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AF447

Old 9th Jun 2009, 10:19
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Grease Monkey

Apologies if this issue has been raised previously. I am interested to know if excessive rudder deflection as a result innacurate speed sensing affecting rudder limiters would cause damage just to the rudder or the complete VS. Can anyone enlighten me?
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Old 9th Jun 2009, 10:20
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In regards to the ACARS messages has anyone had a chance to preview this link?

Innovation Analysis Group

A Honeywell expert goes thru the list of AF447 ACARS messages and tells viewers what has likely happened.
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Old 9th Jun 2009, 10:24
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stef, sorry.
The Warnings as seen by the pilot on ECAM would be IR2.
The rest of the line is the reporting computors.
If you get a warning in flight, produce a PFR when you have shut down. You can then see the original warning, and the reporters. Also in the maint section will be the code generated.

The ACARS sheet you posted contains all this in one line. makes it hard to interpret if you don't see it that way usually, and you never will on the aircraft.
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Old 9th Jun 2009, 10:28
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I have a question.

As a mere engineer, I understand the problems of high altitude flight with the proximity of stall speed and overspeed.

With the known problems of pitot icing (though I have never seen it) why don't you pilots just stop flying so high when there are storms about? Would it not be easy to mandate a descent to a lower FL where the speed range is greater so you have more time to react if something goes wrong?

Yes I know it costs money, but so do crashes.
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Old 9th Jun 2009, 10:33
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Re the VS and rudder question if you Google F-GZCP there is a good picture of the actual aircraft that will show relationship of rudder to VS
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Old 9th Jun 2009, 10:34
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Robharris999

The purpose of a Rudder Travel Limiter is exactly that. As airspeed increases (computed by the air data system) the amount of rudder travel permitted is limited. This prevents excessive loading on the tail structure at high speeds.

If the Rudder Travel Limiting system were to fail, then the travel should be limited at it's last setting eg. if it failed at high speed it would limit to the high speed setting until slats were selected to 'out'.

If the system were to receive incorrect airspeed through the air data system however (due to probe icing??) the rudder travel limiter may be set to allow more travel due to the incorrect computed airspeed vs the actual airspeed. This could mean that the vertical stabilizer might receive excessive structural loading.

MLT
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Old 9th Jun 2009, 10:44
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robharris

It is not so much the rudder deflection itself as the resulting yaw from that rudder input that would be the issue. The limitation on rudder travel is not so much to limit rudder loads as yaw, which produces all sorts of secondary aerodynamic and structural loading effetcs, ONE of which would be high bending and shear loads on the fin attachment to the fuselage...


Originally Posted by Nakata?
The tail fin concerns me. it looks like a fatigue fracture across the base of the tail - a perfectly shear split in a perfect line. that is very strange.
How on earth can you say that... I don't think you'd know a fatigue failure if it landed on your bacon & eggs or sushi dish, whichever is appropriate!

Making judgements from pictures such as this on TYPE of metallurgical or composite failures is just RIDICULOUS... even from sample preparation and subsequent microscopic evaluation it still takes good consideration to say either 'Prior fatigue damage or just one-time overload'


There is some really silly speculation going on here, couched as statements not questions (which anyway would be almost as annoying)

To me, there would need to be a couple of REALLY SOLID pieces of evidence to begin down the 'fin separation' theory - even then without the FDR or VCR the EXACT cause (initiation) of this disaster would still be in doubt.

One of those would be to ASCERTAIN that the fin was found a VERY significant distance away from the bulk of the main mass components of the aircraft - e.g. 25 nm or so, AND in a direction back along the known flightpath

There would have to be other corroborating FACTS to start a good line of enquiry, which as I say, would still need the FDR to conclude the SEQUENCE and TRUE cause of events.

Last edited by HarryMann; 9th Jun 2009 at 11:05.
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Old 9th Jun 2009, 11:07
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As a computer guy (not in aero industry) I would question if we are seeing all the ACARS message.

For instance, the line with IR2 EFCS1X, IR1, IR3, would seem to have been truncated after the comma. I have no idea if the truncation is just a result of the printout layout used or if the message was truncated on transmission, but the fact remains we could be miissing some information on several of the lines.

