Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This proposal would require a general visual inspection for sealant at the interface between the diagonal brace fitting and the aft bulkhead and at the four bolts common to the interface. It would also require applying sealant if none is present or if it is not continuous. This action is necessary to prevent flammable fluid in the upper or rear pylon areas from leaking past unsealed areas and onto a hot engine nozzle, which could result in ignition of the fluid, causing an undetected and uncontrollable fire to spread into the engine struts. This action is intended to address the identified unsafe condition.