And in so doing establish a commitment to a particular, and artificial, Angle of Incidence. This is fine in cruise, but maneuvering an a/c which has cranked in a preference for one (Pitch)or the other (never both), becomes a challenge in adapting to the response of one airplane depending on a very important factor.

Changing the characteristics of an airfoil has dangers inherent in its "benefits". Neutral stick is no such thing when 16 degrees NU, it only "Logs" neutral, and when the deflection cannot be read, there is your guessing game.


I'll stick with swash, and internals. Maybe a particle separator. For the motor, not the pitot.

In the Traces, I'll be looking for gee. Just like Perpignan, but this time at the beginning of the crash.

Bear, take a look at page 5 here. http://www.kamanaero.com/images/PDFs...2020050727.pdf

I flew for a few years with Kaman's servo flap system. It's very responsive to pilot inputs. You don't need hydraulics(though they are handy, and with hydraulics gone, the collective is tiring to move and hold in position).

I personally prefer it, stick and rudder wise, to the swashplate that needs 3000 lbs of hydraulics to change pitch on rotor blades. (Down side, of course, is more parts and thus more maintenance worries ... so it goes, no free lunch ... )

As to the A330 THS and its teaming with the elevator, is there something to be learned from the UH-60?

In that cockpit, you will always know where your Horizontal Stab is (a FBW surface that moves) because there is a guage that tells you its deflection from the horizontal, on the center console. (That gauge is pretty important, since if you are flying above certain speeds, full down Horizontal Stab will kill you due to a nose pitch that the rotor system can't overcome).

From the various material I have access to, on the A330 can all up your THS on a standard ECAMS page. I am not sure if that display is the default or not.

Food for thought, in re knowing what your airfoils are doing while you are flying. Did the crew know where it's THS was? Interesting question, but the more critical question, beginning with the initial LW/NU move on the side stick, is

Did the crew know where their nose was relative to the horizon? (Particularly before apogee was reached).

I don't quite understand the obsession with the autotrim - clearly this would be a concern if they had gone down with sustained full ND input, fighting a hopeless battle against the evil THS. From what we know this was neither the case nor do they seem to have lost all pitch authority...

The concern seems to be in sussing out whether the trim functions in ALT-2 (or in AA Law, which some still suspect was in effect at some point) had an influence on nose pitch attitude in the first half of the event. If no, then solution is in one direction, if yes, then it goes in another direction.

After that, the problem seems to be one of pitch authority: was there enough?

Sidestick, Elevator, and THS
 

Quote from PJ2:
Your previous post on the THS on thread #4, here, explains the THS operation very well and this one connects that explanation with how the THS likely functioned with AF 447. I think its a reasonable explanation of what occurred to the THS and how, after the initial pitch-up.

Thanks for your kind acknowledgement of my recent beginners' guide to "Primary and Secondary Pitch Control" on the previous AF447 thread, which also attempts to describe very briefly how the basic concepts are applied on Airbus FBW, and their relevance to AF447.

The key to the THS movements are, of course, how much elevator the EFCS is using: you explained that here before I ever did.

In a couple of follow-up posts, including the one you have quoted in your post, I tried to develop the argument to describe part of what may have been happening with pitch control as the aircraft reached its apogee, and immediately after:
http://www.pprune.org/tech-log/45465...ml#post6559334
http://www.pprune.org/tech-log/45465...ml#post6560444

Finally, I offered a partial explanation of the problems the PF seems to have been having with roll and pitch control using the sidestick, and how the EFCS may have interpreted what it thought he wanted in pitch.
http://www.pprune.org/tech-log/45465...ml#post6561309

Quite how the aeroplane eventually established itself in – as others have commented – a remarkably stable descent at AoA > +40 and pitch ~ +15 remains mysterious, partly because this is uncharted territory in terms of the aerodynamic performance of the fuselage and THS, as well as the wing. The resulting pitch-moments are therefore unclear. In that context, I recommend a look at Meikleour's contributions, the first of which is here, which relate to a simulator exercise many of us have not done.

The other unclear factor is how the C* pitch-function of the EFCS would treat the invalidation of CAS (IAS) data, when determining the crossover from g-control to pitch-control. As I understand it, that crossover is normally a gradual transition as the airspeed falls below a certain figure in routine flight. Understanding how the UAS affected this will be the other key step in solving the relationship between sidestick position, elevator/THS position, and the achieved trajectory.

