Last updated April 10, 2000
The linear aerodynamics model uses stability derivatives to approximate actual aircraft behavior. The Cessna 172 linear model is based on the following flight conditions:
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| Variable |
Variable in Code |
Description | Units | Value(s) | Source | Notes |
|---|---|---|---|---|---|---|
| h | Altitude | altitude above sea level | ft | ? | not available |
|
Alpha | angle of attack | deg | ? | not available |
V
|
V_true_kts | velocity (true air speed) | kts | ? | not available | |
| q | Dynamic_pressure | dynamic pressure | lb/ft2 | ? | not available | |
| C.G. | - | center of gravity location |
%
|
? | not available | |
| 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:
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| Variable |
Variable in Code |
Description | Units | Value(s) | Source | Notes |
|---|---|---|---|---|---|---|
| b | bw | wingspan | ft | 35.8 | c172_aero.c | |
|
cbar | wing mean aerodynamic chord | ft | 4.9 | c172_aero.c | |
| S | Sw | wing surface area | ft2 | 174 | c172_aero.c | |
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| Variable |
Variable in Code |
Description | Units | Value(s) | Source | Notes |
|---|---|---|---|---|---|---|
emax
|
demax | maximum elevator deflection | deg | +28 | c172_aero.c | |
emin
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demin | minimum elevator deflection | deg | -23 | c172_aero.c | |
amax
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damax | maximum aileron deflection | deg | +20 | c172_aero.c | |
amin
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damin | minimum aileron deflection | deg | -15 | c172_aero.c | |
rmax
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drmax | maximum rudder deflection | deg | +16 | c172_aero.c | |
rmin
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drmin | minimum rudder deflection | deg | -16 | c172_aero.c | |
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| Variable |
Variable in Code |
Description | Units | Value(s) | Source | Notes |
|---|---|---|---|---|---|---|
| GTOW | Weight | gross takeoff weight | lb | 2300 | c172_init.c |
converted to Mass [slug/ft3] in code |
| Ixx | I_xx | roll inertia | slug ft2 | 948 | c172_init.c | |
| Iyy | I_yy | pitch inertia | slug ft2 | 1346 | c172_init.c | |
| Izz | I_zz | yaw inertia | slug ft2 | 1967 | c172_init.c | |
| Ixz | I_xz | lateral cross inertia | slug ft2 | 0 | c172_init.c | |
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| Variable |
Variable in Code |
Description | Units | Value(s) | Source | Notes |
|---|---|---|---|---|---|---|
| Tmax | simpleSingleMaxThrust | maximum thrust | lb | 350 | c172_engine.c | use c172 engine model in code |
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| Variable |
Variable in Code |
Description | Units | Value(s) | Source | Notes |
|---|---|---|---|---|---|---|
| CD0 | CDo |
drag coefficient at =0
|
- | 0.031 | c172_aero.c | |
CD
|
CD_a | drag curve slope | 1/rad | 0.130 | c172_aero.c | not used in favor of CDK |
| K | CDK | induced drag constant, i.e. 1/(pi*e*AR) | - | 0.054 | c172_aero.c | |
CD e
|
CD_de | drag due to elevator | 1/rad | 0.060 | c172_aero.c |
e positive down
|
| CL0 | CLo |
lift coefficient at =0
|
- | 0.310 | c172_aero.c | |
CL
|
CL_a | lift curve slope | 1/rad | 5.143 | c172_aero.c | |
CL
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CL_adot | lift due to angle of attack rate | 1/rad | 1.7 | c172_aero.c | |
| CLq | CL_q | lift due to pitch rate | 1/rad | 3.9 | c172_aero.c | |
CL e
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CL_de | lift due to elevator | 1/rad | 0.430 | c172_aero.c |
e positive down
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| Cm0 | Cmo |
pitch moment coefficient at =0
|
- | -0.015 | c172_aero.c | |
Cm
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Cm_a | pitch moment due to angle of attack | 1/rad | -0.89 | c172_aero.c | |
Cm
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Cm_adot | pitch moment due to angle of attack rate | 1/rad | -5.2 | c172_aero.c | |
| Cmq | Cm_q | pitch moment due to pitch rate | 1/rad | -12.4 | c172_aero.c | |
Cm e
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Cm_de | pitching moment due to elevator | 1/rad | -1.28 | c172_aero.c |
e positive down
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CY
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CY_beta | side force fue to sideslip angle | 1/rad | -0.31 | c172_aero.c | |
| CYp | CY_p | side force due to roll rate | 1/rad | -0.037 | c172_aero.c | |
| CYr | CY_r | side force due to yaw rate | 1/rad | 0.21 | c172_aero.c | |
CY a
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CY_da | side force due to aileron | 1/rad | 0 | c172_aero.c |
a positiveright aileron up |
CY r
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CY_dr | side force due to rudder | 1/rad | 0.187 | c172_aero.c |
r positive left
|
Cl
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Cl_beta | dihedral effect | 1/rad | -0.089 | c172_aero.c | |
| Clp | Cl_p | roll damping | 1/rad | -0.47 | c172_aero.c | |
| Clr | Cl_r | roll moment due to yaw rate | 1/rad | 0.096 | c172_aero.c | |
Cl a
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Cl_da | roll moment due to aileron | 1/rad | -0.178 | c172_aero.c |
a positiveright aileron up |
Cl r
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Cl_dr | roll moment due to rudder | 1/rad | 0.0147 | c172_aero.c |
r positive left
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Cn
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Cn_beta | weathercock stability | 1/rad | 0.065 | c172_aero.c | |
| Cnp | Cn_p | adverse yaw | 1/rad | -0.03 | c172_aero.c | |
| Cnr | Cn_r | yaw damping | 1/rad | -0.099 | c172_aero.c | |
Cn a
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Cn_da | yaw moment due to aileron | 1/rad | 0.053 | c172_aero.c |
a positiveright aileron up |
Cn r
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Cn_dr | yaw moment due to rudder | 1/rad | -0.0657 | c172_aero.c |
r positive left
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