AF447 final crew conversation - Thread No. 2

[john_tullamarine]

Link to Thread No. 1 (http://www.pprune.org/tech-log/466259-af447-final-crew-conversation-thread-no-1-a.html#post6749746)

[PJ2]

Thanks for the link, John.

HN39;

I won't forget our early exchange on stall AoA and later also with Owain Glyndwr the effects of Mach on AoA and buffet thresholds. The discussion had a profound effect on my understanding of my airplane and of high altitude-high speed flight and AF447 specifically. I would recommend to anyone wanting to know more from those that really do know their stuff, to find this and other exchanges with these two posters.

Re, "...would it help prevent future accidents if sophisticated Flight Guidance and Aircraft Monitoring systems, having rejected three sources of airspeed information as unreliable, and 'knowing' conditions such as configuration, weight and altitude, provide more specific information as to the appropriate response?"

I need to think about it! ;-) Along with weight, altitude & configuration it would use AoA and perhaps also have a running historical window, say the last five or ten minutes, of all relevant indications upon which to build a "safe envelope"? Just thinking out loud.

Initially I think, Yes, it would help, but in the Birgenair and Aeroperu cases more than here. Reason I say this is, most of the Airbus UAS events lost airspeed indication for less than two minutes and from what can be gleaned from the Interim Report 2, those crews affected didn't seem to do anything but wait.

Because pilots are creatures of visual, auditory and tactile habit, a switching to a "novel" presentation may present as much surprise as the event itself and take a moment to get used to...which means it also has to be trained in the sim, which available time these days is heavily-challenged already.

But the Birgenair/Aeroperu cases are completely different and I think such a system/presentation would have saved the aircraft.

Organfreak;

I didn't watch the BBC series, preferring the BEA work plus some discussions on the side. I prefer original sources to anything that will perhaps innocently but most assuredly have a point of view and a theory and must keep an audience entertained to be economically viable. I avoid the "Discovery Channel" kind of stuff for this reason. The needs of television are not those of good investigations because such work is enormously detailed and for most, tedious and certainly would not entertain. "The story" is certainly interesting and I can see where those not familiar with the event would enjoy learning about it though and getting enough from such programming to ask further questions.

Not sure if the BBC was showing Vasquez's work, but it showed up early here and was an enormous help in understanding the weather aircraft transiting the ITCZ deal with on a regular basis.

[jcjeant]

Hi,

The needs of television are not those of good investigations because such work is enormously detailed and for most, tedious and certainly would not entertainWell .. here's yet another has appeared in a few days .. and in which journalists claim to show how the accident really happened :ok:
In this new survey Exhibits reveals what really happened during the last 4 minutes of flight Rio / Paris. The final report of the BEA about what happened in advance ... :)
Google Traduction (http://translate.google.be/translate?sl=fr&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.lezappingdupaf.com%2Farticle-pieces-a-conviction-revient-en-mars-sur-le-crash-du-vol-af-447-rio-paris-99824903.html&act=url)

Pièces à conviction revient en mars sur le crash du Vol AF 447 Rio / Paris - Le zapping du PAF (http://www.lezappingdupaf.com/article-pieces-a-conviction-revient-en-mars-sur-le-crash-du-vol-af-447-rio-paris-99824903.html)

[mm43]

Originally posted by PJ2..

I won't forget our early exchange on stall AoA and later also with Owain Glyndwr the effects of Mach on AoA and buffet thresholds. The discussion had a profound effect on my understanding of my airplane and of high altitude-high speed flight and AF447 specifically.I must admit I was impressed by Owain Glyndwr's well thought out dissertation on THS v Elevator, AoA and Mach buffet, and some time ago took the liberty of putting a couple of his posts together as a webpage.

THS v Elevator and AoA (http://countjustonce.com/af447/af447-alpha-dq.html)

[roulishollandais]

THS v Elevator and AoA (http://countjustonce.com/af447/af447-alpha-dq.html)
Thank you..........

[roulishollandais]

I prefer original sources
That for are we Ppruners !

[Lyman]

It might be esoteric, but what I got from Owain was two behaviours. In the long term, the a/c has an all flying tailplane. In the short term, the a/c has a standard PITCH control, one that degrades to "neutral" over time. The aircraft is always seeking cruise, (or attitude: establish), and this conflicts with the need to maneuver, at times.

Which could lead to confusion, unless the configuration (instant) can be sussed visually (screen), or by feel? "What's it seeking?"

Why would this a/c seek to "establish" and hold an attitude that required constant attention from the handling Pilot? An attitude that was intended to be short term, perhaps? PF had the ROLL under control because he knew what was going on, albeit badly. Right, wrong, or sideways, he did NOT get what the PITCH required. This speaks to the a/c's programmimg in ALII. For whatever cause, the handling pilot was unable to 'get'. Is the a/c always correct?

Just a question.

[Organfreak]

Lyman:
The aircraft is always seeking cruise...

In ALT2???

:suspect: :sad: := :( :hmm:

[Owain Glyndwr]

Lyman

Quote:
[what I got from Owain was two behaviours]
unquote

Wherever you got that, it wasn't from me!

Even in Alt2 the C* law is a manoeuvre command system for goodness sake. The control laws don't 'seek' anything. They hold what's there until told by the pilot to change it. There is no conflict except in your mind.

[Lyman]

Owain.

If from the initial PITCH up command, the THS had been trimming the command, the a/c would have STALLED well before the top of climb, where there was no energy left, and the STALL was unfelt, unobserved (per your comment).

Had it not remained at -3.4, then, the a/c would have fallen out, buffeted, and the two man crew would be left with inescapable evidence that STALL recovery was a necessity. Point of fact, the a/c would have recovered on her own had she been allowed to STALL. Instead, the a/c drained energy until at full power, when it mushed into an attitude that was to remain until water contact.

After the loss of energy, the THS then started to trim in NU, and remained at 13.2 (-) until water contact. It stands to reason A) you are not wrong, and B), the lack of SA, CUES, and CRM prevented the crew from sussing the STALL.

No judgment, no accusation. It remains that had the a/c STALLED earlier, the cues would have been present and the outcome may have been different. No?

[RR_NDB]

A33Zab

@RRR:
Don't know what you mean with 'sub'heated, its self temp. controlled.
The heat applied is inversely proportional to the temperature of the probe.

Will post on the subject applied to:

1) Sub heated Pitot's
2) RH not recorded

I am elaborating and will post ASAP.

[Owain Glyndwr]

Lyman,

I'll give it one go then I'm back into hibernation.

[quote] If from the initial PITCH up command, the THS had been trimming the command, the a/c would have STALLED well before the top of climb, where there was no energy left, and the STALL was unfelt, unobserved (per your comment). [unquote]

You keep writing as if the THS has a life of its own. It hasn't. It is slaved to the elevator through an integral term (see the block diagram PJ2 posted a while back). It WAS trimming in the initial phase of the second stall approach - it moved from around 2.5 deg to around 3.4.

It matters not one jot whether the pitching moment comes from elevator, THS or some combination thereof. The aircraft responds to the total pitching moment commanded by the pilot and there is absolutely no evidence to the contrary. That being so, the THS movement would have no effect on the point at which the aircraft stalled - it was merely sharing out the commanded pitching moment to minimise elevator movement.The time at which stall occurred was driven purely by pilot input as a commanded 'g' history.

I did NOT say the stall was unfelt or unobserved. I said that it was difficult to distinguish between turbulence buffet and stall buffet and that there were no pitching moment breaks. As a nonpilot writing in a professional pilot's forum I try to avoid sticking my neck out where it can get chopped off, so I was careful to say that the other clues indicating stall (high attitude, inability to arrest rate of descent) were best left to pilots to evaluate.

I did not add of course that there was this little matter of a voice calling STALL STALL every five seconds or so.

All in all I cannot accept that the stalled condition was unrecognisable.

[quote] Had it not remained at -3.4, then, the a/c would have fallen out, buffeted, and the two man crew would be left with inescapable evidence that STALL recovery was a necessity. Point of fact, the a/c would have recovered on her own had she been allowed to STALL. Instead, the a/c drained energy until at full power, when it mushed into an attitude that was to remain until water contact.[unquote]

Since stall AoA is independent of THS setting, your argument won't hold. The aircraft WAS allowed to stall and it did buffet. Just allowing the aircraft to stall won't get you out of it unless you remove the pitching moment that is holding you in there. This didn't happen.

[quote] It stands to reason A) you are not wrong, [unquote]

True ;)

[quote] and B), the lack of SA, CUES, and CRM prevented the crew from sussing the STALL. [unquote]

Also truehttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/puppy_dog_eyes.gif

[quote]No judgment, no accusation. It remains that had the a/c STALLED earlier, the cues would have been present and the outcome may have been different. No?[unquote]

No

[RR_NDB]

Hi,

Owain Glyndwr,

In your opinion what kind of improvement(s)* could and should be made to the aircraft Systems in order to effectively "help" the crew in similar situations in respect to THS operation.

Kudos for your analysis. (http://countjustonce.com/af447/af447-alpha-dq.html)

Rgds

(*) Algorithms, indications, etc.

[fizz57]

"DON'T PULL" flashing on the PFD in time with the stall warning?

[RR_NDB]

Hi,

Feedback loops are designed (and potentially capable) to improve a System.

For example, the AS probes in auto mode receives just the required electric power.

Feedback loops are designed with "time constants" and eventually with techniques like hysteresis. The engineering takes into account essential aspects like stability, etc.

I posted some comments assertively saying the AS probes the industry is still using, are "subheated".

I am based in several facts and i can discuss each one when necessary.

I have some questions to the Pilots (daily facing UAS threaths) and to the Technicians here:

1) Is the power being applied to the AS probes enough in order to their proper operation?
2) The delay between a sudden atmospheric temperature drop and the "reheating" of the probes could explain the "failures" leading to UAS?
3) The differences between US and FR probes may be explained by "different" time constants?
4) Is the max power sufficient to provide a safe operation in most environments?

Is there "recording capability" in current Systems in order to analyze the UAS incidents more precisely?

Could be better to enter WX using MAX instead of AUTO? (Operating "open loop")?

[lomapaseo]

RR NDB

1) Is the power being applied to the AS probes enough in order to their proper operation?
2) The delay between a sudden atmospheric temperature drop and the "reheating" of the probes could explain the "failures" leading to UAS?
3) The differences between US and FR probes may be explained by "different" time constants?
4) Is the max power sufficient to provide a safe operation in most environments?



good start but to better understand what questions are applicable first search on High altitude "ice crystals" in aviation

I suspect that you may better understand the time differentials between sensing and applying enough heat.

Note that you car windscreen will still ice up and then shed while the defroster is on high, as the sleet density vs your speed changes rapidly.

[RR_NDB]

lomapaseo,

i suspect US probe is "faster" to adapt to a "new environment".

The max power is the same to both probes.

Anyway i will go deep in this subject as you suggested.

IMHO the System should be STABLE under "brief failures". Like AS probes anomalies.

[RR_NDB]

Hi,

I suspect that you may better understand the time differentials between sensing and applying enough heat. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a.html#post7060071)

In AUTO mode you will have a delay from "sensing" to "correct" to the required probe temperature.

if you apply maximum available power, ("open loop condition") no delay at all :)

At which cost? Roughly 1 KW being used, i estimate.

And the environment is frequent, i understand.

Are you saying is difficult to decide (System or crew) when apply max power?

[HazelNuts39]

1) Is the power being applied to the AS probes enough in order to their proper operation?Not sure that I understand the question. If the amount of heat is the problem, then it was obviously not enough to prevent blockage of the pitots in the particular conditions encountered by AF447. However, as stated by PJ2's #1420 in thread no.1: The problem of momentarily blocked pitot tubes is extremely rare. Appendix 7 of the BEA Second Interim Report, which see, lists the events which occurred to Airbus. (...) but given the millions of ice-crystal-cloud-penetrations that occur each year without result, "avoiding all cloud" isn't realistic.2) The delay between a sudden atmospheric temperature drop and the "reheating" of the probes could explain the "failures" leading to UAS?The recorded data show the opposite of a temperature drop. At 02:09:30 the temperature was ISA +10.6°C, trending downwards (Interim #3, p.48), and at 02:10:00 it was ISA +15.6°C (p.86).

[RR_NDB]

Hi,

HazelNuts39,

Not sure that I understand the question. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a.html#post7060236)

Is the power being applied to the AS probes enough in order to their proper operation?

The power UNDER STEADY STATE CONDITIONS (operating at MAX POWER) is enough?

Operating at MAX power there is no delay, i.e. you are in a "open loop" mode wasting energy and stressing materials when not necessary.

I guess the max available power is enough. (Just guessing).

And i suspect the amount of heat are not being sufficient when encountering ice. This "encountering" was mentioned to be heard on CVR.

I took into account PJ2 post when formulating all 6 questions,

The problem of momentarily blocked pitot tubes is extremely rare. Appendix 7 of the BEA Second Interim Report, which see, lists the events which occurred to Airbus. (...) but given the millions of ice-crystal-cloud-penetrations that occur each year without result, "avoiding all cloud" isn't realistic.

The recorded data show the opposite of a temperature drop. At 02:09:30 the temperature was ISA +10.6°C, trending downwards (Interim #3, p.48), and at 02:10:00 it was ISA +15.6°C (p.86).

I am talking in the transient, just after noise increased in CVR due ice crystals "collisions" to windshield an nose cone surfaces.

I also took into account the recorded temperature, (higher than expected and imposing a FL375 REC MAX) not relevant to my rationale. I am looking to the transient, the so called t0+, just after encountering ice crystals when the heat MUST BE PRESENT immediately to assure proper AS sensors operation.

[RR_NDB]

Hi,

F-GZCP was operating with Pitot heating in which mode? Auto or manual mode?

This was mentioned in BEA reports on AF447 case?

FDR records enough data on this issue?

In other 32 UAS incidents Auto mode was selected, as recommended (default)?

Most crews use Auto or manual mode when closing in specific WX conditions?

The timing required for AP/ATHR quit is "compatible" with "heating time constant" of probes when encountering ice crystals when auto mode is selected?

PS

If the temperature BEFORE encountering ice crystal is higher (as in this case) WORSE.

The "required heat" will takes longer to set in the probes.

The recorded data show the opposite of a temperature drop. At 02:09:30 the temperature was ISA +10.6°C, trending downwards (Interim #3, p.48), and at 02:10:00 it was ISA +15.6°C (p.86).
(http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a.html#post7060236)

Therefore a fact in that flight.

[HazelNuts39]

RR NDB;

Where do you see a drop in temperature? "The background noise changed rapidly around 2 h 09 min 46." (p.73). The ice crystals have the same temperature as the air that carries them. Several UAS reports* notice a sudden rise in temperature, which is to be expected because the rising air in which the ice crystals are formed derives its buoyancy from being warmer than its surroundings. See also Tim Vasquez' (http://www.weathergraphics.com/tim/af447/) temperature profile at FL 350.

(*)From Interim #2 p.52:
The recordings of total or static temperatures(9) show increases of ten to
twenty degrees during the event, which sometimes began before noticing
any speed anomalies, except in a case where the increase was lower;

[A33Zab]

if you apply maximum available power, ("open loop condition") no delay at all

You will locally heat-treat the neighboring skin with insufficient cooling.

I don't have exact data for the probe, but AOA operating temp is 120 ºC,
suppose this will be the same for the probe.
---

Don't have sleepless nights about the probes anymore.
The affected thales probes are obsolute and replaced by other probes per AD 2009-0195.

After 07 January 2010, do not install a Thales Avionics P/N
C16195AA pitot probe at any position on an aircraft.



System is automatic, on ground 115V to the Low side if 1 engine is in run state.
115V is applied to the Normal side in Flight.
Manual switch (from AUTO to ON) bypasses the Engine Run & Flight logic.
Temp controlled by the probe itself, the PHC contains the switching logic and monitoring circuits.

[RR_NDB]

Hi,

HN39,

Will process pertinent information and review my books on the subject before. Thanks for questioning. Will answer ASAP.

A33Zab,

You will locally heat-treat the neighboring skin with insufficient cooling.

Any other implication if we cross the specific WX area in MANUAL mode?

Don't have sleepless nights about the probes anymore.

:)

Question for you:

Time constant of the "closed loop" configuration when AUTO mode is selected for Pitot heating seems relevant to be take into account in the 30+ UAS cases?

What is your feeling on this particular point.

I remembered of this possibility when preparing second post on "Transient": Transient in Feedback Systems (II)

Regarding FD data just after UAS (in the transitory)

Related to "What PF saw at his (RH) side", not recorded.

[Owain Glyndwr]

RR NDB

Quote: [In your opinion what kind of improvement(s)* could and should be made to the aircraft Systems in order to effectively "help" the crew in similar situations in respect to THS operation.]

Nothing other than the obvious I'm afraid.

In normal law any further THS nose up movement is inhibited when alpha protect switches in. I can't for the life of me see why this logic was not carried over to Alternate and stall warning respectively.

Apply this simple change and I suspect that most of the other controversial points discussed in earlier threads decline into insignificance.

[Owain Glyndwr]

Don't you think that the problem might be both more subtle and more complex than just the amount of heat applied?

Why did it seem to be almost limited to one particular design of probe? (well by about 10:1 anyway)

What was peculiar about that probe? It must I think be critically dependent on the shape and finish of the probe internal geometry which is a closed book to all except the probe manufacturers.

It wasn't blockage of the drainhole by ice because the sensed pressure dropped to ambient static; so the blockage must have been upstream of that. Did the crystals melt and refreeze? Are the internal diameters critical? Or the radius at the corner of the 'L'? Or the actual location of the drainhole? Would the distribution of the heating along the length of the 'horizontal' bit of tube be important? When they went to the AA probe Thales also made some changes to the surface finish to improve corrosion resistance. Was this important?

I don't know - does anybody else?

[RR_NDB]

Hi,

Owain Glyndwr

Don't you think that the problem might be both more subtle and more complex than just the amount of heat applied? (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-2.html#post7060655)

Certainly is for both FR and US probes

Why did it seem to be almost limited to one particular design of probe? (well by about 10:1 anyway)

Both probes showed limitations. My feeling is:

FR, probably many factors, like you put (geometry, etc)

US, less critical and probably requiring a little bit more heat when facing conditions near limit.

Look, i am trying to simplify (not always possible) because the AS probe principle of operation is VERY SIMPLE. What you need:

-A "certain geometry" (Henri Pitot invention)

-Heating above a certain threshold when facing conditions near limit.

-Other characteristics derived from the environment (moisture, heat, need to drain, etc.)

The short duration of the "failures" suggest that:

The heating may be near the required amount or not being applied fast enough due thermal inertia due geometry, geometry of the "heater" or a combination of aspects related to thermal characteristics.

I am anxious to analyze deeply the 30+ UAS cases to look for:

AUTO or ON mode selected and recorded (consistent) data during the transitory.

I understand the valid information is not recorded during the incidents like AS SIMPLY not measured in AF447.

I don't know - does anybody else?

My feeling is, we are near the required heat. Statistically based and considering AS probes (simple devices) did not fail. Just a brief erratic output.

Did the crystals melt and refreeze? Are the internal diameters critical? Or the radius at the corner of the 'L'? Or the actual location of the drainhole? Would the distribution of the heating along the length of the 'horizontal' bit of tube be important?


Good questions. I don't know.

In normal law any further THS nose up movement is inhibited when alpha protect switches in. I can't for the life of me see why this logic was not carried over to Alternate and stall warning respectively.

Thank you for direct answer!

Rgds,

[A33Zab]

Any other implication if we cross the specific WX area in MANUAL
mode?



No, switch to ON bypasses the auto logic but is the same circuit as in flight and at least 1 eng in RUN state.

The figure explains the function of switch and logic:

http://i474.photobucket.com/albums/rr101/Zab999/ProbeHeat.jpg

[Machinbird]

Temp controlled by the probe itself, the PHC contains the switching logic and monitoring circuits.
Thank you for the schematic. Looks like the probe temperature of the probe is controlled by the actual heater coil itself which is probably made like a an old style wire wound ballast resistor. The temperature coefficient of resistance would then regulate the current & heat. The PHC is just switching the units between On and Off, ground and air mode, and also monitoring the current to be sure each heater is actually working and has not burned open.

I have an old Rosemount pitot probe on my desk, and although these things look fairly uniform between models, there is all sorts of room for variation as to how thick the metal is in various areas (controlling the thermal mass and time constant to conduct heat to the other side), input wattage, heating coil location, what metal is used, and where the drain holes are relative to the elbow and heat sources.

I would think they would avoid putting the heating coils where moisture can actually impinge since you would then be generating steam and pressurizing the probe.

The 3 channel design of the Airbus does provide sensible redundancy for everything downstream of the probes, but no real redundancy for a common mode sensing problem. A better design would involve alternative sensors such as a laser airspeed sensor (but I note that several websites touting such equipment a couple of years ago are now out of service).

Another concept would be to place the probe behind a vane that would bend the airflow into the pitot inlet, but which would centrifugally separate ice particles so that they would miss the inlet for reasonable yaw angles under cruise conditions.

In normal law any further THS nose up movement is inhibited when alpha protect switches in. I can't for the life of me see why this logic was not carried over to Alternate and stall warning respectively.
Amen to that.
It is if someone in conceptual design had decided that the AOA systems were not to be trusted.

Apply this simple change and I suspect that most of the other controversial points discussed in earlier threads decline into insignificance.
Fully in agreement. :ok:

[Owain Glyndwr]

[Certainly is for both FR and US probes]

I hate to confess ignorance, but FR probes? US probes? Either side of the Atlantic or something else?

[Both probes showed limitations.]

Agreed, but one design (from a maker with a previously good record) starts to show problems after being in service for what, seven years? I am not aware of any changes to route structure and if you exclude global warming :) the atmosphere hasn't changed much, so what did? I don't think one can rule out some sort of time dependent change in the physical state of the probes.

[Look, i am trying to simplify (not always possible) because the AS probe principle of operation is VERY SIMPLE.]

Again agreed, but as always the devil is in the detail

[The short duration of the "failures" suggest that:

The heating may be near the required amount or not being applied fast enough due thermal inertia due geometry, geometry of the "heater" or a combination of aspects related to thermal characteristics.]

