Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model MD-900 series helicopters. This proposal would require removing certain serial-numbered main rotor swashplate bearings (bearings) and replacing them with airworthy bearings. This proposal is prompted by reports that inspections of several helicopters revealed that the outer bearing race had been rotating relative to the swashplate assembly, which was evidenced by wear marks in the rotating swashplate. The actions specified by the proposed AD are intended to prevent possible heat accumulation and resulting damage to the bearing caused by the bearing races rotating relative to the bearing seat, which could result in degraded helicopter response to pilot control input and possible loss of control of the helicopter.