AA62 - I can't throw any light on your Kai Tak incident but it brought to mind an incident 'somewhere in the Caribbean' when a Hastings struck a ground power unit while on an engine run. During the ground run the aircraft performed a partial pirouette and delivered a sharp whack (or several!) to the GPU that resulted in a lack of voltage, a consequent prop change and shock load test to the engine. All this took several days due to the exotic location, not that the crew were too upset.