Background
On 9 October 2015 at 1600 UTC, a ground collision occurred between two aircraft in the maintenance area of Wycombe Air Park, Buckinghamshire. The aircraft involved were a Socata TB21, registration N377C, built in 2005, and a Cessna 152, registration G-WACF, built in 1980. Both were single-engine piston aircraft: the TB21 powered by a Lycoming T10-540-AB1AD engine and the Cessna 152 by a Lycoming O-235-L2C engine.
The TB21 was on a private flight with one pilot and one passenger; the Cessna 152 was on a training flight with two pilots (crew) and no passengers. Neither pilot nor any passenger was injured. The maintenance area formed a cul-de-sac bounded by four hangars, with entry and exit on the east side. This area was not under air traffic control (ATC) jurisdiction; pilots only needed taxi clearance when entering the aircraft manoeuvring area.
Collision Sequence
The pilot of N377C reported that after parking outside a maintenance hangar and shutting down the engine, a ground engineer approached and made hand and mouth movements indicating the aircraft should be moved. Believing there was urgency, the pilot interpreted the signals as a request to perform a 180-degree turn and taxi further into the cul-de-sac. After checking the area was clear, he began the turn. After approximately 130 degrees of rotation, his passenger alerted him to an aircraft approaching from the right. The pilot stopped just as the left wing of G-WACF passed over his right wing and struck his propeller.
The pilot of G-WACF reported that after landing, he was cleared to taxi to the apron and then to the hangars. His taxi light and anti-collision beacon were illuminated as he entered the maintenance area. He observed N377C parked near a hangar door and saw a ground engineer gesturing to its pilot. He taxied slowly past N377C and then stopped to allow ground crew to move another aircraft. Shortly after stopping, he felt a slight impact through the control column and noticed a sharp increase in noise before realising his left wingtip had been struck by N377C's propeller.
The engineer reported that it was end of day, and flying school aircraft were being moved into the hangar. He saw N377C taxi into the cul-de-sac, turn back toward the apron, and park outside the hangar. He attracted the pilot's attention and gestured for him to move forward to clear the hangar front. Although a PA-28 was parked ahead, the engineer believed there was enough room for a 25-30-foot forward taxi. N377C moved forward and turned back into the cul-de-sac; during this manoeuvre, its propeller struck the left wingtip of G-WACF, which was taxiing into the cul-de-sac.
ATC personnel reported that the collision occurred behind them. They first became aware of it when they heard a loud bang and turned to see debris from G-WACF's wing on the ground.
Damage
The propeller of N377C and the left wingtip of G-WACF were damaged. Neither pilot nor any passenger sustained injuries.