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"The hunt for the missing Malaysia Airlines plane has shifted below the surface, with the "towed pinger locator" deployed on Friday to search for the black box before its batteries expire."

I wish them luck with that. From experience on the SAA295 'Helderberg' job I know that they've got a sub-minimal chance of finding that pinger in the next week or two. This wreck will be found acoustically, that's almost for sure, but it'll be by low frequency (100kHz or better) side-scan sonar --- or perhaps by pp-magnetometer... Almost certainly not by a couple of pinger locators and most certainly not by a fleet of photogenic aeroplanes sent on a photo-opportunity in a show-biz charade to assuage the PR efforts of three politicians and to satiate half a hundred rolling-news networks on telly.

A comparison with the Helderberg job is quite informative, mostly for its differences rather than its similarities. The water depth was broadly similar, circa four and a half Klicks if I remember correctly in that case. We never found the pinger(s). Not acoustically, anyway. After the thirty days plus ten percent we gave up dragging pinger locators around the hydrospace of the survey ground. We had a list of the co-ords of hundreds of false positives because we were under orders from bozos ashore to crank the receiver gain up the the max, but nothing of any use.

We did eventually find the CVR, replete with dead pinger, but that was more or less by accident when picking up a piece of wreckage with which it was entangled. That thing of quasi-accidental discovery of the recorders is actually quite common. Same thing happened with Valujet in the swamp and yet again with TWA800. In both of those cases the {insert colo(u)r here} boxes were found when someone trod on them. We never did find the SAA295 FDR, despite the fact that it had been affixed to the aircraft immediately adjacent to the CVR. Hell, they never found the recorders from the two Boeings in lower Manhattan -- and that was a case where they knew to within ten metres or better the very exact three dimensional co-ordinates of the impact points and they had reps from Boeing subbies searching every scoopful of debris for the thick end of a year.

We had the same problem, in the case of SAA295, of people ashore repeatedly switching the target area(s) as is being experienced by the poor sods at the sharp end of the MH370 search. We dreaded the hour after the end of the morning 'prayer meeting' conference calls because we knew that someone ashore would get his pencil out and make up a new box, usually in a place which could not be reconciled with any of the previous ones. Out of earshot of the shadowy civilian guy from Virginia who was leading the search from below and behind, we used to refer to those boxes as "your target for tonight".

Same thing is happening with MH370.

If such a bet were enforceable, and if I could find any mugs foolish enough to be a counter-party to the bet, I'd happily and profitably give odds of 100:1 against them finding the pinger with a pinger locator. They've got, at most, a couple of weeks, with only a couple of ships, neither of which (incredibly), is simultaneously towing a 100 kHz side-scan sonar.

Even with vane depressors and drag reducing devices such as Hairy Fairy vortex interruptors on the lower quarter of the tow-cable, they'll be lucky to make much more than three or four knots of waterspeed. The end of line turnarounds are an absolute bitch. In 87/88 we quit after doing a thousand square miles and we had the twin advantages of knowing quite accurately where the aircraft stoofed in and we had our tools in the water (titter ye not in the cheap seats!) at the locus within a week of the crash. These poor sods have none of those advantages and they are being led by an Air Chief Marshal who has reversed seamanship and placed the surface ships at the disposal and in the service of the air fleet instead of the other way around.

This evening, by any timezone, we enter the fourth week of the search and they haven't found so much as a satay stick from that aeroplane. If anybody has learned anything from the AF447 fiasco, then surely they must have learned that becoming fixated on theoretical back calculations of the impact point from subsequently discovered patches of identified and confirmed flotsam can lead to unwise people becoming target fixated on wrong locations.

With Helderberg we had two major advantages. One was that the flight deck crew had been aviating;navigating;communicating right up until very few (less than five) minutes before impact and had been giving copious amounts of positional and intention information to ATC. Very different to MH370. The other massive advantage we had was that the first confirmed patch of flotsam from the wreck was found, and its co-ordinates measured, just 12 hours after impact. The second patch was located just 12 hours after that.

Given the non-linearity of the mathematics of oceanic dispersal, any positional information from that elusive MAS satay stick, even if found during the fourth rather than fifth week, is likely to confuse rather than clarify the impact location. It'll tell you that the wreck lies in the SouthEastern quadrant of the Indian Ocean and not at some fairytale Dawson Field in one of the 'stans, but we pretty much know that anyway.

The ugly truth, quite certainly unpalatable to the two prime ministers and 230 sets of bereaved relatives, is that the best chance of finding the wreckage and a few fragments of human remains lies in a very long hard slog with side-scan sonar. It's a search which is likely to take very large fractions of a year or, more likely, multiple years. Enthusiasm for funding such a prolonged and open-ended search will surely dry up, as it always does, when the bills start flowing in and become overdue for payment.
Malaysian Airlines MH370 contact lost - Page 462 - PPRuNe Forums 2014-04-04
Reposted bymofo mofo

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