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Engineering validation was necessary for manufacturing concepts intended to facilitate streamlining of aircraft sealing processes. The objective of this study was to determine if production cycle times can be shortened for aircraft sealing processes. One of the process timesaving concepts considered in this testing was to omit adhesion promoting or to convert this surface preparation requirement into an option. A variety of sealant bond surfaces (or substrates) were used in this study to test this concept for operations pertaining to fuel tank structure sealing and general (or environmental and pressure) sealing. Engineering test results presented in this report are the basis of conclusions and recommendations that indicate whether or not specific process timesaving concepts are valid.

Low-density polysulfide-based sealants are at the leading edge of engineering technology for sealing processes applicable to military and commercial aircraft. This paper focuses on a major aircraft manufacturer's quality assurance (QA) system dedicated to testing and evaluating sealants for placement on applicable Qualified Products Lists (QPLs); This QA system enabled this aircraft manufacturer to qualify two Class C designations -- Classes C-2 and C-48 -- of low-density sealants. The generic procedure for qualification of low-density sealants, especially Class C materials, is explained from the aircraft manufacturer's point of view. The Engineering decisionmaking process for selecting and documenting property test requirements for qualification of aircraft sealants is discussed.

Lightning protection plating on military airplane carbon-composite parts is a process that requires careful handling of the final product, especially during maintenance of fuel, hydraulic, and electrical systems installations. This paper and the accompanying ten-minute videotape focus on the primary reasons for having to take special precautions with lightning-protection plating (especially low plating adhesion--between 1 and 2 pounds per inch-width) and the engineering rework procedures that have been developed to return damaged plating to the original configuration specified in the engineering drawing.

This report summarizes engineering testing and evaluation of two low-volatile organic compound (VOC) cleaning solvents (WLS R-27M and Turco 4460-BK) and one over-the-counter, biodegradable solvent (De-Solv-lt) for use as cleaners of carbon-epoxy composite surfaces. The cleaners would be used prior to electrolytic deposition of copper and tin (or copper and nickel) plating on carbon-composite aircraft fuel tank structure. Turco 4460-BK was qualified for use on one military air vehicle as a cleaning solvent, because this solvent cleaner passed the required lightning strike and adhesion testing.