Lyman

HazelNuts39

I recently posted that the THS remained parked at three degrees from the drop of autopilot to the threshold of STALL. It then moved NOSE UP to 13 degrees, where it remained...

Similarly, " The trimmable horizontal stabilizer (THS) began a nose-up movement and moved from 3 to 13 degrees pitch-up in about 1 minute and remained in the latter position until the end of the flight." ..(FINAL)

You posted that the THS had articulated during the climb. Referencing a document not in the Final Report, it was implied the HS was trimming...

Which is correct?

At 2:10:51, when the THS started its NU trim, the pilot was about to run out of elevator, and would have Stalled. With the extra degree/6 second rate of NU input, this creates an authority for Nose Up he had lacked on the way up. Does this create a problem?

Does there not appear to be some evidence the THS created a condition conducive to retention of NU into and through the STALL?

Why did the THS not follow the PILOTS NU in the climb? I asked before, no one proposed an answer.

What operational spec rules the inhibition of THS whilst climbing, and just at the payoff to STALL, it re-enters the flight path to keep NU?

DOZY, still waiting for a response from you re: what initiation and end rate did you observe in the descent with your ND full? Did the THS move at all? See, the way you phrase it, the THS did not move ND, but was fully ND after eight seconds. Can you clarify?

HazelNuts39

I directed you to a BEA graph that clearly shows small THS movements between A/P disconnect and 02:10:51, both in the FDR trace and the simulation trace.
At 2:10:51 the elevator was at 1.6 degrees NU. It did not exceed 10 degrees NU until 02:11:37 and reached 30 degrees (full travel) at 02:11:45.
It did, see above.

mike-wsm

Yes, Hazelnuts, that is what happened, ten degrees in a minute, putting the airframe in a condition which defied efforts at recovery. But why did the electronics not limit the speed of movement to a tenth or a hundredth of this? I cannot see any need for a faster response when at high altitude and cruising. Had the movement rate been limited then recovery might have been possible. Hal could have let Dave waggle the little bits without moving the big bits.

infrequentflyer789

What efforts at recovery ? Stall was, it appears, never diagnosed, so how was stall recovery "defied" ?

In fact, PF's response (if it was that, and not mere coincidence) to stall warning was toga and pull. [That is also not an airbus thing - see recent Colgan (Q400) and Ethiopian (737) crew actions].

At high altitude and cruising with all systems normal, HAL would indeed have limited things. Trouble is that in this case HAL has concluded the air data (from all units) is invalid.

HAL effectively removed any such limits because it was no longer sure whether it was "high altitude and cruising" or not. It handed control, and the job of figuring where the plane was and what it was doing, to the pilots to use real intelligence (which "HAL" in this case does _not_ have) to figure out. They failed at that.

CONF iture

In the eventuality he was going to forget, we put the autotrim ... just in case.
Anything else studi ?

CONF iture

Then where are those plenty of posters (including line pilots) who say you're not ?

Lyman

HazelNuts39

Hi HN. So my question is, (I could not find the new graph, would you consider posting it?), the THS was at three degrees (-) at 2:10:51. This after a climb of 3000 feet, and mostly NU elevator. The THS was also at three degrees at 2:10:05, I am confused as to where and when the THS moved NU then back to three degrees?

I grant there may be movement that is not discerned on the BEA trace provided In the report, due to lack of resolution?

I am left with a dearth of information relative to the operation of this HS. My concern is that at 2:10:58, with the advent of deterrent Buffet, the pilot had elevators only, and at the Stall he had elevators fully deflected with a THS at 13 degrees.....

I make no conclusion re: handling by this pilot, but it seems that at a critical time, his PITCH inputs may have grown by a large factor, and possibly without him knowing it (sic) such that any ND he made would not have accommodated
the newly acquired TRIM.

HazelNuts39

Lyman,

The new graph can be downloaded from the BEA site, page AF447 Final Report. Scroll down to "High resolution report images" and look for "Figure 64".
It is discernible on the high-resolution graph I referred you to, other graphs may lack the necessary resolution. My read of the 'simulation' THS trace is shown below:

roulishollandais

Let me put my hat of computer guy :

On alternate 2B law, pilots have to fly the derivate of the pitch on longitudinal axis d(AoA(t))/dt , and Bank angle B(t) non derivated on the lateral axis ! So Bonin did "mayonaise".

