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Lonewolf_50
17th Jun 2011, 18:36
It seems most likely,finally, that the Pf was indeed the least experienced f/o ,in the rhs (frozen atpl) This leaves the other f/o as pnf in the lhs.acting as 'commander' in the absence of the captain.with all the responsibilities that involves.
no comment, but this sets up ...
it seems pretty clear that he had had no training whatsoever in sorting out problems of this magnitude,especially from the lhs.
I do not find your assertion valid, as I don't know what you base your "all or nothing" reasoning on.

Training and qualification are not a step function, they are part of a continuum.

I suggest that you go back and look up the experience base of the two FOs again.
probably never ever had to recover from a fully developed stall at high level in the sim.
Well, who has?

If you head over to the Tech Log threads on this mishap, and a thread on airliner stalls, you will find some people who understand simulation, its uses, and simulator programming issues.

Therein lies your answer: at this point, the fully developed stall, in the sim, isn't necessarily a valid training scenario.

Should it be? An open and much discussed question.

Zorin_75
17th Jun 2011, 19:01
It seems most likely,finally, that the Pf was indeed the least experienced f/o ,in the rhs (frozen atpl)
Based on what?

takata
17th Jun 2011, 19:24
Original search finds Captain's body unsecured.
After wreck discovered, the PF and PNF are found secured to their seats.
Where did you read that from the investigation?
Most rumors about those body state/identity are to be considered what they really are: "rumors". Some were also proved wrong with later official release. Captain body was actually recovered floating in June 2009, but did you really heard a single detail about his body state? Be sure that you won't find any information about that because none was revealed.
On the same subject, investigators (BEA) only commented about the deep recovery of some pieces of the cockpit (3 seats) without mentioning anything about their occupant. Hence, everything else is still pure speculation.

GerardC
17th Jun 2011, 19:45
Camel...sorting out problems of this magnitude,especially from the lhs. Probably never ever had to recover from a fully developed stall at high level in the simSorry to confess, after being a professional pilot for 42 years and a captain for 21 years, I "never ever" have been trained to "recover [a heavy jet] from a fully developed stall at high level in the sim".
Congratulations if your airline routinely trains you to "recover from a fully developed stall at high level in the sim".
Please, feel free to explain every professional pilot here the easy way out of a "fully developed stall at high level" in a heavy jet (let alone a FBW one).
As far as I know, the only crew to survive a "fully developed stall at high level" has been the Air China one, decades ago, recovering a stalled 742 by extending the landing gear well above the placard speed (deep respect to these guys :D...).

petermcleland
17th Jun 2011, 20:08
As far as I know, the only crew to survive a "fully developed stall at high level" has been the Air China one, decades ago, recovering a stalled 742 by extending the landing gear well above the placard speed (deep respect to these guys :D...).

Deep Stalled at way above Gear Placard speed?...I very much doubt that you could get the IAS up that high in a "Deep Stalled" aircraft.

Zorin_75
17th Jun 2011, 20:50
As far as I know, the only crew to survive a "fully developed stall at high level" has been the Air China one, decades ago, recovering a stalled 742 by extending the landing gear well above the placard speed (deep respect to these guys :D...).
IIRC they managed to end up in an inverted dive at very close to 1.0M after failure of one engine. The landing gear wasn't deployed by the crew but it extended by itself as the locks couldn't withstand the 5g they were pulling. It's a miracle that the rest of the plane could, for the most part.

GerardC
17th Jun 2011, 21:20
Sorry, my mistake, landing gear extended "by G force", but this crew did survive a "deep stall" :
"The lowest indicated airspeeds were recorded between 1016:14 and 1016:22. During this period, speeds between 54 KIAS and 110 KIAS were recorded."
(see NTSB accident report: China Airlines B747SP Loss of Power and Inflight Upset (http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/ChinaAir/AAR8603.html))

OK465
17th Jun 2011, 21:38
I think this is where the term, "Chinese Fire Drill", comes from?

predictorM9
18th Jun 2011, 08:42
Hello,

I'm not a professionnal pilot, but I have some basic understanding of physics and aerodynamics. I have multiple questions regarding AF 447:

First: how can the angle of attack can be that high (above 35 degrees)? Is there enough authority from the elevators or THS to maintain such a high angle?

Second: was this stall recoverable at all? If the AOA is that high, shouldn't the elevators be in the wake of the wing (and thus be useless)? Is this some kind of stable stall configuration?

Third: How could the captain maintain an almost zero roll (+- a few degrees) in such a stall? I have stalled before in gliders (I know this is not the same size weight altitude etc so it does not fully), and they tend to roll heavily on one side or another (it is very difficult to keep the wings level). I understand the BEA report on the 40 degrees roll oscillations when the stall started (which is for me consistent with a stall), but I don't understand why these large oscillations didn't persist

Fourth: why did the THS changed its position from +3 to +13 degrees at all? After all, wasn't the autotrim disconnected with the switch to alternate law? How can the computers give up because of lack of data, and still trim the plane (and using what information?)

aterpster
18th Jun 2011, 08:59
Zorin 75:

IIRC they managed to end up in an inverted dive at very close to 1.0M after failure of one engine. The landing gear wasn't deployed by the crew but it extended by itself as the locks couldn't withstand the 5g they were pulling. It's a miracle that the rest of the plane could, for the most part.

The flight engineer tried to tell the captain he had lost an engine. The captain couldn't figure it out. The autopilot put in more and more aileron until its limits were reached, at which point it disconnected and induced a wing over.

As you know part of the tail came off during the ensuing high speed dive/high G recovery. The fact it didn't end up in the ocean was a tribute to Boeing, not the clueless pilots.

Zorin_75
18th Jun 2011, 09:06
Here's the dramatic version:
ovQDYpWYpew
PE92xBmj2Uc
ovhcDDxDuq8

Perhaps this incident isn't that far off topic at all. It too starts out with a comparatively benign failure. The PF is fixated on one problem (speed), breaks his scan and misses the plane's attitude, which is starting to roll. The a/p tries to correct for this, and when the PF takes over manual control he's taken by surprise. At this point they're so disoriented that they rather believe all their ADIs to have failed than actually be doing an aileron roll...

tigger1965
18th Jun 2011, 09:45
Extraordinary recovery and landing by the Air China crew.

But am i correct i thinnking that the Air France deep stall would have been much harder still to recover, being in a nose up attitude?

glad rag
18th Jun 2011, 10:28
# 1756 refers.

petermcleland
18th Jun 2011, 10:44
It might easily be true that a recovery from that deep stall was impossible...I spent the last eleven years of my career in command of a jet airliner that was known to be impossible to recover from a deep stall...A stall recovery was only achievable from the early stages of the stall.

mm43
18th Jun 2011, 10:59
predictorM9;

I suggest you have a look at post #1817 AF447 Thread No.3 (http://www.pprune.org/tech-log/452836-af447-thread-no-3-a-91.html#post6507819) and check out the two links at the bottom.

The aircraft appeared to have a tendency to roll to the right, though this shouldn't have been due to fuel imbalance as that is equalized automatically. There is nothing in the BEA update to suggest a reason for the asymmetry.

Even with the THS trimmed 13° NU, the elevators will have had enough authority to cause a ND trim at IAS < 180 KTS. When that was done the stall warning sounded and the sidestick inputs were reverted to NU. The flight law was ALT 2 and the autotrim can be overridden by constant sidestick inputs or the mechanical trim wheel.

Once the aircraft had fully stalled at FL380, the AoA value was deemed invalid as the mean CAS was < 60 KTS. So you can see that after stalling they found themselves on the wrong side of the stall warning and didn't realize it.

Essentially the aircraft maintained >15° NU attitude all the way down and as the air became denser the forward momentum was reduced, the AoA increased while the RoD remained near constant.

predictorM9
18th Jun 2011, 12:44
Thanks MM43, I understand better about the stability.
But still, in post 1393 it says that the elevators are also fully stalled, so can they still have some nose down authority? And also, what happened regarding the THS? From the BEA report, the plane was trimmed up, but after the switch to alternate law. Who was trimming it? The pilots or the autopilot (which should have been disconnected...).

mm43
18th Jun 2011, 13:28
predictorM9; But still, in post 1393 it says that the elevators are also fully stalled, so can they still have some nose down authority?The elevators were max NU and held the attitude at +16°. I wouldn't get too excited about the stalled tailplane, as the drag caused by the vortex was assisting its lift, and airflow over the aerofoil, i.e. the THS and/or elevators, need only act as a lever to force the NU or ND as required.

Suggest you have a good look at some of the posts in the Tech Log to get an understanding of how the alpha protections and the associated autotrim work in Normal and Alternate Laws. Have a read of the Andy Tracy document at A340 - A330 Control: Flight & Laws (http://countjustonce.com/a330/a330-flight-laws.html), which is a summary of the basic flight laws for the A330 and A340.

takata
18th Jun 2011, 13:37
Hi predictorM9,
First: how can the angle of attack can be that high (above 35 degrees)? Is there enough authority from the elevators or THS to maintain such a high angle?
Once stalled, pitch reached about 16 degrees, but AOA increased to above 60 degrees (about 61 at impact time). This change is due to the loss of horizontal speed, not to the THS or elevators position which only maintained the nose up attitude and killed most of the remaining airspeed due to added drag.
Second: was this stall recoverable at all? If the AOA is that high, shouldn't the elevators be in the wake of the wing (and thus be useless)? Is this some kind of stable stall configuration?
Who know exactly what kind of recovery was attempted? Nonetheless, it seems that some control (roll, pitch) could still be applied with some effects once stalled. We'll see that in detail when more DFDR data would be released.
Third: How could the captain maintain an almost zero roll (+- a few degrees) in such a stall? I have stalled before in gliders (I know this is not the same size weight altitude etc so it does not fully), and they tend to roll heavily on one side or another (it is very difficult to keep the wings level). I understand the BEA report on the 40 degrees roll oscillations when the stall started (which is for me consistent with a stall), but I don't understand why these large oscillations didn't persist
Oscillations where registered before the stall and there isn't that much info about the later phase once she was effectively stalled, beside indications that the roll tendency was stabilized (likely meaning that ailerons imputs were still effective). The stall warning (SW) start well before entering a stall and it will even start earlier once an Alternate Law is triggered (due to the safe flight enveloppe reduction). Same about an overspeed warning (if airspeed was still computed) which would be reduced from Mach .86 to Mach .82. Despite the early SW (possibly due to pilot imputs or turbulences, hence g-induced in relation to AOA and Mach), she climbed 3,000 ft before effectively beginning to stall.
Fourth: why did the THS changed its position from +3 to +13 degrees at all? After all, wasn't the autotrim disconnected with the switch to alternate law? How can the computers give up because of lack of data, and still trim the plane (and using what information?)
Alternate Law do not disable auto-trimming in manual pitch as it is only g-load related; consequently, it will follow any pilot pitch imput until an abnormal condition will be declared. On the other hand, FMGECs (flight computers used by autopilot) are not active anymore once ALT2 is triggered due to an unreliable airspeed situation: AP can not be re-engaged until this situation would be cleared (which imply that two ADRs must be valid following their logic).

HazelNuts39
18th Jun 2011, 15:03
she climbed 3,000 ft before effectively beginning to stall. Perhaps not really important in the overall context of your very informative post, but the airplane must have begun to stall shortly before reaching its apogee at FL380, and was well into a fully developed stall with AoA=16 degrees at less than one g when it got to FL380.

aguadalte
18th Jun 2011, 17:41
It seems most likely,finally, that the Pf was indeed the least experienced f/o ,in the rhs (frozen atpl)
Camel:
This leaves the other f/o as pnf in the lhs.acting as 'commander' in the absence of the captain.with all the responsibilities that involves.

it seems pretty clear that he had had no training whatsoever in sorting out problems of this magnitude,especially from the lhs.probably never ever had to recover from a fully developed stall at high level in the sim .

how can this be ? something is seriously amiss here ,in the training department?

In my company the pilot in charge to replace the Captain's functions is the Senior F/O and his assigned position in the cockpit is CM2 (RHS). He is the Pilot Flying for the time the Captain is not on his seat. The "second" First/Officer will seat on the LHS to perform PNF actions, i.e., comms, papers and assistance to the PF. The "second" First/Officer is trained to execute several maneuvers (Emmergency Descent, Engine Failures, etc.) in order to be able to cope with any situation arising at a time when the First Officer may be absent for physiological reasons. He is otherwise never the pilot flying.

In the case of Air France, I am not sure of the practice or company policy, but I am sure they will have it written in their OM. (Remember that the word bureaucracy comes from a French word bureaucratie) :8

I tend to believe that the Pilot Flying would be the Senior First Officer and that he would be seated on his "natural", "most used to" RHS. Otherwise, I would say that, AF would have to change its policies.

jcjeant
18th Jun 2011, 18:16
Hi,

A doc ......

YouTube - &#x202a;Airbus Fly By Wire Demo&#x202c;&rlm;

cwatters
18th Jun 2011, 19:18
The elevators were max NU and held the attitude at +16°. I wouldn't get too excited about the stalled tailplane, as the drag caused by the vortex was assisting its lift, and airflow over the aerofoil, i.e. the THS and/or elevators, need only act as a lever to force the NU or ND as required.


Interesting comment. When down elevator is applied what happens to the "vortex" drag that is "assisting it's lift"? Seems to me it would reduce.

jcjeant
18th Jun 2011, 22:56
Hi,

Nouvelles de Françe
News from France

L' interview du mois - Laengy Jo (http://www.iutcolmar.uha.fr/internet/recherche/Jcerdacc.nsf/00b1baa6c5288743c1257711002d2c42/f7f565452eec5570c125789600425aee?OpenDocument)

Nous sommes sur la même longueur d'ondes que le BEA sauf que ce dernier s'est étonné devant la presse le jour même pourquoi les pilotes avaient cabré l'appareil. Ce n'était pas honnête de la part du BEA. Cela demande à être analysé. Est-ce que mécaniquement ils pouvaient faire autre chose? On ne sait pas. Alors pour l'instant, il faut se garder de toute interprétation et de tout commentaire.

I let for you the translation duty ......

mm43
19th Jun 2011, 05:04
When down elevator is applied what happens to the "vortex" drag that is "assisting it's lift"?Probably easier to to think of the "bigger barn-door" versus the "smaller barn-door". A bigger slab will be more effective than a smaller slab.

http://oi54.tinypic.com/pp2sz.jpg

A better understanding of what the above graphic represents may be obtained by viewing the initial graphic at post #1817 - AF447 Thread No.3 (http://www.pprune.org/tech-log/452836-af447-thread-no-3-a-91.html#post6507819). Also check out post #1786 (http://www.pprune.org/rumours-news/447730-af447-wreckage-found-90.html#post6523773) in this thread.

EDIT :: The graphic has been changed to show a THS airfoil with bottom camber. Also, the local Angle of Incidence is shown.

The Ancient Geek
19th Jun 2011, 10:44
Thanks for the diagrams and all of the other information.

However, I am still trying to figure out how any pilot would not realise that holding full backstick on anything other than an AN-2 (*) is a bad idea and is sure to get you into big trouble.

Is the full backstick recording actually true or is this an anomaly caused by some deeper issue ?. Did the PF *really* hold full backstick for almost 4 minutes, this seems hard to believe.

(*) The AN-2 is a special case, if the engine fails SOP is full backstick which pops the slats and causes the aircraft to mush slowly into the ground at parachute speed. - Only possible on a draggy old soviet STOL fossil.

aram
19th Jun 2011, 11:33
mm43;

i'm not a pilot - so maybe that's why your graphic confuses me: there's a 13 deg nu-angle depicted between "attitude" and "chord" - to me, this looks as if ' the nose would go up, while wing doesn't move with it' - should the chord not only differ from the attitude by about 3 deg?

RetiredF4
19th Jun 2011, 11:58
nose goes up, wing stays down??
mm43;

i'm not a pilot - so maybe that's why your graphic confuses me: there's a 13 deg nu-angle depicted between "attitude" and "chord" - to me, this looks as if ' the nose would go up, while wing doesn't move with it' - should the chord not only differ from the attitude by about 3 deg?

The THS (trimmable horizontal stabilator) was trimmed 13° to the aircraft nose up position. To get an aircraft nose up command, the THS is trimmed 13° down (leading edge of the THS down). The line "Attitude" basically represents the fuselage, and the zero position of the THS.

I think that should explain it.

aram
19th Jun 2011, 12:20
The line "Attitude" basically represents the fuselagethats exactly my understanding, RetiredF4 - now look at the graphic again: the 'fuselage' is in a 13 deg nose-up attitude, while the wing profile (chord line) is shown almost horizontally - imho, that can't go together - wouldn't the whole wing profile have to be shown pointing upward, in accordance with the 13 deg nose up attitude (apart from the small 3 deg difference between the two)?

EDIT: basic question: is the depicted profile representing the main wing, or just the horizontal stabilizer with trimmable section? - mayby that would explain my misunderstanding.

Chris Scott
19th Jun 2011, 12:36
Quote from mm43:
The elevators were max NU and held the attitude at +16°.

Quote from The Ancient Geek
I am still trying to figure out how any pilot would not realise that holding full backstick on anything other than an AN-2 (*) is a bad idea and is sure to get you into big trouble.

As mm43 is now likely to be asleep, I'll offer my twopence-worth. The BEA does not say the PF had selected full back-stick, but you must remember that the FBW had only partially degraded to Pitch-Alternate Law – not Direct Law. (If it had degraded to Direct law, stick-to-elevator would have been in operation. But in Pitch-Alternate, that is not the way it works.)

Even a neutral (in pitch) stick would have resulted in full up-elevator, because the FBW would have still been trying to achieve (maintain) 1G, and the THS seems to have reached full nose-up trim (13NU) at around the apogee-point. Normally, Pitch-Alternate has a stall-protection function, based on AoA. But the AoA readings had been ruled invalid earlier because of the (false) low-airspeed data.

Although it was inevitably unsuccessful in maintaining 1G, and the aircraft's trajectory had become semi-ballistic, the system would have tried its best. In so doing, it would have selected full up-elevator. It no longer had recourse to the THS, which had reached full-travel.

Remember, the vertical-G that the system tries to achieve is governed by the position of the sidestick, unless protections come into operation.

Chris Scott
19th Jun 2011, 12:49
aram,

You're only looking at the THS and elevators in mm43's super graphic. The chord line is the THS chord line. As you say, the wing chord-line would be at least 13deg higher. (I say "at least", because it depends on the "riggers angle of incidence" of the wing, relative to the longitudinal axis of the aeroplane. Some aeroplanes have a couple of degrees positive, the B707 being an example. Don't know what the A330's is.) For all intents and purposes, the line marked "Attitude", represents the wing-chord angle.

By the way, the whiole of the HS hinges (at its aft spar): hence "Trimmable Horizontal Stabiliser" (THS). As RetiredF4 and mm43 have said, the THS aerofoil can be considered to be mounted upside down, because its normal role is to produce lift in the downward direction. Hence the camber is actually greater on its bottom surface than its top surface. mm43's graphic is not intended to show that. Look at Conf_iture's photos here (http://www.pprune.org/tech-log/454653-af-447-thread-no-4-a-7.html#post6520727) in Tech Log.


Hope this helps.

aram
19th Jun 2011, 13:07
Chris Scott;

this indeed helps a lot - thank you for clarification. apologies for my fundamental misunderstanding(s) in the first place and for inadvertently having produced some clutter - i appreciate the valuable contributions by pilots and other pros on this forum.

Jig Peter
19th Jun 2011, 13:43
Thanks for your post 1767 - nice to hear some once-familiar voices !

aguadalte
19th Jun 2011, 14:02
RetiredF4 mm43
Good graphic, except that the profile is upside down. On the THS the curvature of the profile is on the downside.

I'm sorry to disagree, but I do believe that the mm43 profile is correct. The THS on almost heavy aircraft has a positive profile. That is why the "ground set" (http://www.travel-images.com/photo-dominican214.html)is minus 4º, (zero lift). Remember that the A330/340 family (and others) carry 5 Ton of fuel in the trim tank (that is why THS, with trim tank full, flies at minus 3º - only 1º above ground zero set - and this is done) to save about 3% of fuel, due to less drag.
Also, the reason why the elevator flips 30º up and only 15º down is due to the fact that it needs a higher degree up in order to destroy positive lift created by the THS curved wing.

Chris Scott
19th Jun 2011, 14:11
aguadalte,

I respectfully disagree!

aguadalte
19th Jun 2011, 14:38
Chris Scott:
I know you do. When I made my studies, conventional stabilizers were designed to produce negative lift. At that time, there were no preoccupations with fuel saving or drag reductions...
I think (although not sure) that, with the advent of CGCC computers and in order to save fuel, that new big jets suffered a slight redesign of the stab profile. New jets are not designed to be stable. They are designed to fly with near zero trimming. It is therefore a waste of lift and fuel, to design stabs producing negative lift, together with 5 Ton of Fuel...
I will pay closer attention next time I fly and will take a closer look at the stab profile.:)

DozyWannabe
19th Jun 2011, 15:58
Even a neutral (in pitch) stick would have resulted in full up-elevator, because the FBW would have still been trying to achieve (maintain) 1G, and the THS seems to have reached full nose-up trim (13NU) at around the apogee-point. Normally, Pitch-Alternate has a stall-protection function, based on AoA. But the AoA readings had been ruled invalid earlier because of the (false) low-airspeed data.

Although it was inevitably unsuccessful in maintaining 1G, and the aircraft's trajectory had become semi-ballistic, the system would have tried its best. In so doing, it would have selected full up-elevator. It no longer had recourse to the THS, which had reached full-travel.

Hi Chris,

I still find it hard to believe that given the amount of thought put into systems degradation upon loss of air data the "G-loading" system would still be in effect (after all, loss of air data will disconnect the FMC because it can no longer function reliably - I find it hard to believe they'd still have the FCU systems trying to work with spurious data). We'd need someone who worked on the system directly to clarify though, as I have no data. On the other thread we discussed the behaviour of the control laws as speed decays, where "stick-neutral" gradually transitions from "G-loading" to "zero pitch". There's also the BEA note which seems to be pretty sure that the PF was commanding a lot of nose-up.

Castle Don
19th Jun 2011, 16:38
I assume the lower red vector is the Relative Wind? If so, wouldn't that make the AoA incorrect?

RetiredF4
19th Jun 2011, 18:09
aquadalte
Chris Scott:
I know you do. When I made my studies, conventional stabilizers were designed to produce negative lift. At that time, there were no preoccupations with fuel saving or drag reductions...
I think (although not sure) that, with the advent of CGCC computers and in order to save fuel, that new big jets suffered a slight redesign of the stab profile. New jets are not designed to be stable. They are designed to fly with near zero trimming. It is therefore a waste of lift and fuel, to design stabs producing negative lift, together with 5 Ton of Fuel...
I will pay closer attention next time I fly and will take a closer look at the stab profile.

No need to wait, look at the pictures Confiture posted in the other AF447 thread (http://www.pprune.org/6520727-post139.html).

FBw could not change the laws of physics, if you use cambered airfoils, the lift of the wing has to be upward and that of the tail downward at 0° AOA to have some kind of positive stability, when the confusers go on leave.

