Just going back to the wounded/killed pilot, on Lancs and Halifaxes; the Flight Engineer's normally had enough basic training to fly the aircraft, at least straight and level, and some have been known (and Navigators) to bring the aircraft home and land it. If you've ever seen the movie 'The Dam Busters', it's even mentioned there, when 'Guy Gibson' tells his Flt. Engr. to get ready to pull him out of the seat if he's hit. (meaning on the run-in to the dam.) The line in the movie is based on fact, by the way, not just some movie-makers idea of adding drama.