Summary
This document proposes superseding an existing airworthiness directive (AD) for MD Helicopters, Inc. (MDHI) Model MD-900 helicopters. That AD currently requires applying serial numbers to certain parts, increasing the life limit for various parts, maintaining a previously established life limit for a certain vertical stabilizer control system (VSCS) bellcrank assembly and bellcrank arm, and correcting the part number for the VSCS bellcrank arm. This proposal would require the same actions, except it would reduce the life limit of the swashplate spherical slider bearing (slider bearing). It would further correct what was described as a "bellcrank arm'' life limit in the current AD and correctly describe it as another "bellcrank assembly'' life limit. This proposal is prompted by two reports of cracks in the slider bearing that occurred well before the previously increased retirement life of 2,030 hours time-in-service (TIS) was reached. The actions specified by the proposed ADare intended to establish appropriate life limits for various parts, and to prevent fatigue failure of those parts and subsequent loss of control of the helicopter.