As these pieces are on the previous thread, the links provided will enable you to reach them more easily, and I look forward to any comments or objections. If none should be forthcoming, I shall infer that even the most erudite of our contributors find nothing to disagree with in my proposals... ;)

Did the PF know his Pitch (attitude) at a/p loss? Of course he did.
It was ND, and needed NU. The a/p quits at ND-9 degrees. That much? Either way, the PF input NU, there is no call to question the decision?

Hi Chris,
I agree.
It would only have needed a small amount of rudder trim to have levelled the wings (a technique forgotten / not learned by FBW crews). The stick could then have been released and used more normally to control the attitude. I suspect PF was struggling somewhat to maintain wings level (Meikleour previously described how "twitchy" it was in roll in ALT LAW during his loss of airspeed event).

Chris - I understood that the C* in the AB switched at around 210 kts so I would expect the FCS to be pitch rate driven during the 'climb' and not Nz, especially given the supposed low IAS readings?

Bear - how on earth do you arrive at pitch -9? Is that what you are proposing now?

View from the P3 jump-seat (continued)
 

CONF_iture,

Many thanks for going to the trouble of obtaining and posting excellent photos of the view from the P3 seat in daylight. They confirm my A320 recollections, after a gap of nearly ten years. If in its stowed position, it should be safe to roll the P3 seat forward to the position the photos were taken from, although the pitch of +15 might have made it difficult. Was the captain merely standing?

As you say: although the sidestick can be seen, provided the PF's table is stowed, the console lighting would preclude this at night – unless the dome floodlight was on. In any case, its position would be unclear if it was in the palm of his hand.

THS position should not be a problem, provided the observer's eyes were adapted to low-light conditions.

@GeradC:
 

Because 1 hand on 1 stick, connected to 3 xdcers commanded the 3 FCPC - in ALt 2 - to do so.
(In the absence of ss xdcr, FCPC or pitch system faults, it wasn't a 'flaw' order generated by the system itself.)

Maybe because flying at 60 kts, 15° pitch and 40° alpha was not accounted for?
Ask B. they quit all the signals at 30Kts, so between 30 and 60 flight seems to be possible with that one!?

rudderrudderrat,
Yes. That the PF was struggling with roll-control may have overloaded him. Later, at very high AoA, resultant sideslip would add to probe problems, as has been said. At that stage, was the use of aileron/spoiler productive, counter-productive, or irrelevant?
I'm interested in your rudder-trim argument, but don't see how it would counter wing-drop if the latter was caused by turbulence.

BOAC,
The 210kt crossover seems to be a popular figure. I think there must be a gradual blending-out/blending-in process, to make it seamless to the pilot (which it is). But, as I said, what logic is applied when/while airspeeds have been declared invalid?

BOAC

Steady on. -9 degrees is the a/p limit, the a/c Pitch has not been supplied by BEA. Except in + range........ (perhaps ND does not concern?)

:ok:

Good morning Bear,

I do believe one has to look at the two minutes before AP/AT disconnect and at the moment there is no information from time of 2 h 08 min 07 and 2 h 10 min 05. The speed was reduced to about Mach 0.80 and the turn to the left was initiated at the start of this time period. Although the BEA never specifically has said the pitots became clogged with ice crystals (nor should they at this stage of the investigation), it is apparent they are strongly looking at this as the starting point of the total event. I also think the clogging was not one where in one-second the pitots were clear and then poof, in another second they were clogged. It probably happened on a gradual but ever increasing basis over these couple of minutes or so.

Speed
So as the pitots began to clog, the sensed airspeed by the computers began to go down. Now I can't imagine the computers observing this degrade in speed sat there and did nothing, but perhaps Takata can provide the computer reasoning and logic in this situation while in AP/AT. I would think they would signal the engines to spool-up and increase the speed to maintain level flight the AP was attempting to do at that time. Unfortunately, the sensed speed degrade was wrong and the aircraft was gaining speed it didn't probably require in level flight. I would assume that when the AT dropped and thrust lock occurred, the thrust was locked at a higher N1 setting than perhaps the PF thought it was at?

