What happened
During the execution of an aerial application mission, the aircraft was engaged in its third run when a critical mechanical failure occurred. The main transmission seized unexpectedly, causing an immediate loss of propulsion control. The pilot attempted to manage the emergency by trying to gain sufficient altitude to execute a safe landing; however, the aircraft was unable to climb effectively. Consequently, the helicopter descended uncontrollably and impacted a wooded area.
The investigation
Following the accident, investigators conducted a detailed examination of the failed transmission components. The forensic analysis revealed that the internal lubrication system had failed. Specifically, the oil supply nozzle responsible for delivering lubricant to the transmission was found to be plugged. This blockage prevented the necessary flow of oil, leading to insufficient lubrication of the gears and subsequent mechanical seizure.
Findings
The primary factor contributing to the accident was the mechanical failure of the transmission due to lack of lubrication. The plugged oil supply nozzle directly caused the gears to seize, which rendered the aircraft uncontrollable. The pilot's inability to gain altitude was a direct result of this mechanical failure rather than operational error.