The US National Transportation Safety Board (NTSB) has recommended to the US Federal Aviation Administration that operators include cockpit voice recorder (CVR) "deactivation", either manually or automatically, in flight shut-down checklist actions; and test CVR serviceability daily, including listening to a recording, before first flight. The recommendations are in response to NTSB concerns that CVR recordings on aircraft involved in serious incidents are often useless when they could have yielded important information. The main cause, says the NTSB, is the CVR tape is allowed to run for too long after the incident occurs. Even when an aircraft has landed safely, if the CVR is left running the vital information will have been overwritten by subsequent cockpit audio sounds that may even have taken place after the aircraft has shut down on the line. Most CVRs, says the agency, still have a tape duration of 30min, but it quotes many examples of recent important incidents in aircraft with 2h-duration CVR recording systems that have lost all the data that mattered because they were not switched off after the aircraft landed.
Source: Flight International
