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AF447

Old 10th Jun 2009, 17:15
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TCAS, the Canary in the Mine?

Of course we don't really care that the TCAS failed with no other traffic within range. What I am pursuing is what failure triggered its fault report. I found the below list on the Italian page. Can you point me to a better list?

The first four items would follow from iced pitot tubes, where there would be airspeed disagree. Airspeed anomalies should not affect altitude computation enough to cause the digital Altitude word to go Fail Warn out of the ADIRU. And airspeed will not affect pitch and roll outputs.

The TCAS depends on Altitude, not airspeed.

The IR faults are down the list, obviously occurring some time after the TCAS Fail. Moreover, if 447 had Collins TCAS, IR Fail would be meaningless anyhow, as the Collins doesn't use pitch and roll inputs. Honeywell TCAS use those inputs, but might not fail itself if those inputs are failed.

ATA 27.91 F/CTL ALTN LAW
ATA 22.83 FLAG ON CAPT PFD
ATA 22.83 FLAG ON F/O PFD
ATA 22.30 AUTO FLT A/THR OFF

ATA 34.43 NAV TCAS FAULT

ATA 22.83 FLAG ON CAPT PFD
ATA 22.83 FLAG ON F/O PFD
ATA 27.23 F/CTL RUD TRV LIM FAULT (Brutta cosa)
ATA 34.11 EFCS2 EFCS1 AFS FAULT
ATA 27.93 EFCS1, EFCS2X FAULT
ATA 22.83 FLAG ON CAPT PFD
ATA 22.83 FLAG ON F/O PFD
ATA 34.10 NAV ADR DISAGREE (ADIRU DISAGREE)
ATA 34.22 ISIS 1, ISIS 2 FAULT (22FN)
ATA 34.12 IR2, EFCS1X, IR1, IR3 FAULT
ATA 27.90 F/CTL PRIM 1 FAULT
ATA 27.90 F/CTL SEC 1 FAULT
ATA 22.83 AFS 1, FMGKC1 (1CBS2)
ATA 21.31 ADVISORY CABIN V/S
------------ END OF TRANSMISSION------------

I believe we can rule out icing of the pitot tubes as cause for TCAS Fail, and we can rule out attitude, as the TCAS Faults came before the IR Faults.

We are left with a few possibilities, one being a TCAS antenna.

Another possibility is Altitude Fail, but that does not appear so early in the reporting, if at all.

Sure, severe turbulence could trigger a TCAS Fail in an intermittent installation, and I would be looking at the airplane's history for that.

Otherwise, I'd be looking for lightning damage, rare as it may be at that fright level.

GB

Last edited by Graybeard; 10th Jun 2009 at 19:00. Reason: Corrected ISIS ATA; thanks Selfin.
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Old 10th Jun 2009, 17:17
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hf fault

Great Work Greybeard! The HF was most likely operational until 0214z (we say this, because of the absence of a LRU ACARS message of it being faulted). Therefore, the vertical stablizer was intact and had not left the airplane before 0214z.

This Means that the ACARS messages probably preceded the fatal loss of control event.
Does the HF antenna provide an specific input for fault detection or the lack of the HF antenna would be detected by the absence of (constant and periodical) inputs in a given buffer outside the rudder ?
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Old 10th Jun 2009, 17:27
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I have a closely related question:

How much is known about the processes by which pitot tubes ice up at altitude? I have read a number of other reports which suggest that the culprit is not liquid water (or at least do so to me since pitot tube icing is the only icing mentioned, and in at least one case, ice crystals and graupel were reported at FLs 180-310, while icing if pitot tubes occurred at FLs 390 and 410).

Is it possible that the ice crystals deposit and fuse inside the tubes, thus obstructing them? Of am I missing something major?
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Old 10th Jun 2009, 17:36
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Lav door:



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Old 10th Jun 2009, 17:51
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Mobile OnAir GSM service on board?

