How fast can an athlete move and plug the EXT PWR cable?

[John H Watson]

Do crews always shut down at least one engine when waiting for external services (power, bleed, aircon)?

Well, we never connected bleed or conditioned air with the engines running (on arrival). Too risky. The cabin remains fairly cool for 5 minutes after the packs have been turned off anyway.

I've seen everything from no engines shut down to 3 engines shut down before external power is applied. I've only seen 1 engine only running on a freighter though. One engine might have trouble running all the electrical systems on a passenger aircraft.