For Future "Black Box" Designers......
Bearing in mind how long it took to find and later recover the Air France AF447 Flt Data Recorder and Cockpit Voice Recorder, I have often wondered why these, valuable to the search and subsequent enquiry, items are not given some form of barostatic release. If so designed they could then automatically deploy to release themselves to the surface if the lost aircraft were to descend below a certain depth of water. As merely a retired global and ETOPS flier, I am in no way qualified to know anything about such design matters, yet is it not time that the boffins put their thinking caps on to produce such an aid to their recovery?
The parameters for 'release to the surface' could be clearly defined so as not to activate such a device unless extreme water pressure were experienced by the sensing device. The trigger for release could then be by self-contained electrical, barostatic or even chemical means.
Realising that cost versus the number of times such inventions are needed form a large part of the design equation, it brings to mind the saying that, "Necessity is the mother of invention."
Nevertheless, regardless of the cost of design and fitting such a device to long-flight, over-water aircraft, at least the families and relatives of those lost would have greater hope of some form of final closure for their lost ones.