Fig 3: Structure of ATTAS and HESTOR simulation facility
The structure of the simulation facility is mostly identical for ATTAS and HESTOR, Fig. 3. The 6 degrees-of-freedom aircraft simulation as well as the 9 degrees-of-freedom helicopter simulation with main and tail rotor include engine, actuator, and atmosphere models. They run in real-time on a high performance simulation computer RTS (Real Time Station) that is supported by a powerful commercial software development tool, called SIMsystem, which is hosted by a UNIX workstation. The VME-Bus Interface Computers (Aircraft Interface Computer; AIC; and Helicopter Interface Computer; HIC) are the central data conditioning and distribution multiprocessor systems. The AIC simulates sensor and avionic systems characteristics whereas the HIC performs the tasks of data acquisition and distribution and of the simulation of the functionality of the cockpit interface including the procedures for switching between various operation and trim modes. All data that are available in the on-board systems are provided on the ground simulators in the same data formats (e.g., ARINC 429, MIL-Bus 1553B). In the case of ATTAS, the sensor data interfacing even has airplane-identical connectors so that on-board computers can be connected to the simulator for failure identification purposes. The on-board computer systems are represented as hardware-in-the-loop elements in the ground based simulators. In contrast to the rugged flight-certified on-board systems; for cost reasons, they are based on commercial hardware for the ground simulators. However, they have the same software structure and functionality as their counterparts in the flight vehicles. Software development for the computer systems is accomplished on a Data General mainframe in case of ATTAS and a VME-Bus system in case of HESTOR.