CVR location questions
A number of posters have questioned CVR/FDR locations, numbers and backup power. First issue is that this is restrained by costs. The operators will resist anything that adds to costs (this includes weight). The take up of solid state digital (soild stste is the recording medium, traditional "digital" FDRs use magnetic tape) recorders is because they are cheaper to maintain (no moving parts). With solid state digital you can easily have a combined CVR/FDR, but this "puts all your eggs in one basket". The sensible solution roposed by the regulators and used on the latest aircraft is to have two combined CVR/FDRs one at the front and one at the rear of the aircraft. This gives the best of both worlds, still only 2 recorders to pay for, better chance of one surviving and you only have to find one to get all the data. There are proposals to mandate short back-up power supplies to capture data after power loss but again it's costs, particuarly lifetime costs - batteries require maintenance- that i producing resistance. There are also proposals for cockpit video recorders, crashworthy or otherwise, but that's a whole other issue.