Pitch
I am not going to comment on this aspect as to what the computers were doing or not doing. But rather, some questions about an observation I noted in reading the reports regarding aircraft balance. In the very first BEA Interim Report, dated June 1, 2009, at the time of the beginning of the incident, the aircraft weight was estimated and reported at 205 t and an aft balance between 37.3% & 37.8%, controlled within 0.5% of MAC. The second BEA Interim Report mentioned nothing in this respect.
However, in the BEA Update, dated May 27, 2011, The weight of the aircraft was again reported at around 205 t, but the balance was changed to 29%, or in other words moved forward 8% or so. I thought the aft balance (37.3% - 37.8% reduced drag and improved overall efficiency.
So my questions are: How did this happen? Why did this change happen? Does this have any effect on maintaining pitch either by the automatics or in a manual fly mode?

Just curious...

Hi Chris,

Correct - it wouldn't work for random turbulence, but only if it was mis-trimmed to begin with (rudder + or slight fuel imbalance + or thrust asymmetry).

"From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input."

TD

A change of 8 per cent in Weight would be 33,000 pounds. So the 8 percent of CG is a whopper. Unfashionable to change such heavy horses in mid stream. It may represent the entire aft fuel load, as if it were foreward, which it was not. Cheating Fuel is an old trick, and it saves a significant amount of fuel burn? The cost is Stability, orienting the Cl to the Cg is hazardous. The a/c becomes more sensitive in Pitch, obviously.

If, for instance the Cg fell behind enough, Up becomes down, and down Up. PF did hold aft stick all the way down, after all. hmmm..........


I am not real clear on the a/p's authority in Pitch, Roll, and keeping the two in line with each other. To me, if Pitch transits got out of phase with Power, their could be trouble? Insofar as rate, I think Power up when Nose down would be problematic, as would the reverse. If the THS is in there, what is the calculated rate for stopping speed and Pitch excursions that are (or have become) unnecessary?

If it is a rate thing, do the a/p's limits constrict? As in, "Keeping Up"? I still think it is a toss-up which came first, the 'slows', or the 'unreliables'.

I lean to the slows.......:confused: leading to hand flight.

Now, will there be some clarity from BEA?

Maybe not impossible, but I think the theory falls at the same test as the idea that updrafts caused or accelerated the climb - namely that the kinetic-potential energy then doesn't add up. Those (not me) that did the maths and posted however many pages back, showed clearly that the BEA figures match the a/c trading KE for PE. Your theory has the a/c carrying additional KE over and above what BEA says (real AS > IAS) before the climb - which would give a higher apogee, I believe.

Yet in several other crashes and incidents, loss of autotrim has lead to LOC (and deaths) as pilots failed to manage the trim along with everything else they were handed at short notice.

Autotrim on or off - no right answer. Whichever you choose as a designer, sooner or later someone is going to die in part because it wasn't the other way round.

Given we've only got a transcript and that through translation - who knows.

I also keep coming back to that line though, and wondering what other indications they lost. Did they lose attitude, distrust it, or just not see it ?

infrequentflyer789

Perhaps not a smooth climb, then, but one with rolling and porpoising? Both eat up energy quickly. The Rolling we know, and the Pitching we can infer from BEA?

Hi Bearfoil,
I really think that you are chasing your own tail all around this thread.
The BEA supplied some informations in its narative. Those they considered relevant in order to understand roughly the sequence of events, mostly because there is still many data they would have to check further in detail or to derive from those rough recorded data. But, be sure that it should not cover the flight parameters while she was still flying in auto-mode as it would be very easy for them to verify immediately if everything was ok until the point autopilot disconnected (cross-checking all speed, altitude, position, parameters from the various sources will tell you straight away if it is right or not).

At AP disconnection, the only thing they considered worth mentioning was that the aircraft started rolling (meaning she was wings level before), we don't know the rate or amplitude; but, do you really think that they would hide to us something very unusual, just before this point?
More likely, don't you think that she was flying as expected at FL350, 275 kt, wings level, +2.5 deg pitch, THS should be about ~2-3 deg NU?

Some of this is already part of the narative:
At ORARO : flight level 350, Mach 0.82, pitch attitude about 2.5 degrees; airplane around 205 tonnes and 29% MAC; Autopilot 2 and auto-thrust engaged...
Further change is noted:
2 h 08 min 07: slight turn about 12 degrees to the left; turbulence level increased slightly; speed reduced to about Mach 0.80.
2 h 10 min 05 : autopilot then auto-thrust disengaged; airplane began to roll to the right...

