 |
SUAVE
2.5.2
An Aerospace Vehicle Environment for Designing Future Aircraft
|
|
|
SUAVE
2.5.2
An Aerospace Vehicle Environment for Designing Future Aircraft
|
|
Modules | |
| Supporting_Functions | |
Functions | |
| def | SUAVE.Methods.Flight_Dynamics.Dynamic_Stability.Full_Linearized_Equations.lateral_directional.lateral_directional (velocity, Cn_Beta, S_gross_w, density, span, I_z, Cn_r, I_x, Cl_p, J_xz, Cl_r, Cl_Beta, Cn_p, Cy_phi, Cy_psi, Cy_Beta, mass) |
| def | SUAVE.Methods.Flight_Dynamics.Dynamic_Stability.Full_Linearized_Equations.longitudinal.longitudinal (velocity, density, S_gross_w, mac, Cm_q, Cz_alpha, mass, Cm_alpha, Iy, Cm_alpha_dot, Cz_u, Cz_alpha_dot, Cz_q, Cw, Theta, Cx_u, Cx_alpha) |
| def SUAVE.Methods.Flight_Dynamics.Dynamic_Stability.Full_Linearized_Equations.lateral_directional.lateral_directional | ( | velocity, | |
| Cn_Beta, | |||
| S_gross_w, | |||
| density, | |||
| span, | |||
| I_z, | |||
| Cn_r, | |||
| I_x, | |||
| Cl_p, | |||
| J_xz, | |||
| Cl_r, | |||
| Cl_Beta, | |||
| Cn_p, | |||
| Cy_phi, | |||
| Cy_psi, | |||
| Cy_Beta, | |||
| mass | |||
| ) |
This calculates the natural frequency and damping ratio for the full linearized dutch
roll mode along with the time constants for the roll and spiral modes
Assumptions:
X-Z axis is plane of symmetry
Constant mass of aircraft
Origin of axis system at c.g. of aircraft
Aircraft is a rigid body
Earth is inertial reference frame
Perturbations from equilibrium are small
Flow is Quasisteady
Zero initial conditions
Neglect Cy_p and Cy_r
Source:
J.H. Blakelock, "Automatic Control of Aircraft and Missiles" Wiley & Sons, Inc. New York, 1991, p 118-124.
Inputs:
velocity - flight velocity at the condition being considered [meters/seconds]
Cn_Beta - coefficient for change in yawing moment due to sideslip [dimensionless] (no simple relation)
S_gross_w - area of the wing [meters**2]
density - flight density at condition being considered [kg/meters**3]
span - wing span of the aircraft [meters]
I_z - moment of interia about the body z axis [kg * meters**2]
Cn_r - coefficient for change in yawing moment due to yawing velocity [dimensionless] ( - C_D(wing)/4 - 2 * Sv/S * (l_v/b)**2 * (dC_L/dalpha)(vert) * eta(vert))
I_x - moment of interia about the body x axis [kg * meters**2]
Cl_p - change in rolling moment due to the rolling velocity [dimensionless] (no simple relation for calculation)
J_xz - products of inertia in the x-z direction [kg * meters**2] (if X and Z lie in a plane of symmetry then equal to zero)
Cl_r - coefficient for change in rolling moment due to yawing velocity [dimensionless] (Usually equals C_L(wing)/4)
Cl_Beta - coefficient for change in rolling moment due to sideslip [dimensionless]
Cn_p - coefficient for the change in yawing moment due to rolling velocity [dimensionless] (-C_L(wing)/8*(1 - depsilon/dalpha)) (depsilon/dalpha = 2/pi/e/AspectRatio dC_L(wing)/dalpha)
Cy_phi - coefficient for change in sideforce due to aircraft roll [dimensionless] (Usually equals C_L)
Cy_psi - coefficient to account for gravity [dimensionless] (C_L * tan(Theta))
Cy_Beta - coefficient for change in Y force due to sideslip [dimensionless] (no simple relation)
mass - mass of the aircraft [kilograms]
Outputs:
output - a data dictionary with fields:
dutch_w_n - natural frequency of the dutch roll mode [radian/second]
