AF447

[broadreach]

Phase One was what we were expecting in the first weeks after the crash: immediate evidence, rapidly recoverable.

Phase Two would have brought huzzas for the technology that found the aircraft so soon. Its lack of success has messed us about a little.

Phase Three is what we’re hoping BEA, AF and AI have the bottle for, a long dreary process with some sort of find that encourages more searching, because not all the pieces may have settled in one place on the ocean floor.

I’m still hopeful that a serious search will continue, as opposed to one just for show. But one can only wonder at all the pros and cons going through the deciding minds at BEA, Airbus Industrie and Air France: consign the accident to history and move on based on assumptions, hoping that people will forget, or some right out and say how far they’re willing to go to establish what actually happened.

[mmciau]

I believe that there so many unanswered questions about this accident that the authorities will endeavour to find and retrieve the Recorders if it is at all possible.


Mike McInerney

[Mr Optimistic]

Any indications of doubt over area to search for Phase 3 ?

Suppose the area to be searched will be discussed by the called together forum but are there any indications, in any reports from BEA, that the negative results so far mean that the area to be searched should be changed ?

[Chu Chu]

Does anyone know how much real-time analysis would have been done on the side-scan sonar data? I've got a mental picture of the ship crew watching the screen for an outline with two wings, two engines, and a tail. Which, of course, they weren't likely to see. Maybe experts are poring over the data now, looking for more subtle targets.

[SaturnV]

There is no public info on the technical aspects of the side-scan sonar search, e,g., at what depth was the sonar operating. There are military side-scan sonars that can operate at pressures up to 3000 meters deep, so perhaps if one of those were made available, they might re-do the search grids if the sonar during the second phase search was operated at a much higher depth..

Another side-scan search might find the main wreckage. Even if the main wreckage is found, the odds of finding the boxes are pretty low. If the fuselage slid down the side of a seamount, bringing down a seaslide of sediment and rocks with it, the boxes might be buried.

[ALPHA FLOOR]

It is my opinion that neither Airfrance nor Airbus "really" want those recorders found - the lack of communication from our fleet office wrt this accident (the largest 330 operator in the world) just goes to reinforce what I and many of my colleagues consider somewhat of a conspiracy.

AFL

[RatherBeFlying]

Develop Sonar Target Signature

• Find a twin with similar planform parked in desert storage facility.
• Fit up as a drone
• Add robust long lived pinger
• Stall it over the ocean in the general accident area
• Run sonar over wreckage at various track angles to get signatures against the bottom
• Apply signature to area scans

[vapilot2004]

It is my opinion that neither Airfrance nor Airbus "really" want those recorders found - the lack of communication from our fleet office wrt this accident (the largest 330 operator in the world) just goes to reinforce what I and many of my colleagues consider somewhat of a conspiracy.

Surprising suppositions. Well almost.

Airbus should be keen on retrieving the things. The only way the manufacturer would not want the boxes to be found is if they already knew what the problem was and it has not so much to do with proboscii.

Air France on the other hand might benefit from the benefit of the doubt according to the legal guys. Doubt = minimum mea culpa.

[SaturnV]

alphafloor, you ought to include the Brazilian government as a co-conspirator. If the Brazilians had searched the area west of the track, instead of concentrating on the area east of the track, the debris field might have been discovered by June 2nd, and more proximate to the actual crash location.

ratherbeflying, the signature that the fuselage may present to sonar may be a lot smaller than you apparently expect. If the fuselage is still largely intact and on a slope, the profile presented might be more the cross-section of an 18 foot hollow tube, rather than a nice horizontal presentation of 150 feet or so of metal.

[RatherBeFlying]

If the fuselage is still largely intact and on a slope, the profile presented might be more the cross-section of an 18 foot hollow tube, rather than a nice horizontal presentation of 150 feet or so of metal.

Can't say how many segments the fuselage is in now. The sea surface and bottom impacts can each make a contribution. I venture the best candidates for large components would be the wings and centre section. Then there's how they will array themselves on a slope or collect in a hollow possibly with avalanched slope debris on top

A nice long cylindrical section could roll down a slope or could hang up on a bench or projection or end up on the bottom of a slope.

It would take a lot of cheap airframes to work out the many ways the pieces might come to rest on a contoured bottom.

There have been sonar searches for historic wrecks on reasonably flat bottoms that have taken years.

[Backoffice]

As has been mentioned in earlier posts, if the majority of the aircraft sank in large sections they may have retained some buoyancy and not have gone straight to the bottom, especially with the large amount of composites and possibility of fuel trapped in tanks it may well have travelled miles outside the search area.
I would have thought the engines are more likely to be detected by their magnetic anomaly, assuming the searchers have access to and can use that detection method at that depth.

