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AF 447 Thread No. 5

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AF 447 Thread No. 5

Old 28th Jul 2011, 14:42
  #821 (permalink)  
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Hello Bearfoil,

Yeah, we loose radomes by the dozen, they come cheap these days.

Icing of probes, however, does not happen that often, or does it.
The following quote from BEA interim report does not describe a large number of radome loss events.

As of 3 November 2009, Airbus had identified thirty-two events that had
occurred between 12 November 2003 and 1st June 2009(18). According to Airbus
these events are attributable to the possible destruction of at least two Pitot
probes by ice. Eleven of these events occurred in 2008 and ten during the first
five months of 2009. (Note by EMIT: destruction should be read as obstruction)
Twenty-six of these incidents occurred on aircraft fitted with Thales C16195AA
probes, two on aircraft with Thales C16195BA probes and one on an airplane
equipped with Goodrich 0851HL probes.
As of 1st June 2009 Air France had identified nine events that might meet
the above-mentioned criteria. After the F-GZCP accident the airline started a
targeted analysis of recorded parameters and identified six additional events
that occurred in 2008.
In addition, a foreign operator began a targeted analysis of recorded flight
parameters recorded after June 2006 on its A330 fleet. As of 18 November
2009 it had identified fourteen events. Only four of them had been detected
and reported by the crews to their airline.
Further, Airbus identified four events that have occurred since 1st June 2009.
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Old 28th Jul 2011, 14:46
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Less rare than simultaneous (including rate) obstruction of three Pitot Heads?

Fair question. However, I am basing my question on the FCOM. It's in there.

We are dealing here with most likely an extremely rare confluence of bad things. Yet I witness an unusual presence of "stuckness" and "dismissiveness". I'm not actually taking sides 3hl. What I seek to do is express my thoughts regarding possibilities.

Here, your statement is best directed at Airbus/AirFrance. Again, it's in the FCOM as a cause of duff speeds.
Old 28th Jul 2011, 14:51
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Until the data is in, what needs to be acknowledged are all the possibilities, regardless of probability. I am having a hard time trying to convince people that the time to defend a particular opinion is after all of them have been entertained, and the data is available.

If it is too soon to state cause, it is definitely too soon to reject even one, at least conclusively
Old 28th Jul 2011, 15:20
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Originally Posted by airtren
The picture is informative. Would you have a clue, what training center is that?
A picture is informative, or will illustrate an article, because it is showing something related (like a flight simulator) not because it was taken specifically for the relevant press article. This one is from news archives or possibly related. It is more likely from news picture archives as it seems taken during an aeronautical convention.
Consequently, I'm pretty sure that this picture was not related to any official (informed) replays of the recorders (Airbus, Air France or BEA).
Now, you may wish it was.

Last edited by takata; 28th Jul 2011 at 16:32.
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Old 28th Jul 2011, 15:35
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Audible ice shedding from pitots? Nope... BUT...

As one who spends his life creating sound simulations for all classes of aircraft (at the highest fidelity Level D for commercial aircraft and equivalently for military sims), I find it almost impossible to believe that anyone could believe such ice shedding would be audible - the location of the pitot tubes themselves and, above all else, the small quantity of ice involved (due to the physical size of the tube) makes this claim extremely unlikely.

As it stands, for the many simulators I have been involved in, ice shedding from propellers, with the ice being flung from the blades and hitting the cabin sides, is about the only sound cue related to icing that I believe might be audible to any cockpit crew.

Totally accept the thrust of your point, but think that there is another source of ice-related sounds.

I dimly remember claims made in the original AF447 thread of hearing ice on the windscreen. Cannot find those posts, but this later one captures the idea.
I have seen the TAT anomaly (TAT probe icing due to high ice crystal content) when flying through "light green" radar returns in the neighbourhood of CB's, in other words, while avoiding CB's. Turbulence then was only light, occasionally moderate, nothing out of the ordinary. Saint Elmo's and a sound like rain on the windscreen were also present.

