Airworthiness Directives; Boeing Model 737-300, -400, -500, -600, -700, and -800 Series Airplanes Equipped with Vickers Combined Stabilizer Trim Motors

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 737 series airplanes. This action requires repetitive inspections and functional tests of a trailing edge flap limit switch to verify proper operation, and replacement of the existing limit switch with a new limit switch, if necessary. This AD also requires modification of the stabilizer control system, which constitutes terminating action for the repetitive inspections and tests. This amendment is prompted by reports of uncommanded stabilizer trim motion due to failure of the trailing edge flap limit switch. The actions specified in this AD are intended to prevent such failure, which could result in uncommanded (nose down) stabilizer trim motion and consequent reduced controllability of the airplane.