BOAC

- can you tell us please where that unattributed quote is from? If this relates to the 330, I would also appreciate an explanation of how the trim compensates for 'speed' (and which 'speed') ie is its response a direct function of 'neutralising' the resulting elevator input required for speed change or is there a direct 'speed' function for the THS?

The last para regarding 'lock' at 8+ is particularly alarming.

A33Zab

Its stated in FCOM Vol 3, Supplementary Techniques, Flight Controls, Flight Mode. (3.04.27 P3).


I think you understand but for the ones which do not:

Pls don't consider the THS being locked but read as:

"If THS > 8 up (and no autotrim available), full elevator pitch down authority may be insufficient for speeds above 180 knots."

This also from FCOM 3 and mentioned several times in the 'Abnormal and Emergency' section.

BOAC

Thanks A33 - I have to admit the word 'locked' (ie no 'autotrim') does not sit easy with me, especially with what I understand to be a not unusual training policy on AB a/c regarding 'use' of the trim wheel..

So, what are the 'speed' inputs, if any?

Chris Scott

Turbine_D and A33Zab,
Thanks for your responses. The view in the photo is exactly what I have in mind and memory, and could easily be mistaken for an A320 centre-console. (I presume, however, it is an A330?)

Each pilot has a THS trim wheel. (Unlike the sidesticks, they are interconnected.) There is a THS-position indicator on the outside of each wheel. From the P3 seat, one or the other can easily be seen by moving your head and shoulders laterally to left or right. Do you now agree, A33Zab?

I cannot be completely sure in relation to the A330, but on the A320 you can also observe either sidestick, provided you lean forward slightly. This enables a training or check pilot to monitor the PF's handling of the sidestick, which is impossible from the PNF's seat. This is less easy, however, at night, because side-console illumination is low.

The clear view of the whole operation obtainable from the P3 seat is one of the arguments in favour of conducting line checks from that seat.

takata

Hi Lonewolf,

So far, there is no such "conditioned response" measured behavior, including several other AF crews, as those many previous cases won't show any pattern of similar behaviors.

With all due respect, Your Smartiness should be right. It seems to be all about "conditioned response" and I can't understand what you are talking about.

Nonetheless, if your Smartiness did his homework, he should have also noticed that most recorded UAS events included the same STALL warnings (ie. see Air CARAIBES report) and none resulted to such zoom-climb until AF447 case.

Then talking about "conditioned response" doesn't fit with the case on hand as the previous pilot reactions ranged from "no stick imput" to "emergency descent".

The fact is that the STALL warnings was already identified as the main factor of early confusion during an UAS event BEFORE AF447 case. It was where the procedure seemed already weak (some concern about it was discussed with Airbus) as it was also the first information displayed before the UAS issue was identified, then it was potentially known as dangerous.

I'll post further data later tonight about those previous cases.

A33Zab

Sorry Chris, still not convinced, maybe (for A330) if you ask P1 or P2 to move to the side and lean forward L or R from P3 seat?

Below A330 for sure!






Below A320 (not sure i'm not familiar)

Chris Scott

Hi A33Zab,
Love your photos – thanks. But am at a loss to understand your visibility problem. Could we be misunderstanding one another?
Quote:
Sorry Chris, still not convinced, maybe (for A330) if you ask P1 or P2 to move to the side and lean forward L or R from P3 seat?


P1 and P2 do not block your view of the centre console. No problem!

Chris Scott

A33Zab,
Without affecting my previous, I now notice from your two centre-console photos that there is a difference in the THS-position indicators between the A320 and the A330. The A320's are inboard of each wheel; the A330's outboard. (Refer again to PJ2's photo.) This should improve visibility for the P1 and P2. The P3 would, as I said, need to move head and shoulders left or right to observe one or the other.

Otherwise, the two aircraft seem virtually identical, although the thrust-reverser levers look to be different.

