w7, you seem a bit warped.

mm43

It does not say that in the BEA report, it is a "rumour".

The AOA values were being used by the A/C otherwise the Stall warnings would not have occurred. So the A/C would have sensed that it was at an AOA of greater than 30 and autotrim would have then been inhibited.

"We" cannot make any further "arguments" or state "causes" on this thread until the "FULL" BEA report is published.

iceman50In the meantime I'll live with the "rumour", and I'm certainly not going to die for it.:}

Now imagine you are pushing the nose down to recover the aircraft from the stall, and airspeeds becomes valid, and you get to 30 degrees nose low, and abnormal attitude law wakes up!
Might not that interfere with continued trimming nose down automatically and the recovery?

Better to crank the trim down manually to avoid any uncertainty, I think.

Quoting bubbers44:-

I suspect, bubbers44, that the new (and IMO wrong) procedure was introduced because reduced vertical separation was also approved about that time? That factor might also have made flightcrews very nervous about 'sacrificing' any height in an upset?

If they had done that soon enough and initially got rid of the 15° pitch attitude, the AoA would have been approx 20°. Application of a bit of thrust while still continuing to take the nose below the horizon would have quickly brought the AoA into the CL regime. The problem would be to avoid an over (-)rotate and risking another high AoA trying to pull out.

Might be a subject worth running through a spreadsheet and plotting change of AoA over time versus increase of airspeed over the same time.:cool:

BOAC
wallybird - I would ask you to carefully read both the current and old threads on this topic? Your fixation on 'thunderstorms' is out of place based on what we are told by BEA. There is also no firm 'evidence' of any 'thunderstorms' on their route.

There is no evidence that they 'penetrated' or flew near a 'thunderstorm'.

It is shown (in the reports) that their 'choice' to deviate to the west proved to be a better one than other aircraft which went to the east.

BOAC

As a matter of semantics, and my "fixation" on thunderstorms, and no "evidence" of thunderstorms, then just what are they deviating around?

If not thunderstorms?

w7 - one more go. See #2103. They were deviating around an area of increased instability in the ITCZ. It may or may not have been a 'thunderstorm' but there is no indication that it was. As I quoted, all the a/c that deviated the other way (East) had a rough ride.

I am detecting a general increase in 'urban legend' again that in general the PF made constant 'nose-up' inputs. This was indeed the report's conclusion for the top of the zoom and the early part of the (stalled) descent, but was NOT the conclusion for the zoom itself. Xcitation's 'bullet points' (last quote in #2096) taken from page 3 of the May report are misleading and are perhaps due to translation problems in that they imply that the inputs were mainly nose up 'from A/P disconnect'. BEA have not produced any substantiating evidence of this. Regarding the 'zoom' they say:

"The PF made nose-down control inputs and alternately left and right roll inputs."

The climb is still unexplained.

Just storms? Storms without thunders&lightning?

Remember that on the bus a nose-up input creates pitch-up demand that stays until countered by same amount of nose-down demand. PF didn't have to make constant nose-up input for a/c to keep climbing - short nose-up input will do it. The later nose-down inputs reduced the pitch and slowed the climb but not enough to get the nose down to get the speed back.

If something got jammed there would have been clear traces of such thing in FDR. Similarly if elevator went away then, while active jack could conceivably stay at it's place, the other (redundant one) working in "damping mode" would've got "desynchronized" from the primary one as there would have been no surface to push/pull it. That should be clear on FDR.


RWA:

Why trim didn't change during those nose down actions has been discussed already. There are 2 primary options...
1. Plane went into abnormal attitude law (but there is no tip about that in any BEA statements)
2. Inputs were not significant enough to cause trim change. Some AB engineer or someone other knowing details of A330/A340 control systems could shed more light on that, but nowhere it's said that trim change starts instantly after pitch input. It's perfectly conceivable (and in fact reasonable) that trim starts to change only after stick input is persistent. Note also that it took about 1 minute to get trim from 3 to 13 deg, so one should expect to wait another minute to get it back to 3 by automatic action. If one needs trim to change faster one does have that trim wheel in front of oneself.


Wrt. plenty of time to get that bird out of the fall while at FL100. This was not Cessna 172, this was AF447 heavy. 200tonne bird. Heavy airplanes sometimes get recovered from "falling out of the sky" upset, but it's just that: sometimes.

Back of envelope calculation shows that if they were at -30deg flightpath while at FL100 then maybe they could pull up. 2.5g pullup from -30 flightpath at 200kts true speed takes about 6000ft altitude, but add to that an altitude lost to first regain unstalled AoA (nose down to about -15deg from about +15deg -- it could not happen instantly, and they were falling at ~10000fpm or ~50m/s thus loosing about 150ft every second) could that plane pitch as much while loosing no more that 4000ft? Maybe...
But if they already were at -45deg flightpath (the flightpath angle when they hit the water) they stood no chance at FL100. Pullup itself would take ~8500ft, but pitching down 200t bird by 45deg (from ~+15 down to ~-30) while loosing only 1500ft? I don't see that.

