The document reportedly states that the pilot "was unable to control engine rpm with throttle inputs", which TMZ translates to mean "the engine was not responding to the throttle inputs, so the pilot on the doomed aircraft had lost control".
Eventually, he opted to turn off the engine and perform an autorotation, something he'd successfully done multiple times in the past.
Troy Gentry, best known as part of the country music duo Montgomery Gentry, will be remembered Thursday morning with a celebration of life at the Grand Ole Opry House in Nashville. Earlier on September 8, Robinson had taken the helicopter out for a 1.2-hour flight.
Autorotations are frequently used in cases of engine failure, and use air moving up through the rotor during descent to power the helicopter's blades, essentially allowing it to glide to the ground.
Robinson died upon impact.
The Montgomery Gentry concert was canceled soon after the crash, before it was revealed Troy was one of the men killed.
Twisted metal and the rotor of the chopper could be seen strewn throughout the grass in Medford.
Chris Stapleton paid tribute fellow Kentucky country artist Troy Gentry Friday night playing the Montgomery Gentry hit "Hillbilly Shoes" during his show at Cincinnati's Riverbend. Gentry hailed from Lexington.
"Toward the end of the video, the descent profile became more vertical and the rate of the descent increased before the helicopter descended out of view", the report said.