WBS 5018 is the Honeywell Aerospace fusion welding specification. It defines all the fabrication and quality requirements as well as the procedure qualification data for welding production parts to that specification when defined on drawings. It is for all fusion welding processes, not just GTAW. It does have differences in fabrication/procedure qualification requirements when compared to AWS D17.1, but is also very similar as well. You will have to obtain a copy of the spec to ensure you are performing your procedure quals correctly for the weld joints. Hope this helps.