CONF iture

IF789,

We did switch 2 ADRs off in order to degrade to Alternate Law.

As always, on the Bus, the less you touch the stick the better you fly.
We had no problem with the roll, but did the practice with no simulated turbulence.
Overcontrol and following oscillations can be easy depending of turbulence level.

The sidestick has that particularity, even in Normal Law, to easily, and well unvolontary, induce some roll when full back or fwd stick is applied. It is noticeable when conducting a GPWS procedure.

Machinbird

Clandestino
The control power of the THS is not what we are interested in so much as the effect of trimming all the way up to the stall. Test pilots avoid doing this for good reasons.
It is difficult to get the aircraft out of a stall when it is trimmed right up to the edge of the stall or beyond, particularly with a THS type aircraft.

Do you really think that just because the aircraft functioned just the way the designers set it to do in some obscure corner of the envelope, it is perfectly OK?

Old Carthusian

Autotrim - yet another red herring in search of a barrel to join its other compatriots. The evidence from this accident points to human factors, nothing more/nothing less. It isn't about the technical aspects or how the machine functions but what caused two supposedly rational beings to function the way they did. It's internal not external which seems to be missed by so many posters.
I have mentioned this before - KNOW YOUR MACHINE or professionalism. This was drummed into me by my flight trainers. No excuses - these pilots did not know what to do and this caused the accident. It seems to me that for some commentators the unthinkable is that the flight crew could have reacted as they did. Unfortunately that is the reality and grasping at straws doesn't help. There was nothing wrong with the aircraft but everything wrong with the human reaction. Try to focus on this ladies and gentlemen and the discussion will be much more fruitful.

ChrisJ800

"nothing wrong with the aircraft" hmmm I seem to recall there was a string of ACARS messages and errors including UAS, reversion to Alt 2 Law and other aircraft issues...

Old Carthusian

The aircraft performed as it was supposed to and the control system did the same. It responded to the UAS as it was designed - it was the crew that didn't respond appropriately. Remember, the aircraft stayed in level flight within the parameters of its designed flight envelope. It was the PF who put the aircraft into a stall.

Old Carthusian

The aircraft would have continued flying within the flight envelope - it was not in a dangerous state. You should go and reread PJ2's comments (on one of these myriad threads) on doing nothing. As a pilot one evaluates and then acts. One does not act and then wonder why things go wrong. One scans ones instruments, absorbs the information then in this situation pitch and power.

Now this is not about 'crucifying' the crew it is about understanding why the accident happened. The simple fact is that it was the crew who put the aircraft into the situation where it crashed - nothing else. The following points pertain; CRM, training, crew knowledge of SOPs, lack of knowledge of the machine, airline culture. All these combined to cause the accident in what was a survivable situation. This is the simple fact of the matter, if one assigns responsibility one has to look at the crew and the airline and its procedures.

HazelNuts39

Some time ago I wrote that the airplane's pitch and power at A/P disconnect was consistent with AP & A/THR maintaining altitude and speed while flying in an updraft of approx. 1000 fpm. It would have continued in those conditions as long as the updraft lasted. After leaving the updraft, it would have descended at 1000 fpm at the pitch and power and airspeed it had at A/P disconnect.

P.S. The above assumes that the FCPC maintains pitch after AP disconnect and leaving the updraft. If it maintains 1g, it would need to restore the still-air pitch of about 3 degrees nose-up, and the airplane would then decelerate at about 1 kt TAS per second at constant altitude.

Flight Instructor

I've just read a different thread on this accident and it threw up one big question for me. A lot of people seemed to kept mentioning deep stall (as this is also what the media called it) however was it deep stalled or just deeply stalled? Two very different things. Some people on the other thread seemed to have as little understanding as the many articles you can read about it.
Can an airbus even deep stall? Aren't ALL aeroplanes that can meant to be fitted with stick pushers? or is that something airbus could have got around?

Thanks

sensor_validation

@Flight Instructor
Stall (flight) - Wikipedia, the free encyclopedia

HazelNuts39

For some people 'deep stall' is synonymous with 'locked-in stall' i.e. a condition that cannot be recovered by normal use of the flight controls. For others it just means deeply stalled.
"Can an airbus even deep stall?" Several 'experts' on this forum doubt it. The response of the airplane to slight relaxation of the pull on the SS seems to indicate that the airplane would pitch down with a determined nose-down input.
The stalling characteristics requirements apply with all systems functioning as designed. In the case of the A330 that means Normal law, which does not allow the airplane to exceed the stall AoA, and can even effectively act as stickpusher as demonstrated in QF32. Alternate law is a failure condition that is judged on the basis of its probability of occurrence and the ability of the crew to handle it.

chrisN

RetiredF4 wrote (post 1633): “I´m interested in the "why", and as anybody can have a reason to do something or to don´t do something, the answer might be in the interactions of PF input and AC reaction as felt and understood by the crew.” (Re why did the PF pull back into and keeping the stall.)

Unless BEA release more CVR data or an analysis of that plus other data, I doubt if we will ever know for certain, but early on in one of these threads, there were at least two theories put forward by others:

1. Initial pull inadvertent, while “stirring mayonnaise” trying to control roll. PNF was telling PF to be more gentle with the SS, (but PF took little or no notice?).

2. Soon after, however, PF was evidently doing it on purpose. Possible reason – he thought they were overspeeding, and was trying to raise the nose to correct this. (If at the same time as TOGA, this seems to me inconsistent thinking on his part – but comments like “see the crazy speed”, later “I have been pulling up most of the time”, and reported high noise level which a witness is rumoured to have heard on the CVR playback suggested to some that he confused stall and downrush noise at high AoA with overspeed noise, probably never having heard either before. Didn’t he also try brakes, until PNF told him not to? Also, after PNF took over SS control briefly and stopped pull back, PF resumed (without the mantra “I have control”) and pulled back again, AIUI. That had to be deliberate, and not agreeing with PNF’s apparent belief that it was not overspeed.

