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

Résumé

We propose to adopt a new airworthiness directive (AD) for certain Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD would result in all airplanes having new relays with a ground fault interrupter (GFI) feature. This proposed AD would require, depending on airplane configuration, doing certain wiring changes, replacing the fuel pump power control relays for the main, center and auxiliary tanks, as applicable, with new relays having a GFI feature, performing certain bonding resistance measurements, and modifying relay module assemblies. The proposed AD also would require revising the maintenance program to incorporate Airworthiness Limitations (AWLs) 28-AWL-23 (for Model 737-100, 737-200, and 737-200C series airplanes), and 28-AWL-22 (for Model 737-300, 737-400, and 737- 500 series airplanes). This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent damage to the fuel pumps caused by electrical arcing that could introduce an ignition source in the fuel tank, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.