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AF 447 Thread No. 5

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AF 447 Thread No. 5

Old 12th Jul 2011, 12:53
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CONF iture

Thanks for the CG explanation. That was something I was trying to understand, and I missed it in your previous posts.
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Old 12th Jul 2011, 13:45
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Cool

Hi,

takata
If you were not such a , you would understand that anybody, including pilots, may be induced in error, even by serious Air France or Airbus shortcomings. So first step is to understand what goes wrong.
Stop trolling, please.
takata I will tell you what goes wrong and will be wrong in the next decades
During the next ten to twenty years .. forecasts show that companies will grow very quickly (especially those of the Persian Gulf region)
The demand for pilots and other personnel will be huge
The consequences of these expansions will be reduced formation and training while the aircraft are becoming more complicated
Ironic indeed ....
The result of all this is easy to predict
The planes will start dropping like flies killed by insecticide
This is what's wrong (and already present)

serious Air France
Serious .. Air France ? ... I disagree (see audit results and stats)
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Old 12th Jul 2011, 13:50
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So...

Have some airlines really been training NU inputs and HITHRUST for stall recoveries when this seems to produce further (and usually unwanted) NU trimming?

Has there really been a history of excessive ND Stall recoveries creating ground proximity incidents - forcing this re-evaluatiobn of traditional stall recovery methods?

Or... has this type of recovery procedure stemmed from 'The Devil makes work for Idle Hands'..

e.g there has been no specific events creating a need for high power, NU recovereies, other than that modern fan-engined aircraft are (nominally) capable of such recoveries.
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Old 12th Jul 2011, 14:02
  #144 (permalink)  
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One area of confusion in my mind Chris S may be able to clear up. What I think I see here and from BEA is that the THS did not move from its cruise angle until the top of the zoom climb? Given that it is supposed that PF held a nose-up demand most of the way up, why not? There must have been a good 40 seconds or more of 'demand'.
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Old 12th Jul 2011, 14:13
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BOAC: More 'imaginative thinking?'....

One area of confusion in my mind Chris S may be able to clear up. What I think I see here and from BEA is that the THS did not move from its cruise angle until the top of the zoom climb? Given that it is supposed that PF held a nose-up demand most of the way up, why not? There must have been a good 40 seconds or more of 'demand'.
Where the heck do you SEE that written?

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. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).

At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]".

The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left. The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.

From 2 h 10 min 50, the PNF tried several times to call the Captain back.
So where are the "held nose up inputs"??? It's just NOT there. Why invent this?

The comment regarding the THS comes later. Read the note.
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Old 12th Jul 2011, 14:19
  #146 (permalink)  
 
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Takata and others, Zorin_75 asked a very pertinent question about the persistent fixation on the autotrim. Why IS everybody so fixated on it?

Surely nobody here thinks that turning autotrim off or simply coupling the elevator to the stick would have made a difference, I hope. The elevator jack screw runs too slowly for the pilot to use it for primary control. So the dual action, a quick action partial solution and a chugging along slower action is derived as the best way to handle it all. But the real problem is the full to the stops NU input that persisted until the plane was in an attitude from which recovery was problematic.

Hadn't it gotten into a condition such that the elevator authority was sharply limited by it's being fully stalled? By the time they made the final ND input there was no way to pull out of their stall. (I mentioned the thought of breaking out of it with unequal thrust to introduce an asymmetry to break out of the stable stall. And, yes, I can see no sane pilot wanting to do that. I vaguely wonder if it could have led to breaking the stall before it hit.)

The plane was crashed, essentially, by the persistent NU command not the THS. I've talked about training to use the trim wheels. But on thinking it over and too vaguely remembering the stall characteristics of the aircraft vis a vis position of the elevator I suspect all the elevator would do is slightly modify the NU forces on the aircraft. Are you worrying about something that appears to make a huge difference yet makes no real difference at all when the AOA of the aircraft is some 60 degrees?

Just askin....
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Old 12th Jul 2011, 14:24
  #147 (permalink)  
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Originally Posted by GY
The comment regarding the THS comes later. Read the note.
- Hmm I thought that is what I posted, never mind! Specsavers?

The 'Nose-up demand' certainly does not fit with my 'understanding' of events (which again you MIGHT have noticed (Specsavers?)) but does appear frequently here as a mantra so I was looking to see if it was possible, actually. I'm sure there are those here who think PF made the a/c climb, or am I imagining that? Anyone own up or can we eliminate that 'theory??

