stadedelafougere:
I understand that a large amount of data would be worthless, and as a result when the aircraft parks up at the gate successfully a simple signal to identify the end of the flight is sent and the airline can choose to delete the data while possibly keeping anything flagged as unusual so the maintenance guys can take a look.
Also, if the data was kept it would be easier to diagnose the start of a problem that may eventually become serious enough to cause concern. For example, a problem develops in flight for some reason, that information is now logged with the airline. If 7 days later a flight is forced to make an emergency landing, or worse still is lost the investigators can see clearly that a problem occurred at a particular time. As I understand it, the FDR overwrites itself every 30 minutes so at the moment, that particular fault would never be detected.
The argument regarding data size and cost is not relevant, I work in the IT industry and can assure you that storing TB's of information does not cost a great deal at all.
Basically, the point is that if the technology already exists for the airplane to send messages to the ground, why not take all messages that the FDR flags as unusual straight to the ground regardless of whether it caused a problem or not? Prevention is better than cure.
In response to the tombstone mentality, I understand that its a risk vs cost industry as is every industry. However, I run an IT business hosting many clients valuable data. If I receive an advisory that may cost me in the short term but will protect me in the long term I'll take it and implement it straight away as I know a total failure of my system could cost me dear. You would think that when your talking human life that could be lost it would be the same!