Cessna 172 -- Nonlinear 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 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:

Flight Conditions
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:

Geometry
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

Control Surface Geometry
Variable Variable
in Code 		Description Units Value(s) Source Notes
emax demax maximum elevator deflection deg +28 c172_aero.c
emin demin minimum elevator deflection deg -23 c172_aero.c
amax damax maximum aileron deflection deg +20 c172_aero.c
amin damin minimum aileron deflection deg -15 c172_aero.c
rmax drmax maximum rudder deflection deg +16 c172_aero.c
rmin drmin minimum rudder deflection deg -16 c172_aero.c

Mass Data
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

Propulsion Data
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

Aerodynamic Data
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 code
K CDK induced drag constant, i.e. 1/(pi*e*AR) - 0.054 c172_aero.c
CDe CD_de drag due to elevator 1/rad 0.060 c172_aero.c e positive down
CL CL lift coefficient vs. angle of attack - 
 alpha     CL  
  -5    -0.14
   0     0.31
  10     1.21
  12     1.276
  13.75  1.51249
  15     1.591
  16     1.63
  17.35  1.60878
  18     1.53712
  19     1.376
  20     1.142
 c172_aero.c in deg
CL 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
CLe CL_de lift due to elevator 1/rad 0.430 c172_aero.c e positive down
Cm0 Cmo pitch moment coefficient at =0 - -0.015 c172_aero.c
Cm Cm_a pitch moment due to angle of attack 1/rad -0.89 c172_aero.c
Cm 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
Cme Cm_de pitching moment due to elevator 1/rad -1.28 c172_aero.c e positive down
CY 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
CYa CY_da side force due to aileron 1/rad 0 c172_aero.c a positive
right aileron up
CYr CY_dr side force due to rudder 1/rad 0.187 c172_aero.c r positive left
Cl 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
Cla Cl_da roll moment due to aileron 1/rad -0.178 c172_aero.c a positive
right aileron up
Clr Cl_dr roll moment due to rudder 1/rad 0.0147 c172_aero.c r positive left
Cn 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
Cna Cn_da yaw moment due to aileron 1/rad 0.053 c172_aero.c a positive
right aileron up
Cnr Cn_dr yaw moment due to rudder 1/rad -0.0657 c172_aero.c r positive left

Flight Sim Home * Aircraft Models * Cessna 172 Model * Cessna 172 References