JD-EE - indeed , and I have discussed this with my tame AB expert - we both agree that after 40 + years of 'doing aviation' neither of us had ever contemplated a situation where a tailplane could be so stalled that a nose down elevator command could be a nose up.
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Old 12th Jul 2011, 14:55
  #148 (permalink)  
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JD-EE Great minds think alike, wish mine were one. There is very little to go on from the investigators, and that partially explains the breadth of comment here re: the most important phase of flight. Induction of Fail.

Too many shiny objects to harrumph about, and the meat of the matter in abject darkness. For ten seconds before A/P drop, and ten after, 447's fate was being sealed.

Either one believes the PF (and auto before him), created the stage for an absurd and fatal climb, or one believes they did not, and the hand of Satan slapped them silly at 2:10:00.

In between, (and in the belly of the only important data, that which is missing), this flight was lost.

Who is to say the airframe did NOT actually STALL after the very first WRN? Was the fatal parabola initiated at the beginning of ACARS, or some time before?

Maybe it's me, but I sense that most here assign controlled flight to this a/c until the apogee of the zoom. By definition, one thinks, LOC happened at the "the aircraft began to climb...." Whether or not the PF "caused" the event, is not as important as what caused the event that "caused the event".

Snapshot thinking? a/p dropped for a reason, so in strict terms, can one absolve the a/c?

Of course not. This was a continuum, and I truly believe that when the data is complete, and in the fullness of time, there will be still some adversarial and parochial gripes to be had.

In the meantime, Shadow is most intriguing. With the chronic and slow loss of "Read Speed", wouldn't the a/c Trim Power UP and NU also?

Why hasn't anyone addressed what the a/c might do with the need to "Maintain Speed and Altitude" when in autoflight? Because BEA have ignored it? It is "off limits"?

It occurs to this nomex clad cattle prod wielding ex-pilot that some one should at least attempt it?

Could the a/c have been at max power and NU somewhat at drop? Enough nose up to chirp the STALL and Cricket at 'one' NU left input?

The precise data in this bracket of unaddressed time is seductive.....
 
Old 12th Jul 2011, 15:04
  #149 (permalink)  
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BOAC;
What I think I see here and from BEA is that the THS did not move from its cruise angle until the top of the zoom climb? Given that it is supposed that PF held a nose-up demand most of the way up, why not? There must have been a good 40 seconds or more of 'demand'.
While it may be an impression on the part of some, the reference for any of this is not here but the BEA Update, and it does not state that NU SS was held most of the way up. It states that after the plane started to climb the PF made ND control inputs and alternately left hand right roll inputs.

We see a this best in the Excel graph which A33Zab provided, (post #691) in the previous thread - He has shown, and I think accurately so, that the THS does not begin to move from its 3° position until the aircraft is almost at the apogee. The SS was not NU most of the way up but was NU briefly which initiated the pitch-up then ND which began a slight level-off though the aircraft kept climbing. The stall warning occurred @02:10:51 according to A33Zab's graph and a continuous NU SS and application of TOGA thrust is coincidental with that event, and the THS begins to roll towards NU. The aircraft actually stalls at about 02:11 as the descent begins, while the SS is continuously held in the NU position with the pitch attitude at 16deg and thrust set at TOGA. According to the graph, the THS reaches 13NU at around 35,000ft in the descent at about the same time the captain enters the cockpit.

I suspect that while the THS position moves to continuously neutralize elevator forces just as any trim does, the movement is a "follow-up", the rate of change being governed by the pitch basic control loop which has a number of discrete inputs but primarily the sidesticks and the accelerometers. A long discussion has already taken place on Nz law and trimming to 1gee. Manual control of the THS can be taken any time by rolling the trim wheel forward or back. The following is a schematic of the THS general arrangement:




I'm sure there are those here who think PF made the a/c climb, or am I imagining that? Anyone own up or can we eliminate that 'theory??
Again, the BEA Update states that the PF made "a left nose-up input". It isn't a "theory". Back-stick was later held during the stall, and for 30 seconds during the descent. Also, ND SS was briefly held after the initial pitch-up and briefly again during the descent. Knowledge of all other times will have to wait for the next Interim Report.

Last edited by PJ2; 12th Jul 2011 at 15:19.
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Old 12th Jul 2011, 15:10
  #150 (permalink)  
 
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BOAC, I "think" what I meant was that a ND input would still come out NU and an NU input would also be an NU input. Whether they reversed as gums has said can happen, I don't know. I don't THINK the charts showed a full reversal even to the level that ND was more NU than an NU input. All I remember is that it looked like both resulted in NU type motion.

