Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 727 and 737 series airplanes. This proposal would require replacing the fuel cap assembly with a new assembly on the inlet fitting at the inside top of the auxiliary fuel tank. The proposal would also require replacing the INOP placards with new placards. This proposal is prompted by reports that the fuel cap assembly, due to its design, became loose and allowed fuel to enter the deactivated auxiliary fuel tanks on in-service airplanes. The actions specified by the proposed AD are intended to prevent unwanted fuel transferring to the deactivated auxiliary fuel tanks, due to the problems associated with a loose fuel cap assembly.