Accident Narrative
On March 30, 2014, at approximately 1130 central daylight time, a Bell 47G-3B helicopter, registration N147WT, experienced a rollover during an autorotation near Oglesby, Texas. The helicopter, operated by Lazy 7 Agricultural Services LLC, was conducting an aerial observation flight under 14 Code of Federal Regulations Part 91. The local flight had originated from the Gatesville Municipal Airport (GOP) at 1100. The pilot and passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot reported that the purpose of the flight was to spot wildlife. During the flight, he initiated a climb to transition between areas. As he increased the throttle, he noticed a slight resistance. Shortly thereafter, the throttle freed up, but no response was observed from throttle movements. Both engine and rotor rpm indicators were in the green range, but rpm decayed when the pilot increased the collective. When he stopped increasing the collective, rotor and engine rpm increased rapidly and continued to accelerate. The pilot initiated an autorotation and cut off the fuel. During the final collective application to cushion the landing, the helicopter suddenly yawed left and simultaneously rolled to the right on touchdown.
Postaccident Examination
A postaccident examination of the helicopter revealed that the throttle control adapter had disconnected from the serrated shaft on the carburetor. The retention screws on the throttle control adapter were not safety wired to the carburetor idle stop lever, as required by the Bell Helicopter maintenance manual.
Maintenance History
Service Bulletin 131SB, issued on December 2, 1960, addressed the reworking of adapter screw holes and safety wiring of the adapter to the carburetor idle stop lever. This Service Bulletin was applicable to Bell 47G-2 and 47J-2 models. The maintenance manual for the 47G-3B was later revised to incorporate the information from the Service Bulletin. Maintenance records indicated that the carburetor was removed and replaced on September 25, 2012, and the last annual inspection was performed on November 11, 2013.