And I think rudderrat hit the nail on the head for why the PF pulled nose up even though he was above FL100. The big (well trained) print buried in the FCOM called for TOGA and NU. (If it really is presented as quoted or as I remember seeing it in the past with smaller print for the above FL100 part it was presented poorly. It should break right at the beginning for above FL100 and below FL100 so the decision is made early and then procedure can be followed logically and linearly. (And thank you thank you for that post rudderrat.)
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Old 12th Jul 2011, 15:15
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bearfoil, logically the airspeed loss cannot be slow. If it was the heaters would be effective. For the icing to happen it would have to take place very quickly in a fashion to overrun the heater's capacity on an instantaneous or nearly instantaneous basis.

It took awhile for that coin to drop, too. The original statement bothered me. I just figured out why.
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Old 12th Jul 2011, 15:18
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PJ2, would the original NU command be a persistent, albeit moderate, command or would be a short one to establish the increased AoA and then returned to neutral? I got the impression from choices of wording that the original NU command was transient.
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Old 12th Jul 2011, 15:22
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JD-EE, transient and then neutral, then with slight ND, then NU more continuously, is my impression.
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Old 12th Jul 2011, 15:34
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PJ - that fits with my understanding, so where the *** does 7000fpm come from? That is one hell of a r o c for a 'transient nose-up followed by nose down'. To take your words "but was NU briefly which initiated the pitch-up" - I am still having difficulty in envisaging 7000fpm in a 200t a/c at FL350 from that - are you content? I am, by the way, quite aware of what BEA are saying about when the THS moved and I have assumed it was to compensate for the increasing NU demand on the elevator from PF's 'stall recovery'.
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Old 12th Jul 2011, 15:39
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Hi JD-EE,
Originally Posted by JD-EE
And I think rudderrat hit the nail on the head for why the PF pulled nose up even though he was above FL100. The big (well trained) print buried in the FCOM called for TOGA and NU. (If it really is presented as quoted or as I remember seeing it in the past with smaller print for the above FL100 part it was presented poorly. It should break right at the beginning for above FL100 and below FL100 so the decision is made early and then procedure can be followed logically and linearly. (And thank you thank you for that post rudderrat.)
Respectfully, the procedure recalled by rudderrat is to apply Nose-Down (reduce pitch attitude) at the same time as TOGA... while, in our case, the pilot apply Nose-Up (increase pitch attitude) at the same time as TOGA... Then, this is quite hard to conclude that he was following this procedure!

This is what (below) he is talking about; you may also notice the relevant part about the aural stall warning sounding at "altitude":
"... it warms that the aicraft is approaching the angle-of-attack for the onset of buffet. To recover, the pilot must relax the back pressure on the sidestick..."



Last edited by takata; 12th Jul 2011 at 15:56.
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Old 12th Jul 2011, 15:56
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takata, that is correct if you are not reading in a hurry.

This is what rudderrat quoted:

"An aural "STALL, STALL, STALL" warning sounds at low speeds. Upon hearing it, the pilot must return to the normal operating speeds by taking conventional actions with the controls:
Thrust Levers...TOGA
At the same time:
Pitch Attitude...Reduce
Bank Angle...Roll Wings Level"
So this is what the pilot was doing. He never got down to the other part.
The next bit reads "Thrust/Pitch .... CL/5degs Above FL 100"
And note that this is from the FCOM not the QRH. Rudderrat remarked that in June 2009 the QRH had nothing to say about stall....

Is what you quoted from 2009 or a current manual. It was noted in some incarnation of this thread that the procedures had been altered and something had been added to the QRH regarding stalls.
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Old 12th Jul 2011, 16:05
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Assuming the PF was sane and coherent, (I do), NU would be input to counterract ND, or a descent of some sort. After his correction, neutral stick. If the slight rotation he commanded (NU) then appeared too much, he would input ND (he did). Wait, that did not work, she still climbs. A bit more ND, and what is that pesky Roll? More Roll? compensated. More Roll still? and continued Climb? Increasing climb rate?? More ND and More.

BEA tells the Truth, and I see it this way. By BEA's data alone, where is PF screwing anyone's pooch on the way up? On the way down, with gobs of AoA, the Pitch can reverse with a Stalled Tail Plane. Remember this is not so much a Tail as a variable incidence wing.

