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F-104 Starfighter -- 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 2, 2000

The linear aerodynamics model uses stability derivatives to approximate actual aircraft behavior. The F-104 linear model is based on the following flight conditions (cruise):

Variable	Variable in Code	Description	Units	Value(s)	Source	Notes
Flight Conditions
h	Altitude	altitude above sea level	ft	55000	Roskam pg 529
	Alpha	angle of attack	deg	2	Roskam pg 529
V	V_true_kts	velocity (true air speed)	kts	1031.4	Roskam pg 529	Mach 1.8
q	Dynamic_pressure	dynamic pressure	lb/ft²	434.5	Roskam pg 529
C.G.	-	center of gravity location	%	7	Roskam pg 529
C_L	CL	lift coefficient	-	?		not available
C_D	CD	drag coefficient	-	?		not available
C_m	Cm	pitching moment coefficient	-	?		not available

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

Variable	Variable in Code	Description	Units	Value(s)	Source
Geometry
b	bw	wingspan	ft	21.9	Roskam pg 529
	cbar	wing mean aerodynamic chord	ft	9.6	Roskam pg 529
S	Sw	wing surface area	ft²	196	Roskam pg 529

Control Surface Geometry

Variable Variable
in Code Description Units Value(s) Source Notes

e_max demax maximum elevator deflection deg +20 - guess

e_min demin minimum elevator deflection deg -20 - guess

a_max damax maximum aileron deflection deg +20 - guess

a_min damin minimum aileron deflection deg -20 - guess

r_max drmax maximum rudder deflection deg +20 - guess

r_min 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 16300 Roskam pg 529 converted to Mass
[slug/ft³] in code

I_xx I_xx roll inertia slug ft² 3600 Roskam pg 529

I_yy I_yy pitch inertia slug ft² 59000 Roskam pg 529

I_zz I_zz yaw inertia slug ft² 60000 Roskam pg 529

I_xz I_xz lateral cross inertia slug ft² 0 Roskam pg 529

Propulsion Data

Variable Variable
in Code Description Units Value(s) Source Notes

T_max simpleSingleMaxThrust maximum thrust lb 5050 Roskam pg 530 estimated from C_{T_x}
at sea level

T_max simpleSingleMaxThrust maximum thrust lb 7800 MAM site engine rating
(F-104A)

T_max simpleSingleMaxThrust maximum thrust lb 15800 MAM site engine rating
(F-104G)

T_max simpleSingleMaxThrust maximum thrust lb 18800 MAM site engine rating
(F-104S)

Aerodynamic Data

Variable Variable
in Code Description Units Value(s) Source Notes

C_D₀ CDo drag coefficient at =0 - 0.048 Roskam pg 530

C_D CD_a drag curve slope 1/rad 0.384 Roskam pg 530

C_{D_e} CD_de drag due to elevator 1/rad 0 Roskam pg 530 e positive down

C_L₀ CLo lift coefficient at =0 - 0.122 Roskam pg 530

C_L CL_a lift curve slope 1/rad 2.005 Roskam pg 530

C_L CL_adot lift due to angle of attack rate 1/rad 0.82 Roskam pg 530

C_{L_q} CL_q lift due to pitch rate 1/rad 1.9 Roskam pg 530

C_{L_e} CL_de lift due to elevator 1/rad 0.523 Roskam pg 530 e positive down

C_m₀ Cmo pitch moment coefficient at =0 - -0.028 Roskam pg 530

C_m Cm_a pitch moment due to angle of attack 1/rad -1.308 Roskam pg 530

C_m Cm_adot pitch moment due to angle of attack rate 1/rad -2.05 Roskam pg 530

C_{m_q} Cm_q pitch moment due to pitch rate 1/rad -4.83 Roskam pg 530

C_{m_e} Cm_de pitching moment due to elevator 1/rad -1.31 Roskam pg 530 e positive down

C_Y CY_beta side force fue to sideslip angle 1/rad -1.045 Roskam pg 531

C_{Y_p} CY_p side force due to roll rate 1/rad 0 Roskam pg 531

C_{Y_r} CY_r side force due to yaw rate 1/rad 0 Roskam pg 531

C_{Y_a} CY_da side force due to aileron 1/rad 0 Roskam pg 531 a positive
right aileron up

C_{Y_r} CY_dr side force due to rudder 1/rad 0.87 Roskam pg 531 r positive left

C_l Cl_beta dihedral effect 1/rad -0.093 Roskam pg 531

C_{l_p} Cl_p roll damping 1/rad -0.272 Roskam pg 531

C_{l_r} Cl_r roll moment due to yaw rate 1/rad 0.154 Roskam pg 531

C_{l_a} Cl_da roll moment due to aileron 1/rad -0.0173 Roskam pg 531 a positive
right aileron up

C_{l_r} Cl_dr roll moment due to rudder 1/rad 0.0079 Roskam pg 531 r positive left

C_n Cn_beta weathercock stability 1/rad 0.242 Roskam pg 531

C_{n_p} Cn_p adverse yaw 1/rad -0.093 Roskam pg 531

C_{n_r} Cn_r yaw damping 1/rad -0.649 Roskam pg 531

C_{n_a} Cn_da yaw moment due to aileron 1/rad -0.0025 Roskam pg 531 a positive
right aileron up

C_{n_r} Cn_dr yaw moment due to rudder 1/rad -0.0435 Roskam pg 531 r positive left

F-104 Starfighter -- Linear Model

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