1966 Chipmunk Accident at Amlikon Airfield (HB-TUB)

Incident Overview and Aircraft Details On May 22, 1966, a de Havilland Chipmunk, registration HB-TUB, was involved in an accident at the Amlikon airfield in Thurgau, Switzerland. The aircraft, a single-engine, two-seat low-wing monoplane with fixed landing gear and a tail wheel, was built in 1956 and powered by a 140 hp Gipsy Major C 1 MK-22 engine. It was privately owned but held by the Segelfluggruppe Cumulus of the Thurgau section of the AeCS. The aircraft was equipped for aerotowing operations. ## Operational Context and Sequence of Events The accident occurred during active glider operations at the airfield, which featured an 800-meter runway. Prior to the incident, a winch launch of a Meise glider (HB-514) had failed when its weak link broke at approximately 40 meters altitude, requiring an immediate landing. While the Meise was being recovered, preparations began for a tow launch involving the Chipmunk and a Blanik L 13 glider (HB-838). The presence of the recovering Meise on the mowed strip forced the tow combination to veer right during the initial takeoff roll to avoid a collision. This maneuver caused the Chipmunk to roll over a winch cable that had been laid on the runway. The cable, approximately 1,000 meters long and weighing about 80 kg, became entangled with the Chipmunk's tail wheel. ## Pilot Actions and Crash The glider pilot, observing the entanglement, immediately released the tow line and landed the glider safely. The Chipmunk pilot, unaware of the cable, continued the climb. At approximately 10 meters altitude, he noticed the glider was no longer in tow and released the loose tow line. He then attempted to turn right to land, but the drag from the trailing winch cable severely degraded the aircraft's performance. As the cable wrapped around a group of trees during the turn, the drag increased significantly. The pilot initiated an emergency landing in open terrain. The aircraft lost speed rapidly and crashed from a height of 3 to 5 meters. The pilot was uninjured. ## Damage and Investigation The accident caused damage to the left landing gear leg and the left wing of the Chipmunk, with estimated repair costs of 8,000 Swiss Francs. A broken fence was the only other reported damage. The investigation concluded that the accident was caused by the winch cable becoming entangled with the tail wheel during the launch, a result of the disrupted operational rhythm and the pilot's lack of awareness of the cable's presence on the runway.