Drones for aerodynamic and structural testing /DAST/ - A status report

A program for providing research data on aerodynamic loads and active control systems on wings with supercritical airfoils in the transonic speed range is described. Analytical development, wind-tunnel tests, and flight tests are included. A Firebee II target drone vehicle has been modified for use as a flight test facility. The program currently includes flight experiments on two aeroelastic research wings. The primary purpose of the first flight experiment is to demonstrate an active control system for flutter suppression on a transport-type wing. Design and fabrication of the wing are complete and, after installing research instrumentation and the flutter suppression system, flight testing is expected to begin in August 1979. The experiment on the second research wing—a fuel-conservative transport-type—is to demonstrate multiple active control systems, including flutter suppression, maneuver load alleviation, gust load alleviation, and reduced static stability. Of special importance for this second experiment is the development and validation of integrated design methods which include the benefits of active controls in the structural design. ORRELATION of theoretical and experimental results is a traditional method for assessing advanced design technology. The methods used in testing nearly always are a compromise between the ideal and the practical. This situation is especially true for tests of aeroelastic models. Wind-tunnel tests in the transonic range are traditionally limited by model size, dynamic pressure (for aeroelastic tests), and effects of interaction between the model and reflected shock waves. Full-scale piloted flight tests are restrained by cost and considerations of safety of onboard personnel, especially for flutter tests. A recently initiated NASA program, Drones for Aerodynamic and Structural Testing (DAST), uses an unmanned target drone aircraft for special high-risk flight tests and provides a test method that is a strong complement to wind-tunnel and full-scale piloted testing. Primary focus is on tests in the transonic speed range. For this program, maneuverability requirements are minimal for the test bed vehicle; it is merely used to subject research wings to selected flight conditions. It is sometimes referred to as a flight test facility or ''wind tunnel in the sky." Since the test vehicle has a parachute recovery system, retrieval is possible even in cases of structural failure. The program is primarily NASA in-house with contracted support as necessary. The principal research objectives of the DAST program are to validate: 1) systems synthesis and analysis developments for active control of aeroelastic response and 2) analysis techniques for aerodynamic loads prediction. These objectives will be accomplished by means of experiments on selected aeroelastic research wing (ARW) configurations. Benefits of flight testing include: 1) elimination of questions concerning tunnel interference effects with walls and model