Again agreed, and Machinbird's listing of the possible apparently minor variations in probe design is exactly what I had in mind when I suggested the answer might be too subtle for outsider analysis (but we still try!)

Like RR NDB, I feel that the heat being applied is probably near what is required, since the UAS events have been transitory, but it may not have been applied in the right area. I have heard of problems on other aircraft where pitot icing was linked to the absence of an insulating washer between probe and fuselage. Extrapolating that thought, the fuselage (and the unheated parts of the probes) constitute a thermal mass that would be at much lower temperature than the heated part of the probe. There will be a temperature gradient along the probe and maybe the details of that matter.

I must say that this is one of the more sensible discussions on this threadhttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/wink2.gif

Machinbird
[It is if someone in conceptual design had decided that the AOA systems were not to be trusted. ]

Which is not consistent with the exhortations to "Believe the stall warning". If AoA is good enough for triggering stall warning it is good enough to freeze the THS.

PS - could somebody please remind me how to put quotes in those little blue boxes?

[rudderrudderrat]

Hi Owain Glyndwr,

Good to read you back again. Highlight the text and click the 3rd symbol (between mountain picture and #)

The technical solution to the pitot icing problem has probably been solved already.

I'm more bothered about a technically qualified crew who didn't know what attitude they needed to maintain FL 350 after they lost the FD guidance.

[Owain Glyndwr]

Thanks RRR

The technical solution to the pitot icing problem has probably been solved already.


Very probably - wouldn't it be nice to know how ;) But at least they now have definitive icing requirements that cover the problem altitude/temperature bands

I'm more bothered about a technically qualified crew who didn't know what attitude they needed to maintain FL 350 after they lost the FD guidance.

Quite!

[roulishollandais]

The figure explains the function :Dof switch and logic
:D

Thank you !!! I like to see finally inside of inside !

Specifications :ok: :ok:are often written only when the project is finished ! It is a good thing, that means that we can cross out, delete, change what is wrong in the "philosophy" of the aircraft : We don't fly "philosophy":}. We don't fly ideology. :}

[Machinbird]

My key takeaway from A33Zab's schematic is that there is no direct feedback from any of the probes controlling the power level. Temperature control is reactive rather than proactive. If there were temperature feedback sensors in the probe, it would be possible to more finely control the probe power input. That is where the next big area for improvement in Pitot tube design/performance lies.
All the PHC does is supply 115 V to the Flight or Ground circuits of the Probe heater . There is no High or Low setting as some may understand the concept.

[A33Zab]

Quote:



Originally Posted by A33Zab


The figure explains the function :Dof switch and logic


:D


Thank you !!! I like to see finally inside of inside !


It proves Airbus is K.I.S.S.!

The switch needs only to be touched to ON in de-icing like PJ2 stated and if dual or all PITOT HEAT FAIL message is shown.


Temperature control is reactive rather than proactive


Uhhh...isn't that what is inherent to feedback controls? You need a certain deviation to correct the situation.
(we are awaiting RR_NDB Transient in Feedback Systems (II))

Proactive......than you call it predictive! or not?
if any possible UAS is predictive, wouldn't it be better to DONT GO THERE?

I don't have the pitot internals by hand but the low heat (ground) setting is to protect the A/C skin when less cooling is available.

[Machinbird]

Temperature control is reactive rather than proactive.
Uhhh...isn't that what is inherent to feedback controls? You need a certain deviation to correct the situation.
(we are awaiting RR_NDB Transient in Feedback Systems (II))
OK, Looks like I need to explain the situation better.

One form of current stabilization (old fashioned now but I have used it in equipment) is the old fashioned wire wound ballast resistor. As the current goes up, the temperature of the wire windings goes up, the resistance of the specially selected wire increases and limits the current. These things generally operate at a dull red glow. They are likely using this type system internally for pitot heat stabilization/regulation.

No moving parts, no electrical connection other than normal regulated voltage power supply, and you get a heat source. Properly selected, it is a simple means of generating heat for situations that are entirely predictable and slow changing. The aircraft climbs to altitude, the probe cools a bit, the wire cools a bit and the current increases which increases the power input. KISS to the extreme. To increase the power further, you need to increase the voltage.

The problem occurs when the heat demand changes rapidly. In the case of AF447, we had 19 seconds between the sound of ice crystals impinging and the AP disconnect. It took some time for the ice crystals to cool the probe internal surface and then the heating coils enough so that the power would then increase and melt the ice. When overloaded with ice crystals, this type probe goes through cycles of icing, melting, purging the melt water, and icing again.

If the icing had been detected in the first couple of seconds by a thermocouple, the power could have been cranked up then to meet the new demand before the blockage occurred, but this means that probe heating would be solely under the control of an external control system using feedback to sense and defeat icing. The dynamic control range would be much higher.

This is my take on what is likely the means of pitot tube heat control based on the evidence of the schematic you posted A33Zab. The externally controlled feedback system is probably what is needed to fix the problem.

[HazelNuts39]

If the ice particles are like snow flakes, they may not conduct heat very well between the heated wall of the tube and the space within.

P.S.
How much heat is required to melt 1.6 grammes of ice at -40°C? (Tube opening diameter 10 mm, 20 s at TAS 250 m/s, TWC 4 gm^-3 (NPA 2011-03), 100% catchment efficiency)

[lomapaseo]

P.S.
How much heat is required to melt 1.6 grammes of ice at -40°C?

Isn't the challenge to melt XX grammes per second ?

The meltal temp may be above ice-melting but the 3rd or fourth layer of ice crystals hasn't begun to feel it yet.

My grand daddy use to tell me about sleeping in an unheated drafty room on a cold snowy night with layers of blankets to keep him warm, yet the snow flakes would still glisten on the outside layer

[rudderrudderrat]

Hi HazelNuts39,

Assume snow requires 4.18 J/(g•K); & Latent heat of fusion of ice is 333.55 J/g

Then 1.66gm ice at -40 would require 4.18*1.66*40 = 277 J to be raised to 0C as ice.
Plus 1.66*333.55 J to melt at 0C = 554 J.
Total = 831 J.

If that amount of snow could accumulate in 20secs, then in 1 hour you would need 149,580 J or extra power source of about .04 KWh.

It doesn't sound much - but I can't spot the error.

[Lyman]

I'm with lomapaseo. The problem is rate, not temp. Tightly packed granular microcrystalline water ICE will not conduct heat well. Just as a solid crystal of quartz is a nice heat sink, sand is not. Besides, the crystals only melt to form ICE, they have no exit. So the problem is to expel the 'pack', not prolong the obstruction by trying to 'melt' it? Heating the Stainless steel is a waste of energy.

Some way to expel the slug of compressed particles? compressed air, forward?

A snow cave is great insulation against a bitter exterior, as loma has said. Heat is slow to escape, why would it be quick to enter? Some new approach is needed, it is taking too long to fly without Pitot tubes?

[HazelNuts39]

Thanks RRR;

BTW, .04 kWh per hour amounts to 40 W.

[Machinbird]

You gentlemen are overlooking an important mode of melting the ice/snow inside the probe.
Infrared radiation.
Some initial reading on the subject tells me that we are lining the interior of the probes with the wrong substance. From a Nippon Steel technical report on infrared spectroscopy, this telling observation: http://www.nsc.co.jp/en/tech/report/pdf/n10014.pdf
The emission energies of the glass sheet and PTFE sheet at 200 Celsius
are so high that both materials radiate heat when you draw your
hand near towards them. By contrast, none of the metallic materials
feels hot.I can think of geometries that would promote both modes of melting (conduction and radiation) and which would promote development of open channels through an ice mass.
Seems to me that pitot tube heating design is stuck in the 1930's.

[Machinbird]

OK,
I've had too many cups of coffee today, but another thought occurs.:}

To get more power into a pitot tube quickly, you could couple it up to a waveguide and 'nuke' it the same way we heat water bearing items up in a microwave. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/nerd.gif Those guys designing aircraft pitot tubes really have been stuck in the dark ages. Stick with what grand daddy always used must be their motto.:rolleyes:

[Lyman]

Why Stainless Steel anyway? Delrin, Ceramica, Teflon, etc. Why such a sharp entry? I must be a cup behind, Radar Heating occurred to me as well.

A very thin analogue to the current problem is the Shuttle tiles. A very heat averse medium Isolates heat from the inner surface. It is as if the current design fosters the retention of the snowpack.

[awblain]

I'm not sure powerful IR or microwave heating of the air within the pitot tube is necessarily desirable.

I am reasonably sure that you want to minimize changes to the temperature of the air in the pitot probe as compared with the air next to the static probe.

[Lyman]

Technically, is the 'air' being heated? There is no flow whilst the plug/ice is being expelled, so either a constant current, or a transient one, same as current design? The Steel is maintained at a high heat (Don't Touch!) so would the downside be unmitigable? Dunno. The probe currently requires a fair current, and precise Temp control in flight is not a design consideration, is it? Also, Dunno.

[bubbers44]

Subject: Test Pilot Burt Rutan, on Airbus



Passed on by an experienced guy who worked for Lockheed and then the FAA for years. He absolutely refuses to fly on any Airbus because of their French designed fly by wire system.


Bill, These machines are mfg in Touloius, France and have certification by CAA and ICAO over there before they go for our FAA certification. It depends a lot on direction from the white house and congress as to what the FAA does when it comes to dealing with foreign governments. Some times the FAA doesn't have a whole hell of a lot to say about the end result when pressured by the State Dept on some political issue. I think the FAA core knows all about the Airbus systems that are so radically different than any we have here. The computer nerd systems on the Airbus have caused numerous crashes over many years since their inception but never enough of them at one time to get people up in arms.


Airbus is ALMOST as good as Boeing in hiding the real cause of crashes. I remember about 20 years ago when the A319 was being introduced to India. The pilot thought he had control during a landing BUT the nerds system took over on approach, throttled the engines back to idle, and the bird plopped down in the pine trees and exploded about 1/4 mile from the end of the runway. OF COURSE--Airbus found that it was pilot error since neither he nor the copilot survived. Twenty years later the same nerd systems on a A320 put Capt. Sully in the Hudson. The nerds sensors on the engines determined that the bird strike was cause for shutting down the engines and it shut down both engines and the pilot had no control to restart them. Actually the strike did nothing more than smear some goose guts over an engine PTO probe and their was NO reason to shut down the engines. If this had been a Boeing, Sully could have used the engines to make a safe landing.


The Air France 447 was another nerd screw-up in using JOY sticks to fly a huge airliner--the A330 is a huge bird!!
What makes this incident so sad is that the exact thing happened to an A330 in France five or six years ago during a demo flight by their chief test pilot. The accident was the basic responsiblity of the chief test pilot as he allowed a customer pilot (with very little flight time) to make the take -off to show him how simple it was!! On take-off the customer pilot pulled back too much on the JOY stick, and before the chief could take over, stalled, crashed and burned right in front of the control tower. Just like 447 the chief couldn't see what position the copilot JOY stick was in, as it was covered by his hand, just as the Capt on 447 couldn't see what control inputs were being made when he entered the cockpit at 18,000 feet on the way down to the water. If it had been a Boeing he could have seen the copilot pulling back on the control yoke causing the the stall. And to further the confusion in the cockpit--when the right JOY stick is moved, the left JOY stick doesn't move with it. When one moves either control yoke on a Boeing the other control yoke responds with the same movement--not so with the nerds system!!


Bill,
the only thing we can do at this point is stay the hell off Airbus equipment!!

Jim,
Where’s the FAA in all this ??

[A33Zab]

Read good information and valuable discussion on PPruNe, but also a lot of rubbish......this post is beyond the last category.

[bubbers44]

Somewhere in Europe obviously. I think this ruffles a lot of feathers but Dick Ruttan is a genius with what he has accomplished in aviation and I agree with his comments. Not seeing what your FO is doing on the side stick kept me out of the air bus. That big yoke in front of you tells you when it is time to take over. It rarely happens but sometimes you need to know what the other guy is doing. In the Airbus it is difficult with the side stick from what I have been told. I chose never to fly one.

[Machinbird]

Bubbers, Not up to your usual professional standards to publish something like that "article" of unknown pedigree. :hmm:

For those wondering about the effects of "heating" the air, inside the pitot tube, remember that it should not be trapped if we can keep the tube from getting plugged in the first place, and is always flowing through the tube to the drain ports at a relatively low speed. There is no way to change the pressure in the tube then from heating the gas inside the tube. (I suppose if you got really ridiculous with heating you could start looking at ramjet theory:rolleyes:). The idea is to be able to rapidly apply energy to the internal volume of the pitot tube, and if the thing begins to fill with solid water, to rapidly convert said solid water to a liquid so that it may be purged from the probe vent holes with dispatch. To do this reliably requires sensing systems and a better means of applying energy than is presently being used.

The absorption of either infrared energy or microwave energy by the atmosphere is miniscule unless you then throw in water in some form or other. There are some relatively narrow absorption bands in the infrared spectrum from molecular dynamics.

[bubbers44]

I don't understand the pitot heat and my Dick Ruttan story having anything to do with what we are talking about. He flew around the world non stop and made a world record. He put a man in space without NASA. He has this opinion about Airbus and I agree with him. That is all.

[Lyman]

bubbers

I think you may be confusing the two brothers. Dick flew non-stop around the Globe, Burt launched a human into space w/o the 'help' of NASA.

I don't trust Dick Rutan. Burt? He is the genius. Which one has the HO for Airbus? I have neighbors on either side here in the retirehood. Both flew the Airbus, and both love it. That's all I need to know.

[PJ2]

bubbers44;

Re, "Bill,
the only thing we can do at this point is stay the hell off Airbus equipment!!"

Well, if that's from an aviation professional I don't care what they've done, that's just plain stupid and embarassing. It's prejudice all the way down because the author clearly knows nothing about the Airbus, doesn't want to know but condemns anyway. The stories prove that anything can be twisted to support prejudice if that's all one's agenda is.

You've made it abundantly clear over the years that you don't like, don't trust, and don't know the design. That is sufficient to make your point; there is no cause to re-argue the case each time something comes up regarding the AB discussion. It's boring because it doesn't advance discussion and doesn't contribute to others' knowledge or understanding.

[bubbers44]

OK, that is how I feel about AB. Sorry.

[PJ2]

bubbers44, no problem. My whole point is you don't need to say you're sorry...I'm offering feedback that your views are well and thoroughly understood. I'm not trying to change your mind. I don't need you to "believe in Airbus". But it would be pleasant and interesting to advance discussions on points of understanding, most of which don't involve the Airbus.

If a Rutan or an FAA guy said those things that's really disappointing...I would have expected more comprehension and thought, but there it is and we move on.

[Mr Optimistic]

Bit puzzled about pitot tubes: if these are a worry why not just make them physically bigger. Would take more to block them and the thermal inertia (mass increasing with l cubed, surface area with l squared ) would increase, smoothing temperature changes.

[StainesFS]

As my user name suggests, I am not a pilot, professional or otherwise, and have no axe to grind in the A v B debate except to point out that, if we are to have this debate, the views entailed need to be supported by facts. (I am a scientist by training). The mysterious "Bill" quoted in Bubbers' post uses "facts" which are not supported by the relevant accident reports. In some instances, he is just wrong in his assertions and, in others, he seems to stretch investigator's comments to suit his agenda.

The A319 crash about 20 years ago is, I presume, a reference to Indian Airlines 605 (actually an A320 but that is irrelevant). The report is sparse in detail on the cause of the excessive descent rate, but "Bill" apparently knows more. It mentions pilot error with the flight crew not recognising that the aeroplane was in open descent rather than "approach mode". Much of the criticism of the Airbus philosophy at the time came from the French pilots' union who were unhappy about the loss of the FE in the two person flight deck. This philosophy has, of course, long since been adopted by Boeing also.

The A330 test flight accident was attributed to several causes not just the excessive pulling back on the side stick by the FO. He, incidentally. was not a customer (although Alitalia personnel were on board but not as crew) but as an Air Inter pilot on attachment to the Airbus training arm.

"Bill" seems to think that the engines on the A320 involved in the Hudson ditching were basically intact and were shut down due to, in effect, a computer reacting to a damaged sensor. However a cursory reading of the FAA investigation report reveals details of much more severe physical damage to both engines resulting from impact by particularly large birds. In the interest of balance, the report did state that the successful ditching was due, in part, to the Airbus FBW system.

My own view is that unless or until accident statistics show a significant difference between A and B (one way or another) in accident rates then it becomes a matter of personal pilot preference, which is their right. At the moment, I do not believe that the statistics show any such difference. In the context of a complex investigation into a tragic incident, such views as are declared by "Bill" should be ignored as not being fact-based. They might possibly be seen as part of the continuing propaganda war (conducted by both sides) between A and B in the furtherence of sales. Nothing wrong with that but in its rightful context.

[PJ2]

StainesFS;

Re, "...if we are to have this debate, the views entailed need to be supported by facts."

Not to beat a really dead horse, but yes, that was the point I was also trying to make, thanks.

I know these accidents; none of these accidents occurred in the way "Bill" described, so it is just more of the same boring A vs. B propaganda. I'm surprised that the Habsheim accident wasn't trotted out again.

Apropos your comments regarding statistics you will appreciate the meaning behind the following, from Boeing. Compare equivalent A vs. B types in the numbers:

Statistical Summary of Commercial Jet Airplane Accidents, Worldwide, 1959 - 2010. (http://www.boeing.com/news/techissues/pdf/statsum.pdf)

What such populist myths such as those posted above perpetuate and even legitimize is an institutionalized lack of understanding of what really happened in these accidents. That is not how flight safety and investigative work is done nor is it how training and learning from others in this business is done. "Bill", who remains unidentified and mysterious, should come to PPrUne and join this thread to defend his views and perhaps learn a bit himself. There are some here who critique the airplane thoroughly but they know it and fly it. Vive le débat!

Perhaps also of some interest may be Psychologist Daniel Kahneman's book, Thinking, Fast and Slow (http://www.businessweek.com/magazine/book-review-thinking-fast-and-slow-by-daniel-kahneman-10272011.html) which in part discusses how we make up our beliefs, assess/decide upon risk using intuitive and/or rational thought. Last November Vanity Fair ran an article which may be of indirect interest to some: The Quiz Daniel Kahneman Wants You to Fail (http://www.vanityfair.com/business/features/2011/12/kahneman-quiz-201112)

PJ2

[HazelNuts39]

These machines are mfg in Touloius, France and have certification by CAA and ICAO over there before they go for our FAA certification.Neither CAA nor ICAO have any involvement in the certification of Airbus products.

[Algy]

Indian Airlines accident analysis in Flight International. (http://www.flightglobal.com/pdfarchive/view/1990/1990%20-%201248.html)

[PJ2]

Algy;

Thanks for the link. I think the accident is relevant to the present discussion in the sense that taking over manually and flying the airplane was then and remains today a prime, professional requirement.

If a pilot can't do that with his or her airplane, that is a serious training and standards matter. The A330 (and all the rest) are eminently, easily flyable in manual flight. It wasn't an emergency and the "safe conduct of flight" was not at risk.

The problems only occur when one out-thinks the design and that is again an understanding/training matter, not an automation matter.

The Bangalore accident was not an "automation" accident though mode confusion contributed. All that was necessary was to push the thrust levers fully forward and actually fly the airplane which is their job. All that was necessary in the AF447 accident was to maintain pitch and power settings. The airplane was fine moments before the loss of airspeed indication, and such loss means nothing to the actual airplane itself...it was still flying, still had power and was in stable flight.

The "Idle, Open Descent" issue here was fixed twenty years ago. I used to teach it and the "mode reversion" process during line-indoc training on the A320.

PJ2

[RR_NDB]

Hi,

PJ2

The airplane was fine moments before the loss of airspeed indication, and such loss means nothing to the actual airplane itself...

Means nothing? Sir, respectfully i disagree; here is (the beginning of) WHY:

With the Synergy of a highly motivated group we can touch some "sensitives points" in our effort to understand what occurred with F-GZCP that night.

The diversity of the posts show the agenda of the posters is diversified. I think the more constructive one is to allow us to be prepared to avoid problems when dealing with similar equipment.

This can be important not just to pilots.

A Feedback System is EXACTLY what his name implies:

Something that receives "feed" back (to itself).

Tacoma narrows bridge (http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)) received energy (from wind turbulence), OSCILLATED to the structural limits and was destroyed.

This was a typical POSITIVE feedback (the one that presents GROWING oscillations)

Positive feedback can be dangerous. But when controlled (by lossy components) are very useful and common in our lives.

Example: HF radio equipment used during Titanic accident. (A coiled wire, a capacitor, a switch, a spark gap and an antenna and a power source)

Another positive Feedback System: An A/C subject to an UNDAMPED oscillation when PF apply larger inputs (larger than a given threshold). This may led to the destruction of the equipment. The loss of the F4 posted by Machinbird perhaps is a good example.

During some initial discussion on the (clearly obsolete) AS probes still today used by the aviation industry we had the opportunity to understand the advantage to have a better one using a closed loop. The feedback WOULD REDUCE the time required to the Pitot to "recover" from the "cold" it frequently suffer. :) In the 30+ cases of UAS they briefly (seconds) failed to work properly.

In F-GZCP last flight the System (A/C + crew) received an "input" (heard in CVR) so important that affected the stability of the System.

The ice crystals WERE NOT ADEQUATELY PROCESSED BY AN IMPORTANT SENSOR (so important is MULTIPLE) that as per A33Zab diagram has not a TEMPERATURE CONTROL. It seems (the heater) "less intelligent" than the appliance we use to press our clothes. The pressing iron has a thermostat, i.e. a feedback system to control it's temperature.

This kind of NEGATIVE FEEDBACK improves the operation of the equipment and allows a high quality work. Our clothes are preserved, the pressing iron can operate IN THE BEST range, etc.

Another example of a feedback system is the yaw damper. "With the help" of the rudder the A/C has the directional stability greatly improved.

At that night the System (A/C) put the crew (PF) in the "feedback loop". The pilot had to act immediately. Doing so he corrected the roll. A roll we may understand started by LARGE AMPLITUDE STIMULI from the environment. A harsh one they had to do a "last minute" deviation. PF started to apply LARGE AMPLITUDE stimuli to the new System (A/C + PF) and this could led to UNSTABILITY.Machinbird and others suspect of PIO (roll) after this PF action.