dutch_zeta - damping ratio of the dutch roll mode [dimensionless]
roll_tau - approximation of the time constant of the roll mode of an aircraft [seconds] (positive values are bad)
spiral_tau - time constant for the spiral mode [seconds] (positive values are bad)
Properties Used:
N/A
| def SUAVE.Methods.Flight_Dynamics.Dynamic_Stability.Full_Linearized_Equations.longitudinal.longitudinal | ( | velocity, | |
| density, | |||
| S_gross_w, | |||
| mac, | |||
| Cm_q, | |||
| Cz_alpha, | |||
| mass, | |||
| Cm_alpha, | |||
| Iy, | |||
| Cm_alpha_dot, | |||
| Cz_u, | |||
| Cz_alpha_dot, | |||
| Cz_q, | |||
| Cw, | |||
| Theta, | |||
| Cx_u, | |||
| Cx_alpha | |||
| ) |
This calculates the natural frequency and damping ratio for the full
linearized short period and phugoid modes
Assumptions:
X-Z axis is plane of symmetry
Constant mass of aircraft
Origin of axis system at c.g. of aircraft
Aircraft is a rigid body
Earth is inertial reference frame
Perturbations from equilibrium are small
Flow is Quasisteady
Zero initial conditions
Cm_a = CF_z_a = CF_x_a = 0
Neglect Cx_alpha_dot, Cx_q and Cm_u
Source:
J.H. Blakelock, "Automatic Control of Aircraft and Missiles" Wiley & Sons, Inc. New York, 1991, p 26-41.
Inputs:
velocity - flight velocity at the condition being considered [meters/seconds]
density - flight density at condition being considered [kg/meters**3]
S_gross_w - area of the wing [meters**2]
mac - mean aerodynamic chord of the wing [meters]
Cm_q - coefficient for the change in pitching moment due to pitch rate [dimensionless] (2 * K * dC_m/di * lt/c where K is approximately 1.1)
Cz_alpha - coefficient for the change in Z force due to the angle of attack [dimensionless] (-C_D - dC_L/dalpha)
mass - mass of the aircraft [kilograms]
Cm_alpha - coefficient for the change in pitching moment due to angle of attack [dimensionless] (dC_m/dC_L * dCL/dalpha)
Iy - moment of interia about the body y axis [kg * meters**2]
Cm_alpha_dot - coefficient for the change in pitching moment due to rate of change of angle of attack [dimensionless] (2 * dC_m/di * depsilon/dalpha * lt/mac)
Cz_u - coefficient for the change in force in the Z direction due to change in forward velocity [dimensionless] (usually -2 C_L or -2C_L - U dC_L/du)
Cz_alpha_dot - coefficient for the change of angle of attack caused by w_dot on the Z force [dimensionless] (2 * dC_m/di * depsilon/dalpha)
Cz_q - coefficient for the change in Z force due to pitching velocity [dimensionless] (2 * K * dC_m/di where K is approximately 1.1)
Cw - coefficient to account for gravity [dimensionless] (-C_L)
Theta - angle between the horizontal axis and the body axis measured in the vertical plane [radians]
Cx_u - coefficient for the change in force in the X direction due to change in the forward velocity [dimensionless] (-2C_D)
Cx_alpha - coefficient for the change in force in the X direction due to the change in angle of attack caused by w [dimensionless] (C_L-dC_L/dalpha)
Outputs:
output - a data dictionary with fields:
short_w_n - natural frequency of the short period mode [radian/second]
short_zeta - damping ratio of the short period mode [dimensionless]
phugoid_w_n - natural frequency of the short period mode [radian/second]
phugoid_zeta - damping ratio of the short period mode [dimensionless]
Properties Used:
N/A
1.8.15