Summary
This document proposes the adoption of a new airworthiness directive (AD) for Sikorsky Aircraft Corporation Model S-76A, S-76B and S-76C helicopters. The AD would require removing and inspecting each main rotor spindle attachment bolt (bolt) to ensure that the correct bolts are installed. This proposal is prompted by the discovery of improper bolts installed on a helicopter during its production. The actions specified by the proposed AD are intended to detect installation of incorrect bolts, which could result in reduced hub or bolt fatigue life, separation of the main rotor blade at the spindle attachment, and subsequent loss of control of the helicopter.