To summarise:
a) The claim about hearing ice shedding from the pitots sounds like b/s. [Or a journalistic misunderstanding.]
b) Hearing ice shedding from elsewhere is highly unlikely. [You are the expert.]
c) In de-briefings several pilots have reported hearing something (later identified as ice-crystals) hitting the windscreen prior to a high-altitude "anomaly". So it may well have happened on AF447. [IIRC it is often reported as quite a distinctive sound.]
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Old 28th Jul 2011, 15:45
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Originally Posted by mm43
Following the AP/ATHR disconnect, the aircraft entered a "zoom climb". The Stall Warning sounded briefly during the pitch up manuever and some ND inputs were made and attitude was reduced to 7°NU but the AoA was still rising and the SW sounded again. Further NU inputs prevented any normal stall recovery and once the CAS became less than 60KTS the SW stopped.
- this is NOT what the May BEA report said - perhaps you are 'clairvoyant' regarding the 28 July report? The stall warnings sounded BEFORE the climb.
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Old 28th Jul 2011, 15:52
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airc, THe "STALLWARNING" sounded briefly at PF first input, NURL.

Could that be consistent with a cruise speed input of NOSE UP? If so, would the PF immediately reduce PITCH? If so, it may not be associated with the climb at all?
Old 28th Jul 2011, 16:00
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No idea. The way the (English) report is written (for what it is worth ) there were at least 11 seconds before the a/c began its climb. I was going to sit quietly and await a better report tomorrow but I got woken up by people inventing stuff again
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Old 28th Jul 2011, 16:12
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france info
They won't tell if they got access to the data, but listening to the interview, it is possible they actually did :

"The pilots didn't understand what was going on, we clearly hear it in the registered conversations in the flight deck, there is no panic."

Also a desire to 'protect' the Airbus technology to the public eyes ... ?

"The airplane did not stall, il s'est enfoncé (it has gone deep ?), thanks to the protections."
"The protections have been effective but not understood by the pilots."
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Old 28th Jul 2011, 16:18
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From BEA. At 02:10:16: "So, we've lost the speeds.......ALTERNATE LAW". (PNF). In between the STALL WARNING, and the (PNF) voice recording, there is no official mention of "CLIMB" (or STALLWARNING). Likewise, it would seem a blatant omission by BEA, had the a/c begun the climb, or had experienced notable problems. (Other than UAS).

We may know soon, or not. I expect somewhat less than full disclosure.
Old 28th Jul 2011, 16:22
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Some people are still entertaining the idea that those flight data, CV recorders, are hiding critical informations in order to state the truth, informations that will point to the only one cause of this crash, the only relevant thing they could ever be able to believe as being not a cover up for the manufacturer's wrong doings.

My own feelings is that we won't get more clues tomorrow about this single cause than what is already known fairly exactly today (of course, if one bother to put all the facts together by stopping to make up what he wishes), because nothing more than that was recorded, nothing that could direclty explain PF's actions.

One could replay the scenario many thousands times, it won't help to understand the cause without discarding this way of thinking. Pilot's brain is not recorded. All we are going to learn is more details about their confusion concerning the situation they were facing. It is quite obvious that they never acknowledged the stall situation, neither that they would have tried to recover from it if the stall was not acknowledged at the first place.

That's, in my opinion, the issue the industry would have to deal with in the future. As there will be no single and very easy answer to: what to do then? because it is a very complex one, it's not going to be fixed any time soon.
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Old 28th Jul 2011, 16:26
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What is it about "the Pilot's Brain" that is of interest to the a/c? This a/c is protected, flies safely, won't STALL, (at least on its own....)

A thinking Pilot, one 'thinks', is not necessary to the Airbus. One who can memorize, and leave things alone? Now you're talking! Thinking is optional, and more expensive!
Old 28th Jul 2011, 17:25
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Simultaneous Inputs

According to the 27 May 2011 BEA update:

"At 2 h 13 min 32, the PF said "we’re going to arrive at level one hundred". About fifteen seconds later, simultaneous inputs by both pilots on the sidesticks were recorded and the PF said "go ahead you have the controls"."

