@RF4,

Thx for the explanation. Reducing the RoC from 7000 to 1100 fpm in 24 seconds corresponds to an average normal loadfactor of 0.87 g. Maintaining that a couple of seconds longer would have avoided the stall. A drastic maneuver?

Problem being, that at that point stallwarning Nr. 2 communicated approaching loss of control, which was honored by PF by selecting TOGA, a fatal failure.

A drastic maneuver would have been to unload to at least 0.5g to reduce the pitch faster, thus conserving more energy and gaining less altitude, hereby avoiding SW 2 and thus no TOGA with its negative side effect.

The aircraft ran out of speed before the climb was stopped.

Well, BOAC and Retired have it pretty much the way I see the scenario.

Don't like to be brutal but here I go from a diehard single seater and more. And I had over a 1,500 hours as an IP in different kindsa jets, some side by side, some front seat/back seat, and most as a chase pilot flying maybe 30 feet from the nugget in his single seat jet. Multiply those hours by 8 or 9 to equal the "heavy" pilot IP time.

BOAC has expressed my primary concern. How come the experienced pilot failed to hit the other guy on the head ( boxing glove from the left seat)? The CVR indicates a few cautions and words of advice, but not "commanding" verbiage. e.g. "alternate laws", "we're going up, so go back down". "gently" and so forth. BOAC's point about being BZ with ECAM crapola might also be a factor.

Then what Retired says, which I agree with to the nth degree. A 1.6 gee pull is very noticeable, and that comes from a guy that routinely pulled 5, 6 and even 8 gees in less than 1 second. Unloading to a half a gee is also very severe unless you are flying A2A combat.

The immediate pull is what I am most concerned with. The jet was doing O.K. and then the speed sensors went tango uniform. Big deal. Why the pull up? Why the experienced pilot in the left seat doesn't take some action or yell at the nugget?

For one more time, the gee command doesn't need full back stick to keep increasing pitch attitude. A tenth of gee command can raise or lower the nose at a degree or two per second if you aren't at approach speeds. OTOH, when I see full back stick for a minute or two, it scares me. What was the experienced pilot doing then?

I also agree with BOAC WRT the mechanically connected yokes. My A-7 time was chasing a nugget who was in another airplane! No family models. So I used him as a giant attitude indicator and then glanced down to see speed, AoA and so forth. In the Viper family model we had zero feedback from the nugget in the front seat. The sticks did not move more than 1/8 inch in any case. So I watched and tried to figure out what the nugget was doing. Pitch, power ( at least the throttles were mechanically connected and I could see the tach) and attitude. So the Boeing yoke discussion is moot. Only control aspect that bothers me is the "auto throttle" and no visible/tactile movement when it changes the power.

When I first joined this discussion, I had posited the "deep stall" scenario. But looking at the 'bus charts and such, then the pitch moment coeffiecients, I could see the difference with the 'bus and my Viper. No easy way to keep the 'bus in a stall unless you keep pulling back ( THS doesn't help, either) . Our Viper FLCS prevented you from pushing nose down once we exceeded the AoA limit of 30 degrees or so. The horizontal tails were already commanding nose down. And the aero of the 'bus seems super. Little shaking or buffeting that lets you know you are stalled. It's only the descent rate and attitude that doesn't agree. You know, "gee, I have 10 or 15 degrees of pitch and 10,000 feet per minute of descent rate". Duhhhh? And oh yes, " I am holding full back stick".

As with PJ, I shall try to remain away from the discussion. Will check in every now and then, but seems to me that most agree we had a major failure of crew coordination and a belief that the jet would keep them outta trouble.

Deceleration was caused by the pull-up, not the other way around. Of course, anyone is entitled to disagree with my notion that cause precedes effect.

A330 is not tactical fighter, she doesn't fly anything resembling typical F-4 mission profile, there was no need to gain any altitude.

What negative side effect of TOGA? Mind you, we are discussing the aeroplane flying at FL350.

Right stick went into nose up position as the stall warning was triggered second time, consequently attitude increased to 17.9° peak -see page 62. Eventually, it did stop the climb in the most disorderly manner.

This is PPRuNe. Anything goes provided it's delivered politely and respectfully.

@ Clandestino

Do you actual read a post in conjunction with the referenced discussion (why was the pullup not arrested) or do you just look for some words to comment on? Do i write in greek or Kisuaheli?

Did i say anything from being necessary to gain altitude or that A330 flies like a fighter or should do so? Stick to my words and do not lay words in my mouth i didn´t write.



