20180825015309A

The helicopter was conducting water dropping activities in support of a U.S. Forest service fire fighting operation, under an exclusive use contract. A 150 ft synthetic longline and a 240 gallon bambi flexible water bucket was attached to the cargo hook. The pilot indicated over the radio that something didn't feel right in the controls and he was hearing an unusual noise. He advised the helco supervisor, in another helicopter flying nearby, that he needed to leave the dip site and return to main helibase to have his mechanic investigate. While enroute, the pilot indicated the issues were increasing, and he needed to land immediately. The helco led him to nearest helispot, located in a cool burned over area. Upon left hand approach to this helispot, at about 500 yards upslope, the aircraft apparently became uncontrollable, pitching down & pioretting. Evidence showed that the aircraft contacted the boulder and a burnt conifer tree-covered hillside vertically, hard, level; leaving skid imprints in the soil through the ash covered surface, with aluminum and paint transferred to a smaller boulder located between the skid imprints. Red anti collision beacon lens parts were found scattered around the boulder, and the belly was crushed in at the right front crosstube saddle area. A tree in excess of a foot in thickness was chopped off at a 30 degree angle, approximately 8 feet above the ground level. The aircraft bounced back in the air, rolling right and landing on its top, on another larger boulder, the right top side if the cabin roof showing a large crush mark outboard of the transmission. The larger boulder showed aluminum transfer, and pieces of the main transmission case were found on top, along with a large quantity of transmission oil. The helicopter continued to roll to its right, coming to rest on its left side below the face of the boulder, with the longline wrapped around the fuselage. The main rotor mast and head did not contact the ground as the aircraft rolled to a stop. One main rotor blade was completely destroyed by contact with the rocks, with only a mangled leading edge remaining; and the other blade showed much less damage from contact with the trees, and largely intact, indicating the main rotor system did not turn more than 1 or 2 revolutions after initial tree impact and complete stoppage. The main rotor pitch horns were pulled from both main rotor grips, both scissor tubes were separated, and the drive link to the destroyed blade was broken off at the trunnion bearing connection to the swashplate, due to impact overload of that main rotor blade. The pilot's helmet was found pinned between the aft inboard corner of the broken left sky light frame and a boulder, above where the pilot was seated in the left seat. The pilot was able to extract himself from the pinned helmet & wreckage, then climbing vertically inside, up and out of the right pilots door on the top side, and hike clear, although he suffered serious injuries. One engine reportedly continued to run for an hour and a half, until it ran out of fuel. Examination of wreckage indicate that the gimbal ring and swashplate assy had broken free of the swashplate support, due to the progressive failure of the 4 cast aluminum ears at the top of the swashplate support. 2 ears showed polished fracture surfaces & 2 showed frosty fracture surfaces. The 2 bolts that secure the gimbal ring to the swashplate support ears, and the 2 bolts that secure the gimbal ring to the swashplate inner ring, had left 4 distinct battered areas on the outside of the collective sleeve, as well repeatedly scratched areas inside of the inner swashplate. The extent and quantity of battering & scratching indicates the gimbal ring / swashplate assembly was disconnected from the swashplate support in flight, at least partially, for some time.

-The longline and bucket were found attached, and the cargo electric hook release was found not armed.