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Old 25th Apr 2011, 17:06   #101 (permalink)
 
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Fronl1ne,

The RAT can be deployed automatically if hydraulic pressure fails. That is achieved by the total 'system' sensing a total loss of hydraulic pressure or a loss of all engine power.

In the case of iced-up pitots, the system would not 'know' that ice was causing erroneous readings. That is to say, the aircraft systems would need to be 'told' that the sensed 'q' was not to be trusted, because of ice.

But how could you tell if ice was causing the data to be unreliable? The systems would simply take the 'q' reading as correct, even if it was not.

It's difficult to imagine, therefore, how an automatically deployed standby pitot system would operate.

Maybe the engineers on this thread could expand on this.
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Old 25th Apr 2011, 17:16   #102 (permalink)
 
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Bearfoil

Quote:
so perhaps another look at the conclusion that recovered victims were necessarily unbelted may be needed
This has been a question I have had since this thread began. The crew had to be aware of what lie ahead of them, visual or electronically, and at that time in flight, historical experience of flying this area, common proceedure would dictate seat belts be on. Yet, from what precious little evidence we have, the question remains unanswered, on or off. Information regarding crew station(s) that we have seen can make a valid argument that they were not on, and that the cabin staff may have been up and about when the event occured. Body recovery however does not necessarily mean that these individuals were not belted in at impact. Paxs leave seats on impact even when belted so I do not believe a defendable conclusion can be drawn from this. Further, reportedly paxs are observed still in their seat at the accident site.
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Old 25th Apr 2011, 17:21   #103 (permalink)
 
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WW, so what do you think about post #38 ?
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Old 25th Apr 2011, 18:17   #104 (permalink)
 
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Quote:
Originally Posted by Svarin View Post
henra wrote :

Why ? Maybe because there was no first upset... Just an unpleasant but otherwise normally manageable UAS... When it is over, back to normal ops, get A/P back on. No need to tell the cabin crew.
If it weren't for the location where the wreckage supposedly was found and the time of the Cabin Vertical Speed advisory in relation to this ACARS message I would absoultely agree with your scenario. Has some merit to it.
However, they would have travelled a siginificant distance in these 3 minutes until 2:13:XX namely between 20 and 25nm. After that they would have to shed 35000ft in a short time and return to where they came from and arrive there at little forward speed. Would be difficult to align with the 2:15:15 as likely latest crash time and the time of the cabin VS message marking probably the passing through 8000ft. This message is transferred directly subsequent to the AFS warning.
Still a possible scenario though..

Looking at the timing of the ACARS Messages again I'm not really sure any more if we are on the right track!?
The failed FPV activation is stamped 211, NAV ADR Disagree is stamped 212 which could imply that at 212 things were not back to normal.
That would not leave much time to re-connect the AP and to lose it completely.
However I have to agree either this sequence could indicate a seemingly 'benign' environment where they simply try to get it back to normal ASAP after a seemingly non-dramatic event or it could be a sign of desperation or we are reading something into this message which is simply not there.

The last point makes me curious if no one on this planet can really elaborate/explain what could cause these ACARS messages / what is the logic behind / what they exactly mean or those who know keep it as a secret
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Old 25th Apr 2011, 18:41   #105 (permalink)
 
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Position Altitude and French report

It just occurred to me, have anyone in all the AF447 threads considered the possibility that the last ACARS position report was not at FL350? I read the ACARS sequence and it just contains lat/lon coordinates, no altitude information (nor track, heading, speed, etc.)

The aircraft could be well below that altitude, and AFAIK, at the LKP report, they could be in another heading, is that correct?

Now, maybe my math (and distances information) is wrong here, but from the crew position report at INTOL and their estimates to SALPU and ORARO, the groundspeed varies considerably to the LKP.

But, considering their last estimate 02:00 UTC at ORARO and the LKP at 02:10:34 UTC, their groundspeed was ~273 knots. Does that compute?

INTOL - SALPU (122nm - 13.25 mins elapsed): ~552 kts

SALPU - ORARO (122nm - 12 mins elapsed): ~610 kts

ORARO - LKP (~48.18nm - 10.57 mins elapsed): ~273.6 kts

Isn't it possible that at the position report the aircraft was turning back to Brazil or something different than flying the planned route, at a different altitude and speed?

About Svarin's observation, maybe something got lost from the french to english translation. Anyone here good in french?

The original french report explanation about the AFS occurrence:

Quote:
Ce message ne peut pas être la trace d’un reset, ce qui exclut notamment la possibilité d’un arrêt manuel. Ce message pourrait être la conséquence d’une incohérence entre les deux chaînes internes du FMGEC (COM et MON). Une telle incohérence pourrait elle-même être la conséquence de valeurs erratiques des paramètres d’entrée. Quoi qu’il en soit, les seules conséquences d’un tel message ne peuvent être que le désengagement d’automatismes dont les messages cockpit effect associés ont déjà été émis à 2 h 10.
Le caractère « INTERMITTENT » signifie que l’anomalie a duré moins de 2,5 secondes.
I think Svarin made a point that the crew was alive, alert and well in the flight deck, by trying to reengage the autopilot.

