What happened
On December 2, 1979, a pilot conducted a test flight at the Fricktal-Schupfart airfield to evaluate the aerobatic capabilities of the DG 200 AR Acro Racer, registration D-7622. The primary objective of the flight was to investigate the aircraft's performance during inverted flight and to determine the optimal flap settings for such maneuvers.
During the flight, the pilot performed several aerobatic figures, including an inverted flight and a loop. While executing a powered loop, the aircraft reached a pitch angle of 70 to 80 degrees. At this point, the control stick began to vibrate. The pilot attempted to pull the stick back to prevent an aerodynamic stall, but the control column became jammed in the forward position.
Despite the inability to control pitch via the stick, the pilot managed to use the rudder and ailerons to level the wings and stabilize the aircraft in a high angle of attack. However, the aircraft soon entered an uncontrolled inverted spiral. At an altitude of approximately 350 meters and a speed of 200 km/h, the pilot initiated an emergency egress. While the canopy released easily, the pilot struggled significantly to release the safety harness under the high negative G-forces. Upon ejecting, the pilot's legs struck the forward canopy, tearing the windscreen and frame away. The parachute deployed at 100 meters, and the pilot landed slightly injured near the crash site, where the glider struck the ground in a flat, inverted position.
The investigation
Investigators examined the wreckage and the mechanical components of the control system. The investigation confirmed that the pilot was highly experienced in both powered and glider aerobatics and that no health issues contributed to the incident. The aircraft's weight and center of gravity were within permissible limits, and the weather conditions were favorable.
Technical analysis focused on the control column's movement. Forensic examination of the control linkage revealed that the mechanism was obstructed by a specific cable. Additionally, the investigation looked into the functionality of the cockpit safety equipment, specifically the Autoflug GL-2 harness buckle.
Findings
- The primary cause of the accident was the blockage of the control stick in the forward position caused by the rudder pedal adjustment cable.
- The improper arrangement of the rudder pedal adjustment cable prevented the pilot from recovering from the nose-down pitch.
- The Autoflug GL-2 harness buckle proved difficult to operate under high negative G-loads, requiring significant physical effort and the use of both hands to release.
- The pilot's extensive aerobatic training and preparation were critical in managing the emergency and surviving the ejection.