@Capn' Bloggs : Again, somewhere on the Tech Log threads at least one Airbus FBW pilot stated that F/Os train on both sides of the flight deck, so left/right-hand orientation should not have been a problem.

Dozy, thanks. I missed that. We swapped seats on our Boeing course too. I just wonder how much practical time the bloke in the LHS had in that seat, given the predicament he rapidly found himself and his mate in. 4000-odd hours is not a lot when considering FL350 on autopilot 900hrs/year, hardly touching the stick and being in "wrong" seat, even given that they train in both. It would appear that the training they got wasn't all that flash.

Lomapaseo, in my book, skill is the most essential ingredient. You shouldn't need much knowledge to fly these things, either in or out of a stall. I do wonder about the wisdom of needing to remember to trim forward in this situation when you never do it at any other time (as far as I can make out, not being a bus driver).

Aeroplanes cannot recover themselves yet, but it seems managements the world over have let pilot's skills atrophy all the same.

Capn Bloggs

By identifying it as "skill based" shortfall, it sounds like it means that even though they knew that they were in a stall they did not know how to recover from it.

I suspect that ther may be some arguments against this.

and if it requires a "unique" knoweldge of the use of "trim forward" than that would be a " knowledge base " shortfall.

Lomapaseo, I see your point, but you didn't give us a "Situational Awareness" option, only a "skill" or "knowledge" option. ;)

By "skill" I mean the ability to observe the instruments, identify the situation, then decide what action to take and take it. :ok:

I would take it a step further.

Skill involves knowing when to ignore "Knowledge". It is unavailable to the format here, where rote and reference command at all times. Skill involves risk, and the ability to instantly observe, orient, decide, and act. If it is down to knowledge or memory alone, we are all screwed.

Knowledge PLUS Experience = Wisdom. And experience is not taught, it is acquired.

Lyman, thanks for that gem!

There is a difference between doing "things right" and doing "the right thing"

Capn Bloggs

Understood :ok:

Now that is basic use of all traits.

If it can't be demonstrated during training than a person should not be a pilot of anything. I doubt that the training sylabus needs reworking in that case but the pass/fail needs reviewing.

back to lurking looking for some new facts again :)

He knows that deep stall has specific meaning: the stall that cannot be exited by using aerodynamic means that are normally at aeroplane's disposal i.e. you need to deploy antispin chute to exit it. He knows that only practical mean to get into deep stall with airliner is to get the stabilizer and elevators in wings' wake when stalled. He knows that the only known way to achieve it is to include T-tail in aeroplane's design. He has seen some A330s and concluded that there are no T-tailed A330s. Therefore he knows A330 is not susceptible to deep stalls.

Do you now know that A330 is not susceptible to deep stalls or do you have issue or few with what I've written?

Argument that "No transport aeroplane has been flown so out of the envelope as AF447 so we don't know what is so far out and there might be deep stall area somewhere out there" is not particlarly meaningful or true and is similar to:

Absolutely not. Coffin corner is altitude at which 1g stall line intersects Mach bufffet line. Only overpowered, low Mach no limited aeroplanes are capable of reaching it and A330 is neither. Coffin corner is not where Vls meets Mmo!

It is bloomingly clear that only pitots were frozen and measured altitude was correct all the time. Why-oh-why didn't he read and understand the report? His arguments are totally invalid.

No. Aeroplane was in alternate law. No protections. This was known two years ago as the message concerning FBW degradation was sent via ACARS.

No. Report 3 is pretty clear on that. It just followed pilots' demand, as programmed to do under the circumstances.

Very well, because that's not what happened and BEA did point that but then you have to understand what was written. Not an easy task for prejudiced, ignorant or both.

It does not. Not in any control law. Rest of your post is based on this assupmption and is therefore not true.

No and yes in that order. :)

Look at the pretty picture of A330 earlier, note the AoA, the position of the tail feathers, and the extended disturbed airmass present about the aft fuselage.

I vote with OK465. Elevator authority is demonstrated how? Tunnel time.

All arguments post STALL have a fascination that is understandable, and useless and irrelevant at the same time, unless certification standards are altered. Especially the funny parts about the instrumentation being reliable.

OK465

It's odd, I guessed you'd popped in between AD's post and mine by a second or so. But time does go by fast at my age.

Time and time again I'd asked if the 330 could deep stall, as there have been sooooo many references to it having done so. What I didn't do was assert myself in the way AD did.

I still do not know if it is possible for the A330 to become LOCKED into a stall - given all of the controls are functioning. I have always assumed it could not, but I've been surprised before.

