# Convair 880 -- 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 Convair 880 linear model is based on the following flight conditions (cruise condition 6 in McCormick):

Flight Conditions
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
h | Altitude | altitude above sea level | ft | 35000 | McCormick pg 624 |
|  | Alpha | angle of attack | deg | 4.7 | McCormick pg 624 |
V | V_true_kts | velocity (true air speed) | kts | 461 | McCormick pg 624 | Mach 0.8
q | Dynamic_pressure | dynamic pressure | lb/ft2 | 223.7 | - |
C.G. | - | center of gravity location | % | 25 | McCormick pg 624 |
CL | CL | lift coefficient | - | 0.347 | McCormick pg 624 |
CD | CD | drag coefficient | - | 0.024 | McCormick pg 624 |
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 | 120 | Nelson pg 414 |
| cbar | wing mean aerodynamic chord | ft | 18.94 | Nelson pg 414 |
S | Sw | wing surface area | ft2 | 2000 | Nelson pg 414 |

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 | 155000 | McCormick pg 624 | converted to Mass [slug/ft3] in code
Ixx | I_xx | roll inertia | slug ft2 | 1510000 | McCormick pg 624 |
Iyy | I_yy | pitch inertia | slug ft2 | 2510000 | McCormick pg 624 |
Izz | I_zz | yaw inertia | slug ft2 | 4100000 | McCormick pg 624 |
Ixz | I_xz | lateral cross inertia | slug ft2 | 0 |  | assumed

Propulsion Data
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
Tmax | simpleSingleMaxThrust | maximum thrust | lb | 60000 | David pg 274 | engine rating (990A)

Aerodynamic Data
Variable | Variable in Code | Description | Units | Value(s) | Source | Notes
--- | --- | --- | --- | --- | --- | ---
CD0 | CDo | drag coefficient at =0 | - | 0.024 | Nelson pg ? |
CD | CD_a | drag curve slope | 1/rad | 0.15 | McCormick pg 624 |
CDe | CD_de | drag due to elevator | 1/rad | 0 |  | assumed e positive down
CL0 | CLo | lift coefficient at =0 | - | 0.347 | Nelson pg ? |
CL | CL_a | lift curve slope | 1/rad | 4.8 | McCormick pg 624 |
CL | CL_adot | lift due to angle of attack rate | 1/rad | 2.7 | McCormick pg 624 |
CLq | CL_q | lift due to pitch rate | 1/rad | 7.5 | McCormick pg 624 |
CLe | CL_de | lift due to elevator | 1/rad | 0.19 | McCormick pg 624 | e positive down
Cm0 | Cmo | pitch moment coefficient at =0 | - | 0 | Nelson pg ? |
Cm | Cm_a | pitch moment due to angle of attack | 1/rad | -0.65 | McCormick pg 624 |
Cm | Cm_adot | pitch moment due to angle of attack rate | 1/rad | -4.5 | McCormick pg 624 |
Cmq | Cm_q | pitch moment due to pitch rate | 1/rad | -12 | McCormick pg 624 |
Cme | Cm_de | pitching moment due to elevator | 1/rad | -0.57 | McCormick pg 624 | e positive down
CY | CY_beta | side force fue to sideslip angle | 1/rad | -0.812 | Nelson pg ? |
CYp | CY_p | side force due to roll rate | 1/rad | 0 | Nelson pg ? |
CYr | CY_r | side force due to yaw rate | 1/rad | 0.184 | Nelson pg ? |
CYa | CY_da | side force due to aileron | 1/rad | 0 |  | assumed a positive right aileron up
CYr | CY_dr | side force due to rudder | 1/rad | 0.019 | Nelson pg ? | r positive left
Cl | Cl_beta | dihedral effect | 1/rad | -0.117 | Nelson pg ? |
Clp | Cl_p | roll damping | 1/rad | -0.312 | Nelson pg ? |
Clr | Cl_r | roll moment due to yaw rate | 1/rad | 0.153 | Nelson pg ? |
Cla | Cl_da | roll moment due to aileron | 1/rad | -0.05 | Nelson pg ? | a positive right aileron up
Clr | Cl_dr | roll moment due to rudder | 1/rad | 0.019 | Nelson pg ? | r positive left
Cn | Cn_beta | weathercock stability | 1/rad | 0.129 | Nelson pg ? |
Cnp | Cn_p | adverse yaw | 1/rad | -0.011 | Nelson pg ? |
Cnr | Cn_r | yaw damping | 1/rad | -0.165 | Nelson pg ? |
Cna | Cn_da | yaw moment due to aileron | 1/rad | 0.008 | Nelson pg ? | a positive right aileron up
Cnr | Cn_dr | yaw moment due to rudder | 1/rad | -0.076 | Nelson pg ? | r positive left

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