RetiredF4
19th Jun 2011, 20:01
In search for the correct profile of the THS to this post of mm43 (http://www.pprune.org/rumours-news/447730-af447-wreckage-found-89.html#post6522412) (which turned out in vain) i stumbled on the following graphic:


positive and negative AOA (http://www.bilder-hochladen.net/files/i7vv-1-jpg.html][img]http://www.bilder-hochladen.net/files/thumbs/i7vv-1.jpg)

It depicts the point zero AOA Lift (there is lift due to the cambered profile) and max CL at 16 AOA (stalling AOA of that profile) in the positive AOA region and in the negative AOA region. In the negative AOA region the max CL is smaller by the amount of zero AOA CL.

When we transfer this information to the THS we must assume, that max AOA for max CL is the same for THS up (AND) or THS down (ANU), that the max CL for AND is smaller than max CL for ANU due to the cambered profile for ANU. The ANU function of the THS is more effective than the AND function.

mm43
19th Jun 2011, 20:08
I note there has been continuing discussion on whether the THS has top or bottom camber. As I said in a post earlier (which has been removed), I couldn't find any info on the profile and the drawing was a "best guess". Looking at the pics posted on the other thread, I am inclined to believe that the airfoil has a neutral camber.

A Flight Global cutaway of an A300 THS is the nearest I could find, and it appears to favour a slight positive top camber.

http://oi55.tinypic.com/2i2bhfr.jpg

However, the general idea of how a high AoA would present itself to the THS was what I have attempted to portray, and in that respect I could have done a better job by showing the Angle of Incidence - which is:-

AoI = AoA + (-NU/+ND) or AoI = (61 - 13) = 48°

Castle Don;

The attitude as depicted represents the nominal longitudinal baseline of the aircraft and an approximate chord line for the main wing. The THS is trimmable, and its angle of attack is represented by AoI in the formula above.

HazelNuts39
19th Jun 2011, 20:52
Castle Don;

The AoA of most large airplanes is defined as the angle between the (undisturbed) airflow and the airplane's longitudinal reference axis, and is correctly shown in mm43's super graphic.

Just to confuse things a little, D.P. Davies' book uses the name "angle of incidence" for that same angle. However, for many others "angle of incidence" is the angle between the "wing chord" and the longitudinal reference axis. That angle may be meaningful for light aircraft with a straight, constant section, untwisted wing. It is not meaningful for the swept, twisted wings with variable section that are used on modern large transport aircraft. If you want to apply it to the airfoil section in mm43's drawing, the angle of incidence of the horizontal tail as drawn is -13 degrees.

When talking about two-dimensional flow about airfoil sections, it is customary to define AoA as the angle between the airflow and the section chord. However, when talking about the AoA of the tailplane, one should be aware that the airflow at the tail is not undisturbed. A lift-producing wing has a downwash behind it, and therefore the local AoA is less than the free-stream AoA.

aguadalte
19th Jun 2011, 21:09
In the search for an answer for this camber question, I have found the document of the patented THS system invented by Airbus Industrie (Process for improving the maneuverability of an aircraft during a resource - AIRBUS France (http://www.freepatentsonline.com/7051976.html) please open the PDF).
I know its not much but, the drawings of the THS show a profile with a "neutral wing" (sorry, can't remember the correct name of that wing type).
Please note the last claim of the "paper":
2. The process of claim 1, wherein said initial flight phase is a cruising flight and said resultant aerodynamic force is at least approximately zero. I'm not sure if I'm right but, it seems understandable to me, that in view of the new flight controls systems and new aerodynamic designs, that a solution other than a down camber stabilizer wing would suite the needs for fuel efficiency.

P.S.- By the way, the pictures posted by Confiture were taken from below and do not give a correct idea of the profile of the wing/stab. So, I am still not convinced...

RetiredF4
19th Jun 2011, 22:30
Well, lets look at some more pictures.
Is the A320 series different?

A330-200, see the curve on the underside, would be a very thick profile if symetric (http://www.google.de/imgres?imgurl=http://www.travel-images.com/pht/dominican214.jpg&imgrefurl=http://www.travel-images.com/photo-dominican214.html&usg=__J1o6jMaZDR5CRoZ_2QH55RPgYsQ=&h=469&w=700&sz=89&hl=en&start=1&zoom=0&tbnid=21CW9oCjWj6WOM:&tbnh=94&tbnw=140&ei=d2f-TdLCBJHFtAaiy-XxDQ&prev=/search%3Fq%3Dstabilizer%2Ba330%26um%3D1%26hl%3Den%26biw%3D12 80%26bih%3D799%26tbm%3Disch&um=1&itbs=1)

close view of LE of THS A330 (http://www.flickr.com/photos/clearskyphotography/4443100989/)

A330, see straight top and curved bottom (http://www.flickr.com/photos/pdx_rollingthunder/5706055328/lightbox/)

a319, definite camber on the underside (http://www.flickr.com/photos/francoisroche/3287602678/)

a330 air afrique, definite flat top (http://www.standaard.be/Assets/Images_Upload/2010/05/12/lib5.jpg.h380.jpg.568.jpg)

A320 stabilizer (http://www.google.de/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/d/d1/Estabilizador_horizontal-Airbus_A320.jpg&imgrefurl=http://commons.wikimedia.org/wiki/File:Estabilizador_horizontal-Airbus_A320.jpg&usg=__YnKn8jfROMFRgiZpdFB7F9XzZ6Y=&h=2112&w=2816&sz=1107&hl=en&start=16&zoom=1&tbnid=Jfl5FtVVdt_-ZM:&tbnh=113&tbnw=150&ei=QXj-TYT-F8zzsgbi0K3xDQ&prev=/search%3Fq%3Dstabilizer%2Ba-320%26um%3D1%26hl%3Den%26biw%3D1280%26bih%3D799%26tbm%3Disch&um=1&itbs=1)

Airbus A330-203 MRTT, copy and zoom in (http://www.google.de/imgres?imgurl=http://cdn-www.airliners.net/aviation-photos/middle/7/5/8/1327857.jpg&imgrefurl=http://www.airliners.net/photo/Australia---Air/Airbus-A330-203-MRTT/1327857/&usg=__CAUZNo4p_QPRJfeinjOCHs76exE=&h=492&w=640&sz=76&hl=en&start=18&zoom=1&tbnid=Ajgl8fj1-rskhM:&tbnh=105&tbnw=137&ei=94r_Tam4KIT3sgahm9HzDQ&prev=/search%3Fq%3Dtail%2Bsection%2Bairbus%2Ba330%26um%3D1%26hl%3D en%26biw%3D1280%26bih%3D843%26tbm%3Disch&chk=sbg&um=1&itbs=1)

mm43
19th Jun 2011, 23:16
RetiredF4;

I've reviewed the pics you posted and agree that the A330 THS has more camber on the underside. It follows that with an AoA of close to 0 degrees that a tail down moment is applied and least amount of drag is caused before NU trim is necessary.

Thanks to all those who have posted their comments, and I'll now redraw the THS with bottom camber.

aguadalte
19th Jun 2011, 23:16
RetiredF4:
Is the A320 series different? Yes it is. It doesn't carry fuel, doesn't act as a trim tank.

Me:
The THS on almost heavy aircraft has a positive profile. That is why the "ground set" (http://www.travel-images.com/photo-dominican214.html)is minus 4º, (zero lift). Remember that the A330/340 family (and others) carry 5 Ton of fuel in the trim tank (that is why THS, with trim tank full, flies at minus 3º - only 1º above ground zero set - and this is done) to save about 3% of fuel, due to less drag.
Also, the reason why the elevator flips 30º up and only 15º down is due to the fact that it needs a higher degree up in order to destroy positive lift created by the THS curved wing.

I was speaking of heavy aircraft on the Airbus family.

HazelNuts39:
Just to confuse things a little, D.P. Davies' book uses the name "angle of incidence" for that same angle. However, for many others "angle of incidence" is the angle between the "wing chord" and the longitudinal reference axis. That angle may be meaningful for light aircraft with a straight, constant section, untwisted wing. It is not meaningful for the swept, twisted wings with variable section that are used on modern large transport aircraft. If you want to apply it to the airfoil section in mm43's drawing, the angle of incidence of the horizontal tail as drawn is -13 degrees

None of your pictures shows an undoubtedly lower camber on an A330/A340 aircraft. I've seen most of those pictures before you have posted them here. I've done my research also, and I have found no good picture to post also.

Remember these are twisted wings with variable section.
Would you say that this wing (http://www.jaunted.com/files/6193/ToulouseA380engine.jpg) has an upper camber if you didn't know?

Chris Scott
19th Jun 2011, 23:55
I think (although not sure) that, with the advent of CGCC computers and in order to save fuel, that new big jets suffered a slight redesign of the stab profile. New jets are not designed to be stable. They are designed to fly with near zero trimming. It is therefore a waste of lift and fuel, to design stabs producing negative lift, together with 5 Ton of Fuel...[my highlighting]

True that many jet fighters are fundamentally unstable, but it does not apply to public-transport jets (yet...).

The FBW-controlled A320 is not much less stable than a B737, as far as I know. And it is therefore flyable, and just about land-able, using the THS and rudder as the only means of control. (We practise the former on the aircraft, and the latter in the simulator, on initial conversion.)

The (up-to about) 5 tonnes of fuel in the A330 THS is moved there purely to relax the stability slightly in the cruise, and reduce the negative lift required of the THS (for the reason you stated).

Re the THS bottom-surface camber, I can only speak for the A320. The best view one gets is from a set of steps, when they are positioned at a rear door. The leading edge area is then clearly visible as having more bottom camber, What happens further aft is less clear, I must admit, but the top surface does not show very much convex camber.

Not sure all this makes much difference to mm43's graphic!

HazelNuts39
20th Jun 2011, 09:09
From the Introduction of NACA Report No. 460, The Characteristics of 78 Related Airfoil Sections ...: Airfoil profiles may be considered as made up of certain thickness forms disposed about certain mean lines. The major shape variables then become two, the thickness form is of particular importance from a structural standpoint. On the other hand, the form of the mean line determines almost independently some of the most important aerodynamic properties of the airfoil section, e.g., the angle of zero lift and the pitching moment characteristics. Very old stuff, but still valid. The 'mean line' is equidistant between top and bottom surfaces of the airfoil, and 'camber' describes its curvature, i.e. a symmetrical airfoil has zero camber.

opherben
20th Jun 2011, 12:10
HazelNuts39:

Just to confuse things a little, D.P. Davies' book uses the name "angle of incidence" for that same angle. However, for many others "angle of incidence" is the angle between the "wing chord" and the longitudinal reference axis. That angle may be meaningful for light aircraft with a straight, constant section, untwisted wing. It is not meaningful for the swept, twisted wings with variable section that are used on modern large transport aircraft. If you want to apply it to the airfoil section in mm43's drawing, the angle of incidence of the horizontal tail as drawn is -13 degrees


The inherent wing incidence in a transport aircraft, provides a level cabin in cruise. True with a straight wing, swept wing, any wing, in light, medium and heavy transports.

The vertical tail with its fixed and moving parts, has its angle of incidence set for optimal longitudinal stability and control. Mission requirements, aerodynamic analysis, wind tunnel testing and past company experience, determine which profile and every other parameter, would be optimal.

Saving aircraft operating expenses is affected in longitudinal channel design, by lightweight, low drag surfaces and CG location. Since installed in the back and designed to counter wing and fuselage pitching moments, one way to reduce drag is by reducing the pitching moments against which the horizontal tail must act, specifically by moving the CG backwards. This reduces the tail pitching moment required, and thereby its lift and drag. It does affect longitudinal stability characteristics, but with the use of augmented flight control systems, is mostly latent to the pilot. Having flown quite a bit in variable stability aircraft and rotorcraft for research purposes, I can attest that this design is mostly safely fliable. Not all designs are equal though, for example the MD-11, in which pilots had difficulty controling the aircraft to touchdowen during turbulence, crashing quite frequently because of that, e.g. Narita about two years ago.

barit1
20th Jun 2011, 22:46
There are several factors going into angle of incidence decisions. The CC might like a level floor (zero body angle) in cruise, but then there's Vmu, and several other issues. Most airliners in fact cruise 2 or 3 degrees nose up.

EGMA
21st Jun 2011, 02:10
There is a lot of discussion on this thread regarding AOA and the efficiency of the THS.

It strikes me that both the main plane and tail plane were deeply stalled and providing significant (vertical) drag, rather than controllable lift.

Given that the drag from the main plane acts near the C of G and the drag from the tail plane acts well aft of the C of G this should have resulted in a nose down couple.

The only thing opposing that nose down couple would be the nose up couple provided by engine thrust.

Am I missing something, or was this aircraft unrecoverable until the throttle was closed?

jcjeant
21st Jun 2011, 03:09
Hi,

Am I missing something, or was this aircraft unrecoverable until the throttle was closed? If you read the BEA note .. you will know even the engines on idle .. they don't recover ....

At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have
no valid indications". At that moment, the thrust levers were in the IDLE detent and the
engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In
the following moments, the angle of attack decreased, the speeds became valid again and the
stall warning sounded again.
At 2 h 13 min 32, the PF said "we’re going to arrive at level one hundred". About fifteen seconds
later, simultaneous inputs by both pilots on the sidesticks were recorded and the PF said "go
ahead you have the controls".
The angle of attack, when it was valid, always remained above 35 degrees.
The recordings stopped at 2 h 14 min 28. The last recorded values were a vertical speed of
-10,912 ft/min, a ground speed of 107 kt, pitch attitude of 16.2 degrees nose-up, roll angle of
5.3 degrees left and a magnetic heading of 270 degrees.

EGMA
21st Jun 2011, 04:10
Thanks for that jcjeant .. I did note in the BEA report that there was no hint of recovery ("reducing AoA plus valid speeds") until they'd selected idle thrust.

Perhaps they were fooled by the stall warning coming back?

They hit the ocean with an AoA of 69.3 degrees (trajectory 53.1 degrees + 16.2 degrees nose up) so any recovery had obviously ceased.

Edit: I note they turned onto a heading of 270 in their descent, anybody notice whether they turned upwind or not?

barit1
21st Jun 2011, 17:04
I note they turned onto a heading of 270 in their descent, anybody notice whether they turned upwind or not?

...and what was the rate of turn, which implies a G-force? Or at least a G- vs TAS relationship, which in hindsight gives a crude signal whether they were overspeed or underspeed.

bubbers44
21st Jun 2011, 21:09
Turning upwind or downwind in an Airbus doesn't matter because the computer knows how to handle it because the aircraft is drifting in a mass of air. The new technology has made the airbus such an amazing aircraft.

OK465
21st Jun 2011, 22:22
What barit1 says with regards to the turn is of some significance.

One way to be wing-rocking in a turn to the right with a left roll input on a yoke or SS, even in a heavy swept-wing jet transport with spoilers augmenting the ailerons, is to be stalled.

In addition, that final 60 or so degrees everyone is calling AOA is an angle anchored by a GROUNDSPEED. That final calculated earth referenced FPA is independent of air mass movement. This will only be aero AOA if the air mass is not moving. If the air mass is moving, one-half knot of headwind WILL effectively decrease the actual aero AOA some small amount, just as one-half knot of tailwind will increase it.

True, it's still a bunch of AOA.

EGMA
22nd Jun 2011, 01:34
In addition, that final 60 or so degrees everyone is calling AOA is an angle anchored by a GROUNDSPEED. That final calculated earth referenced FPA is independent of air mass movement. This will only be aero AOA if the air mass is not moving. If the air mass is moving, one-half knot of headwind WILL effectively decrease the actual aero AOA some small amount, just as one-half knot of tailwind will increase it.Valid point, which is why I asked about wind direction. A 20 kt mean wind speed would make that final AoA somewhere between 55 and 75 degrees, depending on wind direction. Still nowhere near a recovery.

HazelNuts39
22nd Jun 2011, 10:07
...and what was the rate of turn, The average turn radius of about 1.23 nm, at an airspeed of 150 kt TAS, corresponds to a turn rate of 1.925 deg/s at an angle of bank of about 15 degrees, n=1.035.

barit1
22nd Jun 2011, 11:46
Now then - if the turn rate remained 1.925 deg/s, but TAS of say 300 kt, what bank angle (and what G-load) would result? :uhoh:

HazelNuts39
22nd Jun 2011, 13:27
Barit1;

bank 28 degrees, 1.133 g. In my simulation TAS changed progressively from 260 to 150 kt in the last 120 seconds.

OK465
22nd Jun 2011, 16:13
Another possibility, academically speaking...

It is possible that the fairly slow heading change to the right is due more to a very gradual yaw to the right rather than behavior typical to an un-stalled coordinated turn with its bank angle and associated load factor and resultant turn rate. It is possible at very high AOA for a left roll input to create this situation.

The roughly 2 degrees per second rate, while not imperceptible, would probably not have a noticeable “feel” to it and would probably have had to have been observed on a heading reference scale, especially if masked by a post-stall wing-rock. It’s also possible that the yaw, though favoring the direction opposite the roll input, could be inconsistent in rate, i.e. “stops & starts” in the descending geometric plane.

If the bank was oscillatory in the stall, the 2 or so degrees/sec could have been an average over the roughly 135+ seconds then. Any period of unloading would have stopped this temporarily also. (Roll direction consistent with the roll input is also a good indication that you are actually unloaded.)

In some swept-wing aircraft with ailerons only, this “aileron drag” can occur at AOA’s even prior to the stall and results in some magnitude of yaw opposite to the direction of applied aileron, slowing the roll rate, or stopping it altogether, or in extreme cases causing opposite roll. This is not a spin, just progressive yaw. Manual application of rudder, with neutral or minimal aileron, is used at very high AOA’s in these kinds of aircraft.

ARI’s & spoilers augmenting ailerons prevent this to any noticeable extent pre-stall in large jets. FBW aircraft in a full up FBW mode are far less prone to this anyway, but post-stall with essentially direct control of the aileron surfaces can produce this in the big jets to varying degrees also.

BOAC
22nd Jun 2011, 17:01
Have I perchance missed another report from BEA after the 27 May? It is just that you lot are talking about rates of turn and the Tech Log about hairy bats, and I wondered wtf?

jcjeant
22nd Jun 2011, 18:43
Hi,

Google translation...

http://henrimarnetcornus.20minutes-blogs.fr/media/01/02/1633103066.jpg

AF 447: should they wait to discover the wreck?

Thanks to its computers and the protections they develop a new generation Airbus (Fly-By-Wire) does not "pick up" not in control law for normal flight. It is a major selling point for the builder who believes that pilot training is not necessary in this area (Pierre BAUD, vice president of Airbus Industrie, 1998).

In case of dropout, no action to perform from memory. The technical crew of an Airbus must refer to an additional procedure described in a document located in a trunk-lid opening near the driver. This procedure is necessary to apply the maximum thrust (TOGA) and simultaneously reduce the pitch.

For years (since 1998) that the aviation community knows that this procedure is dangerous *. The thrust of the engines beneath the wings may, in certain circumstances, generate a couple very important to pitch hard to counter. We must change and cause drivers to implement it. In 1999, William Wainwright, Chief Test Pilot Airbus Industrie reaffirms yet: "There Is No Need for this type of continuation training [upset recovery] is protected fly-by-wire aircraft."

November 27, 2008: an A 320 crashes near Perpignan killing seven people. When checking the operation of the protections in effect, dropping the alarm goes off, the captain applied the current procedure by increasing the engine thrust (TOGA). It follows a couple nose-very important that the pilot can not overcome. The A 320 wins and struck the sea Conclusion: This procedure is wrong, it must be changed.

6 months later, another aircraft type Airbus Fly-By-Wire picks up and hit the ocean ...

June 1, 2009: Flight 447 crashes in the middle of the Atlantic killing 228 people. In his progress report No. 1, the BEA said in the "facts" that the A 330 "appears to have struck the surface of the water line of flight, with a strong vertical acceleration. "In its interim report # 2, the BEA confirms that" the aircraft struck the water surface with a trim, low angle and with a significant vertical velocity. "

In its "Investigation Update" of May 27, 2011, the BEA said that the last values ​​recorded by the FDR is "a plate of 16.2 degrees nose up, a roll of 5.3 degrees left and a vertical speed of - 10 912 ft / min. "

The similarity between the deductions from BEA after the crash and the elements of FDR issued in May 2011 suggests that the BEA and Airbus knew very quickly, as most close observers, that the F-330 A GZCP had won some seconds after the last known position (LKP). The BEA does not make the decision to search the wreckage near the LKP ... at the beginning of 2011. Why?

Should we wait?

* Work of the "Working Group" established by the FAA in 1996 on a recommendation from the NTSBSource:
Les dossiers noirs du transport aérien (http://henrimarnetcornus.20minutes-blogs.fr/)

Lonewolf_50
22nd Jun 2011, 18:58
jcjeant, if the intent was not to find it, then they'd keep on not finding it, even though "they knew where it was." Simple. They'd still be "looking" and not finding it, today.

I do not find your dragging the conspiracy theory into the conversation, yet again, to be useful. The search kept on until successful ... with better equipment, and better techniques.

In other words, "they don't want it found" was proved a bankrupt argument as soon as "they" found it.

jcjeant
22nd Jun 2011, 20:08
Hi,

I take note of your argument ... but the word conspiracy is misleading .. I prefer cover up (it's completely different)
BTW .. this question is not answered ......

The similarity between the deductions from BEA after the crash and the elements of FDR issued in May 2011 suggests that the BEA and Airbus knew very quickly, as most close observers, that the F-330 A GZCP had won some seconds after the last known position (LKP). The BEA does not make the decision to search the wreckage near the LKP ... only at the beginning of 2011. Why?

ChristiaanJ
22nd Jun 2011, 21:52
jcjeant,
Why do you keep quoting cruddy Google translations when better ones are available, and the original French text is available?
And why quote biased French web sites?

SaturnV
22nd Jun 2011, 21:57
jcjeant,
The inadequacy of the search on June 1 has already been discussed; your cover-up idea adds nothing.

The Brazilian Air Force and the French Navy overflew the impact point on June 1. The French-registered ship Douce France searched the area of the LKP on June 1. Neither the ship nor the overflights saw any sign of AFF447 having crashed where it crashed.

There has yet to be an explanation for why the search on June 1 failed so miserably. Hopefully, the BEA, or the French government, or the government of Brazil will explain why this is so.

What would you have done after you receive the reports from the search planes and ship on June 1 that nothing was found near the LKP? Would you keep returning to that area day after day because you believe that's where it must be, or would you send your limited number of planes and ships searching in other areas?

As it was, it was a passing merchant ship sailing way north of the LKP that discovered the floating wreckage, and not the governments who were searching.

wozzo
22nd Jun 2011, 22:55
BTW .. this question is not answered ......

