What happened
On August 4, 1962, a De Havilland DH-82A Tiger Moth, registration HB-UBF, departed from the Herten airfield near Rheinfelden. The flight, operated by a private pilot accompanied by one passenger, was intended to fly toward Bohlhof for glider towing operations. During the climb, at an altitude of approximately 200 to 300 meters, the aircraft entered a left-hand turn. The aircraft subsequently entered a spin, losing altitude rapidly before impacting a dense young forest south of the Rhine river near Möhlin. The impact was mitigated by the tree canopy, but the aircraft was destroyed. Both occupants sustained serious injuries.
The investigation
The investigation examined the aircraft's mechanical condition, the fuel used, and the flight parameters leading to the accident. Investigators found that the engine was operating at high RPM at the moment of impact, and the airspeed indicator in the passenger seat was stuck at 46 knots, which was above the redline limit. The investigation also noted that the aircraft's center of gravity was 43 cm behind the reference point, which exceeded the permitted limit of 42 cm. This shift was caused by the addition of 14 kg of towing equipment in the luggage compartment. Additionally, the pilot had been using automotive gasoline instead of the required aviation gasoline, though the fuel's octane rating was found to be sufficient.
Findings
- The aircraft entered a spin during the climb.
- The loss of airspeed was the most likely primary cause of the transition into a spin.
- The aircraft's center of gravity was outside the allowable range due to the weight of the towing equipment.
- The pilot's recovery attempt, specifically the use of elevator input, likely contributed to the continuation of the spin into the trees.