(These were the tentative conclusions of ATPL’s – I am simply recalling them.)

These are the reason I mentioned that when a stressed pilot forms the wrong conclusion, he/she tends to stay with it regardless of ineffective attempts to correct the wrong problem, in my post 596 on the “final crew conversation” thread on R&N.

gums

As posted way back, at least one jet I flew had a true "deep stall" in which recovery using conventional control movements was not possible. I even posted the graph of pitch moments. The good news was unconventional control applications could "rock" the jet outta the deep stall.

I can not say if the AF447 jet was in a true "deep stall" without seeing the pitch moment charts for its c.g. and AoA. I would say the thing was "deeply" stalled and held there due to pilot inputs and the trimmed stabilizer that reduced nose down authority.

As another contributor posted here a day ago, a similar condition in the sim was overcome and he flew the plane out of the stall.

Lyman

I put great faith in Hazelnuts' analysis. The problem is in accepting it without further questions. The a/c's actual vertical speed was 1000fpm?

At the moment of a/p disconnect, does PF sit on hands? He has a Roll to the right to contend with also. Does he resist the urge to "Have the controls"? Because that means touching, and handling. Why touch and risk the displacement of the stick, if the book says 'don't touch'? Or, "Do not maneuver"? Sophie's choice? An after the fact pronouncement on an anonymous forum doesn't qualify as SOP.

Further, let us entertain that the a/c has not "settled" on 1000fpm, but was in some trend, and the PF felt, and understood the g forces to his satisfactory conclusion? Right or wrong, he is now 'seat of the pants', and that might be a bad thing. We know he is inconclusive about accel cues and audio feedback in the flight deck. In his own voice....

Was his flight path the result of a risky blend of poor memory/training/experience in hand flying with some 'cheek' input? TTex has posited armrest misplacement, and is it possible to believe that PF never got the chance to fasten his restraints after a conversation or other? The only clue we have of his re: stick work is his "I have been pulling for a while".

In the 5-10 seconds of loss of autopilot and manual acquisition, the die is cast. Following this 'potential' conclusion, we have examples of literally dozens of holes/cheese. My contention is that from this early point, the cheese was mostly hole, little cheese.

CONF iture

I'm not sure where you see this ?

What I do see at AP disconnect time is a selected negative vertical speed of 5000ft/min and a vertical speed going in that direction (the quality of the given traces is somehow poor ...)
I also do see a pitch at zero (that's 3 degrees below the usual cruise pitch)

If what I do see is reliable (?) the initial action of the PF to pull is totally justified.

HN39, how would you justify the AP/FD vertical mode trace is not published ?

Lyman

At no time in two years plus has anyone questioned the NU input of PF at handoff. Only insofar as he should have left the a/c descending at 3 degrees. Have I missed something? This has been the position all along, the a/c needed handling.

The ND reflects A/P reaction to substantial UpDraft.

The politics of the initial BEA report reflect the wisdom of the PF's pull.
"The a/c did not initially respond..." It is their way of throwing PF and the a/c a bone...... The resultant climb, when it occurred, had the benefit of the airmass, and in AL2 should have trimmed NU. It did. Six Degrees? The 1.65 g was the result of these factors, not the pilot acting alone.

The jet was manouvering at a/p loss, and can be considered to be Upset, at this point. LOC came later. Twilight Zone, anyone? ffs.

An opinion can be put forth that this a/c was uncommanded for as long as 5 seconds. That qualifies as Upset.

How sinister is the creep of Urban Myth.

HazelNuts39

If you are referring to the 'zipper' trace on page 111, I don't see any effect of that on the airplane's behavior. If you look at page 42 you'll see the AP maintaining altitude with very small variations of V/S due to the turbulence that is more explicit in the trace of normal acceleration. I explain the pitch of zero (that's 3 degrees below the cruise pitch in still air) by the autopilot pitching the airplane down to maintain altitude in a somewhat stronger upcurrent that commences at 2h10 (*). Pitching the airplane three degrees down in still air would change the FPA three degrees down, i.e. result in V/S=-1000 fpm. To prevent the airplane from accelerating on the downward flight path, the thrust must be reduced. The A/THR appears to do just that, although it doesn't quite reach the level required for that FPA (page 113).

That may be so, I was only answering a question.

I have no opinion on that, except that its omission in the interim report probably means that the trace does not provide significant information.

(*) That 'somewhat stronger' updraft may well be responsible also for the rolling motion and for the very particular type of ice particles (crystalline structure, particle size, density) that clogged the pitots of AF447.

DozyWannabe

Remember that could also just as easily be an "invalid value" rendered as the lowest possible value in range by the graphing software. I'm not arguing it's definitely one thing or the other, but given the aircraft's actual trajectory I'm inclined to think it's that. Given that it occurs prior to AP disconnect, I'm also inclined to think they'd have noticed and pointed out flickering values on the FMS display if they'd seen it as there wasn't much else going on in the flight deck at that time.

Lyman

Deep Stall? She came close a couple times to a smart recovery. Deep is a misnomer.

Clandestino: "The a/c wanted to fly." I agree, and there was airspeed available, just a too high AoA. The Stall entered unconventionally, and any recovery would have been the same. How many Stalls have been recovered in type? In these conditions?

bubbers44

Most pilots don't put it in a stall condition when they have a simple loss of airspeed and an autopilot disconnect. They have the experience to know what to do.

grounded27

I am surprised to see this thread go soo long. The simple answer is power and pitch, the varible being TC's.