From memory the RAF Chipmunks could not fly in IMC as I remember the turn and slip and AI both ran of the vacumn pump
Interesting; all my initial instrument flying training in a Chipmunk took place in solid IMC. The QFIs often carried out PAR and SAR approaches in actual IMC too.
Roughly when did you do your training in IMC, because I feel sure the RAF policy changed along the way.
There was no restriction in the RAF regarding IF flying on one power source for the instruments. EFTS at Swinderby were flying their Chipmunks IMC until 1993.