Okay, first the disclaimers; not pilot – engineer. Not aeroplane engineer – CT/MRI Scanner engineer/SLF so, comparable technology. Yes, I have read most of the threads devoted to AF447, but they keep overtaking me. Although fascinating, I have to say it’s a damned laborious business for an outsider, because of the inevitable TLAs (three letter acronymns).

My sources are almost exclusively what I have read on here and only from those whose posts appear the most authoritative. No newspaper or media reports were used in the making of this post, which, is in the form of either unresolved thoughts or questions arising from information read here. I suppose I’m really just trying to summarise what I have understood from this mass of data and in the hope that it will help others.

I was looking back at a draft I wrote to contribute to the first AF447 thread (but never did) when weather, the avoidance of it and the location of the wreck were the main topics, as so few facts were then known. And, my goodness, how this and other threads have moved on? Now, a remarkable three years later, the Flight Data Recorder and the Cockpit Voice Recorder have been found, against all expectation, and analysed to reveal what appears, to this Engineer SLF, a frankly terrifying set of circumstances.

Through choice or lack of planning, AF447 flew – at 35,000ft – near to a large, complex storm cell that other aircraft had avoided. This, directly, lead to icing of the pitots and temporary loss of ‘Air Data’ – information from the air outside – which meant loss of accurate air speed indication.

This condition lead inevitably and almost immediately to the autopilot and autothrottle releasing the aeroplane into the hands of the two F/Os remaining in the cockpit after the Captain went off for his legal, though given the circumstances of weather, ill advised, rest break. Nevertheless, an ‘Unreliable Air Speed’ condition was never formally declared in the cockpit and no ‘procedure’ instigated.

Although the aeroplane had been straight, level and surprisingly stable – given the proximity of the storm – concern about overspeed was immediate and the PF (the least experienced F/O) throttled back and pulled back on the side stick. This instigated an almost 2000ft/min climb which continued – with the speed dropping all the time – to circa 38,000ft.

The PNF (the most experienced F/O) meantime was trying to make sense of what was happening as air data intermittently became ‘valid’ then ‘invalid’ again. All this time PF was pulling back on the sidestick almost, but not quite continuously. At or near the top of the climb, with speed bleeding away quite dangerously, PF hit TOGA – basically firewalling the throttles to a pre-set power output – which always pitches the aeroplane nose up unless counteracted, adding to the already dangerous Angle of Attack. The speed thus reduced still further and, with the stick still pulled back, the wings stalled and the aeroplane began to descend, very nose up.

PNF became very concerned, but equally confused as to what was happening, even though the altitude and vertical speed indications were working on his side, although ASI was not always valid. The stall warning operated, but neither pilot acknowledged it and no obvious action was taken immediately. As the speed dropped still further – below 60kts? – the stall warning stopped because it had fallen below its ‘authority band’. When PF several times released the sidestick, the aeroplane tried to level out and the speed temporarily rose, causing the stall warning to again sound as it re-entered its authority. This warning again drove PF to pull back on the sidestick, confusing PNF still further, if possible.

When the Captain returned from wherever in the aeroplane he had been, he elected to take the centre seat, not the LHS controls. He asked a number of questions, the answers to which served only to confuse any readings he might have taken from the instruments. During this time, PF was still pulling back on the sidestick and it was pretty much in this state that the aeroplane hit the sea at between 7000 and 10,000ft/min.

Apart from the initial blocked pitot/ Air Data failure – a condition experienced by 36 other aircraft of the same type – there was no other failure of an aircraft system.

I am no pilot, although I have flown light aircraft and have had a deep interest in aeroplanes and flying since I was eight, but even I know that pulling back continuously on the elevator control will, eventually kill you. I remember being deeply impressed by the low speed pass into steep, turning climbout of an early FBW Airbus at Farnborough, because I knew then, that to do what that pilot had just done in almost any other aeroplane, would certainly kill him. But I also know doing that at low altitude is quite a different thing from doing it at almost the maximum height for the weight.