Up to this point the System received 'inputs" in some degree affecting the Stability of the entire System (System+PF):

1) Ice crystals.
2) Loss of important feedback loops: A/P and A/THR
3) Turbulence
4) Large PF inputs

This facts generated almost immediately 10 other facts:

1) System was automatically reconfigured (NL to ALTN)
2) System degraded (to "another" A/C with less available resources)
3) ISIS "suffered"
4) A/C broadcasted anomalies (ACARS)
5) Crew not was informed on reason of A/P and A/THR quit
6) Turbulence became POTENTIALLY more relevant
7) HF "surfaced" (by lack of training, etc.)
8) Not use of SOPs and adequate CRM
9) Lack of understanding ("uncharted waters") by PF AND PNF
10) A persistent climb with high rate

Clearly after this facts the System was less robust than before.

A safe (and stable) System MUST BE:

FAULT TOLERANT

And show:

GRACEFUL DEGRADATION.

And i will add:

A safe System must show RESILIENCE (System + crew). The transient (perhaps up to the apogee) dominated the scene. And After "inflexion point" put the plane in a "steady state" condition lasting roughly 4 minutes falling (and circling) at near terminal speed.

For me it is clear the System at this moment (PF starting to act IN THE NEW LOOP) was showing less capability to "resist" to the initial "input" and subsequent consequences: tiny ice crystals.

(to be continued in part B)


In the meantime we must think looking to the factual information we have so far.

PS

Questions to think and take into account in our analysis:

The man machine interface became essential at this critical moments?

We will know what PF saw? (RH was not recorded and ISIS also had "impairment")



Some remarks related to AS probes: Open loop (no feedback): LONGER RECOVERY TIME (to recover from the "cold")


A33Zab

Thanks for the diagram. Amazingly the probes are just heated and their temperature is not controlled*. This fact alone may explain part of the observed problems related to air speed measurement.

As Machinbird pointed there is room for improvement. With a closed loop temperature control the time to reheat the critical internal regions of the probe would be reduced.

Anyway i am deeply surprised (negatively) with the approach used. Sensors capable to "disable" important functions of the A/C more simple than the necessary.

Much of my rationale in some posts were based in a better (closed loop) approach. when in AUTO mode. In both AUTO and ON (what i called MANUAL) the power applied IS THE SAME.

(*) And we really don't know if a ballast wire is used.

Bottom line:

The thermal "recovery" of probes takes too long (in ~20 seconds after hitting ice crystals A/P and A/THR quit). The recovery time WAS NOT COMPATIBLE with System requirements of GIGO.

The recovery time MUST BE REDUCED and i'm sure can be reduced.

The different probe characteristics of FR (now obsolete) and US (with limitations) may be explained by thermal inertia plus the factors mentioned by Owain Glyndwr

Also the materials used certainly are important like mentioned by Lyman

Up to this point (in this sensitive issue and related posts) thanks for comments/questions from: HN39, PJ2, Lyman, roulishollandais, and contributions from Machinbird, A33Zab, Owain Glyndwr and others including PM channels.

I will try to comment and answer questions made before, when possible. (asap)

[RR_NDB]

Hi,

Mr Optimistic,

When i understood the heating approach used in the TRIPLE sensors (failing near SIMULTANEOUSLY), i tend to be,

Pessimistic,

:}

[Owain Glyndwr]

The airplane was fine moments before the loss of airspeed indication, and such loss means nothing to the actual airplane itself...

I agree with PJ2 - anyone who has flown even model airplanes can tell you that a stable aircraft does not need airspeed information to continue safe flight,

All the evidence from other similar incidents is that doing nothing was a viable (and arguably the best) option. Even in alternate law the aircraft is pitch stable - the system does not use, or need, airspeed information to achieve this. This law is in fact 'graceful degradation'. Freezing the throttles also maintains the equilibrium state.

The system was never given the opportunity to show stability in roll as it was continually perturbed by pilot input. Incidentally there was no PIO - the roll oscillations are damped not divergent and the motions and stick movements are not out of phase. What we are seeing there is a pilot struggling to come to terms with a new set of unfamiliar dynamics. He got the hang of it in about 30 secs which is not a shabby performance by any standard.

As for the probes, it it clear that the amount of heat being applied was not enough to handle the rate of ice accumulation, which is a random variable. [The proposed new icing requirements show that ice concentration can be greater over short distances than long. The heating rate would have been set up to cover conditions which were less onerous than those possible. Now that a higher limit of ice particle concentration has been identified it should be simple enough to up the heating rate to cope. no need for fancy feedback systems - KISS is still a good principle]

[RR_NDB]

Hi,

Machinbird

Those guys designing aircraft pitot tubes really have been stuck in the dark ages. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-3.html#post7063794)

Henri Pitot would not like his name being associated to dark ages. :}

Now on i will change from SUBHEATED AS PROBES to

OBSOLETE sensors,

(controlling SOPHISTICATED Systems)

PS

The pressing iron i carry in my motor home has a thermostat. :}

The ones i have in my house are SUPER ADVANCED.

PS2

Seems to me that pitot tube heating design is stuck in the 1930's.

1930?

When i visited the Gold mine museum in Joburg i did see ADVANCED devices. And the mine operated well before that year.

[RR_NDB]

Hi,

Owain Glyndwr,

anyone who has flown even model airplanes can tell you that a stable aircraft does not need airspeed information to continue safe flight

Sure! :ok:

All the evidence from other similar incidents is that doing nothing was a viable (and arguably the best) option.

As a researcher i would prefer to deliver to pilots a better System than one that you need to "wait and see" every time. Wait and see (some kind of hysteresis) is wise, for sure.

In this case the brief failure of obsolete sensors (sub heated, high thermal inertia, etc.) contributed to a chain of events.

This law is in fact 'graceful degradation'

I am not talking about this law. I am talking about the System (A/C + PF) during the transient. And i not mentioned yet the man machine interface.

The system was never given the opportunity to show stability in roll as it was continually perturbed by pilot input.


A fact.

What we are seeing there is a pilot struggling to come to terms with a new set of unfamiliar dynamics

Struggling to understand by hand "testing the plane"? :{

As for the probes, it it clear that the amount of heat being applied was not enough to handle the rate of ice accumulation, which is a random variable.

To control the (important) probe temperature is VERY EASY, RELIABLE and K.I.S.S. TO THE EXTREME. Einstein commented about how K.i.S.S. you can go. There are limits.

it should be simple enough to up the heating rate to cope.

This was my first feeling: SUB HEATED.

no need for fancy feedback systems

Still k.I.S.S.

KISS is still a good principle]

And will be forever. Leonardo da Vinci stated: Simplicity is the ultimate sophistication.

But this is to be covered when commenting on the man machine interface.:E

[RR_NDB]

Hi,

PJ2,

The airplane was fine moments before the loss of airspeed indication

Actually before encountering ice crystal the A/C was working fine, i agree.

After increase of CVR noise and fit with OBSOLETE FR probes we may say she was no longer fine.

The clogging started and eventually affected the Stability of the System.

The bureaucracy (and other factors) was allowing the operation of hundreds of flights with obsolete sensors.

And the pilots being instructed to use "State of the art" band aids. *

I would prefer "State of the art" Systems.

:mad:

PS

With insufficient crew training (lack of) for the worst case scenario.

(*) I like duct tape, swiss army knife, band aid, and all this emergency stuff.

But i love a good design. When possible, why not to have it?

[PJ2]

RR_NDB;

Thank you for your responses.

[RR_NDB]

Hi,

Owain Glyndwr

He got the hang of it in about 30 secs which is not a shabby performance by any standard.

Why? What led him to do that? No reasons?

PF was operating as "part of the feedback loop". He acted doing the opposite. What he received from the System?

He acted without any influence from the System? Doing exactly the contrary?

:suspect:

[jcjeant]

Hi,

Owain Glyndwr
Now that a higher limit of ice particle concentration has been identified it should be simpleI agree .. and I want to add (for be intellectually honest) that this phenomena was identified years before the AF447 accident ... and it WAS simple ... blah .. blah ...

[Turbine D]

Hi All,

I am not a pilot but an engineer. I find the pitot discussion very interesting. There have been many suggestions on how to make this speed detection devise better as it appeared to be the first thing to fail in terms of proper operation in the AF447 flight. I am going to confine my thought only to the pitot itself, not the system of the aircraft to which it is connected that interprets and responds to the signals from the pitot tube or multiple tubes.

In designing a devise of any sort, the design engineer has to know as much about the parameters the devise is going to experience and operate within. Given this information, he/she can then go about designing the devise based on this information and perhaps a data base built on prior experience. Once the devise is designed and manufactured it is then tested to parameters across the envelope it will experience in operation. If these tests are successful, then it can be placed in service with some degree of confidence that it will perform the intended function it was intended to perform. So what could go wrong? What could go wrong with a pitot tube where the basic physics and general design has been known dating back to the late 1700s? And why is it that one manufacturer's design seemingly has less problems than another manufacturer's product when both met mandatory testing and certification requirements? Why is it that when the devise is used on one aircraft, it is more susceptible to non-performance than on another aircraft?

I would postulate to you all, there is nothing wrong with the basic concept of the current day pitot tubes, they will and can work successfully across the total flight envelope without any new bells and whistles. The reason they may not is because the parameters used in the design and testing did not and for that matter, do not match what is experienced across the total operating envelope, particularly at high altitudes and high speed in icing conditions. I have thought about this for some time and wondered in the instance of Airbus aircraft, could there be a difference in pitot tube performance verses that of Boeing aircraft? Could it have something to do with installation or location or shape of the fuselage forward of the mounting point or how the air passes into it or the actual testing and certification requirements? Was Boeing lucky and Airbus unlucky?

I think it has a lot to do with everything mentioned above and some other thing not thought of. Here is some interesting information that has been developed out of the studies resulting from AF447 and commented on by Airbus regarding changes to testing and certification:

Icing Conditions

The certification icing requirements defined in CS 25 Appendix C include liquid water contents, temperatures and droplet diameters in excess of those specified in the TSO. In addition the AMC to CS 25.1419 defines mixed phase and ice crystal conditions. Whilst it is recognized that the TSO tests are not intended as a means of compliance for the certification regulations Airbus believes the ETSO should include icing conditions that are more comprehensive than those defined in the TSO.

There would appear to be little benefit in designing and testing a probe to the TSO requirements if it is necessary to repeat the tests to more conservative conditions to support the aircraft certification.
Pitot and pitot static probes are known to be sensitive to ice crystal and mixed phase conditions and therefore Airbus always tests its probes in these conditions. The AMCs to CS 25.1323 and 25.1325 states:

“Airspeed Indicating System
1 Tests should be conducted to the same standard as recommended for turbine engine air intakes (see AMC 25.1093(b)(1)) unless it can be shown that the items are so designed and located as not to be susceptible to icing conditions. Ice crystal and mixed ice and water cloud will need to be considered where the system is likely to be susceptible to such conditions.
2 However, in conducting these tests due regard should be given to the presence of the aeroplane and its effect on the local concentration of the cloud”

In addition the AMC to CS 25.1419 paragraph 4 states that an assessment of the vulnerability of pitot heads to ice crystal conditions must be made. Conversely TSO C16a does not require tests to be performed in mixed phase or ice crystal conditions. In Airbus view such an omission is contrary to the objective of setting a minimum level of performance particularly as most aircraft fly in such conditions. Furthermore a probe designed and tested in liquid icing conditions only may require a significant redesign to meet the ice crystal and mixed phase requirements.
It should be noted that recent evidence indicates that the ice crystal and mixed phase conditions defined in AMC 25.1419 may not be adequate for pitot and pitot-static probes.

Airbus' comments go on to observe:

Probe Installation Effects

The TSO requires probes to be tested to the liquid water icing requirements of BS2G135 amendment 1 to asses anti-icing performance and modified ISO 8006 icing conditions for de-icing performance.
Test N°2 specifies Max intermittent icing conditions that are considered below JAR25/CS-25 Appendix C requirements. Accounting for installation effects on A330/A340, local LWC at –30°C should be 1.5g/m3 for maximum intermittent icing (without safety factors). The TSO C16A recommendation is 1.25g/m3, which therefore does not cover installation effect on Airbus A330/A340.

These conditions are free-stream conditions and do not consider the effect of the potential installation effects. Depending on the probe design and aircraft installation these installation effects can lead to the Liquid Water Content (LWC) at the probe location several times greater than the free-stream conditions. The TSO should at least highlight the potential installation affects to applicants.

The TSO requires probes to be tested at 0° angle of attack only whereas angles of attack up to 15° are not uncommon in service. Airbus believes that tests at angles of attack up to at least 15° should be included in the ETSO.

And,

Scaling of Icing Conditions During Icing Tunnel Testing

During recent icing tunnel testing it was found that the electrical current drawn by air data probe heaters varied with the mach number of the airstream such that at lower mach numbers the probe current reduced due to a change in the heater element resistance. This effect needs to be considered when scaling icing conditions as for some heater designs increasing the LWC to offset lower attainable icing tunnel speeds and vice versa may not be representative. Airbus recommends that the ETSO highlights this phenomenon.

So I think with proper design parameters, proper mating with the aircraft and proper testing requirements pitot probes from any manufacturer can be designed that work throughout the flight envelope. We are not there yet in full understanding, but it is not hard to imagine the icing problems can and will be solved very soon.

[RR_NDB]

Hi,

PJ2,

The Synergy and motivation we can exercise here with you and other aces is great.

We must use when possible the opportunities to explore new ways to look to the issues.

The concepts and ideas i present are conceived carefully and based on memorable experiences since 1968 when i first was introduced to birds of all sizes (and it's anatomy) in a "War Surplus like" shop. i was student of Electronics avid to understand "everything". I had the opportunity to learn the basics in several areas at this time. Later on i had the privilege to fly some venerable birds like the C47 and ride in C46, Connie, etc. etc. etc.

My motivation in PPRuNe is through a minimum of understanding ultimately, try to contribute to our safety. My 3rd son is a professional pilot and may be can learn something reading our effort. :)

[RR_NDB]

Hi,

Turbine D,

We are not there yet in full understanding, but it is not hard to imagine the icing problems can and will be solved very soon. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-4.html#post7066003)

I think so.

PS

Did you hear about a patent filed by Airbus SAS using L(alpha)ser?

(i write Lima Alpha Sierra echo Romeo and the final result is Lima @ Sierra Echo Romeo)

Anyone could explain this glitch? :*:mad:

[Turbine D]

Hi RR_NDB,

I can't explain the glitch but, I did see that Airbus file for the patent. I also think there will be some changes in the A-320neo to address the pitot icing situation and maybe in the A-350 given enough time. I don't think the technology will be radically different but will be an attempt to incorporate what they have learned since AF447.

[Machinbird]

Sometimes you need a new approach when you understand the real problem.

It find it very significant that 19 seconds of exposure to the ice crystals/pellets was sufficient to shut down the 3 airspeed sensors. The fact that a loaded up pitot tube can begin to clear itself in 30+ seconds after the blockage is not really good news.

While blocked, a pitot essentially stops collecting new ice inside, so it would appear that what takes 19 seconds to collect requires up to 49 seconds or more inside a pitot tube to begin to melt and clear. This tells me that the pitot heating system is seriously outmatched by the environment.

I think, as some of the posters earlier have mentioned, that the key problem is coupling the melting energy to the collected ice. Conduction alone just cannot do the job and maintain an open pitot tube-at least, not at realistic pitot tube temperatures.. Settling for intermittent blockages is not really an acceptable course. What is needed is a better means of coupling energy to the ice when it is collected and a wider dynamic range of energy modulation.

During recent icing tunnel testing it was found that the electrical current drawn by air data probe heaters varied with the mach number of the airstream such that at lower mach numbers the probe current reduced due to a change in the heater element resistance. This is very good corroboration that the pitot heaters behaved like ballast resistors.

I would like to offer the thought that using pitot tubes with different means of heating begins to create diversity in the airspeed sensing system sources. Dinking around with more of the same (higher wattage) in pitot heaters is likely to be unsuccessful and will likely retain the cyclic clearing/clogging characteristic under worst case mixed ice conditions. Sometimes KISS is an inappropriate solution if it involves undesirable adverse characteristics. Time to move on.

At least that is how I analyze this.:(

[jcjeant]

Hi,
Turbine D
I am not a pilot but an engineer. I find the pitot discussion very interesting. There have been many suggestions on how to make this speed detection devise better as it appeared to be the first thing to fail in terms of proper operation in the AF447 flightAre you sure the pitot tube failed ?
When I read the BEA report N°3 it's indicated that the plane was working as per design
The pitot tube worked also as per design
The plane and all parts of it were certified to work under certain limits
The accident of the AF447 show that the plane was put (or go .. make your choice) over the limits of certifications (and he stalled) .. as was the pitot tube (and he iced)
So the plane and the pitot tube never failed .. as .. when the pitot tube returned under the certification limits he worked fine again (nobody go outside the plane for fix it .. as he never failed)
Unfortunately the plane required some extra actions for return in the certification limits ... and those actions were no performed ...
Finally .. who failed ?

[MagnusP]

Not a glitch. Just if you write the proper acronym for the coherent light device, ads appear selling the devices to any scrote who fancies trying to blind a pilot on approach.

[Owain Glyndwr]

Turbine D

I am not a pilot but an engineer. Me too, and I find myself in complete agreement with what you say.

In designing a devise of any sort, the design engineer has to know as much about the parameters the devise is going to experience and operate within. Yep!
What could go wrong with a pitot tube where the basic physics and general design has been known dating back to the late 1700s? And why is it that one manufacturer's design seemingly has less problems than another manufacturer's product when both met mandatory testing and certification requirements? Why is it that when the devise is used on one aircraft, it is more susceptible to non-performance than on another aircraft? Or that one manufacturer’s product will work, but another’s won’t, both at the same location on the same aircraft? Or that the one that didn’t work was OK for seven years?

I would postulate to you all, there is nothing wrong with the basic concept of the current day pitot tubes, they will and can work successfully across the total flight envelope without any new bells and whistles. I completely agree!
The reason they may not is because the parameters used in the design and testing did not and for that matter, do not match what is experienced across the total operating envelope, particularly at high altitudes and high speed in icing conditions. Again I agree completely
I have thought about this for some time and wondered in the instance of Airbus aircraft, could there be a difference in pitot tube performance verses that of Boeing aircraft? Could it have something to do with installation or location or shape of the fuselage forward of the mounting point or how the air passes into it or the actual testing and certification requirements? Was Boeing lucky and Airbus unlucky? I have wondered about that also, and it is interesting that Airbus themselves, when commenting on the proposed TSO, say:

These conditions are free-stream conditions and do not consider the effect of the potential installation effects. Depending on the probe design and aircraft installation these installation effects can lead to the Liquid Water Content (LWC) at the probe location several times greater than the free-stream conditions. The TSO should at least highlight the potential installation affects to applicants And
Furthermore a probe designed and tested in liquid icing conditions only may require a significant redesign to meet the ice crystal and mixed phase requirements.
It should be noted that recent evidence indicates that the ice crystal and mixed phase conditions defined in AMC 25.1419 may not be adequate for pitot and pitot-static probes Max intermittent icing conditions that are considered below JAR25/CS-25 Appendix C requirements. Accounting for installation effects on A330/A340, local LWC at –30°C should be 1.5g/m3 for maximum intermittent icing (without safety factors). The TSO C16A recommendation is 1.25g/m3, which therefore does not cover installation effect on Airbus A330/A340.

But the newly proposed Appendix P to CS25 gives the TWC at -30oC to be 4.5 g/m3 BEFORE any installation effects are included. So the requirements against which the A330 was designed are miles too low against the possible ice particle exposures now envisaged.

[I should have added that Airbus say they test to their own internal requirements that exceed the JAR 25 variety, so we don't really know what theA330 probe capability was]

Worth noting also that the research and analysis work that led to this conclusion was not started until 1998, four years after the A330 went into service.
So I think with proper design parameters, proper mating with the aircraft and proper testing requirements pitot probes from any manufacturer can be designed that work throughout the flight envelope.
I agree with you there, with one proviso, and that is there has to be a suitable facility for testing the probes.



In AIAA 2006-206 they point out that:


Once the atmospheric threat is known, the next challenge to the industry is to develop test methods that properly simulate the engine operation at high altitude in this environment. Icing wind tunnels and icing test facilities available to the industry nowadays are mainly designed to simulate supercooled liquid droplets depicted in the FAR Part 25 Appendix C icing envelope23. These droplets are produced by nozzles spraying water initially at above freezing temperature into the cold working air stream of the test facility, and targeting the same particle size range as in the natural cloud conditions. The droplets lose temperature as they travel down the cold air stream, and in most cases achieve a supercooled state before they reach the test article. The spray particles are generally spherical in shape as they would be in a natural supercooled cloud. Ice particles, on the other hand, occur naturally in many different shapes and they generally span a much larger range of sizes than the supercooled droplets depicted Appendix C envelope
We are not there yet in full understanding, but it is not hard to imagine the icing problems can and will be solved very soon.

Let us hope so

[fizz57]

RR_NDB,
While your focus on the pitots as the initiating cause of the AF447 disaster is understandable, it is really irrelevant in the wider picture. Improving the pitots is necessary in the general drive for safer flying, but not as a specific outcome of this accident.

Sensors can fail for a million reasons. CB's trip, autopilots drop out, likewise. The aircraft should be flyable in this case with the proper backup systems/crew procedures. Surprise surprise, it is!

Ice was the issue in this case, but may not be in another. Your brand of hindsight may have saved AF447, but will not save the next one. The issue here is not the pitot icing, but the subsequent mismanagement of the problem, whether by the crew or the remaining aircraft systems (the stall-warning cutout comes to mind).

[paull]

1> I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?
2> Has anyone looked at (ACARS?) data to see whether
a> Icing is rare but when it happens all sensors will ice ; or
b> Icing is fairly common but the sensor offer effective redundancy and it is rare to lose two.
I think someone mentioned before that HAL can clearly ‘see this coming’, and it would not seem impossible to add some logic along the lines of;
“Hey guys, I have just had to arbitrate a whole series of mismatched speed indications, it is becoming increasingly difficult to pick the right one with any degree of certainty so any time soon I might be handing you the plane”.