I am interested in the "simultaneous" inputs. Were these consistent, or were they conflicting NU and ND commands?
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Old 28th Jul 2011, 17:34
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CVR sounds

Firstly - if the assertion was the sound was replicated from the CVR mic recording it must be recognized that the mic is optimized for voice bandwidth. I commented on this previously, but don't have time to search for the post. But the CVR cockpit mic frequency range is limited - I want to say to around 6kHz....?

Secondly transient noises of short duration are very hard to isolate and make any sense of unless very loud. Ice shedding from the pitots would not do this.

Ice crystals hitting the windshield - yes, I can see that being audible, certainly.

Radome damage/departure/etc - something of this nature would certainly lead to a noticeable change in the aerodynamic impact noise footprint.

Both ice crystal noise and radome damage would be heard over the CVR. Ice-shedding not so, in my professional opinion.
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Old 28th Jul 2011, 17:42
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Takata, I fully concur with your remarks; tomorrow is not going to "solve" this. Expectations that it will are bound to be disappointed because that isn't the way accident investigation works. Reification of this or that pet theory will not be found in this update.


Thanks for your comments and question.

Machinbird made a good point a while back in pointing out to me that "doing nothing" isn't the exact response and of course he was right. By the phrase, I was assuming a great deal on the part of the reader. What I meant was, other than maintaining level flight as best one can using pitch and manual thrust settings, (which would be those which existed just prior to the failure), one "does nothing" in terms of climbing/turning/descending etc. Above all else, one stabilizes the aircraft in level flight. There is absolutely NO reason to change anything during a UAS event.

Now, your question is a good one, made even more important by the extensive and wonderfully-intelligent discussions by many here who do know their stuff, concerning the behaviour of the A330 in Normal, Alternates 1 & 2 and Direct Laws, including simulation of same. I have learned both here and in private communications more about the airplane I flew for many years than I ever knew during my time on the airplane. (There is a notion there that I would like to explore, but time, space and a low desire to do so all call for a break at the moment). The airplane flies and works brilliantly; what is being explored here, as takata notes, are the extreme boundaries of flight in a heavy transport, and at the boundaries, (note: not the limits, but the boundaries), of design and engineering. That is why this accident is extremely complex, involving the above and a healthy dose of human factors, ergonomics, warning systems, and so on.

I assumed the airplane was just about as easy to fly in Alternate 1 and 2 and Direct Laws as it was in Normal. I have done this in the simulator many times and I think it is safe to assume that simulator fidelity is high in these regimes, (vice low fidelity in the stall or upset). It was never a problem flying the airplane thus, nor was it like "balancing oneself on the top of a greased flagpole". I understand the roll direct is brisk, but at altitude, one is always gentle and smooth with a heavy machine in thin air.

In direct response to your question, I think one can manually fly this aircraft at high altitude providing one handles it thus. I have learned through discussions on the reduced damping effects of high altitude flight and the physics of mass and trajectory of a heavy machine as well as the notions underpinning an understanding of PIO, that maintaining level pitch and bank attitudes in the circumstances you describe, would be challenging and perhaps even very demanding depending upon the second-by-second series of sidestick inputs over a short period of time. I think one can lose one's SA if one induces PIO, especially in Roll Direct, a factor which I had not truly been aware of until recently. It will be interesting to see how the BEA deals with this notion and phenomenon, if at all.

These points are why this accident will not be close to resolution and understanding in tomorrow's release by the BEA.

Marshal McLuhan once observed, "In the vortex of process, there are no fixed points of view; understanding is never a point of view." I think that may describe an approach to this report and the final report which will yield the best comprehension of what occurred. If one as a point of view, the report will be disappointing and unfulfilling.