Is there ANY way it could be stable and unrecoverable given say, <60 kts airspeed and high vertical speed? Again, all controls - especially the tailplane - fully functional.

For the sake of using the same terminology, could we agree to the following ?

A "deep stall" (or "locked-in stall") is the classic term for what happens to T-tailed aircraft, when AoA is such, that the wing wake 'blanks' the horizontal stabilser and negates pitch control.
As stated before, about the only way out is a tail parachute.

A "full stall" (or "fully developed stall") is when you pull the aircraft (any aicraft, Cessna or 747 or A330)) beyond the stall AoA and hold it there, either by control input or by THS trim.
With the horizontal stabiliser below the wing wake, full ND elevator, and trimming the THS ND should allow recovery, even if not instantly.

AF447 was in a full stall, not in a deep stall, as most 'aerodynamic engineering oriented' people here understand it.

CJ

That's as I always understood it.

Looking back, it's strange how we glibly did all our training in BAC 1-11s right through to the push. We didn't have a sim for 5 years and Mike Lithgow and Capt Keys were still very fresh in our minds.

Let's go back to basic aerodynamics. The definition of a 'deep stall' is that the stalled airflow from the main-plane is blanking off the horizontal stabilizer, thereby rendering it ineffective.

By definition, therefore, an aeroplane susceptible to a deep stall must have a T-tail. The Airbus is most certainly susceptible to a 'locked-in stall' (that is, locked-in by the pilot holding the control column hard back), but cannot by any stretch of the imagination be susceptible to a deep stall.

There is some confusion on this thread about the literal meaning of 'deep stall'.

I suggest that, because of the very 'conventional' design of the Airbus, with the wing and horizontal stab pretty much in line (just like a DC3), it is not possible to deep-stall any mark of Airbus.

My point entirely.
I was just hoping to clear up the confusion, and avoid unnecessary posts on the subject.
There's enough confusion on other issues.... :ugh:

The canard configured Velocity had a deep stall problem initially.

No T-tail.

Aero changes were made so they didn't fall on you.

OK.....here I am.....again. Why can't we all just admit that if this had been a "conventional" airplane [cable-operated, not computer/electric-operated] that we would not even have a thread on this?! Let's just wait for the final outcome on the investigation to see just what "they" have to say about all this.

I have been [flying at the time] in a "full-stalled" jet transport [cable-operated] before.....AND recovered.....so I know it's possible.

AD, just curious. How far above the main wing is the 330 elevator? Is it a similar distance as, for example, a BAc 111?

You simply can't confine deep stalls or super stalls to T-Tail only types. It is entirely possible to get a deep/super stall on a conventional (read not a T-Tail) type. A swept wing is actually more prone to a deep stall than a T-Tail but a T-Tail is harder to recover, hence pushers and all that jazz. Remember swept wing pitch up?!

I haven't read the entire million threads but does anybody know where the CofG was?

DC-ATE. Disagree. For the simple reason there is no data to rely upon, and intuitively, the difference in fbw, cables has naught to do with this STALL.

Just as the discussion is not only O/T, it is off Planet.

It isn't necessary to display good behaviour whilst STALLED to get the cert.

For ducks, my opinion is that the ship would begin a recovery as the elevators went nose down, but as drag decreased on the tail plane, it would regain its nose up designed in behaviours due better aerodynamics/drag, and the airframe would be unrecoverable. UNTIL THE THS MIGRATED BACK TOWARD NEUTRAL< AT WHICH TIME THE NOSE COULD DROP< AND RELOAD THE WINGS>

Without trim, the a/c would have recovered itself, even with full up elevators. Eventually, nose down elevators would be needed, or its porpoise into the sea, imo. Also less thrust would be nice. My guess is at first drop, the pilot would grok his space.

M'Lud: The cofg was initially reported by BEA as 37. They changed that to 28, later, without explanation. And generally without comment here.

Mustn't discuss.

Wait, could the 5000fpm VSsel have been the a/p response to command from FCM to load the tail due AFTCG? hmmmmm....

After a time w/o the cg adjust, did a/p drop as a result? Could that have been the chronic nose down the PF was hobbled with? Musical cg's?

Horizontal stabilizer.

'DNA of flying' (i.e. 'regular aircraft'), training and FBW must be an issue.
 

