Incident Overview
A pilot was conducting an agricultural application flight, spreading fertilizer over a pine tree area, when a loud bang was heard during a turn. Simultaneously, the pilot lost tail rotor authority. The pilot attempted to level the helicopter and settled it into the trees. The helicopter came to rest upright on its skids.
Post-Accident Examination
Following the incident, an examination of the helicopter was conducted. Flight control continuity was established for both the cyclic and collective controls. The tail rotor blades exhibited leading edge damage on both blades. The lower fuselage was found to be buckled, and the rear housing of the tail rotor gearbox transmission was broken and cracked.
Tail Rotor Gearbox Analysis
The tail rotor assembly was examined in detail. Fracture features on the case assembly were consistent with an overload event. Wear patterns on the bevel gear teeth within the gearbox indicated that they had been forced apart during the incident.
Component Condition
Examination of the components revealed no indications of any pre-existing conditions that would suggest a failure before the tail rotor strike. The damage observed was determined to be the result of the overload event during the forced landing.