[Dysag]

Backoffice

"especially with the large amount of composites...."

Apart from the fin, which detached, and possibly some cabin furnishings, there is only a small amount of composite material in an A330.

[Chu Chu]

The more I think about this, the more I wonder if it's as simple as this:

Phase 2 = side-scan sonar survey
Phase 3 = identify and further investigate targets based on Phase 2 survey.

They were discussing Phase 3 not long after Phase 2 started; perhaps Phase 2 was never expected to result in locating the aircraft without more work. Given all the false sightings of floating debris, I couldn't blame them for keeping mum now even if they had a good idea that they could see the airplane in the sonar image.

[Will Fraser]

I doubt any one would fault them for giving it a rest. I wouldn't. It may be this century's Titanic, left for a better technology in future. Rest them.

[cessnapuppy]

I agree

I agree. In reflection, we either already know what happened or have enough data to make a reasonable assumption and start to take corrective action. Including but not limited to:

• Better dissemination of weather information
• Better training, SOP clarification and use of WX radar
• Be more proactive/aggressive in diverting around bad weather
• (my favorite: hand fly the AC through the ITCZ vs using the autopilot, so if you run into unseen weather, the crew isnt tossed an unstable aircraft into their laps when the AP runs for the hills )
• More active collaboration between 'hand off zones' (like Dakar)
• Faster response when the plane goes missing

All these things we know now, what else is the CVR FDR going to tell us? Useful? perhaps, but not particularly earthshattering - though I guess hearing and seeing their final moments trying to correct the plane may offer some training suggestions

[SaturnV]

chu chu, the general sequence for searches of wreckage where one doesn't know the precise location, is to use side-scan sonar to sweep where one thinks the wreckage might be. If there is a hit, i.e., an area worth investigating further, then a submersible is sent down to photograph. If the visuals confirm that's the object one's searching for, then more extensive photography is done to see whether objects that one wants to retrieve can be located. The ultimate phase would be retrieving any located objects.

A straightforward and laymen's description of the technology and the challenges can be read here, on the search for HMS Hood (and the Bismarck as well). Of course, this involved large ships resting at great depths on a relatively flat bottom, with a fairly good notion of where they were.

Channel 4 - Hood v Bismarck - The Search - Method

Channel 4 - Hood v Bismarck - The Search - Equipment

[cessnapuppy]

what would be good is if the sonar scan imagery and data could be placed in the public domain so that it could be reanalyzed, in the same way that crime scene photographs can be reexamined years later and new clues discerned from otherwise overlooked data

[FlexibleResponse]

If I was a betting man, I would say that the wreckage will be found, and it will be found by the USN.

We just need an appropriate amount of time for face-saving and the right deep-sea salvage contractor to be funded.

No manufacturer wants questions of safety hanging over his products. Regardless of the cause of the crash, there is an engineering solution for everything.

[cribbagepeg]

USN Technologies

It may be that the USN and other nations' forces may be reluctant to deploy their best technologies in an area where they are KNOWN to be operating lest they reveal something they'd rather not. I know that echolocation frequencies in the ocean are much more restricted than in the ether, where spread spectrum stuff can be used to advantage in avoiding detection, but one could speculate a bit...

[Machinbird]

The more I read about the USN SOSUS system and about the nature of the SOFAR channel for transmitting sound long distances without loss, the more convinced I am that positioning data on the AF447 accident can be recovered if someone can be convinced to make the effort.
To understand what the SOFAR channel is about, look at this link: DOSITS: History of the SOFAR Channel and then follow the internal links for more information.
The SOSUS system has been simplified over the years to reduce manpower requirements and has apparently lost some functionality, but appears to be still in existence.
Remember that the AF447 accident is a multi depth event. Even if surface noise may not carry well, it may reflect from an undersea mountain that is in the vicinity and then be carried to a hydrophone in the SOSUS array. Maybe the sounds of the engines hitting the bottom will carry.
We have the advantage of knowing within relatively small windows the time of the crash and the location of the crash. This permits writing algorithms for summing up the sounds within a particular directional hydrophone array to achieve higher gain from a particular direction, and for predicting the arrival time of potential signals at individual hydrophone arrays thus permitting more detailed analysis. Once the accident sound signature is identified on one array, it can be more easily found on the signals recorded on another array in a distant location. Once you have signals on a second array nailed down, you can use that information to predict with loran type precision the coordinates of the events detected.
It is probably worth a shot. It would take some analysis to come up with results and it won't happen unless someone tasks the Navy for results. An inter-governmental request by the French government would be probably all that is required. I hope they are working on it.