Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 757 series airplanes. This proposal would require installation of an extender bracket for the compensator of the Simmonds fuel quantity indication system (FQIS) in the main fuel tanks. This action is necessary to prevent contact between the compensator for the Simmonds FQIS system and a flapper check valve on a baffle rib in the main fuel tanks, which--in conjunction with another wiring failure outside the fuel tank--could result in an electrical arc and a consequent potential source of ignition in the fuel tank. This action is intended to address the identified unsafe condition.