JSBSim

JSBSim is an open-source flight dynamics engine designed to model the six-degree-of-freedom motion of aircraft in real time. It provides the physics core used by several flight simulators and can also be used as a standalone dynamics engine or as a library integrated into other applications. The engine is best known for its role in the FlightGear open-source simulator, where it serves as the primary flight dynamics model for a wide range of aircraft, though it is not limited to that project.

JSBSim solves the equations of motion for an aircraft subject to aerodynamic, propulsion, gravitational, and environmental forces. Aircraft models are defined in XML files that describe mass properties, inertia, aerodynamic derivatives, control surfaces, actuators, and propulsion systems, as well as environmental conditions such as wind. The engine supports nonlinear aerodynamics, rigid-body dynamics, gravity, and actuator dynamics, with configurable time stepping for real-time or accelerated execution. It exposes interfaces for autopilots, sensor models, and external controls, enabling integration with external software components.

Implementation and availability: The core is written in C++ and is portable across major platforms, including Linux, Windows, and macOS. It is distributed as open-source software and maintained by the aviation simulation community through public repositories and contributions from volunteers. Aircraft models implemented in JSBSim cover a range of configurations, enabling simulations from light trainers to complex airframes.

Relation to FlightGear: While closely associated with FlightGear, JSBSim is an independent project that can be embedded in other simulators. Its modular architecture supports swapping wind models, environmental scenarios, and control systems without changing the underlying physics engine.