In my really quite humble opinion, the Captain did not assert enough clear thinking authority and was quite ill advised to leave the cockpit when he did, but did not cause the accident. PNF had probably figured out what was happening, but could not square the symptoms with what he thought PF was doing. He assumed - and more or less had to assume – that PF was doing all the right things to control the aeroplane and when he did take control, a quirk of the stall warning system prompted PF to effectively snatch back control and keep pulling back. When the Captain returned, he too couldn’t even begin to understand what PF had been, and still was, doing.

The software protocols of the Airbus – an otherwise beautiful machine – have again been called into question and I don’t suppose for a moment the boys and girls in Boeing’s design/ build teams are going to say; “Tell you what, how ‘bout a sidestick upgrade for the 773, the 748 and the 787?” any time soon. For interested SLF, this accident is a very, very worrying revelation.

@ Conf iture:
 

Just a little bit different :O.....but you are absolutely right the Yellow line is fixed - like the normal speed reference - and the background is moving.
However the function remains the same......CAS vs AOA.


For now, an image from A380 AMM but too fast for AOA....

http://i474.photobucket.com/albums/r...9/BUSSA380.jpg

Ok illustration however this is a too fast indication.
For too slow, you would be in the bottom red sector.
The arrow shapes seem a bit counter intuitive since they bear opposite relationship to the direction you might want to move the nose to recover.

Glad they didn't put that in my flying machine for landing aboard ship.

MB, me too. Too much info to sort out when you are FUBARed. Keep it simple. Needle, ball and airspeed always worked in the past, now it is much more complex with computers flying most airplanes, especially the Airbus with pilots monitoring. Flying the 757 out of San Jose, Costa Rica one day with a check airman as my right seater on my initial captain check out our clearance got changed to an unlimited climb short cutting the level off and transition. He had the FMC so screwed up as I was making a right climbing turn and the FD was showing a left diving turn so ignored it until he caught up. Automation is fine if it is your helper, not your God. AF447 would not have happened with real aviators flying in my opinion.

Full back stick for over 3 minutes in a stall isn't what we are taught because it always kills you, guaranteed.

Well, I'm sure there's many of us [me for sure] that agree with all that. Unfortunately, not enough apparently. It's just too bad it's come to this. Glad I got out when I did !!

Me too. It was fun when we were flying. Now it looks like just a job with everything being monitored to verify you were stabilized below 1,000 etc. I liked it when you could do a roll over Mt Whitney inverted descending into Bishop in a charter jet. Guess the FAA can't violate me for something I did 35 years ago. It had no purpose, it was just fun.

A33Zab,
Thanks for the illustration, it does clarify things on the BUSS.
As Machinbird I have to say I find this indication for an extreme case somehow counter intuitive ... Would be curious to experiment it in a simulator.

Yes, I would gladly do the Mt Whitney maneuver again but am retired and do boats in the Keys now. I will always remember the event but it wasn't that big a deal. It sure was fun though. It is hard to screw up when once you clear the peak at 500 ft you have almost 10,000 ft below you in the valley.

With respect but the BUSS is not intended for Nimitzclass landings nor for inverted maneuvres......

Its only goal is to supply a speed vs AOA indication in - remote situations - when normal speed indications are not available.

IMO - Fly The Green - seems not be too difficult unless your colorblind and don't understand the meaning of FAST and SLOW.......

'Stalled' indication (some copy paste work)

http://i474.photobucket.com/albums/r...SSA380SLOW.jpg

A33Zab;

Thanks for the information on the BUSS.

Some time ago a post claimed that it displays AoA and nothing else. Would it be possible to retrieve information on how it works internally, i.e. what input data it uses and how these data are combined/processed to drive the display?

P.S.
See for example AF447 UAS by Joelle Barthe

That is a a horribly counterintuitive display!

and "SLOW (down)" or "(too) SLOW"

:confused:

I quite agree, Mac - placing that in front of our 447 crew would, I think, have merely hastened their demise (if that was possible)

HN39 - if I read you correctly there, the BUSS is 'deducing' AoA from inertial GS/FPA and attitude?

