What happened
On July 2, 2022, at approximately 13:00 UTC, a Piper PA25-235 acting as a tug aircraft crashed into a corn field near the Maubray airfield in Belgium. The aircraft was performing a local aerotow operation, pulling a Schleicher Ka 6E sailplane. During the initial climb phase following takeoff, the sailplane pilot lost visual contact with the tug. In an attempt to correct the aircraft's attitude, the sailplane pilot initiated a descent, which inadvertently caused the sailplane to rise above the tug.
As the aircraft climbed, the tug pilot felt a significant vertical force on the tail. Although both the tug and sailplane pilots eventually released the tow cable, the maneuver had already induced a severe upset in the tug aircraft. The Piper PA25-235 entered a dive toward nearby trees at an altitude of approximately 200 feet. The pilot managed to level the aircraft just before impact, but the aircraft was destroyed upon hitting the ground and subsequently caught fire. The pilot of the tug aircraft escaped with minor injuries, while the sailplane pilot was unhurt and landed the glider safely back at the airfield.
The investigation
The AAIU(Be) conducted an extended investigation into the accident, examining the aircraft, the flight history, and the operational procedures. The investigation noted that the club was using a leased Piper PA25-235 as a temporary replacement for their regular Robin DR400 tug. While the pilot had performed training on this new type, the investigation focused on the transition between different engine powers and aircraft characteristics.
Investigators examined the equipment used, specifically the 40-meter nylon tow cable. They also reviewed the pre-flight briefings and the technical specifications of the Schleicher Ka 6E, noting that its all-moving elevator design can influence pitch stability and controllability during aerotow operations, especially when subjected to the propeller wash of a more powerful engine.
Findings
- The lack of situational awareness by the sailplane pilot allowed the unstable flight condition to develop.
- The tow cable was released by both pilots, but the timing was too late to prevent the tug aircraft from entering an upset state.
- The tug pilot's attention was divided between maintaining the flight path and monitoring the position of the sailplane.
- The specific combination of the Schleicher Ka 6E's flight characteristics and the increased propeller wash from the more powerful Piper PA25-235 increased the risk of a tug upset.
- The tow cable was not equipped with weak links that met the specifications defined in the sailplane's Pilot's Operating Handbook (POH).