Flight simulation models are used throughout the aircraft industry including aircraft subsystem design; control system development; training simulation; cockpit display development; accident analysis; and within avionics integration labs and iron bird labs for production and development testing of devices and software. Although aircraft companies usually develop and maintain their own aircraft model library there is demand for an externally-developed aircraft model library by companies developing aircraft subsystems and also by emerging market aerospace companies in the process of building their set of technology assets.
In this paper we describe the design and on-going development of an integrated real-time capable aircraft model for use in aircraft system development, test and integration. The library was developed for desktop simulation as well as real-time simulation with hardware-in-the-loop. Several features are necessary to provide efficiency during test initialization and running. Real-time capability is necessary for use in testing of actual aircraft subsystems such as line replaceable units, avionics, actuators and for pilot-in-the-loop applications. Real-time capability places constraints on the model library mainly because each simulation cycle is completed in the same amount of time as the integration step-size. The model architecture should provide good accessibility and flexibility to both the user and the developer. Access to differential equation integrators is required for trimming and reinitializing the aircraft when the simulation is on-line. Access to scalar and table parameters when the simulation is on-line is necessary for efficiency. The model library must provide subsystem modules so that a developer can integrate with and replace library modules with in-house developed subsystem models and eventually with external devices under test. The each component of the model must expose the data required to model the aircraft communication, control systems, and networking. The structure of the model must support rapid reconfiguration for many different test scenarios and must not require recompile of the model in order to initialize test cases. This paper explores the considerations in the design of an integrated aircraft simulation model, discusses the trade-offs, and discusses the results of our development effort.