I am researching a Lancaster crew from 460 Squadron and see the rear gunner left 1656 Conversion Unit for a short time to join 1481 (B) Flt - which I understand was a gunnery training flight- before returning to 1656. Could someone please explain what a gunnery training flight was and how it worked. Also, I was under the impression that an entire seven-man crew was put together at OTU stage but I have since seen reference to only five being assembled at the OTU and the engineer and second gunner being added at CU stage. Is this correct? It doesn't quite fit in with my research which shows both gunners of my crew were at the OTU together and left to go to the Heavy Conversion Unit along with the rest of the crew (other than perhaps the engineer) on the same day. Was it sometimes the case that both gunners would be crewed up at the OTU? Any assistance will be greatly appreciated. Mike