Most of these aircraft had to be started on the ground using ground crew and external equipment. That means that if your engine cuts out completely while you're flying then your aircraft is effectively a glider. You'll have to do a dead-stick landing or ditch.
I don't know if it's do-able in CoD, but restarts were sometimes possible in these aircraft if you could use the wind resistance of the air flowing through the propeller to keep it turning, then it would sometimes fire back up again. (Somebody with the pilot's manual from the Collector's Edition could maybe post us a restart procedure??)
The best bet with these old girls is to treat them gently, and wait for Miss Schilling to bring out her "orifice mod"