.
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Old 9th Jun 2009, 11:17
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Hasn't the ACARS been done to death by now......

Stickyb...

would seem to have been truncated after the comma
The clue is probably in the words "libellé succint du message".

i.e. an abbreviation / brief summary / however you want to put it of the actual message. I would guess any truncations were intented and designed by a large commitee at Airbus, so I would suggest no need to start playing the X-Files theme tune.
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Old 9th Jun 2009, 11:25
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FYI, this is how an ACARS message looks when directly received from the aircraft (also an A330 in this case):

#CFB.1/FLR/FR0906091059 23333906PES 1,,,,,,,PCU(200MK)SR24A,HARD

Therefore, indeed, there may be truncation in the list circulated in this forum, whereas the BEA/Air France/Airbus certainly have access to the full picture.

Note: This ACARS message is just an example and totally unrelated to AF447!!!
But decoding of details relating to this ATA23 Communications failure welcome nonetheless

Last edited by Junkers388L; 9th Jun 2009 at 12:21.
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Old 9th Jun 2009, 11:32
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I still don't understand, why the ACARS summary was published at all by AF/Airbus. I mean, being obviously a processed and prepared form of information all it does is deepening the speculations.
Isn't it totally against SOP to publish partial data so early in the investigation?
Has anyone a good explanation?
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Old 9th Jun 2009, 11:38
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Originally Posted by Interflug
I still don't understand, why the ACARS summary was published at all by AF/Airbus. I mean, being obviously a processed and prepared form of information all it does is deepening the speculations.
Isn't it totally against SOP to publish partial data so early in the investigation?
Has anyone a good explanation?
Er, it was a leak, not "published"?

AFAIK the only official word on ACARS was that BEA (or AF?) announced that there had been 24 messages, and the overall start and end time. The detailed content is not official, however reliable we might think it is.

Edit to say that the "er" is because I'm ASSUMING that to be the answer, not to disparage the question - as it might have appeared on re-reading

Last edited by Mad (Flt) Scientist; 9th Jun 2009 at 11:49.
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Old 9th Jun 2009, 11:49
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"designed by a large commitee at Airbus"

Mixture: from what I've seen of Airbus, it doesn't work by committee. For one thing, they'd never be able to set a time when one of the nationalities wasn't out for lunch. Over there, one guy decides and the rest execute.

Last edited by Dysag; 9th Jun 2009 at 15:04.
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Old 9th Jun 2009, 12:07
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The fact is it is a lightweight component that floats
Perhaps too lightweight..theres irony in what you say...
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Old 9th Jun 2009, 12:14
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Content deleted, erroneous information. My apologies...

Cheers, y'all.

Last edited by Mudfoot; 9th Jun 2009 at 14:47. Reason: foot-in-mouth disease
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Old 9th Jun 2009, 12:38
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Originally Posted by nsxtasy
In regards to the ACARS messages has anyone had a chance to preview this link?

Innovation Analysis Group

A Honeywell expert goes thru the list of AF447 ACARS messages and tells viewers what has likely happened.

This "Expert" is suspect in my eyes because he does not mention the "Cabin Vertical Rate" message at any time. He implies that the 02:14z message is just an advisory about the ACARS itself.

It appears he was not given all the information that is available. If not, where does all the talk of "Cabin Vertical Rate" originate?
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Old 9th Jun 2009, 12:39
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Originally Posted by nsxtasy
In regards to the ACARS messages has anyone had a chance to preview this link?

Innovation Analysis Group

A Honeywell expert goes thru the list of AF447 ACARS messages and tells viewers what has likely happened.
I just had a listen, for a laugh, and switched off about halfway through.

Interviewer and "expert" seemed to get completely confused about what alternate law was, and then appeared to conclude that the mesage about reversion to alternate law must indicate failure in the flight control computers.

Even with my limited and datred knowledge of how airbuses are put together, it is clear that there is far better, clearer, and more credible analysis of the ACARS data on this thread.
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Old 9th Jun 2009, 12:44
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Originally Posted by Rananim
Perhaps too lightweight..theres irony in what you say...
Not sure what you are implying, unless you don't understand that there is not necessarily a correlation in engineering (particularly in aviation) between weight and strength.
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Old 9th Jun 2009, 12:51
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Swedish Steve

I have a question.

