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Drag force and drag coefficient
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
The second factor that affects the CDo is altitude. For a specific Mach number, as the altitude increases, the true airspeed decreases. For instance, consider an aircraft flying with a speed of Mach 0.5 at sea level. The true airspeed at this altitude 170 m/s (0.5 × 340 = 170). If this aircraft is flying with the same Mach number at 11,000 ft altitude, the true airspeed will be 147 m/s (0.5 × 294 = 147). In addition, the air density decreases with altitude at a higher rate. Thus, the higher altitude means the lower Reynolds number (Equation 3.24) and therefore the higher CDo. Figure 3.33 illustrates the variations of drag force for a light transport aircraft with turbofan engines at various altitudes. This transport aircraft has a stall speed of 90 knots and a maximum speed of 590 knots.
Command-filtered sensor-based backstepping controller for small unmanned aerial vehicles with actuator dynamics
Published in International Journal of Systems Science, 2018
Lijia Cao, Yongchao Wang, Shengxiu Zhang, Tan Fei
Here, the state vectors are and . is the output of the controlled plant, denotes the input vector of the vehicle, and and are the external disturbances. The functions , , and can be expressed as follows. where is the true airspeed, represents the mass, S denotes the reference area, denotes the dynamic pressure, is reference wing span and is mean aerodynamic chord, represents the thrust. And denotes the angle of attack, denotes the angle of sideslip, are attitude angles; represent angular rates around body axis; Also, the C* is called aerodynamic coefficient, where * denotes all the subscript. Moreover, the constants are defined as , , , , , , , , , where , , are roll, pitch, and yaw moments of inertia, respectively; is a product moment of inertia.