I have to admit, I didn't find the 'slow/fast' message one that leapt out and told me what to do without my first having to think about it - and when a pilot finds him/herself at 101% overload - (as virtually all of us would be in a situation like the one the AF FOs found themselves) - having to think about what the display is telling you is the very last thing you need.

I'll accept that the potential confusion might (should?) have been covered during conversion.

As the name says it is a back-up speed scale replacing the standard speed tape. The red-yellow-green tape moves in the same sense as the standard speed tape. There is a target speed indicated by a green area and triangle.

Numbers have simply been replaced by colors. How is that confusing or counterintuitive?

"Numbers have simply been replaced by colors. How is that confusing or counterintuitive"

Something like

GPS Speed 60kts

would be fairly attention getting....

Perhaps, but that has absolutely nothing to do with the BUSS or whether its use is intuitive or not.

No, according to Joelle Barthe's description, the Back-up Speed Scale indication "is based on angle of attack (AOA) sensor information".
Ground speed was 380 kts at the stall, 200 kts when stall warning was first lost, and never went below 100 kts.

HN39 - that is not what I read

they would probably never have seen the display since ( I believe) they would have had to select all ADRs off to get it, following a procedure - and they never even started any procedures.

However, by side-effect, BUSS might have saved them - if you believe off/on SW killed them, read on...

No, what it says is that the BUSS options routes AoA sensor data (raw, I guess) through the IR side (as well). BUSS can then use that AoA data, maybe in conjunction with inertials, even when the airdata side is shot (or off).

Now, the interesting thing is the stall warning comment - which says to me that as well as feeding the BUSS, the re-routed AoA signal from the new ADIRU also feeds the SW logic. Which, I think, means that SW would be continuous even if airdata calculations invalidate AoA data on that side of the ADIRU, and that would apply whether the BUSS is engaged (ADRs off) or not.

Not saying BUSS would have helped, but if anyone's thinking that BUSS wouldn't have helped because it's useless above FL26 etc. and that the on/off SW was the killer... then they might want to reconsider.

- thanks for clearing that up - not the best wording before!

http://i45.servimg.com/u/f45/11/75/17/84/ra_01910.png

Disregarding the attitude and GPS altitude here that don't necessarily fit the situation, my gut reaction, without too much thinking, seeing that big up red arrow would be to pull, at least initially.

I would like to know what the GPS speed is doing there in the 1st place. It does not tell you a darn thing about the aircraft as far a flying goes. The aircraft does not fly on GPS speed, nor does it fly on TAS (Unless you are talking MMO) BUT it does fly on IAS (or CAS if you are a purist) However a good AOA gauge should tell you everything you need to know, IF you knew a little about aerodynamics and knew how to read the gauge. (And pull yourself away from the FMS and actually fly the thing)

I don't think it's reading GPS Speed but rather GPS Altitude.

Speed is on the left side of the ADI and is replaced by a coloured tape indication.

On the right side we usually find altitude information and my guess is the 000 is sea level and the 010 is a thounsand feet with the 520 being mid way on that scale so it's a 520 foot GPS Altitude read out.

Edited... Just noticed is actually says GPS ALT at the bottom of the scale so my assumption is correct!

I agree with you however several people earlier mentioned GPS speed like it will tell you anything about aircraft performance.

This BUSS speed tape is confusing me big time! What exactly does 'SLOW' mean? What is the required response? Since we are talking AB, why does it not just say 'push your side stick forward and increase power'?

First you are confused and ask what it means only to show you know exactly what it means. A bit disingenous perhaps.

It is a speed tape, it operates as a speed tape. Are anybody here confused about how to read a speed tape or respond to it?

No experience. Red is bad. Speed up.

It's the arrow.

Up? What am I supposed to do?

I am still not understanding

It is driving me towards a 'speed' marker (green)?
It cannot itself compute speed due to failures?
How does it compute the green marker?
How does it know when I have got there?

As far as I can see this is AoA driven. The AoA is too high. What is needed is reduction in AoA in fairly short order, not just an increase in 'speed' towards a dubious green mark.

