What happened
On April 13, 2002, a takeoff attempt involving a Christen A1 ‘Husky’, registration PH-KIS, and a Grob G103 C ‘Twin III Acro’ glider ended in an accident at Midden-Zeeland airfield. The operation was a glider tow, which initially proceeded normally. However, approximately 100 meters into the takeoff roll, the glider began drifting toward the rear left of the tug aircraft, while the PH-KIS drifted toward the right.
The pilot of the PH-KIS attempted to use opposite aileron to correct the drift, but the maneuver was ineffective because the aircraft's main wheels were still on the runway and the rudder lacked sufficient aerodynamic effectiveness due to the towing configuration. Believing the aircraft would reach the edge of the runway before liftoff, the pilot eventually decided to abort the takeoff. The tug aircraft rolled into an adjacent plowed field. As the aircraft slowed down in the soft, turned soil, the nose pitched forward, the propeller struck the ground, and the aircraft eventually flipped onto its back. The glider pilot, recognizing the danger, disconnected from the tow rope and rolled to a stop on the runway. Both pilots remained uninjured.
The investigation
Investigators examined the environmental conditions and the maneuverability of the aircraft during the tow. It was established that at the time of the incident, there was a left crosswind of approximately 18 knots. This exceeded the maximum demonstrated crosswind component of 15 mph (approximately 13 knots) specified in the flight manual for the Christen A1 ‘Husky’.
Findings
- The primary cause of the instability was the high crosswind component, which exceeded the aircraft's demonstrated limits.
- The glider pilot's ability to maintain position was severely limited because the pilot must focus on maintaining level wings and preventing premature altitude gain, leaving little margin for lateral corrections near the ground.
- The instability of the tow combination caused the PH-KIS to drift rightward relative to the glider.
- The decision to abort the takeoff led the aircraft into plowed earth, where the uneven surface caused the nose to pitch and the aircraft to overturn.