Event Summary
On 15 January 2012 at 1114 UTC, a Yak-52 aircraft, registration G-LYFA, was involved in a ground accident at Manchester Barton Airfield during taxi. The aircraft, powered by one Ivchenko Vedeneyev M-14P piston engine and manufactured in 1982, was being operated on a private flight with two crew members on board and no passengers. Neither crew member was injured. The aircraft sustained damage to its propeller and engine cowling, and the airfield building suffered minor damage, including light scoring from the propeller and a broken window sill.
Details of the Event
The aircraft had been parked on a grass area and was prepared for flight after approximately eight weeks of inactivity. After engine start and a warm-up period, the pilot increased power to begin taxiing. Both occupants were qualified on the Yak-52 and were members of the same group. Upon reaching the hard taxiway surface, the aircraft rolled forward freely at idle power. When the pilot applied left rudder and brake to initiate a turn, the aircraft did not respond. Further brake applications produced no braking effect, and the aircraft continued rolling straight forward toward an airfield building located 14 m from its parked position. The pilot switched off the magnetos to stop the engine, while the rear-seat pilot closed the fuel switch. The aircraft rolled into the building at slow speed with the propeller still turning. After ensuring the aircraft was correctly shut down, both occupants vacated. The aircraft was later pushed back to its parking position.
Findings
A subsequent inspection by the aircraft's maintenance organisation revealed four leaks in the undercarriage 'down' line of the pneumatic system. As this line also supplied the pneumatically operated brake units, the leaks were established as the reason for the loss of braking. The commander held a Private Pilot's Licence, was 47 years old, and had a total flying experience of 290 hours, of which 64 were on the Yak-52. In the previous 90 days, he had flown 1 hour. The accident was reported by the pilot and the aircraft maintenance organisation.
Probable Cause
The loss of braking was caused by four leaks in the pneumatic system's undercarriage down line, which also fed the brake units.