What happened
On 20 May 2010, a Piper PA-42-1000, registration N313PC, was performing a ferry flight from Xanxerê to Jundiaí. During the descent, the crew noticed that the left engine power lever had become stiff and was stuck between 40% and 50% power. Although the crew declared an emergency as a precaution, they continued the descent because engine parameters remained normal. Prior to landing, the crew had briefed that the engines would be shut down immediately upon touchdown to avoid complications.
Upon touchdown at Jundiaí Aerodrome, the copilot requested reverse thrust. As the pilot applied the reversers, the aircraft experienced an abrupt yaw to the right and exited the runway, eventually colliding with an obstacle in a ravine. Both crew members escaped the substantial damage to the aircraft without injury.
The investigation
CENIPA investigators examined the wreckage and the control systems of the aircraft. The investigation revealed that during the application of reverse thrust, the activation rod of the left engine power lever broke. This failure created a condition of asymmetric thrust. Inspection of the propeller assemblies showed that the right engine was in a reverse thrust setting, while the left engine had not transitioned to reverse.
Investigators also noted a discrepancy in cockpit coordination. Despite the pre-landing briefing to shut down the engines, the crew applied reverse thrust. The pilot attempted to regain control using brakes and rudder inputs but maintained the power levers in the full rear (reverse) position, which exacerbated the asymmetry.
Findings
- The primary cause of the loss of control was the asymmetric thrust resulting from the broken power lever activation rod on the left engine.
- A contributing factor was the failure in cockpit coordination, as the crew did not follow the established briefing to shut down the engines, instead requesting reverse thrust due to a probable conditioned reflex.
- The pilot's decision to maintain the power levers in the reverse position while attempting to control the aircraft with brakes and pedals contributed to the excursion.
- The investigation could not definitively determine if the breakage was due to material fatigue or a maintenance deficiency, though the engine was 150 hours away from a scheduled overhaul.
Safety action
CENIPA issued several safety recommendations, including:
- A request for the National Civil Aviation Agency to evaluate the necessity of additional inspections for teleflex cables used in propeller and power control.
- A recommendation for operators to emphasize the importance of risk assessment and choosing compatible infrastructure during technical emergencies.
- A recommendation to the aerodrome authority to remove termite mounds and erosion ditches from the runway vicinity.