Differential presssure based angle of attack estimation in a Flush Air Data System (FADS)

Flush Air Data Sensing System (FADS) form a mission critical sub system in future aerospace vehicle. FADS makes use of surface pressure measurements from the nose cap of the vehicle for deriving the air data parameters of the vehicle such as angle of attack, angle of sideslip, Mach number, etc. These parameters find use in the flight control and guidance systems, and also assist in the overall mission management. The overall FADS system including pressure transducers, tubing, port geometry, FADS algorithm, and electronics along with the mechanical and electrical integration scheme was successfully tested in a subsonic wind tunnel facility. The tests are carried out in a low speed wind tunnel at wind speed of 65m/s (Mach =0.2). For each blow-down, angle of sideslip (beta) is set at one value and angle of attack (alpha) is varied. This paper addresses the use of differential pressure transducers for angle of attack estimation during the test. MEMS based differential pressure transducers were developed for this purpose. The angle of attack obtained from the system is compared with the wind tunnel set conditions. The experimental result establishes that the accuracies demanded are provided by the system. Suggestions for improving the accuracy of the system are also provided based on the wind tunnel test results.