Beside, AP disconnection, one not due to protections kicking (High AoA or High Speed) or Failures in relevant systems, then due to AP limits are:
- Aircraft attitude :
* Pitch > +25° or < -13°
* Bank > 45°

I wonder on what consideration you base that assumption. On the basis of how a pitot tube 'works', it is not plausible at all. The BEA Update speaks of 'a sharp fall from about 275 kt to 60 knots in the speed displayed on the left PFD, then a few moments later on the ISIS'. The Air Caraibes Memo speaks of 'une diminution tres rapide de la CAS'. On the basis of the ACARS Fault message PROBE PITOT, BEA's Interim no.1 attributes the initiating event to 'a decrease of more than 30 kt in one second of the polled speed value'.

That would be me, having misread the documentation I had.

Again, it was just me - the "Airbus community" were the ones who kindly corrected me via PM.

But all indications suggest that the PF was commanding the elevator and by extension the THS to do just that - it didn't do it on it's own.

Not true. "What's it doing now" usually applies to modern autopilots (i.e. FMS/FMC), which are not restricted to FBW aircraft (the 757, 767, Classic and NG 737 and 744 have them for starters), nor indeed Airbus. As far as trim goes, all you need to have in the back of your mind regarding modes/laws is that in anything other than Direct Law and below, autotrim is active, so one needs to be wary of large, sustained inputs.

Really? How else am I to interpret at least 5 years of posts demanding that Airbus return to interconnected yokes and introduce a big red "Direct Law" button (as in the 777), not to mention continued belief in a conspiracy surrounding AF296 @ Habsheim?

But "tactile feedback" has been artificially driven in every major airliner designed since the late '60s, and indeed is computer-driven in the case of the 777 - so if you're in a situation where you don't trust the aircraft, who's to say that the feedback you're getting is accurate?

Also, the FBW computers coped just fine with the loss of airspeed information. The A/P and A/THR kicked out, and some protections were lost but ultimately the pilots had a controllable aircraft.

The problem is that "limits" (gums' suggested term) does not adequately describe what the system will do for you - for example, the Alpha Max/AoA protection will spool the engines to full thrust in the case of a sudden nose-up input - that's not a limit, it is - for want of a better term - a "protection". Also, your comment suggests that you believe some consider the existence of protections and their description as such might lead to a false sense of security - but from what I've learned from this thread, conscientious FBW Airbus pilots seem well aware of the limitations of said protections and the modes/situations in which they will not function.

Alpha-floor protection
 

Dozy;

While I agree with the entire post, just a minor semantic correction in your last paragraph to avoid confusion:

The protection that commands TO/GA (the EEC controls the spooling up) is named alpha-floor. IIRC it is activated in normal law when the AoA exceeds the corresponding threshold (between alpha-prot and alpha-max), sudden or not.

Hi Dozywannabe,

Correct. When manually flying I could "feel" the aircraft getting slow because the elevator would feel heavy in order to maintain altitude (until I manually trimmed the elevator). No so with AB FBW.

I wouldn't call that "coped" - I'd call that given up!
Even my old Boeing 707 A/P would have remained engaged, all that would have been required would have been manual thrust adjustment.

If I recall, those old 707/727 autopilots would also remain engaged with a complete hydraulic failure (A&B) even though they couldn't "fly" the aircraft from that point.

I think they put in a special red light for that.

First, you should try to put those events into the right sequence, then your questions should be answered by themselves.

Autotrim large change took place past 0210:51 : "The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight." [BEA]

Why would you put absolutely this aircraft out of pitch trim before this point, beside trying to fit something squared into your rounded mind?
If THS trim, for whatever reason, was something else than 3 deg NU before 0210:51, it reverted to this setting, then reached 13 deg NU between 0210:51 and 0211:50.

How does it fit now with your question?
Ask yourself.

Hi,

There is a subtle difference between the French and English about this conversation
In the French text is "indication" (singular form) and in the English version is "indications" .. ( plural form)
This is very different :eek:
I wonder how it's possible to make a difference of plural or singular form .. when a french tell "indication" as it's no difference for mark (voiced) the plural !!
So why make a difference between the versions :confused:

From Airbus Abnormal Procedures 2.05.80:
Drain Holes Free:
The IAS may fluctuate or drop quickly towards the sticker shaker speed. The IAS behavior depends on the condition of the pitot tube drain holes.
The sensed Pt drops quickly towards static pressure (Ps).

