Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 737-100, -200, - 300, -400, and -500 series airplanes. This proposal would require repetitive tests to verify the integrity of the yaw damper coupler, and various follow-on actions. This proposal also would require a one- time inspection to determine the part number of the engage solenoid valve of the yaw damper, and replacement of the valve with a valve having a different part number, if necessary. This proposal is prompted by a review of the design of the flight control systems on Model 737 series airplanes. The actions specified by the proposed 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.