BAE Systems’ reconfigurable simulator of a jet fighter shows the future of physical testing is bright.
Engineers must consider that not all simulations live within the confines of a digital system—or your classic CAE software. In industries like automotive and aerospace, reconfigurable physical simulators are being used to help engineers, test pilots and designers optimize their designs.
One perfect example of this is with a flight simulator from BAE Systems. It is currently helping design teams rapidly assess the flight control systems for the Tempest, a sixth-generation fighter aircraft being co-developed by Italy, the U.K. and Japan. The physical simulator acts as a bridge between digital and physical testing while still bypassing the expenses of manufacturing a bespoke physical prototype for each test. It also brings humans-in-the-loop so they can feel, for themselves, the performance of current design iterations.
“It allows our engineers and test pilots to fly the aircraft in a virtual environment, allowing them to test and develop flight control systems for Tempest,” says Jon Wiggall, Test and Evaluation Integrated Product team lead for BAE Systems’ FalconWorks office. “The rigs use a combination of aircraft hardware and digital models.” According to BAE Systems, changes made to the Tempest design are reflected in the physical simulator.
The simulator also helps code safety-critical, systems software automatically. Wiggall adds, “This enables rapid assessment of the flight control systems during more complex flight maneuvers, with the simulator capturing crucial data about how the jet will handle and perform, years before its first flight.”
Clearly, digital CAE simulations have not eliminated physical prototyping, as some predicted. Instead, they can be merged with physical simulators to simplify and streamline the testing process.
The Benefits of Reconfigurable Physical Simulators
BAE Systems calls its simulator the Tempest combat technology demonstrator (CTD). The use of simulators such as this has grown in popularity due to increased Industry 4.0 practices; namely, the collection and use of digital data to drive intelligent design via physical prototypes or assets in the field.
For instance, BAE Systems has found that this practice has been particularly advantageous for the development of safety systems software.
“The flight control software is designed and developed as part of a model-based design process,” says Wiggall. “The design is captured as a set of models that can be readily included as part of an aircraft simulation model for assessment on the desktop computer in the office, or a flight simulator.”
“The toolset supports autocoding of these same software models into actual code that can be loaded directly on to the flight control computer hardware, avoiding the historical time-consuming overhead of having to hand code the software specification into code that is suitable for the flight control computer. This auto coding process consequently allows for design changes to be assessed quickly and any potential issues to be identified much earlier in the lifecycle,” he says.
In effect, test pilots complete assessments of the simulator’s handling, performance and flying qualities. Engineers then feed this information into the development of new software. With traditional physical prototypes this could take weeks, maybe months. But now the team can perform these tasks in days.
Generally, BAE’s work on Tempest reveals the utility of hardware-in-the-loop and human-in-the-loop simulations for aircraft manufacturers. The combination of the real hardware of the simulator and the digital engineering simulation makes it easier to improve how plane controllers respond in real time to realistic stimuli like cloud cover, turbulence or weakened radar signals.
“This technique enables the interfaces between the systems to be evaluated and proven earlier in the lifecycle, providing confidence in system design much earlier in the program, reducing costs and development time,” says Wiggal.
How the Tempest Combat Technology Demonstrator Works
BAE’s simulator is comprised of a utility management system, a cockpit with flight control systems and hydraulics systems. These rigs can work independently or be combined to model the overall system.
“The simulator utilizes three key models—[an] aerodynamic dataset, [a] propulsion model and [an] undercarriage model—that generate six forces and moments,” says Wiggal. “The aerodynamic dataset is derived from a combination of both computational fluid dynamics modelling and wind tunnel testing. The six forces and moments from these models are summed together and used within equations of motion to determine aircraft motion. [Then] the atmosphere and earth models are all based on physics models.”
Each rig uses a combination of aircraft hardware and digital simulations. For example, BAE Systems’ virtual cockpit relies on computer game technology. The device simulates the controls a pilot needs to fly a craft through a helmet visor.
“As the three key models are refined during the engineering development lifecycle, the simulator model is also updated to reflect these changes so that all of the engineering team continues to work with the latest available dataset,” adds Wiggal. “Work in the rigs is an ongoing part of our technology de-risking … The simulator, hardware and software will evolve over time as work on the [CTD] progresses towards first flight and beyond.”
BAE Systems expects the rigs to evolve to evaluate hardware, including cockpit displays and best practices, like emergency procedures. The test pilots and engineers on the flight test team can then train and rehearse representative missions ahead of real flight trials.
“Test pilots from BAE Systems, Rolls-Royce [producers of the aircraft’s engine] and the UK’s Royal Air Force (RAF) have already flown more than 150 hours [in] the [CTD] completing handling, performance and flying qualities evaluations.”
As Physical and Digital Simulations Get Better, So Do the Engineers
BAE believes that an aircraft engineer’s journey to improve a craft like Tempest also gives that professional a broader and deeper understanding of knowledge. This work should also increase their flexibility. This will allow them to perform more duties on future projects.
“Engineers are being exposed to a much broader spectrum of engineering, much earlier in the product lifecycle,” says Wiggal. “Eventually, test engineers will get to see the full spectrum of test from simulation to rig design, rig commissioning and test execution through to qualification evidence, aircraft ground test and aircraft flight test. This journey will provide a broader, more knowledgeable engineer that has significantly more flexibility across the engineering team on future projects.”
The main pushback to physical prototypes has always been the time and cost to produce them. This is especially true when the prototype could go up in smoke after a 10 second test. However, BAE systems shows that merging simulation technology with reconfigurable physical assets and human pilots—via human- and hardware-in-the-loop practices—can work to keep the spirit of physical prototypes alive while limiting their drawbacks. The prototype can be reconfigured quickly and there are no risks to people or property as all the tests are governed by digital models.
