Learjet 24 -- 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 May 31, 2000

The linear aerodynamics model uses stability derivatives to approximate actual aircraft behavior. The Learjet 24 linear model is based on the following flight conditions (maximum weight cruise):

Flight Conditions
Variable Variable
in Code 		Description Units Value(s) Source Notes
h Altitude altitude above sea level ft 40000 Roskam pg 522
Alpha angle of attack deg 2.7 Roskam pg 522
V V_true_kts velocity (true air speed) kts 400.9 Roskam pg 522 Mach 0.7
q Dynamic_pressure dynamic pressure lb/ft2 134.6 Roskam pg 522
C.G. - center of gravity location % 32 Roskam pg 522
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 34 Roskam pg 522
cbar wing mean aerodynamic chord ft 7 Roskam pg 522
S Sw wing surface area ft2 230 Roskam pg 522

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 13000 Roskam pg 522 converted to Mass
[slug/ft3] in code
Ixx I_xx roll inertia slug ft2 28000 Roskam pg 522
Iyy I_yy pitch inertia slug ft2 18800 Roskam pg 522
Izz I_zz yaw inertia slug ft2 47000 Roskam pg 522
Ixz I_xz lateral cross inertia slug ft2 1300 Roskam pg 522

Propulsion Data
Variable Variable
in Code 		Description Units Value(s) Source Notes
Tmax simpleSingleMaxThrust maximum thrust lb 2020 Roskam pg 523 estimated from CTx
at sea level
Tmax simpleSingleMaxThrust maximum thrust lb 5900 David pg 559 engine rating
(Learjet 24F)

Aerodynamic Data
Variable Variable
in Code 		Description Units Value(s) Source Notes
CD0 CDo drag coefficient at =0 - 0.0216 Roskam pg 523
CD CD_a drag curve slope 1/rad 0.3 Roskam pg 523
CDe CD_de drag due to elevator 1/rad 0 Roskam pg 523 e positive down
CL0 CLo lift coefficient at =0 - 0.13 Roskam pg 523
CL CL_a lift curve slope 1/rad 5.84 Roskam pg 523
CL CL_adot lift due to angle of attack rate 1/rad 2.2 Roskam pg 523
CLq CL_q lift due to pitch rate 1/rad 4.7 Roskam pg 523
CLe CL_de lift due to elevator 1/rad 0.46 Roskam pg 523 e positive down
Cm0 Cmo pitch moment coefficient at =0 - 0.05 Roskam pg 523
Cm Cm_a pitch moment due to angle of attack 1/rad -0.64 Roskam pg 523
Cm Cm_adot pitch moment due to angle of attack rate 1/rad -6.7 Roskam pg 523
Cmq Cm_q pitch moment due to pitch rate 1/rad -15.5 Roskam pg 523
Cme Cm_de pitching moment due to elevator 1/rad -1.24 Roskam pg 523 e positive down
CY CY_beta side force fue to sideslip angle 1/rad -0.73 Roskam pg 524
CYp CY_p side force due to roll rate 1/rad 0 Roskam pg 524
CYr CY_r side force due to yaw rate 1/rad 0.4 Roskam pg 524
CYa CY_da side force due to aileron 1/rad 0 Roskam pg 524 a positive
right aileron up
CYr CY_dr side force due to rudder 1/rad 0.14 Roskam pg 524 r positive left
Cl Cl_beta dihedral effect 1/rad -0.11 Roskam pg 524
Clp Cl_p roll damping 1/rad -0.45 Roskam pg 524
Clr Cl_r roll moment due to yaw rate 1/rad 0.16 Roskam pg 524
Cla Cl_da roll moment due to aileron 1/rad -0.178 Roskam pg 524 a positive
right aileron up
Clr Cl_dr roll moment due to rudder 1/rad 0.019 Roskam pg 524 r positive left
Cn Cn_beta weathercock stability 1/rad 0.127 Roskam pg 524
Cnp Cn_p adverse yaw 1/rad -0.008 Roskam pg 524
Cnr Cn_r yaw damping 1/rad -0.2 Roskam pg 524
Cna Cn_da yaw moment due to aileron 1/rad 0.02 Roskam pg 524 a positive
right aileron up
Cnr Cn_dr yaw moment due to rudder 1/rad -0.074 Roskam pg 524 r positive left

Flight Sim Home * Aircraft Models * Learjet 24 Model * Learjet 24 References