What happened
On 4 September 2007, a Yak-50, registration G-IIYK, was involved in a ground accident at Lee-on-Solent, Hampshire. After landing on Runway 23, the pilot taxied the aircraft to a tarmac area near a hangar, a low wall, and a fuel bow and bowser.
During the taxi, the pilot attempted to turn the aircraft using differential braking. To assist with the recharge of the aircraft's pneumatic systems, the pilot closed the cockpit ventilation air valve. As the pilot moved their hand from the cockpit air switch to the magneto switch, the sleeve of their flying suit caught the throttle. This action caused an unintended application of full power.
Despite the pilot immediately closing the throttle, the aircraft continued to accelerate forward. The aircraft passed through a gap in the low wall, causing the wings to strike the wall, and subsequently collided with the cab of the fuel bowser. The propeller struck the windscreen of the bowser cab, resulting in substantial damage to the engine, cowlings, fuselage, and wings. The pilot exited the aircraft without injury.
The investigation
The investigation examined the pneumatic systems of the Yak-50, which utilizes compressed air for engine start, landing gear retraction, and wheel braking. The investigation noted that the pilot had observed a slower than normal recharge rate for the air pressure during the taxi.
While the pilot suggested a potential leak in the landing gear air system might have contributed to a loss of braking effectiveness, the physical evidence and sequence of events focused on the mechanical interaction between the pilot's clothing and the flight controls.