What happened
On 28 April 2011, a Yak-52, registration RA-3585K, was participating in a formation flying training school near Langford, Essex. The flight involved a series of manoeuvres, including a tailchase exercise. During the exercise, the aircraft broke away from the formation after the crew lost visual contact with the lead aircraft.
While attempting to rejoin the formation, the aircraft entered an inverted spin at approximately 1,800 ft agl. The spin lasted for at least three turns, during which the aircraft reached a low speed and a high angle of attack. Although the aircraft eventually recovered from the spin into an erect dive, it was at too low an altitude to avoid impacting the surface of a lake. The impact resulted in 2 fatalities and the total destruction of the aircraft.
The investigation
Investigators examined the wreckage, which was found submerged and inverted on the lake bed. The examination of the flight control systems, engine, and propeller showed no evidence of mechanical failure or pre-impact defects. The investigation also analysed video footage from a helmet camera, which showed the aircraft reaching a low speed and high angle of attack at the apex of a wingover manoeuvre.
Analysis of the flight instruments, specifically the gyro horizon and turn/bank indicator, suggested that the presentation of the instruments might have been confusing to the crew. Furthermore, the investigation looked into the training backgrounds of the occupants, noting that while the instructor was experienced, the student had limited experience in recovering from unusual attitudes or performing inverted spins in this specific aircraft type. The investigation also noted that the school's procedures for tailchase exercises allowed for a minimum height of 1,000 ft agl, which provided a very small margin for recovery.
Findings
- The aircraft entered an inverted spin due to pro-spin control inputs being applied at the apex of a wingover manoeuvre.
- The crew's lack of specific experience in recovering from inverted spins in the Yak-52 may have delayed effective recovery actions.
- The low altitude of the manoeuvre (1,800 ft agl) left insufficient margin for the crew to complete the recovery before impacting the water.
- Ambiguity regarding which occupant was in command of the aircraft may have hindered timely corrective action.
- The use of non-standard flight instruments may have contributed to pilot disorientation during the spin.