Sterling, MA, USA
N54VP
Boucher Revolution Mini 500
The pilot hover-taxied the helicopter from its tiedown spot to a grassy area for takeoff. Upon reaching the grassy area, he initiated a takeoff, and the helicopter accelerated through effective translational lift and began to climb. About 30 feet and 25 mph, the rotor system drive belt broke. The helicopter yawed to the left, and the pilot immediately lowered the collective and applied right rudder to correct the yaw. The helicopter impacted the ground "straight ahead but tail down." The main rotor deflected downward, and a rotor blade stuck the tail boom. The helicopter's right skid collapsed, and the helicopter rolled over on its right side and caught on fire. A section of drive belt, about 46 inches in length, had "broomstraw" separations at both ends. On the toothed side of the belt, there were about 15 areas along one edge that were worn down or missing. Another section of belt, about 40 inches in length, also had broomstaw separations at both ends, although one end had considerably less. The belt was missing material its entire length, with the missing material varying between 1/2 to 3/4 the width of the belt.
On June 8, 2002, about 1600 eastern daylight time, a homebuilt Revolution Mini 500 helicopter, N54VP, was destroyed in a post-impact fire, following a forced landing during an attempted takeoff at Sterling Airport (3B3), Sterling, Massachusetts. The certificated private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the local personal flight, conducted under 14 CFR Part 91. According to the pilot, he hover-taxied the helicopter from its tiedown spot to a grassy area for takeoff. Upon reaching the grassy area, the pilot initiated the takeoff, and the helicopter accelerated through effective translational lift and began to climb. About 30 feet and 25 mph, the rotor system drive belt broke. The helicopter yawed to the left, and the pilot immediately lowered the collective and applied right rudder to correct the yaw. The helicopter impacted the ground "straight ahead but tail down." The main rotor deflected downward, and a rotor blade stuck the tail boom. The helicopter's right skid collapsed, and the helicopter rolled over on its right side and caught on fire. A certificated airframe and powerplant mechanic reported that he had seen the pilot conduct a preflight inspection and later start the helicopter's engine. The pilot performed a run-up, then the helicopter lifted off the ground and into a hover. The mechanic turned away to work on a glider, but looked up when he heard the helicopter's engine rpm rapidly increase. He then saw the helicopter's main rotor blades hit the ground and the helicopter roll over. A small fire began in the vicinity of the engine compartment (the engine was no longer running), and eventually consumed almost the entire helicopter. According to a Federal Aviation Administration (FAA) inspector, among the charred remains of the helicopter, was a separated main rotor drive belt. The belt had worn areas along both edges. The belt had been supplied with the helicopter kit, and had, along with the helicopter, accumulated 212 hours of operation. Two sections of drive belt were provided to the Safety Board for examination. One section, about 46 inches in length, had "broomstraw" separations at both ends. On the toothed side of the belt, there were about 15 areas along one edge that were worn down or missing. The other section of belt was about 40 inches in length, and also had broomstaw separations at both ends, although one end had considerably less. The belt was missing material its entire length, with the missing material varying between 1/2 to 3/4 the width of the belt. The belt part number provided by the FAA inspector was 0506. A review of the Mini-500 master parts list described part number 0506 as "Drive belt cog type 50 mm." The belt provided by the FAA inspector had a maximum continuous width of 30 mm.
A misalignment of the rotor system drive belt, which resulted in belt chaffing, its subsequent separation, and a resultant loss of power to the rotor system. Also causal was the relatively low altitude and airspeed at which the separation occurred, which inhibited the pilot's inability to maintain a level attitude during the autorotation.
Source: NTSB Aviation Accident Database
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