SYSTEM FOR IN-FLIGHT AIR-FLOW MEASUREMENTS OF AN AGRICULTURAL AIRCRAFT

Airspeed and the orientation of spray nozzles relative to air directio n significantly affect spray droplet size. A measurement system based on pressure probe techniques was developed to measure and record airsp eed and airflow direction at spray boom and nozzle locations near the trailing edge of the wings and under the fuselage of a fixed-wing agri cultural aircraft. The main feature of the system is an airflow measur ing ''rake'' comprised of eight total pressure five-tube probes and tw o stream pressure probes. The probes are encased in an airfoil. A mult iport rotary pneumatic valve is used to rapidly sample the differentia l (velocity) pressure between the total pressures and stream pressure. The system was calibrated in a wind tunnel for pitch and yaw angles u p to +/-25 degrees. Software was developed to control the rotary valve and data acquisition. The system was mounted on a Cessna AgHusky agri cultural aircraft for flight testing and wake survey studies. A pitch, yaw, and Pitot tube boom extended forward from the leading edge of th e aircraft wingtip provides aircraft attitude and airspeed reference f or the rake measurement system. Data collected with this system will p rovide a basis for adjusting application hardware to obtain improved c ontrol of spray droplet size for various aircraft speeds and loadings.