Robinson Helicopter Company in Torrance California manufactures two different model lines of normally-aspirated piston powered helicopters, the R-22 and the R-44. These helicopters utilize a drive system that transfers power from the engine to the transmission and rotor drive shafts through the use of drive belts. Robinson has experienced problems with this system since the early 1980s.
Robinson issued a service letter discussing premature wear of its drive belts in 1981. The company issued a mandatory service bulletin due to belts climbing out of sheave grooves in 1983. Robinson changed its sheave alignment tolerance and engine shimming procedures in 1984. Also in 1984 Robinson acknowledged receiving reports of belts coming off or rolling over in flight. In 1986 Robinson introduced a new version of drive belts. Again, they received reports of the Banded Vee Belts jumping out of the drive sheaves. Robinson acknowledged that the belts have a tendency to either roll in the sheave or break during the first 100 hours of service. In the years since there have been changes to belts, alterations to inspection procedures, and findings of belt separation or shredding as the probable cause for power failure. In 2009 the Australian Government Civil Aviation Safety Authority issued an Airworthiness Bulletin related to the R-22 main rotor drive system. The Australian government stated that its airworthiness bulletin was “raised in response to continuing reports of R22 main rotor drive system failures, including low time-in-service main rotor drive belt failures.” If a Robinson Helicopter is involved in a mishap careful investigation of all drive system components must take place to evaluate the root cause of the mishap. Our firm is investigating drive system failures in these helicopters.