What happened
On June 7, 1961, a Pilatus Porter PC-6, registration HB-FAT, operated by Motorfluggruppe Zürich, attempted a commercial passenger flight at Kloten Airport. The aircraft was carrying 7 passengers when it began its takeoff roll on runway 28. During the initial phase of the takeoff, the aircraft's nose pitched downward, causing the propeller to strike the runway surface. Simultaneously, the aircraft veered sharply to the right. The aircraft traveled approximately 150 meters before coming to a stop after rotating roughly 150 degrees from the runway centerline. There were no fatalities or injuries during the incident, though the aircraft sustained significant damage.
The investigation
The investigation examined the pilot's pre-flight procedures and the mechanical state of the aircraft. It was established that the pilot had taken over the aircraft at 14:05 and proceeded to start the engine without utilizing the onboard checklist. This omission led to the pilot failing to notice that the combined control lock, which secures both the control column and the rudder, remained engaged.
Investigators also conducted a reconstruction of the taxi phase to determine how the aircraft's maneuverability was affected by the locked controls. The investigation noted that the engine was running unevenly at low RPM, prompting the pilot to increase power to approximately 1600 RPM, which necessitated constant braking. Additionally, evidence of a light braking skid on the right wheel suggested the pilot may have been applying right rudder or braking to counteract the engine's torque, contributing to the rightward veer.
Findings
- The primary cause of the accident was the failure to disengage the control column lock due to inadequate pre-flight checks.
- The pilot did not use the official checklist during the initial engine start or the subsequent taxi to the holding point.
- The aircraft's nose pitched down and the propeller struck the pavement because the controls were restricted.
- The aircraft veered right, potentially exacerbated by the pilot's attempts to manage engine torque through braking and rudder input.