JSBSim Aerospace 6-DOF Flight Dynamics (.xml)

@modelscript/jsbsim (languages/jsbsim) provides zero-regex XML parsing, non-linear 6-DOF rigid-body flight dynamics integration, cruise trim stabilization, linear DAE lowering, and Modelica 3.x projection for JSBSim Flight Dynamics Model (FDM) fixed-wing and rotorcraft aircraft configurations.

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Supported Extensions & Standards

Extension	Format	Description
.xml	JSBSim FDM XML	Aircraft configuration schema encoding metrics, mass balance, propulsion, landing gear, and aerodynamic tables

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Key Capabilities

1. Six-Degree-of-Freedom (6-DOF) Non-Linear Equations of Motion

• Integrates the full non-linear Newtonian equations of motion for a rigid aircraft in atmospheric flight:
  • Translational Accelerations in Body Frame:$$\dot{u}=\frac{F_x}{m}-qw+rv$$$$\dot{v}=\frac{F_y}{m}-ru+pw$$$$\dot{w}=\frac{F_z}{m}-pv+qu$$
  • Rotational Accelerations in Principal Axes:$$\dot{p}=\frac{M_x}{I_{xx}}+\frac{I_{yy}-I_{zz}}{I_{xx}}qr$$$$\dot{q}=\frac{M_y}{I_{yy}}+\frac{I_{zz}-I_{xx}}{I_{yy}}pr$$$$\dot{r}=\frac{M_z}{I_{zz}}+\frac{I_{xx}-I_{yy}}{I_{zz}}pq$$
  • Euler Angle Kinematics:$$\dot{\varphi }=p+(q\sin \varphi +r\cos \varphi )\tan \theta$$$$\dot{\theta }=q\cos \varphi -r\sin \varphi$$$$\dot{\psi }=\frac{q\sin \varphi +r\cos \varphi }{\cos \theta }$$
  • Geodetic Altitude Rate of Climb:$$\dot{h}=u\sin \theta -v\sin \varphi \cos \theta -w\cos \varphi \cos \theta$$

2. Aerodynamics & Steady Cruise Trim

• Models lift ($C_L$), drag ($C_D$), side force ($C_Y$), and moments ($C_l,C_m,C_n$) as functions of dynamic pressure $\overline{q}=\frac{1}{2}\rho V^2$, angle of attack $\alpha =\arctan (w/u)$, and sideslip $\beta =\arcsin (v/V)$:$$C_L=C_{L0}+C_{L\alpha }\cdot \alpha$$$$C_D=C_{D0}+k{C}_L^2$$$$C_m=C_{m\alpha }(\alpha -{\alpha }_{\text{trim}})+C_{mq}\left(\frac{q\overline{c}}{2V}\right)$$
• Computes automatic cruise trim equilibrium where aerodynamic lift cancels aircraft gross weight ($L=mg$):$${\alpha }_{\text{trim}}=\frac{mg-\overline{q}S{C}_{L0}}{\overline{q}S{C}_{L\alpha }}$$ensuring stable horizontal flight without pitch oscillation or kinetic energy loss.

3. Direct DAE Lowering

• Lowers state variables ($u,v,w,p,q,r,\varphi ,\theta ,\psi ,h$) and aero force equations into @modelscript/runtime's DAEBuilder linear memory arena.
• Enables co-simulation between aerodynamic airframes, onboard flight control computers (@modelscript/simulink), and satellite navigation systems (@modelscript/ccsds).

4. Bidirectional Modelica 3.x Projection

• Projects JSBSim aircraft into Modelica.Mechanics.MultiBody 6-DOF airframes with aerodynamic force elements.

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Pre-Flight Diagnostics

The JSBSim linter validates aircraft geometry, mass distributions, and inertia tensors:

10 rules7 error3 warning Run with msx jsbsim lint

Code	Rule	Severity	Message
M8901	missing-aircraft-name	error	JSBSim <fdm_config> element is missing required 'name' attribute.
M8902	non-positive-reference-area	error	Wing reference area (<val>) must be strictly positive.
M8903	non-positive-wingspan-chord	error	Wing metric '<param>' (<val>) must be strictly positive.
M8904	non-positive-empty-weight	error	Aircraft empty weight (<val>) must be strictly positive.
M8905	invalid-inertia-tensor	error	Moments of inertia tensor is invalid: <reason>.
M8906	missing-aerodynamics-section	error	Aircraft model does not define any aerodynamic force/moment coefficients in <aerodynamics>.
M8907	missing-landing-gear	warning	Aircraft model defines no landing gear bogies in <ground_reactions>; ground interaction is disabled.
M8908	negative-engine-thrust	error	Engine '<engineName>' specifies negative maximum thrust (<val>).
M8909	undefined-fcs-input	warning	FCS channel '<channelName>' references input property '<inputProperty>' not bound in flight control.
M8910	unrealistic-cg-location	warning	Center of gravity (<cgX>) is significantly far from aerodynamic center (<aeroX>); aircraft may have extreme pitch instability.

Generated from languages/jsbsim/src/errors.ts. All languages →

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CLI Usage

# Inspect aircraft metrics, mass balance, engines, and aero coefficients
msx jsbsim inspect Cessna172Skyhawk.xml

# Run pre-flight linting and inertia tensor validation
msx jsbsim lint Cessna172Skyhawk.xml

# Simulate 6-DOF flight dynamics with automatic cruise trim
msx jsbsim simulate Cessna172Skyhawk.xml --duration=15.0 --speed=180.0 --altitude=5000.0

# Lower 6-DOF flight dynamics equations to ModelScript linear DAE arena
msx jsbsim to-dae Cessna172Skyhawk.xml

# Project into Modelica 3.x 6-DOF flight mechanics model
msx jsbsim to-modelica Cessna172Skyhawk.xml -o FlightMechanics.mo