What happened
The pilot reported that he took off, and during a climb through about 800 ft, he heard a loud snap and immediately felt severe lateral vibrations. He declared an emergency and landed without further incident.
The investigation
An investigation revealed that the inboard trailing ear of the main rotor sleeve/spindle assembly, PN 330A31-002607, for the blue blade, had failed. Evidence of fatigue was found over most of the fracture surface and evidence of fretting corrosion was found at the origin of the fatigue. Also, an area of fretting corrosion was found on the trailing side flange of the hinge pin, on a surface clamped by the torque of the hinge pin nut.
Findings
Records showed that the Aerospatiale service bulletin 01.35 had been complied with on 3/30/82, and that the hinge pin had been replaced on 4/10/82, about 100 flight hours before the failure. A spot check of the maintenance facility revealed that 2 out of 3 torque wrenches were overdue a calibration check. The third provided 54 inch lbs when set for 120.