Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A Helicopter

摘要

This document proposes superseding an existing airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A helicopters. That AD currently requires a service life limit on certain landing gear parts based on hours time-in-service (TIS). This action would add another method of calculating the life limit for certain landing gear parts based on cycles and would require the operator to choose and record the method of calculating the service life of each part in the rotorcraft history or equivalent record. This action would also require replacing the part based upon either the maximum hours TIS or the maximum cycles but not both. This proposal is prompted by the need to add flight cycles as a method of calculating the life limit for certain landing gear parts based on fatigue analyses. The actions required by the proposed AD are intended to add or revise the retirement life for certain landing gear parts to prevent fatigue failure of the landing gear and subsequent loss of control of the helicopter.