reaching alpha prot, the THS just stops moving.
Anything above alpha prot is done on the elevators only.
It is not 'inefficient and unnecessarily complex' it is commun sense.

[HazelNuts39]

jcjeant,

At the time of the accident, AF was in the process of replacing Thales C16195AA probes by Thales C16195BA probes. The current standard is Goodrich Type 0851HL.

PS. For more details, see interim report #2, 1.18.7 and final report 1.18.1.7.

[DozyWannabe]

You are misinformed Dozy.
Reaching alpha prot, the THS just stops moving.
Anything above alpha prot is done on the elevators only.
It is not 'inefficient and unnecessarily complex' it is commun sense.

No - it does not stop moving because it is commanded to stop, but because at that point there is nothing else to correct for. This is something on which I'm pretty damn certain because (admittedly many years ago) I saw the logic paths.

[HazelNuts39]

Dozy,

FCOM 1.27.20 Flight Controls, Normal Law, Flight Mode:
When angle of attack protection is active, THS is limited between setting at entry in protection and 2° nose down (i.e. further nose up trim cannot be applied).

[DozyWannabe]

@HN39 - which is not the same as being directly commanded to stop, no? Movement is limited because of the useful positional range at the protection limits.

All I know is that I was taught it was a side-effect of the protection logic rather than a direct command.

[CONF iture]

No - it does not stop moving because it is commanded to stop, but because at that point there is nothing else to correct for. This is something on which I'm pretty damn certain because (admittedly many years ago) I saw the logic paths.
That is what is terrible with you Dozy, you have a biaised concept of the laws, modes, protections ... but you keep explaining each and everyone how it works.

It shows especially when you start talking about Habsheim ... but as long you're 'pretty damn certain' ...

[DozyWannabe]

No CONF, I have a conception of the logic at engineering level. If you want to think of it as a physical analogy, picture a metal sheet in a G-clamp. The Normal Law protections are the G-clamp and prevent the flight surfaces from exceeding a certain position. The closer to the airframe limits the aircraft gets, the tighter the G-clamp is wound, but the protections do not directly order the flight surfaces not to exceed a given position.

Take the G-clamp away and there is no restriction.

[HazelNuts39]

which is not the same as being directly commanded to stop, no?No, it is not, but who said it was, and does it matter?

[DozyWannabe]

No, it is not, but who said it was, and does it matter?

It matters if someone tries to claim that there was a direct limit on autotrim movement in Normal Law that was taken away when degrading to Alternate...

To inhibit a direct control surface limit implies that something that could have still functioned despite the degradation was nevertheless taken away, whereas inhibiting an entire external system that relied on data that was no longer reliable is a perfectly reasonable design decision.

[HazelNuts39]

Dozy,

For practical purposes, the difference escapes me. Perhaps you should say that the PRIM's, having rejected the three ADR's, cannot define alpha-prot?

[jcjeant]

jcjeant,

At the time of the accident, AF was in the process of replacing Thales C16195AA probes by Thales C16195BA probes. The current standard is Goodrich Type 0851HL.

PS. For more details, see interim report #2, 1.18.7 and final report 1.18.1.7. You don't answered my question :)
Will you buy this car and take your family to a certain death ?

[DozyWannabe]

Dozy,

For practical purposes, the difference escapes me. Perhaps you should say that the PRIM's, having rejected the three ADR's, cannot define alpha-prot?

That's one technical explanation (aside from replacing "alpha-prot" with "alpha max"). But the issue from an engineering standpoint is that the flight surface limits are not defined within the system that controls them, but imposed by a second system from outside (hence the G-clamp analogy). In Alt 2 that second system as a whole is considered failed and therefore inhibited.

This design decision was made based on the hypothesis that the pilot should have full authority across every flight control surface if the reliability of data was doubtful, and ironically this is a position that every Airbus sceptic would normally agree with.

What makes this situation doubly ironic for me is that if Airbus had slapped a limit on autotrim in alternate law and that limit had prevented a recovery in another incident, the same people who are currently lambasting the autotrim design for unquestioningly following the PICs inputs would be lambasting Airbus for preventing a recovery by limiting autotrim authority.

[jcjeant]

What makes this situation doubly ironic for me is that if Airbus had slapped a limit on autotrim in alternate law and that limit had prevented a recovery in another incident, the same people who are currently lambasting the autotrim design for unquestioningly following the PICs inputs would be lambasting Airbus for preventing a recovery by limiting autotrim authority. The simple solution for avoid this double ironic situation is to put the trim in manual when out of normal law when trouble (false or no data at all)
This design decision was made based on the hypothesis that the pilot should have full authority across every flight control surface if the reliability of data was doubtfulPilot full manual authority on ALL moving surfaces ... :ok:
My aircraft

[DozyWannabe]

The simple solution for avoid this double ironic situation is to put the trim in manual when out of normal law

Not so simple if the pilot isn't used to it, as studi points out.