These, and many other questions, will never be answered, because all AF 447-related threads on PPRuNe live in a parallel universum where they are, thanks to posters like you, doomed to repeat the same questions over and over again. :ugh:

jcjeant
22nd Jun 2011, 23:40
Hi,

What would you have done after you receive the reports from the search planes and ship on June 1 that nothing was found near the LKP? Would you keep returning to that area day after day because you believe that's where it must be, or would you send your limited number of planes and ships searching in other areas?As it was, it was a passing merchant ship sailing way north of the LKP that discovered the floating wreckage, and not the governments who were searching. You neglect to keep in mind the ACARS and the first report of the BEA
Those are not pointing fingers to search long way from LKP

The inadequacy of the search on June 1 has already been discussed

And what was the result of those discussions .... ??

So .. WHY BEA with this knowledge go make search far away from LKP ? (phase 2 and 3)
Even here in the first days of those knowledges .. informed people were convinced with .. or a deep stall or a spin ..
Do a airplane cover long distance in such situation ?
In all former catastrophes implying a stall or spin not recovered .. airplanes were discovered near the location of the upset.

KBPsen
22nd Jun 2011, 23:51
You are a broken record, jcjeant,.and adds nothing but the same predictable noise.

Enough already!

jcjeant
23rd Jun 2011, 02:49
Hi,

You are a broken record, jcjeant,.and adds nothing but the same predictable noise.

Enough already!

I take note of your non argument
Now can you answer at the question
Why ?

Denise Moore
23rd Jun 2011, 05:41
voyachan, safetypee, etc.

I understand pilots are trained on where the instruments get their data, but how often do pilots practice that? Isn't it possible that, given the circumstances, they weren't able to work out quickly enough which instruments they could believe or shouldn't believe? (Especially if they aren't sure what has failed.)

Denise Moore
23rd Jun 2011, 05:57
Lonewolf50, as someone with an IT background, including supervision of programmers, I have to suspect a fault in the software, in its not matching real human behaviour.

I've found programmers design software in a particular way, and if human people behave differently the programmers are resistant to changing the software. A simple example is entering a date. People might enter a date various ways, but programmers often don't like to design the program to accept any valid date. Often programmers will insist people should have to learn how to enter the date a particular way.

I suspect that is part of why the handling of stall warnings is handled badly. If the warning is supposed to be continuous then it should be continuous if the aircraft is detected to be stalled while in the air. Don't assume pilots will figure out that the plane is still stalled and but that the stall warning stopped for some other reason. Don't assume a pilot who did the right thing will figure out that a new stall warning is misleading.

In this thread it has often been said that somehow the pilots seemed to not realize that they were stalled, or perhaps thought they had gone overspeed. With all respect to those who think the pilots had to be to blame, it is not likely that three experienced pilots all made such errors unless the instrumentation and the way it presented information to them misled them.

BTW, I was surprised when people reacted with surprise to the suggestion that the FBW system should have said why it gave control back to the pilots. I understand the reaction was due to a conceptual understanding of the whole point of the FD system. But I suggest perhaps that should be given a second look. It seems like some information about that was given to the pilots, but perhaps it might in some situations be useful if that information was more clearly available.

I won't go into the weather issue. That, after all, is at least in part a judgement call. And many here have noted that pilots have flown through worse conditions many times without crashing. It could only have been at most a contributing factor, not something sufficient to cause the crash.

jcjeant
23rd Jun 2011, 11:25
Hi,

Because you are too stupid to realise that there is no conspiracyAgain (broken record ?) you also confuse conspiracy and cover up ... two things completely different

A cover-up is an attempt, whether successful or not, to conceal evidence of wrong-doing, error, incompetence or other embarrasing information

A conspiracy is nothing but a secret agreement of a number of men for the pursuance of policies which they dare not admit in public

Lonewolf_50
23rd Jun 2011, 12:54
jcjeant, not quite.
Again (broken record ?) you also confuse conspiracy and cover up ... two things completely different
Not really. If you are trying to conceal information that multiple people have access to, then you need to get a group of people to agree to a plan to do something unethical. <= That's a conspiracy, is it not? :cool: Absent a plan to conceal, then the information will be available.

Suggest you forward your concerns of a cover up to:

1. Members of French Parliament
2. BEA
3. Law enforcement authorities in France (who would have an interest in illegal activity)

This set of forums, however, appears not to be the place you'll get satisfaction.

Why? For one, you are asking people to prove a negative. That's a dead end. ("There must be a cover up if there isn't evidence that there isn't one." Sorry, that isn't necessarily so. You are assuming a conclusion without a valid premise AND evidence.)

Two, you assume an answer in your question, when that answer hasn't been supported by evidence. That's a case of asking "have you stopped beating your wife."

Please give it a rest.

mm43
23rd Jun 2011, 20:16
Denise Moore;
With all respect to those who think the pilots had to be to blame, it is not likely that three experienced pilots all made such errors unless the instrumentation and the way it presented information to them misled them.
Perception and logic are not necessarily good bedfellows.

A system designed to provide prior warning of a stall can and will fail when its warning is dealt with incorrectly. A bit like the original photovoltaic door guard; it told you when the beam was broken but didn't discriminate between someone entering or leaving.

HarryMann
24th Jun 2011, 00:07
FBW could not change the laws of physics, if you use cambered airfoils, the lift of the wing has to be upward and that of the tail downward at 0° AOA to have some kind of positive stability, when the confusers go on leave. Could I finally close the camber issue, after so much (debatable) discussion..

1) Mean camber would be -ve (e.g. on bottom surface, as installed)

2) Camber of a supercrital aerofoil section is not always that obvious, max thickness often far back (>50%) and strange camberlines used, but nevertheless, (1) applies.

3) Camber doesn't determine whether foil is lifting one way or other, it determines the ZLA (zero lift angle), Cl max, Cm and Cd curves.

4) Camber optimises the drag of the aerofoil for a given AoA... that is, in this case, the typical cruising Lift Coefficient would be determined and the shape (and hence camber-line) finalised, such that the low-drag-bucket was at that CL (-ve in this instance, however marginally - stability requires it)

5) The aerofoil is working in considerable (and varying) downwash from the mainplane, a stabilising situation.

6) Little of this has much to do with FBW or the somewhat aft CG during cruise; as has been said, this CG is set to offset cruise trim drag, not to create a zero or -ve stability FBW aircraft for maneouvrability reasons.

So the camber determines little, other than the setting angle of the THS and the actual Cd (drag) . As we know from watching amazing outside square loops during aerobatics, even quite + cambered foils such as on a Spitfire, can be flown upside down - they are just draggier and have lower maximum Cl (Clmax)

Lonewolf_50
24th Jun 2011, 01:26
Denise

I suspect that is part of why the handling of stall warnings is handled badly. If the warning is supposed to be continuous then it should be continuous if the aircraft is detected to be stalled while in the air.
A significant consideration conflicting with that is the problem of spurious warnings. That is a non trivial human/machine interface problem that has to be addressed before a particular machine hits the field. For many systems, the weight on wheels switch feature that influences other systems is a way to deal with spurious warnings on the ground. But those can go bad also. I think we have a thread on an accident in Spain where that feature was part of the problem.
Don't assume pilots will figure out that the plane is still stalled and but that the stall warning stopped for some other reason. Don't assume a pilot who did the right thing will figure out that a new stall warning is misleading.
While I agree as a general principle, a driving design paradigm is stall avoidance. That is also a flight imperative __stall avoidance__ particularly in passenger carrying air transport. That mind set, or philosophy, will have knock on effects when the final design and integration decisions are made.
In this thread it has often been said that somehow the pilots seemed to not realize that they were stalled, or perhaps thought they had gone overspeed.
Those estimates are hopefully made as a best guess, since there is so much unknown about this accident.
With all respect to those who think the pilots had to be to blame, it is not likely that three experienced pilots all made such errors unless the instrumentation and the way it presented information to them misled them.
OR, and this is a big OR

Their understanding of what was displayed was influenced by training, environment, or being faced with a novel situation.

Turbine D
24th Jun 2011, 02:55
Hi Denise Moore,

There has been an interesting and continuing discussion regarding the software/human interface in Tech Log, AF447 Thread #4 which is the current one. If you have not done so, you may want to read several posts:
#273, Pg.14
#280, Pg.14
#309, Pg.16
and,
#319, Pg.16
They are all posts by Gums. He flew some of the very first FBW F-16 Falcon fighters that were originally known as Vipers. I think he has some of the concerns you have.
As an engineer, we tend to think in terms of probabilities of failure, e.g., 10⁻⁹ or thereabouts, and designs are formulated and tested on a probability basis. What often is not thought of is "possibility" of failure. Possibilities are real. This was pointed out by PJ2 in a post and he gave a link to an interesting article:

http://leeclarke.com/docs/clarke%20thinking%20possibilistically%20-%20Significance.pdf

opherben
24th Jun 2011, 07:56
Denise Moore wrote:
With all respect to those who think the pilots had to be to blame, it is not likely that three experienced pilots all made such errors unless the instrumentation and the way it presented information to them misled them.

From my limited 9000 hours along 36 years flying and gained understanding, a fliable aircraft, even when lacking an instrument or two, when CFIT from 38,000 feet, is the result of pilot performance. Not to mention how he got there. Or the full aft sidestick input held throughout the fall. Additionally, one doesn't have to be an experienced captain, just a rated aviator, to know how to avoid a CB, and how to trim to neutral during stall recovery. Altough engine thrust when initially applied here is counterproductive, it shouldn't affect recovery by much as a full forward SS plus neutral trim would have effected a successful recovery by FL200.

Denise Moore
24th Jun 2011, 08:12
Lonewolf_50, I would go with the novel situation idea.

After all, given how much has been done to eliminate accidents, most common situations that would lead to accidents are going to be covered off by pilot training and experience, aircraft design, etc. I suppose a pilot could make a "rookie mistake" and in some situations that could cause a crash. But these days most crashes are likely to involve a confluence of different factors that if they had not combined wouldn't each have by themselves resulted in a crash. It is likely to be a novel situation.

I suppose one implication might be to add something to basic pilot training. Try to also have training to help pilots to recognize and deal with novel situations. (Aside, pilots who flew in wars might, besides having just more experience, also have had to develop more ability to deal with novel situations.)

Even though a situation might be novel, the pilot's ability to deal with it is still going to be affected by the way the aircrafts instrumentation and systems work. How much useful information did the pilots of AF447 get? What were they able to do to command the aircraft? We really still have to go to those factors as the underlying "fault". Unless pilot qualifications start taking into account the person's ability to deal with novel situations, blaming it on a novel situation isn't all that helpful. Even though, yes, it was a novel situation.

Like others, I'm puzzled about what happened during the final 3 minutes or so, and why there is so far no information about that. I find it unlikely that all three pilots were stunned and baffled and just did nothing. Unless maybe the physics of the situation made it impossible for them to do anything? Otherwise it is likely that one of them at least tried to do something to save the plane and their lives.

Denise Moore
24th Jun 2011, 08:22
Turbine D, thanks for the interesting links.

I would add that, adding to the difficulty is also that known possibilities can be ignored.

Consider Katrina. The risk of such a hurricane wasn't exactly unknown, but for various other reasons steps weren't taken to cope with that. The recent flooding in Australia is another example. Despite what was repeated constantly, the flooding wasn't unprecedented. Flooding had happened often in those areas, and the governments there actually have decades of records of the flooding. For various reasons, they just hadn't done anything to deal with flooding.

This obviously relates to replacement of the pitots. It probably should have been harder to delay their replacement, by making it harder for the various parties involved to decide that isn't such an important issue.

Denise Moore
24th Jun 2011, 08:28
Opherphen, obviously you're right that pilot performance is involved. And the pilots of AF447 might have made mistakes. But I'm not sure, whether it will be useful to blame the pilots even if they did make mistakes. As I'm sure you realize, a serious look has to be taken at WHY they made any mistakes that they made. We might never know why they didn't divert from the weather, but maybe we can guess. And if indeed they didn't realize they were stalled, WHY didn't they realize they were stalled?

Dwesty
24th Jun 2011, 08:59
Whilst I understand that there are many factors....

There are certain situations where the stall warning and overspeed will sound at the same time, based on an actual previous pitot/static errors that resulted in a crash.

The key lesson to recover is POWER + ATTITUDE = PERFORMANCE, the message is if in doubt set a logical POWER + ATTITUDE and the PERFORMANCE will work.

Like Colgan Air, if you lose sight of the basic tenants of flying and chase an altitude, attitude or performance without consideration of all factors you will not stand a chance. If in doubt, set an AoA using a logical ATTITUDE (which will closely relate to AoA), set a reasonable POWER, the laws of physics will not cause a catastropic break up unless the AHRS has failed and you are accidentally set 20 degs nose low.

If you performance fly and chase an airspeed, altitude or VSI reading you will lose sight of the basics.

No criticism of others, I know that at night in a CB it is confusing, but its just how I fly.

BOAC
24th Jun 2011, 10:24
Come on now everyone - just like the other thread I keep seeing "they were in a cb" "they didn't divert for weather" - where exactly have I missed these facts? It is looking as if imagination is becoming fact again.

RWA
24th Jun 2011, 14:27
Opherben-:


"....a fliable aircraft, even when lacking an instrument or two, when CFIT from 38,000 feet, is the result of pilot performance. Not to mention how he got there. Or the full aft sidestick input held throughout the fall. Additionally, one doesn't have to be an experienced captain, just a rated aviator, to know how to avoid a CB, and how to trim to neutral during stall recovery. Altough engine thrust when initially applied here is counterproductive, it shouldn't affect recovery by much as a full forward SS plus neutral trim would have effected a successful recovery by FL200."


As someone who only ever flew gliders and light singles, it's probably presumptuous of me to comment, Opherben. But, to my mind, that raises the immediate question of how any of us know that the aeroplane was 'flyable' at all - particularly given the 'full up' position of the 'trimmable horizontal stabiliser' (better known, in my flying days, as the 'tailplane'?

To quote the BEA report on an earlier (2008) all-killed accident in an A320 off Perpignan:-


When the stall warning sounded, the Captain reacted by placing the thrust levers
in the TO/GA detent and by pitching the aeroplane down, in accordance with
procedures.

The nose-down input was not however sufficient for the automatic compensation
system to vary the position of the horizontal stabilizer, which had been progressively
deflected to the pitch-up stop by this system during the deceleration.


Further on in the 2008 Perpignan report, the BEA states:-


Between 15 h 44 min 30 and 15 h 45 min 05, the stabiliser moved from -4.4° to -11.2°
corresponding to the electric pitch-up stop. It stayed in this position until the end
of the recording.

The aeroplane attitude increased sharply and its speed dropped to the point
that rendered it practically uncontrollable, the flight control surfaces becoming
ineffective due to the low speed and the high angle of attack. The aeroplane
stalled again, this time irrecoverably, bearing in mind the aeroplane’s altitudeand without any crew inputs on the trim wheel and the thrust levers. The loss of control was thus caused by a thrust increase performed with afull pitch-up horizontal stabilizer position. This position and the engine
thrust made pitch down control impossible.


http://www.bea.aero/docspa/2008/d-la081127.en/pdf/d-la081127.en.pdf

In the case of AF447, the BEA's phrasing seems to be almost eerily similar:-


At 2 h 10 min 51 , the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight.

http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai2011.en.pdf

One more thing to add - a final quote from the BEA 'note' on AF447; that, at a bit over 10,000 feet, the PF (possibly acting on the orders of the captain, who, according to that Der Spiegel leak, correctly diagnosed that the problem was a stall):-


At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.


Just seems to me that it's far too early to put this one down to 'pilot error.' especially since the BEA's report leaves out so many things that the BEA must already know?

Or does anyone think that the two pilots on the flight deck only noted the 'change in law' and then said nothing else until the 'no indications' exchange after they'd lost 20,000 feet?

Or that the Captain, who got back to the flight deck in a commendably short time, said nothing at all?

HarryMann
24th Jun 2011, 16:57
Yes....

In short then we have lost two similar aircraft in short order due to loss of control of basic pitch attitude, despite the power to recover being at the pilots fingertips and staring him/her in the eyes... that Trim Wheel, the elephant in the cockpit.

Which raises many questions, one of which must be:-

Why are the many training bodies not addressing recovery from stalls (of all styles and reasons), rather than simply illustrating their avoidance and prevention.

Another would be:

Why is the THS given this much automatic command and power in inappropriate situations... a THS reaching above a given NU setting, close to maximum, say 10 degrees; should have had a very specific cockpit warning as it runs through that threshold:

<<Eee Aw Eee Aw>> "THS 10 degrees NU and increasing"

If not before, certainly after Perpignan ... and NU trimmed near-stall incidents are probably more numerous than we know about.
Gatwick and Schiphol are two mentioned somewhere on these forums.

Low slung podded engines combined with a heavily NU THS can get you there... and that's not a good place to be, even at 35,000 ft.in this case.

opherben
24th Jun 2011, 17:54
Technologs ask questions.
Decision makers, having studied the evidence before them must provide timely answers. Two years on, the community, the customers, the families all need answers. I have conducted complex air accident investigations as chairman, in which I grounded the relevant fleet pending certain fixes, whose implementation was completed in the same week the accident took place. A question of attitude, which leads to proper operations risk management (ORM). I haven't seen ORM mentioned here, odd.

I maintain that a fliable aircraft CFIT is the result of pilot performance. Evident in the last BEA report.

Perpignan isn't the only similar case, they are numerous and indicate a fundamental conceptual error in pilot-aircraft interface. No matter how many pilots like to fly Airbus aircraft, they too fail to see the major shortcomings in that design.

Anything else is technologist wording, not managerial straight to the point decision. Leads to chaos.

Would be interesting to see how the final report dodges or dances to French aviation politics.

captdaddy
24th Jun 2011, 19:19
Many suppositions have been made about why these pilots didn't do the right thing.....but NOBODY, including the BEA has told us what they were looking at inside that black box( the cockpit) that stormy night...
Almost everyone has assumed that there were enough indications that gave the pilots the required info to make the right decision....when your cockpit is full of TV screens who can say what was being displayed /seen ...that even holds true for steam gauges...
And if half the displays say one thing and the other half say something opposite, which do you believe ....do you put more trust in airspeed than altimeters ?...
Now add to that the fact that there was the proverbial dark stormy night with no outside visual reference and probably ALOT of turbulence...
I think most of us who have do multiple SIM rides would agree that you can be led to make some erroneous choices when you lose all outside visual reference and maybe half your indicators (not that they have flags pop up ) but they don't agree with other info you're getting...
Add to that the fact that you've just had the aircraft change flight control modes/protections (ie aoa protect, auto trim etc) in the middle of this nightmarish 3 minute ride and I think we might lean toward a more questioning attitude of the designers who think they can cover every base with one of their control laws....

SDFlyer
24th Jun 2011, 20:21
Turbine D: "As an engineer, we tend to think in terms of probabilities of failure, e.g., 10⁻⁹ or thereabouts, and designs are formulated and tested on a probability basis. What often is not thought of is "possibility" of failure. Possibilities are real."

That is very interesting. I work on prediction of response, or failure to respond (a.k.a. "resistance"), to anticancer drugs either in clinical development or approved by regulatory agencies and on the market (various tumor types). We look at various parameters (often called "biomarkers") that we think might have clinical utility in assessing risk. So we run stats on the data and come up with positive and negative predictive value, sensitivity, specificity, hazard ratios (with confidence intervals) and so on.

Like you in a sense, we are also interested in trying to understand and model or predict "failure", which in our case translates to progression of (usually metastatic) disease and death. In your case it's death by another means I suppose.

In coming up with models, you must have to assign different priorities or "weights" to the many different types of variable, no? I mean, all technical failures that can happen shouldn't be treated the same when trying to build a model I assume - or are they? Do you weight them differently, according to some estimate of criticality? I'm not a statistician but I run a fair bit of stats analysis for a living - sounds like you do as well. Sometimes you can't make real progress without some fairly heavy stats, at least in my experience.

glad rag
24th Jun 2011, 20:40
Would be interesting to see how the final report dodges or dances to French aviation politics.

Well since you've made your mind up there's no need to bother us all again, is there?:ok:

bubbers44
24th Jun 2011, 20:59
I once experienced the most dissorienting situation in a Lear Jet when my handflying FO was descending at high altitude and while balancing fuel looked up at the instruments while in the clouds and saw my attitude indicator go through 30 degrees bank and increasing towards redline on airspeed. I felt level as obviously did the FO so it took every bit of discipline to take control and level the three attitude indicators to level flight. I was actually flying sitting leaned over in my seat because I didn't feel level. Experience got us through it, JFK JR didn't fare as well with vertigo. I don't think this would have happened with the captain in his seat even though he was rightfully taking his scheduled rest. I wonder how many hours each of the FO's had of actually flying an airliner without an autopilot in the clouds? My guess is 10 to 30 hrs. Airlines don't want you to handfly any more at a lot of places.

glad rag
24th Jun 2011, 22:10
Having suffered disorientation, just the once, all I can say to anyone who underestimates it's ability to totally deceive you in the most subtle of manners is..

...wake up quick!

No pun intended.

vovachan
24th Jun 2011, 23:06
Something I read: pilots when they become disoriented tend to pull UP. Perhaps this is what we are dealing with here

bubbers44
25th Jun 2011, 00:16
I don't think pilots pull up when they get disoriented unless they are very knew at flying. I saw a Bonanza take off from Burbank, lose an engine, pull up and turn right into a cross control stall that caused them to spin in killing 4 people. More experienced pilots wouldn't have done that. Hopefully some day they will give us some meaningful information of what led up to this accident. So far they haven't told us much of anything even though they have all of the data. We have a lot of experts expounding on their theories with no data however. BOAC, I'm not saying you.

Machinbird
25th Jun 2011, 19:45
When the PF started to apply nose down control in the well developed stall, I wouldn't be surprised if the Captain, who by then had plopped himself into a jump seat, started to float out of the seat and vetoed further tests of that solution. After all, with the engines at idle, someone was probably figuring they might have contributed to the aircraft's pesky ~16 degree nose up attitude.

Machinbird
25th Jun 2011, 20:12
I maintain that a fliable aircraft CFIT is the result of pilot performance. Evident in the last BEA report.
As long as the aircraft was in a stall, it was not flying, and was not under control so CFIT is, in my considered opinion, an overly broad brush for this situation. This is not even remotely like flying into a mountain on approach.

The aircraft was taken outside of its normal flight envelope during cruise. The crew was unable to accomplish the recovery into a normal flight envelope (which was apparently possible given the correct understanding of the situation). Part of the accident investigation will have to focus on why the crew did not achieve correct situational awareness.

Do you think that not having an AOA gage might have been a factor?
It boggles my mind that there are AOA sensors on the aircraft but no real cockpit display.

Yeah, I know, you never flew with it before, so why do you need one now?:ugh::mad::mad::mad:

opherben
26th Jun 2011, 08:51
Since improper flying technique can get an aircraft into stall, a pilot is trained for and is expected to recover from such condition, promptly and efficiently.
An aircraft with handling qualities which make it unlikely to recover a stall isn't suitable for passenger transport.
A stall as encountered by AF447 is a stable flight condition outside its authorised operating envelope, perfectly recoverable in airworthy passenger transports, and far from the second stage of PSG (post stall gyrations) and later, third, stabilized spin. Both later conditions may be unrecoverable in certain types and conditions.
I have flown with and without AOA indicators. They don't replace airmanship and flying skills.

