Summary
This document proposes to revise an existing airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -300, - 400, and -500 series airplanes, that currently requires a one-time inspection to determine the part number of the engage solenoid valve of the yaw damper on the rudder power control unit, and replacement of the valve with a valve having a different part number, if necessary. That AD was prompted by a review of the design of the flight control systems on Model 737 series airplanes. The actions specified by that AD are intended to prevent sudden uncommanded yawing of the airplane due to potential failures within the yaw damper system, and consequent injury to passengers and crewmembers. This action would make certain editorial changes to clarify the requirements of the existing AD.