Manual control does not necessarily mean manual trim, no matter if you or others wish it was so.

[jcjeant]

Not so simple if the pilot isn't used to it, as studi points out.If a pilot can't use (or had forget how to use) ALL moving surfaces of a plane ... this is not the good job for him ... IMHO
Manual control does not necessarily mean manual trimFull authority .. yes ..
My aircraft

[DozyWannabe]

If a pilot can't use (or had forget how to use) ALL moving surfaces of a plane ... this is not the good job for him ... IMHO
Full authority .. yes ..

The pilot can command autotrim from the sidestick. Easy as pie.

[Lyman]

Do oh oh Z...

"The pilot can command autotrim from the sidestick. Easy as pie..


If he can command it, it is not AUTO..... He is flying a powered elevator, and if he snuffs Autotrim, he'll get fired....

Auto/Manual, there is a difference....

[DozyWannabe]

If he can command it, it is not AUTO..... He is flying a powered elevator, and if he snuffs Autotrim, he'll get fired....

Auto/Manual, there is a difference....

Firstly - proof of what you're saying please.

Secondly - autotrim is separate and distinct from flightpath automation and always has been.

Finally - autotrim is separate and distinct from FMS/FMC automation and is slaved to pitch commands made by the PIC. Autotrim is an automatic system slaved to the pitch commands given to the aircraft whether those commands come from the FMC/FD/Autopilot or the guy sitting in the command seat. Autotrim cannot be "snuffed" or disabled through crew action.

[OK465]

This is like 'good cop', 'bad cop'.

[DozyWannabe]

Try "thoroughly fed-up cop".

;)

[Lyman]

Toody and Muldoon? Friday and Smith? Cramden and Norton? Butch and Sundance?

Dopey and Sneezy?

yeah...wait, the Ministry of Silly Walks?

[DozyWannabe]

I was thinking Bayliss and Pembleton.

[Lyman]

Baywatch and Pendleton?

No se, amigo....

[DozyWannabe]

Bayliss and Pembleton (or Pellegrini and Edgerton):

Three Men & Adena 5 - YouTube

If you don't understand, likely you never will.

[TTex600]

Even if autotrim was limited or disabled in Alternate, the end result of AF447 would have been the same .......

Why do you assume so much?

How can you say the end result would be the same?

Until you know why he continued to pull, you just can't make that assumption.

It is very possible that the pilots would have recognized the stalled condition had the stab remained at cruise setting. In that case, every time he released back pressure, the nose would have dropped, and it might have sunk into his conscience that his pull was in fact the problem. But I'll admit that the preceding is just my opinion. You might try the same tactic.

[CONF iture]

No CONF, I have a conception of the logic at engineering level. If you want to think of it as a physical analogy, picture a metal sheet in a G-clamp. The Normal Law protections are the G-clamp and prevent the flight surfaces from exceeding a certain position. The closer to the airframe limits the aircraft gets, the tighter the G-clamp is wound, but the protections do not directly order the flight surfaces not to exceed a given position.

Take the G-clamp away and there is no restriction.
You are fascinating in your style Dozy, you are told how you're wrong but still manage to explain me how it works in the very next post. Your place is in Politics, whatever the winds stay on your feet and talk, just talk.

G-CLAMP ... I like a dozen of them or is it just an ident ?

Excuse my sarcasm really, but that guy has no limit.

[jcjeant]

The pilot can command autotrim from the sidestickThat's exact .. he command not the trim but trigger the autotrim system (that's not a manual command on the trim)
If for some reason .. the command to elevator is blocked (or the elevator is mechanically blocked) the pilot have no more control on autotrim
In manual the pilot can command the elevator and the trim (they are no more linked by a system)
So he have full authority on the two separate moving surfaces
He can even don't use the elevator for control the pitch ....
So ... really it's my aircraft

[HazelNuts39]

I wonder if the preoccupation of some posters with the THS can be traced to a misperception of its rôle. When releasing the stick in a small airplane, the elevator is released and the airplane goes to the AoA for which it is trimmed.

That is different in a FBW airplane. Releasing the stick does not release the elevator. The elevator goes to the position that will provide 1g. As long as the elevator doesn't reach full travel, the position of the THS is irrelevant for the flight path. The main difference is that the elevator moves quickly and the THS moves slowly. 1° of THS is equivalent to 1.5° of elevator (according to Owain G).

