I think the ‘flight-engineer’ in most Lancaster crews should really be thought of as ‘assistant-pilot / flight-engineer’…

…but ironically the flight-engineer would be the least likely to have had any pilot training as I think I’m right in saying that most flight-engineers were British (rather than Canadian / Australian etc) or at least were trained in Britain as there was less need for ‘flying’ training (much of which was done in Canada for other aircrew for example).

I’m not really sure how the initial crew selection process worked in the RAF but weren’t navigators and bomb-aimers mainly trainee pilots who had been ‘washed-out’ of pilot training? As such, depending at what point during that training they’d been ‘washed-out’ there would possibly have been more ‘redundant’ piloting skill on board the average Lancaster than may have been imagined!

There were instances of navigators or bomb-aimers flying bombers back to Britain after the pilot had been killed or otherwise incapacitated (or had baled-out!) including landing (damaged) bombers on darkened wartime airfields…

…the reward in one case was ‘remustering’ the crew-member concerned for pilot-training!