Evaluating the Accuracy of Load Application for Static Structural Testing of Aerospace Flight Vehicles

Abstract

This study introduces a method to evaluate the accuracy of load application in static structural tests of aerospace flight vehicles which use lots of actuators. Test data were collected for this study from typical test conditions of four independent structural tests performed within two decades in this laboratory. The tests included three full-scale aircraft tests and a launch vehicle sub-component test. The accuracy of load application was evaluated by calculating the root mean square deviation (RMSD) of errors normalized by DLL (design limit load). The RMSD range of the normalized error for the three full-scale aircraft tests was 0.27–0.89% and was much larger than the 0.04% obtained for the launch vehicle sub-component test. After analyzing the errors in all 91 loading channels used for the four tests, it was determined that tight adjustment of the load limit valve (LLV), and using actuators with a small load ratio, introduced large errors in load application. Even after excluding undesirable data related to the tight adjustment of the LLV and the use of actuators with less than 3% load ratio, the accuracy of load application for the three full-scale tests was still lower than the results for the sub-component test. The factors which induced the large errors in the full-scale tests were determined to be the large displacement of wing or canard and the use of actuators with small load ratio. RMSDs recalculated after excluding the undesirable data were in the range of 0.26–0.41% for the full-scale tests. The maximum value, 0.41%, can be used as tolerance to confirm the accuracy of load application for the next full-scale tests.