[syseng68k]

Not so simple if the pilot isn't used to it, as studi points out.
Well isn't that what training is supposed to do ?.


Manual control does not necessarily mean manual trim, no matter if you or others wish it was so.
Yes, (sigh) we know it isn't at present, but that wasn't the context. The
context was the suggestion that it might be a good idea. Comments on
what was actually said might be usefull. Like, for example, whether you
think it might be a good idea and if not, why ?...

[NeoFit]

The pilot's only job is to feed the dog and keep him awake; the dog is supposed to make sure that the pilot doesn't touch anything.


Hello gentlemen,

Sunday is coming, and I need some smiles.

It has been recently discussed here (AFAR) what the airplane's computers were doing.
Sometimes, Buses pilots are asking: "what 'she' is going to do"
(I don't need to open here a polemic about male or female computers).

So I propose you, for those who would not have made it yet, to acquaint with this (http://www.headupflight.net/articles2/Pilot%20or%20Computer%20in%20Command.htm).

If you agree, I'll speak another day about 'The bumblebee does not know how to fly ...but ....'

[syseng68k]

If you don't understand, likely you never will.

Do you really have to be so superior and dismissive of others, or
is it just a temporary aberation ?. You're letting the side down
with comments like that and are starting to look like a troll, which
a usenet forum would have a particularly harsh way of dealing
with..

It's not a competition here :-)...

[Linktrained]

NeoFit
Thank you for publishing Prof.Dr.Ronald Schmid on Computer in Command.

I would add that an aeroplane is the only mode of transport that is unable to stop whilst in its operating medium ( the air).

The Titanic, could have, should have, stopped. A car cannot be driven in practice on ordinary roads at speeds of only between 30 to 35 mph constantly, without having to stop, somewhere.

[roulishollandais]

@ Dozy W.
Air Inter Ste-Odile:
If Airbus and Honeywell have changed the display FPA / VS on the FCU panel this results from their free choice, not a Court decision.:=
Instead the prosecutor, in his submissions on appeal, has completely rejected all attempts by experts and all parties to the trial for fifteen years who sought to challenge both the display, the autopilot modes, or that the control laws (not mentioned).
If the charges to be reviewed has not been decided by the Court is that the defendants were not for those wrong approach cards, and not for compensation ground.

Posts of the thread AF447 PPRuNe are not journalists or gossip grand public, but the result of discussions and information done by professionals.

[TTex600]

Try "thoroughly fed-up cop".

Then why continue to escalate the tension, especially by butting into a sub discussion that didn't include you in the first place? For that matter it's a free forum, you're obviously free to butt in anytime you want, but you could at least butt in as a third party instead of assuming the argument was originally made to include you.

[Turbine D]

Originally posted by TTex600: Then why continue to escalate the tension, especially by butting into a sub discussion that didn't include you in the first place? For that matter it's a free forum, you're obviously free to butt in anytime you want, but you could at least butt in as a third party instead of assuming the argument was originally made to include you.
Now you must admit this wasn't a very tech oriented posting, was it? Dozy has been a very valuable resource in understanding the electronics of the Airbus aircraft for many of us during the AF447 saga. Your criticism tends to be a cheap shot.
Since you have recently emerged as the bright bulb on the string when it comes to technical understandings (questions when you know the answers), lets get back to technical stuff, eh? A question for you: There are 6 cues, you were taught, so as to recognize UAS. What are they, can you name them without looking them up? We are all interested in your response.
These cues, by the way, being missed by this crew, lead to non-application of the UAS procedure.

[andycba]

HN39:

"I wonder if the preoccupation of some posters with the THS can be traced to a misperception of its rôle. When releasing the stick in a small airplane, the elevator is released and the airplane goes to the AoA for which it is trimmed.

That is different in a FBW airplane. Releasing the stick does not release the elevator. The elevator goes to the position that will provide 1g. As long as the elevator doesn't reach full travel, the position of the THS is irrelevant for the flight path. The main difference is that the elevator moves quickly and the THS moves slowly. 1° of THS is equivalent to 1.5° of elevator (according to Owain G)."

Forgive my ignorance, but could you explain something further? - I've long been following this story as someone with a history in software development, human machine interface design, appropriate use of technology as well as safety critical engineering in computing and telecommunications. This area is also rife with mode confusion, troubles with automation and manual configuration, as well as difficult diagnosis of problems and recovery/reversion - just look at Natwest as a recent example.

I'm confused by how you are referring to a FBW airplane here in general - FBW is a mechanism to move control surfaces without direct mechanical linkages, at least for the primary control mechanism.

