- 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.

@ BOAC:
 

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.

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?

The view from the P3 seat
 

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.

Conditioned response
 

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.

@ CS:
 

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!

http://i474.photobucket.com/albums/r...A333rdSeat.jpg




Below A320 (not sure i'm not familiar)

http://i474.photobucket.com/albums/r...999/A320TW.jpg

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!

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.

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!

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?

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.

Airbus Cockpit Pics
 

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...

http://i1116.photobucket.com/albums/...rbusPoster.jpg

Apols if the pic screws the page width...

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?

Beats me. :bored:

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. :ok:

Pull up
 

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.

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?

@HazelNuts39

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

And this is a clear issue of aircraft design.

Lonewolf 50;

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

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.

- 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'..

So what? Level at 250?

Perspective
 

Garage Years, # 926

The pictures are nice, but they show a misleading perspective. The photos are taken using a very wide angle lens, in order to capture the whole cockpit in one view. The downside of such a view is that objects seem to be much further away than they really are: you would think it is about a mile to the instrument panel, actually the observers knees are pressed against the pedestal, the view towards the sidestick is obstructed by the broad shoulders of the pilot, etcetera. If the pictures had been taken by a lens more closely resembling the acute field of view of the human eye, about four pictures had been necessary across from left to right and three rows from top to bottom.
Unfortunately, the pictures that I have to demonstrate this, contain recognizable pilots in view, so I will not post them here.

Chriss Scott, # 924

Well said, although I would change your statement
"why did the PF demonstrably embark upon and maintain a clearly unsustainable climb from level flight? "
into "a clearly unsustainable pitch attitude"

I know it runs into semantics, because you can reply that clearly they managed to sustain the pitch attitude all the way down into the ocean, didn't they, but is was the unrealistic pitch attitude that caused the speed loss and subsequently the stalled condition.

Chris, A33Zab, the photo below, taken from the Right Seat, is of an A330 pedestal/trim wheel/trim indication. The trim indication is smaller than the A320 and is on the outside of the trimwheel. I recall it being highly visible from the front seats but it seems not visible from the Observers seat where the captain likely would have sat down, (cockpit arrangement diagram below).


http://www.smugmug.com/photos/i-9czg...-9czgPfz-L.jpg


http://www.smugmug.com/photos/i-QNCj...-QNCjZ2G-L.jpg

Having an AOA indicator in the cockpit doesn't necessarily imply that it be used as a control instrument or even incorporated in one's scan...

But it would be the first place I would look if I heard, "Stall, Stall".

The digital/analog indicator on the PFD in "some" 737 NG's is very unobtrusive...and in the aircraft without it, it's even more unobtrusive.

Does the trimwheel move when autotrim is active ?

Garage Years,
Thanks for the photos and yes, EMIT, there is a perspective problem with that wide-angle lens. Both pilots' seats look to be well-aft of their normal in-flight positions, particularly on the A320 photo. When I sat on the P3 seat in its central position, my knees were almost touching the back of the centre console. The A320 P3 seat is adjustable sideways (but see below).

Lonewolf_50,
In daylight it would be possible to see if the stick was being pushed or pulled, but it would be difficult at night due to the low illumination of the side console.

PJ2,
Thanks for that better photo of the A330 centre console, and the seat plan. When sitting in harness in the P3 seat, it is still possible to move your torso to the left or right – provided the inertia-reel shoulder harness is not locked. I think that should enable enough sideways head movement to see the left or right THS-position scale, but you may well know better! Do you have access to a sim?

In the seat-plan diagram, do you agree that both P1 and P2 seats are in the full-aft position, provided for ease of entry and exit?
And is the P3 seat moveable sideways, while remaining attached to the rear bulkhead? If so, it looks further aft than on the A320, so viewing the sidestick across the lap of a pilot may not be possible. Is it capable of being locked in more than one position, like the A320?

Quote from mm43:
It is worth noting that no control surface systems fault warnings entered the the CMC and resulted in ACARS messages. There was plenty of time for them to be transmitted, and due to the manner in which the BEA produced their Note, it may be safe to assume that there were no control faults recorded by the FDR.

Yes, and I agree with the rest of your analysis.

And what would be the next thing you would do?

