A new Airworthiness Directive (AD) is under consideration by the FAA, targeting all Robinson Model R44 and R44 II helicopters. This proposed AD stems from documented instances of fractured clutch shaft forward yokes (yokes) in the main rotor (M/R) drive, attributed to fatigue cracking.
Following a reported yoke failure in 2022, the FAA issued Special Airworthiness Information Bulletin (SAIB) AIR-22-08, reiterating the importance of strict adherence to existing inspection protocols and maintenance manuals. The manufacturer indicated that the yoke failure was caused by fatigue cracking and improper torque at the bolt hole and yoke cross-section. Subsequent to the issuance of the SAIB, another incident was reported by the manufacturer involving yoke fracture and separation from the drive train, once more attributed to fatigue cracks and improper torquing.
The proposed AD necessitates visual inspections, to be conducted within 100 hours of time-in-service (TIS), of specific part-numbered flex plates, yokes, and yoke bolts. Depending on the inspection outcomes, affected parts would require replacement. Furthermore, the AD mandates replacement of a designated part-numbered yoke after reaching 2,200 hours TIS or within 12 years from initial installation. Alternatively, if removal from service is not opted for, a 10X or higher power magnification visual inspection along with a magnetic particle inspection would be required.
Comments on this proposed AD must be submitted by April 15, 2024.