Imho that it was a major assisting part in changing pitch by 11° in connection wit the NU SS. Do the math, look at the loadfactor charts and come back again to comment. Later on the opposite happened, reduction of power had a noticeable effect on reducing pitch, as you stated yourself in previous posts. And we are not discussing an aeroplane flying at FL350, but one that was just short of falling out of FL350. TOGA might not have that much effect on an aircraft in FL 350 flying already at max speed, but it sure has more effect on an aircraft which is on the way to loose it´s aerodynamic stability due to lack of flying speed.


Again, read my post as answer to HN´s question. I´m talking about the time period before stall warning two, when the PF attempted to arrest the climb with (HN computed it) average of .87 g´s, which was not enough. The SW2 sounded before a NU SS input was made again and the aircraft was still in a climb with 1.100 fpm. Would the PF had made his ND inputs more agressive like the assumed .5 g´s, then it would imho have changed the siuation significantly.

It is shocking – The message is : Something is very wrong here – It can be a crucial part of the enigma, especially for the Captain who is just entering the game.
The only time you see a yoke in that position is for flight control check during taxi-out.

Maybe yes maybe no – But what is better ?

1. A given piece of information for all to grab
2. The suppression of such piece of information

You may have noticed that my post was in response to cpt. Sullenberger's opinion that the AF447 disaster "would have been much less likely to happen on a Boeing".

Not true. The stall warning came 4 seconds after the PF started pulling. If he had maintained the nose-down input that produced 0.85 g there would have been no stall warning and no stall.

As RetiredF4 says "Do you actual read a post in conjunction with the referenced discussion or do you just look for some words to comment on?"

PF initiated the climb to "recover" the apparent 400 feet loss due to Mach correction. That was the cause of the initial climb.

A side effect may have been that he suffered from Somatogravic illusion with an deceleration of 3 kts per second which may explain why he was seeking confirmation. (See Page 90 interim report 2011.)
"Ok. Ok. Ok. I am going back down?" (with a serviceable ADI in front of him) PNF then says "According to the three you’re going up so go back down"
PNF then selects ALT ATT "The ‘AIR DATA’ selector then the ‘ATT/HDG’ selector are positioned on “F/O on 3.

If they are not suffering from some Somatogravic illusion with regards to their attitude, why select ALT ATT?

rrr,

IMHO one does not get a somatogravic illusion simply by pitching up.There is no change in the total acceleration perceived, the longitudinal acceleration is equivalent to the change in attitude and flight path. A pendulum suspended from the cockpit ceiling would remain in the same position in the airplane. AIUI, somatogravic illusion is caused by a change in the total acceleration, e.g. by adding thrust or applying brakes.

Hi HazelNuts39,

Please see my post 599 and the report Transportation Safety Board | Home

If you calculate their linear acceleration, it is about the same as AF 447's deceleration.

- full motion simulators rely on this to generate the illusion of 'acceleration' by tilting the platform nose up! So, you are correct in that the actual pitch motion does not generate it, but the new attitude achieved (nose up) does.

Hi rrr,

I've read that report. It doesn't explain how they did their calculations and I don't have access to reference 52.

I do respectfully disagree. The pitch change produces a change in flight path. Once stabilized on the new flight path, lift equals weight and the AoA is the same as it was before, hence the change in pitch equals the change in flight path angle FPA. Without a change of thrust or drag, the change of linear acceleration along the flight path is given by a = g * delta FPA = g * delta pitch (angles in radians).

It´s not black and white again.

Figure 27 final report

Figure 28 final report

The PF never had a steady SS, and main cause for the Stall Warning two was the impending exiting of the flight envelope due to airspeed, altitude and pitch resulting in approaching creitical AOA. The SS NU phase might have initiated it a tad earlier, but imho we dont know the effect of it, as the SS input is not necessarily immidiately transferred to a elevator deflection (FBW) and a elevator deflection does not immidiately tranfer to a flight path change (delay until the aircraft reacts). Additionally at 02:10:45 there was a thrust reduction present, just 4 seconds prior the SW2 sounded. We didn´t talk about the effects of that one jet.

The trend to more NU SS might also have been a side effect of handling the throttles from PF, first the reduction at 02:10:45 and then selecting TOGA at 02:10:56.

But basically what i´m trying to say in regard to BOAC´s initial question was, that i see an early recovery attempt prior SW two (see loadfactor). The recovery attempt was not appropriate to the severity of the initial pitchup and the altitude rise and speed decay could not be stopped quickly enough. When the focus of the PF changed from the SS to power and switching indicators and the SW2 sounded, TOGA and SS position kicked the airframe outside the flight envelope without being noticed by the aircrew.

But again it is my oppinion and not fact, and everybody is entiteled to a different oppinion.

RF4,

Look again at the figures you kindly posted. On figure 27 you can see that at 02:10:49 the pitch stabilized at 6 degrees and the PF's sidestick going from push to pull. On figure 28 you see the PF continuing to pull. The response of the airplane is immediate, it starts to pitch up. It is that pitch change that causes the AoA to increase and to exceed the stall warning threshold.