The implementation of FBW could have direct control surface deflection based on control input movements - e.g Airbus direct law

On the other hand, there are a myriad of control laws that can be put in place on a FBW aeroplane that can alter/filter the control inputs to produce a control surface movement to match what the designers want to achieve - be it protections, stability etc.

As I understand it, Airbus, Boeing, Sukhoi etc have their own implementations of FBW, not all the same and not all demanding 1G responses? Do all FBW default to a 1G design philosophy? And as I could understand it, airbus and boeing differ in their control law philosophy, with one being flight path stable and the other being speed stable?

So this lumping together of all FBW aircraft as following the 1G philosophy has me confused. Could you elaborate a bit further if possible on this at all for an outsider?

[HazelNuts39]

andycba;

My post was about the A330, the airplane under discussion in this thread. Sorry if I did not make that explicit.

[thermostat]

Seems to me that some folks don't understand the "auto trim" concept.
The elevator and stab must be faired (in a straight line) in order to remove the load (forces) on the control column/stick.
If the stick/wheel is moved back, the elevator moves up and is no longer faired with the stab. The pilot has to trim nose up (leading edge of the stab moves down) so as to align to two surfaces and remove unwanted pressure.
Instead of the pilot having to manually move the trim wheel, auto trim simply does it for him/her. Holding back pressure on the wheel/stick will cause the auto trim to move (trim) the stab until the two surfaces are aligned (faired).
That's what happened in the case of 447, The auto trim did exactly as it was supposed to. It trimmed the stab to fair with the up elevator. It's a beautiful system that reduces the workload on the pilot. If they wanted to recover from the stall condition, all they had to do is push forward a bit on the SS moving the elevator down and the auto trim would have dutifully trimmed nose down to the required angle. End of stall. Please stop blaming the auto trim for doing it's job.

[TTex600]

TurbineD, my post was as tech oriented as was Dozy's quoted post. And sometimes, someone has to stand up to the bully.

I have no idea what six clues you think I was taught. Unlike Dozy, I'm not professing to be the expert. But I do know a little and some of it happens to show that Dozy isn't the expert on all things flying.

Edit: you accuse me of a cheap shot, then drop right down to trying your own shot. I posed flying questions to Dozy because he continues to insinuate superior operational knowledge. I asked him specific Airbus quirks, not to show my knowledge but to help him realize that he might not know everything.

I've asked many times for people to think about why the crew was confused, maybe they didnt know youre six steps. You've not answered my questions about their confusion with your six steps. Go ahead and post them, some of us might learn something.

Edit #2: TTex doubles down.

Dozy assumes the role of an exasperated superior and again insults those who would dare disagree with him
Try "thoroughly fed-up cop".
Where do I find your post chastising Dozy for his attitude of superiority? Why not take umbrage with his self elevated position as a board policeman?


I'll stand by the post you find offensive. And I'll ask again, If Dozy is thoroughly fed up, why does he continue to escalate the tension?

[TTex600]

It's a beautiful system that reduces the workload on the pilot

How many accidents/incidents have been blamed on pilot fatigue caused by working too hard on trim? Or, how many accidents were blamed on pilots incorrect trim?

IOW, was the auto trim necessitated by a need to reduce pilot workload?

[Machinbird]

I think I understand what TTex is pointing at.
There was only a small trim change in THS position leading up to the stall, but if that trim change had not occurred, the aircraft would have sought to fly at its original trimmed speed and PF would have had to work mighty hard to slow it down to a stall. Dozy does not really appreciate the significance of this because his piloting experience is minimal.

Yes the Airbus THS trim worked exactly as it was designed to. So What? In retrospect, that might have not been the best design from a human factors standpoint.
Yes, any self-respecting Airbus pilot who could fly the thing in ALT2 law at altitude would appreciate the flight path stability offered by the current implementation of Alt2 which involves similar behavior to Normal Law in pitch and Direct Law in roll.

However a pilot who badly overcontrols an Airbus in roll and doesn't know how to stop it will have serious trouble controlling other axes at the same time. With such a loss of precise pitch control ability, the flight path stability of the Airbus becomes a liability, because it tends to mathematically integrate inadvertent pitch inputs.

Such a pilot would benefit from a direct drop to manual THS trim following loss of speeds. This essentially means Direct Law in pitch also, since Alternate law in pitch without autotrim does not make sense.

Perhaps the law of lowest common denominators (i.e. weakest pilot skills) should apply as the difficulty of flying increases. From all accounts Alt2 at altitude is not particularly difficult if one is smooth, but can be a real bear if one is using the stick to wipe the cockpit.

