ISIS
 

operate from -180 to +180 deg without deterioration.

http://i474.photobucket.com/albums/r...ab999/ISIS.jpg

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

3hole

My issues are of design, and the use of trim in this case. The PF commanded a climb up without the assistance of TRIM. So either by good luck, or a/c design, the THS stayed put, and he relied on elevators only.

At the top, the design input TRIM after the STALL. That seems unwise. Commanded to be sure, but none the less, it responded.

Several of his inputs served to lower the NOSE, and the STALL sounded, and he pulled up again.

So, once STALLED, there would not only seem to be no need for all NU from the THS, but that it would be highly dangerous to leave it there.
With a continuous STALL warning, one would hope a 'smart' a/c would return the THS to neutral, and allow the Pilot to recover with elevators.

Since the speeds had returned, it becomes especially apparent (to the aircraft) full up THS is not a good thing? No alert, no lowering the THS,

I could easily be the thick one here, and not you.

BUSS
 

Because UAS above FL 250 is considered transient. (caused by ICE)

One need to switch all 3 ADR P/B to OFF to activate BUSS scale.

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


change the aircraft configuration with wings level.

ISIS
 

A33Zab

Thank you for the details of the ISIS.

Could you add the size in inches (or mm) across the horizon, on the A/H part, so that I ( and others interested ) can adjust the scale on a monitor to be able to appreciate the instrument properly, as it might be viewed by a PF or PNF.

Let me try to understand: static air data is deleted from the system? Is that what is going on in this mode?

@LT:
 

A33Zab,
Thanks for the pics and the info.
Was that the fit of the AF447 A330?

So, you're advocating more automation? I'm not disagreeing here... I actually think all the information required to help the crew was available.

@LW50:
 

All ADR data is removed when ADRs are switched OFF.

With this BUSS option installed the AOA signal is fed into IR part of ADIRU,
IR part is available even with Air Data P/B off.
Don't know if more inputs are re-routed.

Is it anywhere referenced to use it in this situation? I could only find the following references, where the mechanical trim is desscribed as standby system in case of autotrim not being availble.


We know now that it might have helped to defuse the situation, how could the AF447 crew know? By not knowing the above references?

BUSS looks suspiciously like an AOA indexer.

I 'spect it's possible to have an indexer without shutting off the all the ADR's also.

We had an indexer in the training 727 we flew in the 80's, as well as a separate full-time AOA gauge.

Back to the future.

GY

Why wouldn't I be advocating for more automation? Or a better fit between what exists and the crew? Isn't that what this is all about?

If this airframe thinks enough of itself to protect the Rudder from inadvertent and harsh deflection, why would it not also want to protect itself from a TRIM trapped STALL?

If more than 8 degrees Rudder is not available at certain speeds, why would -13 PU be available? This is the "disconnect" I see from the outset of this thread, some logic here, some logic there, but something short of a continuous path in all directions.

It can be explained, but excuse me, pulling out the book and trying to get task specific recurrent in these conditions is insanity.

Knowledge plus experience equals wisdom. Substitute the word intuitive for wisdom, and there you go. Nothing that can occur on this aircraft can be permitted to be anything short of fluid, intuitive, and absolutely resistant to failure.

And that is the goal for when things are difficult, and doable; to say this argument is justifiable at all when problems of a familiar nature are involved is frankly outrageous.

It would be so nice to simply say PE. That is not any longer acceptable if one also expects to take credit for a failure resistant a/c when faults are so readily apparent?

We read here from guys who dream this stuff and live it. But there are real people here, and when some assume a posture of haughty self satisfaction that makes my fur hurt. The aircraft has holes, fill them.

all the best

A33ZAB,
Many thanks for the details of the ISIS.... looks and sounds very much like the SAARU in the triple 7. ...an everything-you-need-PFD-in-a-self-contained-box. Pop one of those in your little ragwing and you're home free!

Lyman.... Thanks for clarifying... One further comment, re: "If this airframe thinks enough of itself to protect the Rudder from inadvertent and harsh deflection, why would it not also want to protect itself from a TRIM trapped STALL?"
Because it is NOT "trapped" at all and there is no risk of structural damage as there is with the rudder.

Autotrim will do exactly the same on a boeing if the automatics are trying to maintain a flight path (with speed decreasing). See Schipol 737 and similar accidents/incidents.

Not a FBW issue, not an AB issue.

@3HL:
 

Minor correction:

-ISFD (Integrated Standby Flight Display) is the B. naming for ISIS.
-SAARU (Secondary Attitude Air data Reference Unit) is the "back-up" ADIRU of the777.

Exact! 1 standby instrument for whole fleet! A. thru Z.

@ChristiaanJ:
 

For ISIS, this ISIS was installed.
The BUSS option was NOT installed.

