Incident Overview
On April 13, 2013, an accident occurred at Sonderlandeplatz Lager Hammelburg (EDFJ) involving a Piper PA-18-135 tow plane and an Alexander Schleicher Ka 6 glider. The incident resulted in serious injury to the tow pilot and severe damage to the tow aircraft, while the glider sustained no damage and its pilot remained uninjured.
Sequence of Events
The single-seat Ka 6 glider took off behind the PA-18 on runway 28 at 15:11 local time. During the initial climb, the glider overflew the tow plane. The glider pilot pushed forward to regain position, causing the tow cable to slacken. When the cable tightened again, it accelerated the glider sharply, causing it to overfly the tow plane once more with a pendulum motion to the right.
The glider pilot attempted to reposition behind the PA-18 but failed. Being positioned above and laterally offset from the tow plane, the glider pilot could not release the cable because both hands were occupied pushing the control stick forward. The weak link in the 41-meter plastic tow cable broke.
The glider pilot executed two 180-degree turns at low altitude and landed safely on the airfield. Meanwhile, the PA-18 pilot reported that after takeoff, the nose dropped, placing the aircraft in a descent. He noticed the tail of his aircraft being pulled upward by the cable tension. Although he attempted to release the cable, the PA-18 impacted the ground approximately 15 meters to the right of runway 28.
Aircraft and Personnel Details
The Piper PA-18-135, built in 1954, was a two-seat shoulder-wing monoplane with a Lycoming O-290-D2 engine. It had a total time of 4,655 hours. The tow pilot was a 35-year-old private pilot with 328 total flight hours and over 200 hours on type. He held a valid towing endorsement without aerotow.
The Ka 6 glider, built in 1956, was a single-seat wooden shoulder-wing aircraft with a total time of 2,829 hours. The glider pilot was 52 years old with 110 total flight hours and 40 prior aerotow starts.
Investigation Findings
The German Federal Aviation Office (BFU) investigation found no technical defects in either aircraft. Both were within weight and balance limits. The tow coupling on the PA-18 was inspected by the manufacturer and found to meet airworthiness requirements. The weak link in the cable had broken as designed.
The accident is attributed to the glider pilot's inability to release the cable due to being out of position (above and behind the tow plane) while managing control inputs, leading to excessive tail-up attitude on the tow plane, which resulted in a stall and crash. The BFU noted that similar incidents have occurred previously when gliders overfly tow planes during takeoff.