HarryMann

With much discussion - some verging on serious disagreement though perhaps that is mainly in emphasis and tone rather than on facts - the following points seem to be featuring strongly where tentative agreement exists:-

1) A stall warning system that has (more than) raised eyebrows before, could be at the centre of cockpit crew confusion once the event had 'matured'
2) A THS trim system, has possibly (or effectively) 'run away' to an extreme setting, that would not be expected at high Mach and cruise Altitude. Said THS system's manual trim wheels do not light up, flash, shout or scream, nor display messages on PFD when at such an extreme setting, even when at that Mach, Alt and Config which surely must be considered a bizarre combination - so why not?
3) An AoA sensor, that whilst likely more immune from debris and/or environmental contaminants than pitot-static AS sensors, and an essential last-ditch safety device (feeding SW system), as well as providing a valuable singular (& independent) item of air data in its own right:
a) did not have its own dedicated display (matching its singular discrete origin and across-the board usefulness)
b) had its feed into the SW system inhibited/constrained in a fairly predicably dangerous fashion (that is creating a fait a complit, should a full (deep sic) stall actually occur)

It appears from reading all the above posts, that their only chance was the Captain, who fought back to the cockpit upon call ASAP, like as not assessed the situation correctly despite not having even half the history & information at his fingertips, and had begun to take pro-active steps along the right lines when old father TIME just ran out for him - I cannot help but feel fustrated even now that we have learnt so much over the last 100 years, and forgotten half of it..

That half is...

We are in WING-BORNE FLIGHT through a fairly decent & consistent layer of air and very few things matter most of the time:
other than AoA and a modicum of speed and thrust, even the latter can be dispensed with for quite a long time in most aircraft, subject to some altitude.

But AoA, not even pitch, is everything with wings and air. Both the THS system and Incidence vanes are major player in AoA matters.

Goodness - even a bit of string (albeit kevlar with a luminescent tracer in it) alongside each side-screen could have jerked someone back into the real world in this instance, no?

Ok, hand-up to hindsight... but having flown sailplanes & hang-gliders, still find it strange that the basic origins and roots of flight are ignored... even the Space Shuttle is an AoA device when back in the atmosphere, indeed, most crucially when re-entering at the very outer limits!

Chris Scott

HarryMann,
That was a most thoughtful and relevant post.

Just a few thoughts of my own, based first on your numbered ones:
1) The inhibition of the stall-warning when the sensed airspeed falls below a certain value needs to be addressed. I suspect the problem is that the present generation of AoA sensors cannot operate accurately at very low TAS, which is what they experience every time an aircraft vacates the runway after landing. Ground/flight detection remains, unfortunately, less than 100% reliable. That may sound ridiculous in the context of AF447, but it's part of the problem for the designers.
2) Agree as far as configuration is concerned. There is no way that you would ever want a THS setting of 13NU on a clean aeroplane. Even half that value is a frightening thought.
3a) Rightly or wrongly, this is standard industry practice: not an Airbus-ism.
3b) The constraint is an attempt to avoid false stall warnings, which themselves are dangerous, but it failed the crew in this instance.

Re some of your other points.

The captain had an impossible task on his return to the cockpit. In any case, the "ride" would have made any activity/observation extremely difficult, unless and until he managed to get into the P3 or P4 seat and attach seat-belt or full harness. (The view from the P4 seat is likely to be poor.)
Regarding your other comments, I think the emphasis on AoA would involve revolutionary changes in civil pilot training; starting ab-initio. To justify that, we would need to consider how much a lack of AoA awareness may have contributed to other accidents, not only the obvious ones like G-ARPI, which also involved an unawareness of wing configuration.

In the case of AF447 the bottom line remains, however: why did the PF demonstrably embark upon and maintain a clearly unsustainable climb from level flight?

Lonewolf_50

takata: your tone is unappreciated. I am trying to be cordial here. You might notice that I used the smile to indicate humor in the Brenner Pass jest. You respond with snotty sarcasm.

"Tunnel vision" is a particular kind of congnitive problem to overcome in a cockpit. (Also known as target fixation in tactical jets, and a non trivial factor in numerous CFIT mishaps). I find it an utterly unsatisfactory diagnosis for the crew's performance in AF447.

Please go back to the post you have chosen to respond to with such sarcasm, and note my edit for clarity. Compound emergencies versus malfunctions: what are you trained to do, and how are you trained?

LATER EDIT: you may not realize that we are in violent agreement.
I ask you in all seriousness, again, how do you, takata, train people to do tasks? Do you? The point is to connect to your own personal experience, not to talk down to you.

Your pretense that all that is needed to address is previous UAS incidents is at odds with the problem set confronting the crew, and the non-trivial problem to how the crew reacted to stall warning, at altitude. (As noted earlier, whether they should have needed to respond to stall warning is a good question, but once you are presented with stall warning, what do you do?)

mm43 makes an important point about timing, descent rate, and the chances of recovery (via nose lowering and subsequent pull out once the wing is unstalled) that points to the odds of recovery as _low_ once the high AoA, stalled descent had become a more or less stable flight condition.