RetiredF4
26th Jun 2011, 09:35
opherben

I have flown with and without AOA indicators. They don't replace airmanship and flying skills.

Computers and all other stuff built in to modern FBW aircraft don´t either, but they are deemed necessary anyway. Because they help and assist to implement airamship and flying skills, as an AOA indicator would do as well.

Otherwise we could argue about what is really necessary besides airmanship and flying skills:
A cup of coffee: When the coffee leaves the cup, you are flying upside down.
And a cigar: When it is finished, it´s time to land.

Machinbird
26th Jun 2011, 13:49
An aircraft with handling qualities which make it unlikely to recover a stall isn't suitable for passenger transport.

Part of the AF447 crew problem that night must have been stall recognition. The flying qualities in the stall were too much like normal flight. Should that be a certification issue?

What about the "stall stall stall" warning you say? Unfortunately that occurred in a context where its validity was called into question. That is why AOA indicators could have helped.


I have flown with and without AOA indicators. They don't replace airmanship and flying skills.

Did you use your AOA as you flew, or did you consider it redundant?
When the airspeed packs up and anytime you are flying slowly, it can tell you quite a lot about your aircraft's performance potential.

Were your airmanship and flying skills as good at 0200 in the morning as they were at 1000 in the morning? If you had been in one of the front office seats in AF447 when the airspeed went South, are you certain it would have been a non-event for you?

Mr Optimistic
26th Jun 2011, 14:05
If the stall warning operates off aoa sensors, and you are in the mode not to believe the warning, why would you believe the aoa readout ? Can see it could potentially help, especially in recovery with uas, but otherwise what evidence is there that it would have helped the SA here ?

aterpster
26th Jun 2011, 14:20
http://i201.photobucket.com/albums/aa214/aterpster/UpDown.jpg

RWA
26th Jun 2011, 14:40
Harryman
Why are the many training bodies not addressing recovery from stalls (of all styles and reasons), rather than simply illustrating their avoidance and prevention.

Excellent point, Harryman, IMO. My guess is that it's almost impossible for the programmers (however talented) to 'reproduce' stalls in a simulator; and equally impossible for the trainers (and the accountants) ever to let novice pilots actually stall real airliners worth hundreds of millions of dollars as part of their training..........

Any of us who have learned to fly anything have learned to 'deal with' stalls. But only in basic training (in my case in the odd Cessna and Blanek or T21 gliders). AND with the benefit of good visibility and instruments that were all working.

I doubt (well, just about KNOW) that any such practice would have been unlikely to have been of much help to the unfortunate guys flying AF447; in icing conditions, with at least periodically-malfunctioning instruments, zero visibility, and severe turbulence. AND with pre-programmed 'systems' interfering as well, though some at least of them will have been 'signing off' and 'leaving it to you' in the middle of things, and just sending you a useless 'encoded' message that the PNF just had to waste time reading and cancelling........

So I'm reasonably sure in my own mind what the accumulating 'problem(s)' that caused the accident were.

But I have no idea at ALL as to what the manufacturers AND the airlines can DO about it. And, seems to me, THEY likely won't have much idea either, up to the present time........

BOAC
26th Jun 2011, 15:55
RWA and all the other boys and girls here - I'm sorry to bang on about this, but please stop MAKING THINGS UP!The level of turbulence increased slightly - NB NOT 'Severe Turbulence':mad: Please try to stick to the given facts - it only confuses the thread. Soon it becomes 'fact' eg - "why did they fly straight into a CB?".

Machinbird
26th Jun 2011, 18:14
If the stall warning operates off aoa sensors, and you are in the mode not to believe the warning, why would you believe the aoa readout ? Can see it could potentially help, especially in recovery with uas, but otherwise what evidence is there that it would have helped the SA here ? Well, let us see how this could be laid out in the cockpit.

First you have Port side AOA going to LHS AOA indicator, then Stbd side AOA going to RHS AOA indicator. The indication should be on the PFD if possible, and should NOT be numeric, but instead should be a simulated analog needle or tape display.

Then if you hear the stall warning, you can see the indicator bouncing in the stall zone and check with the other side for the same indications. Hopefully it is designed so as to get your attention, such as a pulsing red color when your AOA is excessive. Since it is moving you know it isn't stuck. Then all you have to do is believe it. Apply nose down stick and observe AOA decrease. Keep AOA in a safe range. Apply power as necessary. You sure as heck know you aren't approaching Vmo.

If you slap the equipment in a cockpit and don't train people in its use, then it is a waste. I'm sure a creative sim instructor can figure out some excellent training exercises to help bring AOA into your scan.

ChristiaanJ
26th Jun 2011, 18:26
Of course, Concorde had an AoA and 'G' indicator...

http://www.concordesst.com/inside/cockpittour/flightcontrols/pictures/c1.jpg

To what extent it was included in the normal T scan is another question.....

OK465
26th Jun 2011, 20:31
My guess is that it's almost impossible for the programmers (however talented) to 'reproduce' stalls in a simulator;

Not being argumentative, but this is not quite correct.

Flight test data from stall testing, to the extent it was conducted, is incorporated in advanced Full Flight Simulators. These flight tests are obviously structured for some measure of safety, so that beyond a certain point where data collection is out-weighed by risk, any additional data used in simulation is predicted data from other sources.

Beyond the stall boundary there is still a certain amount of training value where simulator characteristics and response to pilot inputs is valid. The problem is you cannot necessarily tell where flight test data transitions to predicted or extrapolated data during a more extended encounter. And truthfully this has not been given any priority in regulatory evaluation requirements of individual simulators. You don't "down" a sim for something for which you have no experience or guidance for subjective evaluation or a flight validated QTG for an automated evaluation.

The big jets are stalled and recovered so as to produce stall warning system functionality and tolerances and recommended avoidance and recovery procedures and technique. Simulations don't discount this.

As has been stated previously, however, improper pilot inputs to any simulation can also take you out of the realm of what was tested and into "new territory".

The advantage of simulation, of course, is that pilots can make improper inputs and get negative feedback safely. There is currently a lot of effort being directed at substantially improving jet transport stall simulations and incorporation into operator training.

EGMA
26th Jun 2011, 20:44
If the AoA is being monitored by the 'system' why not include it as part of any related 'aural'.

I don't need to continuously monitor an AoA indication but ...

"Stall warning 10, Stall warning 20, Stall warning 30, Stall warning 40"

... would sure get my attention ...

and ...

"Stall warning 30, Stall warning 20, Stall warning 10"

... just might let me know that ND was having an effect.

HazelNuts39
26th Jun 2011, 20:47
Then if you hear the stall warning, you can see the indicator bouncing in the stall zone ...When you're flying at Mach 0.6, and have lost your airspeeds, how do you know where your stall zone is on the AoA indicator?

OK465
26th Jun 2011, 21:01
If there is NO AOA indicator in the cockpit, it is NEVER available.

Mr Optimistic
26th Jun 2011, 23:22
I drink gin and tonics in the back. Give it up boys, an aoa monitor would have made no difference here.

HarryMann
26th Jun 2011, 23:32
I am having trouble with progressing further than page 92 on this topic

Any hints or tips? sorry for the trouble

OK465
26th Jun 2011, 23:39
I drink gin and tonics in the back. Give it up boys, an aoa monitor would have made no difference here.

If you travel by air frequently, you may want to switch to something stronger.

canyonlight
26th Jun 2011, 23:41
Apparently applying nose down control with the side stick is about as effective as selecting page 94 of this thread. The thread defaults to 93. I guess the flight program defaults to stall.

Zorin_75
26th Jun 2011, 23:46
AoA surely is valuable information, but if nose points 16 deg up and altitude is going down, one would assume figuring out that there's a sh*tload of AoA doesn't really take a rocket scientist?

So maybe they didn't believe what any of their instruments were telling them - still they must have remembered climbing to FL350 - how can 16 deg NU attitude seem like a good idea up there unless you're trying to massively bleed off speed (then you're somewhat unlikely to select TOGA I guess?) or flying a Blackbird?

The more one thinks about it, the less sense it makes. :confused:

Machinbird
27th Jun 2011, 02:18
AoA surely is valuable information, but if nose points 16 deg up and altitude is going down, one would assume figuring out that there's a sh*tload of AoA doesn't really take a rocket scientist?The more confused the crew, the more important it is that they have clear, unequivocal, easy to interpret information available. Their internal computers were no doubt overloaded trying to make sense of what they were seeing. They didn't figure it out in time.

Machinbird
27th Jun 2011, 02:21
Canyonlight
Apparently applying nose down control with the side stick is about as effective as selecting page 94 of this thread. The thread defaults to 93. I guess the flight program defaults to stall. If you will observe, the next potential page is set up prior to the exhaustion of the current page. If you select the next page prematurely, it defaults to the current page.

Graybeard
27th Jun 2011, 02:42
Ecam alerts and warnings must have been a cacophony. The CVR audio must be interesting.

RWA
27th Jun 2011, 02:54
BOAC


RWA and all the other boys and girls here - I'm sorry to bang on about this, but please stop MAKING THINGS UP!
Quote:
Originally Posted by BEA Report
The level of turbulence increased slightly

- NB NOT 'Severe Turbulence'http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gif Please try to stick to the given facts - it only confuses the thread.


With all (genuine) respect, BOAC, in my view the BEA's use of the word 'slightly' is valueless (like much of the rest of the document) since the BEA provides no information at all on how much turbulence was being experienced before the increase (whether 'slight' or not)?

That there WAS an increase is clearly shown by two paragraphs in the note:-


At 2 h 06 min 04, the PF called the cabin crew, telling them that "in two minutes we should enter an area where it’ll move about a bit more than at the moment, you should watch out" and he added "I’ll call you back as soon as we’re out of it".

At 2 h 08 min 07 , the PNF said "you can maybe go a little to the left […]". The airplane began a slight turn to the left, the change in relation to the initial route being about 12 degrees. The level of turbulence increased slightly and the crew decided to reduce the speed to about Mach 0.8.

So the facts are that the flightcrew warned the cabin about likely additional turbulence, and then, two minutes later, diverted 12 degrees to the left of course and reduced speed.

Perhaps 'severe' was too strong a word; and I'll happily substitute 'significant' if you prefer it. But you'll know much better than I do that airline pilots hate diverting or reducing speed unless they have to, because it means delays.

So I hope that you'll agree that there's little doubt that turbulence was a factor in the early stages of the accident?

And moving on from there, one has to wonder why the BEA used the word 'slightly' at all, when it provides no evidence at all to back it up - and, I repeat, no information at all on what level of turbulence was occurring before said increase?

BOAC
27th Jun 2011, 07:51
RWA - my position on the 'paucity' of information released by BEA is on record on the site. I agree we have only a 'subjective' assessment of turbulence, but it is pretty much standard practice that if moderate or worse is expected, the cabin will be told to secure carts etc and get the pax and then themselves seated and strapped. I cannot see AF being different there but with so many vital clues missing from the published CVR extracts we do not know. Of course turbulence was present, but the experts opinion is that it would have been 'average' ITCZ turbulence. From what little is published, it appears the pilots took the appropriate action initially - warn the crew, adjust route. Based on what little I see so far I do NOT consider turbulence to have been a contributory factor in the accident.

I am trying to stop the growing spread of the 'urban legend' that they "flew blindly and stupidly into the mother of all CBs". As long as that remains unproven (and unposted), I am happy. As I and others have said, there are significant and meaningful chunks of flight deck comment missing from the release for some reason which may well hold an explanation as to why they zoom climbed, for example, which precipitated the stall.

I have commented in Tech Log also on the Atlantic incident in 2001 where an A340 did a similar zoom - without crew input - and its speed reduced to a very low figure too. Way to go.

Edit to correct my error on Vls

chrisN
27th Jun 2011, 10:38
Re unavailable pages, as posted by somebody else, when posts reach a number higher than ending in 00/20/40/60/80, a new page is generated. If Mods. delete some so the “latest” is now within the 00/20 etc. range, the new page number is visible but has no entries and it was said that we can’t get into it.

Look at the most recent post number. If lower than 00/20 etc., there is no accessible next page. If 00/20 etc., there may be another on the next page, or maybe not yet – just have to try it.

Hope that helps.

opherben
27th Jun 2011, 10:54
RetiredF4 wrote: Computers and all other stuff built in to modern FBW aircraft don´t either, but they are deemed necessary anyway. Because they help and assist to implement airamship and flying skills, as an AOA indicator would do as well.

Otherwise we could argue about what is really necessary besides airmanship and flying skills:
A cup of coffee: When the coffee leaves the cup, you are flying upside down.
And a cigar: When it is finished, it´s time to land.

AOA indicator necessity is a function of aircraft handling qualities and mission. It is neccessary in F4 where above 15 units AOA you start using pedals for lateral control, and approach using 19. Otherwise you may depart its operating envelope. In A4 you need it for carrier landings, but don't for airbase operations, although it could be more accurate than airpspeed for determination of climb airspeed, cruise airspeed, endurance airspeed etc...

If it were mandatory, it wouldn't be offered as option, e.g. most Boeing passenger transports. Like ashtrays.

SaturnV
27th Jun 2011, 11:03
BOAC, we do have the report of one 'expert' on conditions along the airway that night, someone who was actually there and not in some chair greatly separated by distance and time.

When passing the INTOL waypoint, they [IB6024, a 340 at FL370] encountered conditions typical of the inter-tropical convergence zone. These conditions were particularly severe 70 NM to 30 NM before the TASIL waypoint. They moved away from the route by about 30 NM to the east to avoid cumulonimbus formations with a significant vertical development, and then returned to the airway in clear skies close to the TASIL waypoint.

The original in French:
En passant le point INTOL, il rencontre des conditions typiques de la zone de convergence intertropicale. Ces conditions sont particulièrement fortes de 70 NM à 30 NM avant le point TASIL. Il s’écarte de sa route d’environ 30 NM vers l’est afin d’éviter des formations de cumulonimbus à fort développement vertical puis la rejoint, en ciel clair, à proximité du point TASIL


IB6024 was 12 minutes behind AF447 (before it deviated, and before AF447 looped in its heading).

For reasons known only to the BEA, the interactive track map that was subsequently released omitted both this flight and the Lufthansa 744 that was 20 minutes ahead, and which deviated to a lesser extent. (The LH track can be traced somewhat by the AMDAR record.)

I will leave it to native Francophones to correct, but I believe turbulence forte is usually translated as severe turbulence.

opherben
27th Jun 2011, 11:25
Macinbird wrote:
Part of the AF447 crew problem that night must have been stall recognition. The flying qualities in the stall were too much like normal flight. Should that be a certification issue?
Incorrect statement, the aircraft was nose high, low airspeed far below minimum for the configuration, weight and airmass instability, sinking like a rock.

What about the "stall stall stall" warning you say? Unfortunately that occurred in a context where its validity was called into question. That is why AOA indicators could have helped.

Needs no complex evaluation to determine flight condition and corrective actions. AOA indicator would confirm it, and the stall warning is obvious.


Did you use your AOA as you flew, or did you consider it redundant?
When the airspeed packs up and anytime you are flying slowly, it can tell you quite a lot about your aircraft's performance potential.

Were your airmanship and flying skills as good at 0200 in the morning as they were at 1000 in the morning? If you had been in one of the front office seats in AF447 when the airspeed went South, are you certain it would have been a non-event for you?

I am not the typical airline type. As chief experimental pilot with decades experience, who determines the authorized flight envelope by flying out of it (for example, to determine VMO [maximum operating airspeed] we fly at 125% its value), and writes pilot manuals and procedures including stall recovery.

In my operational flying, I am better at 2 am, because I know the associated problems and make proper advance preparations. I never use any questionable chemical substance, not even anti-perspirants which poison your body with aluminum, but instead deodorants which lack it (most readers don't know that).

GerardC
27th Jun 2011, 11:40
there WAS an increase is clearly shown by two paragraphs in the note:-
At 2 h 08 min 07.....the level of turbulence increased slightly and the crew decided to reduce the speed to about Mach 0.8.

I agree with "BOAC", there WAS a turbulence increase but, since they only elected to reduce speed at 2h 08, the level of turbulence before that time must have been very benign ideed.
This is very close to the LH crew testimony :
Flight LH507
Flight LH507 (B747-400) preceded flight AF447 by about twenty minutes at FL350. The crew reported that it flew at the upper limit of the cloud layer and then in the clouds in the region of ORARO. In this zone they saw green echoes on the radar on their path, which they avoided by changing their route by about ten nautical miles to the west. While flying through this zone, which took about fifteen minutes, they felt moderate turbulence and did not observe any lightning. They lowered their speed to the speed recommended in turbulent zones. They saw bright St Elmo’s fire on the windshield on the left-hand side.Imho, all this means that those who chose to divert to the east of track had to deviate more, for a longer time and suffered more turbulence.

EMIT
27th Jun 2011, 12:08
Saturn V, #1868,

you are correct in your statement that the French words

"Ces conditions sont particulièrement fortes"

can be translated into the English words

"These conditions were particularly severe".

But where in this little piece of text do you see the word "turbulence"?

The typical ITCZ conditions that were particularly severe may mean that there were more CB's than usual, so a little more deviating action than usual could be necessary.

Once again, as BOAC has stated many times now, it is not at all necessary to fly through the middle of a CB, in order to get the pitot icing problem. I have seen the TAT anomaly (TAT probe icing due to high ice crystal content) when flying through "light green" radar returns in the neighbourhood of CB's, in other words, while avoiding CB's. Turbulence then was only light, occasionally moderate, nothing out of the ordinary. Saint Elmo's and a sound like rain on the windscreen were also present.
Certainly it is problematic that on certain Airbus types the pitot heating can be overwhelmed by ice crystal icing, that's why a recommendation has been made to change the type of pitots, even before AF447 happened, but the outcome of the accident has much to do with basic pitch and power flying. Remember, four perfect attitude sources where always available, showing a very unusual 15 degrees nose up attitude at high altitude.

BOAC
27th Jun 2011, 12:17
Saturn -it would help if you would lay your cards on the table with all this back and forth stuff - most indications we have so far.are that we have NO evidemce that the crew penetrated an active CB, either from a 'separated' armchair or anywhere. You obviously believe they did. Why not state so and declare your evidence please?

I think 'turbulence forte' was discussed extensively on thread 1. I believe it was said to be a non-'standard' grading and thus thought to be subjective. I also think the report was sent well before the LOC. Had it been 'severe' (in your words) the a/c would most probably have been forced to turn back or descend to avoid LOC at that point and/or structural damage and injury to crew and pax. Even your quote from your 'armchair expert' did not consider the weather conditions there to be exceptionally bad.

So - let's hear your facts?

SaturnV
27th Jun 2011, 13:04
Gerard C, of the three other flights on the track that BEA references, the LH reported moderate turbulence and deviated to the west, the IB chose to deviate 30NM to the east, and said conditions were severe. AF459 deviated 20 NM to the west, then chose to deviate 70-80 NM to the east of the track. (The summary of AF459 indicates they encountered unexpected turbulence at NATAL, and immediately began adjusting their radar, but there is no further mention of conditions they encountered, only what they saw on their radar.) So I don't know how you conclude that going in one direction off the track produced a smoother ride. (AF447 deviated slightly to the west.)

EMIT, as noted in the BEA's first interim report,
the BEA made a list of flights close to airway UN 873 during the night of 31 May to 1st June 2009 and asked crews for testimony. Not all of the information requested has been received at present. The testimony summarised hereafter is representative of the information already analyzed.

The narratives of the other flights as published by the BEA are incomplete, and the BEA has not yet provided any additional information. The BEA has also chosen to not release transcripts of the other flights' communications with ATLANTICO. Are there descriptions of conditions being encountered in their communications with ATLANTICO?

(The BEA summarizing seems to contain at least one error: the LH is said to be at FL 350; but the AMDAR trace says 325.)

I agree we have to await the full CVR transcript to see how situationally aware the flight crew was of the weather they were encountering. For example, did they adjust the mode and tilt of the radar, as AF459 did? If they had, and there was discussion of such on the CVR, would you think the BEA might have mentioned that in their most recent note?

SaturnV
27th Jun 2011, 13:25
BOAC, I don't believe they knowingly and purposefully flew into a meso-convective complex with cells that were overshooting to FL 520 or 560.

I do have questions, suspicions if you will, about how aware they were of the weather they were encountering. I do wonder whether and why their perceptions of the outside environment were so different from the flights following that they continued on, and the other flights chose to avoid. Clearly, the actions of the crew of AF459 following, with the same plane model, same radar, presumably the same AF training and procedures, on encountering the amas between ORARO and TASIL were dramatically different. How to explain or reconcile the actions of the two AF flight crews?

Lonewolf_50
27th Jun 2011, 13:35
I agree with "BOAC", there WAS a turbulence increase but, since they only elected to reduce speed at 2h 08, the level of turbulence before that time must have been very benign ideed.
Just a point to consider, beyond agreeing with many that there is quite a bit of information lacking.

The conditions previous to upset are not as important (in terms of understanding pilot response) as conditions during the period 2:10 to 2:14.

As we all know, conditions change in the vicinity of big buildups. Sometimes those changes are significant. The crew expected some change in conditions before the course correction of 12 degrees. There is no guarantee that their correction was sufficient, though it may have been. It also could have been insufficient, with a result of flying into turbulence that they'd expected to avoid by the course change.

One useful piece of non-evidence that we can work with is lack of evidence of an action taken: absence of further warning to the CC to secure the cabin for turbulence.

I do not feel it reasonable to rule out the possibility that a change in condition was coincident to the other problems they encountered.

The well asked question is then: why no alert to the cabin crew? When things get rough, it is standard practice to have the CC secure the cabin.

Aviate, navigate, communicate is also standard. Crew got very focused on aviate, and were having sufficient trouble with aviate to summon the Captain. That is a possible accounting for the non-call to the CC to secure the cabin.

Admittedly, this doesn't give an answer, it just raises another question. So be it, only so much information to work with.

BOAC
27th Jun 2011, 13:41
BOAC, I don't believe they knowingly and purposefully flew into a meso-convective complex with cells that were overshooting to FL 520 or 560. - so carefully worded I understand you do believe they did fly into one at 350. So be it.

The 'difference' you query could be explained by the fact that they were two different crews who 'read' the situation differently. Also in 10 minutes a cell can move quite a distance in relation to an avoid distance of 20 miles or so, so the question is not what 449 or IB did, but what 447 did. If I had 2 Drachma for all the different interpretations of 'weather' I have seen in my career I would be able to rescue Greece from bankruptcy.

As you say, the information from the other flights (and 447) is not complete. We do not know, for example what they saw or decided weather-wise after the CVR 'left 12 degrees'.

I do not understand why you do not accept that at the moment the accident APPEARS to have been primarily triggered by pitot icing in cloud - not a CB. Cloud is pretty difficult to avoid at night.

SaturnV
27th Jun 2011, 14:06
BOAC, if the LH narrative (p. 88 of the interim report) is taken at face value, AF447 was already in the clouds at FL350 on reaching ORARO. So on that basis, I would posit they were already in what they were in, and did not point themselves in the direction of a Cb.

