Wind Tunnel Testing of Variable Camber Compliant Wing with Multiple Load Cell Test Fixture

This paper describes the design, setup, and testing of a unique mounting fixture built for the Variable Camber Compliant Wing developed by the U.S. Air Force Research Laboratory. The intent of the Variable Camber Compliant Wing was to demonstrate an active 2D section camber change under aerodynamic load. Mounting possibilities were limited in the Vertical Wind Tunnel due to the dimensions and weight of the wing which necessitated a custom design to obtain aerodynamic force measurements. ATI Industrial Automation offers a promising solution with their wide range of multi-axis force/torque sensors which are becoming widely adopted in aerodynamic testing of small unmanned aircraft. These sensors can provide accurate results when loaded in close proximity to the balance center. However, it has been reported in literature that the error increases dramatically when loaded off the balance center. In this case, a load cell is mounted on each end of the unique fixture, forming a direct interaction between the two load cells. An extensive calibration loading procedure was performed prior to the test to develop a calibration matrix sensitive to the test setup. The intent of this paper is to present development of a correction method for this unique mounting fixture which could provide a new flexible wing testing capability in the Vertical Wind Tunnel Facility at the Air Force Research Laboratory.