European safety regulators have detailed certification proposals to improve the protection of information from flight recorders.
The European Aviation Safety Agency says that premature depowering of cockpit-voice recorders has, in some cases, resulted in loss of useful information which might have been captured if an alternate power source had been installed.
EASA adds that some investigations have found both the cockpit-voice and flight-data recorders were fed from the same electrical bus – rendering both recorders inoperative in the event of bus failure.
The revision also intends to reduce the possibility that impact sensors – known as g-switches, and designed to stop the recording – might accidentally be activated by other events.
"Several safety investigation bodies have reported reliability issues with negative acceleration sensors," says EASA.
"In several occurrences involving high levels of airframe vibrations, some g-switches were triggered prematurely during the occurrence and, therefore, the recording of voices or data stopped before the end of the flight."
EASA's notice of proposed amendment suggests updating certification specifications to ensure that g-switches are "not used as the sole means" to detect a crash impact.
The proposal involves relying on the start-stop logic of the recorder, instead of dedicated sensors.
EASA is also proposing provisions to accommodate installation of combination recorders as well as deployable recorders.