3hl

"No risk of damage, as with the Rudder?" Methinks the reason the THS was not deployed in the climb, and the elevators were not allowed to grab too much at a time had to do with protections.

The a/c at the bottom is not Damage?

The Rudder could disintegrate and part the VS, no crash. The THS, at full NU does not risk damage to the a/c? What if they had recovered aero flight, and the THS remained at -13 in a steep and high speed dive. No risk of damage? What a ride. ?

No inference of applicability, but look at this. The Rudder on AA587 tore the VS off (That was at <250 knots). If 447 had been in a recovery from Stall, the THS couldn't take the Tail off? I wouldn't place a bet.

http://i474.photobucket.com/albums/r.../BUSSScale.jpg
OK465I concur, Increasing AOA is toward the bottom. Oriented this way to make the display read in a manner similar to airspeed. Note: There are no numbers on the display.

Shouldn't the note at the bottom right say:
Red lower area corresponding to CAS < VLS

AF447 would have been at the bottom of the bottom red band while on its way down. Even three highly confused aviators would have understood their plight then.
Well, lets hope so.

It might have though...

I think a THS position trim clacker might well have alerted PNF to something going very awry in pitch much earlier and at least have glanced at the wheel or pointed the Captain to it immediately upon cockpit re-entry ?

.. even if PF himself was 'focused down a very narrow tunnel of perception' and would likely have been aurally blocking it out.

This is a drastic speed decrease, all the way down to a Stall condition, which is determined, and announced for 53 seconds by the "a/c's controls". Stall means fall !!!!

During these 53 seconds, of definite Stall Condition, determined by the a/c's computers, the THS went also under the a/c's computers control from -3 to -13 degree, which is MAX Nose Up, which is exactly the opposite of what in a Stall condition the pilot, or the computers should be commanding.

Personally, I would not consider this a FBW issue, in the sense of the FBW being a system in which the medium for transferring/passing bi-directionally control information is wire.

Is this really not an Issue??? if Boeing is doing to wrong thing, it is OK for AB to do the same?

Hi,

3holelover
I dunno about structural damage for THS .. but this ended with a big structural damage (the entire plane and it's load)
Maybe it's to understand Lyman prose as:
Why the THS still full up .. when the plane know (seem's the pilots no) he is in a full stall
Plane know this is a full stall .. plane know this is a full up THS deflection
The two are contradictory
Why not automatically reset the THS in a better position (with a warning to pilots) like it's a limitation for rudder deflection in particular situations ?

It's not "more automation". It is rather "right automation"!!!:D

All of the AOA information to avoid this crash are present in every modern Airbus aircraft, as standard equipment. In addition to the stall warning and the VLS/Alpha Prot, Alpha max scale on the left side of the PFD, there is an even better, direct measure of AOA, even though it does not come from the AOA installed on the aircraft (3 on the 320 series).

The problem is, no one is trained to use it.

What is AOA? It is the angular difference between the relative wind and the longitudinal axis of the aircraft (chord of the wing, more specifically). In lay-mans terms (I am one), it is the difference between where the airplane is pointed, and where it is going, about the lateral axis.

Call up the "bird". With the wings level, the AOA is the vertical distance from the pitch bars (where the aircraft is pointed), and the "bird" (where the aircraft is actually going). Non-wings level, you visually drop a perpendicular from the plane of the pitch bars to the bird. That distance, measured on the PFD, is your AOA, and would have prevented this crash.

I know some engineer (I am one also) will say that this AOA measurement is not "perfect", but neither is an AOA gauge. Not even close. Just as IVSI is more useful than a pure VSI, this IRU based measurement is actually more user friendly to the pilot, more reliable, and "cleaner". And it is EXACTLY where the pilot is staring to control the aircraft, there is no other "scan" to learn.

On a 320 series, cruise is usually 2-3 degrees up, green dot, S, and F speed are 7-8, Stall warning (in alternate law in the sim) comes on at 10-12 degrees with the stall happening a bit above that. In level flight this is the "pitch attitude". In non-level flight, this is the perpendicular distance from the pitch bars to the bird. Icing doesn't affect the IRU's and there are 3 of them on the 320.

We were just not trained to use this.

The pilot(s) did call up the bird, FPV, but it was not working. That from ACARS, I think.

It seems to me....
...that many of you are looking for all sorts of things that either automation or aircraft systems of one sort or another could have done/be done in future to help in this situation, while forgetting that flying is an inherently dangerous undertaking that has, for eons now, been made rather routine by simply training pilots how to handle their machines.

Yes, you could automate the hell out of the thing, but at some point, somehow, all that automation could easily be counter productive.... Can't you imagine a situation, for instance, where a stab that returns to neutral automatically, might be a bad thing? Maybe it's best to leave the aircraft handling to pilots?
Maybe it's better to train pilots to fly, rather than manage computers?

