What happened
On 22 April 2007, at approximately 12:27Z, two Yak 52 aircraft were involved in a ground collision at Virginia Aerodrome. The incident occurred while a flight of three aircraft was taxiing toward the holding point of Runway 2/23 to begin aerobatic training. The third aircraft in the formation, ZU-WAN, was taxiing toward the two preceding aircraft when the pilot attempted to decelerate. Upon applying the brakes, the pilot discovered the system was ineffective due to a lack of air pressure. Consequently, ZU-WAN was unable to stop and struck the stationary aircraft, ZU-CWL, from behind. There were no injuries to either pilot, though both aircraft sustained damage. ZU-CWL suffered damage to its left horizontal stabilizer and elevator, while ZU-WAN sustained damage to its propeller.
The investigation
The investigation examined the mechanical operation of the aircraft's braking system and the regulatory status of the involved aircraft. The Yak 52 utilizes a pneumatic braking design where air pressure is directed to wheel bladders via a lever on the control column. Investigators looked into whether mechanical failure or pilot error was responsible for the loss of pressure. Additionally, the investigation reviewed the maintenance records of the Aircraft Maintenance Organisation (AMO) responsible for the most recent annual inspections, finding the AMO held valid approval at the time. The investigation also noted the regulatory status of the aircraft's flight authorization.
Findings
- The primary cause of the collision was the failure to engage the air system master valve, which resulted in a lack of air pressure necessary to operate the brakes.
- The pilot of ZU-WAN lacked sufficient familiarity and experience with the specific operation of the pneumatic brake system.
- The Authority to Fly for ZU-CWL had expired on 24 January 2006, which was a violation of the Civil Aviation Regulations of 1997.
- Meteorological conditions were clear with good visibility (CAVOK) and were not a contributing factor.
- Both aircraft had been maintained by an approved maintenance organization.