I hope this helps airtren; I am enjoying your contributions and am pleased you entered the conversation.
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Old 28th Jul 2011, 17:43
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Thanks for the pointer CONF_iture

From listening to the interview, among the two interviewed pilots comments that I would mention, are references to the shortcomings of the "a/c to pilot information interface", the reviewing of procedures for such situations, and a dialog between Air France and other airline companies, on one side, and Airbus on the other, in that regard which is just at the beginning..

Originally Posted by CONF iture
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Old 28th Jul 2011, 18:06
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Bearfoil, for once I'll inject an icon:

Of course, the FCOM mentions the possibility of a radome getting damaged or lost. Such an event would greatly influence airflow around the nose of the aircraft and would thus adversely influence the pressure measurements as taken by the various pressure sensors mounted around the nose. But FCOM mentions a zillion possible failures.
The BEA Interim Report number 1 mentioned an estimate of aircraft state at impact, based exclusively on damage patterns found on floating debris - almost 2 years later, the recorders proved that the original estimate was remarkably accurate.
Part of the original estimate, was parts of the radome found at sea.

Quote from Interim report 1:
Observations of the tail fin and on the parts from the passenger (galley, toilet door, crew rest module) showed that the airplane had likely struck the surface of the water in a straight line, with a high rate vertical acceleration.

Quote from Interim report 2:
From these observations it can be deduced that:
* The aircraft was probably intact on impact.
* The aircraft struck the surface of the water with a positive attitude, a low
bank and a high rate of descent.
* There was no depressurisation.

I think you can TRUST the BEA that, had there been grounds to suspect that the radome was lost, they would have mentioned it in their reports so far.

To the rest:
Whether it is conceivable that pilots somehow make an error with regards to stall reactions? Yes, it happens, even in good old fashioned Boeings!
Heavy take-off, during flap retraction an upgust underneath a big Cu (note: I do not state Cb), as margin at that moment is very small, it triggers a stick shaker.
PF reaction? Pull up the nose slightly. PNF intervenes, so nose is lowered, a/c continues flight uneventfully.
Query by the PNF (the commander) about the reaction of the PF - well, it pointed to a sort of mix up of the text from GPWS/Windshear procedures, that speak of pulling up, with the stick shaker as upper limit of that action. So, somehow, in the PF's mind, there had formed a connention of "stick shaker, pull up".
More strange reactions in pilots minds: read up in an old Boeing magazine about the 767 that took off from Isla Margarita (1994 or 1995) and turned directly towards the 3.300 ft high mountain on the island. The GPWS calls caused a PF reaction of increasing pitch by 1 degree. Only after the audible impact with a TV antenna on the mountain top, did he progress into a proper GPWS reaction.

Once again: 15 degrees nose up, clearly visible on those beautiful PFD's, is very, very unusual attitude in a transport aircraft around FL350. All recorded pilot actions should have been very much nose down. All sorts of failure flags on the PFD and messages on ECAM should not have distracted the crew from the still perfect attitude indications.
And, as said by many before, the mighty "push" of TOGA at FL350 is nothing more than CLB thrust at that altitude, and as such a disappointingly small amount above normal cruise thrust. Certainly not a big handful of pitch up moment.
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Old 28th Jul 2011, 18:42
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Have a look at the fractures evident on the radome after surface retrieval.

Note the linear fracture from the outer perimeter in toward the center of the piece. Can you describe the likely mode of failure of this two phase material with any linearity remaining? I can. Are you at all interested?
Old 28th Jul 2011, 19:28
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Follow up


Behind the radome is the WX Radar. If the radome gets lost, that radar is not gonna be able to sweep its antenna back and forth any more, exposed to a 480 kts airflow. That is certainly gonna trigger a couple of messages that would have been in the ACARS data stream.
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Old 28th Jul 2011, 19:29
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Radome Loss In Flight

CVR should go from relatively quiet to noisy as hell.

I doubt that we will hear the CVR for our confirmation, So I will just wait for the BEA to tells us what's significant on the CVR
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