# Cessna 620 -- Linear Model

Graduate Research done by Jeff Scott
Advisor: Prof. Michael Selig
Applied Aerodynamics Group
Department of Aeronautical and Astronautical Engineering
University of Illinois at Urbana-Champaign, Urbana, Illinois 61801

Last updated June 1, 2000

The linear aerodynamics model uses stability derivatives to approximate actual aircraft behavior. The Cessna 620 linear model is based on the following flight conditions (cruise):

Flight Conditions
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
h | Altitude | altitude above sea level | ft | 18000 | Roskam pg 515 |
| Alpha | angle of attack | deg | 0 | Roskam pg 515 |
V | V_true_kts | velocity (true air speed) | kts | 217.2 | Roskam pg 515 | Mach 0.351
q | Dynamic_pressure | dynamic pressure | lb/ft2 | 91.1 | Roskam pg 515 |
C.G. | - | center of gravity location | % | 25 | Roskam pg 515 |
CL | CL | lift coefficient | - | ? |  | not available
CD | CD | drag coefficient | - | ? |  | not available
Cm | Cm | pitching moment coefficient | - | ? |  | not available

The data input into the simulator is listed in the following tables:

Geometry
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
b | bw | wingspan | ft | 55.1 | Roskam pg 515 |
| cbar | wing mean aerodynamic chord | ft | 6.58 | Roskam pg 515 |
S | Sw | wing surface area | ft2 | 340 | Roskam pg 515 |

Control Surface Geometry
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
emax | demax | maximum elevator deflection | deg | +20 | - | guess
emin | demin | minimum elevator deflection | deg | -20 | - | guess
amax | damax | maximum aileron deflection | deg | +20 | - | guess
amin | damin | minimum aileron deflection | deg | -20 | - | guess
rmax | drmax | maximum rudder deflection | deg | +20 | - | guess
rmin | drmin | minimum rudder deflection | deg | -20 | - | guess

Mass Data
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
W | Weight | weight at flight condition | lb | 15000 | Roskam pg 515 | converted to Mass [slug/ft3] in code
Ixx | I_xx | roll inertia | slug ft2 | 64811 | Roskam pg 515 |
Iyy | I_yy | pitch inertia | slug ft2 | 17300 | Roskam pg 515 |
Izz | I_zz | yaw inertia | slug ft2 | 64543 | Roskam pg 515 |
Ixz | I_xz | lateral cross inertia | slug ft2 | 0 | Roskam pg 515 |

Propulsion Data
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
Tmax | simpleSingleMaxThrust | maximum thrust | lb | 1300 | Roskam pg 516 | estimated from CTx at cruise

Aerodynamic Data
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
CD0 | CDo | drag coefficient at =0 | - | 0.0322 | Roskam pg 516 |
CD | CD_a | drag curve slope | 1/rad | 0.269 | Roskam pg 516 |
CDe | CD_de | drag due to elevator | 1/rad | 0 | Roskam pg 516 | e positive down
CL0 | CLo | lift coefficient at =0 | - | 0.48 | Roskam pg 516 |
CL | CL_a | lift curve slope | 1/rad | 5.55 | Roskam pg 516 |
CL | CL_adot | lift due to angle of attack rate | 1/rad | 2.7 | Roskam pg 516 |
CLq | CL_q | lift due to pitch rate | 1/rad | 7.5 | Roskam pg 516 |
CLe | CL_de | lift due to elevator | 1/rad | 0.58 | Roskam pg 516 | e positive down
Cm0 | Cmo | pitch moment coefficient at =0 | - | 0.06 | Roskam pg 516 |
Cm | Cm_a | pitch moment due to angle of attack | 1/rad | -1.18 | Roskam pg 516 |
Cm | Cm_adot | pitch moment due to angle of attack rate | 1/rad | -8.17 | Roskam pg 516 |
Cmq | Cm_q | pitch moment due to pitch rate | 1/rad | -22.4 | Roskam pg 516 |
Cme | Cm_de | pitching moment due to elevator | 1/rad | -1.73 | Roskam pg 516 | e positive down
CY | CY_beta | side force fue to sideslip angle | 1/rad | -0.883 | Roskam pg 517 |
CYp | CY_p | side force due to roll rate | 1/rad | -0.227 | Roskam pg 517 |
CYr | CY_r | side force due to yaw rate | 1/rad | 0.448 | Roskam pg 517 |
CYa | CY_da | side force due to aileron | 1/rad | 0 | Roskam pg 517 | a positive right aileron up
CYr | CY_dr | side force due to rudder | 1/rad | 0.2 | Roskam pg 517 | r positive left
Cl | Cl_beta | dihedral effect | 1/rad | -0.1381 | Roskam pg 517 |
Clp | Cl_p | roll damping | 1/rad | -0.566 | Roskam pg 517 |
Clr | Cl_r | roll moment due to yaw rate | 1/rad | 0.1166 | Roskam pg 517 |
Cla | Cl_da | roll moment due to aileron | 1/rad | -0.1776 | Roskam pg 517 | a positive right aileron up
Clr | Cl_dr | roll moment due to rudder | 1/rad | 0.02 | Roskam pg 517 | r positive left
Cn | Cn_beta | weathercock stability | 1/rad | 0.1739 | Roskam pg 517 |
Cnp | Cn_p | adverse yaw | 1/rad | -0.0501 | Roskam pg 517 |
Cnr | Cn_r | yaw damping | 1/rad | -0.2 | Roskam pg 517 |
Cna | Cn_da | yaw moment due to aileron | 1/rad | 0.0194 | Roskam pg 517 | a positive right aileron up
Cnr | Cn_dr | yaw moment due to rudder | 1/rad | -0.1054 | Roskam pg 517 | r positive left

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