Flight Sequence
On 19 October 1996, at approximately 1345 local time, the pilot of the Piper PA-18-180, registration HB-ORW, conducted a control flight from Hausen am Albis airfield. The aircraft was positioned on runway 27 with flaps retracted and the trim set slightly tail-heavy. After applying full power, the pilot noted normal engine operation. The aircraft began its takeoff roll in a three-point attitude and lifted off after a short distance. Shortly after becoming airborne, the aircraft drifted left. The pilot, who had initially held the control stick aft, attempted to lower the nose for a normal climb attitude, but the aircraft did not respond and continued turning left, climbing to about 15 meters above ground. Despite reducing power and making further control inputs, the pilot could not prevent the left wing from striking the ground. The aircraft cartwheeled over the nose and right wing, coming to rest approximately 225 meters from the runway threshold and 80 meters left of the runway axis in wet grassland. Both the pilot and passenger were lightly injured; the pilot sustained minor head injuries.
Findings
- The pilot held a valid private pilot license with a total of 1195 flight hours, including 195 hours on the accident type. Recent flight training was adequate.
- The passenger, who assisted with maintenance, occupied the rear seat and was preparing to record data on a metal clipboard. No interference with controls occurred.
- The aircraft was airworthy with proper maintenance intervals. It was not equipped with shoulder harnesses.
- Weight and balance were within prescribed limits.
- The trim was set slightly tail-heavy (horizontal stabilizer position at approximately 60% of its range).
- Examination of the flight controls, cables, pulleys, bearings, and rudder connections revealed no pre-existing defects that could impair control function.
- The engine operated normally. Propeller deformation and ground marks indicated low engine power at impact.
- Impact occurred 225 m from the runway start, projected onto the runway axis.
- The calculated takeoff distance over a 15 m obstacle for a normal takeoff was approximately 205 m.
- Weather: rainy, visibility 8 km, wind from 240° at 9 kt with gusts to 23 kt.
Assessment
Initial investigation focused on a possible technical defect because the pilot reported no response to control inputs. However, the entire control system showed no pre-existing anomalies. The assessment thus turned to operational aspects. The aircraft, primarily used for glider towing, had ample power (132 kW/180 hp). On hard surfaces, takeoff roll without a tow is very short. For tailwheel aircraft, a three-point attitude at the start of the roll is necessary for directional control until sufficient speed provides adequate control authority. The pilot initially held the stick aft, maintaining positive ground control. However, he apparently did not reduce the angle of attack early enough before liftoff to increase speed further, preventing a proper takeoff. The aircraft most likely lifted off from the three-point attitude while not fully airworthy. Propeller slipstream induced aerodynamic forces caused a left drift, and engine torque induced a left roll. The pilot could not counter these effects. The aircraft continued climbing in that state to about treetop height before stalling over the left wing. The tail-heavy trim setting exacerbated the situation. In glider towing, the tow load provides stabilization, slowing the takeoff and tending to lift the tail. The absence of shoulder harnesses contributed to the pilot's head injuries, which could have been more serious.
Probable Cause
The accident was caused by an inappropriate takeoff procedure.