Thanks HPbleed. Not trying to AB bash. Have travelled on most of the AB range and all the Boeings (and few others too). Having been in the IT industry for 30 years I've seen every type of software human interface failure you can think of. And new generations of developers/engineers keep coming through with even bigger convictions that technology will "save us all and take us to the promised land"....Human performance improvement through the art of listening, understanding, acknowledging, valuing and respecting PLUS the development and use of technology is where we'll see the most benefits achieved, but most industries and businesses are still very slow to understand this and the technocrats still push their philosophy without due regard for their and technology's inherent fallibility.

Auto trim sounds just great, but I can imagine even a simple concept like that could have you confused in amongst a systems failure in trying conditions and it's the overall response of the AB's 'ecosystem' (to put it one way) I'm wondering whether has been fully thought through.

Some of the 'protections' built-in to the systems must also be contributing to some deep seated misunderstandings about operations within that 1% area where the machine is no longer 'protecting' a pilot's inputs.

Hey iceman50, I wasn't for a moment saying the crew wasn't trained to handle the dark or IMC, I'm simply saying that these conditions PLUS whatever occurred at AP and A/THR disconnect (and yes I take your point that at that moment it was not 'extreme') PLUS the AB's system's response(s) PLUS the potential poor crew initial response PLUS potentially other things none of us can be clear on yet, facilitated a complex mix that the crew couldn't understand and this must be partly a training issue as well as the man-machine interface psychology issue that makes me concerned this type of accident could readily happen again.
Thanks Clandestino; glad you've cleared that up for me (although given I was pretty good at that old video game [which someone reminded me was actually called 'Asteroid'] I was thinking I'd be in a good position to head on up to the cockpit of an AB if the entire crew became disabled and a call went out to the passengers "can anyone onboard fly?"!) Please don't just write off the rest of my post. One of the challenges on forums like this is that if you display some ignorance, everything else you've said just gets flicked away and the potential for the debate to morph into something that might help can be lost. I (and all other crew/SLF) want to be able to travel on these airliners confident the crews flying them are trained well enough to cope with the complex scenarios and multi-faceted problems systems failures can introduce.

The rest of my post was an effort to highlight "(the) man-machine interface psychology, economics, politics and big business needing to come clean and invest more dollars into research and training rather than just about this particular crew's lack of ability, perceived or otherwise". I think that is still the major concern here and how crews can ensure they're ahead of the curve on comprehending what the machine is attempting to do. These highly automated systems are a miracle of ingenuity and technical brilliance but what appears to be missing is an overarching realisation that it is simply not possible to cover every combination of potential system responses to incorrect data input and the likelihood of a subsequent incorrect human interpretation under the extreme stress of an inflight emergency (and being in an stalled airliner [regardless of how the stall was entered, who was responsible or what warning horns were sounding either continuously or intermittently] travelling downwards at 10K FPM with just a few minutes left is an environment that makes the phrase 'extreme stress' sound like an understatement) is very real and likely to occur again and with increasing regularity given lowering of crew standards.

Hi ChristiaanJ

I'm not an 'aerodynamic engineering oriented' people, but I do agree with your post #373 and thank you for it, as it lifted the doubts I still had regarding the terminology. :D :ok:

Just have a look at this graphic to confirm what ChristiaanJ has posited.

Don't forget that the THS at 14 degrees nose up "blanks" the elevators, and since the HS is TRIM, the PITCH is effectively "blanked". When flying with a loaded (unloaded v/v its purpose) tail, PITCH can get "squirrelly" Especially ND. The THS is trimmed ND for aft cg, so 447 was off to a risky start in her climb. Trimming it up, whether auto or manual, is not a good idea. There is a case to be made for her climbing in default with the THS at ND set. This a/c should have been descending, whether computer, or manual. imho. Temps, aft cg, etc.

Some points i like to remember in viewing this graph:

The AOA was considerably higher than 30°, BEA states that it never went below 35°. In a former thread the AOA was computed (GS and descent rate) at something like 60°.

The graph assumes, that the FPA (flightpath angle) would decrease with the THS and elevator full ND. Out of my practical expierience and my theoretical knowledge with full stalls and spins the FPA would increase considerably in the process of reducing AOA due to increase in descent rate. That leads initially to a chasing of the AOA. If stopped too early, secondary stall is preprogrammed.

Although the graph only shows the THS and the elevators, the behaviour of the complete aircraft including the point when power can be applied again in the individual phases of the recovery is decisive in the validation of a successfull recovery attempt and the altitude required to accomplish safe recovery.

