The three dimensional wind vector calculations are based on the difference between the aircraft's air speed and ground speed. The aircraft's air speed is determined using five pressure ports (Figure 1) located on the nose of the aircraft. The Pitot Nose pressure is measured using the center port, the attack angle is measured using the top and bottom ports, and the sideslip angle is measured using the difference between the two side ports. Bleed air from the engines is used to heat the radome (Figure 2) to help prevent ice build which can block the ports. Tubes, with water traps (Figure 3), connect each port to pressure transducer located in the nose of the aircraft.
The aircraft's ground speed is determined using an Applanix Position and Orientation System (POS). The POS system consist of a Inertial Measurement Unit (IMU) (Figure 4), GPS antenna, and the POS Computer System (Figure 5). The POS system computes an optimally accurate navigation solution using both inertial and GPS information. Real time 25 Hz data is received from the POS unit during flight and is recorded along with the other instrument data by the M300 data system. The POS data is also recorded at 200 Hz on a flash memory card that can be removed from the POS system and post processed to obtain a more accuracy navigation solution. The post processing procedure uses a Kalman filter based integrated navigation algorithm to compute the optimally accurate navigation solution.
- Figure 1: The nose of the University of North Dakota's Citation aircraft showing the five pressure ports used to measure the pitot nose pressure, the attack angle, and sideslip angle.
- Figure 2: The inside of the radome of the University of North Dakota's Citation aircraft showing tubes connected to the five pressure ports on the Aircraft's nose.
- Figure 3: The tubes and water traps in the nose of the University of North Dakota's Citation aircraft.
- Figure 4: The Inertial Measurement Unit (IMU) located in the back of Citation Aircraft cabin.
- Figure 5: The Position and Orientation System (POS) mounted in a 19“ rack in the cabin of the University of North Dakota's Citation aircraft.