What happened
On August 25, 2004, at 12:45 local time, a Piper PA-25-235 Pawnee, registration F-GHSX, was performing a glider tow at Mont-Louis aerodrome. During the takeoff roll on runway 14, the towed Schleicher KA 6E glider moved erratically relative to the tow plane, passing above, then below, and finally above the aircraft again. During this sequence, the tow cable disconnected from both the glider and the tow plane. Following the disconnection, the tow plane entered a steep dive and struck the ground near the threshold of runway 32. The glider pilot executed a right turn and landed on the grass strip adjacent to runway 32.
The investigation
The investigation focused on the flight dynamics of the tow and the experience levels of the crew. The glider pilot reported being caught off guard by the high climb rate of the Piper PA-25-235, which caused him to lose visual contact with the tow plane twice. Witnesses observed that the glider pilot deployed air brakes and began a right turn before the cable actually detached.
Technical examination revealed that both the aircraft and the glider were equipped with Tost brand hooks. The glider's hook, located near its center of gravity, was slightly offset and featured an automatic release system. The investigation also noted that the pilots did not utilize radio communication during the takeoff phase. Furthermore, the glider pilot had significant time away from this specific aircraft type, having not flown the Schleicher KA 6E since August 2003, and this was only his second tow using a high-performance aircraft like the PA-25.
Findings
- The primary cause of the accident was the pilot's failure to adequately account for the specific characteristics of the tow attachment during the climb.
- The glider pilot experienced significant stress due to the pressure of performing a solo flight following a period of infrequent flight on this specific model.
- The high performance of the tow plane caused the glider to climb more rapidly than anticipated, leading to unstable positioning and the eventual loss of the tow connection.