System for In-flight Airflow Measurements of an Agricultural Aircraft

Abstract

Airspeed and the orientation of spray nozzles relative to air direction significantly affect spray droplet size. A measurement system based on pressure probe techniques was developed to measure and record airspeed and airflow direction at spray boom and nozzle locations near the trailing edge of the wings and under the fuselage of a fixed-wing agricultural aircraft. The main feature of the system is an airflow measuring “rake” comprised of eight total pressure five-tube probes and two stream pressure probes. The probes are encased in an airfoil. A multiport rotary pneumatic valve is used to rapidly sample the differential (velocity) pressure between the total pressures and stream pressure. The system was calibrated in a wind tunnel for pitch and yaw angles up to ± 25°. Software was developed to control the rotary valve and data acquisition. The system was mounted on a Cessna AgHusky agricultural aircraft for flight testing and wake survey studies. A pitch, yaw, and Pitot tube boom extended forward from the leading edge of the aircraft wingtip provides aircraft attitude and airspeed reference for the rake measurement system. Data collected with this system will provide a basis for adjusting application hardware to obtain improved control of spray droplet size for various aircraft speeds and loadings.