What happened
On 12 June 2015, during a busy race day at Ronaldsway Airport, Isle of Man, a collision occurred between two light aircraft on Taxiway D. Due to high traffic volumes, the taxiway had been temporarily reclassified as an apron, with roughly 70 aircraft parked on the grass verges.
The Grumman AA-5 Traveller, registration G-BBSA, was positioned with its nosewheel on the taxiway and mainwheels on the grass edge. The pilot had moved the aircraft forward to avoid the uneven grass surface before starting the engine. While waiting to contact the Tower for clearance, the pilot observed a Cessna 182F G-WARP taxiing toward him. Realising a collision was imminent, the pilot attempted to shut down the engine, but the rotating propeller struck the passing aircraft.
The pilot of G-WARP reported that he had positioned his aircraft two metres left of the centerline, believing there was enough clearance to pass both the parked aircraft on the left and the G-BBSA on the right. The pilot of G-WARP noted that the engine on G-BBSA did not appear to be running as he passed.
There were no injuries to the occupants of either aircraft. The collision resulted in the right wingtip and aileron of G-WARP being severed by approximately 0.3 metres, while G-BBSA sustained propeller damage and a suspected engine shock-load.
The investigation
Investigators examined the positioning of both aircraft and the operational environment at the airport. The investigation established that the pilot of G-BBSA had started the engine while the aircraft was partially on the taxiway to avoid the uneven grass. The investigation also reviewed the movements of G-WARP as it navigated the crowded apron area during a period of high activity.