Question: The cockpit data recorder on-board MH370 was dead a year before the flight. Why was this allowed to happen. What precautions could now be put in place to make sure a (little, but costly) mistake can be prevented from happening again ?
As I understand it the transmitting beacon battery had expired, so the actual recording of data would have still worked anyway. But you raise a good question, i.e. how do you prevent it from happening again.
You could either do it by design, such as ensuring it is continuously charged from the aircraft power, which would be costly , probably into the billions of pounds to retrofit all aircraft with a new design recorder, and you also introduce other safety risks about continuously charging a battery as they get hot and could catch on fire.
Alternatively (and probably more likely) you could do it through checks, such as including a check of the recorder. I think most modern flight recorder have ‘built in tests’ i.e. an automated check everything is working as intended when you switch the aircraft on. I’m not sure if the Built in tests include a battery charge check, which it could easily do but It sounds like the MH370 flight didn’t have this feature but it looks like the authorities have considered this since, but too late for MH370.