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AF 447 Search to resume

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AF 447 Search to resume

Old 1st Nov 2010, 22:13
  #2341 (permalink)  
bearfoil
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NeoFit

Right you are, any com from 447 would be memory only. The RMP3 inop was not an operational factor? How do we know this? two of three audio sort can definitely play a role. If 121.5 was needed under great pressure, and pilot needed a switch, the RMP inop could have been just one more thing to have gone wrong. Strikes me that MEL with two of three is a smidgeon lax?

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Old 2nd Nov 2010, 00:25
  #2342 (permalink)  
 
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Bearfoil
If the a/c (447) turned in either direction, 459 is the likely flight to interrogate for any desperate contact from 447. Why? In turning, it was allowing 459 to get "closer" to their problem, advantageous for reception of a 121.5 ELT at impact.
Situational awareness of other traffic by AF447 isn't something I'd hang my hat on. Evidence points to the fact they were on Selcal watch from 0136z, and I doubt they even knew that AF459 was 30 mins or so behind them.

The ELT business has been discussed thoroughly earlier in this thread:-
  • Manual/Auto activated fixed unit with antenna on top of fuselage just aft of rear door.
  • Likely antenna was lost as V/S departed on impact.
  • Portable manual units in cabin.
  • One recovered - unactivated.
NeoFit

The MEL on departure Rio de Janeiro covered the substitution of the good overhead unit (RMP3) for the PIC's faulty unit (RMP1). What could have triggered a similar failure on the relocated RMP3? The only thing that happened after their last comms with RECIFE Center on VHF, was a transfer to HF and establishing comms with ATLANTICO. The MEL seems rather innoccuous - it may or may not be important.

mm43
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Old 2nd Nov 2010, 02:26
  #2343 (permalink)  
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mm43

The point being: If one Pilot is incapacitated, we're down to one. Shall the remaining pilot let go the sidestick to reach over and fondle the one remaining on the "2 side?

Not so innocuous? Something happened and comms weren't happening.

Re:459, I did not intend to infer 447 had knowledge of 459 in trail, only that any 121.5 would likely be received by the AF behind, had it occurred.

Thanks for everything,
bear
 
Old 2nd Nov 2010, 03:39
  #2344 (permalink)  
 
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Grity
the grid spacing in direktion latitude is 1 minute of angle = 1 nautical mile = 1852 meter
Thanks for that information Grity. Just didn't know where to find it and I probably drew a wrong conclusion as a result.

Another slim possibility for the SE leg of the spill in addition to a portion of the aircraft (like a wing) skittering over the wave tops, might be a portion of the aircraft containing fuel sinking and encountering a subsurface current significantly different in velocity/direction, thus leaving a trail back on the surface. Project DeepSpill mapped the additive vector effects of subsurface currents during the tests and provided some interesting data on the displacement of the POL plume on its way to the surface.

Regarding potential voice communication on 121.5. I'd be very dubious. The priority has always been Aviate, Navigate, Communicate.
With the flight control issues they must have had, about the only thing you might expect to hear would be something like, "Hoist one at the bar for me." and that only after they had given up all hope, which any real aviator would never do.
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Old 2nd Nov 2010, 09:49
  #2345 (permalink)  
 
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mm43, depending on noise and TX power on VHF the communications range might have been as great as 500 miles for two aircraft at 35000'. For line of sight communications on UHF (higher base path loss) the narrow band FM range is at least 30 miles in my experience. So pure line of sight with AM and 5 watts should be at least 300 miles. At even higher frequencies people have gone mountain top to mountain top with WiFi over 200 miles. So by that check aircraft to aircraft range at 35000' to 35000' should be close to double the aircraft to ground range. Cut off some for multipath as you become tangential to the Earth's curvature and 400 miles should not be difficult.

So a simple "Hey, could you wake up DAKAR for us?" call should have removed ONE obstacle to their being noticed as overdue immediately after they went down. The absence of position reports should have been another cue.
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Old 2nd Nov 2010, 09:56
  #2346 (permalink)  
 
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We'd all be better informed if there was a simple switch to activate "VOX" (voice activated transmit) for 121.5 MHz, so at least everybody would have heard the cockpit conversation as it went down without any further pilot interaction.