[Clandestino]

So I think with proper design parameters, proper mating with the aircraft and proper testing requirements pitot probes from any manufacturer can be designed that work throughout the flight envelope.

But i love a good design. When possible, why not to have it?

Sorry to say chaps, but such a faith in our ability to totally comprehend the atmosphere and design solution to every problem it throws at us is excessively optimistic.

Icing conditions that AF447 encountered a couple of minutes before its destruction are very rare and seldom cause trouble. Being elusive, we can't analyze them as much as we would want. All we know about them that they usually occur near "deep convections" and unlike every other known type of icing, they need the surface they hit to be heated or they won't stick, so they clog heated probes and engine compressors. I am exaggerating here but if we approach the problem narrow-mindedly, there is obvious design solution: cut heat to probes as they pick-up ice. That would make probes resilient to exotic high level ice crystals but would make them more vulnerable to every other icing condition there is and that's a lot of problems created for just one particular solved. In real world, there are no designs without downsides and designing solution for problem one doesn't even know what it is can be successful by pure chance.

Order for replacement of Thales probes was based just on empirical evidence (which is more than enough when dealing with high hazard activities such as aviation) that they are ten times more susceptible to getting blocked by high level ice crystals than rival ones. We have no idea what is in the design of probe or complete installation that makes Goodrich probe ten times less likely to get blocked than Thales but we can be sure that different performance was completely unintended. Also Goodrich probes are not completely immune and we better make sure the pilots know what to do when they lose airspeed information, like keep on flying regardless.

I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?Probably not. 30something crews got it right in the real life even without resorting to prescribed procedures. Some of them were AF.

[Lyman]

It is remarkable that aviation culture will wax hysterical only to be followed by a rapid version of "Nothing here, let's move along."

When a passenger packed 777 lands short of the runway with fuel starved engines (starved, not exhausted), we end up with an urban myth of "mysterious fuel characteristics", and a band aid sheet metal workaround.

Here, it seems, we are on the cusp of similar dismissal of anomalous circumstances.

Whistling in the cemetery? "We are going to crash...It cannot be." "Odd Pitots" and crap pilots? Keep whistling.

"It cannot be..."

Oh, yes it can. Merely unusual Pitot behaviour? Definitely. If one believes in real red herrings, and not virtual.

[PJ2]

paull;

Re, "1> I know that prior to AF447 the pitot-icing had already been identified and there were steps in place to change the sensors, but was any action taken to introduce this scenario into sim. flights so that we could assess what proportion of pilots would get it right?"

Yes, such training was planned and done as part of AFs recurrent briefings and simulator training curriculae for 2008/2009.

The BEA Second Interim Report, Section 1.17 Information on Organisations and Management, provides specific information on this and the previous section, 1.16 Tests and Research discusses the thirteen previous UAS events which had sufficient data such that adequate studies could be undertaken of the phenomenon.

Oddly, of the 36 UAS Events listed in Appendix 7 of this Report which occurred to the A330 up to the day of the accident and during the recurrent training period, only two were not in cruise* yet the UAS script was for the right-after-takeoff phase which of course is the most critical phase of flight.

The briefing notes for the exercise indicate that if the ADRs are not rejected and the FCPCs and FCSCs continue to use the incorrect information, the crew will have to:

" Trigger the emergency manoeuvre(15) if they consider control of the flight
is dangerously affected (initial climb, go-around, etc.);

" Trigger the Flight QRH procedure with UAS / ADR check if the trajectory
has been stabilised and flight is under control." **

*one event was on descent (FL290) and the other event was on approach.
** p54, BEA Second Interim Report, English version

[Lyman]

PJ2

A quick question. You refer to "UAS" procedures in the literature from Airbus. I may be mistaken, but I believe the term "UAS" was coined here at PPRUNE, post AF447. Prior, the nomenclature was not specific, generally referencing other than "Unreliable Air Speed" (UAS). ??

[PJ2]

Lyman;

The term "UAS" was used in the BEA Second Interim Report but not the first. In researching the eight or so AF447 threads the term was used first by Will Fraser on the 23rd of September 2009 and thence by bearfoil on the 24th of December, same year. Whether the BEA adopted the abbreviation or not can't be known. I know some from the BEA have monitored the threads in the past.

The evolution of the UAS drill and QRH checklist is discussed in the BEA Reports. I first saw it around 1998 and it showed up in the FCTM around 2003/05. At that time it was clarified when to apply the memorized items and when to not do the memorized items and go straight to the QRH procedures which prescribed setting pitch and power according to the QRH tables. Typically such circumstances were cruise flight; the memorized items were intended for low-level, during/after-takeoff circumstances where immediate information was required due to the immediate high risk to the flight, (as per Birgenair & Aeroperu accidents). The aircraft is not in immediate danger with a loss of airspeed information in cruise.

[Hamburt Spinkleman]

Unreliable airspeed has been called unreliable airspeed for many years. It is not a new term, neither is the abbreviation.

I recall checklists called "unreliable airspeed" from at least the early 90's, possibly the late 80's, and expanded checklists and explanatory material with the heading "speed control with unreliable airspeed".

The expanded checklists and explanatory material were more detailed in the A300 days than for later models, particularly concerning the various failure modes and effect on indications and systems.

[Lyman]

PJ2, Hamburt Spinkleman.

Thank you both for your input. The reason I suggest that "UAS" is a "new" acronym has to do not with aviating, but with marketing. At the time, in 2009, it occurred to me that "Unreliable" is not a term to be found on any documents emanating from the community, manufacturer, Line, Pilot's, etc. Not only does it conjure up "risk", it could be conflated to mean, erm...."Unreiiable". It could also have a negative effect in "product liability".

So Hamburt, I am curious if you have copies of these "checklists from years ago".

The reason I coined the term was its self-explanatory nature, and its 'honesty' in an industry that can at times be over obsessed with "marketing".

I meant it without malice, but was attracted to its inception merely because it was....descriptive.

me

Especially at low level, PJ2, would it not also be important to include "Point" after Pitch/Power? Heading after T/O could be construed as important as the first two, CFIT?

[PJ2]

A history of the Unreliable Airspeed drill and checklist can be found in the BEA Interim Reports.

[Turbine D]

PJ2, Lyman, Hambert Sprinkleman,

I did a little research on UAS and came up with some interesting results. It would appear the accident investigation and reporting agencies tend to use the term "Erroneous Airspeed Indications". This is true in the Aeroperu and Birgenair reports as well as one issued by the US NTSB on an incident over Kansas City involving a B-717 which did not crash. These reports were issued prior to or around the time of AF447.

However, there is an FAA document that was issued to discuss this phenomenon:

Date: 6/26/75
Initiated By: AFS-223
AC No.: 91- 43


Subject: UNRELIABLE AIRSPEED INDICATIONS

I would say, in terms of the English language, errorneous airspeed meaning is pretty clear, the airspeed was wrong. Unreliable airspeed is a little "softer" as its meaning is "don't count on it to be accurate or uncertain of accuracy".

Lyman, In a court of law, I suspect the terminology of either poses a problem for the defendant.

[llagonne66]

As QRH section 2.21 is titled "UNRELIABLE SPEED INDICATION/ADR CHECK PROCEDURE", it looks like the "air" has been added at some point of time to the "speed".

But does it change something to the AF447 story (except adding almost one page to this thread:}) ?

[oldchina]

1.17.4.3 Terminologie du constructeur (AIRBUS)
Memory item the following procedures are to be applied without referring to paper: immediate actions of UNRELIABLE SPEED INDICATION/ADR CHECK PROC

"Air France a traduit le titre de cette procédure par « Vol avec IAS douteuse »."

[Hamburt Spinkleman]

Like llagonne66, I don't know what the point is, but.

"Unreliable Air Speed" is the term Airbus has been using for decades in Flight Manuals, FCOM's, QRH's and other material.

Boeing, by the way, use the same term. Or actually they use both "Airspeed Unreliable" and "Unreliable Airspeed".

[Lyman]

Hamburt Spinkleman

The point is a small one. I got tired of writing out the various phrases used to identify a problem that was getting much attention. In creating (?) the acronym, UAS, I found a way to simplify and shorten the nomenclature. If it was used before, fine, but I believe the industry was calling the problem different names, and spelling them out, as if it was this ill-defined, and rare anomaly. I thought it deserved its own acronym. That BEA started to use it also meant I may have been correct in codifying it. It also meant that BEA might have been reading PPRuNe, which means PPRuNe has some standing in the discussion/investigation. So Hamburt, it means whatever it means to you, nothing more. At all.

[Hamburt Spinkleman]

If it is a matter of credit and accolades then it appears those should go to a Will Fraser. See PJ2's post #86.

But even he is some 30+ years too late.

[Lyman]

Will Fraser c'est "Nom d'Aero". Nom de Plume.

The acronym, "UAS", not the text. Let's drop it.

[A33Zab]

Heater is 2 elements of resistance wire, ~34 Ohm @ 20°C.
Uses full 115VACrms wave in flight and half wave (~81Vac) on ground.

PHC warnings levels <0.9A and >6A in flight; <0.4A and >4A on ground.

http://i474.photobucket.com/albums/rr101/Zab999/Pt_tubeHtr.jpg

[HazelNuts39]

Similar idea posted here (http://www.pprune.org/tech-log/466259-af447-final-crew-conversation-thread-no-1-a-60.html#post6981095).

[KBPsen]

I think you will find that Claudette is a bot of some sort, roaming the forums reposting snippets of previous posts.

There have been a few of them recently.

[Lyman]

KBPsen

Quite. "She" happened to land just ahead of the accident flight? At the age of 21?

[Organfreak]

Claudette:
"DON'T PULL" flashing on the PFD in time with the stall warning?

More useful would be, "TILT". (And...you'd lose your quarter.):p

[Lyman]

First of all, "PULL" is TAUGHT as a partial in approach to STALL. It is a version of "Maintain Altitude".

Secondly, on the PFD already was ALTERNATE LAW in AMBER. Piloting an a/c in the conditions 447 found herself takes more than second grade reading skills.

Failing more data, I will never understand the PF's actions. Never. Without context, and perhaps there is none, all that aft stick is bizarre. Equally mystifying is the utter lack of "conversation" on the flight deck. I do not believe it was so, there is more to hear. If wrong, I will apologize in time. The Human Factors group is stuck with the hot potato, No? To make conclusions, they will have to support them. In this support I think more shall be revealed.

[A33Zab]

on the PFD already was ALTERNATE LAW in AMBER


You confuse PFD with ECAM....
ECAM message is F/CTL ALTN LAW(PROT LOST)

The only messages you will see on PFD is RED "MAN PITCH TRIM ONLY"
or AMBER "USE MAN PITCH TRIM" or a FMGS related or EFIS switching message.

[gums]

Good grief.

I thot most here agreed that the crew

- Pulled versus "neutral or even down command on the stick
- Had poor coordination
- Couldn't figure out they were stalled because the jet didn't shake, rattle and roll all that much

The pitot heat needs to be examined, for sure. But it is not going to be "found" as a primary "cause" by the investigators. The jet can fly real fine with only attitude and "manual" power settings while working out the UAS problem, right?

It's gonna be all pilot/crew error.

[PJ2]

Lyman;
Re, "Without context, and perhaps there is none, all that aft stick is bizarre."

Without spending too much time reviewing old ground, I had some time ago posited the notion that the PF was executing one of the memory items in the UAS drill.

In the BEA Second Interim Report pgs 54 & 54, Section 1.17.2.4, it is noted that the UAS event was included in the 2008-2009 recurrent training season. The training included a booklet, the contents of which are briefly described in this section.

The training script for the recurrent simulator session in which the UAS event was included and which the PF First Officer had taken on February 2 2009, (the PM First Officer had received this training a couple of months earlier), required that the aircraft remain in Normal Law with no warnings triggered.

The UAS scenario used in this simulator session was a loss of airspeed information just after takeoff.

In such a case, the safe conduct of the flight is impacted and the memory items of the UAS drill are to be executed.

After ensuring that the autopilot, flight directors and autothrust are set to OFF and if below thrust reduction altitude (nominally either 1500ft AGL or more recently, 1000ft AGL), TOGA thrust is set and the initial "safe" pitch attitude is set to 15deg NU.

At slightly higher altitudes (thrust reduction altitude to FL100) the thrust levers are set to the "CLB" (climb) detent and pitch is set to 10deg NU. Above FL100 and if the safe conduct of the flight is still impacted, pitch is set to 5deg.

The last item in the memorized group states that once the aircraft is above circuit altitude or MSA, (Minimum Safe Altitude), the aircraft is leveled off for troubleshooting.

The FCTM (Flight Crew Training Manual) dated February 2007, though not the legal operational document (only the FCOM is) states that if the safe conduct of the flight is not impacted, the memory items are not to be executed and the crew must reference "part 2" of the QRH UAS checklist for correct pitch and power settings. In other words, present pitch and power settings are maintained while the QRH is brought out and the checklist read by the PM.

As pointed out by Owain Glyndwr, the failures resulting from the loss of airspeed information are graceful and do not present controllability problems. Loss of airspeed information does not require immediate action when in stable, level flight. So, what explains the immediate action?

I think the PF concluded that with the loss of airspeed information the safety of the flight was at immediate risk and was simply executing what he recalled from the earlier simulator session.

As the BEA Third Interim Report states, neither cockpit discipline nor SOPs were followed, and in combination with the effects of the immediate, strong pitch-up commands and subsequent aircraft response taking the aircraft out of stable, controlled flight, I think this prevented them from perceiving and then assessing what was happening.

The situation became immediately confusing as to why the airplane was behaving the way it did, (two momentary stall warnings, due strong pitch-up commands) and the returning airspeed information after about 28 seconds, and a likely clearing of ECAM faults as the airspeed data returned to normal, presented confusing signals to the crew. By this time the airplane was approaching the stall at the apogee of the climb.

Once the pitch-up occurred, a cognitive dissonance rapidly emerged from the differences between expected aircraft behaviour and what they were seeing/hearing. Putting it differently, the pitch-up was expected to be the "correct" response but it wasn't producing the expected stability. Normal perception of the stall warning was blocked because they were trying to resolve cognitive expectations with what was happening).

There seemed to be the expectation that the aircraft would respond at cruise altitude the way it would right after takeoff. This speaks to training and experience issues of manually flying transport aircraft at cruise altitudes and of knowledge and understanding of high altitude, high Mach number flight.

I'm speaking here as a pilot of course, but I think these are reasonable, if not at the moment theoretical, human factors.

gums;

Precisely.

Issues arising from this may be the loss of stall-warning below 60kts and some form of audible signalling when the trim is moving but I think the designers/engineers had a reasonable expectation that the aircraft would not be flown in these regimes by competent line crews, and that every contingency imaginable could not be designed against, not, at least, without prohibitive and difficult-to-justify cost.

I think the one very significant issue is however, the design of the UAS drill and QRH checklist which does not reflect with sufficient clarity what is stated in the FCTM. All we need do is review the PPRuNe contributions on this to see that the matter is indeed conflated even among those who fly the airplane. The fact that 36 other crews did not do what many here have claimed to be the "correct" response in cruise, (if above FL100, pitch up to 5deg) is evidence that there is a significant disconnect here. In fact I think even Airbus is confused about this.

[Organfreak]

PJ2 wrote, among many sensible things:
I think the PF concluded that with the loss of airspeed information the safety of the flight was at immediate risk and was simply executing what he recalled from the earlier simulator session.


Bravissimo! Well-done. :D

[Owain Glyndwr]

Without in the least dissenting from what Gums and PJ2 have written, and accepting that the drills were not exactly clear, it is I think worth reminding ourselves that 5deg pitch/CLB is not, of itself, deadly.

At 02:10:50 or thereabouts the aircraft was at 6 deg pitch, 5 deg AoA, climbing gently. The bank had been substantially zero for 15 secs past. The airspeed was 216 kts; which is about 1.17Vs. No stall warning. of course.

Had they stopped at that point or gone to level flight we would not be having all these discussions.It was the second pull up to 17 deg pitch that mattered and which is, for me, completely incomprehensible.

[PJ2]

Well, this is entirely speculative and unsubstantiated! It is only one of a number of reasonable explanations of why the PF almost-instantly pitched the aircraft up to an attitude that, in a transport aircraft at cruise altitude, I still find frightening, and like everyone else I'm just trying to explain/understand. Greatly-reduced damping effects of much thinner air in high altitude flight requires that one be very gentle with the airplane, just like Davies* says. It is no wonder that the stall warning blipped twice, as the AoA at which the stall warning occurs (in Alternate and Direct Laws only) is between 1 and 2 degrees higher than cruise flight AoA's.

Aircraft inertia will continue the physical trajectory of the mass and "fly through" any immediate response by the aircraft to increased lift resulting from an increase in pitch and thus the AoA increases in any such swift changes in pitch, here, to the point of triggering a couple of stall warnings.

Frankly, while such handling is an abuse of the airplane which exhibits a lack of understanding of high altitude flight it's no big deal because the airplane isn't stalled. But none of this explains the continued pull on the stick after the stall warning continued sounding. Any response should have been a full-forward stick to achieve about a 12 to 15 degree nose-down attitude to unstall the airplane...that results in a descent rate of around 15,000fpm.

When the speed begins to increase indicating exit from the stall, a very gentle pull on the stick is required to avoid another high AoA resulting from the higher positive g's during recovery and subsequent second entry into the stall.

This is, or should be, all pretty basic stuff, thus the questions surrounding the continued pull. I think the confusion surrounding the ceasing of the stall warning and then its reappearance is understandable but the extremely high descent rate and unwinding altimeter, (the (older) standby altimeter was going around the dial once every 2 seconds in the sim), should be sufficient to have indicated a fully-stalled aircraft but they only realized that at around FL100 or so.

It's all been thoroughly discussed in seven previous lengthy threads but sometimes a review is helpful.

Owain Glyndwr;

Thank you for this reminder...I fully agree with you that a 5deg pitch attitude (about 2.5deg above normal cruise pitch) is not itself a problem, (I had originally thought and had posted that it was but again learned and changed my views!).

[Lyman]

The second pull to 17 was accomplished by a pilot who had done that before, and not experienced any fatal result. He was repeating what the a/c and the UAS drill taught and were teaching. Pull, TOGA. It's in the book, and not contra indicated. Remember the "second Pull to 17" happened just after the STALL WARN blared, as it had before. Duff speeds? Is it Real?

Because it defeated a stable attitude is IRRELEVANT. You and I know that, but PF's screen was not recorded, remember? Did he purposely leave a stable attitude, only to STALL? I suggest, not on purpose.

A33Zab. Thank you, yes the ECAM. What is more important to a flying pilot, his instruments? His duty to the ECAM and fault resolution? An interesting discussion? Where should the cue appear? On ECAM, along with dozens of other bitches, or on the life and death of what he knows the a/c is doing?

In a very real way, there is a built in conflict on this flightdeck, if only "philosophical". Get out the book, address each warning, alert, team the return to unannunciated complaints? Or handle the a/c? There was little CRM, if any, shall the PF do it all, or must he choose? PFD? The fact that at any given time in this four minutes a plan and some teaming would have helped, the confusion was inconquerable, each opportunity ignored, misunderstood, or wasted.

imo

[PJ2]

Lyman;

As has been reviewed on numerous occasions, the SOPs to deal with an abnormality come under the heading (as you probably know) of aviate, navigate, communicate then deal with the abnormality or emergency. Control of the aircraft is first assured, then ensure terrain clearances, then communicate internally (announcing the emergency/abnormality and calling for the drill or checklist, then when all is done, communicate with ATC then the flight attendants/passengers.

Except for the rejected takeoff and TCAS/GPWS/Stall warnings, no emergency and certainly no abnormality (which this was), requires immediate action and never without crew coordination.

In the RTO for example, crew coordination may be just the announcement "Reject!", followed by the simultaneous closing of thrust levers, selection of reverse, monitoring/applying full brakes and ensuring ground spoilers are up. At a minimum, announcing the drill or checklist ensures awareness and subsequent coordination and appropriate action.

In abnormalities, on the Airbus the PM calls the ECAM name of the abnormality, the PF calls for "ECAM Actions" and the PM reads (silently) and carries out the ECAM checklist items, confirming any non-reversible actions with the other crew member before actioning them. Then the STATUS page is then checked for system/aircraft unserviceablilities and possible performance considerations.

Where/when required either by the ECAM or company SOPs, the QRH is then brought out for further responses to the abnormal. The entire process including high levels of CRM is heavily emphasized in all initial and recurrent simulator sessions, check flights and in the aircraft manuals.

It is against all this that the response of both the PF and PM is astonishing and incomprehensible even given cockpit gradient and lack of command assignment and consequent assessment and decision-making issues. It may be unfair to observe (because I wasn't there, not because it isn't reasonable to expect), but upon initial pitch-up without announcement from the PF which is non-standard and highly irregular behaviour I would have expected the PM to announce, "I have control", level the airplane, call for the UAS checklist and sort it out with the captain later, on the ground.

[Lyman]

Hi PJ2. Again I must salute your patience and wisdom. I do think, though, that in reiterating the proper procedures we can be distracted by just how emergent was the crisis, helped not in the least by the apparent thick skulled behaviour of the pilots, which we both acknowledge. We have the same target, but I think we approach the understanding from different perspectives. Your words describe "best case, best practice." Here, clearly, such was not the case, not with the information we have to hand. I cannot know why the PF started to handle the a/c so quickly, but he did, and right or wrong, I think he had a motive, one he thought was sound. That he should not do that is patent, as we know, again your patience trumps my volatility. I do not have the experience you have, so it may be easier for me to achieve confusion than even our PF. My sense of the cockpit is that there were two opinions on board, that of the PF, whose behaviour we know was incorrect, and the PM, whose only mistake appears to have been that he allowed the PF's opinion to prevail.

