For Correspondence column:
I have studied the reports on many air crashes and have a suggestion. One of the primary problems faced by the crash review boards such as the NTSB is the damage to the Flight Data Recorder and Cockpit Voice Recorder from the crash and possible fire. What comes to mind in studying the reports is that the actual impact is less critical than the incident that causes it. By this I mean that once the aircraft has left controlled flight, or experienced certain definable circumstances, the FDR and CVR likely contain the information that is necessary to determine why the event occurred.
Therefore, it would make some sense to define a set of circumstances that are outside the normal flight envelope of an airliner. These limits could be adjusted for each aircraft type. At a preset limit, there could be an audible/visual alert in the cockpit to alert the crew that the aircraft is approaching the limit. When the system detects that the higher 'critical' limit has been reached, the system could jettison a set of FDR/CVRs that would be equipped with a small parachute, floatation device, and locator beacons. This set of FDR/CVRs should be an adjunct to the original FDR and CVR which would remain with the aircraft until impact.
This would provide several benefits. First, this set of FDR/CVR should escape impact and fire damage. Second, as the set would descend away from the wreckage, it should be easier to detect than the set that is buried in the wreckage of a large aircraft. Third, since it would be equipped with a ELT beacon, activated on jettison, the crash location and time would be more likely to be pinpointed than in the normal case where the plane merely disappears from the scope. Fourth, the floatation device would enable a crash over water to be located more quickly, and provide for rapid retrieval of the data.
Unfortunately, the only benefit to the passenger and crews of an airliner so equipped would be the quicker location of the crash, albeit it is possible for an aircraft to travel some distance from the jettisoning of the FDR/CVR package. If the ELT was encoded with a different tone to indicate that it was a remote beacon, this should not mislead rescuers. The main benefit of this system would be to increase understanding of how the flight got out of control, and thus educate other aviators to the possible dangers.
It is true that in some crashes, such as Korea Air 801, this concept would provide no information not available from the normal FDR and CVR, but in the case of say TWA flight 800, some of the information from the CVR and FDR would have been available to the NTSB within hours of the crash. This may not have provided the clues needed to understand what occurred, but it is possible that in some crash, some day it could.