Accident Overview
The pilot reported that the engine RPM began to drop shortly after takeoff from an open field. In an attempt to regain RPM, the pilot opened the throttle further, but the engine did not respond. The helicopter subsequently crashed onto a building roof as the pilot attempted to land while avoiding power lines and other obstacles.
Post-Crash Examination
A post-crash examination of the helicopter revealed that the throttle-cable end-fitting had separated from the throttle cable pushrod at the fuel injector servo. Metallurgical examination of the fitting and pushrod joining threads disclosed uneven wear that had resulted from fretting.
Maintenance History
The manufacturer had issued Service Notice N-196, which requires inspection of the throttle cable for wear every 100 operating hours. According to the aircraft maintenance records, this notice was not complied with at the last inspection, which occurred 4 flight hours before the accident. The notice had last been complied with approximately 189 operating hours earlier.