Compare that to that situation : If some famous pilot asks me to design the control system so that when putting his stick mayonnaise in the oscilloscop, we can discover he "pitched" J.S.BACH Toccata et Fugue BWV 565 in minor D, and rolled Diango Rheinardt playing "les Yeux Noirs", Oh yes it would be possible ! But I would say him "NO".

But Airbus and their pilot and non pilot designers accepted that crazy myriad "alternate(s)" deal. So much fun !

mike-wsm

infrequentflyer

Many thanks for your kind explanation.

bubbers44

Bonin killed all those people because he shouldn't have been signed off as an FO. The PNF didn't have the guts to take over. The captain got there so late he couldn't believe what they had done and never seen it before. Just remember, automation is our friend, just ask Airbus.

TTex600

Bubbers44, I just can't let you say that Bonin killed off all those people because he shouldn't have been signed off as an FO. I would agree that the airline and the French Regulatory Agency killed off all those people because they signed off Bonin and Robert as FO's.

It isn't fair to blame the pilots for the lack of training they received. In this airplane, you truly don't know what you don't know. The FCOMs are not adequate to reach a level of true understanding, a situation which leaves it up to the training department pass along a great deal of information.

There are numerous links on this site to the Airbus Flight crew training manuals. Those FCTM's include info not included in the FCOMs. I had never seen a FCTM until I clicked a link on this very site. That's the best example I can give to illustrate that all info is not available to the trainee.

jcjeant

Indeed ....
English final report page 211
This BEA remark is ironic (physics of flight at high altitude) when we know that during a flight from point A to point B far the largest flight time is going at high altitude
And it is mainly the physics of this phase of flight which is not sufficiently explained or simulated .......

Ian W

Dozywannabe
My understanding as a fully paid up SLF with bus driver friends, is that the THS movement is not commanded in automatic operation, but operates to reduce the stress on the elevator hinges so it motors to the position that requires no further elevator deflection to maintain the 1g flight path. As has been said earlier if you reduce the power the THS will try to keep the nose high enough to maintain the 1g flight path all the way into the stall.

447 however did not enter the stall in the classic straight and level gently slowing down manner. The aircraft was in a rapid climb to above its flight envelope and thrust ceiling converting kinetic energy to potential energy. There is no prestall buffet or normal handling effects if you pull into a hammer-head stall or tail slide this was not far short of that. The resultant loss of aerodynamic lift as the aircraft ballooned over the top with negative g, gave the THS algorithms something perhaps that had never been considered likely.

Once set up in the stable nose up stall the wrong side of the drag curve in TOGA with a descent speed that was almost as much as the forward speed, there might be insufficient aerodynamic pressure on the elevators even in the down position to get the THS to move. Therefore it would remain fully nose up until (or if) the aircraft responded and started nose down. That may have taken idle/idle and nose down and held down till 30 or 40 degrees nose down attitude till airspeed was regained. That would be something an ex-military pilot might do but totally inconceivable for the 'must loose minimum height' never aerobatted, C-150, C172, PA-44, CRJ, Bus trained pilot. And of course every time there was an attempt to nose down the stall warning sounded and strangely the crew appear to have taken notice of it in descent having disregarded it previously.

This is not a case of playing in simulators, if the real aircraft algorithms fail then the simulator will be unable to replicate the effect. Someone needs to get an out to grass A330 on the way to a boneyard and actually replicate what happened. Good VFR with a clear horizon over uninhabited desert or sea just the thing for a test pilot to try. After all the experienced pilots here (and the engineers) are of the strongly held opinion it was only the fumblings of a poorly trained crew that caused the crash they would have recovered and flown home like the 30+ other reported UAS incidents. Even the engineers here think they could have recovered it after two or three simulator sessions. So there is no risk is there go fly a real A330 through the same maneuver at FL380 show the world how its done and get real information on how the THS behaves dropping at 11,000fpm in a stable stall.