In the middle of an ocean? Where the traffic is relatively small, and there are significantly horizonally separated airways for the traffic going NE and for that going SW, and where are no planes to be vertically separated from from FL100 up to FL600? Those guys know perfectly well that they can divert by significant amount, they can change level, etc. without any risk of collision.

sebaska

Thanks for the input. There is a possibility that the THS could have become inop and the sensors not suss it. It is a long story, and I'll start by noting the PF's Nose down inputs prior to STALL STALL, at which time he evidently relented, and either held neutral, or back ss.

Nose Down. Again, Nose Down. The airplane is not dropping her nose. (This at the post apogee fall off). Again Nose Down, now the STALL WRN.

Each time the PF inputs some NOSE DOWN, the a/c does the opposite, she starts to nose up, and slows. Finally, with the STALL WARNING, PF is baffled (wouldn't anyone be?)

Under what circumstances would the nose rise with down elevator? Just a few. For one, if, instead of commanding PITCH, the elevators were trimming the THS. How is that possible? Only if the THS had lost integrity with the mount, specifically the jackscrew. Had this occurred, the THS elevator system would perform as an all flying tail, a stabilator.

For the elevators to work in PITCH, the THS must remain resistant to them, that is why it does not trim at elevator deflection speed.

Look, this is but one possibility, and I expect it to be ignored or dismissed, but since it is possible, I think it deserves a look.

See BOAC #2121 re: the climb, and consider how the climb could have been extreme due PF input of NOSE DOWN. The climb is the key. Still looking at mechanicals, and FC.

Bear, I don't have enough info to answer your "?" about what's mounted wear with any confidence. Someone who flies or fixes the A330 might.
As to this:
bear, I am confused as to what you are saying. If you move the elevator, you command pitch to one degree or another. What appears to happen, unless in direct law or manual control, is that initial pitch controls are manifested in elevator movement, which is followed up by trim to the THS to put the loads in equilibrium for the new state. An elevator movement up or down will change the shape of the combined airfoil (THS/elevator) any time you do it. Under normal operations, the THS will naturally lag behind the elevator input for any control position change.

Using the trim wheel short circuits that. I understand based on a few posters here having described such an event, that it makes the control via trim wheel less "smooth" for the pilot flying compared to what he is used to.

To suggest that the elevators only trim the THS seems to me a desicription of how the combined system (elevator and THS) does not work. That may be my fault in part, as some pages back I raised the ideas of primary and secondary flight controls, and trim functions. (Maybe at Tech Log thread)

From the block diagram, the change induced by elevator control informs the system of a need, or not, to adjust THS trim to better position that flight control surface for best AoA for desired performance.

If anything got stuck, or was operating in reduced authority, there may or may not have been an audit trail ... but given how much info IS provided to the system via various wires and circuits, I'd be more inclined to believe that a jackscrew failure (or analogous THS positioning machine failure) would trigger either an alert or an ACARS message ... which to date BEA have not released as being the case.

Whatever remains of the tail flight control surface hardware after the slow descent to the depths would be nice to have examined, if only to consider the null hypothesis as part of the process of elimination.

Forensic analysis may be imperfect for a part collecting various deep ocean residue for a couple of years, but a good estimation could be made.

Hi Bear,
I really wonder if you don't get a different report than ours. There is actually only two nose-down imputs reported in the whole BEA note:
The first mentions of ND is obviously reducing the vertical speed; consequently, I can't find anywhere that "the aircraft does the opposite, she starts to nose up, and slows".
The second mentions of ND is obviously reducing the angle of attack; consequently (again), I can't find anywhere that "the aircraft does the opposite, she starts to nose up, and slows".

The obvious issue isn't about what the PF/aircraft did but, quite frankly, about how you are reading this report with such a personal interpretation of a couple of "facts".

Following your understanding of "facts", at this point, this aircraft is entering a near vertical dive, don't you think?

Hi,

About THS .. I will repeat myself :)
Be sure that Airbus Industrie have already simulated many parts of the situations where AF447 was involved
They certainly know perfectly if the plane is recoverable with parameters as attitude .. altitude and speed .. and position of the THS at 13° up of AF447
And those tests can (maybe) be performed by some members (A330 pilots) of this forum
Apparently no one made it so far.

Lonewolf50

Offered only insofar as to what could explain a Pilot pulling back when Confronted with STALL warn or actual Stall.

