What happened
On August 10, 2024, a Pilatus PC-6/B2-H4 Turbo Porter, registered D-FOGO, was conducting scheduled skydiving operations out of Portimão, Portugal. After completing five successful flights, the aircraft departed for a final mission carrying a pilot and seven passengers (including three tandem pairs and one camera operator). The aircraft climbed to flight level 150 before releasing the skydivers.
During the subsequent descent to FL100, while flying over the Portimão marina, the pilot experienced a sudden nose-down attitude. The pilot attempted to counteract the movement by pulling the control stick with both hands. For approximately 50 seconds, the aircraft underwent a severe upset, transitioning from a pronounced nose-down attitude to inverted flight. During this period, the pilot maintained radio transmission, broadcasting a distress message. Data from FlightRadar24 and NAV Portugal confirmed the erratic flight path.
After regaining control and leveling the wings, the pilot reported a loss of engine power. Despite attempts to restart the engine, the aircraft continued its descent without power, eventually landing on runway 11. The aircraft sustained minor damage, including the separation of wing access covers on both sides.
The investigation
The GPIAAF investigation involved coordination with the operator, Treino Avançado, and the Swiss Transportation Safety Investigation Board (STSB). A physical inspection of the aircraft was conducted by a technical adviser appointed by the manufacturer. The investigation examined maintenance records, pilot experience, and the aircraft's technical history.
Findings
- The pilot was highly experienced, with 22,800 total flight hours, 670 on type.
- The aircraft was airworthy at the time of dispatch.
- The investigation identified recent and long-standing failures of the pitch trim system that had not been properly recorded in the official technical logs.
- Maintenance actions were performed that were not specified in the maintenance manual, such as the unapproved application of lubricant spray.
- The operator lacked a structural damage registration system (dent and buckle chart) at the time of the event.
- There is an ongoing industry-wide concern regarding Pitch Trim Runaway in this aircraft model; EASA has recently mandated the replacement of relays at 2,500 flight hours following similar investigations.
Safety action
- Safety Recommendation PT.SIA 2025-12: The operator must evaluate its aircraft Technical Logbook System to improve the reporting and control of aircraft defects and maintenance actions, ensuring all anomalies are properly documented and corrected by certified entities.