Locator Beacon (Pinger) batteries
Just a word on CVR (and FDR) locator pinger batteries. They do not have a fixed life as such and they do not shut down after 30 days. They are designed to provide optimum performance for 30 days (90 days in the case of newer style batteries which I understand this aircraft may not have had). During this time the batteries will slowly discharge and the voltage will reduce but the pinger is designed to operate normally on a reduced voltage so is initially not affected, hence the "guideline" figure of 30 (90) days. When the battery has reduced to this voltage level, where the pinger works at optimum performance, the pinger performance will start to reduce and this could take days or weeks before it dies completely. Another factor is the age of the pinger and battery, which should be replaced at regular scheduled intervals (cannot recall what it is now).
The bottom line is that when the towed array finally arrives on site they may still have several weeks rather than days to listen for it. Chance of picking it up will reduce with time but it will not just suddenly switch off at 30 days. Just like the average torch it will slowly get dimmer and dimmer until it fades to nothing.
PS: I worked on CVRs until 25 years ago and continued to sign them off until about 10 years ago. Pingers (as we called them) were not repaired but replaced with new items, complete with battery, as I recall.
Last edited by Ka-2b Pilot; 28th Mar 2014 at 13:56.
Reason: Clarify which pinger and added PS.