OK465

I would assume here that, even with full forward SS, the airspeed did not go from a fully stalled 150ish to a value in excess of 300 knots in 8 seconds.....

I would infer then that if the THS went from full ANU to neutral in 8 seconds, a trim condition for an airspeed in excess of 300 KIAS clean, while the airspeed was still some margin below that value, that the aircraft was at this point, 'not in trim'.

jcjeant

Yep ... where is Chuck Yeager when you need him ?

Turbine D

Why? Why is this important? we know what happened. The objective is to keep a commercial jet airplane inside the flight envelope it was designed for and not test it for responses way outside of the flight envelope. IMHO, it would be much wiser to take the money and apply it to this:
And, if this is done on a pass/fail basis, perhaps those that don't comprehend will be given remedial training until they do fully understand before returning to a seat in the cockpit, if they ever do.

Lyman

"Yep ... where is Chuck Yeager when you need him ?"

Every Saturday morning, at 0800 you will see him taking off on 25, Grassy Valley air park. He will be flying his friends Aviat Husky.

Wait until he lands about two hours later and catch him at the FBO. If you give him 50 dollars, he will say hello. Make it a hundred, and he will shake your hand.

really.

Turbine D

I would really hope you didn't get the THS movement idea from an Airbus driver. The sidestick controls the elevators. On the A-330, the elevator deflections are 30º nose up and 15º nose down. THS deflections are 14º nose up and 2º nose down. So if a pilot flying level at 350 and Mach 0.80 with a thrust setting of ~85% N1 decides to pull back the sidestick and hold it for a prolonged period of time, some time being all the way back, the elevators will accommodate his command. They will deflect all the way to 30º nose up which it did on AF447. then the THS will begin movement (trimming), as calculated by a computer, to neutralize the pressure on the elevators and also moving up to near the maximum of 14º nose up which it did on AF447. So simply said, the THS didn't lead to the stall, the elevators did based on sidestick positioning determined and held by the PF. Once in the stall, the elevators held the aircraft in the stall, not the THS.
I would very strongly urge you to go to R&N, AF447 report out to PJ2's post #811. Read what he has to say and click on the underlined post #457 to learn about the THS from an expert.

gums

Maybe a deep breath and get away from some of the personal affronts I have seen lately. So I'll affront Yeager versus some folks here, heh heh.

Lyman is very close to the Yeager persona, in my not so humble opinion. Met him personally twice. Once a formal affair when I was a yute, next time was really neat - 16th TFTS at Hill in 1979.

Desk clerk announces we have a VIP and we're welcome to get to the main briefing room, a theater deal. It's Yeager. He sits down on the edge of the stage and we just talk for about two hours. We ask questions and he answers, embellishes, brags, confesses, etc.

So 6 years later I am on the Northrop legal team for the lawsuit between McAir and Northrop about cockpit displays and avionics and such. Another pilot was an A-7/F-18 USN Lt Commander then flying for FedEx. Our third pilot was Yeager.

The other junior toad and I were getting $100 per hour for our work. We both made about $1000 one day when we checked out the F-20 at Edwards in order to fly the thing the next day. Sheesh - this was back in 1985, so a good deal, ya think? Yeager was getting $800 just to show up for anything, and I don't know what his hourly rate was.

So Lyman might have it pretty close. At our depositions the McAir team let Yeager go real fast, but I made about $500 that day for my grilling. Yeager was already well known for liking the F-20, so I guess McAir folks figured he was not gonna provide much to them.

In all fairness, I think if you got Yeager in a very informal situation that he had a yearning to attend, he could be pretty neat. In my case, we were the first squadron in the world ( and first to fly an operational FBW jet, I must remind a few here) and he wanted to talk with us and make a "show" at the squadron. That summer we had many dignitaries show up, and they all signed the bar we had in the rec room, shook hands and such. Yeager was the only one that just sat there with us and talked with us as aviator to aviator. Was a really neat time and place, I tell ya.

And now back to our regularly scheduled fray.