This aircraft didn't fail. One system alone had what should have been a non earth shattering, temporary fault, due to ice crystals, but then it's pilot(s) failed.

Yes, as I said earlier, I agree there are probably some tweaks that might make sense, but I don't think anyone should get carried away in burying human failure with more complexity and more tacked-on, automated garbage that will wind up fouling somebody else down the road.

As yet, nobody wants to fly in a fully automated, pilotless aircraft. All we need, to get folks to their destination safely, in any serviceable aircraft, is a pilot who knows his machine, and knows how to fly it. That simple formula has been proven to be quite safe. What was missing here wasn't more junk, it was human knowledge and skill. Airmanship.

Does anyone here really believe an aircraft can be made that won't stall? My limited knowledge of aerodynamics and physics tells me, with current aircraft design, that's not possible. So pilots had better know how to recognize and correct for a stall. The surprise to me here, has been learning that hasn't been universally the case. That, imho, needs immediate correction!

Flying is inherently dangerous, but how a/c's got better and better from their original inception, was also from understanding the shortcomings and improving or eliminating them. Combining a better training with an improved a/c is a better combination than just training.
The current model is only going to progress on even further automation.
What is needed, is to eliminate or minimize the shortcomings in the design, which will reduce the risks of manual flying..
Certain elements of the current design had their own contribution to the failure of the pilots. Improving those elements will only make the design, the a/c better, and the flying safer.

don't see it as more complexity, but exactly the opposite less complexity. I think much of the current complexity is so - complex - because it is counter-intuitive. Making it more intuitive is making it simpler and easier for the pilots to quickly understand. From the information regarding the active stick position/motion shared directly among the pilots, to a more logical Stall Warning, to an Autotrim that locks, making sense in a Stall condition... etc.

We've been at this since the first passenger airplane: we have continuously complemented airplane shortcomings with pilot talent and training. But... in the same time we have improved a/c's after each accident that made us understand better its shortcomings.

This a/c showed a remarkable stability and extraordinary structural integrity during the Stall. That is exceptional.

It would be nice to be able to make it so it would not stall. But I don't see that as an attainable goal.

However, it is achievable to improve the logic, the algorithms, the software subsystem, so that remarkable stability, and extraordinary structural integrity is not wasted if in a stall, by making the stall avoidance better, and stall recovery easier.

3Hole
Don't you see a problem with an aircraft with an automatic trim system that trims silently? For years we have had alerting devices on THS trim movement (clackers & whoolers) to let you know the thing is moving. Then comes the new guy on the block with a "better" idea. (Airbus)

Couldn't they have seen the trim moving in their peripheral vision? Maybe, maybe not. There were serious problems in the cockpit that night that demanded attention.

If someone in the cockpit had noted that trim running up, they could have stopped it just like you would in a 707. Grab the trim wheel. Without all that nose up trim, the PF would have had serious trouble holding the nose up against the natural aerodynamic tendencies of the basic aircraft to drop its nose as it slowed. The PNF could have largely overridden the inept handling of the PF if it had occurred to him.

But no one saw the trim move. No one heard it move. If they had thought about it, they should have anticipated it moving, but they had other problems and it bit them.

We have now lost two Airbus aircraft due to lack of crew awareness of trim position and (other problems). Fixing the trim system to provide better motion alerting should be easy. It has plenty of precedents and it is not rocket sciences.

Yessir Machinebird. I agree. That'd be a worthwhile "tweak".

Machinbird,

It is clear that the silent trim was not helpful in that stressful situation, and you've eloquently explained that.

But I am going further.

The trim should have stopped, or should have never happen during the Stall.

The a/c computers determined that the a/c was in a Stall, and sounded the alarm for 53 seconds.

During those very 53 seconds, the autotrim moved silently the THS to its extreme position of -13 degrees of max NU.

It is clear that there was a logical disconnect between the Stall and Autotrim. Had there been a logical connection, with a locking of the THS in Neutral, it would have certainly helped the pilots, the recovery from Stall.

During the rest of the descent, the Stall Warning sounded another 8 times, and the THS has remained in its max NU during all those 8 Stall Warnings.

Should the THS have returned to Neutral at the first Stall Warning out of those 8, the recovery would have been helped.

Hi,

I will repeat this X1000 if needed:
The Pitot tube was not faulty
As many here like write about the plane ...
The pitot tube operated normally .. as required by its specifications and certifications
The problem is that the measuring instrument has been used outside his operating range
Ice crystals is not a area for use Pitot tube .. it's not in the certifications
As the plane went well until he was out of its flight envelop
As the pilots went well .. until they were (or put their self) in a situation out of their skill

Airtren,
We are not too far apart in viewpoint. The nose up trim should have stopped running well before reaching alpha stall in any case.