As a mere engineer, I understand the problems of high altitude flight with the proximity of stall speed and overspeed.

With the known problems of pitot icing (though I have never seen it) why don't you pilots just stop flying so high when there are storms about? Would it not be easy to mandate a descent to a lower FL where the speed range is greater so you have more time to react if something goes wrong?

Yes I know it costs money, but so do crashes.

Steve,
the answer to your question is that the preferred method of CB avoidance is lateral rather than vertical. Best of all one avoids a whole system but when this is not possible (as is frequently the case) the method is to find a route between individual cells, not penetrate any of the cells themselves. Often this is easier when higher because the gaps between the cells
are greater. Also many CBs do not reach cruise altitude. Sometimes lower altitude can involve worse weather.

My own experience is that operating at normal optimum altitudes is satisfactory provided that adequate lateral separation from CB can be achieved. Careful monitoring and readiness to intervene on speed and thrust are part of the process.

The issue of probe icing is one I have not encountered, nor I would guess, have most readers,and it would appear to be type specific to A330/340. It would also appear, judging from the reports from previous contributors, to occur in specific circumstances, notably layer cloud around the CB e.g.the anvil, even though the CB itself has been avoided.

It is of course true to say that if airspeed indications are lost, lower altitude does give a greater range of speed availability, therefore the crew's task is easier. In all cases judgements have to be made according to the circumstances.
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Old 9th Jun 2009, 13:04
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To swedish steve:


A pilot always try to fly at OPTIMUM altitude, which is the altitude where you have the best kilometric endurance and you have a good margin to the low and high stall speed.

In Europe is always quite easy to fly at that altitude because, even if there are many planes flying around, the separation in height between planes are reduced (1000 feet between converging flights). The longitudinal and lateral separation between planes is also reduced because Air Traffic Controllers use the radar.

Across the Atlantic Ocean the longitudinal separations are very big (planes that follow the same route is 10 minutes of separation, i.e.80 nautical miles) and the vertical separation is double (2000 feet between converging flights).

So, at the start of Atlantic crossing if the pilot take the altitude which is not the optimum but nearly the maximum at that moment, is very happy because if there is bad weather in front of him, he will have more chance to overfly it (anyway the pilot, in the evaluation of the chosen flight level always have to think about ahead forecast turbulence).

If there is bad weather, the pilot has to use the weather radar, scans the sky in order to understand if he is able to overfly it or he has to change route in order to circumnavigate thunderstorm cells.

The job of the pilot is to evaluate and mainly take the decisions which are not the ideal but a compromise.

Anyway if the plane enters in a permissible cloud, pilot knows that the plane has a protection against ice built-up using airworthiness antice devices.


After this accident I know that Airbus had some troubles concerning the anticing of the pitots. If there is ice build-up in the pitot the airspeed indicated to the pilot (the speed that show the margin to the low and high stall speed) is unreliable.
See also this link
http://alphasite.airfrance.com/s01/?L=2

Anyway, there is a procedure called: flying with “UNRELIABLE SPEED INDICATION”.
In this procedure the pilot has to fly the plane with precalculated attitude showed to the PFD’s (primary flight displays through IR1, IR2, IR3 and ISIS) related to the phase of flight and applied the correct power to the engines in order to fly predetermined speed.

This emergency procedure is very difficult but I think that the Air France crew was able and well trained to follow, to manage and apply it.

This is the time to do again the question:BUT DID THE PILOTS HAVE THE ATTITUDE INDICATIONS ON PFD’s?

Answering this question will also answer the other: why the rudder could be detached? Without airspeed they didn’t have the Rudder Travel Limiter.
And without attitude indication, the flight could be so unstabilized that if not using the rudder with care the rudder could be damaged and detached
loosing, may be, the pressurization.


Now Swedish Steve, I ask you again to explain me better what you answer me using simple and comprehensive English (sorry, English is not my native language)


I ask again to other professionist people to clarify the line written in the Acars messages: did the AF447 flight also have IR’s failure?

Thanks
Stef
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