What happened
On May 1, 2018, a Pilatus PC-12, registration PR-WBV, was performing a private flight from Angra dos Reis to São Paulo when the aircraft experienced a failure in its propeller pitch-control system during the descent phase. The malfunction caused the propeller to tend toward a feathered position, making it difficult for the crew to maintain engine performance.
In response to the failure, the crew attempted an emergency landing at the Gastão Madeira State Aerodrome (SDUB) in Ubatuba, São Paulo. During the landing attempt, the aircraft performed a maneuver to avoid an obstacle in the runway overshoot area but ultimately crashed in a swampy area near the threshold of runway 09. The impact resulted in substantial damage to the aircraft, including the separation of the empennage and structural failure of the wings. The Pilot in Command sustained serious injuries, while the Second in Command and two passengers suffered minor injuries. The remaining six passengers were uninjured.
The investigation
CENIPA's investigation focused on the mechanical failure of the propeller system and the crew's management of the emergency. Investigators examined the propeller components and found that the beta ring displacement was outside the manufacturer's specified limits, though it was unclear if this was caused by improper maintenance or the impact itself. The investigation also noted that the aircraft had previously been subject to an inspection regarding an intermittent ENGINE NP warning light, but was released for flight without a definitive root cause being identified.
Findings
- Propeller pitch-control failure: The primary cause was a malfunction in the propeller system that led to an unmanageable engine condition.
- Inadequate decision-making: The crew failed to properly assess flight parameters and runway constraints, attempting a landing at an airfield where the available runway length was insufficient for the aircraft's configuration.
- Reduced situational awareness: The crew struggled to recognize and organize the stimuli related to the propeller feathering, leading to a failure to evaluate all available emergency alternatives.
- Instruction and training deficiencies: The Second in Command lacked specific simulator training for such emergencies due to the aircraft's regulatory classification, and the Pilot in Command struggled to apply simulated emergency procedures to the real-world scenario.
- Inadequate technical documentation: The Aircraft Manual and Quick Reference Handbook (QRH) did not provide clear instructions for managing a propeller feathering event in flight, leaving the crew without sufficient guidance.
Safety action
CENIPA issued several recommendations to improve safety:
- To ANAC: Coordinate with Pilatus Aircraft Ltd. to assess the adequacy of procedures regarding the "ENGINE NP - In flight" warning.
- To ANAC: Review the maintenance supervision processes of the Synerjet do Brasil Maintenance Organization.
- To ANCA: Evaluate the necessity of requiring specific endorsements/training for pilots operating the PC-12 class of aircraft.