The elevators change the Pitch of the A/C acting through the Horizontal Stabiliser. This would not happen if the HS was free to move where the elevators put it. 'eg'. the elevators would change the AoA of the HS rather than the a/c.

So IF the Horizontal Stabiliser was not connected to its jackscrew (which "Positions it internally"), it would deflect to whichever angle the elevators put it. This would in turn change the Pitch of the a/c, but opposite to ss input. Down elevator pushes the trailing edge of the HS UP, climbing the a/c.

I don't wish to make any claim re:447. AGAIN, I think it is worth a look, if only to better understand the way the a/c functions.

The PF WAS making ND input, and the STALL WARN tripped. It is logical (though perhaps not correct in this case) to assume the effect of his command was counter to his expectation (And to ours).

So, in the failure case (separated jackscrew), the a/c is reacting to the THS' position, which is commanded by "trimming" elevators, rather than "commanding" elevators. Simply drop a step in the arrangement of conventional trim tab, elevator, and HS. Eliminate the HS, and what is left, is the arrangement on all THS flying a/c!

Aside.... BEA say "..and remained in that position to impact..." They are speaking of the THS, planted at 13. What holds it there? Perhaps not the Pilot's NU, perhaps not Hydraulics, active or lock. Perhaps airflow.

sebaska. I believe the two motors are positioned on the same jack. Perhaps not.

I'm sure that such severe misbehaviour would stand out in FDR recording. THS diconnected from its jack would be banging up and down dependent on elevators position. This would be accompanied with violent pitch changes and high g loads. If the whole thing would not separate almost immediately. Then how both left and right THS would fail at the same time? Or is there just one jack for both of them?


A I understand each elevator has two jacks (It has been described here recently). Normally one of those is active while the other is in "damping mode" (i.e. gets pulled/pushed instead of pushing/pulling).
THS has one jack with two motors. But I understand it's one for each side. But i could be wrong.

I submit that such misbehaviour did reach the DFDR, and we are seeing it, per BEA.

Do not be too quick to dismiss the THS/Elevator system as wild, with great Pitch excursions. On the contrary, many aircraft are controlled w/o jacks on the HS. With articulating elevators and a freely pivoting HS, Pitch is quite manageable, and all that is necessary is a program that can retain precise Trim for the AoA of the assembly as a whole.

The problem would be in the Flight management from the cockpit. Immediately, Pitch would reverse, but control could be maintained, even good control, and Trim. It would take a brilliant pilot, similar to the rare excursions experienced by a PF taking off with elevators reversed. Ab Initio, ad lib, as it were.

Here, I am looking for a possibility that would explain not only unusual behaviour on the part of PF, but also the aircraft.

ACARS was a LEAK. BEA affirmed what was made public. They even explained it. There was that GAP, however. And no further comment from the authority.

I have been doubtful and suspicious of ACARS as leaked from the git. No way of knowing if all of ACARS exists, is known by BEA, or some other.

for now, I am looking for reasons to support any theory that embraces such aberrant behaviour, as reported.

Thanks for taking the time to respond.

Now, some HF. One or the other or both of the cockpit crew wanted the Captain's presence, NOW. It could not have been UAS, Weather, or any of the normal suspects, imho.

Some one removed his bars (figuratively), placed them on the deck, and called for help from Captain. It is not in the nature of Pilots to do that, unless the situation is irrecoverable. Such as, an aircraft that is behaving wildly, unpredictably, and deadly.

@Bearfoil
IMHO the suggested catastrophic failure of the THS is over-reaching. Such a failure of control surface would result in well documented "smoking gun" errors. Furthermore the a/c response to control inputs appears to have been reasonable considering the stall condition and weather. For a brief description of THS check out Section 5 the A330 brochure here.

@Wallybird7
Thunder and lightning comments are IMHO of less merit. The primary threat here is convection (up/down draft, shearing resulting in excessive strain to the airframe and disruption to flight path/attitude) and precipitation (causing icing on the airframe and affecting thrust). Lightning can occur many miles away from the convective storm and can be independent event. Lightning strike on a/c is a very rare and generally benign event.

I submit that to some extent, any conjecture is true to your definiton of "over-reaching". BEA have not offered an explanation of any kind. Have you noted that? Likewise no theory. They have allowed (encouraged?) speculation. The alternative is "Wait for the final report".

I thought we were past that. I think any attempt to give the discussion "guidelines" in the absence of any attempt to provide reasonably complete data (BEA), is presumptuous. If my posts are bizarre, upsetting, etc. I rely on the mods to edit them. I have always welcomed mods input or editing; I am here by 'invitation' only. I have even edited myself, or banned me temporarily. I have utmost respect for all who post here, everyone.

I am unable to put together even such as is found here, except to take in that which is accomplished for me.

Over my Head?. Boy Howdy.