An Integrated, Modular Simulation System for Education ... - Cal Poly

difference between the two axes are the angle of attack (alpha) and the side slip angle(beta). In actual flight the airpath and aircraft body axes rarely coincide. The effects ofthe difference in angles adds to the overall drag as some of the lift is mapped to the dragand some of the original drag is mapped to the down force [+Fz] of the aircraft andtherefore affects the natural frequency, and damping, of the longitudinal and lateral longperiod oscillations. The simulator originally did not re-map the forces calculated inairpath axis to the aircraft body axis. The re-mapping of the forces changed the dynamicsof the model so that there was much less climb associated with a step input of negative(up command) elevator. The re-mapping of the forces also affected the natural frequencyand damping in the long period [phugoid] mode. Re-mapping added damping to thesystem and decreased the natural frequency. Figure 17 shows the changes in ζ, ωn and θfor the 3 mapping of the lift force into the drag force.21Pitch Rate and Angle With and Without Forces to Body AxisAngleAngle bodyRateRate body012345670 20 40 60 80 100 120 140 160 180 200Figure 17 Navion Long Period Longitudinal Dynamics56