Summary
This document proposes adopting a new airworthiness directive (AD) for Bell Helicopter Textron Canada Limited (Bell) Model 427 helicopters. This proposal would require replacing the hydraulic solenoid tee fitting (tee fitting) and tubes. This proposal is prompted by the manufacturer's discovery that tee fittings may be installed improperly and restrict hydraulic fluid flow. The actions specified by this proposed AD are intended to prevent restricted flow of hydraulic fluid to the flight control hydraulic actuators resulting in loss of hydraulic control, excessive stiffness in the flight controls, and a subsequent forced landing of the helicopter.