Starting in 2008, Air France is said to have offered a GSM-based service named "Mobile OnAir" to their passengers, which had allowed to use a cell phone during flight, at least on an experimental base. For obvious reasons, I'm interested to know if this service had been continued until today, in particular, if AF447/F-GZCP had an active, satellite linked GSM basestation installed.
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Old 10th Jun 2009, 18:17
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Ground brick,

You've stated that HF is not an option for data transmission but on the latest HFDR(high frequency data radio) equiped aircraft data transmission by the ATSU is indeed possible.

This aircraft technically didn't have a ACARS system instead it had a ATSU which acts as a router of data from the FMGEC, CMS or FIDIMU to the VDR(VHF data radio), SATCOM or HFDR depending on selected customer options.

The hardware functions of a ACARS CMU are carried out by the AOC software in the ATSU.
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Old 10th Jun 2009, 18:18
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Correct translation would be "where legal medical examinations will be carried out".
I would translate as "forensic examinations."
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Old 10th Jun 2009, 18:22
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I read through the Air Caraibe report despite poor French.One thing that stood out for me:
"En effet,le PF est intimement persuade que les deux alarmes "STALL" sont inappropriees."
ie.the pilot relied on instinct/airmanship by ignoring the false STALL alarms.
The report seemed to imply that it was a good thing that the crew couldnt read the TECH RECOMMENDATIONS in the turbulence,because they would have directed the crew to respect the alarms,as already discussed by Bobrun.

The report spoke of an environment that was "extremement charge" due cacophony of aural alarms.They focused on "flying the plane" and reading the UNRELIABLE AIRSPEED checklist and here I lost the translation a bit but it seemed to say that having disengaged ATHR and set turb N1 prior to the crazy airspeed readings(they encountered turbulence earlier),they were already at an advantage.They were already in a state of preparedness and so could " renforcer son attention sur sa trajectoire et sa vitesse"(fly the plane).Only speed reference was GPS.

"Never in the field of PPRUNE boredom has so much speculation been based on so liile facts"

This (and the previously closed thread) make the speculation about BA038 seem restrained.
Nobody died on BA38.Contribute or shut up but dont denigrate.
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Old 10th Jun 2009, 19:09
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@Rananim:

"En effet,le PF est intimement persuade que les deux alarmes "STALL" sont inappropriees."
ie.the pilot relied on instinct/airmanship by ignoring the false STALL alarms.
In fact the PF was truly convinced that the two alerts "STALL" are false
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Old 10th Jun 2009, 19:51
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Greybeard, Safety Concerns

Request for clarification..
Greybeard posted this on the previous page: ATA 34.12 IR2, EFCS1X, IR1, IR3 FAULT.
I originally thought this meant failure of all three IR, an assumption I made several days ago, but I also remember reading that the "EFCS1X,IR1,IR3" bit refers to the equipment reporting the fault, which in this case is entirely logical. This would imply that IR1 and IR3 were not reported as failed.
So is IR2 the only IR to be reported failed?
Thanks, TP
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Old 10th Jun 2009, 20:08
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Tripple Bravo two pages back (1088) posted a link to visit. This was from that site, and may be helpful to some.


http://www.iag-inc.com/premium/acars2.pdf
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Old 10th Jun 2009, 20:10
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Tail and other debris

Those who imagine the tail separated on impact must realize that the plane would not "sink" but be fragmented into thousands of small pieces, with a massive region of floating paper, insulation, and all manner of debris, intermixed with fuel, oil, and hydraulic fluid, some of which would be deposited on the surface of the tail section - we know this looks clean as a whistle and was found off by itself - making it almost certain that the tail separated well above the main wreckage site.

I would then propose an alternate theory - from the visible damage to the tail section's lower region - the presence of middle and rear mounting boxes that have been torn from the empennage structure - perhaps the front mounting lug failed, allowing aerodynamic forces to lever the tail backward just enough to allow 500+ MPH air to penetrate into the body of the tail section - this would probably be enough to pry the tail section from the empennage and cause the visible damage to the lower part of the rudder, and would also result in the obvious torqueing seen on middle and rear the mounting boxes that remained attached to the tail section. The front mounting lug is missing in just the same way seen on AA587. This would also explain why the rudder remained attached to the tail section with no evidence of excessive sideways force being applied to it.