I wonder if safety people have ever considered such a concept. (If VHF comms used SSB instead of AM interference would be much less of an issue for using such a technique.) They might even suggest actuating this mode automatically on AP disconnect until the pilots turn it back off. Then 121.5 MHz becomes our surrogate CVR.
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Old 2nd Nov 2010, 11:27
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Weather at 1:36

Any thoughts on the weather at 1:36 as it relates to the non responsive cockpit. See bottom of pp 89 of 1st report. The cells were apparently converging at 1:30. Seems far out at Mach .82, but I am also thinking of the masked cell theory.
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Old 2nd Nov 2010, 13:07
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Accident report recommendations

Hi

I was reading the old report by BEA on the accident of Pan Am 816 back in 1977.
http://www.bea.aero/docspa/1973/n-pa...n-pa730722.pdf
The second recommendation of the two given by BEA is that CVR:s and FDR:s should in the future be designed to eject from the aircraft and float in an accident. That was very many years ago, but nobody seems to have followed their safety recommendation. In my own field such behavior is regarded as almost criminal.

Regards
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Old 2nd Nov 2010, 14:32
  #2349 (permalink)  
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Diversification

The interaction between the Aviation industry, the Regulators and the public is a constantly morphing 'being' relative to "minor" actions. There is a tacit (and written) 'book' that gives all of us direction, and motive in the interest of Safety.

New products, business models, cultural fad/fashion, etc. must have a place at the table, Aviation is a business, in every respect. In the broad view, 'fear' of flying has been replaced (too often) with nonchalance. This is good, and bad. When Propellors are slung off an engine, or unknown 'whirl mode' physics kills people, every person takes alarming note. When periodic inspections of a/c are deferred (by rule), or slyly 'pencil whipped' into compliance by greed, the conflict is less publicly apparent. Too many maintenance bases have people who view regulations as "obstacles" rather than necessary guidelines.

Relative to 121.5 and its impact on the investigation, so many things were going wrong with 447, that in all honesty, some perspective is needed to understand the lack of an emergency call. It boils down to pilot incapacitation, a too heavy work load, or duff radios/antenna. Everything about overwater twinops has been addressed, so we can comfort ourselves in the knowledge that it is highly unlikely some new and mysterious enemy in the sky is at work. The end result of the investigative exercise will very likely be related to mechanical, human, or Natural causes, and these causes very well known to the professionals having a look.

No pilot finding himself in the situation these crew did would likely consider extrapolating a final impact zone to pass along to his 'collectors'. The need of a modified automatic broadcast may be obvious, but that is subject to new mandates, an adversarial and inescapable exercise known as "Notice of Proposed Rulemaking".

thx for your contributions, imo this is a very important venue for advised give and take.

rgds,
bear

Last edited by bearfoil; 2nd Nov 2010 at 16:19. Reason: miscreant comma deletion
 
Old 2nd Nov 2010, 16:12
  #2350 (permalink)  
 
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Originally Posted by diversification
In my own field such behavior is regarded as almost criminal.
Such expressions in a technical forum call for a reaction. BEA recommends that a (feasibility) study of means for automatic ejection of flight recorders be untertaken. The recommendation is not addressed to anyone. Was there a follow-up? May be the feasibility study was undertaken, and demonstrated that the risks to the airplane outweighed the potential benefit for accident investigators. Do you know anything about the follow-up?

regards,
HN39
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Old 2nd Nov 2010, 16:31
  #2351 (permalink)  
 
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Communications

Gentlemen,

if one wishes to have a serious look at communications in this instance, then it would be nice to know who on the ground first realized something was very wrong. Why did a stream of messages pointing at some serious failures onboard, followed by lack of automated position reporting, fail to wake someone up in either Maintenance or Operations/Dispatch ?

Remember, a series of more than 20 technical faults between 02:10 and 02:14, and then no automated position report at 02:20... No auto pos report at 02:30... No auto pos report at 02:40... Who is lacking in communications discipline here ? What is the use having someone supposed to watch over the whole operations, ETOPS & Dispatch, etc...

