When working with complex aircraft design it is necessary to be able test configurations easily. At Saab this is done in several ways. When looking at the weapons integration on the Gripen Aircraft, clearance analysis (called feasibility studies at Saab) are created to evaluate if new external stores can be mounted. This is done manually in CATIA by measuring and evaluating the result. To ease the work when performing these repetitive tasks, it is possible to take advantage of Knowledge Based Engineering, KBE. This thesis revolves around implementing KBE in the process. The approach is to create a configurator that can handle the different external stores and perform the required tasks. The end result is a configurator with a Graphical User Interface, GUI, in which the user gets help with the feasibility study and which requires light manual input from the user. The configurator performs the study and produces a Word report for the user to examine. The resulting time saving is around 75 to 80 percent from the original process. The conclusion is that the configurator can facilitate the feasibility studies at Saab by reducing the time and lower the threshold for the user. Even though the process is not fully automated, the configurator is judged to perform at a satisfying degree.