Worked on the ramp for Servisair at MAN for a summer in the 80s, and one day was despatching a Connectair Shorts 330. Everything went fine, so stood waiting for him to taxi off after the doors closed. However the Captain seemed to have trouble starting No1 engine, and after several attempts I saw him walking down the aisle, so wandered over to see what the problem was. I was a bit puzzled to see him clutching the ship's axe, but as he just wanted some engineering steps I assumed he hadn't flipped!
Imagine how far my jaw dropped when he climbed on the wing, and proceeded to belt the engine a couple of time with the blunt side of the axe (add 6 inches and that's how far the passengers' jaws dropped, looking through the window!). 'Should be fine now' said the Captain as he got back on board and shut the door - sure enough everything roared into life and he departed.
I'd heard of hitting a car's starter motor to free it, but this was a new one on me!! Could explain the thumping noise though!!!