Examination of a Helicopter Main Rotor Tension-Torsion Strap Fitting that Fractured Due to a Quench Crack

A helicopter accident occurred when a main rotor tension-torsion strap fitting fractured as a result of fatigue. The fatigue propagated from a quench crack that occurred during manufacturing. Fluorescent magnetic particle inspection (MPI) did not catch the indication during the manufacturing process, but other quench cracked fittings subject to MPI after the accident did reveal obvious indications.