What happened
On August 2, 2024, a Bell 407, registration N20BH, was involved in an accident near Raft River, Idaho. The helicopter was operating in support of the United States Forest Service, transporting three Helitack crew members from Gerlach, Nevada, to Pocatello, Idaho, with stops in Winnemucca and Elko, Nevada.
During the final leg of the flight, approximately 55 minutes after departing Elko, the pilot noticed the barrier inlet air filter light flickering. After the light remained illuminated, the pilot engaged the filter bypass system. Shortly thereafter, the pilot observed the engine Measured Gas Temperature (MGT) gauge rising into the yellow band.
In an attempt to manage the temperature, the pilot reduced power and began a descent. However, the MGT continued to rise, eventually exceeding the redline of 779° C while the aircraft was between 1,000 and 1,500 feet. While the pilot was searching for a landing site, the engine indicated an overspeed condition. After attempting to arrest the overspeed by raising the collective twice without success, the pilot initiated an autorotation into a nearby corn field. Because the height of the corn was unknown, the pilot could not accurately judge the timing for the final pitch pull, resulting in the helicopter dropping approximately 5 feet and landing hard.
All four occupants sustained 4 minor injuries and 0 fatalities. During the impact, the main rotor transmission assembly separated from the airframe and fell into the cabin compartment. All individuals were able to exit the aircraft on their own.