techgeek

There was indication to the pilots of unreliable airspeed information.

techgeek

deSitter,

That's a pretty harsh indictment of a lot of good people. People are not 100% perfect at flying planes or designing and writing software. Most pilots and software engineers are very committed to continuous improvement in our respective professions. In the case of AF447, great care needs to be given to the point of intersection of these two disciplines precisely because, as you point out, errors or omissions (whether piloting or programming) can lead to people dying.

JPI33600

Just to try to sort out this man-machine-interface stuff, can we imagine the very same initial event in a more conventional airplane, say, a B757? In cruise at night, George is in control, and all of a sudden all airspeeds go wild and George gives up. What indications are available on the panel, and what is the PF supposed to do?

KATLPAX

grizzled, thanks well said.

Zorin_75

Again, I think we're still missing too large pieces of the puzzle to tell what really happened. However, from the precious few bits of information that we do have, what makes you come to that conclusion?

engfireleft

Attitude + Power = Performance

It is basic stuff that sometimes tends to get obscured in all the magic. It is also the foundation under which the "Unreliable Speed Indication" drill and checklist were written.

JD-EE

Bienville, you are correct. I am not a pilot. I simply read.

"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)."

I read that as the pitots froze up and the stall warning happened. I am not reading the "left nose-up" as being a violent movement such as would stall the plane. I am also reading this as the aircraft presuming 60kts is an obvious stall so let's warn the pilot he's about to stall. (There being no real unique stall warning.) That's the moment the fit hit the shan.

Now, what sequence do you see happening there? It is worded a little ambiguously. But it does seem to say the stall warning was coincident with the abrupt reduction in indicated air speed. And I take it as dead wrong. You cannot stop an aircraft that rapidly. (I read it as "seconds or less" not "tens of seconds" for the "sharp fall" from 275 to 60.

I certainly do not read a left-up control stick movement such as to the left around the storm (context, remember) as being the precipitating event to a real stall with no drop in air speed followed measurable time later by the "sharp fall".

If I am wrong, please clarify the quoted paragraph as you read it.

Clandestino

Period between 0200 and 0600 is called "window of circadian low" for a few very good reasons.

Relevant time zone was UTC+2.

cirr737

I switched onto the big bus just some weeks ago, so I decided to shut up until now... but how some people here speculate on things like the sidestick commands reversing or protections going crazy, I just want to add one thing: Ockhams knife - the most simple solution is the right solution - for some reason somebody just screwed up.

Probable Cause:
Unreliable airspeed leading to the PF reacting to a stall warning with a prologend nose-up command several times, aggrevating the stall.

Contributing Factors:
(1) Lack of training
(2) Man-Machine Interface
(3) Sidesticks not linked -> insufficient monitoring
(4) Icing of the pitots
(5) Fatigue
---- or ----
(6) Somebody beeing plain stupid (reacting to a stall warning with a pitch up is plain stupid) and shouldn't have been let near a cockpit

Just my two cents....

JD-EE

Bienville, to address the response to the stall I very drily note you are correct. The correct response to a real stall is drop the nose (any way you can) and gain speed. Why did the Continental pilot die with a recorded 150# pull on the stick as his plane stalled into the ground? Why have many other pilots responded to the stall warning with a pull up and goose the engines move? Is this because the stall warning is taught as "the plane cannot stall, this is a warning it might (contradictory here but a paraphrase of what I've read here) stall so pull up and push throttles forward some to compensate."

As I read messages here, on this thread, there is no real "you are now stalled" warning for the A330-200.

So as I see it, based on messages here, the pilots reacted to training and pulled up. A slight bit should have sufficed. It didn't work. So from there it turned to poo rapidly.

And if I had to involve a pilot error in the picture that is the moment. They were not thinking when the stall warning happened or THEY would have seen it was spurious. (IMAO the computer should have seen it was spurious.)

edit: (I must say I am impressed by your persistence in your claim that the first stall warning indicated a real stall. It stalled from around 38500' when the airspeed really did get too low for that altitude. The first warning was, as I indicated, purely spurious. If not howinheck did the plane slow down fast enough to enter a real stall? No indication of such a deceleration is made.)

edit2: I note that the 2:10:16 interval notes the pilot flying made a nose down stick movement. So the initial reaction was correct.

Zorin_75

1. Check the pitch attitude and thrust.
2. If pitch attitude or thrust is not normal for phase of flight:
Autopilot disengage switch . . . . . . . . . . .Push
Autothrottle disconnect switch . . . . .. . . .Push
F/D switches (both) . . . . . . . . . . . . . . . OFF
Establish normal pitch attitude and thrust setting for phase of flight.

lateott

JD-EE wrote:You are absolutely right. The first stall warning was false. The flight dynamics were fine (though I wonder why the computer caused the roll that had to be corrected).