Another point validating the effectiveness and the time/ altitude required for recovery is the rate, with which the FCPC´s would change the position of the elevators in the short term and the THS in the long term. As shown before, the max deflection of the elevators the crew did achieve (with limitied SS down) was a reduction from 30° nose up to 15° nose up. And this reduction didn´t achieve anything noticable to the crew. Manual THS trim (nowhere mentioned in the books except in direct law, and never trained) and prolonged ND input would have been mandatory anyway.

It is easy on the paper, but it is already challenge in the aircraft in pure VMC with all gadgets working and it might have taken a wonder to do it in the Cockpit of AF447.

mm43 - what is the meaning of 'AoI' in your diargam? If it is 'incidence' I think we need to be careful on definitions, but I cannot see that it has much relevance anyway.

To follow Franzl, some while ago in discussions somewhere in this maze about 'recovery' I said that the pitch change required to unstall could have been as high as 50 degrees nose down - well past the limits most pilots would contemplate. This would indeed have drastically increased the rate of descent until sufficient manoeuvre capability was there for pitching nose up, which is why my subjective assessment of min recovery altitude from THIS stall was around 20k.

I don't really want to be dragged in to the SS/yoke battle except to say that if I had been dragged out of my pit in my silk pyjamas and arrived in a cockpit at 35,000' with 15 degrees nose up, 10,000fpm+ and a co-pilot with the yoke back in his groin, I might have had a clue as to why the nose was up that high - I hope so.

Thanks, now corrected.
Wrote that after mid-night... should have checked it better.

Sorry for the delayed reply. I don't know how far above the main wing the 330 horiz-stab is, but I would guess that the designers would have ensured that, at a main wing stall alpha, the horiz-stab would still be flying.

The BAC 1-11 was a T-tail aeroplane.

I do not believe that a swept-wing aircraft is prone, at all, to a deep stall, as the elevator would normally be available for recovery (provided the PH is not holding the stick hard back!).

Regarding swept-wing pitch up at the stall, I understand that, with washout, the wingtip stalls last, retaining roll-control at the point of the stall. Therefore, the tendency of a swept-wing aircraft is to pitch down, not up, unless someone is holding the stick hard back.

ChristiaanJ - Sorry, while I was composing my rant on deep-stalls, you had covered the point very well.

Tips stall first on swept wings, not last. Washout reduces the effect.

edit: tips stall first on rear swept wings. The X29 featured foward sweep to get around this as does the HansaJet.

But I understand your point about pitching.

Guys - with the estimated AoA's we have in this accident you can forget which bit 'stalls first' or 'tail blanking' at 60 deg AoA the whole wing is so stalled that it matters not, and the tailplane would be well in the airstream.

From the old days, AOI = Angle Of Incidence.

The new Air France board of directors after the Stalinist purges :)

Air France - Corporate : Board of directors
No more Gourgeon and Schramm .. the (bad) arrogants spokespeople after AF447 event

Nope. It did not.

First, regarding the deep stall, we were discussing airliners, not GA types.

Second, GA canards like: VariEze, LongEZ or SpeedCanard have low wing loading, relatively high speed range (relative to min speed, that is) which necessitates use of large foreplane - compared to wing. Now this foreplane absolutely must be designed so it stalls before mainplane. If it were otherwise, loss of lift at mainplane, combined with still working foreplane woud introduce such a pitching momentum it could tumble the aeroplane end-over-end and that's the issue with GA canards. This tumble is very possibly irrecoverable but is not deep stall.

Third, I am sure that there were numerous witnesses who saw F-GZCP taxi out to her fateful flight and I have strong reasons to believe that not one of them will testify she was canard equipped.

No. Lower. Further back.

Please provide reference to this statement of yours. I really wonder how is it possible to not put the conventional mainplane below the wing's wake at stall and beyond.

Only in the tales of yesteryear, when swept wing was largely an unknown quantity. Since then, wise aerodynamicists came up with something called "washout". When measuredly applied, it assures that roots stall first, thereby: 1)eliminating pitch-up associated with tips that stall first 2) reducing rolling momentum from asymmetric flow separation - separation now occurs closer to CG in lateral sense 3) keeping the outboard ailerons effective. Statement that:was true when Huns were en vogue. Nowadays, on swept wing transports, washout reduces the effect to the point of elimination, as was tragically proven by certain crew of certain airliner that fell flatly into Atlantic without gyrations that have to be expected with tips stalling first


In both cases primary consideration was not elimination of wingtips stalling first.

X-29's forward swept wing was intended to direct spanwise airflow towards the fuselage instead of towards the wingtips. While this does reduce the effective AoA of wingtips, with forward swept wing the roots that stall first will cause pitch-up so exacerbating the problem which FSW was supposedly intended to solve.

