Abstract:One-step co-curing process of manufacturing the composites cover panel with stiffeners for wing fuel tank by applying open expansive silicon rubber die is presented. In view of more serious defects existing in the parts of initial manufacturing stage, including warp, stiffeners size out-of-tolerance, delamination and dense voids, the corresponding design modification, process improvements and quality control measures, are introduced. Perfect parts are obtained eventually, and the function check and flight tests with these parts are passed.