And beyond that, I think we both agree that we won't know more until the full CVR comes out (though even a negative on the full CVR could be telling).

I do find it curious that the BEA dropped the LH and IB flights from the interactive, yet included flights on UN866, 90 NM to the west. Perhaps these two UN873 flights, with more detail, will re-appear in the final BEA report.

SaturnV
27th Jun 2011, 14:58
Back in 2009, Vasquez created this image of what he thought a radar would show.

http://www.weathergraphics.com/tim/af447/af447-radarsim.jpg

Source:
http://www.weathergraphics.com/tim/af447/af447-radarsim.jpg

If Vasquez's depiction is reasonably accurate, did AF447 try threading a needle?

BOAC, I agree that pitot icing was the precipitating cause of the upset (no pun). But proximity to a Cb with updrafts, and associated transport of liquid water into regions where it spontaneously forms ice crystals may have led to the pitot icing.

RWA
27th Jun 2011, 15:00
I am trying to stop the growing spread of the 'urban legend' that they "flew blindly and stupidly into the mother of all CBs". As long as that remains unproven (and unposted), I am happy.


Couldn't agree more, BOAC - truly sorry that we've been at cross purposes. I feel exactly the same way. For myself, I'm sick and tired of the press and public (and most other parties involved) seeking to blame the pilots for almost every accident that occurs. Unfortunately, though, that tends to suit most of the organisations that might otherwise be held liable - especially, of course, the airline, the manufacturer, and the equipment suppliers.

There are bound to be, as always, a number of causes identified in the final report. 'Pilot error' always suits the business side best - beyond that, it will be a 'horserace in reverse,' with Airbus, Air France, and Thales all 'competing' to finish in fourth place.

As I and others have said, there are significant and meaningful chunks of flight deck comment missing from the release for some reason which may well hold an explanation as to why they zoom climbed, for example, which precipitated the stall.

I have commented in Tech Log also on the Atlantic incident in 2001 where an A340 did a similar zoom - without crew input - and its speed reduced to a very low figure too. Way to go.


Total agreement. My earlier consideration of possible, unexpected 'severe turbulence' was actually triggered by the BEA's (in my view, completely out of line) assumption that the 'zoom climb' was merely the result of the PF pulling the sidestick back. I can supply yet another example of a (quite recent, and fatal) 'zoom climb/deep stall' incident that had nothing at all to do with 'pilot error,' and was in fact caused by sudden and 'severe' turbulence:-

Because of storm cells ahead, the pilot decided to change course laterally by 20 km and attempted to climb over the storm cells. However, the thunderstorm front was unusually high, extending up to 15 km (49,000 feet). The Tu-154 entered an area of severe turbulence, pushing up the airplane from 11.961 m to 12.794 m within just 10 seconds. The angle of attack increased to 46 degrees and the airspeed dropped to zero. It entered a deep stall from which the crew could not recover. The plane crashed and burned in a field.

ASN Aircraft accident Tupolev 154M RA-85185 Donetsk (http://aviation-safety.net/database/record.php?id=20060822-0)

Apologies in advance if I appear to come across as unduly cynical...... :)

BOAC
27th Jun 2011, 15:09
RWA - pleased we have an accord!

Saturn - I cannot comment on the 'proposed' radar picture - without diving into my lats and longs and trig tables,
1) I have no idea what the range scale is between the 'red' bits or what they might signify
2) No idea what scanner angle or gain is being synthesised there
3) I see no 'Mauve/purple' to indicate moderate or greater turbulence

Depending on the distance between cells that I saw I might well 'thread the needle' as you call it - normal practice if the gap is sufficient.

A pretty picture but really meaningless in real terms.

Roseland
27th Jun 2011, 17:52
I don't have a QRH available, and the nearest thing I have is the A330/A340 Flight Crew Training Manual from:
http://www.smartcockpit.com/data/pdfs/plane/airbus/A340/misc/A330-A340_Flight_Crew_Training_Manual.pdf
The procedure for Stall Recovery says:
Set TOGA thrust
Reduce pitch attitude to 10° below FL200 or 5° at or above FL200
Roll wings level
Check that the speedbrake is retracted
No mention of pushing the nose down, no mention of checking the HS trim...
It seems to me they were 'following the book', albeit somewhat nose up.
Am I missing something?

RetiredF4
27th Jun 2011, 18:47
Roseland
Am I missing something?

revised stall recovery procedure (http://www.pprune.org/tech-log/415373-new-airbus-stall-recovery-procedure.html)

GerardC
27th Jun 2011, 19:42
(The BEA summarizing seems to contain at least one error: the LH is said to be at FL 350; but the AMDAR trace says 325.)Saturn, do you realise that FL "325" is not an available flight level for this route ?
Where is the "error", then ?

jcjeant
27th Jun 2011, 19:47
Hi,

Am I missing something? I don't think so ..
Any procedures put in force after the day of disparition of AF447 is not relevant for the discussion of AF447 case
The pilots had to work with what they have this day (procedures and training)

Turbine D
27th Jun 2011, 20:01
BOAC,

Your quote:
Based on what little I see so far I do NOT consider turbulence to have been a contributory factor in the accident.
Also in 10 minutes a cell can move quite a distance in relation to an avoid distance of 20 miles or so, so the question is not what 449 or IB did, but what 447 did. If I had 2 Drachma for all the different interpretations of 'weather' I have seen in my career I would be able to rescue Greece from bankruptcy.
I rspectfully disagree with your statements here, there is certainly information that turbulence and weather played a role in this accident. For instance:

Other airplanes flying within the same airspace
1. Lufthansa LH 507, Boing 747‐400, Sao Paulo‐Frankfurt, 20 min ahead AF 447, FL 350 , moderate turbulence, diversion 10 NM west
2. Iberia IB 6024, Airbus A 340, Rio de Janeiro‐Madrid, 12 min afterAF 447, FL 370, severe turbulence, diversion 30NM east
3. Air France AF 459, Airbus A330‐203, Sao‐Paulo‐Paris, 37min after AF 447, severe turbulence, FL 350 auf 370, diversion 80NM east
4. TAM Lineas Aereas JJ 8098, A330, Sao‐Paulo‐Paris 40min afterAF 447, FL 370, severe turbulence, emergency descent, flight route 120 NM east

Light turbulence ‐ briefly causes slight, erratic changes in altitude and/or attitude.
Moderate turbulence ‐ similar to light turbulence, but greater intensity. Changes in altitude/attitude occur. Aircraft remains in control at all times. Variations in indicated air speed.
Severe turbulence ‐ large, abrupt changes in altitude/attitude. Large variation in indicated airspeed. Aircraft may be temporarily out of control.

So, AF447 sandwiched between LH and IB, but closer to IB interms of time and distance, may very well have experienced turbulence between moderate and severe. Notice how turbulence got worse as time went on. However AF447 did not divert, but kept on the track towards the weather ahead. Keep in mind in the ITCZ, these storms come off the coast of Africa as individual cells, but often, as in this case very close together. As they get further off the coast, they slow down and generally combine into clusters. The cluster ahead of AF447 consisted of four distinct columns. The youngest and strongest was to the east and had fully developed, the other three were in the process of decay, the most decayed cell being the western most cell. The entire system is moving westward, but at a slow rate of speed. So the flights that diverted eastward needed to stray furthest from the planned route verses LH that diverted westward.

So then the question becomes why did AF447 not divert? A clue might be this from the crew of AF459:

The Captain of Air France, which has flown Sao Paulo-Paris the same night that the flight AF 447 recounts the crossing of the Atlantic.
It is a key witness in the investigation into the disappearance of the Air France Airbus over the Atlantic. The commander of flight AF 459, who left Sao Paulo on Monday, June 1 at 0:10, French time, on board a AirbusA330 similar to the aircraft, which disappeared, wishes to remain anonymous. But he remembers precisely the conditions encountered [that night].
The route earlier in the flight AF 447. Under this pilot, the weather report that day of major cloud masses in the pot black. “The satellite maps indicated a thunderstorm but nothing alarming, he says, they are very frequent in this region.” Once in the intertropical convergence zone, the crew increases the “gain” of his radar, i.e. its sensitivity.
This manipulation can make reading the screen, which is polluted by many unnecessary details, but enhances the reliability of data on clouds. “This manipulation allowed us to avoid a big cloud mass that we would not have identified with the radar in automatic mode.”
According to one of its two co-pilots, “the cloud mass was difficult to detect because there was no lightning.” The flight AF 459 to make a detour of 70 miles or 126 kilometers, while the flight AF 447, spent twenty minutes earlier, to lead through this area, added the officer. His captain did not want to confirm this information.

Another clue as to why might be this:

Air France is reviewing crew training, use of weather radar and the availability of meteorological information for pilots following the loss of flight AF447 over the South Atlantic last month.

Chief executive Pierre-Henri Gourgeon disclosed the measures a week after investigators divulged details about meteorological conditions at the time of theAirbus A330's disappearance, and the course deviations performed by other aircraft in the vicinity.

In a transcript published by the airline after he spoke to a French newspaper, Gourgeon said there was "never any arbitration" between safety and economy and highlighted operations during weather as an example.

"For example, it's written down in black and white that, when there are storms, you go around them," he says. "There is no question of saving on fuel. Pilots are totally free to choose their route."

One of the aspects of the investigation is the choice of flight track by AF447's crew. Investigators have stated that "several" other flights - ahead of, and trailing, AF447 at about the same altitude - altered course to avoid cloud masses.

These flights included another Air France A330 operating the AF459 service from Sao Paulo to Paris. Gourgeon says this crew crossed a turbulent area that had not been detected on weather radar and, as a result, increased the sensitivity - subsequently avoiding a "much worse" area of turbulence.

"Flight 447 didn't have the good fortune to encounter that first warning and may not have been able to avoid the second very active storm," adds Gourgeon.

France's BEA investigation agency says the crew of AF459, which had been 37min behind AF447, detected echoes on the weather radar which "differed significantly" depending on the radar setting.

The crew initially chose to deviate 20nm to the west but the radar then showed an extensive squall line which led them to deviate to the east by 130-150km (70-80nm).

"On the strength of that report, we are going to review the way we use radar," says Gourgeon. "Whether or not that was the cause of the loss of flight 447, we have to examine every factor and improve all of our procedures and rules."

So, was weather a factor? If you think in terms of likelyhood, possibility or even probability, IMO, it will be a factor.

Your quote:

I am pretty certain "the aircraft is at fault" since I believe if the pitots had not failed the accident would not have happened, nor, I personally believe, would it with iced pitots with a 'conventional' FCS, but am keeping an open mind on the rest

Interestingly, four of the five planes that night were Airbus. I wonder which brand of pitot tubes the other three Airbus planes had where pitots didn't fail? Could it have been because of the particular pitot brand in use or because of weather avoidance by diversion from their intended flight path?

Not trying to change your mind, just some information to think about...

Lonewolf_50
27th Jun 2011, 20:29
GY, in trying to parse the points in the closed thread about stall procedures, I arrive at this yet again. (It seemed to discuss A320 procedures. Hope they are close enough for comparison).

IF you are trained to respond to stall warning with the idea that the stall warning means
"do something or you'll stall" *

THEN you may respond differently if the stall warning is actually telling you
"you are stalled, do something!"

The 5 deg nose up + max power seems like a pre-stall avoidance maneuver to me. (10 deg nose up at alt < FL 250)

EDIT: let me explain why I say this. It makes good sense to begin your action before you stall. If your AoA is close to stall, that's a good time to be warned. The system is designedto warn you for a very good reason: better to get ahead of the stall and fly the airplane out of that condition that to try to deal with being stalled.

While 5 deg nose up max power per that procedure (alt > FL250) would hopefully prevent (or clear, if 16 deg nose up caused it) the stall and not result in another one, a nagging thought crosses my mind.

If that attitude and power combination were sustained for too long, would you not eventually reach the altitude limit and then stall for a different reason? :confused: (Not saying this happened with 447, based on the info to hand, but it's a risk if your stall recovery at high altitude results in a climb, with airspeed limits high and low slowly converging ... )

Granted, once recovered from stall (or even approach to stall) one then works to restore original airspeed, course, and altitude ... gently, I presume.

canyonlight
27th Jun 2011, 21:44
So noted. Thank you.

BOAC
27th Jun 2011, 22:02
Turbine - I accept 'weather' was a factor, otherwise the pitots would not have iced up! Moderate turbulence should NOT cause an accident.

What your table of routes shows, interestingly, is that 447 diverted the correct way - west, where turbulence appears to have been 'moderate' which has NO EFFECT on aircraft control. In addition, a 12 degree left may well have placed them in the same clearer airmass that the LH found (at 10 miles).

But it all proves very little, except that going east appears to have been the worst decision, and the further east you went the worse it got. The 'radar' quote is a sensible action by AF (which of course they should have taught from the beginning)

Still no-one can explain the reason for the bizarre pitch programme these aircraft appear to have. I would really like to see the RH stick trace (assuming it is recorded).

mm43
27th Jun 2011, 22:12
SaturnV; BOAC;

The Tim Vasquez radar simulation image unfortunately had incorrect position information plotted on it.

An enlarged portion with the ORARO and TASIL waypoints added, along with a scale, some timings and the 0210 upset position is shown below. As BOAC has already suggested, the crew appear to have been "threading the needle", and reference was made to the turbulence experienced passing ORARO.

http://oi53.tinypic.com/2u7n4vs.jpg

You can argue over the simulated paint colours, but the picture of what was happening should be pretty clear. In my opinion, they were not in "severe turbulence" - more like "light chop" with the occasional "bump".

Turbine D
27th Jun 2011, 22:31
BOAC - I agree the direction to go at that time was to the West although later on it was to the East. Actually, AF459 started to divert to the West, but then decided the East way around was better.

I really think that AF447 didn't change that 12° from their planned track until they were very deep into the weather and less than 40 km from where the plane hit the sea. The 12° put them on an almost north track.

As far as what causes the subsequent pitch up event, it is a mystery to me with all of the complexities of the FBW logic and computers.

SaturnV
27th Jun 2011, 22:41
GerardC,

From Annexe 1 of the first interim BEA report.

Dans la nuit du 31 mai au 1er juin, un avion équipé du système AMDAR a suivi une route semble-t-il similaire à celle du vol AF447, passant au voisinage du même amas orageux, environ 30 minutes plus tôt, au niveau de vol FL325. Cet appareil a transmis uniquement des mesures de vent et température.

[^^^ p. 91]

The flight is identified as EU0046, flying at 10660 meters, FL325, outside air temperature -40.6C, in light winds. and those measurements were recorded at 01h44.

Back in thread one, the conclusion among posters was that EU0046 was the Lufthansa, and its true identity had been withheld for proprietary reasons. The 30 minutes more or less is actually closer to 20 minutes, as the 01h44 time for the data point would indicate. AMDAR was taking a measurement every 7 or 8 minutes, and I believe the 01h44 point was the one nearest AF447's 02h10 position.

jcjeant
28th Jun 2011, 00:09
Hi,

It is essential to keep the standard high nothing can be neglected
it is not a kindness to overlook slackness or mistakes, it is really great cruelty to do so cruelty to wives and relatives of the man you let off and his shipmates and to yourself.
There is no margin for mistakes in submarines; you are either alive or
dead'!
These words, spoken by Admiral Sir Max Horton when Flag Officer
Submarines in 1941 to all submarine officers and men in Malta, carry a universal truth for all mariners, not just submariners.

Methink this can also apply to the airliners pilots

Lonewolf_50
28th Jun 2011, 21:11
Roseland: from your link


STALL RECOVERY


In alternate and direct laws, an aural stall warning “STALL, STALL, STALL” sounds at low speeds. Recovery is conventional. Apply the following actions simultaneously:

·

Set TOGA thrust
· Reduce pitch attitude to 10° below FL200 or 5° at or above FL200
· Roll wings level
· Check that the speedbrake is retracted




I don't know if this has since been revised, (2005) but I am not sure I'd have listed them in that order, particularly since the potential pitch up moment from TOGA can interfere with nose attitude reduction.

Granted, engines do take time to spool up, so perhaps that order listing, since one ought to be working it all at once, ends up with a nose lowered, wings rolled level, and power arriving on time to get the most thrust one can, and clean up the bird comes last. (Fly/configure, correct order).

As I suggested above, this procedure far more closely resembles a response to stall warning, which is given at an AoA before stall, by design. Follow the bouncing ball ... as the pilot continues with the stated procedure ...


Below FL200 and in the clean configuration, select Flaps 1.
If ground contact is possible, reduce pitch attitude no more than necessary to allow airspeed to increase.
After the initial recovery, maintain speed close to VSW until it is safe to accelerate.
When out of the stall condition and no threat of ground contact exists, select the landing gear up.
Recover to normal speeds and select flaps as required.
In case of one engine inoperative use thrust and rudder with care.
The aural stall warning may also sound at high altitude* where it warns that the aircraft is approaching the angle of attack for the onset of buffet.

* = this passage is consistent with the idea that the initial procedural steps are tailored to a low altitude procedure response to a stall warning in alternate or direct law.

{Proceeding with high alt stall warning }


To recover, relax the back pressure on the sidestick and if necessary reduce bank angle.

Once the stall warning stops, back pressure may be increased again, if necessary, to get back on the planned trajectory.

Would be good steps to recover from a stall as well, except "if necessary, reduce bank angle" seems redundant. If stalled, or darned near, reducing bank angle is another way to reduce stall margin.

EGMA
28th Jun 2011, 22:41
I think it worth remembering the difference between recovering from an incipient stall and a developed stall.

Forgetting power changes which take time to attain ...

If the incipient stall is caused by too high an AoA, lowering the nose will bring about a recovery. If the stall is due to a low airspeed, say after a zoom climb, a moderate amount of nose down may be required.

Once that stall has developed, a considerable amount of nose down will be required to reduce the AoA.

It strikes me that +5 degrees NU and TOGA does not cover all eventualities.

glad rag
29th Jun 2011, 00:54
SaturnV; BOAC;

The Tim Vasquez radar simulation image unfortunately had incorrect position information plotted on it.

An enlarged portion with the ORARO and TASIL waypoints added, along with a scale, some timings and the 0210 upset position is shown below. As BOAC has already suggested, the crew appear to have been "threading the needle", and reference was made to the turbulence experienced passing ORARO.

http://oi53.tinypic.com/2u7n4vs.jpg

You can argue over the simulated paint colours, but the picture of what was happening should be pretty clear. In my opinion, they were not in "severe turbulence" - more like "light chop" with the occasional "bump".

That is quite interesting when added to this below, I read TV's update about the AC position from his site....

http://takata1940.free.fr/LastFlight.jpg

RWA
29th Jun 2011, 04:20
EGMA


I think it worth remembering the difference between recovering from an incipient stall and a developed stall.


I think you're exactly right there, EGMA. Basically pilots appear, until recently anyway, to have been advised and trained only on 'stall avoidance,' not specifically on 'stall recovery;' and also, apparently, to give at least equal priority to 'maintaining altitude,' rather than concentrating on getting the nose down.

The only 'good news,' though, according to this article covering a meeting that took place this year, is that both main manufacturers, and presumably the airlines too, appear finally to be well aware of the need for a 'rethink':-


"Recent crashes linked to stalls include that of the Colgan Air Bombardier Q400 on approach to Buffalo, N.Y. (2009); Turkish Airlines Boeing 737-800 in short final for Amsterdam (2009); West Caribbean Airways MD-82 in Venezuela (2005); Thomsonfly Boeing 737-300 near Bournemouth, England (2007); and XL Airways Germany Airbus A320 off the coast of Perpignan, France (2009).

“Most approach-to-stall incidents and accidents occur with sufficient altitude available for the recovery,” Boeing Senior Safety Pilot Mike Coker told delegates at the Flight Safety Foundation’s European Aviation Safety Seminar in Istanbul this year. “Incidents progress to accidents when the crew fails to make a positive recovery after the stall warning occurs.”

"Flawed training is partly to blame, he asserts. Approach-to-stall training is typically conducted at simulated altitudes of 5,000-10,000 ft., but many stalls actually happen much higher. In the case of AF447, stalls occurred at 35,000 ft. and 38, 000 ft., respectively. That has important, negative implications, Coker concludes.

“Recovery stresses an increase to maximum thrust and recovery with minimal altitude loss,” he says. Therefore, “students try to minimize the nose-down pitch change while engines spool up.”

"To make matters worse, engine margins at high altitude are much smaller than at lower flight levels, where pilots can count on a much greater response to power increases. Also, Coker says, “it is probable when pilots remain on a particular model for extended periods of time that their exposure to approach-to-stall indications and recovery occur as infrequently as once in a decade,” when stall exercises should really be part of recurring training. He stresses that training should focus on correct procedures, reducing the angle of attack and appropriate energy awareness, and not so much on minimizing altitude loss.

"Airbus and Boeing have worked together to devise new procedures for stall recovery that emphasize angle of attack rather than preserving altitude."


http://www.aviationweek.com/aw/jsp_includes/articlePrint.jsp?headLine=null&storyID=news/awst/2011/06/06/AW_06_06_2011_p36-330706.xml (http://www.aviationweek.com/aw/jsp_includes/articlePrint.jsp?headLine=null&storyID=news/awst/2011/06/06/AW_06_06_2011_p36-330706.xml)

I think that tends to confirm my earlier speculation that the blame for this accident is likely eventually to be spread four, or possibly five, ways - in no particular order, the manufacturer (extensive instrument shutdowns, plus the currently-inexplicable behaviour of the THS), the airline (inadequate training and undue emphasis on 'conserving altitude'), the pitot-tube supplier (given that low speed indications may have triggered the stall warnings even though true airspeed may still have been adequate), the pilots, and the weather.

The only 'good news' is that the industry as a whole seems already to be reacting to the 'lessons' of AF447 and other similar accidents, not just waiting for the BEA to produce its report.

PJ2
30th Jun 2011, 14:28
mm43;
You can argue over the simulated paint colours, but the picture of what was happening should be pretty clear. In my opinion, they were not in "severe turbulence" - more like "light chop" with the occasional "bump".Yes, I think so. They had the radar on and were using it for diversion around weather and the remarks (call to the F/A's, and the PNF to PF, "...a little to the left" etc) do not convey anything out of the ordinary in terms of weather and expected turbulence. Generally one knows when one is about to be hammered and the words one uses in the cockpit for diversion, and in one's call to caution the F/As are more direct. "Stop the service and I want everyone sitting down" is what might be said to the F/As if one was expecting moderate turbulence or more.

Turbine D, hear you...agree it's weather-related because the pitots iced up but I don't think the weather played any other role in the loss of control. Only thing I would add in response to others' rides through the area is, such weather always changes rapidly and what was for one a turbulent ride with need for wide diversion around buildups can be good ride with light chop twenty minutes later for another.

RWA;
But you'll know much better than I do that airline pilots hate diverting or reducing speed unless they have to, because it means delays.

So I hope that you'll agree that there's little doubt that turbulence was a factor in the early stages of the accident?
PMFJI, but I don't think turbulence played a direct role at all in this accident.

Diverting or reducing speed costs little time and little fuel...perhaps a two, three minutes and a few hundred kilos. Diversions are not 'hated by airline pilots', they are routine operations when/where required. Unless the diversion is for hundreds of miles off course, (done it), a diversion around weather is a non-issue in terms of schedule and fuel.