Clearly, when did someone, either in ATC or in AF ops, wake up and pick the phone up ?

Trying to find fault into the perfectly normal behaviour of a crew on SELCAL watch, or trying to say that somehow they should have written their death will on 121.5 while having their hands full with messed up flight controls and UAS... No pilot would do that, really, except on a TV show. We are talking imminent death here, and few are those who faced that who can talk about it. A little respect is due here.

In addition, who was there to listen on 121.5 and who was questioned by whom on that particular subject ? I wouldnt like to be the one who was on watch on 121.5 at that time, both because of what they could have heard, and because I would not enjoy being told to shut up on this matter.

Either there is no deliberate intention to hide the truth, and a lack of comms on 121.5 by the doomed pilots is very understandable, or there is a deliberately misleading smokescreen in place, and there is no way you could tell with certainty that no communication occured at the time of accident.

This communications subject is not one with which one could try to bash dead pilots, but it does raise some nasty questions for all those still alive on the ground who were supposed to watch a little over them.
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Old 2nd Nov 2010, 16:34
  #2352 (permalink)  
 
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ATLANTICO was in communication with other flights on that track that night, as flights alerted ATLANTICO of their deviations because of the weather. To this point, the BEA has not released the transcripts of any conversations between ATLANTICO and these other flights enroute TASIL.
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Old 2nd Nov 2010, 16:46
  #2353 (permalink)  
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SaturnV

Nor is any information relative to inter flight comms available. There had to have been some, perhaps even a good deal of chatter, weather, etc. The basic bonds of pilotage seem to have been hidden from "sight". Must be quite damning, I should think. ACARS, by its very creation, demands constant monitoring, or what's the point?

Svarin

That's it, in a nutshell.

Last edited by bearfoil; 2nd Nov 2010 at 18:15.
 
Old 2nd Nov 2010, 18:09
  #2354 (permalink)  
 
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JD-EE
depending on noise and TX power on VHF the communications range might have been as great as 500 miles for two aircraft at 35000'.
The graphic indicates that, i.e. any 250NM radius circle whose circumference intersects another, puts those aircraft within VHF range. All of the aircraft plotted were well in VHF range of each other.

mm43
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Old 2nd Nov 2010, 18:54
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Svarin
Why did a stream of messages pointing at some serious failures onboard, followed by lack of automated position reporting, fail to wake someone up in either Maintenance or Operations/Dispatch ?
That is a matter for Air France to address. I am sure the same systemic failure wouldn't or shouldn't happen again in that organisation.

However, there is a curious correlation between the AF on ground failure and what happened in the air that night. Remember at INTOL the crew gave ATLANTICO their times for SALPU and ORARO? They then didn't report at either waypoint, and neither did ATLANTICO attempt to call them.

Was it because they thought that as ATLANTICO had also given them a change to the primary HF frequency after TASIL that they were not expected to report again? No, I suspect that something else happened, because at the least I'd expect they would have called ATLANTICO at ORARO with the estimate for TASIL (FIR boundary).

Possibly AF447 did try calling ATLANTICO and were not heard. I doubt it, there would have been some trace of that call either on ATLANTICO's 6649kHz tape or tapes of any of the other stations sharing the "CAR-A" 6649kHz frequency, i.e. Cayenne, Georgetown, Caracas, Havana, Merida, and New York. On the otherhand, did anyone check?

The BEA in their interim reports have only presented the bare facts surrounding this comms mystery, and I expect that when the final report goes to press, some further observations will be included.

mm43

Last edited by mm43; 2nd Nov 2010 at 19:08.
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Old 2nd Nov 2010, 19:42
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HN39

Accept my humble apology. I made an error in translating the french and added more meaning than was there.

Regards
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Old 3rd Nov 2010, 16:14
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After some very interesting offline discussions (by “offline” I mean via PM’s and emails, rather than open fora) I’m wondering if there are any techies (AB / ACARS), or other knowledgeable folks, out there who can contribute information and ideas to this discussion.

Proposition: The initial ACARS messages relating to a “pitot-static” fault (34111506) were said to indicate “faulty airspeed sensors.” As far as is (publicly) known there is no information that can establish the “origin” of the fault (or “disagreement”). Much has been said and written about ice accretion, super-cooled water droplets, etc, but there seems to be no basis for a factual conclusion that “ice accretion” was the reason for the fault.

