What happened
On October 19, 1996, a Piper PA-18-180, registration HB-ORW, was performing a test flight following a 100-hour inspection and minor repairs at Hausen am Albis airfield. The pilot, accompanied by a passenger acting as a data recorder, lined up on runway 27. The aircraft was configured with flaps retracted and the trim set in a slightly tail-heavy position.
Upon applying full power, the engine functioned normally. The pilot maintained a three-point stance using the control stick to keep the aircraft on the runway. However, as the aircraft lifted off, it began to veer sharply to the left. The pilot attempted to correct the deviation by pushing the stick forward to establish a normal climb attitude, but the aircraft failed to respond to these inputs. The plane continued to drift left, following a taxiway parallel to the runway, until it reached an altitude of approximately 15 meters. The pilot attempted to recover by reducing power and applying further corrections, but the left wing struck the ground heavily. The aircraft eventually came to a halt in a wet field roughly 80 meters left of the runway centerline.
The investigation
SUST examined the mechanical condition of the Piper PA-18-180 and the flight controls. The investigation of the airframe, including control cables, pulleys, bearings, and rudder connections, revealed no pre-existing defects that could have impaired control functions. The engine was found to have operated correctly, and propeller deformation suggested that power was low at the moment of impact.
The investigation also reviewed the environmental conditions, noting rainy weather, visibility of 8 km, and winds from 240 degrees at 9 knots with gusts up to 23 knots. The pilot's medical fitness and flight experience were also evaluated, noting that while the pilot was experienced, the aircraft lacked shoulder harnesses, which contributed to the pilot sustaining light head injuries during the impact.
Findings
- The primary cause of the accident was an inappropriate takeoff procedure.
- The pilot likely lifted off from the three-point position without sufficiently increasing speed or reducing the angle of attack.
- Because the aircraft was not yet at a high enough airspeed for effective control, aerodynamic forces from the propeller slipstream and engine torque caused a significant leftward drift.
- The tail-heavy trim setting further contributed to the difficulty in maintaining control during the rotation.
- The lack of shoulder harnesses in the aircraft meant the pilot's head struck the interior during the impact.