Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, that requires installation of components to provide shielding and separation of the fuel system wiring (that is routed to the fuel tanks) from adjacent wiring. This amendment also requires installation of flame arrestors and pressure relief valves in the fuel vent system. This amendment is prompted by testing results, obtained in support of an accident investigation, and by re-examination of possible causes of a similar accident. The actions specified by this AD are intended to prevent possible ignition of fuel vapors in the fuel tanks, and external ignition of fuel vapor exiting the fuel vent system and consequent propagation of a flame front into the fuel tanks.