I'm going to offer the opinion that if AF447 dropped to Direct Law on loss of speeds, even with the crew she had on that night, the odds of arrival at the other end would have dramatically improved. Then the raw airframe's natural speed stability would have helped them avoid the low speed trap that they fell into. At least, they would not have crashed in the same manner.:suspect:

[rudderrudderrat]

Hi studi,
They would not have had to wrestle forcefully the yoke forward, while needing one hand to control a misbehaving autothrust system.

All they needed to do was to disengage the autothrust and advance the thrust.
How can 3 crew members watch the speed decay to Vref -20?
Why did no one press the TOGA switches?
Alternate Law would not have saved that crew either.

"The first officer responded immediately to the stick shaker by pushing the control column forward and also pushing the throttle levers forward. The captain however, also responded to the stick shaker commencing by taking over control. Assumingly the result of this was that the first officer’s selection of thrust was interrupted. The result of this was that the autothrottle, which was not yet switched off, immediately pulled the throttle levers back again to the position where the engines were not providing any significant thrust. Once the captain had taken over control, the autothrottle was disconnected, but no thrust was selected at that point. Nine seconds after the commencement of the first approach to stall warning, the throttle levers were pushed fully forward, but at that point the aircraft had already stalled and the height remaining, of about 350 feet, was insufficient for a recovery."

ASN Aircraft accident Boeing 737-8F2 TC-JGE Amsterdam-Schiphol International Airport (AMS) (http://aviation-safety.net/database/record.php?id=20090225-0)

[mike-wsm]

Bearing in mind that the THS position had been in one steady setting during high altitude cruise, shouldn't the electronics have kept it like that and refused to move it so far so quickly without reason? Any permissible movement would be extremely slow and linked to fuel burn or movement.

[HazelNuts39]

There was only a small trim change in THS position leading up to the stall, but if that trim change had not occurred, the aircraft would have sought to fly at its original trimmed speed and PF would have had to work mighty hard to slow it down to a stall.I don't think that is a correct description of how the system functions. A sidestick input commands a change of flight path. The flight control system moves the control surface to satisfy that demand. If the THS had not moved, the FCS would have commanded more elevator to achieve the demanded response from the airplane, 1.5° for 1° of THS estimated by Owain Glyndwr. The elevator would have reached its maximum deflection of 30° 5 seconds earlier (see chart below). At that time the AoA was 33° and perhaps it would not have increased beyond that with the THS remaining at 3° and the sidestick held on the back stop.

I'm going to offer the opinion that if AF447 dropped to Direct Law on loss of speeds, even with the crew she had on that night, the odds of arrival at the other end would have dramatically improved.I doubt that also. It would not have made longitudinal control any easier, and the PF would probably have over-controlled. And what were his targets? Would they have been different in direct law?

http://i.imgur.com/eaEBt.gif

[rudderrudderrat]

@ Studi,
Alternate law plus fixed thrustlever detents would most probably have saved them. If you don't see that you have most probably never flown Airbus or you just deny to accept how it works.
Have you read OEB 38 "Erroneous Radio Altimeter Height Indication"?
"During an ILS (or MLS, GLS) approach with AP engaged, if an erroneous and very low RA height indication occurs, THR IDLE and FLARE modes may engage early with the following consequences:
In CONF FULL, the High Angle of Attack protection is not available. As a consequence the autopilot will not automatically disconnect at α prot +​1 °. If the flight crew does not immediately react, the angle-of-attack will increase and may reach the stall value."

If you think a computer controlled stab trim will save your life - then you are going to be bitterly disappointed.

[rudderrudderrat]

@ studi,
If you are lucky you are even in the Alternate law with low speed stability, so you do not even end up that low on speed.
Have you actually read OEB 38?
what it really means if you have to handle a situation.

Oh .... Please tell me what it really means.

[rudderrudderrat]

Ok, one more last time. Have you actually read OEB 38?
However, I am not aware of one single accident of an Airbus where the protection "took control away" where it better should have not.
Here are a few to start with then.
Accident of an Iberian Airbus A320 in Bilbao (http://www.iasa.com.au/folders/Safety_Issues/others/Bilbao.html)

"the French Civil Aviation Authorities (DGAC) had issued an airworthiness directive (AD) for the A319/320 aircraft. It ordered the crews to fly at least 10 kts. faster and use only “CONFIG 3” (flaps 3) setting on approach in conditions with gusts greater than 10kts reported wind increment (max. wind minus average wind), or when moderate or severe turbulence on short finals has to be expected......
In the light of the accident occurring only four months ago, and the sometimes lengthy ‘normal’ timeframe for implementation of safety revisions after an accident, it appears to be of “amazing speed” how Airbus Industrie, - even in the absence of a final report, has already decided and performed a modification on the alpha- protection control laws. This was done in an approach “to increase the flight crew’s authority”, - as Cpt. Brandt was quoted saying by media. - A step applauded even by staunch Airbus critics among the international pilot community. A revised software version is expected to be validated this month and has already received certification by the French Civil Aviation Authority (DGAC) and the European Joint Aviation Authority (JAA). Airbus plans to implement a “rapid retrofit program” for its entire A319/320 fleet."