Notwithstanding sudden surprises, I agree with mm43 that they likely experienced nothing more than light turbulence.

The vertical and lateral acceleration parameters will tell us soon enough, along with anything said between the PF & PNF that wasn't released in the recent update.

jcjeant
30th Jun 2011, 15:22
Hi,

PMFJI, but I don't think turbulence played a direct role at all in this accident. That can be .. but no one had already show out a scenario for explain the sudden bank angle and turn to the right when AP disconnected...
This "going to right" (despite the apparent correction to left by PF) will continue until plane contact water ..... (BEA graphic)
If not turbulences or weather induced .. what is at play there ?

bubbers44
30th Jun 2011, 21:50
Maybe simply in his haste to grab the side stick when the autopilot disengaged would easily do that since he was reaching for the sidestick in the dark from the left side of the stick and probably bumped it to the right. Unlikely turbulence would have caused it. So far all we know is they lost airspeed indications so the autopilot and autothrottle disengaged. I am sure his hand was nowhere near the sidestick when it disengaged and with his limited experience in the aircraft doubt if this ever happened to him before this event. Sometimes it is nice to have a big fat yoke in front of you when things go south instead of a meal tray.

jcjeant
30th Jun 2011, 21:58
Hi,

Maybe simply in his haste to grab the side stick when the autopilot disengaged would easily do that since he was reaching for the sidestick in the dark from the left side of the stick and probably bumped it to the right. Unlikely turbulence would have caused it. So far all we know is they lost airspeed indications so the autopilot and autothrottle disengaged. I am sure his hand was nowhere near the sidestick when it disengaged and with his limited experience in the aircraft doubt if this ever happened to him before this event. Sometimes it is nice to have a big fat yoke in front of you when things go south instead of a meal tray.
From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the
controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall
warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt
to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments
later in the speed displayed on the integrated standby instrument system (ISIS).he was reaching for the sidestick in the dark from the left side of the stick and probably bumped it to the right

That's wrong if the BEA note is exact
The BEA note show only a "left nose-up input" after the autopilot disengaged .. nothing about a right input by the PF
The right bank is uncommanded

I am sure his hand was nowhere near the sidestick when it disengaged and with his limited experience in the aircraft doubt if this ever happened to him before this event.

Pure speculation not supported by any BEA reports so far ...
You can speculate .. you can't be sure (or maybe you had see the FDR ? :) )

mm43
30th Jun 2011, 22:03
Originally posted by jcjeant ...
This "going to right" (despite the apparent correction to left by PF) will continue until plane contact water ..... (BEA graphic)
If not turbulences or weather induced .. what is at play there ? Yes, this "roll to the right" has been noted earlier and the PF appears to have kept it corrected in conjuction with the NU inputs to the sidestick, i.e. Pitch (- [NU]), Bank (- [L]). The matter of fuel imbalance was addressed by PJ2, and reference to the FCOM shows that the lateral transfer action is automatic. No ACARS messages have any association with it, and other than the BEA noting the actions of the PF following AP/ATHR disconnect, the last noted action was after the aircraft was established in the stall - "The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds". The context in which these left sidestick inputs have been noted by the BEA suggests that they were a dominate feature of control.

During the stalled descent, the airflow over the aircraft was abnormal and may have been affected by a vortex which developed a geostrophic clockwise rotation causing a pressure differential across the vertical stabilizer. On the other-hand there could have been a non-reported control defect, and if this happened I'm sure the BEA will report it in due course.

bubbers44
30th Jun 2011, 23:36
No, JC, I don't know where his right hand was when the AP disconnected but how many pilots on this thread guard the side stick during cruise? I would guess none. I never guarded the yoke because it was so easy to reach and a waste of time. Once in an MD80 I was flying into Atlanta on a cat 1 and below 300 ft in the clouds the plane went into a right bank and AP and AT clicked off. I recovered and landed but who knows what the AP is going to do before it disconnects. That is why we have pilots to fix those things. I can not see any reason to pull all the way back on a yoke because I lost airspeed, can you? Maybe Airbus teaches alpha protection rules that I chose not to learn by not flying it but it didn't work very well this time. Maybe airlines should make sure that their pilots can handle unreliable airspeed problems without losing control as obviously happened here.

xcitation
1st Jul 2011, 03:00
It makes no sense why the experienced pilots after stall warnings would fixate on the flight instruments showing a high pitch and low airspeed; then continue with full stick back and watch it unwind to sea level for 4 minutes. I don't buy it. It simply doesn't add up. The stall warning disabling I admit is confusing however the attitude indicator showing nose up is unmistakable.
IMHO they were not aware of the attitude/airspeed or dismissed it as being bogus. The fact that they nosed up and finally reduced thrust to idle is consistent with a perceived overspeed and nose dive attitude. I have not read any alternative hypothesis that makes sense despite interesting discussions about THS etc.
:confused:

RWA
1st Jul 2011, 05:14
xcitation:-


IMHO they were not aware of the attitude/airspeed or dismissed it as being bogus. The fact that they nosed up and finally reduced thrust to idle is consistent with a perceived overspeed and nose dive attitude. I have not read any alternative hypothesis that makes sense despite interesting discussions about THS etc.


Inclined to agree that they may initially have interpreted the upset as a dive, xcitation; probably 'influenced' by the fact that (assuming that the altimeter was reading true) they'd have been losing height at about 10,000ft. per minute! But there's no guarantee that all (or even any) of the instruments were 'reading true'; especially in view of the 'cascade' of no less than 24 error messages, which among other things had caused both the autopilot and the autothrust to sign off.

And I'm afraid that you're just wrong about them continuing noseup inputs. IMO the BEA note is more notable for what it leaves out than what it puts in; but it does at least report the fact that, with more than 10,000 feet in hand, the PF did in fact 'do the right things,' reduce power, and apply nosedown stick:-


The altitude was then about 35,000 ft, the angle of attack exceeded 40 degrees and the vertical speed was about -10,000 ft/min. The airplane’s pitch attitude did not exceed 15 degrees and the engines’ N1’s were close to 100%. The airplane was subject to roll oscillations that sometimes reached 40 degrees. The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds.


At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again. Further, I've seen it mentioned that the reason that the THS went to 'full up' in the first place may have been because it was responding to the earlier nose-up inputs. But that raises the question of why it didn't 'respond' in turn to the later nosedown inputs, but instead, again in the BEA's words, 'passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight'?

Shore Guy
1st Jul 2011, 06:36
Pitch and Power: Lessons from Air France Flight 447: AINonline (http://www.ainonline.com/news/single-news-page/article/pitch-and-power-lessons-from-air-france-flight-447-30323/?no_cache=1)

RetiredF4
1st Jul 2011, 08:43
Shore Guy
Pitch and Power: Lessons from Air France Flight 447: AINonline

Did the Air France crew simply fail to fly the airplane, as some claim, or were they the victims of a training system that taught them to rely too heavily on computers right up to the moment the impossible overload occurred, like the HAL 9000 in Stanley Kubrick’s film 2001? No one questions whether or not the Air France crew met the certification requirements in place at the time they received their type ratings. But does the type-rating requirement on an Airbus, or any other large aircraft, go far enough into the actual handling characteristics of the aircraft–especially at high altitude–and especially when multiple computer failures occur? (Bolding by me)

Another question keeps nagging in my mind since some time:

Are those actual handling characteristics of FBW aircraft - especially at high altitude- and especially in Alt or Direct LAW known to the manufacturer and to the regulating authorities, and if known, how are they communicated to the training departements and pilots?

Since nearly two years a lot of experts and pilots of this forum (i´dont count myself to those experts) familiar with the aircraft or at least familiar with FBW or engineering FBW are discussing what happens when this and that is going on. Looking back there is lot of disagreement concerning technical and piloting issues, besides the principle PP and importance of AOA. We have searched the web and found uncountable publications related to the aircraft, its normal and abnormal handling procedures, but concerning aerodynamic behavior of the aircraft in high altitude cruise where the ship is flying most of the time, the information is thin to nothing. We know, flying is done by automation, but how and why and by what system seems to be out of the grasp of not only the aircrews. What will the aerodynamic behavior of the aircraft be when AOA exceeds an value, how will CL shift, will there be a tendency of the nose to drop or will it stay high, what will the stabilizer effectiveness be, will ss roll input induce opposite roll due to missing yaw compensation, and how will a degradation of the FBW systems due to failures influence this natural aerodynamic behavior of the aircraft? If some and a lot more points are known to the crew in such a situation, only then wil they be able to judge the effectiveness of control inputs (like nose down stick, how long, how much nose down.....) and have a better chance to do the correct actions.

I wouldn´t have survived in my fighter, would i have been trained and tested on such a minimalistic scale.

jcjeant
1st Jul 2011, 09:50
Hi,

Yes, this "roll to the right" has been noted earlier and the PF appears to have kept it corrected in conjuction with the NU inputs to the sidestick, i.e. PSo this departure in a right bank stay a mystery ...
Maybe the pilot would not act on the joystick if this angle to the right would not have happened
I suppose the fact to roll to right induced also a lost of altitude

Pali
4th Jul 2011, 13:22
I've read with interest almost the whole thread. It puzzles me why would a trained crew of 3 experienced pilots not recognize stall and would try to handle the situation with nose up inputs most of the time during the fatal fall.

It seems to me like if the confused pilots would try to handle or avoid a (non-existent) overspeed problem.

Now I have a general question: What is actually a more feared situation? Would an unhandled dive lead to kind of Mach 1 speed with a fatal end? Do pilots try to avoid overspeed even if there would be a risk to end in a stall? It is called coffin corner after all...

There is a great deal of discussion about stall in this thread over and over but I can't find anything about overspeed problem. Can someone please explain this or point to some link which describes the situation more?

Roseland
4th Jul 2011, 14:16
Like others in this forum I suspect that no one factor will be found solely responsible for this tragic loss.

Having read (I think) every post in this thread, as well as both BEA reports, I have tried to make a list of ‘things we should learn from’ so as to avoid a repeat.

I would be interested to hear if I have missed out anything significant. Before I get flamed, I should point out that I am not a qualified Aircraft Engineer, my flying is now in the past tense, and these are my subjective opinions!

The aircraft appears to have flown into a storm. It is unknown whether the decision not to detour further away was due in part to a fuel constraint.

Airbus considered the need to upgrade to the pitots only warranted a Service Bulletin, rather than an AD. This is surprising given the number of documented previous occurrences of unreliable airspeed and their obvious safety implications.

Air France appears to have taken over a year to start to implement the SB. AF447 had not been upgraded.

A lack of visual and aural cues from the controls (no yokes moving, no throttle levers moving, no “tick, tick” from the HS trim) may have denied the crew warning of the impending AP disconnect.

The design of the stall warning system, whereby it is disabled if the apparent airspeed (i.e. as measured by the pitots) falls below 60kts is astonishing, given the known pitot icing issues. It beggars belief that such a system can get through design and certification.

The Airbus Stall Recovery procedure in force at the time, which the crew appear to have been following, started with “TOGA”, and had no mention of either getting the nose down or checking HS trim. No distinction was made in the procedure between recovery from an incipient or a developed stall.

The disabling of the HS autotrim once in Abnormal Law has apparently been a factor in other accidents; it remains to be seen if it was a factor here.

Graybeard
4th Jul 2011, 16:24
Mandatory Service Bulletins are paid by the manufacturer: Thales or Airbus in this case. Optional SB are paid by the user, and on the user's schedule. The maker tends to downplay the urgency, in order to avoid paying the cost. It takes a diligent regulator to correctly accept the maker's determination of mandatory vs. optional.

If an airline wants to incorporate an SB Free of Charge, it often has to argue the case. Pending orders for new planes affect these negotiations, of course.

Assuming there was a limited supply of new pitot probes, it would have been prudent to do a phased upgrade, doing one at a time on each plane until the full fleet has one new pitot. Doing all 3 at once on each plane was a mistake, not only for logistics, but also if something went wrong with the upgrade.

If just one pitot on AF447 had been replaced earlier...

oldchina
4th Jul 2011, 17:32
It is unknown whether the decision not to detour further away was due in part to a fuel constraint".

Well, unknown to you and I certainly, but I bet the answer comes out on the CVR, and is known to the BEA.

If started early enough a 20-40 nm detour adds an insignificant amount to the fuel burn.

Of course if you wait till you're face to face with the big painting on the radar, it's something else.

lomapaseo
4th Jul 2011, 21:04
Mandatory Service Bulletins are paid by the manufacturer: Thales or Airbus in this case. Optional SB are paid by the user, and on the user's schedule. The maker tends to downplay the urgency, in order to avoid paying the cost. It takes a diligent regulator to correctly accept the maker's determination of mandatory vs. optional.



That certainly is not a fact other than what somebody negotiates in a contract.

The decision of mandatory is entitrely the regulators based only on the facts of the impact on safety. The manufacturer may place in the record any needs for urgency as they see fit. There has even been cases where a manufacturer's recommendation for urgency have not resulted in a mandated action by the regulator.

This is not about money, it's about safety relative to the original type certificate and any new useage data.About the only time money enters into this is the time for compliance factor.

BOAC
4th Jul 2011, 21:15
Roseland - I go with all of your post #1909 except the para beginningThe aircraft appears to have flown into a stormwhich is totally unproven.

testpanel
4th Jul 2011, 21:58
Roseland - I go with all of your post #1909 except the para beginning Quote:
The aircraft appears to have flown into a storm
which is totally unproven.


Is it?
AF/IB and others diverted, to the east...............
They flew straight into it..............

bubbers44
4th Jul 2011, 23:00
They didn't fly directly into the storm they deviated west instead of east as did half the flights. They took a 12 degree left deviation to avoid weather. Apparently their pitot tubes froze up because of faulty probes that hadn't been replaced yet. When they froze up they pulled back into a deep stall for some unknown reason and crashed. No data of severe weather, just choppy conditions typical of that area. I hope the final report comes out soon so the nonsense can go away. Pilots all pick their way through weather depending on what is happening at the moment, not what another flight did 30 minutes before them. Weather changes rapidly sometimes.

Roseland
5th Jul 2011, 07:40
The purpose of the list was to identify potential weaknesses in systems and procedures that could come back to bite future flights.

The point about the storm was to question the wisdom of allowing flight plans to be filed where the advertised destination is an 'alternate'.

Regardless of Air France's comments about the pilots being free to choose the route and make an unscheduled stop, I am sure there is pressure to eke out fuel and keep to the published timetable.

JCviggen
5th Jul 2011, 09:01
Apparently their pitot tubes froze up because of faulty probes that hadn't been replaced yet

I don't think that can be established as a fact. Faulty is not the right word anyway imo. There were certainly probes ready to go on that should be at least a bit better in icing conditions, but it is by no means certain that they would not have frozen up as well in the conditions they encountered which could have been anything from very severe...to moderate. We'll never know.

matkat
5th Jul 2011, 10:10
greybeard, I am afraid you have the issues of SBs wrong many SB providers put things such as mandatory or alert on the SB however this is irrelevent as only a national aviation authority can mandate an SB, ALL SBs are optional when they are mandated by an authority they become ADs and off course have to be carried out. You are however correct in the statement that some come free of charge and others cost.

Roseland
5th Jul 2011, 10:11
JCviggen,

I agree the pitots froze, and that whilst the newer ones recommended in the 2007 Bulletin should have been better, there is no guarantee they would not have iced up too.

For me the questions are

"In the light of the catalogue of previous unreliable airspeed occurrences, should Airbus/the regulator have mandated the upgrade, rather than as an advisory", and

"Should Air France have implemented the upgrade, on at least one pitot per aircraft, more swiftly?"

oldchina
5th Jul 2011, 10:31
"allowing flight plans to be filed where the advertised destination is an alternate'"

If you are referring to reclearance/redispatch procedures, they are allowed because they require fuel reserves in accordance with the airline's policy to be available at all times.

In other words the flight should arrive at 'advertised' destination with enough fuel for holding and diversion to alternate, if needs be.

Roseland
5th Jul 2011, 10:40
oldchina,

I'm clearly missing something here. If what you say is correct, and I am sure it is, then why file a plan where the intended destination is listed as an alternate?

WanganuiLad
5th Jul 2011, 11:22
I, a mear slf have a question :)
The sidestick was hard left and back for 30 seconds.
Would this input have been as likely to occur if they had a yoke in front of them ?

I wonder if there is a sensory perception penalty for having the primary control out of the direct line of the pilots sight ?

BOAC
5th Jul 2011, 11:30
Roseland - you have me confused now. What is this about "why file a plan where the intended destination is listed as an alternate?". Destination was CDG. The alternate was ORY. Can you explain your query please?

Roseland
5th Jul 2011, 11:34
WanganuiLad,

I think there are two questions here:

Would the PF been more aware of the inputs he was making, and

Would the PNF and Captain have noticed the inputs more quickly had it been a yoke rather than a sidestick.

A third question could be "would the crew have noticed the yokes creeping forwards to offset the HS trim as the pitots iced?" prior to AP disconnect.

Roseland
5th Jul 2011, 11:39
BOAC,

You're right (of course!).

The first BEA Report lists Paris ORLY as the alternate, not CDG.

Must be my age - I still think "Paris, must be Orly!"

Apologies to all for the confusion!

oldchina
5th Jul 2011, 11:56
The answer lies in the en-route contingency fuel (typically 3% of planned trip fuel) which has to be loaded as reserve together with fuel for holding at destination and diversion to alternate.

A first flight plan is filed with e.g. Bordeaux as "destination" and anywhere suitable as alternate. Could be Toulouse, could be CDG.

When getting close to BOD, if the 3% contingency has been consumed you land at BOD.

If, as is usual, most of the 3% has not been used, you file a second flight plan from this redispatch point to CDG.

Fuel for holding at CDG and diversion to ORY is still required but contingency fuel is now only 3% of the planned burnoff from reclearance point to CDG (very little). Very very common and perfectly legal.

eSpoiler
5th Jul 2011, 12:56
Anyone know when the BEA report is due? I can't wait to see which of the many hypotheses for the cause prove to be the most accurate.

RWA
5th Jul 2011, 13:39
oldchina quoting Roseland
It is unknown whether the decision not to detour further away was due in part to a fuel constraint".

Well, unknown to you and I certainly, but I bet the answer comes out on the CVR, and is known to the BEA.


Must admit, oldchina, that aspect bugs me more than any other part of tihs business. Unless we are expected to believe that the two duty pilots said nothing between 'We've lost the speeds' and 'no indications' -and, further, that the captain said nothing at ALL during his two minutes on the flight deck - it seems obvious that the BEA is suppressing (or, one could say, concealing) information that would probably go a long way towards identifying the primary cause(s) of the accident.

In this connection, it's possibly relevant to quote some passages from the report and CVR transcript for the A320, flown by XL Airways pilots, that crashed off Perpignan in 2008. Those pilots definitely acted unwisely, to say the least - they decided to test the 'low speed protections' at only 3,000 feet, in landing configuration - but the report and transcript clearly shows that, as in the case of AF 447, the THS went to 'full up' and stayed there - and the pilots were just plain unable to get the nose down:-


When the stall warning sounded, the Captain reacted by placing the thrust levers in the TO/GA detent and by pitching the aeroplane down, in accordance with procedures. The nose-down input was not however sufficient for the automatic compensation system to vary the position of the horizontal stabilizer, which had been progressively deflected to the pitch-up stop by this system during the deceleration. The Captain controlled a left roll movement, caused by the stall. The aeroplane’s high angle of attack and the roll movements generated asymmetry, and a speed variation between ADR 1 and 2 appeared. This increasing divergence caused a rejection of the three ADRs by the FAC then the ELAC. The flight control system then passed into direct law. It is likely that the crew did not notice this due to the emergency situation and the aural stall warning that covered the warning of a change of flight control laws. The Air New Zealand pilot, by saying “alpha floor, we’re in manual” likely considered that the alpha floor function had triggered and that in fact the autopilot had disconnected.

15 h 44 min 46 Okay here we go
15 h 44 min 49 Und ich sag ihr jetzt dass wir im Moment in Dreitausend bleiben
The weight is fifty four
And I say now to her that we are maintaining three thousand at the moment
15 h 44 min 51 Golf X-ray Lima triple eight
Tango can you speed reduce speed again
15 h 44 min 56 We are reducing
15 h 44 min 57 Triple click
15 h 44 min 58 ��We are still reducing the speed Golf X-ray Lima triple eight Tango (*)
15 h 45 min 03 (*) I will say when the trim stops
The word “stops” is stronger than the rest of the phrase
15 h 45 min 05 SV: Stall ( x13)
Cricket (stall warning)
15 h 45 min 06 Stop ! Noise similar to thrust levers being moved forward to the stop
15 h 45 min 13 (oh oh oh)
15 h 45 min 18 (…)
15 h 45 min 19 End of stall warning
15 h 45 min 20 Single chime
15 h 45 min 24 Ich nehm die Speed noch mal hoch ja?
(I increase speed ) Yeah?
15 h 45 min 26 Ja it's pitching up all the time
15 h 45 min 27 (…) Stick forward (*)
15 h 45 min 29 Pitching up
15 h 45 min 30
15 h 45 min 31 It’s (*) alpha floor we’re in manual Single chime
15 h 45 min 33 It's pitching up this (…)
15 h 45 min 34 Kriegst du das geregelt? Are you able to handle this?
15 h 45 min 35 Nee No
15 h 45 min 36 Gear up SV: Stall (12 times)
15 h 45 min 37 Gear up Cricket (stall warning)
15 h 45 min 39 Gear up Gear up
15 h 45 min 40 (*)
15 h 45 min 42 (…)
15 h 45 min 44 (…)
15 h 45 min 45
15 h 45 min 47


You can read the whole report on here if you like:-

http://www.bea.aero/docspa/2008/d-la081127.en/pdf/d-la081127.en.pdf

Sorry for the long quote - but I thought about cutting out 'irrelevant parts' but finally concluded that just about ALL of it is possibly relevant.

One question for Airbus pilots. We all know that Airbus throttles don't have servos - so they just stay in their detents, they don't move in response to thrust changes by the autothrust. Are there servos on the trimwheels - or do they also just remain in the 'normal position' whatever the systems tell the THS actually to do?

And, if the latter is so, what means do the pilots have of finding out what position the THS is actually in at any given time?

Lonewolf_50
5th Jul 2011, 15:51
For wanganuilad
I, a mear slf have a question http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif
The sidestick was hard left and back for 30 seconds.

Would this input have been as likely to occur if they had a yoke in front of them?
Depends on how well the attitude indicator was integrated into the PF's scan pattern, not control "position" so much.

EDIT: I have a hard time believing that "hard left and back" for thirty seconds is the accurate translation of what the pilot's input was. I don't think it would take 30 seconds of "hard" input to get the nose up to 16 degrees. My two cents.
I wonder if there is a sensory perception penalty for having the primary control out of the direct line of the pilots sight ?
First off, if this pilot was trained in type (hey, he was!) the where the stick is located is a non-issue. You adapt to where it fits into your hands during type training. A counter to that is "How often did he hand fly in Alt Law?" That is a good question irrespective of sidestick or yoke location.

