Store Unsteady Aerodynamic Loads Measurement Technology

Until recently, the stores released from supersonic aircraft have been carried on external pylons. This locates the initial release point of the store some distance from the aircraft, and the release sequence can be designed to encourage the store to move away from the aircraft after it is released. Aircraft that have been recently developed have internally carried stores. Internally carried stores are greatly impacted by unsteady flow upon release, and are susceptible to “fly back”, a phenomenon in which the trajectory of the store brings it into contact with the aircraft or another store. The current testing technique utilized by AEDC to analyze the aerodynamic loads on the store utilizes the combination of a balance integrated into the scale model store and a Captive Trajectory Support system that facilitates the capture of aerodynamic data and the movement of the model store through it''s trajectory as it moves away from the aircraft. Improvements are needed to the CTS system that will enable accurate, transient load data to be captured during testing. This will enable the transient loads to be taken into account when the store trajectory is computed, and will improve the accuracy of store separation test results. Streamline Automation proposes an innovative approach to upgrade the balance data acquisition system to increase the data capture rate, the addition of instrumentation that will aid in separating unsteady aerodynamic force information from structural vibrations, and a data processing framework that will fuse the data and extract the unsteady aerodynamic loads. BENEFIT: AEDC has two wind tunnels that perform store separation testing, 4T and 16T. The proposed system could be deployed at both wind tunnels to improve Captive Trajectory Support testing by accurately capturing unsteady loads. There are several other wind tunnel facilities that perform CTS testing. Some of these facilities, such as the NASA Ames 11'' transonic wind tunnel are government run facilities, but the CALSPAN 8'' transonic wind tunnel is privately operated. These wind tunnels perform similar types of testing on weapons bay launched stores, and could benefit from the same types of upgrades that are of interest to AEDC. Ultimately the proposed effort concerns the extraction of transient force data in a noisy environment, which has numerous applications.