My Dad was a Flight Leiutenant at the time
H, the rank structure that I described was for NCA (Non-commissioned aircrew) - the officers' ranks were unchanged.
However, if I may correct myself, I got the equivalences wrong in my earlier posts... in fact Aircrew I was the FS rank while Aircrew IV was for the corporal. The confusion comes from the number of stars in the rank badge. Aircrew 4 has one star while aircrew III has 2 stars and aircrew II has 3 stars. Aircrew 1 has a crown over the 3 stars. In effect, the stars replaced the ground trades chevrons... no wonder it didn't catch on!