In a rapidly changing world with emerging disruptive technologies, having an aircraft capable of modifying its squadron-level capabilities, such as radar and weapon settings, in a simple and quick way, allows the warfighter to stay relevant, which is of paramount importance. “Incremental development, modular hardware and software, and layered systems architecture provide the ability for continuous growth throughout the life cycle at an increasing rate,” said Johan Segertoft, vice president and head of Gripen Weapon Design business unit at Saab Aeronautics, addressing the issue of flexibility. a design philosophy that Saab began to apply since the Viggen era. “We started focusing on the Gripen E avionics system in 2010, and looking back, we saw three key things we needed to take care of,” he says. While many factors, e.g. thrust to weight ratio, have grown linearly over the years and are therefore predictable, this was not the case for computing power per dollar as this grew exponentially. . The second problem is complexity, which is related to the type of computer we have now, compared to 10 years ago, again an exponential increase. What we have new is that we were going to get something better,” so modularity allows legacy hardware to be replaced with state-of-the-art hardware. These two problems are not unique to aviation. “The third issue, and this one is unique to aviation, is safety. It’s very time consuming because systems have to be certified, flight critical software has to run for 1,000 years, 365 days a year, 24/7, and during that time you’re allowed to have a error”, Johan Segertoft points out, adding that this error must be mitigated so as not to cause disaster.
Regarding the Gripen E, he explains that “here the avionics are not only integrated, they are also distributed, because we have completely separated the hardware from the software, and we have also encapsulated the flight critical elements tactical elements. EDR On-Line understood that during development missions, the aircraft operates with flight-critical software running on prototype software, thanks to the aforementioned avionics platform, which at Saab is known as DIPS (Distributed Integrated Platform Software). “It gives us speed of development, the possibility to try new things, while remaining completely safe”, explains Johan Segertoft, adding that “we can exchange computers, and we did it to obtain more power from For example, we had three computers and we saw that we needed several treatments, so we changed them in a few days, virtualizing new ones to 96 computers, obtaining the power of almost 300 computers. We are the only company to do this, as it is incredibly difficult, the tricky part being formal verification, as we have developed a system that re-verifies itself all the time and is assured to the highest level of RTCA DO-178B so we had to work with the authorities because the standards did not call for such a difficult system, and the Tempest FCAS PYRAMID Open Mission System program apparently follows our vision.
The Gripen E is obviously designed for typical linear growth, but the software expert Saab points out that the avionics platform responds to exponential growth. Aircraft sensors and actuators communicate through a data point making all information available to all software making the system sensor agnostic with the developer only needing an API (Application Programming Interface) and of a development kit. All of this speeds up the upgrade process; “in a normal plane, new developments are first tested in a platform, which runs on UNIX stations that interpret binary numbers backwards like Linux, so you have to compile twice, and in doing so, you can introduce errors, because the software running in the platform is not the same as the one running on the plane, whereas in our system, you only compile once, and the engineers can “steal” it on their own computers, which reduces complexity.” To illustrate the benefits of the system, Johan Segertoft reviews the development schedule.
“We started in 2010, and the first seven years were blood, sweat and tears. Then, on June 15, 2017, we flew for the first time with vessel 39-8. About a year later, we flew the 39-9, the second test aircraft, and all of its computers were upgraded. It took less than a week, the rest was more functional growth. We then added all the tactical gear, in a few months, 39-10 fliers in early 2019, then moved to batch number 1 in series. EDR On-Line understood that the first four aircraft of batch #1 are equipped with three heads-down displays (HDD) and an old head-up display (HUD), while the following six aircraft entered service a few months later are equipped with the latest cockpit configuration with small hard drives, a new HUD and the Wide Area Display (WAD).
“It allows you to see the pace of improvement; on average, we have released new flight software every four weeks, we have been doing Agile development since 2010, and this has been possible because the product supports it,” adds the Saab representative. Of course, the customer won’t be updating their aircraft at the same rate, the four-week rate being something used for development. Discussions are ongoing on these aspects with customers, because the Gripen E changes the paradigm even in this aspect, which will consequently change behaviors. “One of our test pilots said that from Christmas 2021 to summer 2022 the plane was a completely different platform, thanks to the number of upgrades induced in the development platforms.”
The developments are the result of beneficial collaboration between Saab and customers, air forces and procurement offices. “In some areas, we have requirements that push us to the limits of what is not feasible today, and we are trying to get closer to them. In the Gripen C/D, which is a very capable aircraft from a software point of view but does not have DIPS, it took about 12 months to test a new idea in a real environment. Now we’ve extended the Agile concept to include the flight test program, which we call ADAPT for Agile Design And Permit To fly, and that makes it possible to do the same test in four weeks, and the fastest addition of a security-critical application took us probably seven to eight days.
Another key issue is the ability to fly in areas without GPS by maintaining precise positioning“because mistakes would immediately affect situational awareness,” Jussi Halmetoja points out.
Due to his operational experience, he could not avoid concluding his presentation by talking about training and operations. “To fight effectively and for real, you must train real, with real aircraft in a real environment, against real threats, so don’t replace your training with synthetic or simulated training, these must be combined”, the right mix between real and simulated flight hours being the problem.
 DO-178B is a document jointly developed by the Radio Technical Commission for Aeronautics (RTCA) RTCA SC-167 safety-critical working group and the European Organization for Air Conditioning Equipment WG-12. aviation (EUROCAE) on software considerations in airborne systems. Certification of systems and equipment.
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