Accident Sequence
At the end of an aerial application mission, the helicopter was refueled, and the pilot departed for home base. A few minutes after takeoff, the helicopter collided with trees.
Post-Accident Examination
Examination of the engine and drive train revealed no preimpact failure; however, the collective pitch control yoke bearing had failed. The ball bearings and race in the yoke bearing were observed to be pitted, and the ball bearings were worn undersized.
Maintenance History
The last inspection of the yoke bearing occurred about 9 years and 839 flight hours before the accident, during the 1,200 hour inspection. The yoke bearing was not required to be inspected during the recent 600 hour inspection. The bearing was an on-condition item, and did not have a scheduled time change. The bearing could not be inspected while installed on the helicopter.