1. Compute the effect of altitude on the dynamics of a high altitude UAV with characteristics shown below. Vary altitude from sea level to 60,000 feet and show how the frequency and damping of the short-period longitudinal dynamics change. Do this by hand using approximate linear equations of motion, ignoring changes in speed. Then use the web-based program (or your own program) to compute changes in the other dynamic modes and describe any potential problems with the design.
If we wanted to build a 1/5 scale model of this UAV that would fly at sea level with similar dynamics to the full scale design at 60,000 ft, what would it weigh?
Finally, if we wanted to use the same model to simulate the short period longitudinal dynamics of the UAV at sea level we could change the ballast weights to modify the c.g. position and the moment of inertia, Iyy. How would these have to be changed if the wing loading (weight/area) was set to 12 lb/ft2, but we did not want the basic short period dynamics to be changed?
area (ft^2) 540. span (ft) 116. chord (ft) 5.0 mass (sl) 500. Ixx (sl ft^2) 50000. Iyy (sl ft^2) 40000. Izz (sl ft^2) 65000. Ixz (sl ft^2) 0.0 Vt_ref (ft/sec) 177.0 alpha_ref 0.1 theta_ref 0.1 altitude_ref (ft) 0.0 CL_ref 0.8 CD_ref 0.04 Cm_ref 0.0 CLalpha 5.92 CDalpha 0.0 Cmalpha -0.3 CLq 15.98 CDq 0.2 Cmq -6.0 CLadot 0.0 CDadot 0.0 Cmadot 0.0 CYbeta -0.886 Clbeta -0.09 Cnbeta 0.05 CYp -0.041 Clp -0.0607 Cnp -0.1044 CYr 0.285 Clr 0.164 Cnr -0.0887
Assume none of the force or moment stability derivatives in the table above change with speed, Vt or scale. The controls are set so that the airplane trims at a reference CL of 0.8 in all cases.