[RetiredF4]

studi
By the way, there is normally no alternate law with gear down, it goes into direct law upon gear down and AP off, so treat Amsterdam as an EXAMPLE for possible benefits of autotrim.

Just to be correct, that applies only, if the aircraft was already in alternate law prior gear lowering, and has imho nothing to do with AP off. If not in alternate law prior gear down, it will land in the flare mode of alternate law. I think you know that, but others might read your post in a different way.

[NeoFit]

studi

And I give you the Bilbao incident. It is the only one.


And what about ORY 1994 Tarom serious incident ?
(so sorry, but it's my own hamster wheel ;-))

[Lyman]

Wie gehts studi...

I think I have not referred once to Boeing. I discuss THS and Autotrim because of its importance in this accident, whilst you seek to frame Bus as Victim of nasty Bus haters....

Autotrim is remarkable in 447 case for its anomalous behaviour in the tragic flight path that doomed this flight.

1. At 2:10:05, it was set to three degrees (-) NU. Throughout the climb and until STALL Warn 2, there it remained, until 2:10:48. You say, along with thermostat's elegant description of its function, that it seeks always to fair the elevators into its AoI, reducing stress on controls.

2. At 2:10:48, it started to move smoothly ( see graph IR #3), until it hit Maximum NU. IT REMAINED at MAX for the duration...

3. There has been a weak but continuous clamor that the THS' behaviour was due "insufficient deflection" by the pilot, and/or short duration of input via SS.

4. Which is it? Is it insufficient controls NU by the pilot? Or is it "Pilot pulls like madman" on SS, and the THS behaviour is unexplained?

5. Some explanations for this dormancy of the HS:

a. Overspeed protection, THS inhibited.

b. Load factor exceeded for Autotrim, (spike of +1.65G in climb)

c. Direct Law

d. A mystery, and none of my business....

Aufwiedersehn, Lyman

EDIT.... It is not incorrect to state that for purposes of discussion, one may say that there was no Autotrim whatsoever post autopilot loss, 2:10:05.

It was fixed for 43 seconds as this aircraft climbed to STALL....it then cycled smoothly to its functional limit, and remained there until impact, at 2:14:28.

I know you are a big fan of Autotrim, so....where was it?

I have belabored this anomalous failure as to the effect it must have had on the pilots. In phase 1, the CLIMB, the was no trimming. In PHASE 2, it was maxed full NU.

PF BONIN has to master the controls in two regimes, the climb, elevators only, and the fall, FULL NU THS plus elevators. In upset, and then LOC, he has TWO PITCH authorities to acclimate to.

No problem, any monkey can do that? Just as the a/c is about to Stall, the Slab
Actions to provide trim FULL NU. The a/c remains NU, dissipates some very valuable energy, and drops in free fall (still NU). You could do that in your dreams?

A casual observer could make the claim that the STALL was forestalled, then caused, by the THS.

[bubbers44]

Why all these laws? Are pilots flying these machines or robots? All my flying career it was so simple, push forward it goes down, pull up it goes up and pull up too much it goes down because you are totally stupid. Very simple law.

[Organfreak]

@Studi:

What had been under discussion was Airbus flight-control logic in this particular case, AF447, and the possibility of improvements to the software logic. (Admittedly very difficult to suss, given the lack of specific information about exactly what the pilots saw and responded to.) As you yourself admitted, there is always room for improvement in almost any system you could think of, and here, we were not talking about improving Boeing's flight-control logic.

Your comments have devolved this into a discussion of A vs. B, in general. Not helpful at all, though always fascinating and tempting to get into. Perhaps this should have been a new thread: "Ten thousand views on A vs. B." :bored: The very unfortunate accident at Schipol really has very little to do with what happened to AF447.