If there was a first false stall warning, would it cause the pilots to question subsequent stall warnings?

lateott

JD-EE is right on. There was no stall initially, just a false stall warning due to a completely impossible "loss" of airspeed.

The stall was created by the PFs reaction to what was not a stall. The computer made it unrecoverable by trimming full nose up.

takata

Hi bear,
0210:05...The airplane began to roll to the right and the PF made a left nose-up input.
0210:51...The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs...The PF continued to make nose-up inputs. The airplane’s altitude reached its maximum of about 38,000 ft...
0211:40...The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds.
[French: 0211:40...Le PF exerce une action sur le manche en butée à gauche et à cabrer, qui dure environ 30 secondes.]
"en butée à gauche et à cabrer"= full deflection, stick left and nose-up (during 30 seconds).

Real stick imputs chanels are recorded by the DFDR independently of the "computer" imputs. It is how one can see that both pilots are possibly giving "conflicting" imputs, whatever the result is on the "computer" and control surface orders.

ihg

Just a question as I could'nt find any reliable information about it.

What sensors do exactly trigger the stall warning? To my knowledge stall warning depends primarily on AOA sensors (taking into account slats/flaps settings)

Or is any other data also processed by the stall warning (air speed?)?

Assuming that the stall warning primarily depends on AOA sensors, and given that you have no/confusing/unreliable/disagreeing air speed data, why not fully trust or prioritize "stall warning" over all other warnings like potential overspeed warnings?

I mean that stall warning would then be based on sensors, which you still could have faith in , whereas overspeed warning would be based on sensor, which obviously show problems. Problems, which brought you into that situation...so why trust any warning coming from them?

Or do I miss something here?


Yeah,sure, all that fancy laws and protections left the pilot no other choice but pulling on that stick until the bitter end. .
I followed your earlier 'elaborations' about software engineering with some sympathy as I partly can support your 'findings' from my own experience. But given your last post here, you just seem to be another one trying to adjust reality to your own 'agenda' with a given result of the 'blame game' from the very start.

cirr737

@lateott

No, it was genuine - The stall warning is based only on AoA which was valid (except later when the speed dropped below 60kts)

>> 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. <<

With a nose up input at this flightlevel with a heavy A/C you are approaching the critical AoA really quick. And with the roll the load-factor increased leading to reaching the critical AoA even faster

JPI33600

engfireleft and Zorin_75, thanks for your answers:
Now, for those questioning the Airbus MMI, how is the information different on the 'bus panel? Attitude and engines N1 are available as well, so what is this nonsense about the A330 MMI having prevented the pilot(s) from correctly reacting to UAS condition?

JD-EE

Please excuse me for a moment while I stop choking on laughter.

There that's better. Now it seems to be that you made up the fact that the plane stalled at the time of the first stall warning without carefully reading the paragraph that defined it. You have a preconceived notion and are driving it into the ground with impressive arrogance.

And to me it looks like you "just make stuff up" to support your notion. You certainly are offering no evidence that the plane COULD have stalled at the time you indicate. What slowed it down far enough? (I will admit that the English in the report could be clarified a little, particularly the paragraph titles. I suspect it's a stylized phrasing for their report purposes. The "From 2 h 10 min 05" indicates "data from" that time shows the following information.)

cxhk

Svarin, I have no idea which airline trained you, but during my initial A330 training, I clearly recall using the manual pitch trim in direct law. This is to expose the pilot in manual pitch trim and allow us to get a sense of how sensitive the pitch trim really is (and it is bloody sensitive). We fly an approach in direct law with manual pitch trim only, as part of the initial type training / exposure to the airbus flight control law, although this is not part of the regulatory requirements, it is still good to see and very good exposure.

Also on many occasion during our simulator training,our simulator instructor had told us on many occasion that when we are in the coffin corner, and if we had a approach to stall situation, with TOGA thrust being auto apply at Alpha Floor, and with THS being full trim, we might not have enough elevator authority to counter the pitch up by TOGA thrust. Therefore a small amount of forward push of the THS might be required to help with the nose pitch down for the stall recovery, 99% of the time we do not need this, but we were told it is available and do use the THS if needed.

Just my two cents!

bratschewurst

What's not clear from the report is why the PF made any stick inputs at all. My understanding is that, even in alternate law, the computers maintain the pitch and roll attitudes previously commanded until the stick is moved, so presumably the aircraft would have continued straight and level, assuming that was the case when the a/p disengaged.

"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."

Would the flight control system countered the roll without the PF inputting left nose-up? And what led him to think that he should pitch up at all? If (as reported) he was flying from the right seat, the airspeed he was seeing was not recorded on the FDR, so perhaps there's insufficient information to fully judge what he was responding to.

But it does appear, if my understanding of the Airbus FBW system (gleaned mostly from these threads) is correct, that the aircraft would have continued in straight and level (and unstalled) flight absent the left nose-up input by the PF.