To more directly answer your question ...
Viper pilots (F-16) seem to have managed to work around this small problem of stick not twixt the legs about thirty years. (see also posts about FBW by a poster "gums" on the Tech log discussions).

http://t2.gstatic.com/images?q=tbn:ANd9GcS2Rqwp87FHZSQSnfEj413FGH5RjQBg6Z38xBY-r2DDLPbkAsU1

Their Naval Brethren, Hornet (F-18) pilots have an FBW control stick remaining in the customary position, twixt the legs.

Either convention seems to work well enough once you've been trained on the aircraft. I have an old friend, retired now, who flew F-18's in the Navy, and flew F-16Ns as an aggressor pilot. He managed to adapt to both.

http://upload.wikimedia.org/wikipedia/commons/9/9e/F18_Cockpit.JPG

If you are a pilot, you don't often look at the stick while you are flying. You sense it's position with the tactile sensations of your hands. You typically "feel the stick" and "look" at its influence via the nose attitude and / or bank you induce with it.

Given that these pilots were in the dark and in the clouds (or in and out of clouds) they'd "see" what their stick was doing by their primary scan instrument, the attitude indicator. (Artificial Horizon, which indicates pitch and roll). Given the FBW characteristics of the stick on the A330, even if both stick were in between the pilots' legs, rather than on one side or the other, the deflection wouldn't be all that visibly apparent the way it is with a traditional yoke.

Lemain
5th Jul 2011, 16:16
Fuel for holding at CDG and diversion to ORY is still required but contingency fuel is now only 3% of the planned burnoff from reclearance point to CDG (very little). Very very common and perfectly legal. And perfectly safe always provided that a/c fuel metering/gauges are highly accurate and that any fuel transfer pumps and tank sumps/fittings allow full use of the expected fuel, if required.

jcjeant
5th Jul 2011, 20:31
Hi,

whatever the systems tell the THS actually to doUnlikely as the throttles .. the trim wheels are moving (but no noise as usual on other types) when trim auto move
This is an indent (indication of deflection angle) on their side
http://www.pprune.org/tech-log/454653-af-447-thread-no-4-a-41.html#post6554443

RWA
6th Jul 2011, 03:20
Quoting jcjeant:-


the trim wheels are moving (but no noise as usual on other types) when trim auto move
This is an indent (indication of deflection angle) on their side



Many thanks, jcjeant, especially for the link to the very clear photograph. So information on the THS position was readily available to the pilots throughout?

As mentioned, exactly the same thing appears to have happened off Perpignan. The BEA, in that report, specifically states that none of the pilots touched the trimwheel.

One sentence in the Perpignan report troubles me a great deal, though:-

When the stall warning sounded, the Captain reacted by placing the thrust levers in the TO/GA detent and by pitching the aeroplane down, in accordance with procedures. The nose-down input was not however sufficient for the automatic compensation system to vary the position of the horizontal stabilizer, which had been progressively deflected to the pitch-up stop by this system during the deceleration.

Can you shed any light on the 'automatic compensation system' to which the BEA refers? Many people on here have been assuming that the AF447 THS went to 'full up' because of noseup inputs by the PF. But the THS at Perpignan appears to have gone to 'full up' (and stayed there) even though the pilot in that case was applying nosedown commands throughout?

Worth mentioning too that the AF447 pilot, according to the BEA, also applied nosedown commands while they were still above 10,000 feet; but, as at Perpignan, the THS stayed at 'full up.'

So what exactly are those automatic systems designed to 'compensate' for?

I think many of us consider it likely that the pilots were at first confused as to whether the aeroplane was in a stall or a dive. Is it possible that the 'systems' were ALSO confused?

jcjeant
6th Jul 2011, 03:45
Hi,

You will find answers in the BEA report (english)
Read it again (completely)
http://www.bea.aero/docspa/2008/d-la081127ea/pdf/d-la081127ea.pdf

RWA
6th Jul 2011, 06:04
jcjeant, I HAVE read it fully...........

I was particularly struck by its mention of the THS misbehaviour - which contains almost the same words as the more recent AF 447 report:-


Between 15 h 44 min 30 and 15 h 45 min 05, the stabiliser moved from -4.4° to -11.2° corresponding to the electric pitch-up stop. It stayed in this position until the end of the recording.


If there is anything else in the report that explains why the THS did this, other than the passage I quoted (which refers to an 'automatic compensation system') I must have missed it? Please point me to the passage you mean?

The strong implication of the BEA's Note is that the AF 447 pilot's noseup inputs caused the THS to go 'full up' and stay there for good; even though, in the latter part of the descent, he was applying nosedown inputs. But equally, the THS at Perpignan did exactly the same thing (went full up) even though the pilot in that case was applying only nosedown inputs.

Which strongly suggests that the THS was, for some reason, 'acting on its own account' rather than reacting to the sidestick inputs?

Anyway, as requested, please 'point me' towards the explanations you reckon are contained in the Perpignan report?

jcjeant
6th Jul 2011, 08:07
Hi,

For me (from the report .. check the laws where was the plane) the auto trim was no more auto for many time ... the plane going in direct law ... no more auto trim ... and also few seconds before crash he was in alternate law .... but with the gear down (no more auto trim)
They never actuated manualy (as in the AF447 case) the trim ... they forget it ...
My two cents

iceman50
6th Jul 2011, 08:32
RWA

You need to read it again and also read up on the flight control laws, there was NO THS "misbehaviour". The A/C behaved as it was meant to. The unusual attitude training coves the fact that the THS may be in a position other than optiminal and "manual" pitch trim may be required. The PFD also has a "use manual pitch trim" message in amber.

In Perpignan they unfortunately did not follow the correct flight test schedule and paid the ultimate price, it is beter to be late in this life than early in the next.

Unfortunately there is NOT enough information about AF 447 to fully see what happened but the THS moved under the pilots direction due to sidestick input. There are also a few comments about the bank being uncommanded. Possibly not as it is surprising the number of pilots that whilst doing the pre-flight control check are unable to just move the elevators or just move the ailerons without making an "uncommanded" input on the other controls. It is regarded as "What's the problem", well that can lead to poor control discipline and could "possibly" have been the initial cause of the roll/bank that needed to be corrected.

cwatters
6th Jul 2011, 09:03
Can I check my understanding as I'm not a jet pilot..

Am I correct in thinking that the trim (auto or manual) has more control throw/authority than the side stick? In effect auto trim has changed to become a sort of "power steering" rather than just a trim?

In direct law, there is no automatic pitch trimming. The control surfaces are activated directly by the controls.

So in direct law if you need to apply a lot of down elevator (or to get rid of a lot of up elevator) the only way is to wind it in using the trim wheel?

If that's the case a minor warning message to use manual trim seems somewhat inadequate.

Edit: I can see why the auto function might have to disconnect if the instruments that control it go faulty but why can't the function that gives more control throw from the side stick be retained?

lochias
6th Jul 2011, 13:16
Hi all
i dont know if anyone mentioned this before but i was told that the whole accident seems to be a pilot error. It seems that the pilot tried to avoid the bad weather by going over it but stalled the aircraft. Instead of sticking the nose down to increase speed and recover went on to "toga" thruttle position.

This action increase the angle of attack thus stalling again.

Will try to see if i find more detail about this rumor.

jcjeant
6th Jul 2011, 13:19
Hi,

Will try to see if i find more detail about this rumor.

You are kidding .. I suppose :hmm:

oldchina
6th Jul 2011, 13:39
I fear he is not...

ChristiaanJ
6th Jul 2011, 14:56
lochais,

I suspect you're thinking of the Tupolev, some time ago, that tried to fly "over" the weather, and that "fell out of the sky" in the process.
It was mentioned in one of the AF447 theads.

RWA
7th Jul 2011, 13:55
jcjeant:-


the plane going in direct law ... no more auto trim ... and also few seconds before crash he was in alternate law .... but with the gear down (no more auto trim)
They never actuated manualy (as in the AF447 case) the trim ... they forget it ...



No need to shout, mate......... :)

We seem to have a continuing misunderstanding. I'm not saying that there was no 'pilot error' involved - in fact I've said several times that, IMO, it was almost certainly one of the factors involved.

All that I'm asking is HOW and WHY the automatic systems could possibly have put the THS to the full up position, and KEPT it there, in two separate all-killed accidents - one where the pilot was applying only nosedown inputs, and the other where the pilot began by commanding noseup but ended up also commanding nosedown?

Given that the BEA, in the Perpignan report, confirmed that the THS being at, and remaining at, 'full up' made it impossible for the pilot to control the aeroplane (i.e. get the nose down):-


"The aeroplane rapidly regained speed under the dual effect of the increase in thrust and the pitch-down attitude. Under the combined effect of the thrust increase , the increasing speed and the horizontal stabilizer still at the pitch-up stop, the aeroplane was subject to pitch-up moment that the Captain could not manage to counter, even with the sidestick at the nose-down stop."

TioPablo
7th Jul 2011, 18:05
FBW systems are very complex. Such a sophisticated piece of software also switches modes or operation states according to several constraints in real-time.
However, it is impossible for any system to deliver the expected output or best solution in an absolute way when the inputs are given by natural forces (non-finite domain). You can test the constraints by generating
variables to feed the different modules, but the sheer complexity and the amount of possible values implies the use of heuristics to deal with certain combination of inputs.
Upper and lower limits may produce an undesired behavior given unexpected situations like: a stall warning which is triggered when the pilot is actually solving the problem by feeding nose-down inputs.
At the other hand, those limits may save the aircraft in other scenario.
So, there more complex the system is, there more prone it will be to deliver unexpected outputs given a real-life situation.
At the end, AF447 was an almost fully operational aircraft that ended at the bottom of the ocean.

Are the highly trained and experienced pilots to be blamed?
Why? Because they got confused?
Ask yourself a single and simple question: Confused by whom?

before landing check list
7th Jul 2011, 18:38
I think front wheel drive cars were a godsend to the casual driver with mediocre skills. IE they are easy to drive however you will not see any serious performance car with front wheel drive only. I know this is a crappy analogy and I know our fighters are very performance driven and some of them are FBW. I do think our airliners need computers and FBW because a LOT of the pilots are NOT PERFORMANCE ORIENTATED AND HAVE FORGOTTEN HOW TO REALLY FLY. They have mediocre skills. For example the yaw damp needed to be off for landing the 9, you have any idea on a 2 mile final a captain would have the ball almost going stop to stop because he forgot what his feet were for? Maybe I am freakin old but it seems like we are (as a whole) demanding less of our pilots flying ability and decision making skills we are molding them inso systems managers without a whole lot of stick time. By stick time I do not mean sitting for hours watching the water pass under while drinking your coffee. I mean real stick time as in gliders, acro, utility etc where you actually have to not only fly but also know what and why you were doing it.
What we actually need of a pilot is a good mix of hands on flying skill, real world experience in weather, ATC, ICAO and relevant rules, and of course systems training and lots of time in the aircraft he/she will be operating.
Of course all of this comes with a cost amd the cost cannot be paid for with our cookie cutter approach, you know the so called flying academies which pump out pilots with minimal experience flying with no actual real world experience.
Our experience base now is retiring and dying, what are we replacing them with?

Gretchenfrage
7th Jul 2011, 18:39
Are the highly trained and experienced pilots to be blamed?
Why? Because they got confused?
Ask yourself a single and simple question: Confused by whom?

Good questions.

It all funnels into what I created many years ago now

SIPE

System induced pilot errors

hetfield
7th Jul 2011, 18:46
@Gretchenfrage

and all others asking the question

"How got three experienced, well trained pilots into that trap?"

For me it's a nightmare, even I'm retired. All night I'm thinking what would I have done, coming back into the flight deck and to find the s... hitting the fan.

Scary:ugh:

before landing check list
7th Jul 2011, 18:46
We have so many more systems because our basic skills have deteriorated. Yes I know the airplanes are faster now, fly higher and faster and we do need a bit more systems, but how many times have both pilots (I have seen it) both look at the FMS and ask each other "WTF is it doing now"?

hetfield
7th Jul 2011, 18:56
Yes I know the airplanes are faster now, fly higher and faster Sorry to say NO, absolutely NO.

Go WIKI.


BUT, the planes are automated to replace, for instance, the Flight Engineer, to save costs.

Sometimes it doesn't work......

bubbers44
7th Jul 2011, 19:23
I've always felt it my responsibility to maintain basic flying skills even though the airline doesn't. Routinely when it is appropriate use just the basic instruments and get your scan working again. Headed south climbing out to cross over Cuba on my 757 I would ignore all except standby attitude indicator, standby air speed, altimeter and whiskey compass while on a vector. If you never did it would you trust those instruments with a complete electrical failure.

If the PF on AF447 had done some of that would they still be flying today?

TioPablo
7th Jul 2011, 22:52
I mean real stick time as in gliders, acro, utility etc where you actually have to not only fly but also know what and why you were doing it.I couldn´t agree more :ok:
I know many pilots who got tired of being system managers and renewed their glider license to regain both: control and joy beside their jobs.

Vel Paar
7th Jul 2011, 23:18
Well to all those by the seats of your pants aces out there, I too would love to fly manually from take off to TOC and TOD to touchdown without use of FDs or just relying on the standby instruments. However I have been warned that should anything undesirable happen and subsequent technical enquiries reveal that I had not used all the automation as designed, I will be deemed to be guilty of not following company SOPs wrt use of automation to accomplish a safe, smooth and comfortable flight. The company and the regulatory authorities take a dim view of anyone wanting to " improvise " to hone their basic manual flying skills!

bubbers44
7th Jul 2011, 23:25
TP, I agree that is the real way to stay sharp but it costs bucks. I towed sailplanes, flew them and taught aerobatics loving every minute of it. I was just showing the cheap route of getting some hand flying for free. Most pilots are too cheap to go out and rent a Citabria or sailplane at todays prices. I put myself in that group. Remember when a Citabria was 17.00 per hr? Probably not because you are too young.

I instructed for the very famous Art Scholl in the 60's at his aerobatic school at Flabob Airport, Riverside, Ca. I cherished the opportunity of meeting Bob Hoover and his well known pilot friends on a regular basis. We still see them at the Reno Air Races every year. I never let my basic flying skills go away because that is all you have when things start falling apart. You owe it to yourself and your passengers to be better than what the pilot mills can put out.

Airbus tried to put out a crashproof airplane but you still need someone to take over when all that automation fails at the worst time.

bubbers44
7th Jul 2011, 23:32
VP, sorry you work for that company. If you don't use your initiative to hone your flying skills and go along with company logic you will lose your flying skills gradually. Hopefully you don't just settle into this job and accept it as the wave of the future. You can probably just do it anyway or if the company is a stickler for no handflying find a safer job.

chase888
8th Jul 2011, 01:16
Interesting comments regarding gliding experience.
Giving a clue to my age, about 50 years ago in NZ, a DC3 was caught on the wrong side of a standing wave and sank about 7,000 feet into the side of a mountain in a nose high attitude on full power.
The general view of the gliding community at the time was that had the pilots had any sailplane experience they would have recognized their predicament and flown out of it.
Obviously no standing waves out in the Atlantic, but the situation for the crew seems eerily similar

DC-ATE
8th Jul 2011, 01:53
before landing check list -

All good points, but what good will it do to have the pilot as experienced as you want him when he can't have TOTAL control over this FBW cr*p ?!?! Correct me if I'm wrong, but I don't think there's a way to TOTALLY, manually fly this stuff. The side stick, throttles, etc. are not connected to anything but electrical wires.

EMIT
8th Jul 2011, 03:12
Well DC-ATE, as you can read in the BEA preliminary report, the airplane reacted in a totally normal way, as soon as a proper stick input was given: when the stick was pushed forward, the pitch attitude lowered and the AOA decreased.
Unfortunately the proper stick input was not maintained long enough to effect complete recovery from the stalled situation.
Nothing really crappy about aircraft response there, Fly By Wire or not.
"Even" an Airbus is a totally normal airplane if you treat it as such.

Do not get confused by Airbus being FBW, it is not statically unstable as an F-16 is. I am not gonna explain that further, that has been done very well by old Gums a lot of postings ago already.

before landing check list
8th Jul 2011, 03:36
They even have "FBW" instead of throttle linkages on some race motorcycles. Why you may ask? So they can eek out a few less milliseconds on the throttle response time. EMIT, I agree if the aircraft did everything the pilots asked of it and if the pilots were not asking the correct questions then shame on them. However I still do not fully appreciate the fact that in essence every time you try to make a input you are asking a computer permission and depending on it's programming you may or may not get what you are asking for. Granted you do have to make the correct inputs, that is where YOUR experience comes into play. It is up to you as the pilot what kind of experience you can bring to the table and what kind of experience the bean counters are willing to pay for. Now we are back to front wheel drive cars made for mediocre driving skills.

Personally I do not mind FBW at all as long as it (the wire) is going through a control tube

I did have the opportunity of jump seating on a A320 (when you could do such a thing) and when we were at FL I asked what would happen if we lost all electrics, I mean ALL. I got a look like I was a kid asking what if a wing fell off. After a bit the captain said something about the FO opening a door to the RAT and then they would spend the rest of the fuel load trying to get a computer on line so they could land it. Yes, it is not unstable like a F16 (Neither is a dart or an arrow) but really what is the real purpose of FBW? I mean we have had fully coupled auto pilots for quite a while and they operated servos and worked just fine. Are we really saving a bit of weight so we can get another 10 passengers on board? Are we trying to reduce response time of a few milliseconds? They are even doing this to freakin helicopters, why? I do not think the benefits out weigh the negatives, but this is just me.

Do you want to be a board member so if the company fails the blame can be passed around or do you want to be a pilot where you(the crew) are fully responsible for the outcome of the flight?

Maybe I am getting old.

RWA
8th Jul 2011, 04:32
Quoting EMIT:-


Well DC-ATE, as you can read in the BEA preliminary report, the airplane reacted in a totally normal way, as soon as a proper stick input was given: when the stick was pushed forward, the pitch attitude lowered and the AOA decreased.

Unfortunately the proper stick input was not maintained long enough to effect complete recovery from the stalled situation.



Unfortunately, EMIT, you appear to be assuming something the BEA's (increasingly suspect) note does not say. In fact, it only states:-



"At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again."


So there is no evidence that the PF did not in fact maintain the nosedown inputs?

Typically of the BEA (on this occasion) the note later mentions both pilots applying simultaneous inputs - but it doesn't indicate whether those inputs were up or down......

On the other hand, the BEA DOES say without equivocation that the THS remained in the same 'full up' position that it had adopted (for whatever reason) at the onset of the accident "until the end of the flight." And, as the BEA said in the earlier Perpignan report which I quoted above, this would likely have left the pilots in a situation which they "could not manage to counter, even with the sidestick at the nose-down stop"?

jcjeant
8th Jul 2011, 05:56
Hi,

Typically of the BEA (on this occasion) the note later mentions both pilots applying simultaneous inputs - but it doesn't indicate whether those inputs were up or down......This one of the reason why I posted in the thread in Tech Log:
The BEA communicate .. but not inform .. just like a tabloid
Too much people confuse the words communication and information .. they are two different beasts ...

fizz57
8th Jul 2011, 07:11
Guys, my guess is that the BEA report is deliberately incomplete to hold off the inevitable lawsuits to the proper time, ie. after the final report is published. In my view, it says all that needs to be said, without actually giving anything definite the lawyers can grasp on. Unfortunately it also leaves enough holes for those on this forum who of course know exactly what actually happened to try and squeeze their pet theories into the gaps.

I'd say the "how" , even if not the "why", is clear enough, and the real professionals (should that be singular?) who have contributed to this topic have it about right.

BOAC
8th Jul 2011, 07:43
I'd say the "how" , even if not the "why", is clear enough- we would all be interested to know exactly what happened - since you obviously do, can you tell us? It would save an awful lot of bandwidth (or should that be a lot of awful bandwidth...?)

RWA
8th Jul 2011, 14:16
Quoting fizz57:-


Guys, my guess is that the BEA report is deliberately incomplete to hold off the inevitable lawsuits to the proper time, ie. after the final report is published.


Sadly, I think you're pretty nearly right there, fizz57. Except that I suspect that the BEA's thinking was even more short-term than that - that they were just required to shove out something that 'hinted' at pilot error, to get Airbus 'off the hook' before the Paris Airshow.......


In my view, it says all that needs to be said, without actually giving anything definite the lawyers can grasp on.

Sadly, I have to disagree there. The BEA's job is to determine the cause(s) of the accident as soon as ever possible, so that similar accidents can be avoided in future. Maybe I'm an idealist dreaming of a 'perfect world' - but we are probably all agreed that the BEA's note is more notable for what it leaves out, rather than what it puts in. The BEA's job is not to 'play poker' with lawyers - however much pressure the political guys put on them.

In a word, it's one of the most 'unprofessional' documents I've ever read in my life.......

Quoting jcjeant:-


The BEA communicate .. but not inform .. just like a tabloid



Exactly right in my view.

OK - I'll stick my neck out with a couple of 'speculations'......

1. As to the stall warnings cutting in and out, my guess is that this had to do with the 'Indicated Airspeed' being understated due to icing and/or the steep pitch-up. As far as I know (though I very seldom flew anything that had any sort of stall warning) stall warnings are 'disabled' below a given airspeed - simply because, if they weren't, they'd go off during the landing flare.......

2. As to the behaviour of the THS, if I was involved, I'd look very closely at the question of whether, if the autopilot and autothrust 'sign off,' it is designed to 'fail safe' or not. After all, the normal 'duty' of the THS in automatic flight, again as far as I know, is to maintain a precise altitude. For all I know, the THS, both at Perpignan and in the AF447 accident, was simply going on with that 'normal job' - trying to regain the assigned altitude it had last been set to maintain, before the autopilot was switched off (Perpignan) or 'signed off' (AF447)?

To repeat, just 'speculations.' Constructive comments/further information/corrections welcome. But anyone who feels the need, by all means 'flame away' if that's your wont........

BOAC
8th Jul 2011, 14:25
While waiting for the 'insight' from Fizz......................

1) Nothing really wrong with a stall warning 'going off' in a landing - if you land a C150 PROPERLY the stall warning should 'bleep' just as you touch. I agree it is not a nice thing to have on a commercial jet, however, it might frighten the pax.

2) Cannot agree with that para -THS is not 'dropped' with loss of A/P. It runs throughout the 'normal' flight regime in AB330 ie it does not 'fail',. A/P or manual. It is not there to maintain 'altitude' but to trim the tail to relieve elevator displacement (ideally!) to allow full elevator authority, just like any other trimmable tailplane.

Geragau
8th Jul 2011, 19:53
Vel Paar's comment :The company and the regulatory authorities take a dim view of anyone wanting to " improvise " to hone their basic manual flying skills!

bubbers44 :VP, sorry you work for that company. If you don't use your initiative to hone your flying skills and go along with company logic you will lose your flying skills gradually. Hopefully you don't just settle into this job and accept it as the wave of the future. You can probably just do it anyway or if the company is a stickler for no handflying find a safer job.

