On April 16, 1994, at 2000 mountain standard time, a Bell 47G-3B- 1 helicopter, N304JP, landed hard following a loss of engine power while engaged in aerial application operations near Yuma, Arizona. The helicopter was owned and operated by Sundown Helicopters, Inc., of Yuma, Arizona, under the provisions of 14 CFR Part 137 of the Federal Aviation Regulations. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The aircraft incurred substantial damage. The certificated commercial pilot, the sole occupant, was not injured. The flight originated from the field to be sprayed about 1915 hours on the day of the accident. The operator and pilot reported that the helicopter had completed a swath run and was pulling up to clear a line of trees when the engine decelerated to idle. The pilot entered an autorotation and landed hard, damaging the skids and the fuselage. Postaccident inspection of the engine revealed that the throttle arm had come off the carburetor throttle body shaft. The operator stated that the arm and shaft were new components, installed on February 24, 1994, by a contract mechanic. The operator also stated that an "excessive amount (about 2 inches) of safety wire was on the arm, which allowed the arm to slip off the shaft."