While the Cospas-Sarsat satellite system for search and rescue has been "undoubtedly helpful", said the group, its detection of beacon signals after a crash "remains problematic" - either because of malfunction, submersion, obstruction or damage.

BEA sought advice from Cospas-Sarsat's operators to see whether beacons could transmit "a limited set of parameters" before an accident, and was invited to attend a meeting in Washington in September 2010 to draft initial operational requirements for next-generation beacons.

There have been previous similar suggestions, said the BEA, but the benefit has been impaired by limitations of Cospas-Sarsat's Leosar low-Earth orbit satellites, whose detection capability is "incompatible" with the typically short interval between an aircraft encountering distress and a resulting accident.

But this limitation "will disappear" with Cospas-Sarsat's medium-orbit Meosar system, it added. Initial testing shows localisation within 5km (2.7km) could be achieved with a single transmission burst.

The BEA adds that the time between beacon activation and initial data burst, currently specified at 50s, could be reduced to 3s to ensure data transmission initiates before a crash.

Cospas-Sarsat plans to approve operational requirements this year and compatible beacons could be available by the end of 2015. Meosar operational capability is expected in 2018.

Source: Flight International