What happened
On 15 June 2023, a JS-MD 3 glider, registration G-JSMD, was undergoing a private winch launch at Nymsfield Airfield in Gloucestershire. The weather conditions were fine with a light north-easterly wind. The pilot had secured his harness and prepared the aircraft with negative flap, intending to transition to positive flap as speed increased.
As the winch acceleration commenced, the pilot experienced a sensation of sliding backward in his seat, after which he lost memory of the subsequent flight sequence. Observers on the ground noted that while the initial ground run appeared standard, the aircraft performed a much more aggressive rotation than usual. This resulted in a steep climb, followed by a drop of the left wing. The aircraft entered a rolling and yawing motion to the left before impacting the ground in a steep, nose-down attitude. The impact destroyed the aircraft and resulted in one serious injury to the pilot.
The investigation
The investigation examined the aircraft's configuration and the pilot's physical experience during the launch. While the aircraft was confirmed to be within weight and balance limits, the impact damage prevented investigators from determining the exact flap setting at the moment of takeoff.
Following the pilot's report of sliding rearward in the cockpit, the British Gliding Association (BGA) coordinated with the manufacturer. The manufacturer's chief test pilot conducted trials under similar launch conditions and confirmed that the reclined seating position in this model could allow a pilot to slide backward during the high-acceleration phase of a winch launch. This movement was found to be possible even when the aircraft was controllable, though the test pilot noted that the phenomenon did not occur when restraints were tightly secured.
Findings
- The aircraft experienced a rapid pitch-up at the start of the launch.
- This aggressive rotation led to an aerodynamic stall.
- The resulting loss of control occurred at an altitude that left no opportunity for recovery.
- Inadequate pilot restraint contributed to the pilot sliding backward, potentially affecting control inputs.