Accident Sequence
Shortly after departure, the pilot observed that more than "usual" forward cyclic and collective application was required to maintain the helicopter's desired airspeed. A scan of the instruments assured him that "All was okay." While cruising at 700 feet and 70 knots, the pilot detected a strong odor of burning rubber, a loss of power, illumination of the clutch warning light, and yawing of the helicopter. He entered autorotation, turned to a "dark, open area," and descended into trees.
Examination
Examination of the helicopter at the scene revealed that the drive belts were twisted, torn, and off of their respective pulleys. Further examination and testing showed that the clutch actuator functioned as designed, but the alignment of the drive belt sheaves and pulleys could not be determined due to impact damage.
Pilot Interview
In a follow-up interview, the pilot stated that during engine start, 10 to 15 seconds elapsed between his actuation of the clutch switch and the moment the main rotor blades began to turn. According to the pilot's operating handbook starting engine checklist, the rotor blades should turn less than 5 seconds after engagement of the clutch switch. Additionally, a note in the manufacturer's maintenance manual, V-Belt Installation, states: "A delay of more than 5 seconds between clutch switch engagement and rotor turning indicates excessive slack."