Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
It has been found occurrence of screw units manufactured with metallographic non-conformity that may increase their susceptibility to brittle fracture. The screw failure may result in loss of the related balance washer causing a possible ram air turbine (RAT) imbalance event, which may result in RAT structural failure, which associated with an electrical emergency situation, could result in loss of power to airplane flight controls hydraulic back-up system. * * * * *
Loss of power to the hydraulic back-up system for airplane flight controls could reduce the ability of the flightcrew to maintain the safe flight and landing of the airplane. The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.