HansaJet's wing was mid-mounted so there would be minimum fuselage diameter and minimum interference drag from wing to fuselage joint. It got forward sweep so wing centre box would not impede on cabin space. Hansa Jet is T-tailed and stick pusher equipped, therefore her stalling characteristics are of academic interest only.


The amount they have already invested in research and training is closer to gigabucks than megabucks. That so far we have no official word that Airbus MMI is sub-optimal or even dangerous boils down to two options a) while imperfect, it really is acceptable b) there's large worldwide conspiracy covering the fact that it really is sub-par and kills people.

Which one to believe? Tough one, ain't it?


Rest of youth post is spot-on, I just have to comment on this. It is not trained because it doesn't work. You can forcibly move the wheel to position of your choice but the FBW will return it to the position it deems to be necessary once you loose your grip and all the while will try to combat the trim with elevator to satisfy G demand.

There's no use and no need for manual trim while auto-trim is working.

It is one of the factors but given the contents of the threads we had dealing with AF447 so far, it tells more about ignorance of the posters than alleged complexity of FBW Airbuses.

I suspect that main reasons the AF447 tragedy got so much attention on PPRuNe are a) it involves large body count b) it involves western built and operated widebody c) it involves relatively new flight control technology that is easier to deride than to understand d) most of the posters just can't dismiss the whole affair by using some of their deeply rooted prejudices. If it happened in CIS, they'd conclude it was vodka-caused. If it happened in Africa, it would be corrupt CAAs and shoddy maintenance that doomed it. If it happened in Asia, well it must have been a strong cockpit authority gradient or some similar cultural thing. South America - machismo. Regional airlines - inexperience and poor training. Turkish - exmilguy not well adapted to civvie world.

Well, we're out of prejudices here as it happened to long established western flag carrier. Most of the posters feel that it struck close to home and they can not write it off easily as something-that-can't-happen-to-me. Mental gymnastic they perform to deal with their shock and horror is very interesting thing to behold but its results are not particularly informative.

A very important point, and i´m glad you mentioned it. I raised that question (how would the FCPC´s behave during manual trim when not in direct law) some moons ago. Nobody followed my lead there.

Clandy: The first quote is yours and the second is from an NTSB Velocity accident report. You can do a search on the NTSB site and find it in one of the 8 reports for the Velocity. You'll know which one. PAGE 1E. (No tumbling mentioned here.)

Your post was discussing 'aeroplanes'. The Velocity is an 'aeroplane'. Your claim was that 'only' T-tailed 'aeroplanes' could deep stall.

Quote:

---

He knows that the only known way to achieve it is to include T-tail in aeroplane's design.

---

Followed by a claim that no Velocity aircraft ever deep stalled. I believe your words were: "Nope. It did not."

Does the Velocity stall description bring anything to mind?

Just curious, when was the last time you positioned the trim manually in a stalled A330?

You know guys, if you get that THS out of position, you are going to have one hell of a job to do.

If the AP (or someone else) trims it nose up (or down) and then hands you it. What are you going to do?

I remember an incident where an inexperienced pilot got a ERJ-145 out of trim THS wise. Luckily it was nose UP. Come to think of it, 447 was nose up too. Glad the Barbie-jet pilots got out of it.

Anyways. My main point is this:

That tail needs to be pointing where you're going.

If it isn't- you're in a world of !!!! until it is.

Clandestino,

Not quite. Even if the entire length of a wing, swept or straight, stalls at the same time the separation of the airflow occurs towards the rear of the wing causing the centre of lift to move forward. Unchecked that may cause pitch up.

I can't, I have paper copies of several flight test documents on controls and stability.

Did you not spot the part about several roll excursions, some up to 40 odd degrees and the 270 heading change?!

It is not the tendancy of a T-Tail to deep stall it is the recovery that can be a problem. Note that the King Air, although a T-Tail, is not prone to deep stalls, straight wing you see!

Isn't this why some types have a stick nudger to ensure pitch down at the stall?

The purpose of washout (look at the outboard 1/4 of a 747 wing from the rear) is to prevent this entire-wing-stall-at-the-same-time. The entire wing won't stall "at the same time", surely?

Sorry. Once again : prior to june 1st 2009 Air France F/Os did NOT get any, on purpose, left-seat flight training.

Some sim sessions ("true" captain not compulsory) just happenned to be with a two F/O crew but the purpose was not to train F/Os in the left seat.