History of Flight
On 5 January 2003, a Yak-52 (registration G-YAKW) departed Turweston Airfield at 1110 UTC with a pilot and passenger. The pilot informed the air-ground radio operator of plans to perform aerobatics for approximately 30 minutes before returning. The aircraft was observed maneuvering two miles northeast of Towcester, Northamptonshire. After a sequence of aerobatic maneuvers lasting about 10 minutes, the aircraft entered a vertical climb, executed a stall turn, and then descended vertically. There was no apparent recovery, and the aircraft impacted the ground beneath power lines. Rescue services arrived 15 minutes later; both occupants were fatally injured.
Witness Evidence
Multiple witnesses observed the aircraft performing vertical and horizontal aerobatics at altitudes not considered unusually low. The highest point of the final maneuver was approximately 3,000 feet above ground level. The final descent was described as stable, with the possibility of three slow rotations before the descent was obscured by trees.
Wreckage Examination
The aircraft was recovered to the AAIB for detailed examination. During inspection of the aft fuselage, investigators discovered that the elevator control surfaces could move freely in the nose-down direction but could not move beyond neutral in the nose-up direction. Examination of the aperture at the base of the tail revealed a restriction: a small, short-handled flat-bladed screwdriver had become impaled on the swaged end of the lower elevator cable at its attachment to the aft quadrant assembly. This jammed the elevator control, preventing nose-up movement.
Aircraft and Maintenance Information
The Yak-52 is a low-wing monoplane with tandem cockpits, powered by a single Ivchenko Vedeneyev M-14P piston engine. The aircraft was manufactured in 1985. The internal fuselage is open from the forward firewall to the tail, with control cables and components exposed. A trainee mechanic at the maintenance facility that performed recent work on the aircraft reported losing a screwdriver matching the item found.
Probable Cause
The screwdriver jammed the elevator control such that the elevator control surface could not be moved beyond neutral in the nose-up direction, preventing recovery from the vertical dive.