Flight Dynamics Model

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A Flight Dynamics Model (FDM) is a set of math equations used to calculate the physical forces acting on a simulated aircraft, such as thrust, lift, and drag. Every aircraft simulated by FlightGear must use one of these models. FlightGear supports several different types of flight dynamics models.

Flight Dynamic Models

Integrated FDMs

Currently (March 2020) FlightGear comes with these FDMs:

Was originally developed specifically for FlightGear, and has been the default FlightGear flight dynamics model since 2000.
In addition to airplanes JSBSim also supports rockets, helicopters and lighter than air aircraft (and to some extent water-craft and land vehicles).
Is yet another FDM using different calculation methods. YASim supports airplanes and helicopters. It was introduced in FlightGear version 0.7.9 in 2002.

Historical FDMs

Historically FlightGear have also been able to use these FDMs, but while the source code is still there they are no longer built by default:

Was originally developed by NASA, and was the first FlightGear FDM, now replaced by JSBSim and YASim.
Was developed by the UIUC Applied Aerodynamics Group at University of Illinois, based on LaRCsim.
It includes additional features, such as the ability to simulate aircraft icing. UIUC lacks ground interaction.

Other FDMs

There are also other ways to set up an FDM:

External FDMs
FlightGear can also be set up to render using inputs from an external FDM source, such as from MATLAB.
Custom FDMs
Other custom FDM have been written for specific aircraft types, such as for hot air balloons.
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