JD-EE remarked:-
The numbers for depth of pinger receiver, its expected range, and the depth of the mountainous ocean floor where AF447 went down left me wondering, "Why bother except to put on a good show?"
Yes, agreed for the following reasons -
The effectiveness of the 'pingers' in very deep water has always been questionable. Diverse currents and abrupt water temperature changes with depth create inversion layers. 37.5kHz propogation in water behaves in a similar manner to that which results in anomylous propogation in the VHF/UHF and higher spectrum, ie "ducting". High surface water temperatures, depth and bathymetry in an area of the equatorial North Atlantic reknowned for strong currents, effectively reduced the faint possibility that the DFDR or CVR would be located in the available time to something close to zero.
Moving on; the effectivenes of multibeam sonar in detecting specific parts of the debris is not doubted. C & C Technologies, Inc. Autonomous Underwater Vehicle (AUV) can operate at a depth of 4,500m and the resolution of the multibeam sonar in 2002 produced the following for the BBC of wreckage of a Fairey Swordfish Mk1 and a Hangar Lift Deck which parted company with HMS "Ark Royal" when it sunk in 1066m of water in 1941.
The yellow and cyan description/text has been added by me.
For good measure, here is a photo of a Fairey Swordfish ("Stringbag") on a Royal Navy carrier deck.
The problem with AF447, is
where to start looking using sidescan sonar initially.
mm43