'Tis true that there was, very obviously, a training/knowledge problem on the flight deck (AF447), but that does not mean that there was no problem whatsoever with the A330's logic. I'm upset by arguments such as yours (and Dozy's) because they would remove any possibility of safety improvements, which have to be a good thing. "It's good enough, in fact, it is wonderful," you seem to say. Scary stuff. :ooh:

[DozyWannabe]

Do you really have to be so superior and dismissive of others, or is it just a temporary aberation ?

It was a throwaway comment made very late at night, after a long day, referring not to the subject at hand but to a (brilliant but not very well-known) police procedural TV show.

I was saying "If you don't know who Bayliss and Pembleton are, you probably wouldn't get the reference" - nothing more. It was supposed to be a comic aside to prevent things from getting too serious!

[Lyman]

studi...


Quote..."It is interesting what you say, but from a pilots point of view, it is irrelevant if a pitch demand on the side stick is executed by elevator or stabiliser, as long as it is executed. This was the case, the aircrafts pitch followed Bonins input."

That too, is interesting. The Stabiliser, in Full NU adds 13 degrees to the elevators deflection relative to the airstream. I submit that had a great deal to do with the extreme high AoA into and through the STALL. At deflection of 30 degrees, plus 40-60 AoA, the elevators are acting more like spoilers than elevators. At the highest, they are lift fences at ninety degrees to airflow. All drag, no lift.

At three degrees deflection, the elevators would be pumping hard, without the trim that a pilot would expect. Now trim is visible on the wheel, but that would possibly serve to confuse..... If pilot susses no trim, well. That is evidence of DIRECT LAW. What else could it be? A Trick? Not really, but false evidence, appearing "Real".

At the extremes of deflection, the AOA could be expected to drop rapidly, and increase likewise, making for a bit of a wild ride.

[DozyWannabe]

studi

And what about ORY 1994 Tarom serious incident ?
(so sorry, but it's my own hamster wheel ;-))

As studi says, completely different type, completely different systems design. Notably the old A300/310 system had a very loud warning bell when the trim went too far out of position. Of course, those types were not FBW and as such were not designed to have a constantly-correcting automatic trim - a loud bell signifying trim movement would quickly become a nuisance with the FBW design.

That too, is interesting. The Stabiliser, in Full NU adds 13 degrees to the elevators deflection relative to the airstream. I submit that had a great deal to do with the extreme high AoA into and through the STALL. At deflection of 30 degrees, plus 40-60 AoA, the elevators are acting more like spoilers than elevators. At the highest, they are lift fences at ninety degrees to airflow. All drag, no lift.

With a traditional empennage design, and with all control systems functioning, it is never completely impossible to un-stall the aircraft due to aerodynamics. The limiting factor is purely time (i.e. how long you have before running out of altitude to recover), and if the PF had pushed the stick forward and held it there, the THS would have come forward and recovery would have been straightforward in a matter of a few seconds (presuming that the recovery was effected with enough altitude to spare).

By looking at the DFDR traces, it's evident that the aircraft did not stay nose-high all the way down. What happened was that the nose came down, the speed built up, but the elevator and THS position caused it to pitch back up again - just like a paper dart running out of speed.

The THS went to full-NU as quickly as it did because the PF was still pulling up as the aircraft ran out of the speed at apogee and continued pulling well into the stall. The aircraft only ever did what was demanded of it.

Remember that spoilers work as they do because of their relative closeness to the aircraft's centre of gravity. Spoilers wouldn't work on the tail because they'd cause the extreme pitch-up moment that was seen when the nose dropped in the AF447 sequence - due to being placed well aft of the aircraft's CoG.

@Organfreak - I don't know if you can see this, but I don't think I've ever even hinted that the Airbus systems design is perfect (hell, I'm a software guy and know full well there's no such thing!). All I've ever objected to is kneejerk assertions that such-and-such a change would make things better, when the people suggesting it don't fully understand the decisions behind that design - some of whom have never even tried to understand it and work from the basis that it's fundamentally wrong based on their own prejudice.

[bubbers44]

I think that is the reason I stuck with Boeing. Just fly it as pilots have flown for over 100 years. There are no laws, just airmanship. If you are very stupid you can stall so just don't be stupid. How hard is that?

[Lyman]

bubbers

Why is it do you suppose that Autotrim is kept when the Law has degraded? What advantage does it have over Direct Law, (manual reversion), such that the a/c remains at a specific Pitch incidence to work from?

This does not apply to 447, as I have pointed out, though the aircraft should have had Autotrim, it did not, and when it Stalled it did have it?

Curioser

[DozyWannabe]

@bubbers44 - There have been a lot of changes to how pilots control aircraft in the last 100 years, most if not all of which were necessary to progress. The very first one was going from wing-warping to aileron panels - admittedly that was more like 102 years ago now, but I suspect you were including the Wright Bros. in your timeframe. Another big one was going from taildraggers to tricycle gear, which required a significant change in methodology.