This leads to two immediate questions:
1 What other circumstances (i.e. disagreement among the pitot-static sources) could have generated those same messages?
2 (Flowing from question 1) Could those particular messages have been (for instance) the result of airspeed disagreement due to an unusual attitude of the aircraft?

According to BEA, AF, and AB, there is some ambiguity with regard to timing of events v/s timing of transmission of specific ACARS messages. I suggest that, given that uncertainty, along with the uncertainty of “causes v/s effects” within the actual chain of events, we are left with a still very large realm of possibilities – and very few “probabilities".

Discussion?
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Old 3rd Nov 2010, 18:23
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Disagreements

When i look at the published diagrams of the system, the signal from a pitot tube is measured/digitized by an ADM unit and the resulting data sent on a data-bus to the corresponing ADIRU unit. That unit also obtain digital data from one of the static ports and its ADM-unit. Based on these data the ADIRU computes the actual speed. This system is in triplicate.
Resulting three air-speed values from the three ADIRU:s are then sent (in syncronized or random fashion?) to each of the three computers where they are compared before use.
If the data refer to three measurement made at slightly different times, they may differ if the airflow is shifting around the aircraft.
The logic is said to be that each computer tests the differences between these speed values. If they agree within a given limit their median is used. If the difference is larger, the average of the two closest is used instead and the value with the largest deviation is assumed to be false (resulting in an error msg). In case there are three AoA units their data are treated in the same way. When only two AoA:s are in use, their average is said to always be used.
In the special case that the remaining two values also differ by more than a given amount the msg for three invalid air-speeds is generated.
In case that one or more of the ADIRU:s cause the speed error, this message has perhaps nothing to do with the pitot tube, its connection to the ADM, or the ADM unit. The ADIRU:s have selftest programs and should therefore report any internal inconsistency - however this selftesting has not worked as designed in a few cases. The possible cause is still under investigation.
Thus the Airbus system differ from the one used by Boeing, where three ADIRU:s are combined into one unit and the speed comparison seems to be done inside this module.
It is a pity that we don't have accsess to the source codes used nor program flow-sheets.

I hope I have avoided most mistakes in this description.

Regards
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Old 3rd Nov 2010, 18:45
  #2359 (permalink)  
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grizzled

I know that your second question has been posed before, It was I who posed it. Too much appears to have occurred prior to AS disagree to assume that the pitots were in any way compromised, or the statics, for that matter, imo. The pertinent question is to ask a 330 pilot if he thinks it possible, a/p active, to encounter Unusual attitude sufficient to disturb airflow twixt port and starboard to create discrepant readings that might mimic Pitot Fail? Adding allowed Pitch and Roll excursions (might as well include some Yaw) together creates quite a large circle of offline attitude as described by the nose relative to straight and level.

I haven't any access to the 330, but occasionally visit a 300 freighter. The last time we met, there were brand new and beautiful Pitots attached to either side of the Fuselage, and there were four of them. Imagine.

cheers
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Old 3rd Nov 2010, 19:23
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Disagreements - addendum

We should be aware of the possibility that the system works in other ways as it is "software driven" and this kind of software sometimes is modified, up-dated, replaced.
In principle it is thus possible for all units to communicate with each other anytime using the common bus-system.
Errors in the program(s) running in ADIDU units have been detected earlier, often after software up-dates that brought an earlier buried program bug to the surface.
Some links and comments:
ADM example:
http://www51.honeywell.com/aero/comm...ata_Module.pdf

Observed ADIRU problems:

9M-MRG: The ATSB found that the main probable cause of this incident was a latent software error which allowed the ADIRU to use data from a failed accelerometer.

On 6 August 2008, the FAA issued airworthiness directive 2008-17-12 expanding on the requirements of the earlier AD 2003-26-03 which had been determined to be an insufficient remedy. In some cases it called for replacement of ADIRUs with newer models, but allowed 46 months from October 2008 to implement the directive.

The 46-months span the time of the AF447 accident!

Regards and good luck with the structuring work.
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