Editing Flight simulator (section)

=== Simulation models ===

The central element of a [[simulation]] model are the equations of motion for the aircraft.<ref name="baarspul1990" /> As the aircraft moves through atmosphere it can exhibit both [[six degrees of freedom|translational and rotational degrees of freedom]]. To achieve perception of fluent movement, these equations are solved 50 or 60 times per second.{{r|allerton2009|p=16}} The forces for motion are calculated from aerodynamical models, which in turn depend on state of control surfaces, driven by specific systems, with their avionics, etc. As is the case with modelling, depending on the required level of realism, there are different levels of detail, with some sub-models omitted in simpler simulators.

If a human user is part of the simulator, which might not be the case for some engineering simulators, there is a need to perform the simulation in real-time. Low refresh rates not only reduce realism of simulation, but they have also been linked with increase in [[simulator sickness]].<ref name="pauschLiteratureSurveyVirtual1992">{{cite Q|Q112822678}}</ref> The regulations place a limit on maximum [[Latency (engineering)|latency]] between pilot input and aircraft reaction. Because of that, tradeoffs are made to reach the required level of realism with a lower computational cost. Flight simulators typically don't include full [[computational fluid dynamics]] models for forces or weather, but use databases of prepared results from calculations and data acquired in real flights. As an example, instead of simulating flow over the wings, [[lift coefficient]] may be defined in terms of motion parameters like [[angle of attack]].{{r|allerton2009|p=17}}

While different models need to exchange data, most often they can be separated into a modular architecture, for better organisation and ease of development.<ref name="ippolitoSoftwareArchitectureReconfigurable2000">{{cite Q|Q112822781}}</ref><ref name="oberhauserVirtualRealityFlight2017">{{cite Q|Q112822831}}</ref> Typically, gear model for ground handling would be separate input to the main equations of motion. Each engine and avionics instrument is also a self-contained system with well-defined inputs and outputs.