Throughout this three year long thread the evolution appears to be that the pilots were not up to it, and the a/c was wasted due to precipitous and unfounded actions. It has been far too long since anyone has written what these three pilots were up against. We cannot be at all sure that the conditions extant at the twenty seconds before and after were conducive to standard action, imo.

grateful to you

[HazelNuts39]

The only messages you will see on PFD is RED "MAN PITCH TRIM ONLY" or AMBER "USE MAN PITCH TRIM" or a FMGS related or EFIS switching message. Interim Report #2 para. 1.6.11.5 (page 47 in the English edition) shows the changes on the PFD between Normal and Alternate law.

[Organfreak]

Lyman:
The second pull to 17 was accomplished by a pilot who had done that before, and not experienced any fatal result. He was repeating what the a/c and the UAS drill taught and were teaching. Pull, TOGA. It's in the book, and not contra indicated.

:eek:
I beg to differ. As was just recently posted (and many times before), that procedure is strictly reserved for UAS near to the ground and for windshear (near the ground). It is patently wrong at high-altitude cruise. That's why it's now being trained, I do believe.

Your words describe "best case, best practice."

The only practice that would have saved them. :*

[Lyman]

"That's why it's now being trained....." qed.

Point being, it was the second time he made that "mistake". Was there a Windshear warning? W/S appeared on ACARS, as did TCAS. Monkey hear, monkey do.... Besides, Pitch is filtered through the computer in AL2, none of his aft stick had as robust a result as had his ROLL. This in itself could have been the confusion's source, one of. Twitchy in Roll, molasses in PITCH. Acute Roll inputs, and chronic in Pitch? Was he treating them the same, respect wise? If he had forgotten and expected both axes to respond the same, his overcontrol in Roll could have incested his PITCH commands? Vice versa?

[A33Zab]

Absolutely agree! Thanks for the addition:ok:

[Turbine D]

Lyman, Re: UAS

Perhaps this will help refresh your memory, a 2006 Airbus presentation that contains some readable data.

http://www.iag-inc.com/premium/AirbusUnreliableSpeeds.pdf

[Lyman]

Hey TD

Thanks for the link. Despite the cartoon format, I see a serious side, and my attempt to shorten and more specifically define the challenge remains. "Speed" is not as descriptive as "Airspeed", and at each opportunity to quantify the problem the manufacturer continued to use full script. I think the acronym is an apt one. As PJ2 points out, BEA picked it up. Whether concurrent or original, the acronym remains descriptive and has become part of the dialogue, I think in a good way. No?

[Baron 58P]

:E:E:E lawyer, asked to define the difference between "unlawful" and "illegal" by the judge in a criminal court case could not define the difference. "Ah", said the judge, "I have always thought that the one was "against the law" and the other was a sick bird!"

[RR_NDB]

Hi,

We are with limited factual information on the case. There are some reasons, we understand.

Trying to understand the "non understandable" reasons of PF (persistent NU) and in a simulation exercise (in doing so, trying to cover
ALL POSSIBLE reasons) and "last but not least" considering that RHS was not recorded (one of "inputs" to PF) i would ask: What kind of information he could see to justify his actions?

The SS sitck to the extreme left was coherent. (bank angle indications were reliable). What kind of possible misleading information could be coherent with (some) PF actions with respect to pitch?

[Lyman]

RR NDB

Reselected PFD's to acquire the BIRD, coupled to reselected autoflight, which drank in 90 knots and showed profound NoseDown? There was a great deal of mystery and yellow tarps on the avionics bay (recovered).

V/sel: 5000 fpm DOWN, etc. The fact remains PF should have relinquished control. The fact also remains he did not. What was he looking at, surely not all blue? Mostly Brown? Why would he ignore PM: "TJIS< here here, we are climbing, go down." He Did Not descend. He saw all blue and continued to pull?

What did Air Caraibes show on the selected PFD during its uncommanded climb?

Down? Nothing?

[Turbine D]

Lyman,

In my post to you, I was not referring to the acronym relative to speed. The message I was conveying was the fact that in 2006, it was documented exactly what to do if one encountered unreliable or erronous air speeds at high altitudes. The correct procedure was available then. It is what PJ2, gums and others have been saying. 2006 is prior to AF447.

[gums]

Trust me, I have not been coordinating posts with PJ2. The nice words from PJ2 and Turbine and some others are great, but sooner or later we have to discuss the very personal opinions of the pilots here with respect to crew coord, warning systems and training.

Correct me if I have some things wrong:

- Some turbulence, but nothing real violent. No SLF's bouncing off the top of the cabin or spilled drinks.

- Airspeed goes tango uniform for some reason, regardless of whether it was icing or a sensor problem by the electrical system.

- System tells crew that airspeed is unreliable or has failed.

- Pilot states that the jet is in an alternate flight control mode and states something like "I've got the plane".

- Pilot sees a need for aileron/roll control and then also pulls up to "x" degrees on the ADI.

- Aircraft climbs and loses velocity ( indicated, true, inertial, whatever).

- warning systems give confusing data

- aircraft momentum allows the jet to drop below an adequate dynamic pressure over the wings to stay outta stall. The "protections" are not working as the AoA inputs are not helping, nor the confusing warning indications.

- aircraft enters a stall, but is still recoverable

- pilot does not appreciate the fact that his inputs are not working like the Airbus public relations brochures claim

- some systems come back on line but the jet is not responding as the PR documents claim, nor all the training in the sim

- aircraft descends for 3 minutes in a stalled condition while crew can't figure out what is happening

- crew never pushes forward long enough, if at all, to unload the wings and gain a decent amount of air molecules over those thingies that provide lift.


So I see a finding of crew error and contributing factors like sensor failure and confusing warning indications and crew training.

Anybody disagree?

can comment, opine on another thread, but we have beat this horse for over two years.

[chris weston]

I'm quite happy with that summary gums, seems entirely fair to me.

Yes I've read every post.

Yes I'm SLF.

[mm43]

"Speed" is not as descriptive as "Airspeed", and at each opportunity to quantify the problem the manufacturer continued to use full script.I'm supprised the manufacturer hasn't adopted "airspeed" in its "unreliable speed" procedure description. Lets face it, ground speed has limited application, i.e. navigational, along with determining windspeed, and taxiing. So to that end, "Airspeed" is the number that counts from V1 in the takeoff roll until passing a similar point in the landing rollout, and it follows that if it becomes "Unreliable", UAS is the acronym of choice.

Reverting back to Robert's comment, "We've lost the 'speeds'" and Bonin's far from unequivocal response, leads me to suspect that Bonin was focused on an earlier discussion with the Capt in which his desire to go higher was rejected on account of the REC MAX limitations due to high OAT. Well, he got his way and went higher, and as we now know the aircraft would have survived at FL380 if it had been "flown" there.

I use "flown" in a sarcastic sense, as the FDR/CVR transcripts (that we have) indicate little evidence of the true meaning of the word.

Passages in the CVR transcript where the words, "You're going up" and "I'm going down?", and similar variations makes one wonder if these two pilots were actually in the same aircraft! It has been stated often in these threads that we do not "know" what Bonin saw on his PFD, but as there were no anomalies on the the PFD's prior to 02:10:05 it is reasonable to expect the same prevailed for the rest of the flight. What we do not "know" and never will, is how Bonin interpreted what he saw. We do "know" what he did. Responsibility for the safe conduct of the flight and what happened that night lies with the Captain, and decisions he made prior to taking his rest period are all relevant.

Hopefully the BEA will have managed to extract some data from the recovered QAR that will provide closure to this matter.

The BEA's factual Final Report will of course lead to the "blame game", where the roll that either of the pilots played in this accident will be sheeted home to rest with those with the deepest pockets. A rather cynical outcome to an accident that I believe ultimately revolves around "human factors" of which all three pilots in one way or another were involved.

[PEI_3721]

gums, good effort; a reasonable summary and findings.
However, to avoid controversy with the use of the ambiguous and often emotive word ‘error’, consider inadequate human performance. Use of this term would provide opportunity to explain (hypothesise) why the human performance was inadequate for the situation. This also avoids the easy blame and train conclusion/recommendation.

[Lyman]

Computer trouble re: quote function.

gums, I agree with everything except the part where you state the pilot acknowledges the a/c is in "some alternate control law", and states "something like" 'I've got the controls'. It didn't happen. No one acknowledged ALTLAW at all except PM when he said "Lost the speeds, Alternate Law." This includes the species of ALTLAW (2). That was eleven seconds post a/p loss, and 9 seconds after the Pilot flying stated: "I have the controls". PF did not mention Law degradation, and seemingly performed none of the (rather loose) UAS protocol. How do we know either knew lost AS was the problem until PM states so? We don't know if PF EVER knew that, he did not acknowledge: his only 'speed' reference was to "some crazy speed". (Overspeed?) The working theory prior to PM "Lost Speeds" could be anything, but likely NORMALLAW, no change was announced, and none acknowledged. Show us where the UAS was sussed after loss of a/p with master caution and cavalry charge and before PNF actually speaks it? (Eleven seconds, enough time to seal their fate?)

It is a matter of opinion only whether the STALL was recoverable. It may never be known, including when it "almost did."

[Machinbird]

Passages in the CVR transcript where the words, "You're going up" and "I'm going down?", and similar variations makes one wonder if these two pilots were actually in the same aircraft!
This phrasing stands out as really unusual for pilots flying an aircraft. I'm wondering how much of this is from translation out of French, and how much is just plain FUBAR?
I would expect to hear the initial advice from PM to sound something like,"You are 300' high and still climbing." It needs a reference to the altitude assignment.

I'm wondering if PM was trying to avoid further unsettling a guy who was already badly rattled?

[Machinbird]

gums, I agree with everything except the part where you state the pilot acknowledges the a/c is in "some alternate control law", and states "something like" 'I've got the controls'. It didn't happen. No one acknowledged ALTLAW at all except PM when he said "Lost the speeds, Alternate Law." This includes the species of ALTLAW (2).
That is correct Lyman. PF's initial lateral control inputs in the BEA 3rd report indicates that he was still using the 'pulsing' type technique of lateral control (That we have seen in a number of YouTube videos of Airbus pilot stick technique) after the switch to alternate law. He may have heard PM's comment about Alternate law, but it never carried down to how he was trying to fly the aircraft. Pulsing would be extremely inappropriate in roll direct.

[Lyman]

Machinbird

I might misunderstand "pulsing" as you employ it. If he was 'pulsing' in Roll Direct, wouldn't the traces be "serrated" to show input/reverse of input as the a/c stuttered in bank angle? A 'choppy' excursion, not a smooth one? The ailerons would be deflecting, stop, then recommence deflection, creating the exaggerated banking we see?

The stick would return to center after each pulse, yes? That stops the bank in ROLL DIRECT? In the traces, I see banking that is smoothe, once commenced, albeit overdone. It may be that the graph has insufficient resolution.

[Machinbird]

Lyman, take a look at this excerpt from the BEA report.
Look at the yellow-amber colored stick move display. Do you see the head and shoulders pattern? Or the Big head, little head pattern. That is what stick pulsing looks like. The other side of the zero deflection line, it is inverted, but it is still there.http://home.comcast.net/%7Eshademaker/InitialLateralMoves.jpg

[Lyman]

Machinbird

I do indeed. My point is that the a/c behaved smoothly in roll, as the actual bank angle shows. His stick is not smoothe, but as has been pointed out, it adjusted rather quickly to DIRECT. AB pilots, as can be seen on YOUTUBE, mix mayonnaise on a regular basis. Looking out the front whilst they do, the a/c is on rails, most impressive. To me, it is difficult to trash their stick movement, given the adequate results we see.

Let me ask a question. The a/c rolled through 8.4 degrees from 0 in the time it took PF to "I have the controls". That is the roll he sussed, I assume from his FD. The a/p dropped at 05, and at 07, it was at 8.4 degrees right. He rolled to the left to 6 degrees in two seconds, per the trace by BEA. The a/c then rolled right sixteen degrees in two seconds, before he arrested, and rolled back to the left. This excursion was 17 degrees. We need to subtract some time for the roll to diminish, then reverse.

I'm getting at roll rate. Rapid, No? The a/c's attitude is not known prior to a/p loss (at least on the graph you show).

I estimate seventeen degrees in 1.5 seconds subtracting for lag. That feels quick for a heavy a/c. Does that establish "Twitchy"? I am not sure how "pulse" is risky in that regime, the a/c won't react quickly enough, (as the actual bank shows)? Aileron overloading? Could one or more ailerons have been damaged to establish an out of rig condition that resuted in the chronic roll to the right?

Nonetheless, and it is asking for an opinion only, rolling that quickly felt like ROLL NORMALLAW? How could he have missed it? The PNF was exasperated enough to say: "Watch your Lateral......" to which PF made no response?

Thanks for your response, and your patience with my questions.

[gums]

Good point PJ, and I am guilty of lapsing into the standard litany.

From a personal view as a PLF, I would prefer "error", implying that the pilot made a mistake versus pee poor training or ability to begin with. I want my crew to be at least "adequate", heh heh.

Make no mistake, the 'bus flies very close to some limits of the performance envelope when at high altitude, and the comments about not climbing due to weight and such show this. Until I went thru a lot of the manuals and such, I had no idea of how close to the mach limit at the alt of AF447. So a simple loss of speed indications is cause for very smooth and precise control inputs, FBW or not. Same for control of the engines, i.e. get rid of the auto stuff and keep the things where they were when the problem happened. That aspect of the throttles may come up in BEA's final report.

I'll return to the lurk mode unless I see something startling or a personal attack. @ Okie...... yeah, I could have done well in the heavies, but didn't want the responsibility. In a single seater, all you have to do is save yourself and you don't take 200 folks with you if you screw up or the jet is really FUBAR.

[Machinbird]

I'm getting at roll rate. Rapid, No? Lyman, for an aircraft the size of the A330, the initial roll and its successors was very rapid. The amount of aileron applied ensured continuation of a rapid roll rate.

There is no reason to suspect any malfunction of the airframe structure, control surfaces, or hydraulic systems in the observed behavior.

Nonetheless, and it is asking for an opinion only, rolling that quickly felt like ROLL NORMALLAW? How could he have missed it? The PNF was exasperated enough to say: "Watch your Lateral......" to which PF made no response? Rolling that quickly did not feel like Normal Law, that is why PF had difficulty in moderating his inputs. He had apparently never flown the aircraft in that environment. His initial control input might have been acceptable for Normal Law, but for Alt 2, it was way too large. Once he set the aircraft to flopping its wings, he didn't know how to stop it. What he did was accelerate (but not moderate) his inputs to try to get ahead of the oscillation. What resulted was a decreasing amplitude oscillation that flipped phases on him at least twice. I posted a chart of the roll oscillation back in December. During the data analysis, it became visible that the interval between half-roll oscillations was decreasing from the initial period.
http://www.pprune.org/6908719-post682.html

[HazelNuts39]

Is the maximum roll rate of about 11°/s shown on the AF447 traces really so rapid?

In normal law (FCOM 1.27.20) the roll rate requested by the pilot is proportional to the side stick deflection, with a maximum of 15°/s when the sidestick is at its stop.

In direct law (FCOM 1.27.30) the maximum roll rate is approximately 20 to 25°/s, depending on speed and configuration. Spoilers 2, 3 and 6 are inhibited, except in case of some additional failures affecting the lateral control.

[rudderrudderrat]

Hi HazelNuts39,

All PF's previous experience in Normal Law in roll was mostly useless when faced with Alt Law.

In Normal Law, a small deflection of the SS to the left would have immediately commanded sufficient aileron (up to max deflection if necessary) to arrest the roll to the right and provide a slow roll left.

In Alternate Law a small deflection to the Left would have merely reduced his roll rate to the right. He would have needed more SS deflection to the left than he was used to. Relaxing the SS would have allowed the aircraft to roll right (rather than reduce the roll rate to zero in Normal Law). He has no aileron trim to reset the balance point, and probably only ever used the rudder trim when he was last One Engine Inoperative (in the sim).

He had to relearn Alternate Law handling characteristics quickly. How much he had to learn would depend on the last time he had practised the procedure at Altitude. When was that I wonder?

Once overloaded, he lost the plot with pitch attitude.

[HazelNuts39]

In Alternate Law a small deflection to the Left would have merely reduced his roll rate to the right. He would have needed more SS deflection to the left than he was used to. Relaxing the SS would have allowed the aircraft to roll right (rather than reduce the roll rate to zero in Normal Law). Isn't it the opposite?
Once overloaded, he lost the plot with pitch attitude. I'm not sure that he was 'overloaded'. Why would a slow roll to the right or 8° of bank put so much stress on him?

[rudderrudderrat]

Hi HazelNuts39,
Why would a slow roll to the right or 8° of bank put so much stress on him?He had probably never handled the aircraft at FL 350 in Alt Law before. In Normal Law, a small ss deflection left would have commanded sufficient aileron to roll it towards wings level, then if he let go of the ss the roll rate would have been zero.

If you examine his ss deflections in Machinbird's post, he was struggling to find the roll rate neutral balance point of aileron deflection. When he relaxed on the ss, the aircraft continued to roll. Simply holding wings level was taking more of his concentration.

[RetiredF4]

Let me drop in for one remark to HN39 quotes:

Is the maximum roll rate of about 11°/s shown on the AF447 traces really so rapid?

In direct law (FCOM 1.27.30) the maximum roll rate is approximately 20 to 25°/s, depending on speed and configuration. Spoilers 2, 3 and 6 are inhibited, except in case of some additional failures affecting the lateral control.

I'm not sure that he was 'overloaded'. Why would a slow roll to the right or 8° of bank put so much stress on him?

The cause for trouble is not the roll rate or the bank itself, it´s the rollrate and bank near the maximum of the flight and speed envelope. Using 20°/s roll rate at 5.000 feet might be sporty, using them at FL 350 is imho insane.

[HazelNuts39]

Using 20°/s roll rate at 5.000 feet might be sporty, using them at FL 350 is imho insane. Agreed. That's why Annex 3 of Interim Report #3 recommends making "small corrections".

[Lyman]

It is comforting to consider the lack of excessive g in 447's maneuverings post a/p drop. What may be hiding in the sensed "feel" of less than ultimate g on the a/c are the stresses at the various control surfaces. This is a heavy. The controls are large enough to produce lively excursions in PITCH and ROLL at all altitudes.

I don't know the M/E's here, but I am not one, and am interested in loads, stress, and response; how these parameters can produce damage to the airframe, where local loads cannot be borne. Rapid cycling can damage hinges and skin.

I am not trying to reinvigorate the "Lost VS" kerfuffel, nor the other arguments.
I don't propose the a/c broke, only that it is possible, and that there are hints of the possibility in the data. There are slim chances of proof anyway, to my knowledge, each surface operates in anonymity, though I am sure some doubts can be borne in discussion.

[CONF iture]

It is true you can lose the largest part of a surface control without generating a single ECAM message :

http://i45.servimg.com/u/f45/11/75/17/84/310_ru10.png (http://www.servimg.com/image_preview.php?i=138&u=11751784)

Here it was the rudder but what about one or more ailerons on AF447 ?

[Lyman]

The first clue of a possible impairment happened in autoflight. The V/select reported as 5000 fpm descent. If accurate (the a/c did not remain in this config, only commanded, rejected), the a/c was countering a 50 knot climb, or compensating for a chronic misalignment of THS and/or elevators.

As to RUDDER, I believe the pin is actuated within the fuselage; any "position" would be Pin Only, not necessarily to include the Rudder itself. So RTLU reports the drive portion position. Of course, the Rudder is assumed to be attached thereto.

HazelNuts39. At static deflection, yes. In cycling, the loads (calculated) can be much greater? The airplane's stresses are "independent" of a transiting aileron, yes? Are you assuming Still Air? In turbulence (again, calculated) the stress can multiply, of course.

And that is assuming a full complement of control surfaces at less than max deflection. At cruise, fewer surfaces are utilized, and at less deflection (small inputs). If all surfaces are not available, the ones remaining to accomplish the maneuver must be at max. (Spoilers locked out, eg).

[Machinbird]

Lyman, before you go traipsing too far off into engineering La La Land, let me point out that the aircraft control systems were functioning as designed later in the flight, that the control gains were designed to be appropriate for that portion of the flight envelope and the aircraft was well inside its envelope, and the decision by the engineers was sensible since in Alternate 2 law, the aircraft did not require using as many spoilers based on actual flight tests results and calculations of spoiler effect on wing bending moments.

There is plenty of evidence to explain the performance of the aircraft as the effect of turbulence and pilot control inputs.

Take a look at the Cooper-Harper pilot rating scale located here:fig66 (http://history.nasa.gov/SP-3300/fig66.htm)
If you were to ask PF right then about flying qualities, he would have been in the 8 or 9 area, but in retrospect we can assign it a 10 (because he lost the plot in pitch)
(rudderrudderrat has the idea.)

Right about now, I anticipate that all the experienced Airbus drivers will have their hackles up and snorting a loud "Bull Sh&t." "I've flown in those conditions and you just have to be gentle with it." And you would be 100% correct. The problem is that PF had never been trained for that corner of the flight envelope and started off on the wrong foot with it. To be specific, he used an improper control strategy. That was the beginning of the end for AF447. There was time to save the day later, but by then, the crew was too rattled to work their way out of the situation.

At least, that is my take on the HF side of this accident.

[RR_NDB]

Hi,

CONF iture

Here it was the rudder but what about one or more ailerons on AF447 ? (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7075805)

It is technically feasible (and not costly) to detect this type of failure (on the fly :)).

In new designs and existing (easy retrofit). Sensing aerodynamic pressure "reflected" on actuators. No load (or light one) means less surfaces like your example.

Curiosity: info on this incident, please.

[RR_NDB]

Hi,

Machinbird:

To be specific, he used an improper control strategy. That was the beginning of the end for AF447. There was time to save the day later, (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7075914)

:ok:

the crew was too rattled to work their way out of the situation.

With a better man machine interface this HF "disaster" could be reverted?

[RR_NDB]

Hi,

RetiredF4

Using 20°/s roll rate at 5.000 feet might be sporty, using them at FL 350 is imho insane. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7075639)

Important point assertively mentioned!

And prior to any other "pitch stimuli"

Showing a completely inadequate handling technique.

With the enormous responsibility yet in the "correction loop" as one crucial "element".

Other than possible wrong indications (due AS anomalies) the displayed bank angle were reliable (and redundant)

[RR_NDB]

Hi,

Garbage in is not allowed by IT personnel wisely because will generate Garbage out.