Thus far we have not had a serious UAS incident on the 777 to see what the latest generation of "artificial feel" will do when a significant data source is compromised.

I think you're misunderstanding the point I was making - the FBW system is distinct and separate from the Autopilot/FMC system. They pass data back and forth where necessary, but they are entirely different in terms of purpose, hardware and software. Now, as to what you're saying about old-school autopilots, IIRC in the 707 we're not talking much more than a wing leveller and altitude hold with a turn function. It didn't have an autothrottle or try to manage your speeds, ergo pitot information had no bearing on the design of the thing. Modern aircraft are very different in that respect and autopilot/FMS functionality much more all-encompassing.

Personally I think Airbus made the correct decision to disengage A/P upon confirmed ADR DISAGREE, and yet again we're back to Birgenair, where the A/P did continue to try flying the aircraft with blocked pitot and an erroneous overspeed warning. The result was that the aircraft had a very high pitch angle and it was only the massive amounts of thrust and a hard limit on FMC authority that kept the thing in the air. For all the stick Airbus come in for due to supposedly "encroaching on pilots' authority", their systems are designed to put the pilot in charge very early on in the failure sequence.

jcjeant,

I suppose you didn't notice the other difference, the Special Foreword To English Note?

To me, the noticeable element in this exchange is that the PNF acknowledges the PF's announcement, but at the same time corrects it, by adding the word 'valid'. IOW, there were indications but they were not considered valid.

Hi jcjeant
Agree... and it is not the only one.
The reference text is the French version, in any case, the English one being a hurried translation (as to your "why?").
Another point very badly translated, where Bearfoil's is driven to interpret it as a non-sense, is this one:
English: "The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb" -- here was also the error with angle-of-attack.
Bearfoilly's : "At PITCH +10, the a/c began to climb."
French : "L’assiette de l’avion augmente progressivement au-delà de 10 degrés et il prend une trajectoire ascendante."

In fact, the poor French syntaxe (in context) was badly translated in English, and Bearfoil's reading was, at the end, completely wrong ("only when pitch reached +10°, the aircraft started to climb").

What it means basically was :
"pitch attitude increased progressively (above +10°) while the aircraft trajectory was starting to climb".
As, of course, the climb did not start only when the pitch was above +10 (plane attitude changed smoothly), despite all those inertial forces involved.

Hi Dozy,
I'm not qualified on 777 - but I am led to believe Boeing have fitted the "big red button" - so that it would fly just like a very large 737. (with all the tactile feed back one could want aka Direct Law).

A question for the BEA
 

According to the Update, between 2:10:16 and 2:10:50 'the speed displayed on the left side increased sharply to 215 kt (Mach 0.68)'. At 2:11:06 the speed on the ISIS increased sharply towards 185 kt, and was then consistent with the other recorded speed.

If one of the PFD's had been switched to ADR3, would that be recorded on the DFDR?

I'm no expert on the 777, but as I understand it there are no "laws" to the system design akin to those of the Airbus system. Now - you've got your "tactile feedback", but it's computer controlled, based on the inputs the flight computers are receiving from the various sensor systems. Take those inputs away and I'm not sure what the back-driven system will do in response.

Certainly not.
Placed on the very same situation, but with hindsight about the outcome, most pilots, including any member of AF447 crew would certainly not make the same errors : basically, they would understand quickly that they will stall, or that they are already stalling, then certainly they will act properly to recover. Nonetheless, everything is pointing that this did not happen during this night.
Maybe, this very same scenario, played in the simulator (up to the point it could play it), with the same crew could have ended differently... who knows? Maybe the PF records during his sim checks was also near perfect? So the basic question of the investigation is to address the real security issues, not to find who seems "guilty" of what.
As for the level of civil responsability to be shared between the manufacturer, the company or the crew, honestly, this should be left to the court to decide. In the future, we'll be certainly allowed to comment its conclusion to the death. As a matter of fact, for me so far, any actor involved is possibly responsible of something wrong in the process leading to this catastrophe. But then, I need first to understand what it was exactly and why he was acting like that.