However, for an automatic commanded pitch down (or up maybe), we have seen that the A330 doesn't need a connected Autopilot to command a abrupt pitchdown - read QF72 accident investigation..

Last edited by Pugachev Cobra; 25th Apr 2011 at 18:49. Reason: Added QF72 info
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Old 25th Apr 2011, 18:52   #106 (permalink)
 
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Cool

Hi,

One from neighbors

Google Vertaling

Original page:
Le « décrochage » d
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Old 25th Apr 2011, 18:55   #107 (permalink)
 
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A. I think we're probably reading more into it than there is. We are humans, and we've evolved to see more patterns than exist in reality (better to see a non-existent bear and live than not to see one that is there).
B. The logic for ACARS messages is published, we're just trying to use them for something they were never intended to do. They're there to report aircraft position, status and issues that may require maintenance. They're not there to record flight data.
C. There's no secret, but I wonder how much experience there is with A330s reporting exactly this set of ACARS messages. Again, we're only getting a few indications here.

You can't really rule stuff out here. For example, we can't say "they didn't fly into a huge cell, because if they did, they would have seated the FAs and everything would have been secured." We can't say that, because our weather data suggests exactly that, and if they had seen what our weather data shows, they would have gone more than a little bit off-track to avoid it, as the other aircraft did.
If the evidence shows that they weren't belted in, all that tells us is that the flight crew were not expecting turbulence, which is a state consistent with flying through a huge cell (that is, not being aware of it; another state consistent with flying through a huge cell would be being aware of it, but underestimating its intensity).
In any case, what about the other flights that were threading the thunderheads in the ITCZ that evening? Did they secure the cabin?
We can't argue that 39 flights in an A332 implies familiarity with the wx radar if there's formal training or evaluation on using it.
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Old 25th Apr 2011, 19:06   #108 (permalink)
 
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e message ne peut pas être la trace d’un reset, ce qui exclut notamment la possibilité d’un arrêt manuel. Ce message pourrait être la conséquence d’une incohérence entre les deux chaînes internes du FMGEC (COM et MON). Une telle incohérence pourrait elle-même être la conséquence de valeurs erratiques des paramètres d’entrée. Quoi qu’il en soit, les seules conséquences d’un tel message ne peuvent être que le désengagement d’automatismes dont les messages cockpit effect associés ont déjà été émis à 2 h 10.
Le caractère « INTERMITTENT » signifie que l’anomalie a duré moins de 2,5 secondes.

Translation: This message cannot be due to a reset, which excludes in particular the possibility that it was manually shut off. This message could be due to a disagreement between the two internal channels of the FMGEC (COM AND MON). Such a disagree could, in turn, be the consequence of erratic input values.
Whatever the case may be, the only possible consequences of such a message can only be the disengagement of automation whose associated cockpit effect messages were already transmitted at 0210.
"Intermittent" means that the anomaly lasted less than 2.5 seconds.

Well, to be precise, the message doesn't have consequences, rather whatever sent the message would have also instructed the A/P to disengage if it were engaged. That's "only possible": they are not making any statement on the A/P status.
They are also implying that if the flight crew "reset" the FMGEC by turning it off and on again, there would be a different set of messages (otherwise, I cannot see how they can claim that it "excludes the possibility" -- it only excludes the possibility that this message was generated by a reset, not that a reset occurred previously or after).

I will now join -gums- in shutting up (but not in his insight, alas).
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Old 25th Apr 2011, 19:21   #109 (permalink)
 
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Pugachev Cobra;

The ORARO estimate of 0200 is wrong, and it should have been 0204. It was possibly misheard due to accent/static.

The 02:10:34 AOC report will have left the a/c at 02:10:30. When it was generated is not known, but AOC reports have precedence over other ACARS messages and the BEA have stated its nominal time as 0210.

The preceding positions are listed below, and you will note that GS was fairly constant at around 467KTS.

ACARS AOC Positions
0210: 02°58'47"N 30°35'23"W
0200: 01°48'00"N 31°08'59"W
0150: 00°38'23"N 31°45'36"W
0140: 00°29'23"S 32°22'11"W
0130: 01°38'59"S 32°58'47"W
0120: 02°49'11"S 33°36'35"W
0110: 04°01'11"S 34°14'24"W
0100: 05°12'35"S 34°52'11"W

The altitude at 0210 when the flight law reverted to Alternate Law was FL350 at 272 +/- 2 KCAS as recorded by the Rudder Travel Limiter Unit (RTLU) which set the maximum rudder travel to +/-7.9° based on the last valid air data.