-drl
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Old 10th Jun 2009, 20:23
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Originally Posted by TripleBravo
Lost in Saigon,

if the expert talking here: Innovation Analysis Group is not talking about the CAB PRESS advisory, then I would refer to him as a real expert. (Had no time to actually watch the video.)
The expert quoted here has little or no Airbus knowledge.
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Old 10th Jun 2009, 20:26
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Hi,

New here, but may be able to contribute something.

HF Antenna: The state of this would be reflected in the vswr reading, which essentially says how well the transmitter is matched to the antenna. If the antenna is missing, or cable open circuit or shorted, the transmitter autotune would detect it and either run at reduced power or shutdown completely.

Whether this would result in an ACARS message, someone else may know, but it is detectable and should be logged...

Regards,

Chris
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Old 10th Jun 2009, 20:27
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Originally Posted by BOAC
While we wait (hopefully) for the FDR/CVR is it possible for someone ?!WHO KNOWS!? to summarise what can be deduced from the 24 ACARS messages we have seen?
Much earlier in this thread I have with the help of a retired A330 engineer posted the following decoded maintenance computer ACARS messages:

The PFD flag at 210Z was an "airspeed limit" warning (error code 2283)

The PFD flag at 211Z was a "flight path vector" warning (error code 3412)

The above from my post 6 Jun here.

Two more required expert interpretation as they can have multiple meanings:

The Rudder TRV Lim Fault at 210Z (code 2723) is a reported fault by the flight control primary/secondary computers and is probably related to the loss of ADIRU air data. This is not solid, but likely and is also a known and expected fault message as any other failure of the rudder limiter would have been followed by additional failure or warning messages.

I have mentioned this before on this thread and discounted "Daryl's" Honeywell 'expert' interpretation of this message.

The 214Z advisory warning (code 2131) could have been one of the following:

Cabin Vertical Speed, Cabin Altitude, Differential Pressure or cabin pressure controller data loss (lack of pressure info, TAT or mach data from the ADIRUs). When there is a loss of ADIRU air data, the cabin pressure controllers will pass the same code without extensions. The first two advisory messages (vs and Cab Alt) would be accompanied by other faults so this is most likely to have been a warning about the Delta P (descent rate being too high) or a general cabin pressure controller fault. Again not solid, but the last two ACARS received code interpretations are the most likely scenarios.



Finally, the least glamorous 2245Z maintenance status (code 3831) message is related to the vacuum system controller for the toilets. This could be a potable water or waste tank level, tank differential pressure, or general toilet (unassigned) fault.
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Old 10th Jun 2009, 20:42
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Thanks, va, but I am looking to see what can be reasonably deduced from the messages in terms of systems degredation. As little supposition as possible? EG are we CERTAIN the initial warnings came from 3 failed pitots as seems to be the baseline here, or could we be looking at software rather than hardware??
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Old 10th Jun 2009, 20:48
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Boac, yes, well in that case, only these two:

The PFD flag at 210Z was an "airspeed limit" warning (error code 2283)

The PFD flag at 211Z was a "flight path vector" warning (error code 3412)

fell into the definite bin.

These results were passed along via an exchange of emails so I will try a prearranged phone conversation to see what else can be made more solid in the list.
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Old 10th Jun 2009, 20:50
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Finally, the least glamorous 2245Z maintenance status (code 3831) message is related to the vacuum system controller for the toilets. This could be a potable water or waste tank level, tank differential pressure, or general toilet (unassigned) fault.

Maybe the A/C flying up side down giving that status
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Old 10th Jun 2009, 21:16
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Apparently they've now recovered over 100 pieces of debris.
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Old 10th Jun 2009, 21:22
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Pure speculation from me, but I see the Captain in his bunk, the F/O's putting the a/c in a big Cb, probably due to botched (if well intentioned)attempt to navigate around them on their own without waking him.
Why so many have a concern were the Captain did sleep or whatever? as i understand the 2 F/O was highly qualified for the A/C
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