For my money, he's very close to the mark.

This makes response to the initial stall warning a critical action in the chain of events. Response to stall warning ... trained response ... NOT tunnel vision.

Yet again, the difference between dealing with a malfunction versus dealing with an emergency, or approach to an emergency, and multiple malfunctions at once.

Back to the Swiss Cheese. (Hence the Brenner Pass, more humor). Even with the admonitions from the Pitch and Power Chorus, even with PJ2's well reasoned point that patient, gentle, response to UAS and Alt law flying at altitude, there are still cheese slices to pull out of the stack in how one responds to both malfunctions and more serious inflight problems: stall, or approach to a stall. Again, as I point out, and others more experienced than me have as well, this points to a training issue.

Stall response, and stall training response is linked to the AoA display question.

The industry generally (not just Airbus) chooses not to add AoA gages into airliner cockpits. Sound arguments for and against can be made. One should not be surprised that many pilots would prefer that a flying parameter, AoA, is available on the display, but simply adding a gauge isn't enough.

How do you train? (This question is not now directed at you, takata, but perhaps better said as "how does an organization train its people?" )

How do you habitually incorporate an AoA gauge into your scan? The answer to that question would be a component of the answer in whether or not AoA display is a chosen feature.

If the aircraft monitors the AoA for you (which most passenger planes seem to do), AoA going absent for a while leaves you blind. You can look all you want, and the information you seek isn't there.

This goes back to a question which may never be answered: what did the PF see? What did the nose pitch attitude tell him? The BEA is pretty clear about where the nose was, and how long it stayed there. The largest flight instrument in the cockpit is usually the artificial horizon (attitude indicator) on the PFD. A330 cockpit layout looks to be no exception.

GarageYears

I have a very nice poster from Airbus of the cockpits of the A320/A330/A340 and A380 all together. In reality you can hardly notice the differences.

Below I have tried to post a photo I took of the poster for the A320/A330 cockpits. The perspective is probably a little higher than the 3rd occupant seat, but my take is you COULD see the sidestick from this position. You make up your own mind...



Apols if the pic screws the page width...

Lonewolf_50

GY:

If the sidestick is being held in a pilot's hand, and manipulated, what useful information would you see if you looked at the side stick to inform you of what is going on, other than the movements of the pilot's hand?

GarageYears

Beats me.

I was simply providing the picture, in support of a discussion between A33Zab and Chris Scott, I believe....

Actually I think the pic is pertinent to the on-going discussion anyway.

HazelNuts39

Recovery - (from FL 350, M.4/130 kCAS, 10,000 fpm at 2:11:40) - a few 'ballpark' figures:

1. First you have to reduce AoA to unstall. Let's say pitch down 30 degrees from 15 NU to 15 ND, 20 seconds?? at 10000 fpm that's 3333 feet down, FL317.
2. Then you need to recover to an airspeed that lets you pull say 1.5 g without stall warning, say M.59/235 kCAS/362 kTAS, that's another 3622 ft down, you're now at FL 280.
3. Pull 1.5 g during 10 seconds, 863 ft down, and you're level at about FL270.

Comments welcome.

Lonewolf_50

HazelNuts39

Is your estimate based on the idea of performing the recovery from stall with no usable airspeed reference during the recovery?

Or

Is the idea that, at some point in the recovery, the airspeed indications become valid again?

hetfield

@HazelNuts39

Your computation may be right. Anyhow I have the impression that all three pilots didn't know what the was going on until too late.

And this is a clear issue of aircraft design.

HazelNuts39

Lonewolf 50;

No, I've no ideas about that, it's just physics. But why would airspeed not become usable while pitching down?

Lonewolf_50

If the initial icing issue had cleared itself up, seems to me at some point they would, as the points BEA presents indicate that they did.

At what point the pilots see the info on the tapes, trust it, and use it remains open, but I suspect that if the speeds "came back" they'd be more likely to trust the info than not.

BOAC

- still hoping someone can enlarge on this please? Anyone?

HN - I suspect you have been somewhat optimistic in your height loss for achieving manoeuvre speed and pulling out at "1.5g", not forgetting you are starting at 10,000fpm down and this will increase dramatically during your 'recovery'..