Doesn't the "what" depend on if you are up high or down low with the gear down? ;)

HN - whatever - it is really irrelevant since we understand NO effective recovery action was taken. Far more interesting (for me) is the answer to my query on #902 which I guess no-one knows? Very reassuring.

DJ77;
Yes. Like the Boeings (although I can't recall the B767's arrangement), the trim wheel moves with trim changes in either manual or auto flight. It is in motion, quite frequently, with the small speed/pitch changes that normally occur.

Chris;
Sitting in the center seat it is entirely possible to move sideways slightly and observe the trim position. Other considerations in reading the trim setting would be turbulence, the fact that the indication and pointer are on the top of the indicator and one is viewing from the rear, (there is no parallax however).

Yes, the forward seats appear to be in the full-aft position - the rails take each seat slightly outboard for more room - still, it is a bit of a step across the inboard part of the seat to get in.

The third (center) seat in the A330/A340 is on rails, well ahead of the rear bulkhead and cockpit entrance. The rails take the seat from the full forward position, which is about eight to ten inches behind the aft edge of the pedestal, rearwards about two feet behind the pedestal and thence to starboard about two feet, maybe a bit more. The fourth observers seat is well to starboard, behind, and to the right of the F/O position, and fixed to the bulkhead.

In my opinion one cannot adequately see or judge what movements on the stick are occurring. Most movements are tiny - a pitch-up such as this one might take a two, maybe three centimeter movement aft.

When I first checked out on the A320 I really liked the "Iron Cross" feature because it told me what the other stick was doing. On my first takeoff, the symbol disappeared at lift-off and I distinctly recall being surprised because I thought it was a natural and needed bit of information. Over the years I grew used to using many other cues as to what the other stick was doing and the Iron Cross would not indicate the tiny movements referenced above, but the airplane would. Communication between crew members on this type is vital where any possibility of confusion exists - it is a "cerebral" airplane in that sense, displacing physical cues with digital cues which must go through an interpretive process first. That was "the veil" that I felt when I first sat in the A320's cockpit. The "interpretive process" becomes natural and as swift as in a conventional cockpit after a while and one can get very good at it, all subconsciously of course.

I don't know the arrangement of controls in fighters, so let me ask those who flew them - do fbw fighter aircraft have a way of conveying to the pilot in the front or the back seat, what control inputs the other pilot is making or do both sticks move, (via mechanical connection, etc)? Are there back-driven autothrottles in any types - how is thrust control arranged? Is it standard to display AoA in every fighter?

Svarin, #848
I'm thinking about something that has one function. An adr is probably a
good example, as it's function is simply to measure air data parameters
and send the results elsewhere. It's functionality is quite limited and
the only thing the internal software must do is produce accurate results
when the inputs are within range and an error message when it finds that
the inputs exceed the limits of the measurement hardware. That may be a
little oversimplified, but it's basically a box that converts barometric
pressures to electrical signals that other parts of the system can
understand. Because of the limited functionality, it's not too difficult
to devise tests that provide a high degree of confidence that the thing
is working to spec.

The complexity problem arise when many of these individually reliable
boxes are connected together, as you then have time as an added variable
thrown into the mix. Depending on conditions, the various boxes send
their messages with slight variation in timing, so that, for example a
data or error message may arrive at one box before, or after, a message
from a third, or fourth. The testing and validation problem is one of
how to model or prove the system correct when timing variation, together
with all possible system operating and failure modes, probably gives
millions of possible combinations / sequences to test against.

You might compare an adr to a fiddler in the local pub, while a complex
interconnected system is more akin to a symphony orchestra. If the
orchestra is playing Bach, then you're probably ok, so long as everyone
is in tune and in sync. Jazz, and you might be in big trouble :-)...

Hi BOAC,
What is it you don't understand about maintaining a pitch attitude (modified for 1g) by auto-trimming out the load due to changes in air speed?

Well, rrat - it is to see HOW exactly it does it, do you see? More to the point, do you know? Are there ADC inputs to THS setting? Do I assume you know?

Thanks for replying, by the way.