Question:

Considering PF is "inserted in the loop" when A/P (and A/THR) drops why PF of AF447 told about "crazy speeds"?

The System presents to the crew, Garbage (AS)?

If IT system is not fed with garbage, why erratic and conflicting data could be fed to "organic processors"?

This is safe during the transients? For example just after Law degraded.

This (garbage to the crew) promotes "graceful degradation" of the "Effective System" (system + PF) or could promote (briefly) accelerated degradation?

[RR_NDB]

Hi,

A33Zab

Heater is 2 elements of resistance wire, ~34 Ohm @ 20°C. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-5.html#post7070290)

Why in series?

[wiggy]

Look, even at high level it's not that difficult, controls are soggy not firm :sad: but hey they still work.

Straight and Level Two as I taught it for years = Power plus Attitude plus Trim = Trimmed Performance.

Never mind complicating the issue by programming in benign failure, all the crew needed to do, even if the autopilot dumped the problem in their laps, was fly the S&L attitude and leave the ****ing power where it was.

That they weren't trained to do so, or that Airbus/AF encouraged a mindset that the software will save you, is the real problem.

[Machinbird]

Considering PF is "inserted in the loop" when A/P (and A/THR) drops why PF of AF447 told about "crazy speeds"?Mac, If you will recall, the statement about crazy speeds was likely not the result of the instrument displays, but from the noise of the turbulent flow around the aircraft (due to extremely high AOA). Actual airspeed indications were largely Invalid due to the extremely high AOA, or extremely low-for the same reason.

[RR_NDB]

Hi,

gums

we have to discuss the very personal opinions of the pilots here with respect to crew coord, warning systems and training. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-7.html#post7074731)

As i understand, when PF is "inserted in the loop" due A/C anomalies, "crew coord, warning systems and training" becomes much more critical. Man machine interface must be very good (and simple up to a certain limit).

THS silently moving, SS of other pilot not viewable, etc. sounds like a threat to the "CRM involving the automatism features of the plane"

Mac.

PS

"CRM" in the sense of Management of all resources (including the auto ones) like THS.

[Lyman]

Was it not the sound of the crystalline ice shower? Was it sound at all? Didn't he just "feel like we have some crazy speeds". We are at a linguistic disadvantage,
French is a challenge for me.

EG. If climbing and airmass is supplying some of the energy, rate of climb can be inconsistently sensed? Climbing "too quickly" for the expected g?

[Machinbird]

A33Zab

Quote:
Heater is 2 elements of resistance wire, ~34 Ohm @ 20°C. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-5.html#post7070290)
Why in series?

Mac A33Zab can follow up if he wishes, but I think I can answer this.

First, there are two heaters in the pitot tube, one for the pickup barrel of the tube, the other for the watertrap area of the tube. The reliability of the pitot tube heater elements is very high. The current is monitored by the control computer. You want to know if there is a heater malfunction in either heating element. When in series, if either fails open, you know about it in a timely manner with a single current sensor. Since you have redundant pitot tubes, a single failure is no big deal by itself.

[RR_NDB]

Hi,

Machinbird:

Since you have redundant pitot tubes, a single failure is no big deal by itself. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7076289)

I would design like that. it is correct.

Thank you

Mac

PS

A33Zab could help us in more important questions :)

i am scanning fast previous posts after a "difficult mission" (trip) and now preparing to post a continuation of the "PF in the loop, transient" issue. Part B will cover from 350 to apogee. When like you precisely said, they had the beginning of the end. :{ by completely inadequate handling at this FL. And Why? Very interesting issue.

[RR_NDB]

Hi,

Machinbird:

If you will recall, the statement about crazy speeds was likely not the result of the instrument displays, (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7076272)

My rationale was based in the speeds (in plural). And also because "crystalline ice shower" (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7076285) IIRC started before.

And,

the noise of the turbulent flow around the aircraft (due to extremely high AOA


Occurred IIRC later when A/C was stalled. "turbulent flow around the aircraft (due to extremely high AOA"

The timing must be reviewed to verify. My feeling is of crazy speeds saw in his side and ISIS.


Plz, not consider:


Argument for my rationale:

Actual airspeed indications were largely Invalid due to the extremely high AOA, or extremely low-for the same reason.

So erratic, "viewed" as crazy.

Error!

[RR_NDB]

Hi,

Bear, :)

Was it not the sound of the crystalline ice shower? (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-8.html#post7076285)

Based in a "pattern" memorized when read pertinent data (essentially BEA) my feeling was PF phrase was due what he was seeing.

This feeling could be verified looking the timing since start of ice crystals noise to the "crazy speedS" phrase.

Mac

PS

I posted before this analysis. Decision making, risk taking.

[Lyman]

RR NDB

I think it is very hard to be accurate with this conversation. Firstly, it was hardly "discourse". I think also it was not CRM. If the CVR releases are complete, I would be astonished. I believe much is witheld, and, again, the translation is questionable.

If memory serves, Bonin mentions only "speed". Crazy or otherwise, crazy is not cockpitspeak for any condition I am aware of. PNF is closer to the ideal, but it is not fair to make any finding: conversation.

Entirely lacking context and continuity, until the final is in, this banter is confusing at best!

May your beacon find a direction, bear.

[RR_NDB]

Hi,

Bear,

Probably facing a glitch, :)


I believe much is witheld, and, again, the translation is questionable.

Certainly.

but it is not fair to make any finding: conversation.

I was looking to "garbage in" fed to PF. So, "crazy speeds" could be a confirmation for that.

Again very limited factual information (necessary) and others factors like you mentioned.

I will investigate closer this point.

May your beacon find a direction, bear.

Sometimes our beacon could present "crazy headings". :):}:E:{

Intermittent failures were one of my nightmares. I had one in RR (375 KHz) NDB many years ago. And in the return flight to my base it failed again, :{

Nothing compared to intermittent failures in "feedback Systems" where also the "failure" is feedback to the inputs of the System. :}

[RR_NDB]

Hi,

I learned from CJ, on the Concorde YD was slightly disturbed when HF radio was transmitting. Yaw Damper is a good example of a "closed loop" feedback System.

EMI/EMC aspects caused this problems later solved, i guess through shielding, etc.

PF was inside the loop after A/P and A/THR dropped.

As i understand, his "inputs" came from the displays ahead of him and from other "inputs" like noise, G, etc.

His actions with SS were clearly inadequate specially near the "corner". For example, roll.

Question:

His initial "pitch up", the ones that put the A/C in the zoom climb could be justified by a set of erratic "inputs" he saw?

The change of speed to alt could be a "based" decision (acting thinking to be under imminent risk) and putting the plane above REC MAX?

[jcjeant]

Hi,

Was it not the sound of the crystalline ice shower? Was it sound at all? Didn't he just "feel like we have some crazy speeds". We are at a linguistic disadvantage,
French is a challenge for me.About "Crazy speed"
This is the exact transcript of the BEA in report N°3 in french language

J’ai l’impression qu’on
a une vitesse de fou
non qu’est-ce que vous
en pensez ?

I translate this as:
I have the "feeling" (impression) we have a crazy speed ... what do you think ?
So it's an evidence that this remark is not the consequence of instruments reading .. as he use the word "feeling"
what do you think ?
Add to the fact of "feeling" as he ask the other for infirm or confirm his "feeling"
This feeling may be the result of what he hears .. or an internal message of his body

[NARVAL]

QUOTE JCJEANT
J’ai l’impression qu’on
a une vitesse de fou
non qu’est-ce que vous
en pensez ?

I translate this as:
I have the "feeling" (impression) we have a crazy speed ... what do you think ?

You are perfectly accurate in your translation. I would add that in French," une vitesse de fou" applies to very high, excessive speed. A speed very much above what you would expect, and completely abnormal.
We cannot be sure we have the whole exchange from the CVR...The sentence translated is not technical, factual language normally used in cockpit conversations. It is certainly expressing high stress, and the anxiety of not understanding the situation as far as speed is concerned.

[A33Zab]

CONF iture:


Here it was the rudder but what about one or more ailerons on AF447
?


RR_NDB:


It is technically feasible (and not costly) to detect this type of failure
(on the fly http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif).



Looking at the aileron & spoiler traces:


If NOT in A/P control the outboard ailerons are centered (active zeroed) at speeds above 190Kts. (Active zero =1.4[/FONT]° up)[/COLOR]

(In A/P control or certain failure modes outboard. ailerons can be controlled up to 300Kts)

This transition is visible @ 02:10:05 at A/P drop off.

The trace shows also the outboard ailerons remain centered all the way down even when the CAS was well below 190Kts.

This could be another protection from the PRIMS (due to rejection of ADIRU's?)

The position is sensed by the LVDT inside the servo actuator and not the actual surface position.

There is no separate surface position RVDT like in the elevator and rudderdesign.

However the adjacent servo-actuator (while in dampening mode) is still monitored and since this one is driven by the aileron it reflects the actual surface position.

If there is any difference between the active and the dampening servo a fault message will be triggered. (And aileron faults were NOT present)

There were NO outboard aileron commands from PRIM and because there were also NO aileron fault messages present, we can conclude the surface was still attached.

However we CANNOT conclude nor exclude the outboard aileron surfaces were completely undamaged.

The inboard ailerons did receive commands, A/C did respond to these commands and failures were absent.

***

From the spoiler trace:

In ALT 2 spoiler (roll function) 2, 3 and 6 are inhibited.

The only glitch you will find in the FDR trace is after ~02:13:35.

Traces of spoiler 5 (cyan) & 6 (amber) shows peaks thereafter, this could be the moment the PRIM 1 and SEC 1 were switched off.

#5 is controlled by PRIM 1 and #6 is controlled by SEC 1.

If the peaks are caused by aerodynamic loads we can conclude the surface(partly?) was still connected to the servo. (Spoiler position is also derived from the servo-actuator LVDT).

[RR_NDB]

Hi,

A33Zab,

Fine biz,

Kind rgds.

[CONF iture]

The trace shows also the outboard ailerons remain centered all the way down even when the CAS was well below 190Kts.
This could be another protection from the PRIMS (due to rejection of ADIRU's?)
That question should be addressed by the BEA ... let's wait and see.
The SECs should have taken over, no ?

I remain very surprised at your (and other's) "eagerness" to find (potentially catastrophic) failure with the aircraft.
My only eagerness is to make sure the victim's families have access to all the data, not only part of them. There is no excuse for the Judge not to include them in the proceeding. We want to know what happened, everything, not only what the crew did wrong.

[sebaska]

The trace shows also the outboard ailerons remain centered all the way down even when the CAS was well below 190Kts.
This could be another protection from the PRIMS (due to rejection of ADIRU's?)

That question should be addressed by the BEA ... let's wait and see.
The SECs should have taken over, no ?

No. SECs don't take over valid PRIMs. In case of unreliable airspeed many protections remain as for a last valid speed.



I remain very surprised at your (and other's) "eagerness" to find (potentially catastrophic) failure with the aircraft.

My only eagerness is to make sure the victim's families have access to all the data, not only part of them. There is no excuse for the Judge not to include them in the proceeding. We want to know what happened, everything, not only what the crew did wrong.

But wild speculation does not bring families closer to truth, it only decreases signal to noise ratio. You want the data not a garbage. :ugh:

This was addressed by BEA in interim reports that both wreckage as well as FDR recording indicate no structural failure up to the impact. Plane was responding to stick deflections, and was symmetric aerodynamically (otherwise it would not fall flat, wings level at such extreme AoA). It was (for many) surprisingly stable (many planes would need to enter flat spin to fall wings level from fl370 down to the .

Wild and unfounded (and in fact contrafactual) speculations were plenty here. When BEA said that fracture analysis of found rudder indicates almost flat impact with little forward speed and small roll to the left many here dismissed it and continued to speculate about plane disintegrating mid air. Then "black boxes" were found and read and surprise - they perfectly agree with that early rudder analysis. Yet still some contrafactual speculations surface all the time :=

[jcjeant]

Hi,

You want the data not a garbage

Indeed .... :)
Google Traduction (http://translate.google.be/translate?sl=fr&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fteleobs.nouvelobs.com%2Farticles%2Fvol-af-447-rio-paris-les-raisons-d-un-crash-le-docu-fiction-sera-t-il-diffuse&act=url)

[HazelNuts39]

In case of unreliable airspeed many protections remain as for a last valid speed.Except for the RTLU, that is new information and it would be helpful if you could elaborate on that.

According to BEA's Interim Report #3 p.27 (English version): The calibrated airspeed recorded in the FDR is that displayed on the left-hand PFD, unless it is invalid (if the speed is less than 30 kt, in which case the SPD flag replaces the speed scale). The recorded airspeeds remained above 30 kt until at least 02:11:45.

Perhaps it one should distinguish "invalid" from "erroneous". At least one airspeed value became erroneous at 02:10:04.6. The ECAM message NAV ADR DISAGREE was generated after 02:12:00, so until that time at least two of the three airspeed values must have been within tolerance of each other, erroneous or not, but still 'valid' until 02:11:45.

[HazelNuts39]

Can anyone explain why there is a SPD flag on the left PFD between 02:11:40 and 02:11:45? (p. 44 of I.R.#3 EN)

[Lyman]

Could those have been two (incorrect, but consonant) speeds upon which PF based his "Overspeed"? Plugged Drains only? Hence the continued PULL?

For that matter, if reading high, wouldn't A/P have input NU, and for how long prior to loss of reliable speeds?

Don't mind me.

[HazelNuts39]

Could those have been two (incorrect, but consonant) speeds upon which PF based his "Overspeed"?No, the speed from ADR2 that was not recorded would have been close to either ADR1 or ADR3 (when different) which were recorded. Note also that the right PFD was showing the speed from ADR3 between 02:10:40 and 02:12:17.

Since the CAPT pitot and the F/O pitot are mounted in exactly identical symmetrically opposite positions on the forward fuselage, while the STBY pitot position is below the CAPT's and therefore in a slightly different airflow, I would expect ADR2 closer to ADR1 than to ADR3.

[A33Zab]

Can anyone explain why there is a SPD flag on the left PFD between 02:10:40
and 02:10:45? (p. 44 of I.R.#3 EN)


My copy of (p. 44 I.R.#3 EN) shows speed flag @ 02:11:40 not @ 02:10:40.
Is my copy again outdated? or do you need to increase the font size a little bit:)


while the STBY pitot position is below the F/O's


Minor correction, STBY is below Capt. probe, to be exact 60° below datumline (Z=0) while Capt and F/O are @42°.

[HazelNuts39]

A33Zab;

You are correct on both counts, thanks for pointing that out. I've edited my post to correct the errors.

[A33Zab]

No thx,

BTW, very good observation! I don't have an answer.
Airspeed acc. graph was still above 30Kts.

Confirmed by the CVR transcript pages @ 02:11:40:

The CAS is 106 kt and the CAS ISIS 112 kt.


But this is contradictionary with:

The FD 1 and FD 2 become unavailable.
The angles of attack 1 and 2 become invalid (NCD status)


Which implies CAS 1 AND 2 are <60 kt.

[CONF iture]

No. SECs don't take over valid PRIMs. In case of unreliable airspeed many protections remain as for a last valid speed.
Outboard ailerons did not move when they should have. If there is a logical explanation, and there could be one, I would like to hear about it ...

You want the data not a garbage.
Exactly my point. Full data to the families. FDR especially.
Airbus has full access to the data, which makes sense, naturally the families should also, why not ? What's the problem ?

[Hamburt Spinkleman]

Outboard ailerons did not move when they should have.They should not have moved. The EFCS retains the configuration associated with the last known good speeds. When the ADR monitoring began, the flight control configuration was locked, including RTLU and ailerons.

The rest is pure politics and anyone can spin that as they please.

[Lyman]

Also THS? Flap? RTLU froze the Rudder. Does the lock remain locked? Also, do spoilers remain inhibited, and for how long? If speeds return, are controls all available? Also, if ailerons inhibited, how did ROLL DIRECT retain so much authority, without the outers?

Thanks for info sir.

[HazelNuts39]

But this is contradictionary with:
Quote:
The FD 1 and FD 2 become unavailable.
The angles of attack 1 and 2 become invalid (NCD status)

A drop of 30 kt in 1s of either the median or the mean IAS around 02:11:40 could again have triggered the monitoring of the airspeeds by the FMGEC and the EFCS. That would explain the loss of the FD's, but not that the AoA's became NCD.

[A33Zab]

The ADR monitoring of FMGEC is a continuous process and rather complicated...:8
simplified it needs at least 2 valid sources for the command side, OWN ADR and ADR 3, with OWN ADR as default.
But the monitoring side takes all 3 ADRs (if valid) in account.
Don't know the exact influence of F/O switching to ADR 3 on monitoring logic.

Anyway:
@02:10:40 CAS (#1) seems to be in same range as ISIS trace (~ADR3).

[CONF iture]

That would explain the loss of the FD's, but not that the AoA's became NCD.
02:11:40 CAS measurements are still above 60kt but not 5 sec later.

When the ADR monitoring began, the flight control configuration was locked, including RTLU and ailerons.

RTLU was initially stuck then non available, but what is your reference for the ailerons ?
Please quote ...

[Lyman]

Clearly, many here are conversant with the 330's systems, and its pilotage. I certainly am not. So I am curious as to some things.

When the ADR's begin to be interrogated by the computers, as to reliability, isn't this ongoing? Or is this 'suspicion' the result of already sensed anomaly? Because if it involves locking of control limits (certainly not locking controls, that would be crazy), are the pilots on board with the 'suspicion'?

Most certainly, right? Wouldn't the flight crew be apprised instantly if A/S was thought sour?

As in: "Monsieur, the computer is interrogating our displays, heads up..."

Would that be the cue to start UAS protocol? Certainly. So Bonin was informed at the outset of the 'beginning' of UAS? At least its possibility?

Now, since H. Spinkleman has stated the controls' limits are locked at the beginning of such interrogation, may we assume the THS stopped trimming shortly after? It is shown, FDR, the THS remains at 3.5 degrees until just at apogee? Bonin knew this of course, he was without trim to PITCH.

Another has said, essentially, that all control surfaces were acounted for until late in the game. I differ, here. Since the ailerons reporting is accomplished by its actuator, the aileron 'need not be present' to be accounted for? Similarly, an elevator is in the same situation? Is there a tickle conductor to the Trailing edge, so, if its continuity is interrupted by surface separation, it is known in the cockpit/ACARS? I have not heard of one.

The "Aircraft handled in predicted response per the FDR". That's nice, but it does not account for all controls' surfaces to the strictest extent. The recovered spoiler separated at its attach to its actuator; the recovered elevator, at its hinge line. It is acknowledged that to entertain control surface separation may be difficult, even fearful, but thus far, we have BEA saying that the a/c impacted "......complete". They did not say "Completely intact, whole".

[Machinbird]

Lyman, I know lawyers speak the way you speak all the time, but would you mind writing in simple un-convoluted English for a change. It might help present your points more clearly. Choose simple words instead of the $5.00 words please.

[Lyman]

Swear to God Mach, are you kidding? 5.00 words? Show me one, give me some direction. I'd be happy to edit.

sub Mach

Are the pilots 'told' instantly when the computer doubts the Speeds?

Did "control limit locking" involve THS?

Are surfaces linked to the computer, or just the actuator?

etc.?

[HazelNuts39]

The ADR monitoring of FMGEC is a continuous process and rather complicated...
I'm referring to the "10 seconds" speed monitoring process described on page 55 of BEA's Interim Report no.1 and again on page 40 of I.R.#3. It is triggered by a decrease of more than 30 kt in one second of the “polled” speed value. The polled speed value is the "median" or middle value of three valid ADR's or, if one ADR has been rejected, the mean of the two remaining values.

[Lyman]

HN39

A decrese of 30knots/sec? Only? Not to include an increase of the same value?

Will someone say if the flying pilots are made aware of the urgency of the monitoring process post 30knot/sec. sensed? Are they "in the loop"? Or do they have to wait for the 'generic' cavalry charge and "MASTER CAUTION" without elucidation from the panel? My sinking feeling is that they are not made aware, that they have to await, in ignorance, the 'decision" of the Computer. No "Speeds" notation (verbal) exists until eleven seconds after a/p LOSS.

Did the AutoPilot quit at start of monitoring, and, ten seconds after its loss, the pilots were 'told'? Sounds impossible.

[A33Zab]

RTLU was initially stuck then non available, but what is your reference for
the ailerons ?


RTLU was not stuck, as in jammed, it was freezed at the position it was.
this is a protection not a malfunction of the RTLU.
RTLU reset would have been accomplished upon S/F selection.

If anyone can find the reference for the OB ailerons he is most welcome, I couldn't find it in words, but its there in the traces and since the roll function of spoiler 2,3 & 6 in ALT2 are inhibited to decrease the roll rate it is obvious to zero the OB ailerons for the same reason.

[Lyman]

I ask again. The ailerons and spoilers inhibit remain in ALT 2? Where does she get her reputation for "twitchy"? And wouldn't this be counterintuitive, since Roll would then demand maximum from surfaces that were not intended to produce rapid Roll Rate?

Or are they limited to prevent excess YAW, the remaining Roll controls being closer to the longitudinal axis?

[roulishollandais]

My only eagerness is to make sure the victim's families have access to all the data, not only part of them. There is no excuse for the Judge not to include them in the proceeding. We want to know what happened, everything, not only what the crew did wrong.

The BEA report is PUBLIC. Their report is said "administrative".

It is independant from the trial who does his own enquery (yes !) They have their own experts...

We have access only to the BEA enquery results.

The family may ask to the Judge the result of the Justice enquiry two.

The reality is very different : it is totally impossible for the Justice to do an independant inquery. But you have two groups of experts (all are generaly friends or colleagues one of another)...

That is in France ...

[CONF iture]

RTLU was not stuck, as in jammed, it was freezed at the position it was.
this is a protection not a malfunction of the RTLU.
RTLU reset would have been accomplished upon S/F selection.
I used 'stuck' as it is the word they used for the translation on page 40 of the third Interim Report, but am I missing something here :
As the role of the RTLU is to limit rudder and pedal deflection as a function of the speed, and the position of the rudder limiter was stuck, frozen since 02:10:06, why that limit was exceeded when the rudder was suddenly and generously applied after 02:13:00 ?