Would not a 'DOWN' arrow, flashing perhaps, on the AI be far simpler and realistic? After all is is a matter of simplicity to compute an AoA at any altitude/Mach at which the wing will unstall.

@BOAC:
 

NOT FAST

Fly the GREEN !!

And to bring the green down, you lower the nose......

If you see the 'SLOW' at the top of the scale (like the SLOW image), it is already saying "STALL STALL" for a while! (without interruptions)

Do anyone need more clues?

- I think that apparently we can all answer that, sadly.

If you see SLOW written on the road while driving your car what do you do?

Before you've managed to stall, it's more of a green band than a mark, which might be clearer what to do with it.

http://af447.typepad.com/.a/6a015392...28d2970d-500wi
[images credit to google search and a site I know nothing about - but it's not mine, just to be clear]

I think this is more or less an AoA indicator dressed up as a speed tape, but I think it does do the "compute an AoA at any altitude/Mach at which the wing will unstall" without the pilot having to remember or read tables (I guess).

By the time you've been pulling up through the stall warning for best part of a minute, it's going to look like the previously posted image and probably isn't helpful (green ? what green, where ?). But if you kept it in the green in the first place, you wouldn't have that problem.

Also, look at the conventional AoA gauge (which option AF didn't give them either):

http://af447.typepad.com/.a/6a015392...c632850970d-pi

At the same point in the timeline, that needle would have been firmly pegged at 25, and the size of the nose-down inputs they made would not have shifted it. Pull or push, the needle doesn't move - must be broken gauge... no ?

I've read the whole thread...:)

It seems that the crew simply had no understanding of the anatomy of a stall and therefore an AoA gauge may not have helped....was there pre-stall buffeting noted? for it seems that the A330 has very docile stall characteristics perhaps further misleading the crew

were AF's A330s actually equipped with 'BUSS'? I seemed to have missed where it was first mentioned in the thread

I don't think a competent pilot needs green arrows or any computer generated warnings to recover from a stall. It is so basic, you push down. Stall warning goes off, push down, works every time. Not with these clowns.

But you apparently don't have to be a pilot to "operate" an Airbus. A systems monitor will do. (Where did the German shepherd go? Oh, he's aft taking a whizz.)

The arrows appear to be an unfortunate choice of shape. The angled part of the arrow head is there to indicate whether you are just beginning to get into trouble (The tip of the arrow) or are fully in trouble tail over tea cup. They do not point to anything. It is not at all like an AOA indexer display (for those who know what that is).

The whole display is intended to look as much like the airspeed tape as possible. What I see as an issue with this approach is that this requires mental interpretation before you respond and it leans on the visual mode of information input like everything else on the 'Bus does. You will have to go through a thought process something like this:

• I'm getting near the 'Slow' arrow tip.
• Shall I add power or shall I push the nose down?

This is not the instinctive response those of us used to controlling AOA on approach have developed. Perhaps with enough training you could reverse the arrow indication mentally to move the nose the correct way, but then again, the 'Bus does not trim for speed so it is probably irrelevant in most cases.:hmm:

If it said "TOO FAST" and "TOO SLOW" it would be a lot clearer.

(The system knows what power the engines are putting out so maybe a "GET THE NOSE DOWN!" or "AOA TOO HIGH" would help too.....)

"I don't think a competent pilot needs green arrows or any computer generated warnings to recover from a stall. It is so basic, you push down. Stall warning goes off, push down, works every time. Not with these clowns."

Ptretty strong language considering you obviously haven't read the transcripts carefully enough to avoid putting your foot in your mouth.

If you take the trouble to read back you will see that the stall warning was off, UNTIL the nose was pushed forward to get out of the stall and at that point the stall warning came on.

In a pitch dark environment with everything seeming to be in conflict with everything you thought you understood about your aircraft's behaviour, perhaps it was all too easy to become a clown as you so eloquently and kindly put it.

Nojwod

Suggest YOU take your foot out of your mouth and re-read the transcript correctly!