Hi HazelNuts,
Spot on!
Now that everything is showing that stuff involving AP & THS fantasy laws are not worth the bandwith, we should go back to the basics of Unreliable Airpseed Events... if we really want to understand what kind of situation was faced by AF447 crew, and possibly discuss what could have confused the PF and crew. PJ2, Chris Scott and few others have already tried (more than once) to bring back this thread on the cockpit confusion (hence, ergonomics and interface issues) but it looks much less sexy than talking about any Airbus Systems getting confused.

I guess that what is recorded is ADR1 & 3 airspeed channel, independently from where it is displayed (hence the choice of ADR3 instead of 2 as it could be displayed to Captain's PFD). Note, your typo about 215 kt (Mach 0.86)?!

I await the news of BEA next report as everyone does.

Perhaps it will clear up this confusion. When autopilot dropped out, the PF made immediate inputs, and heard the STALL Warning, two times.

What could the autoflight have done to get this aircraft to so obviously be nibbling at aerodynamic STALL? If dropping a/s reads, would the ap have increased power to such an extent that both engines were blazing away, and altitude still was dropping?

By definition, this is UPSET. At some point later, the onset of zoom climb qualifies technically as Loss of Control (LOC).

We hear the PF "I have the controls". So after the uncontrolled zoom climb starts, we will certainly hear PNF on the radio reporting "Out of...."

Will there be a MayDay in there as well? I believe we will hear at least one.

takata, you are wishful thinking. I know the feeling, and you have it.

Obviously you do not know any spoken French, or you wouldn't have posted this.
Spoken French tends to elide the last letter of most words.
In 99% of cases that's not a problem, since the meaning is obvious from context.
In this case it isn't... but please stop playing Sherlock Holmes, when you have no significant clues, and English is clearly not your mother tongue either.

Pot, meet kettle.

Seriously - takata's going on the evidence we have so far and you're still working on the supposition that the aircraft must have done something on it's own despite everything that we've been told - because, as you said before, you don't want to believe that the PF made a basic error and then compounded it.

We don't have anywhere enough information to make a call yet, but if you expect us to take your input seriously then you must also equally consider the possibility that - aside from the pitot issue - there was nothing wrong with the aircraft and that the upset was pilot-induced.

Doze. But which pilot?

Dazzle me with a theory of a Near STALL widebody at handoff. Because if you cannot, I will continue and suggest that the unreliable airspeeds were caused by the Rolling moment of a fast widebody in chop, and that the discrepant reads were made so by the airstream losing its integrity at the lower nose, while she mushed on full of gusto and KE. Not to mention plenty of NU. Hopefully BEA will fill the void they created between 2:08:07 and 2:10:05. Then I'll buy you an adult beverage of your choosing. My soul is ready, how's yours?

Lily White Auto?

Hi Christiaan,
You are of course totally right concerning the CVR transcript but let me complete the explanation for people who don't know that, in French, the pronounciation of such sentences would be phonetically exactly the same :
« je n’ai plus aucune indication » <=> « je n’ai plus aucune indication(s) »
« on n’a aucune indication qui soit valable » <=> « on n’a aucune indication(s) qui soi(en)t valable(s) »
Nonetheless, in both case, the plural form is incorrect ; the correct written form would be a singular "aucune indication" (not a single indication)... which, in turn, could also mean that they have lost "all indications"... go figure!!
This would be a problem with most transcript when spoken and written forms could have different meanings as this is really ambiguous to be sure what exactly "indication(s)" is aimed at.
It could be : "je n'ai plus aucune indication [de vitesse] => lost all speed indications, or anything else lacking on his instruments pannel as it is "undefined". This could be addressed with context as it could be about whatever "indications" they were talking about before, or after. Beside, I also believe that jcjeant is also fluently speaking his mother tongue.

bearfoil,

please bear in mind that the gap betwen Alpha = 2,5° (Cruise AoA) and Alpha = 4° (Stall Warning) is not really much if you are forcing the aircraft from level flight to a RoC of 7000fpm within seconds.

A Pull- Up sufficient to achieve this RoC in a short time would be easily sufficient to briefly exceed the STALL WARNING threshold (which is btw not the real stall AoA), especially when some turbulence contributes to it.

How's an a/c "nibbling at stall" supposed to do that 3000 ft climb?