EDIT :: As kindly pointed out by HazelNuts39 in post #114 below, there are other permutations that will provide the same CAS but with different levels and Mach numbers.

Last edited by mm43; 22nd May 2011 at 03:43. Reason: added correct graphic
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Old 25th Apr 2011, 19:37   #110 (permalink)
 
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Quote:
Originally Posted by Pugachev Cobra View Post
About Svarin's observation, maybe something got lost from the french to english translation. Anyone here good in french?
The original french report explanation about the AFS occurrence: [etc.]
It's not my mother tongue, but I've lived and worked here in France long enough (35 years in aviation, automatic flight controls, etc.) to be able to do a translation.
To me the translation DingerX quotes is sufficiently accurate to all normal extent and purposes. If there is anything you query in particular, just ask.

Quote:
Originally Posted by DingerX
Well, to be precise, the message doesn't have consequences....
Quite.
But the French in the report is fairly convoluted (in the best French formal report-writing style), and it's easy to read too much into it.
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Old 25th Apr 2011, 20:31   #111 (permalink)
 
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Hi,

Just one remark about the "galley catering-cannister stowage unit" picture that I posted (#3787). This picture have been posted on a now apparently dead French forum (Eurocockpit). It was said there the latches positions were not conclusive. And perhaps, the box on the top (which position was very astonishing for me if there was a high sea) had been put there when its recovery happened.

And one question: I think I have understood (imho!) that in "normal" flight with AP engaged, moving the thrust levers or the stick (right words?) do get the autopilot off. And then, you have to manually re-engage it to get it again. But what happen if nobody move either of them after automatic disengagement? Is the AP going back automaticly if the a/c "think" the speed indications are right back?

Sorry, if this has been answered before (and thanks to all this brainstorming by knowledgeable people).
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Old 25th Apr 2011, 20:51   #112 (permalink)
 
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ChristiaanJ;
Quote:
But the French in the report is fairly convoluted (in the best French formal report-writing style), and it's easy to read too much into it.
An interesting point. With your knowledge of French "aviation speak", do you think that the BEA's English translation of their preliminary reports is generally "on the button" in relation to English "aviation speak"?
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Old 25th Apr 2011, 20:54   #113 (permalink)
 
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mm43;

From the BEA text on the RTLU:
Quote:
As an example, at FL350, this travel is obtained for Mach 0.8 +/- 0.004, corresponding to a CAS of 272 +/- 2 kt.
As another example, at FL362, Mach 0.82, 272 kCAS?
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Old 25th Apr 2011, 20:58   #114 (permalink)
 
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HN39;

Thanks for reminding me! Very true.
I have previously posted the same comment.
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Old 25th Apr 2011, 21:00   #115 (permalink)
 
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I was looking at some of the other incidents mentioned in the second interim AF447 report when I noticed this in the TAM report.

http://dms.ntsb.gov/aviation/Acciden...2011120000.pdf

"This incident report has been combined with NTSB Incident Report DCA09IA064.
Updated on Mar 29 2011 6:09PM"


But the Northwest report (DCA09IA064) looks unchanged...

http://dms.ntsb.gov/aviation/Acciden...2011120000.pdf

Anyone know what is up?
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Old 25th Apr 2011, 21:03   #116 (permalink)


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Wave Height

Considering the velocities typically involved in air accidents over water, wave height has little to do with airframe conditions through impact. After the preliminary survey of the fuselage the investigators have data that shows almost no horizontal component pre- sea surface contact.
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Old 25th Apr 2011, 21:09   #117 (permalink)
 
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From post #79

'This means the a/c likely did not crash right after end of ACARS sequence. '

Could someone explain this please ???
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Old 25th Apr 2011, 21:43   #118 (permalink)
 
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Quote:
Originally Posted by mm43 View Post
ChristiaanJ;
An interesting point. With your knowledge of French "aviation speak", do you think that the BEA's English translation of their preliminary reports is generally "on the button" in relation to English "aviation speak"?
mm43, rather than 'wading back' through the topic, could you give me a link to the latest BAE report, and I'll go back to the site, look at the English and give you my assessment (for what it's worth).
From what I remember, it's definitely better than Google Translate (which BTW has remarkably improved over the last year or so, and is usually adequate for a first look, especially if you have some knowledge of the source language), but not always done by English-mother-tongue translators.
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Old 25th Apr 2011, 21:45   #119 (permalink)
 
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Link to reports:

FLIGHT AF 447
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Old 25th Apr 2011, 21:55   #120 (permalink)
 
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RR - I guess I'll kick in another comment (aside from being double qualified for QCWA). The aircraft pilots are pilots first and radio operators second. With SelCall I am not sure they listen to the radio enough to get "The Ear" that helps drag stuff out of noise.

On the other paw, ACARS is digital. It would have a pretty good chance of getting through mere static. And I note, everybody who seems to be wx aware of that particular evening and location suggests there was little or no lightning involved in the storm system. So "What QRN?"
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