Summary
We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 767-200, -300, and -300F series airplanes. For certain airplanes, this proposed AD would require modifying the fuel quantity indicating system (FQIS) densitometer. For certain other airplanes, this proposed AD would require replacing the existing hot short protector (HSP) on the FQIS densitometer with a new HSP. The proposed AD would also require revising the Airworthiness Limitations (AWL) section of the Instructions for Continued Airworthiness to incorporate AWL No. 28-AWL-22. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent the center tank fuel densitometer from overheating and becoming a potential ignition source inside the center fuel tank, which, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.