Accident Details
On 28 August 1999, a glider experienced an accident during a winch launch at Schönhagen. The aircraft was a PZL-Bielsko SZD-50-3 "Puchacz" glider. The pilot sustained serious injuries, and the glider was destroyed. Forest damage occurred.
Flight History
During a training flight, the winch cable tension decreased. The glider entered a spin and struck wooded terrain. According to the investigation, at an altitude of approximately 150 m above ground, the climb angle decreased. The aircraft suddenly banked left over the left wing and entered a spin-like condition. The flight instructor radioed commands to release the tow rope and recover from the spin, but no reaction from the student was observed. After several turns, the glider impacted a pine forest about 100 m from the runway. The tow rope had released shortly before impact.
Pilot and Winch Operator Information
The 76-year-old student pilot reported a brief tension loss at 40-50 m above ground, after which the winch pulled again. At 100-150 m, tension dropped again, with the airspeed indicator showing about 60 km/h. The student had been training since October 1996 with a total flight experience of approximately 36 hours, of which about 30 hours were on the SZD-50-3 type. The winch operator had held the required license since 24 July 1999. On the day of the accident, he had performed three launches; the first two were normal. On the third, at about 150 m, engine power suddenly decreased while the throttle remained at full. The tow rope began to sag, and the glider entered an uncontrolled attitude. The operator reported no prior indication of power loss.
Technical Findings
No technical defects were found on the glider. The winch, a Herkules H 4, initially would not start during a test run. Examination revealed that the emergency stop lever, located on the rear wall between the two seats, was partially in the "off" position, and its wire safety was open. After moving the lever to the normal position, the winch started and ran without issue. Repeated tests showed varying degrees of RPM reduction when the lever was moved toward the "off" position.
Environmental Conditions
Visibility was good. Wind was from 300° at approximately 5 knots.
Performance Characteristics
The SZD-50-3 "Puchacz" loses about 80 m of altitude per spin turn and requires about half a turn to recover from a spin, depending on the center of gravity and pitch attitude. Given that the glider entered a spin at 100-150 m above ground, even immediate and correct recovery offered only a small chance of avoiding the accident.
Probable Cause
The accident resulted from: the winch cable tension decreasing due to adjustment of the emergency stop lever; the pilot not deciding to abort the launch in a timely manner; and the pilot not pushing forward, causing the glider to enter a stalled condition.