JD-EE. Chronic and slow enough to allow the TailPlane to trim for it. And engines to develop max thrust (or close to it).
 
Old 12th Jul 2011, 16:20
  #158 (permalink)  
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BOAC - we don't know the details of the SS movement so it isn't possible to correlate such movement with rate of climb. The aircraft would have had a nominal pitch attitude of around 2.8deg roughly - SS movement aft of 3 - 4cm (previously said 2 - 3cm), as measured at the top of the stick would produce an enormous but clearly brief rate of climb of the kind we see here - it would be the equivalent I suspect, of about a six-inch rearward movement of the control column on the B737, just to try to equate a sense of the large changes involved in pitch and climb.

"Two-hundred tonnes" I believe is immaterial here as the wings produce commensurate lift for the design. It is a matter of mass, momentum and available energy (far more than 200T worth) from the wings at the initial CAS, which, given the eventual pitch attitude of 15deg clearly would be quickly unsustainable but in the short term, achievable. The BEA Update states that the VSI reduced to 700fpm and it is easy to understand/imagine the ballistic trajectory which resulted prior to the start of the descent.

Aside from my original thoughts of responding to the UAS drill instead of "doing nothing" while getting out the QRH for pitch-and-power settings, this almost looks like this was a reversion to original training where the approach to the stall is taught in transition or initial courses at lower altitudes in which the goals have traditionally been minimum loss of altitude, (much discussed in earlier threads) and "powering out of the stall" using TOGA thrust. The initial pitch attitude just may be some over-controlling which resulted in checking the stick forward a bit before responding again to the stall warning with back-stick, (driving the THS up, as we see). As I mentioned a number of times before, once the aircraft departed level flight, the "knowns and cues" for stable, level flight were gone and situational awareness, (what pitch? what power?) became problematic. The simulator exercise required a lot of nose down and I don't recall seeing what the THS actually did during the exercise and didn't look at the THS indiction. The descent rate was 7500fpm and the stick had to be held full forward. This was a stall from a pitch-up and the PFD looked like this in the recovery:


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Old 12th Jul 2011, 16:43
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Originally Posted by JD-EE
So this is what the pilot was doing. He never got down to the other part.
Obviously, it isn't what the pilot was doing as he applied sustained nose-up, no? Otherwise, every single procedure calling for TOGA would fit with your definition of what he was doing. It would better fit with WINDSHEAR procedure in this case.
As the BEA did not provide any hint about any manual change of N1 rate during the first part of the climb (between 0210:05 and 0210:50), we may also think that the PF realised he climbed to 37,500 ft without adding any thrust from 35,000 ft and was trying to compensate for it. Maximum N1 is about 115%, but I don't know if such level could be reached in current conditions... at 35,000 ft, he was flying at about 95% N1.
Originally Posted by JD-EE
And note that this is from the FCOM not the QRH. Rudderrat remarked that in June 2009 the QRH had nothing to say about stall....
Is what you quoted from 2009 or a current manual. It was noted in some incarnation of this thread that the procedures had been altered and something had been added to the QRH regarding stalls.
This FCOM quote is dated March 2003 (Rev 18). Most people did not look at the FCOM 3 which is providing "supplementary techniques" (3.04.27).
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Old 12th Jul 2011, 16:50
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PJ2 "Once the aircraft 'departed' level flight". Other than level is not a 'departure', yes? Departure means a loss of aerodynamic flight, no?

Per BEA, how is the a/c known to be at S/L flight at dropout? PF obviously corrected for a ND or descent (or overspeed) of some sort, right? Assuming his NU input was a stupid or inadvertent blunder is not supported by the Data, surely? He could have pulled NU to correct an overspeed whilst NU already, yes? This would fit with such an unusual roc so quickly. Would the a/p have trimmed the NU to control speed with added power it had applied to "correct" a "slow" IAS due particle ICE plugging?

I do not mean to nitpick here, but your commentary is the Gold Standard here, and am I missing your drift? Maneuvering to retreat from STALL WARNING is not a STALL recovery, that is why the book allows for back pressure. I cannot find where it allows NU? Only back pressure, to minimize altitude loss? In fact, it advises lowering Pitch at this point, which is not the same as ND. This is parsable, but I read it as "non-negative" 'Target Pitch', to maintain altitude. I find nowhere a direction for PITCH UP.

Situational Awareness is the key, of course. Strictly speaking, loss of autopilot, for whatever reason, is a loss of SA machine-wise? Whether for UAS or inability to maintain programmed flight envelope limits?
 

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