Hi,


Pending a resolution of Airbus engineers and certification in 10 years .. pilots can easily solve the problem of silent motion trim
No rocket sciences indeed ...

http://i.imgur.com/ZCNhm.jpg

I think you have to be careful what you ask for.

- Making the trim operation audible (this seems like a no brainer). Relying on the visual cues seems over optimistic, particularly when things have already gone pear-shaped.

- Auto-neutralizing trim state in stall warning. Unless I am misunderstanding things here, the trim was not what stood this aircraft on it's tail, it was the PF elevator input. My understanding is that the elevators alone can override the THS. Would neutralizing the THS have been the key here to save the aircraft? I don't think so at all. The PF (and PNF+Captain) at no point acknowledged the STALL. In fact the PF was demanding NU pitch for most of the time - he got what he asked for. Would the PF have NOT demanded NU if the THS has not followed his demands... or had untrimmed? Doubtful.

I do believe a better more explicit YOU ARE STALLED alerting system can be implemented. The aircraft knows enough from AoA, Vertical Speed and perhaps Ground Speed to be able to state quite happily "You are stalled and plummeting to certain doom - how about reducing AoA with a bit of nose down old chap...". OK may be that's a bit glib, but something beyond the existing Stall Warning audible ---> "AIRCRAFT STALLED! AIRCRAFT STALLED! REDUCE AoA!"

jcjeant


I believe that you are too quick to defend the pitot tube as not being at fault. The earlier poster had specifically stated "pitot system"

It was the speed measuring system at fault (the pitot was only a part of it). Of course you are correct that such a system fault was presumed at aircraft certification..

At this point the assumption is that a combination of systems or unlikely events probably caused the accident. The issue now is what needs to be fixed to prevent another accident.

It is not enough to change the pitot tube alone when clearly a system fault was not accomodated to continued safe flight and landing.

Hi Garage Years,

I agree. It is pointless adding more audible warnings to already saturated pilots.
Altitude Alert, Multiple Ecam Dings, Autopilot Disconnect, Thrust Lock Dings etc. + "Stall Stall".

A different warning / alert is required to elevate it to the highest attention getter - like the discrete stall warning vibrations through the control column on other aircraft. It simulates the natural buffet onset. There is no other warning like it.
The audible "Stall Stall" seems to have been filtered out of all 3 crew members sensory perception - no one commented on it.

The "THS at max NU" was a major immediate reducing - if not neutralizing - factor of the effectiveness of the "Elevators ND (even if at max ND)".

The "THS Neutral + Elevators ND" would have allowed an immediate more effective Elevators ND, compared with the "THS max NU + Elevators ND".

On the Stall Warning, as it can be seen from my posts on the topic, we're on the same page.

Retired F4

As caveated by our contributor, the scenario might not have been similar enough to have triggered a "this is one of those situations" responses from the crew.

What I was trying to get at (damping and pitch rate limiting functions considered) is that I think the pitch rates would be a little faster (you'd have to wait less time) if you moved the THS with the wheels (even when auto trim is functioning, which it should in Alt 2) rather than wait for the elevator THS linkage to induce THS nose down (THS actually up a bit) commands.

But if one doesn't train it, one probably doesn't resort to such actionns when things get hairy in the cockpit.

How hard would it be to just post a little animated graphic of the fin/stab configuration? Something that can be instantly visually absorbed? "Wow that can't be right.."

Hi,

lomapaseao
The Pitot tube is not only a part of it .. it's the most important part of it
Remove from the plane the Pitot tube and you have no more speed measuring system at all
The AF447 case proven this.
The best solution at today date is to use the Pitot tube in his domain of certification
So .. dont fly in ice crystal area ..
If not able to detect ice crystal .. don't fly in the areas when this is the possibility to meet them .. forget fuel sparing .. fly safe !

Lonewolf_50
 

I´m fully with you at that, but:
I wanted to make it clear, that i couldn´t find a reference in the valid publications for aircrew (FCOM, FTCOM) and maintenance (LTTM), which even would give a hint to use manual trim in such cases.

So how should the crew know about it?
Why should it have been trained?
Did anybody knew it before AF447?
On what basis would it be trained now?

We had the manual trim discussion before on the older thread, but there everybody asssumed direct law, where only manual trim is available.

We even dont know, how the system will behave after manual trim has been applied despite autotrim still active.

(Ref. LTTM)

What happens after release (which i interpret as not turning the wheel any more)? I couldn´t find anything in the manuals.

Point is: We know now, that trimming the THS manually would have helped to bring the nose down. But we dont know consequences in other circumstances, as there seems to be no documentation concerning such a usage. So how can one train for it without documentation?