Airworthiness Directives; McDonnell Douglas Helicopter Systems Model MD-900 Helicopters

This amendment adopts a new airworthiness directive (AD), applicable to McDonnell Douglas Helicopter Systems (MDHS) Model MD-900 helicopters, that requires removing certain serial-numbered main rotor swashplate bearings (bearings) and replacing them with airworthy bearings. This amendment 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 this 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.