In general most of these changes were made (as were those underpinning the Airbus FBW design) to make life easier for the pilot.

Why is it do you suppose that Autotrim is kept when the Law has degraded? What advantage does it have over Direct Law, (manual reversion), such that the a/c remains at a specific Pitch incidence to work from?

As many have pointed out, it's because it's what the crew will have been used to on that type for over 99% of their time flying the thing.

[Lyman]

HazelNuts39

Howso? With elevators and THS deflected max NU, plus AoA, what value do you derive? Never mind, I must have had a touch of vertigo.......arse about, apologies.

Dozy:

Quote. "By looking at the DFDR traces, it's evident that the aircraft did not stay nose-high all the way down. What happened was that the nose came down, the speed built up, but the elevator and THS position caused it to pitch back up again - just like a paper dart running out of speed."

Yes, and why did the THS not trim ND?

And. Quote. "The THS went to full-NU as quickly as it did because the PF was still pulling up as the aircraft ran out of the speed at apogee and continued pulling well into the stall. The aircraft only ever did what was demanded of it."

That is just wrong. It spent 43 seconds 'parked' at three degrees NU. It did not trim NU as the climb began and continued. PF's commands were a combination of ND and NU, and some time was spent -1G. So it should have trimmed, what inhibited it?

And Quote: [B]"As many have pointed out, it's because it's what the crew will have been used to on that type for over 99% of their time flying the thing."

I was asking bubbers44 what he thought.

So why carry a 99 into the one percent? Manual should mean manual, not a 'blend'

[DozyWannabe]

Yes, and why did the THS not trim ND?

Because it was never commanded to - none of the inputs of the PF and PNF were ever sustained long enough to make a difference, with one exception. The PNF's input at 02:13:42 would probably have been enough to move the THS - however it's a moot point for two reasons:


The aircraft was already too low by that point.
The PF was still pulling up - hence the "DUAL INPUT" warning.



It spent 43 seconds 'parked' at three degrees NU. It did not trim NU as the climb began and continued.

Yes, because the elevators' authority was sufficient to meet the demand.

PF's commands were a combination of ND and NU, and some time was spent -1G. So it should have trimmed, what inhibited it?

I've said this more times than I care to think about, but because the ND command has to be *sustained*. In the A320 sim, from THS full-NU to return to neutral required full forward sidestick input for about 8 seconds. The PF never applied corrective inputs for anywhere near long enough.

I was asking bubbers44 what he thought.

For which you'll get an answer in line with his way of thinking - i.e. that the traditional control setup is the best way to do it.

[Lyman]

Since when do the elevators act alone? Trim is automatic, and so quote me where it is printed that trim won't follow? Include trend please, and g references.

Quote. "Because it was never commanded to - none of the inputs of the PF and PNF were ever sustained long enough to make a difference, with one exception. The PNF's input at 02:13:42 would probably have been enough to move the THS - however it's a moot point for two reasons:"

Eight seconds w/o trimming? Reference if you do not mind....

"For which you'll get an answer in line with his way of thinking - i.e. that the traditional control setup is the best way to do it."......priceless

[HazelNuts39]

Lyman,

If you take a look at figure 64 of the english version of the final report, you will see that
(a) the THS did not remain 'parked' during 43 seconds, and
(b) the THS is too slow to follow quick movements of the elevator.

[OK465]

...from THS full-NU to return to neutral required full forward sidestick input for about 8 seconds. The PF never applied corrective inputs for anywhere near long enough.

Parked on the ground, you can hold the SS full forward for 8 seconds, 8 minutes, or 8 years and the THS will not move.....

.....because there is no change in the existing dynamic pressure.

[Lyman]

HazelNuts39


HazelNuts39 Lyman,

If you take a look at figure 64 of the english version of the final report, you will see that
(a) the THS did not remain 'parked' during 43 seconds, and
(b) the THS is too slow to follow quick movements of the elevator.

According to the traces of THS in IR#3, it was parked for 43 seconds.
How is a graph different due language in the accompanying text?

Too slow? So it ignores trends over time? Pretty easy to circumvent its action; so then why retain it? Bump the stick many small times so as not to wake the beast?

I trust you, as always, but here I do not believe you. For me, I would need to see the pertinent data from Airbus, re: trimming.

WAIT.... So that is why all Bus drivers stir mayonnaise? Eureka, now we know they do not like Autotrim either. Small bumps and suss... Small bumps and suss, etc. etc. fear? Or loathing? Both?