On September 15, 2024, about 1700 mountain daylight time, a Robinson Helicopter Inc R-44 II, N233WT, was substantially damaged when it was involved in an accident near Basin, Montana. The pilot and 2 passengers sustained serious injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that after taking off from mountainous terrain and reaching an altitude about treetop level, the helicopter began to lose engine and rotor rpm. The pilot immediately nosed the helicopter down, attempted to maneuver the helicopter around trees, however, it descended, struck trees, and impacted the ground. Postaccident examination of the helicopter revealed the fuselage and drivetrain were substantially damaged. The helicopter was relocated to a secure facility for further examination.