PJ 2 #944

In F-16, no feedback from one sidestick to the other.
Even more, in the F-16 the sidestick cannot be moved like in the Airbus. The signal is the FORCE that is exerted on the stick, not the angular displacement.
In the original, F-16 the stick was really as rock solid as an iron pipe, it turned out that that configuration was not so nice for finer control, so a little bit of play was built into the versions from Block-10 onwards (maybe 2 or 3 millimeters of movement at the top of the stick).
Philosophy for the non-moving stick is as follows: there is a "perfect" relaxed steering attitude for your hand, the stick is built in that attitude. If the stick had to be displaced angularly for generating steering signals, that would mean rotating your hand out of the perfect steering attitude - would be a painful exercise under a 9 g load.
In the Rafale, the French originally built a sidestick akin to the Airbus setup. It took some rough remarks from an F-16 pilot to get the factory to switch to an F-16 type stick, after that the Rafale was a fine flying machine.
Info on what the other guy is doing comes from aircraft response. No such thing as "Dual Input" calls as in Airbus. Does it always work out fine that way? No, there has been a case in F-16 history when a non F-16 rated backseater kept his feet well away from the rudder pedals; unfortunately that brought his knees very close to his sidestick. When his G-suit inflated during a dive pull-out, the expanding suit pushed the sidestick sidewards, unexplained sudden roll, didn't work out well.

Autothrust in a fighter, no, everything is done manually. Exception, I believe, Saab Viggen, for landings on short runway strips.

Angle of Attack indicators in fighters? YES.
And, yes, they are actively used.

AOA in civil airplanes - unfortunately, mostly in disguised form: the red minimum speed indication on the speed tape is actually AOA driven, ever notice how it moves up as you increase g-load? (OK, that is observed mostly in the SIM, e.g. during unusual attitude recoveries). Too bad, that when the speed tape is taken away because of system errors, you also loose your disguised AOA indication.
So yes, I would like an AOA indicator in civvie aircraft.

Trim
 

PJ 2 #944

In the 767, there is no trim wheel and no trim actuation noise. Trim position is indicated on a tape style indicator on the pedestal, approximately next to the throttle quadrant. Only time you really use it, is for setting of take-off trim, after that, trim more or less disappears from your conscious memory.

(PJ 2 knows, but info for others)
When flying manually, you trim as needed. A/P trim works without pilot involvement.
Tricky thing is, autopilot may trim very much nose up without your conscious knowledge. Results are not only awkward in this AF447 case, but also in the B-737 Turkish 1951 stall accident in Amsterdam, and in many stall incidents.

May I point you to the fact that similar statements would have to be made for most if not all types of airliners ?

Full NU Trim will overpower the elevator not only in the A330.

And please don't assume it can only happen in an Airbus that you are handed an Aircraft with Full NU trim. AP commanding full NU Trim quitting and handing over a plane with 10° + NU Trim.
Has happened on different types.


Although I don't know for sure how it is technically solved in the A330 the system behaviour strongly points to an inertia based (read IR) system rather than anything ADR.
As always happy to stand corrected.

PJ2,
Thanks for confirming that the THS-position indicator is visible from the P3 seat, as I expected. However, I should admit that, on entering the low-lit cockpit from the front vestibule (or galley?) area, there is a potential problem of adjustment to night vision. (I know that the vestibule lights probably dim automatically when the cockpit door is opened, but that only serves to protect the night vision of those already in the cockpit.)

Quote:
In my opinion one cannot adequately see or judge what movements on the stick are occurring. Most movements are tiny - a pitch-up such as this one might take a two, maybe three centimeter movement aft.

You are right, particularly in the case of pilots who prefer to hold the stick continuously in the palm of the hand, rather than making inputs and then releasing. With the roll problems the PF was experiencing, and the reversion to Roll-Direct law, he may well have been holding it in the palm of the hand. As I've previously commented, the low illumination of the side console at night would also make it very difficult to see the stick.

[EDIT] There is another slight possibility re cockpit illumination. Being in a remote area, and in the vicinity of thunderstorms, the crew might have elected to put the dome light on. This would not be my choice, but I've seen it done. It floods the whole cockpit with light.

Hi,

Well .. as the THS was in full deflection .. honestly .. regarding any error of interpretation .. we can put the eventual parallax out of the game.
I assume if one check the pointer of the THS wheel .. it will see immediately that the pointer indicate a full deflection .... :ok:

Hi BOAC,

In Direct Law it's like a Boeing, you don't need any ADC input to manually trim the elevator stick load out.
In Normal or ALT LAW the autotrim works in a similar way to maintain the (modified) pitch attitude. I can't see why it would need any ADC input either.