I have not heard about the slats being extended earlier ...
S/F selection and position is just another trace I'd like to see.

[Lyman]

"As the role of the RTLU is to limit rudder and pedal deflection as a function of the speed, and the position of the rudder limiter was stuck, frozen since 02:10:06, why that limit was exceeded when the rudder was suddenly and generously applied after 02:13:00 ?"

CONFiture. You will need to address the limit strength of the RUDDER actuator v. air loads. Just as the limit strength of the THS jackscrew is compared to the airloads on the THS. When takata posted the picture of the recovered jackscrew, I noted some damage at (near) the end (NU) limit of the screw. The rotation and torsional impetus of the jackscrew would be in opposition to the extreme airloading on the THS. If it failed, and trapped the collet in its near max. position of 13.2, that explains the nesting of the THS from apogee. Logic demands some movement post apogee with ND from PF. None is in evidence.

These questions are unaddressed here, and to my knowledge, not broached in the BEA reportage.

Best regards

[mm43]

Originally posted by Lyman ... Ref THS ...

Logic demands some movement post apogee with ND from PF. None is in evidence.Post apogee the Elevator was mostly at 30° NU and never came below 15° NU - short term. Why would the THS need to follow?

Excerpt from Owain Glyndwr's explanation ...

For virtually the whole of the event, and certainly for the whole time the aircraft was stalled, the THS had a positive AOA so that it was generating upwards lift and a nose down pitching moment despite the fact that it was set at -13.5 degrees! This is consistent with it being a stable aeroplane as shown by that pitching moment curve. Of course the net HS lift was negative and the net pitching moment positive (nose up), but this was made up of a very large downwards lift from the elevators partly offloaded by the positive lift from the THS itself. If the elevator had been returned to neutral the THS lift would have given a ND pitch and attitude reduction. Look at the traces - that is exactly what happened!
The nose was being held up by the application of elevator.

[A33Zab]

As the role of the RTLU is to limit rudder and pedal deflection as a function of
the speed, and the position of the rudder limiter was stuck, frozen since
02:10:06, why that limit was exceeded when the rudder was suddenly and
generously applied after 02:13:00 ?

Because the RTLU is not a Rudder DEFLECTION Limiter but a rudder INPUT limiter.

@~02:13:00 the pedal input was abrupt and full 8° while Yaw damper was deflecting the rudder in same direction max 4°.

So a little overshoot occured (and torsion on the inputshaft) because yaw damper was unable to compensate in time.

http://i474.photobucket.com/albums/rr101/Zab999/A330_MRudder.jpg

I have not heard about the slats being extended earlier ...
S/F selection
and position is just another trace I'd like to see.

Because they were not...

For lieman:

The LL (limit loads) are max loads expected in the normal flight envelope, the UL (Ultimate Loads) are 1.5 LL.
No breaking of the surface occurs before UL.

[Lyman]

Hi mm43

I am reading Glyndwr with jaw dropped to floor. yes?

[Organfreak]

A question:
Because the RTLU is not a Rudder DEFLECTION Limiter but a rudder INPUT limiter.

Is this an add-on made after the AA587 crash? You know, where the pilot got blamed for "excessive rudder input"? (tail broke off) :*

[A33Zab]

Is this an add-on made after the AA587 crash?


No, RTLU is common on A320 series, (PTLU) was added to this system on A34/33 from the start....AFAK.
My ATA 27 pages with diagrams of RTLU and PTLU are dated APR 1993.

But AA587 was A300 isn't it?

[Organfreak]

@A33Zab:
Thank you.
But AA587 was A300 isn't it?

Yes.

[CONF iture]

Because the RTLU is not a Rudder DEFLECTION Limiter but a rudder INPUT limiter.
I feel a bit uneasy by this statement, I must say.

The RTLU set the position of the rudder limiter (physical limitation). In this case it was between 5 and 6 degrees according to the graph on page 112 of the third Interim Report, but 8 degrees after physical observation as stated in the second Interim Report ... why such difference btw ?

The RTLU ECAM MSG then indicates the unavailability for further rudder deflection limitation calculation function, but the position of the rudder limiter was already frozen.

Nevertheless, at 02:13:00 the rudder reached 10 degrees ... not 'a little overshoot'

Could it be the consequence of the limitation value being unfrozen following a slats extension command ... ?
It is clearly mentioned in the second Interim Report that the flaps were retracted but I have not seen a word on the slats ...

Extending the slats could be an attempt to regain control, kicking the rudder like it was done at 02:13:00 could be another one ...

roulishollandais,
The families are 'parties civiles' and should have full access to the data.

[RR_NDB]

I am studying carefully before posting part B and C on "Transient in feedback Systems II" and i have a question "hovering" in my mind. :8

Why not to implement a protection against climbing above REC MAX?


Protections are designed to "protect". It is reasonable to allow a plane climb (at high ROC) towards a FL above this important limit?

[jcjeant]

Hi,

CONF iture
roulishollandais,
The families are 'parties civiles' and should have full access to the data. Indeed .. as plaintiffs families are entitled to access to investigative files
But it's more complicated than that because the judge handling the case has not joined the FDR and CVR transcripts as exhibits to the investigation and therefore .. given the needs of the technical investigation .. BEA has given datas to Airbus and AF .. but not to families since they are not parts of the technical investigation .....
AFAIK
Dura Lex Sed Lex

[A33Zab]

Originally Posted by A33Zab
Because the RTLU is not a Rudder DEFLECTION
Limiter but a rudder INPUT limiter.


I feel a bit uneasy by this statement, I must say.

The RTLU set the
position of the rudder limiter (physical limitation). In this case it was
between 5 and 6 degrees according to the graph on page 112 of the third Interim
Report, but 8 degrees after physical observation as stated in the second Interim
Report ... why such difference btw ?



IMO the TLU trace shows its RVDT angle ISO max. rudder deflection.

Ref. mm43: RTLU GRAPH (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-11.html#post7088235)

Ref. PJ2: R/PTLU (http://www.pprune.org/tech-log/395105-af-447-search-resume-93.html#post5861419)

When the RTLU is at minimal (0° RVDT angle) the RTLU limits the rudder input to 4°, to be accurate this is 3.7° (CMM).
Interpolating the low resolution TLU trace its value was ~4.2° (RVDT angle) just before @02:10:05.
4.2° + 3.7° ~ 7.9° at which it was freezed by PRIM at the start of the speed monitoring process.

The RTLU ECAM MSG then indicates the unavailability for further rudder
deflection limitation calculation function, but the position of the rudder
limiter was already frozen.


The following is purely speculative since I am not able to prove with documentation.

The PRIM freezed the RTLU at the start of the monitoring process, but it can not control it because the TLU electrical motors are driven by the SECs.
The PTLU and RTLU share the control relays but have separate driver circuits inside the SECs. (so far true)

If the SECs continue to drive the PTLU to 5.8° RVDT angle the limiting position of the PTLU will be 5.8°(RVDT angle) + 3.7° ~ 9.5°.
at that position it detected the RTLU is not following its command position and triggers the TLU NOT AVAIL signal and F/CTL RUD TRV LIM FAULLT @ 02:10:18.

Nevertheless, at 02:13:00 the rudder reached 10 degrees ... not 'a little overshoot


The surface xdcr is placed at the lower side of the rudder, the lower servo is attached to the linkage before the RTLU, the upper and center input linkage after TLU.

Taking free play in all swivels & hinges in account the rudder deflection can be a bit more than the RTLUs position. (Due to poor resolution I would say just before 10°......9.5°?)


Could it be the consequence of the limitation value being unfrozen following a slats extension command ... ?
It is clearly mentioned in the second Interim

Report that the flaps were retracted but I have not seen a word on the slats



No, Slat/Flap input is combined (1 S/F lever).


If this was TRUE, the R/PTLU would have been driven to allow max. rudder deflection (35°) within 30 sec.
After 30 sec. this backup circuit will be isolated.



http://i474.photobucket.com/albums/rr101/Zab999/MRudderDwg.jpg

[mm43]

As mentioned by A33Zab, the RTLU graphic he linked to is actually for the A333 (taller Vertical Stabilizer) and the graphic below is for the A332.

http://oi56.tinypic.com/ivvayo.jpg

[CONF iture]

If this was TRUE, the R/PTLU would have been driven to max. rudder deflection (35°) within 30 sec.
No, why should it ?
The rudder pedal position was 10 degrees off max, so was the rudder (page 112)

No, Slat/Flap input is combined (1 S/F lever)
FLAPS 1 selection on ground before take-off does provides both slats and flaps. It is called CONF 1+F
But FLAPS 1 selection in the air for landing preparation provides only slats. It is called CONF 1

Many data are missing ...
The BEA has provided too little.
What the Judge is waiting for ?
Who are those lawyers who pretend to defend the families ... ?

[A33Zab]

@MM43:

THx, edited the link.

@ CONF iture:

Maybe I was not clear, this did not occur to AF447!.

It was a reply on your suggestion of extending the slats.

Extending the slats could be an attempt to regain control

When TLU is deactivated (TLU NOT AVAIL) in flight a safety feature is to allow full rudder deflection when needed - at landing -.
Selecting S/F handle to CONFIG 1 will extend slats and if slat arrives @16° a backup circuit drives the TLUs to ALLOW for full pedal(35°) and rudder deflection (35°) if required.

This would have been visible in the TLU trace.

Many data are missing ...
The BEA has provided too little.


IMO only relevant items have been and will be published.
Nevertheless some questions indeed have to be answered or explained.

[CONF iture]

When the RTLU is at minimal (0° RVDT angle) the RTLU limits the rudder input to 4°, to be accurate this is 3.7° (CMM).
Interpolating the low resolution TLU trace its value was ~4.2° (RVDT angle) just before @02:10:05.
4.2° + 3.7° ~ 7.9° at which it was freezed by PRIM at the start of the speed monitoring process.
Before I adventure further in that exchange, what do mean exactly by 'RVDT angle' ?

[Organfreak]

I don't know s*** from Shinola, but that's never stopped me before. :O

Isn't that an angle sensor?

[Machinbird]

Isn't that an angle sensor? Not quite, or at least not directly. Probably Rudder VDT.
Now what is a VDT? See this link for a clue Modern LVDTs in New Applications in the Air, Ground, and Sea | Sensors (http://www.sensorsmag.com/sensors/position-presence-proximity/modern-lvdts-new-applications-air-ground-and-sea-7508)
We'll let A33Zab grade this exercise.:} (And the winner is Lyman, it seems!)

[Lyman]

Rotary Variable Differential Transformer?


Edit, slow down lyman. Displays my sailboat's Rudder deflection.
.

[A33Zab]

Before I adventure further in that exchange, what do mean exactly by 'RVDT
angle' ?

Maybe this clears up.

LVDTs
The linear variable differential transformer (LVDT) is a sensor used to measure displacement in the industrial environment. An LVDT consists of three coils of wire wound on a hollow form. A core of permeable material can slide freely through the center of the form. The inner coil is the primary coil, which is excited by an AC source as shown. Flux formed by the primary is linked to the two secondary coils, inducing an AC voltage in each coil. When the core is centrally located in the assembly, the voltage induced in each primary is equal. If the core moves to one side or the other, a larger AC voltage is induced in one coil and a smaller AC voltage in the other because of changes in the flux linkage associated with the core.

RVDTs
The rotational variable differential transformer (RVDT) is used to measure rotational angles and operates under the same principles as the LVDT sensor. The LVDT uses a cylindrical iron core, while the RVDT uses a rotary ferromagnetic core.


Item 6 in drawing below are the 4 RVDTs.

http://i277.photobucket.com/albums/kk76/batcave777/AF447/RTLU_2010-08-10_143738-1.jpg

[Organfreak]

Yeah, Lyman, I Googled it too, but I knew they'd know I Googled it, so I didn't post it. (see emoticon)

I did learn that a transducer can be used instead of a variable transformer, with the same effect.

[CONF iture]

When the RTLU is at minimal (0° RVDT angle) the RTLU limits the rudder input to 4°, to be accurate this is 3.7° (CMM).
Interpolating the low resolution TLU trace its value was ~4.2° (RVDT angle) just before @02:10:05.
4.2° + 3.7° ~ 7.9° at which it was freezed by PRIM at the start of the speed monitoring process
Maybe I could dispute or argue on those numbers but to be honest I don't have the knowledge and documentation to go much further in that direction.
And overall I like what you said here :
This would have been visible in the TLU trace

Nevertheless I'd like to see the trace for the S/F lever position, especially when selecting FLAP 1 is at some point part of the STALL RECOVERY procedure.

IMO only relevant items have been and will be published
The AP/FD vertical mode trace is a relevant item for the reason I have already mentioned here (http://www.pprune.org/tech-log/466259-af447-final-crew-conversation-thread-no-1-a-54.html#post6936599) but is nowhere to be seen ...


I do feel for the families of the 3 pilots who are put under such a negative light in such a dishonest and oriented program :

gmUyg2xGZbo&feature=player_embedded

The families need all the data - Those data do not belong more to Airbus and the BEA that they belong to them.

[thermostat]

Lots of ideas from lots of folks. Unfortunately we have no way of knowing their professional backgrounds. Some engineers, some mechanics, some pilots and some ?????
I have said before and I'll say again this crash could not have happened if the aircraft had been diverted around the CBs as others did.
As pilots, we have all been told about the "ERROR CHAIN" in CRM classes. If you bother to look carefully at this accident, you will find many links in the error chain. If someone had broken any one of those links, the flight would have had a happy ending. I can list the links if required.
Pitot heat : Any system can be overloaded past it's limit. My knowledge of these systems on the ones I flew was "low" heat on the ground and "high" heat in the air. These systems are not able to cope with supercooled water of the magnitude encountered by this flight, hence the loss of many systems which are dependent on proper pitot function.
It's been over a year of chatter on how the crew should have recovered from the subsequent stall while in turbulence with many warnings flashing, ringing and blowing and it doesn't seem as if it will end soon. My view however is as stated above. Stay away from CBs at any altitude but more so at high altitude and arrive alive.

[Machinbird]

Stay away from CBs at any altitude but more so at high altitude and arrive alive.
It has been a few years since I roamed the high altitudes with frequently unreliable radars in my military jet, and your statement is very true, but sometimes difficult to fully implement.

Solitary cells are easy to circumnavigate. When they shoulder together in lines and large areas it becomes more problematic. The upper ice crystal portions of Cb clouds are weak radar targets. Although radars can be very helpful, they can also degrade or be mismanaged. When that happens, as it seems may have happened in the AF447 case, it is almost inevitable that you may get closer to a cell or cells than you wished. From the turbulence encountered-judging from the BEA report-they did not fly into the core of a cell, but instead into a peripheral area. But it was close enough to cause a problem.

Sometimes you do not succeed in breaking the first link in the accident chain. For this reason, you should break as many other links in the chain as possible. That is the source of the chatter you remarked upon.

We cannot absolutely avoid some proximity to Cb cells. To attempt to do so would shut down large portions of the world's air commerce. It isn't going to happen.

[DozyWannabe]

in such a dishonest and oriented program ...

Dishonest how, and can you prove it?

The families need all the data - Those data do not belong more to Airbus and the BEA that they belong to them.

What would the families do with it? Who would they take it to? The whole point of investigative agencies that are set up to be independent from regulators and the airlines (of which the BEA is one) is that they have nothing to lose or gain in the outcome. The families could take the data and pay someone to read it, but the conclusions derived from that would be worthless on the basis that the families' lawyers would have paid them to try to exonerate the crew, just as the same allegations could be levelled at DGAC, Airbus or AF if they had a hand in the investigative process itself.

[jcjeant]

Hi,

What would the families do with it? Who would they take it to? The whole point of investigative agencies that are set up to be independent from regulators and the airlines (of which the BEA is one) is that they have nothing to lose or gain in the outcome. The families could take the data and pay someone to read it, but the conclusions derived from that would be worthless on the basis that the families' lawyers would have paid them to try to exonerate the crew, just as the same allegations could be levelled at DGAC, Airbus or AF if they had a hand in the investigative process itself. What would the families do with it?
That's not the good question
Again it's just to try to understand the lawyers position on this problem
It's a law problem .. no more
Airbus is a party cited in the trial has come .. as well as family associations
It should therefore be treated equal .. which is not the case .. since Airbus has access to parts (FDR furnished to them by BEA) that will eventually be used at trial .. while the associations of families do not have access to because that the judge in charge of this case want not joint those pieces to the trial record .. (so far)
Unfair ...simple as that ......
the same allegations could be levelled at DGAC, Airbus or AF if they had a hand in the investigative process itself.
Airbus have not a hand in the investigative process .. fair enough .. but be sure they analyze each stances from the listing of FDR and they can use their results in court if necessary
Family associations do not currently have this opportunity

[DozyWannabe]

But Airbus has not been granted access to the FDR in order to prepare a legal case, has it? It's simply because, as the manufacturer of the airframe, they need to ascertain whether or not there is a defect in the design that could cause more accidents. Are you seriously suggesting that such data be withheld until the trial is complete?

Even with the data that has been released, there are those on here that continue to insist that the zoom climb to stall was uncommanded despite the FDR data proving the exact opposite. Even if the raw data was released to the families, they couldn't do much with it. They could try sending it to the NTSB or AAIB who would in all likelihood tell them exactly the same things that the BEA are saying. The trial wont begin until the full report is released in any case, at which point all the relevant data will be in the public domain.

[jcjeant]

Hi,

But Airbus has not been granted access to the FDR in order to prepare a legal case, has it?Are you naive ?
And again it's not the good question ...
It's regard of laws
The fact is they are cited party in the trial as the families association and must be considered equal..

[lomapaseo]

............. until the full report is released in any case, at which point all the relevant data will be in the public domain...

agree

but I doubt that many posters on this forum will agree on what's relevant, especially if it doesn't match their theory

[jcjeant]

Hi,

agree

but I doubt that many posters on this forum will agree on what's relevant, especially if it doesn't match their theory
Again ....
Nothing to do with theory or shadow agenda .. it's a law problem

[Turbine D]

jcjeant,

I think you are getting the cart placed in front of the horse. It is not a "law problem," so far. Determination of the causes or probable causes have not been determined as of yet. The BEA has the responsibility to investigate the accident, assemble all of the available data and evidence, consult with any entity that may provide greater insight into the potential meanings of the evidence and data including providing of specific information to enable testing and confirmation of potential findings, followed by assembling a final report based on the pertinent data and supporting findings as to causes, probable causes and undetermined causes. At the conclusion of the BEA's investigation the final report is issued and presented to the responsible French Court. At the time this transfer occurs, it then become a "law problem" to be resolved. Prior to this report, no party of interest that cannot contribute to in depth understanding, i.e., technical expertise or human behavior as it pertains explicitly to the accident should have access to the full actual data.

The BEA can (as does the NTSB in the US) choose to release certain preliminary information to the general public it has found to be pertinent and indicate what other tasks are being performed in its investigation as it proceeds towards conclusion. The BEA has chosen to do this through interim reports. The BEA may also decide to privately apprise the families of the victims, out of courtesy, of their investigation methodology, status, etc., perhaps more in detail than what may be released to the general public. It is the BEA's call, but nothing is owed in advance of the final report being written and turned over the French Court.

I am not aware of any highly technical aircraft accident investigation where the investigative body could not consult with the airline operator, aircraft, engine or avionics manufacturers to gain additional knowledge of the system or systems, while sharing available need to know data to hopefully enable correct conclusions to be drawn. It doesn't mean the lawyers to be involved in the future litigation are entitled to this exchange of information at the actual time the exchange occurs.

Dozy is correct in his assessment!:ok: Welcome back Dozy

TD

[jcjeant]

Hi,

I am not aware of any highly technical aircraft accident investigation where the investigative body could not consult with the airline operator, aircraft, engine or avionics manufacturers to gain additional knowledge of the system or systems, while sharing available need to know data to hopefully enable correct conclusions to be drawn. It doesn't mean the lawyers to be involved in the future litigation are entitled to this exchange of information at the actual time the exchange occurs.It's unfortunate you are not aware of the french laws ... :{
Airbus have entire FDR listing
Families associations have not FDR listings
A complaint against Airbus (recognized as valid) was filed by associations of families
Airbus and families associations are two parties involved in the legal process
Both parties must be treated equally
It's nothing to do with investigation .. or technical recommendations ....

[Turbine D]

Originally posted by jcjeant
It's unfortunate you are not aware of the french laws ...

Care to enlighten me? :hmm: Has there been parallel legal investigatory actions on going by the French magistrates while the BEA is doing the technical investigation? The judiciary has priority to investigate any object from the accident site that might be used as evidence which may delay and prevent the safety investigators from carrying out their investigation. Has this happened? Standard 5.12 of Annex 13 explicitly states that the records derived from these devices should not be made available for purposes other than safety investigation unless an appropriate authority has determined that the proper administration of justice outweighs the adverse impact on aviation safety. Have the French magistrates ruled otherwise at this point? :confused:

[jcjeant]

Hi,

Has there been parallel legal investigatory actions on going by the French magistrates while the BEA is doing the technical investigation?Yes ..
The "juge d'instruction" asked to "experts" called by him (in a pool of experts who are stdby for such investigations) to make their own investigations ..
It's the judicial process ... like in any accident (cars .. buses .. trains)
These experts will present their results at the trial
The BEA will also (certainly called by the judge) present their results
Note that the parties involved can have also their own experts and they will also present their results on the trial
These can be contradictory and it is the judge to decide (it can also call other experts for cons expertise)

[roulishollandais]

jcjeant explained this french confusion very well.

Don't forget the BEA is alone to have the science, the art, the technology, for such an investigation, and the best experts, ... and the pieces of the aircraft !
And the "juge d'instruction" is waiting the final report of the BEA, like us to know what has happened !
I know one of his expert who does not know very much about the A330...

We have to say also that it is a penal trial and not a civil trial. The fault definition is not the same, and the relation whith the fault defined in the Warsawa convention is different, and the consequence of limitation of responsibility for the airline is not clear in the penal trial.

[Turbine D]

jcjeant & roulishhollandias,

Thanks to both of you for the explanations. :ok: I knew the French law was significantly different from English and US law. One thing, when you say "penal", what does that mean? Is it the same as what I would call "criminal"?