Not shown on these figures, the load factor changes from 0.85 to 1.15 in those 4 seconds.

The thrust levers are moved back to 33° at 02:10:47 and the N1 decrease to 85% in 4 seconds. That may have added a nose-down moment change, but did certainly not contribute to the pitch-up.

The following graph illustrates the drastic maneuver:
http://i.imgur.com/5m36B.gif?1

- and entitled, of course, but way off beam! Perhaps you could tell us how you think a full motion sim produces a sustained feeling of acceleration (or deceleration)? - remembering, of course, that a sim does not have an 'FPA'.

I would suggest you read up on somatogravic illusions. In this case it its the otolithic membranes that are in play. Skylibrary covers it well in www.skybrary.aero/bookshelf/books/767.ppt - you will see the effect on slide 20.

BOAC,

Thanks for the link. Very interesting, and confirms what I thought:

Slide 24: The gravity-inertial acceleration (GIA) is the vector sum of the vector of gravitational acceleration (upward) and all other accelerations.
Slide 25: A somatogravic illusion is a false sensation of body tilt that results from perceiving as vertical the direction of non-vertical gravito-inertial acceleration or force.

The direction of the GIA is the same as that of the pendulum suspended from the cockpit ceiling. Its orientation to the airplane longitudinal axis does not change when the airplane pitches up. Its orientation relative to the pilot's head doesn't change if the pilot doesn't change his position relative to the airplane. To convey the same sensation in a sim, the sim's cab doesn't tilt like the airplane it simulates.

EDIT:: Perhaps we should be talking about somatogyral isnstead of somatogravic illusions.

- no - they refer to rotational effects and we are looking primarily at attitude based effects.

Did you see slide 20? The effect of 'head tilt' as they call it - 'nose up' attitude here - which results in a sense of acceleration. Add to that the pressure felt on the back due to the tilt, all of which can cause a sensation of acceleration. I suggest you try to watch a full-motion sim - perhaps the best demonstration would be on the 'landing roll' when the sim adopts an extreme nose-down attitude to produce a deceleration effect where you are pushed forward in your harness..

You cannot just rule out somatogravic illusions in 447. It appears they did not really appreciate the attitude they had, so they could well have felt misleading 'acceleration' effects. I have no idea. I take it you have never experienced 'the leans' or the feeling of pitch induced by rapid acceleration/deceleration without 'normal' visual clues - very powerful illusions and the cause of many accidents..

SIMS
 

Comparing SIMS to real world is a complicated matter, Hazelnut.

In a SIM, the tilt of the cabin is used to give an ILLUSION of acceleration, which then is confirmed by the instruments: the attitude indicator tells you that you are straight and level, and the airspeed indicator that you are gaining speed: sensation and information all agree.
Apparently all the information is congruent, but actually you are stationary on the ground, sitting in a box with no real outside vision.
If you would sit in the SIM with your eyes closed, your motion sensing system would tell you the truth, that you are tilted backwards. Your cognizant system however, overrides your feeling, because all instruments tell you that you are level. Your feeling then "corrects" itself, it must be an acceleration that it senses (but in the SIM the instruments are lying to you, compared to the real world)

In the cases of somatogravic illusion in actual flight situations, when they lead to an accident, the feeling system overrode the cognizant system. No matter how correctly the instruments displayed that the aircraft was level (or at a normal pitch attitude) and accelerating, the feel system told the pilot that he was pitching up abnormally, to which he instinctively reacted by a push on the control (yoke or stick).
Instead of resetting their feel system to the reality shown on the instruments (which tell the truth, in real aircraft), the accident pilots try to reset the world to their illusions.

The human feel system is relatively coarse: accelerations go unnoticed, when under the detection threshold. Ask any fast jet pilot about close formation flying in IMC: if the leader rolls in roughly (noticable) but rolls out very smoothly (not noticeable), then you will feel as if still in a bank, when actually level again. Do that twice in a row and the wingie will feel as if almost flying upside down. A quick glance at your attitude indicator would instantly reset your internal gimbals (even though you were supposed to never take your eyes of your flightlead, such a quick check inside your own cockpit was what you really needed to do).

In a SIM, the motion system may quit if you maneuver heavily (unusual attitude recovery, or trying to replicate AF447). Just disregard your feeling system and fly the instruments, that is what instrument flying is about.

Of course, in AF447, some instruments did not tell the truth (airspeed), but as said many times before, pitch and power were shown correctly and were ample info to keep airplane safely in the air, be it with slightly less than the usual accuracy of a knot and a foot that us perfectionist always strive for.