Airworthiness Directives; The Boeing Company Model 737-600, -700, -700C, -800, and -900 Series Airplanes

We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires installation of an automatic shutoff system for the center tank fuel boost pumps, and installation of a placard in the airplane flight deck if necessary. This AD also requires revisions to the Limitations and Normal Procedures sections of the airplane flight manual to advise the flightcrew of certain operating restrictions for airplanes equipped with an automated center tank fuel pump shutoff control. This AD further requires installation of a secondary control relay for the electrical control circuit of each of the two center tank fuel boost pumps. Additionally, this AD requires a revision to the maintenance program to incorporate Airworthiness Limitation (AWL) No. 28-AWL-23. This AD also provides an option of installation and maintenance of universal fault interrupters using a certain supplemental type certificate, which terminates certain requirements of this AD. This AD was prompted by fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent center tank fuel pump operation with continuous low pressure, which could lead to friction sparks or overheating in the fuel pump inlet that could create a potential ignition source inside the center fuel tank. These conditions, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.