This French system is known as inquisitorial, as opposed to the adversarial system used in Common Law legal systems. In this instance, the judge who is appointed to the case is in charge of preparing the case and assessing whether it should come to court. In the US, this would be decided by a Grand Jury of citizens where the prosecution presents enough evidence to ask the Jury to indict the defendant/defendants. The Jury decides if the evidence presented is adequate to send the case to a trial.

Does the judge consider this? "There is no felony or misdemeanour in the absence of an intent to commit it.
However, the deliberate endangering of others is a misdemeanour where the law so provides.
A misdemeanour also exists, where the law so provides, in cases of recklessness, negligence, or failure to observe."

In the case as referred to in the above paragraph, natural persons who have not directly contributed to causing the damage, but who have created or contributed to create the situation which allowed the damage to happen who failed to take steps enabling it to be avoided, are criminally liable where it is shown that they have broken a duty of care or precaution laid down by statute or regulation in a manifestly deliberate manner, or have committed a specified piece of misconduct which exposed another person to a particularly serious risk of which they must have been aware. (From French Law)

It will certainly be interesting to see how this all unfolds. It is different than the Concorde case in several ways... :hmm:

[roulishollandais]

@Turbine_D

You are right, "penal" is "criminal". You will find the french law (in french) in this link.
Accueil | Legifrance - Le service public de l'accès au droit (http://www.Legifrance.com)
(legifrance.com)
and then ask "les codes en vigueur" in the "lois et règlements"
Then as "nom du code" you may choose ... want you want, for exemple
- code de l'aviation civile
- code penal
- code de procedure penale

The "juge d'instruction" is very independant in France, but as generally he don't know nothing about aviation, he has to ask for everything.
Experts will come running to explain at the manner they want.

For example in the Ste Odile crash (january 20.1992, Air Inter) the experts did not give to the "juge d'instruction" the french reglementation PANS-OPS in french (about VOR-DME approach), but the ICAO common text in english (despite this text exists in french too), which has not the force of the law, but is only a work text that the differents states member of ICAO use to build their own law.
When the french law is different, for the main rules, the state has to declare the difference, or to do "reserve" (in the sense of the international public law) (according to the Chicago convention).
In this trial, I buyed the french law and brought it to the "juge d'instruction", who said me "thanks, english is not my tea-cup, I learned latin-greek, and said me he had only the ICAO text in english...

The "Juge d'instruction" decides who may be guilty, often many persons.
At the Court, a Prosecuter, who is not independant :oh: from the Government, plaids for the french law. He has the same difficulties as the "Juge d'instruction".
For the families and surviver there is no class action. Their lawers have still very much to learn in aviation law

The greatest difference I see is that years and years are necessary in France to have a definitive Judgment.

(Law lesson is enough for today ! it is not finished).

jcjeant seems to have followed french aeronautical trials too, and he will give you other many indications !:O

[jcjeant]

Hi,

RH,
Nothing to add ... you explain it very well
Trying to follow the Concord appeal trial .. but no many publicity made about (less than the first trial ...)
I guess the trial has come about AF447 be held as previous .. that is to say in an atmosphere of suspicion and with the consequences of the defects in the French courts for the treatment of such cases
Each trial about aircraft accident in France is always source of controversial comments and critics about a system so many want to be changed ....

[roulishollandais]

Each trial about aircraft accident in France is always source of controversial comments and critics about a system so many want to be changed ....

HI,
Many lawers do not correctly use the french law in these trials, and hope too much from a criminal procedure. The Warsawa convention (convention de Varsovie modified Montreal) is a very bad system, to old and no more adapted.

But Public wonder that all the parties know another, are smiling and are very polite together... (the cockpit discipline is present).

[roulishollandais]

The star french lawyer DANIEL SOULEZ LARIVIERE who already argued such modifications during the Ste-Odile crash criminal trial,
defending the civil aviation (M. FRANTZEN who is also the husband of M.LABURTHE's daughter) has been heard yesterday by the general Prosecutor of the Cassation Court !

Me Soulez-Lariviere asks also introduction of "european law" (which one ??) in the civil part of the trial !

If such a modification is done for the AF447 criminal trial, that would mean that families requests would be throwed off, as the AF447 fell in international waters, and no french Court could judge ! (nor french nor other country's Court !).

It would be a major dissent about public and private international law !!!
http://www.rue89.com/rue89-planete/2012/04/06/maree-noire-de-lerika-toute-la-procedure-pourrait-etre-annulee-230903surprise ! 06/04/2012 à 07h31
Marée noire de l’Erika : toute la procédure pourrait être annulée

Le 24 mai, la Cour de cassation se prononcera sur les conclusions de son parquet général, qui demande l’annulation pure et simple des douze années de procédure ayant abouti à la condamnation de Total et de trois autres prévenus.
Selon Libération (http://www.liberation.fr/terre/01012400844-erika-la-justice-veut-passer-l-eponge) et Ouest France (http://www.ouest-france.fr/actu/actuDet_-Justice.-La-procedure-de-l-Erika-risque-d-etre-entierement-annulee_39382-2063471_actu.Htm), l’avis de l’avocat général et le texte du rapporteur concluent que la loi nationale n’aurait pas dû s’appliquer lors des procès du naufrage, en décembre 1999, du pétrolier qui avait souillé 400 km de côtes bretonnes avec 30 000 tonnes de fioul.
Plus de « préjudice écologique », et plus de condamnation pour l’affréteur Total, la société de certification italienne Rina, l’armateur italien Giuseppe Savarese et le gestionnaire du navire, Antonio Pollara : le naufrage ayant eu lieu en « zone économique exclusive » (ZEE), c’est-à-dire hors des eaux territoriales françaises, la loi de la France ne pouvait s’appliquer.
Cassation totale, sans nouveau procès

Le ministère public demande donc la cassation totale, sans renvoi – donc sans nouveau procès –, de l’arrêt de la cour d’appel rendu en 2009. Les quatre prévenus avaient été condamnés aux amendes maximales pour délit de pollution maritime, et à verser des indemnité pour préjudices « matériel, écologique et moral », rappelle Libération. Voilà ce qui pourrait être annulé en mai.
Comme le souligne Ouest France à propos de la décision attendue le 24 mai, « les avis des deux rapporteurs ne lient pas les conseillers de la Cour, mais il est toutefois rare que leur avis ne soit pas suivi ».
Dans Libération, plusieurs juristes cités anonymement font part de leur sidération :\:\, que résume bien cette déclaration de l’un d’eux :
« Toute une jurisprudence gênante pour les acteurs du transport :ugh:maritime sera anéantie. On se retrouvera alors sans responsable :ugh:pour l’une des plus importantes pollutions du littoral français ! »
L’avocat de Total, Me Daniel Soulez-Larivière, est satisfait :
« Toutes les questions de droit international public que nous soulevons depuis le début ont été prises en compte. »:ugh:

[ChristiaanJ]

Nice one, roulishollandais....

[VGCM66]

Back to topic.

Any chances yet to get this subtitled to English: Vol AF 447 Crash: 01/06/09: Les Raisons D'un Crash (Reconstitution) - YouTube :)

Cheers,

VGCM

[RR_NDB]

Hi,

IGh:

After UA811 [Fwd Cargo Door electrically-unlocked during flight] the manufacturer misinformed the NTSB:
"... .. Based on what Boeing has told them, investigators say four independent systems would have had to have failed for the door to open in flight...." [Wall Street Journal, 27Feb1990].
This misleading information, from that manufacturer, led to the incorrect P.C. published by NTSB in their initial AAR.
(http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-12.html#post7123052)


If in a "simple" issue (a door part) this occurred, what could happen when investigating a System (effective aircraft: System + crew) even the designers don't understand completely? AF447 was failing (a closed loop feedback System presenting failures since the beginning: 02:10:05 or even before per ACARS analysis) with the crew applying (surprising ones) inputs based on System outputs we may never know. (RHS was not recorded).

It seems the misleading (may) yet occurred. ("plane operated as designed, etc."). Public (also detected in PPRuNe) was being prepared (induced?) to: "crew error" in the end. If crew error was the cause (if), the media would emphasize (in the headlines just after Final Report publication) Why they made (errors)?

IMO they never could say plane was OK at that "investigation timing". Subtle bias?

Mac

Timing: Paris air show :}

PS

The plane was really, OK? The crew received (required) System "outputs" to proceed safely? System "helped" the crew or mislead them?

[Organfreak]

@RR_NDB & IGh:
Quote:
After UA811 [Fwd Cargo Door electrically-unlocked during flight] the manufacturer misinformed the NTSB:
"... .. Based on what Boeing has told them, investigators say four independent systems would have had to have failed for the door to open in flight...." [Wall Street Journal, 27Feb1990].
This misleading information, from that manufacturer, led to the incorrect P.C. published by NTSB in their initial AAR.

If in a simple issue (a door part) this occurred......

Sorry, even though it's OT, I can't let this stand. I don't know what Boeing told them, but this door was damaged by improper closure pre-flight, as well as having a design problem that allowed this to occur in the first place. There was nothing "simple" about it. Regardless of any deception that IGh implies, this issue was identified and understood, and properly fixed by Boeing.

--Keepin' It Real

[RR_NDB]

Hi,

Airbus it seems (based on we have) consider UAS an information (not necessarily) to be shared immediately with crew.

Instead, requires (the crew) to scan and assess (then, decide)

And, worse (IMO):

Don't (immediately) inform when UAS ends.

IMO a VERY IMPORTANT FACT to be taken into account immediately.

In order to (the crew) reestablish immediately (necessary) confidence in the System.

That (confidence) seems to be had compromised in F-GZCP last flight.

Mac

"Confidence is the greatest asset of any successful enterprise. Nothing useful survives without it" (Albert Schweitzer) (http://en.wikipedia.org/wiki/Albert_Schweitzer)

[RR_NDB]

Hi,

Organfreak:

There was nothing "simple" about it. (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-12.html#post7124223)

"Simple" compared with AF447 (complexity) (http://www.pprune.org/tech-log/481350-man-machine-interface-anomalies.html#post7124336)

I edited post including quotes around the word simple. :ok: ?

[PJ2]

Hi Organfreak;

I'm on "break", but reading occasionally. Re, "I don't know what Boeing told them, but this door was damaged by improper closure pre-flight, as well as having a design problem that allowed this to occur in the first place. There was nothing "simple" about it. Regardless of any deception that IGh implies, this issue was identified and understood, and properly fixed by Boeing.", I found the following which might clarify the issue that it was indeed an electrical actuation of a correctly-closed door:

Accident Investigations - NTSB - National Transportation Safety Board (http://www.ntsb.gov/investigations/summary/AAR9202.html)

The NTSB Report is here (http://www.ntsb.org/Wiringcargodoorlite/Additional%20Aircraft%20Accident%20Reports_files/AAR92-3.pdf).

[RR_NDB]

Hi,

PJ2:

it was indeed an electrical actuation of a correctly-closed door: (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-12.html#post7124392)

Thanks

It appeared in this case that a short circuit in the aging plane caused an uncommanded rotation of the latch cams, which forced the weak locking sectors to unlock; (http://en.wikipedia.org/wiki/United_Airlines_Flight_811)



* No tapes (Aeroperu), no wasps (Birgenair).


Kapton was being used in the (aging) B741?

[thermostat]

I find it so rude and inappropriate for people like Burt Rutan to make a statement such as one published by Bubbers 44, post #47. The airplane that has killed more people than any other is the DC10. This happens to be an American made 'plane the seemed to have been certified under the table due to the RB211/L1011 problem. It had so many flaws that it should never have been certified until those design faults were rectified. The AA crash in Chicago was blamed on the method used by AA to hang the engine. This was grossly misleading. The real problem was the fact that the loss of hydraulics (due to the loss of the departed engine) resulted in the LE slats (on that side) retracting. Why? because they were NOT locked down (as on the B727). The resultant roll caused the loss of the 'plane. What about all those cargo doors that opened in flight causing the loss of the planes?
There are many of us who fly and have flown the A320/330/340 without any serious problems. The AF447 A-330 ( a perfectly good 'plane) was flown into a CB when close to the "coffin corner." The supercooled water encountered caused the pitot tubes to ice over, resulting in the loss of many systems. Unfortunately the actions of the confused pilots resulted in an unrecognized stall and subsequent loss. How is that the fault of the manufacturer?
Did a B737 not crash going into Schiphol airport in Holland recently? Should we blame that on Airbus also?
It would be greatly appreciated if the folks who comment on these and other posts kept to the facts and not point fingers simply because the unit involved was not made in the great USofA.

[Organfreak]

@PJ2 et al,

I stand corrected on UA811 and do humbly apologize for my bad information and corrective tone. I must have seen and retained the first, wrong report. I will now (make every effort to) shut the hell up! And go back to what I am good at, which is.....uh......
:\ :ouch: :uhoh::oh::O

[lomapaseo]

This damn "we" and "them" is not productive to accident imvestigation and how it is suppose to work.

Of course it needs to be a team approach with the same objectives of preventing the next accident, rather than finding fault or protecting someones reprutation.

All investigators know this (wherever their institution), but those on the sidelines continue with their presumptions of guilt.

Sure Boeing and the NTSB investigators (add others at will) make mistakes in assumptions and investigative findings, but not from a devious plan to obfuscate, We leave that to press releases :)

It's easy to say that it would have taken 4 separate combinations of faults for such and such to happen. After all, that assumption was already verified in the product certification. The objective of the accident investigation was to find "How' and then "why" followed by the lesson learned. From my viewpoint the only criticism would be that an investigation didn't meet that objective.

[3holelover]

It would be greatly appreciated if the folks who comment on these and other posts kept to the facts and not point fingers
That's an excellent idea....
In keeping with that notion could you perhaps provide a source for your assertion that "The airplane that has killed more people than any other is the DC10."?

IOW.... I believe that to be an incorrect/non-factual statement.

[Turbine D]

Thermostat

The AA crash in Chicago was blamed on the method used by AA to hang the engine. This was grossly misleading. The real problem was the fact that the loss of hydraulics (due to the loss of the departed engine) resulted in the LE slats (on that side) retracting. Why? because they were NOT locked down (as on the B727). The resultant roll caused the loss of the 'plane.

First, indeed, the primary cause was blamed on uncommanded slat retraction on the outboard left wing. But there were many other causes and issues identified in the NTSB report.

Why did the slats retract uncommanded? Because the engine and pylon both went over the top of the wing causing hydraulic and electrical damage and failures.
Why were the slats not lock down? Because this was not a requirement at the time.
Why did both the pylon and engine go over the top of the wing? Because the pylon/engine assembly was damaged during installation at American Airline's maintenance facility.
Why was it damaged? Because the forklift being used ran out of fuel and a resulting hydraulic check valve leak permitted the assembly to drop resulting in the initiation of a large stress induced crack in the rear of the pylon.
Why was a forklift being used to remove/install both engine and pylon instead of removing/installing separate units? Because it saved time and money.

Some more details in the NTSB report you failed to mention:

1. Based on a study performed by J.H. Wiggins Company at the time, the probability of an uncommanded slat retraction during takeoff was somewhere between one in one hundred million to two chances in a billion.

2. The forklift being used was written up as defective because it drifted down under load. The engine + pylon assembly weighed over 13,000 pounds. No corrective action was taken until 3 months had elapsed from the time it was used on the assembly in question.

3. The revised Damage/Tolerance concept was not in effect at the time the DC-10 was designed and what was being used at that time did not contain newer requirements on the certification of structural design (the pylon is a structure). Had the requirement for accidental damage evaluation been in effect when the DC-10 was designed, one might expect that such consideration would have been given to accidental damage to the upper flange of the pylon aft bulkhead.

4. The certification of the DC-10 was carried out in accordance with the rules in effect at the time. The premises applied to satisfy the rules were in accordance with then accepted engineering and aeronautical knowledge and standards. However, in retrospect. the regulations may have been inadequate in that they did not require the manufacturer to account for multiple malfunctions resulting from a single failure, even though that failure was considered to be extremely improbable.

5. The uncommanded slat retraction in itself did not cause the plane to crash. Had the dc power been active, the pilots would have received warning of this condition and would have determined the roll to the left was a response to an impending stall situation based on a stall warning devise that was also not operational. They could not see the wing, slats or the missing pylon/engine from the flight deck.

IMHO, using "selective data" from a 30 year old accident to offset an equally flawed (Rutan's opinion) does little to clarify the more recent accident. Hopefully, the BEA final report on AF447 will provide not only probable cause but positive change recommendations, based on their findings, to once again improve aviation safety, just as the NTSB report did 30 years ago…

[Lyman]

In additon, I believe a power reduction (Starboard) could have saved the rollover. I think it was in the report, along with speculation that the pilots in handing over ( the F/O took off), back to Captain, the firewalled Right Rudder command was interrupted, causing Yaw left, and Left wing STALL.

TurbineD. Wasn't the Pylon Saddle crack determined to be the result of chronic incorrect hoist? As you say, the Pylon was to have been mounted first, then the engine. It was the AFT Pin join that let go, yes?

[Turbine D]

Lyman,

On takeoff, there was a crosswind from the right at 19 knots, gusting to 28 knots. It lifted off in a slight left-wing down attitude. A right-wing aileron and subsequent rudder application brought the wings to level and the plane on proper heading in the crosswind. However, with the loss of the engine and pylon structure, the aircraft cg shifted aft 2%. With all slats extended the stall speed was 124 KIAS . The asymmetric slat retracted left wing stall speed was 159 KIAS, that being the speed in which directional control could be maintained. At KISA lower than 159, a stall warning shortly after liftoff would have occurred had it been electrically powered.

In a SIM setup to duplicate the conditions of failure, thirteen pilots did 70 takeoffs and 2 landings. They had been briefed, of course, on the flight ahead of their SIM exercise. When the pilots exactly duplicated the flight controls and pitch attitudes of AA 191, the aircraft was lost. However, most pilots recognized that the start of the roll left was actually a stall and lowered the nose to gain speed, recovered and continued flight. Landings were not a problem. 80% right rudder and 70% right-wing down aileron and nose down from the 14º climb attitude was required for successful recovery.

At the altitude they were at (about 300 feet), cutting back the power on the two operating engines would have been not the thing to do, they needed more forward speed.

As for the pylon maintenance, the (to be AA 191) aircraft was in for a service bulletin to replace the aft bulkhead spherical bearing. The pylons were suppose to be removed in accordance with the procedures defined in the DC-10 Maintenance Manual (engine first, then the pylon from the wing). However, American had been experimenting with the use of a forklift to remove the engine and pylon from the wing at the same time to avoid a number of electric and hydraulic disconnects. American contacted McDonnell Douglas regarding this procedure and was advised against it due to potential damage to the wing/pylon mounts. They had performed this one step operation on several (4) foreign DC-10 they were servicing. On the aircraft in question (AA 191's), they started the removal process towards the end of a work shift and left the forklift running for the next shift to finish the removal procedure. When that crew came in they had trouble removing the forward bulkhead bearings and then notice the whole engine stand was mis-aligned. The stand was then moved forward about 12 inches to enable removal of the forward bulkhead bearings. Sadly, the whole procedure was done out of sequence from what it should have been. Because of this, the aft upper flange was damaged, not only on this aircraft, but also at other US airlines which used a similar forklift procedures on 76 engine/pylons combinations. I think fatigue cracks were found on 17 engine/pylons. Damage to the aft upper flange lead to fatigue cracks being initiated. The damage was not reported because it was thought the damage was to a low stress component and was a minor repair situation at best as defined by the FAA at that time.

[Lyman]

TD What a blessing to have you here. I think I did read losing some power on the right, in concert with lowering the nose may have been successful. I had forgotten the cross, that can't be good. Much was made of the invisibility of the leading edge, and engine, and the fact in this case losing an engine on T/O meant exactly that.

Thank you greatly for the follow up.

The a/c was badly treated, likely because knuckleheads were unquestioned. The BOSS kind of dynamic is fading away, in favor of checklists, and teams. I am not confident of out-sourcing, but sometimes.......

be well

[RR_NDB]

Well put! (http://www.pprune.org/tech-log/478681-af447-final-crew-conversation-thread-no-2-a-12.html#post7125857) :ok:

Our agenda to (always) be: Air Safety (for future, possible cases) in order to: low probability to occur again.

[bubbers44]

Each incident requires different inputs, the DC10 may have been saved by not lowering speed to V2, the AF case needed pilots who could handle UAS without pulling up into a full stall. It is difficult to train common sense into pilots from a training program, they have to learn it through experience with dealing with a lot of situations they learn to handle. That is what makes a seasoned pilot.

[bubbers44]

If the stall speeds with LED's retracted were above V2+15 I think the pilots would have lowered the nose to stay wings level. The big spread of speeds seems excessive to me. Unfortunately the low airspeed caused the DC10 to stall and crash.

[roulishollandais]

@philip2412 and jcjeant (Thread 8 AF447)

Like you, I find these sentences in the CVR are nonsenses.

So I no more trust the CVR mistraduction.

[ExSp33db1rd]

I think I did read losing some power on the right, in concert with lowering the nose may have been successful.

Interesting, flying my first light twin - many moons ago - the instructor suggested that more people had been killed due to the assymetric issues of losing an engine in take-off, then had by losing the sole engine on a single under similar circumstances, and suggested that in that event one might consider closing the throttle on the remaining good engine and land straight ahead, just like a single.

Just a thought.

[Lyman]

I heard that too, but for a twin..... With a "middle" engine, the DC10 had ample thrust, and lowering the nose with a concomitant and measured reduction in number three's thrust was a scenario that was tossed around.....

But I don't think it was meant as a prelude to a straight ahead emergency landing.

[ExSp33db1rd]

Agreed, just a comment about asymmetrical power effects.

[Lyman]

hello sir. Thanks. The DC10 has a quirky asym layout, yes? with OEI, the #2 engine, if it is running, wants to push the nose down, its mount well above the Longitudinal axis? With #1 gone, (literally), the a/c will tuck the nose and roll left. In AA's manuals, the protocol for OEI must include this tendency? If #2 is the lost one, the a/c will Pitch up, and without a yaw, more or less?

At handover, the rumor was that the rudder pedals were inconsistent, aggravating the tendency to roll left whilst the Left wing was Stalling?

cheers