Wow! bubbers, your grandpa must be the CEO of your airline! As far as I know, most air carriers want their pilots to utilise all the automation available to ensure smooth, economical and safe operations. I have unfortunate colleagues called up for tea and bickies when the AIMS/FOQA indicated some minor excursions when they flew manually without FDs.
A few indulgent chief pilots may just wave off such " no SOP " ops but they are getting fewer and fewer.

Phantom Driver
8th Jul 2011, 20:12
Here we go again.....:(
(MHO..)

bubbers44
8th Jul 2011, 22:40
G, so you are all in favor of no flying skills, just punch the buttons. Did you notice by chance what happened to AF447 using your technique? Sometimes the autopilot quits and it doesn't matter what button you push, you are just F*****.

bubbers44
8th Jul 2011, 22:55
G, I am sure the UAE would have a hard time training a competent pilot so maybe button pushing a computer is your only option. I will be watching the news for the results. I'm sure something will be on in the near future.

xcitation
8th Jul 2011, 23:20
IMHO the question is "how do I practice flying outside the norm". The answer has to be using the simulator mostly. I can't really see how sail plane flying would help when the flight deck is lit up like a christmas tree, chirping and whooping, betty nagging and the ECAM scrolling by like the credits on a cheap movie. These pilots knew how to fly and recover from a stall. The big question is how did they process the PFD, ECAM, warnings... That kind of real/perceived multiple failure situation was never trained for. You can't get it in a sail plane or pitts.
The other issue is that you cannot go manual flying around coffin corner in chop. I question how much free play the earlier poster does at FL370 or above. Some manufacturers don't recommend manual at the cruise alt for particular types, its just too woolly to be playing buggles up there. As throwing out the SOPs and going full manual whenever he wants...:bored:

bubbers44
8th Jul 2011, 23:42
BOAC, the thousands of hours spent in a Cessna 150 giving dual reminds me of the stall warning right at touch down. I would never want to hear it in an airliner. We were never exposed to that in airliners because it was well before stall. One time in 23,000 hrs I got a stick shaker in a 727 on a tight turn with speed brakes out at night going into Puerto Plata. I immediately stowed the speed brakes and landed normally. I appologized to my copilot even though he didn't care because it had never happened before or after in my career or his. Stowing the speedbrake fixed the problem because the speed was right, the speebrake brake caused the alert.

EMIT
8th Jul 2011, 23:44
xcitation, previous post

Flying manual, even at FL370 is NOT DANGEROUS, it is just NOT ALLOWED because it is RVSM airspace, where extremely accurate altitude keeping is required.

The 100 or 200 ft margin that we lazy, easily bored humans would maintain if we tried it for 9 hrs would be unacceptable for separation purposes. That is the reason why we delegate that task to ever sharp, never bored autopilots.

Glider flying would be a good training means to bring home the point that flying is a matter of maintaining attitudes and angles of attack, not something of text on screens, whether your IPhone or ECAM displays. Sure, those screens may convey important information, but the flying thing meanwhile is to keep the nose more or less near the horizon, with the blue sky on the side where your aircraft roof is.

FL370, or whatever level you are flying, should give ample margin for normal flying, if not, you have gone too high. Climbing towards, or starting a descent from level, is not against RVSM rules, by the way, neither is flying manually for a short time, e.g. to trim the aircraft properly.

TioPablo
9th Jul 2011, 02:50
Glider flying would be a good training means to bring home the point that flying is a matter of maintaining attitudes and angles of attack, not something of text on screens, whether your IPhone or ECAM displays. Sure, those screens may convey important information, but the flying thing meanwhile is to keep the nose more or less near the horizon, with the blue sky on the side where your aircraft roof is.:D Well said EMIT! (Goed gezegd!)

Geragau
9th Jul 2011, 03:07
One time in 23,000 hrs I got a stick shaker in a 727 on a tight turn with speed brakes out at night going into Puerto Plata. I immediately stowed the speed brakes and landed normally.

Now how did that happen?

totempole
9th Jul 2011, 03:33
I believe what all the self aggrandizing by the seats of their pants aces forget is that most shiny new jets fly out of and into airports where RNP/PRNAV requirements dictate use of the automatics. To fly manually on these SIDs and STARs is to invite possible deviations which can be " career stalling " for some.

Enough of all these great stories of heroics...the world is changing rapidly and like it or not the automatics will rule the future pilot's life. I love flying manually and I am lucky to have flights into airports where RNAV/PRNAV procedures are not required.

The challenge is to be totally proficient in correcting all the anomalies with the automatics entirely or partially. The supreme rule is never ever getting into situations where you have to use your super self declared " acy profiency " to manually get out of situations where you have gotten the automatics into. In my years of training pilots I have seen proud " old aces " get the automatics into ****ty situations and then proudly clicking them off to fly manually, mostly to an untidy end. Their pride.....they didn't crash despite the " failed automatics ". Actually there was absolutely nothing wrong with the automatics in those instances; the problem was the self declared aces did not understand the proper use of the automatics and misuse the functions.

This is not to say that pilots need not maintain their proficiency in flying manually. We have to strike a balance and the world is not going to change just to please those who think peddling the modern contraptions old fashion way is the be all and end all.

xcitation
9th Jul 2011, 03:33
@ EMIT

Flying manual, even at FL370 is NOT DANGEROUS, it is just NOT ALLOWED because it is RVSM airspace, where extremely accurate altitude keeping is required.

Aren't you contradicting yourself?
Out of curiosity how much manual flying above cruise alt have you done and was it in chop?

A37575
9th Jul 2011, 08:01
We have to strike a balance

Agree. But just what measurement of balance? Presumably you are talking about a balance between automatic pilot competency and pure flying skill competency. Surely a captain or copilot pilot licensed to fly a type of aircraft should have 100 percent competency on both skills. In your dreams is the reply from one cynic. If this is too optimistic then let's barter a little. Are you suggesting equal competency? Or is the balance 10 percent towards manual competency and 90 percent automatics competency?

Practice makes perfect and if the company policy is to stay on automatics from lift off to near touch down, then that only leaves the flight simulator for honing manual flying skills. Where simulator time is dictated by costs and company policy requires full use of automatics in the simulator, this leaves only a few minutes of effective time per session for the pilot to practice manually.

For example, there are many operators who regard simulator practice at unusual attitude recoveries in IMC as a total waste of time. Often the instructor hasn't got a clue how to instruct on these manoeuvres anyway. Which is one reason why there has been an increase in loss of control in IMC accidents in recent years.

Until authorities bite the bullet and insist more emphasis be placed on pure flying skills versus automatic pilot monitoring skills, the current trend towards loss of control in IMC will not reverse.

before landing check list
9th Jul 2011, 08:34
A37575, as you know there is no way to quantify what you are asking. However I do think that most of us are saying there is too much reliance of flying the aircraft through it's automation because most of the pilots now do not have the refined hands on ability that only comes with actually flying the aircraft (an aircraft) by hand.

Surely a captain or copilot pilot licensed to fly a type of aircraft should have 100 percent competency on both skills.

Surely somebody who knows nothing of the industry would imagine this, it does sound logical however we know this to be sometimes false. I do not know what your background is however some of us have spent a lot of time actually flying, and I do not mean hours monitoring a FMS and auto pilot. Also I do not mean to come across that a person with 2000 hours flying an ag plane makes a better airline pilot either. That is the other extreme,

I think the "balance" referred to here would be a pilot with enough practical knowledge in aerodynamics so as to know what is happening (not so much the minutia) and why it was happening and if it was not happening the way it was happening incorrectly would have no problem analyzing the situation correctly using all relevant data, coming up with a plan of action and not be afraid of hand flying the thing sometimes contrary to what we use as a bible called the SOP's.
How this person gets this knowledge and the intestinal fortitude required to put the plan into action usually comes from a diverse education, not just the academy approach and not just the utility approach but a knowledge based from the mix of the two, and not just those two.

Balance

EMIT
9th Jul 2011, 12:20
xcitation #1973

No, xcitation, I was not contradicting myself. The discussion about manual flying, as is referred to in this thread, is about the so called danger from an aerodynamic standpoint, i.e. too great sensitivity of flight controls, or eeeeeek "coffin corner"!

The danger of inaccurate flying in RVSM is risk of collision. That is irrelevant in the discussion about AF447.

Are you not contradicting yourself - in one post you write about flying AT cruise altitude, in another one you query me about flying ABOVE cruise altitude.
To be sure, initially, the AF447 was AT cruise altitude, their real problem started when they went far above it through the setting of an unusually high pitch attitude.

Setting that unrealistic pitch attitude may be the result of never flying manual at high altitude, it is not the result of manual flying at altitude being somehow dangerous or exceedingly difficult.

And totempole, writing posts like this does not put me into the category of self aggrandized aces, I hope? Don't worry, my religion is to be highly proficient in automatics AND in manual.
Autopilots however, do not need training or recency to stay proficient - when they are one day unproficient, they announce it with a failure light. Pilots look physically the same when able and proficient or when not recent or unproficient. That's why I take every opportunity to fly manual and sure, some times or places are not opportune.

chase888
9th Jul 2011, 22:06
The challenge is to be totally proficient in correcting all the anomalies with the automatics entirely or partially. The supreme rule is never ever getting into situations where you have to use your super self declared " acy profiency " to manually get out of situations where you have gotten the automatics into. In my years of training pilots I have seen proud " old aces " get the automatics into ****ty situations and then proudly clicking them off to fly manually, mostly to an untidy end. Their pride.....they didn't crash despite the " failed automatics ". Actually there was absolutely nothing wrong with the automatics in those instances; the problem was the self declared aces did not understand the proper use of the automatics and misuse the functions.

I suspect Totempole has hit the 447 nail fairly on the head.
Not suggesting the crew did what is suggested in his post above, but its a fact that manual flying did not work out on 447 unfortunately.

bubbers44
10th Jul 2011, 01:15
The reason AF447 had the problem is when the AP threw the flying to the PF, he didn't respond properly and zoomed it up into a stall. Knowing how to hand fly at high altitude acurately would have saved the day but apparently he couldn't. I don't know how hard flying at altitude with a side stick is but it is quite doable with a yoke. Have done it quite a few times. Sometimes we dispatched with AP inop with FAA blessings.

RWA
10th Jul 2011, 03:37
quoting Bubbers44:-


"The reason AF447 had the problem is when the AP threw the flying to the PF, he didn't respond properly and zoomed it up into a stall. Knowing how to hand fly at high altitude acurately would have saved the day but apparently he couldn't."


Bubbers44, I don't think we can draw those sorts of conclusions from the fragmentary and incomplete information so far provided by the BEA. In fact, the more I read that Note the more convinced I become that it was deliberately framed to suggest 'pilot error,' without actually providing much evidence. However, a careful reading reveals that the PF did NOT in fact cause the 'zoom climb.'

The first relevant paragraph says:-


"From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS)."


So the first thing that happened was the autopilot and autothrust signing off, and the speeds (and very probably other instruments) going haywire. The PF made a left nose-up input, probably to counter the aeroplane's incipient roll and maintain altitude. Please note at this point that the time that movement was made was '2 h 10 min 05.'

The next paragraph of the note refers to a pitch-up some considerable time (at least eleven seconds) later. Please note especially the section I have 'bolded.'


"At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]". The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left."

That paragraph does not refer to noseup inputs on the part of the PF before the 'zoom climb' - indeed, it says the complete opposite, that he countered the climb with nosedown inputs, and succeeded in more or less restoring level flight.

That, to my mind, leaves open the question of what caused the 'zoom climb' in the first place? The only thing one can say with any certainty is that, on the vestigial information provided by the BEA in the second quoted paragraph, it wasn't the pilot?

Then, of course, came the stall warning. And the PF seems to have responded by carrying out the prescribed drill at the time - 'TO/GA power and seek to maintain altitude.'

goeasy
11th Jul 2011, 05:21
The saddest realisation to me, on the limited info available, is that if this crew had resisted the urge to act, and just sat and watched, they may well all be alive today.

The hardest thing for any modern pilot today, is to NOT react to a screen full of warnings, and aural callouts, but to watch and fully assimilate the information available.

The 'hand-fly heros' may not have won this game either...

cwatters
11th Jul 2011, 07:19
The saddest realisation to me, on the limited info available, is that if this crew had resisted the urge to act, and just sat and watched, they may well all be alive today.

It's not clear that's the case.

Ian W
11th Jul 2011, 11:52
if this crew had resisted the urge to act, and just sat and watched, they may well all be alive today

From reading all of this and associated threads, it seems that there have been 3 incidents reported on these threads of Airbus aircraft apparently undemanded 'zoom climbing'.

The incident on approach to Paris may be different but resulted in the aircraft doing a wingover and recovering.
The incident where an A340 climbed past an A330 in a zoom climb during the day VMC and recovered.
AF447 appears to have zoom climbed to above the aerodynamic ceiling of the airframe. I am not sure that the system is designed to cope with suddenly being in the stall without any approach to it.


So it appears that something in the Airbus or handling can zoom climb the aircraft (has this happened with other types?)

I have only 'fallen out' above the aircraft ceiling in single jets where the aircraft were built for unusual positions and engine thrust had no pitch effect. If as everyone says the TOGA power would pitch the aircraft nose up, once that had been done and the aircraft started dropping stabilized but with an AOA that was on the wrong side of the drag curve, is it certain that there is sufficient aerodynamic authority in the controls to do a simple ND to recover?
Would the crew have to be more imaginative with large rudder deflection or even perhaps asymmetric thrust to put one wing down - and if they did that could they end up changing a stabilized stall into a spin?

It just seems to me that perhaps there was only one chance to recover from what happened and that was at the top of the zoom holding full nose down and reducing power which should have bunted the aircraft back into a flyable state. But the 'standard' stall recovery of NU to 5deg and TOGA was precisely the opposite.

Lonewolf_50
11th Jul 2011, 12:27
Practice makes perfect and if the company policy is to stay on automatics from lift off to near touch down, then that only leaves the flight simulator for honing manual flying skills.
Where simulator time is dictated by costs and company policy requires full use of automatics in the simulator, this leaves only a few minutes of effective time per session for the pilot to practice manually.
There's a problem. Use of full automatics in the sim. Seems to me that sim sessions ought to emphasize training scenarios one can't do in the aircraft.

For example, there are many operators who regard simulator practice at unusual attitude recoveries in IMC as a total waste of time. Often the instructor hasn't got a clue how to instruct on these manoeuvres anyway. Which is one reason why there has been an increase in loss of control in IMC accidents in recent years.
Until authorities bite the bullet and insist more emphasis be placed on pure flying skills versus automatic pilot monitoring skills, the current trend towards loss of control in IMC will not reverse


How can such a fundamental flying skill set be a waste of time?
Is this a symptom of institutional worship of autopilot?

This scares the hell out of me.

I am required to fly commercially next month to the east coast for a business meeting. You are suggesting that in some companies, skills necessary for IFR competency are being institutionally neglected, and allowed to atrophy. The flying public need to be warned.

RWA,
Then, of course, came the stall warning. And the PF seems to have responded by carrying out the prescribed drill at the time - 'TO/GA power and seek to maintain altitude.'
Ian W
It just seems to me that perhaps there was only one chance to recover from what happened and that was at the top of the zoom holding full nose down and reducing power which should have bunted the aircraft back into a flyable state. But the 'standard' stall recovery of NU to 5deg and TOGA was precisely the opposite
.
The training issue.
IF stall training is restricted to "near the ground environments" THEN the one time you stall at altitude you are playing catch up.

Based on a number of incidents related in the past two years on this topic, some crews in the past have caught up, this crew was unable to, as were some of the others in the past.

The question is, does BEA cover this in the final report? How much emhpasis?

We shall see.

DC-ATE
11th Jul 2011, 14:41
Lonewolf_50
I am required to fly commercially next month to the east coast for a business meeting.

There's always AMTRAK. Great way to travel even it it takes a little longer.

Lonewolf_50
11th Jul 2011, 17:47
I agree, but my company does not. :mad:

cwatters
11th Jul 2011, 22:23
How can such a fundamental flying skill set be a waste of time?

I agree with you but I wonder how many glider pilots would check the trim wheel position in the middle of recovering from a stall? Bet most would wait until they had recovered to S&L.

bubbers44
11th Jul 2011, 22:34
Autotrim on a sailplane?

RWA
12th Jul 2011, 02:15
Quoting Ian W:-


"The incident where an A340 climbed past an A330 in a zoom climb during the day VMC and recovered."

I think you've 'found the smoking gun,' Ian W, congratulations.



For 18 seconds after the autopilot disengaged the aircraft remained within 200 feet altitude of FL 360 but once AoA law was invoked at 14:21:50 hrs, the aircraft's attitude began to pitch nose-up. The pitch-up trend continued for 17 seconds reaching a peak of 15° nose-up shortly before the first nose-down sidestick command was applied. Throughout this phase the aircraft climbed rapidly (reaching a peak rate of about 6,000 ft/min) due to the increase in lift created by the flight control system's capture of alpha prot. The aircraft reached its apogee at FL 384 at 14:22:28 hrs where the airspeed had decayed to 205 KIAS and 0.67 Mach even though full thrust had been applied.

-----------
The crew subsequently descended back to FL 360 and successfully re-engaged the autopilot and autothrust systems.

That isn't referring to the AF 447 accident. It's from the British Air Accident Investigation Board's report on the 2000 A340 Atlantic 'zoom climb' incident you mention.

Apparently the autopilot and autothrust disengaged on that occasion too. The 'zoom climb' was triggered by the aircraft going into 'Angle of Attack' Law (yet another law for us to half-understand :)).

http://www.rvs.uni-bielefeld.de/publications/compendium/incidents_and_accidents/ACAS-AAIB-dft_avsafety_pdf_501275.pdf

I find it very interesting that the 'protections' began to zoom-climb the A340 18 seconds after the autopilot and autothrust disengaged. That's just about exactly the same time that the AF 447 zoom climb commenced, as shown by the excerpts from the BEA Note that I quoted above.

EMIT
12th Jul 2011, 02:47
On the quotes about the A-330 / A-340 zoom climb Airprox incident in NAT RVSM airspace:

Read the report, then you will find great differences with the AF447 case. This Airprox case was a situation with moderate to severe turbulence, large wind speed fluctuations that caused large speed (and Mach) variations and those initiated the incident. One such speed fluctuation caused AOA to increase to Alpha protect, etcetera.

There is no occurrence of the ERRONEOUS speed values that AF447 experienced, no LOSS of valid speeds, etcetra.

The cases are completely different, although the quotes try to make them similar.

RWA
12th Jul 2011, 03:32
Quoting EMIT:-


One such speed fluctuation caused AOA to increase to Alpha protect, etcetera.

There is no occurrence of the ERRONEOUS speed values that AF447 experienced, no LOSS of valid speeds, etcetra.

Oh dear, EMIT :).

AF 447's speed readings were 'fluctuating' too; I don't somehow feel that it matters whether they were also 'erroneous' or not.


"The cases are completely different."

My own feeling is that there appear to have been only two obvious differences beween the two cases:-

1. The A340 only zoom-climbed at 6,000ft./min., whereas AF 447 zoom-climbed at 7,000.

2. The A340 crew were fortunate in that they were operating in daylight and no doubt had a visible horizon to work with.

But OK - if the 'systems' didn't cause the AF447 upset, what (in your opinion) did?

before landing check list
12th Jul 2011, 03:58
For 18 seconds after the autopilot disengaged the aircraft remained within 200 feet altitude of FL 360 but once AoA law was invoked at 14:21:50 hrs, the aircraft's attitude began to pitch nose-up. The pitch-up trend continued for 17 seconds reaching a peak of 15° nose-up shortly before the first nose-down sidestick command was applied. Throughout this phase the aircraft climbed rapidly (reaching a peak rate of about 6,000 ft/min) due to the increase in lift created by the flight control system's capture of alpha prot. The aircraft reached its apogee at FL 384 at 14:22:28 hrs where the airspeed had decayed to 205 KIAS and 0.67 Mach even though full thrust had been applied.

-----------
The crew subsequently descended back to FL 360 and successfully re-engaged the autopilot and autothrust systems



To tell you the truth I have no idea what "Alpha Prot" is nor does it really matter. I do know that for whatever reasons autopilots do strange things; due to a software error, stray trons floating around, faulty sensors etc. My question is this; Did the crew have access to reliable information as to what the aircraft was doing at the time either through the primary instrumentation or the standby and if so did they have control authority to put the aircraft where it needed to be or was it really out of control?
If they did have access to the actually flight path information of the aircraft and if they had access to the control of the aircraft why did they let it diverge so much for so long?
Now I am assuming they were night, IMC and kinetics should not used but if they knew something was amiss for whatever reason why did they not respond earlier? 18 seconds and close to 3000 vertical feet is a long time/way.

1. The A340 only zoom-climbed at 6,000ft./min., whereas AF 447 zoom/climbed at 7,000.

2. The A340 crew were fortunate in that they were operating in daylight and no doubt had a visible horizon to work with.

But OK - if the 'systems' didn't cause the AF447 upset, what (in your opinion) did?


If the systems did cause the initial upset but the pilots failed to react in a timely manner and control and correct flight path information was available to them, then poor training did them in. If the systems did cause the initial upset but control/flight path information was not available to them then it was/is a design flaw.

cwatters
12th Jul 2011, 06:38
Autotrim on a sailplane?

Thats the point, there isn't one so you don't get to learn how dangerous having one can be.

Lonewolf_50
12th Jul 2011, 11:46
RWA, from the discussions over at tech log, Alpha Protect works in normal law. At some point early in the AF 447 event, the pilots reported alternate law. At that point, Alpha Prot should not have been a factor in the behavior of the aircraft.

EMIT
12th Jul 2011, 12:16
Quote RWA

The A340 crew were fortunate in that they were operating in daylight and no doubt had a visible horizon to work with.

Remark EMIT: the Artificial Horizon is a perfect replacement for the Natural Horizon, the AI is used 100 % of the time during night and IMC conditions. A pitch of 15 degrees nose up is visibly crystal clear on an AI and is highly unusual in a civvie airliner at FL 350. The suggestion of another poster that maybe, the line Pitch 15, Thrust TOGA was inappropriately "quoted" inside the PF's head might hold some value. (the quoted pitch/power combination is the one to use in case of speed indication loss just after lift-off).

Quote RWA
But OK - if the 'systems' didn't cause the AF447 upset, what (in your opinion) did?

Remark EMIT: IF after all, the PF did not himself STEER the a/c into the zoom climb, then at least he should have seen the pitch change to 15 degr nose up, a very inappropriate pitch at that altitude, and should have tried to steer that pitch down to a normal value of 2 or 3 degrees above the horizon. This was not done, a lot of backstick was maintained.

Even though stall warnings, speeds or whatever were rightly or wrongly blaring, every big jet pilot must know that 15 degrees nose up at FL 350 is not gonna work in the long run (longer than a few seconds).

bubbers44
12th Jul 2011, 12:30
EMIT, hopefully the BEA final report will be a lot more informative than their last one. It lacked any meaningful information for some reason. They had all the data but it was like the guy who wrote it was getting off shift in 15 minutes and had a hot date and couldn't be bothered by details.