only 30 mins
Believe in was a union agreement between BALPA and the CAA.
It was a recommendation included in the public inquiry into the Papa India disaster when a Trident 1 stalled after take off at LHR in 1972.
A lot of BEA pilots had a distrust of management and the agreement included the facility to erase the tape after engine shut down.
I flew with the system for three or four years after it's introduction - it was ALWAYS erased (or so we thought!)