I kind of thought the Eastern L-188's had APUs in the tail. There was an exhaust port there with a screen over it. We were told that was to protect the APUs from 250 kt. birds flying into your rear. Maybe they were removed at some time. I have a friend at United who said they windmill started a Viscount engine at the gate with propwash from a DC-6 ( or 7 or Connie maybe ). They used ropes wrapped around the prop hubs on DC-3s also. As co-pilot on a CV 440 we checked the auto-feather of each P & W R-2800 on taxi out. You let the RPM drop a little and disarmed it did the other engine. One night at DCA, I let the RPM get a little low doing this and both engines loaded up and quit. As we coasted to a halt in front of the Atlantac Aviation ramp. The very gruff Captain said: "Gee, that never happened to me before". Ground control said: "Eastern continue taxiing...........Oh, I see you've lost them both". The ships battery was never kept in good enough condition to start those big engines and we barely got a call off to operations for a power cart as the battery voltage charged downwards from 24 v. It took them 1/2 an hour to get us started again. Miraculously I didn't get bawled out by the Captain.
A Buffalo Air DC 4 froze one night in the far north after the ground electric engine heaters tripped a circuit breaker and no one noticed until morning. They couldn't unfreeze them with the electric heaters and had to fly in a big Janitrol space heater.