Farnborough International Airshow (FIA) saw the reappearance of Airbus’ E-Fan, 2-seater all electric prototype aircraft. It may be a stepping stone to commercial viability of small electric aircraft, and perhaps a smaller step along the longer path towards all electric airliners, and in fact it is clear that such outcomes are regarded as inevitable by many in the avionics sector.
It will, however, be a long path and it is incumbent on companies such as Raytheon to develop the technologies that will be adopted as aircraft evolve with more electric systems. Steve Clerkin is Raytheon UK's business sector lead (Aviation Electrical Power Systems), Integrated Power Solutions, and his team were launching a couple of products at FIA which he believes could play a part in this evolution.
“Boeing and Airbus have put aircraft out there that are partially electric,” said Clerkin. “The 787's got an awful lot of power electronics on it and it's capable of generating 1.5 megawatts of electrical energy off its generator, for instance. For all that it is at one end of the spectrum, it's an awful lot of electricity and an awful lot of power to manage. I don't think every aircraft from now on will have that same amount of energy consumption, but the 787 has got electric systems on everything.”
The drive towards More Electric comes from a need to be lighter, more efficient, more reliable and greener. But even then operators are asking for more. Clerkin said: “All of those things are what attract the operators to select which aircraft they are going to buy, but also they want an environment where it's quick to assemble, quick to maintain, and faster turnaround. That's where electric comes in.”
The next generations, or replacements, for aircraft such as the Airbus A320 or Boing 737 are those that are likely to be the ones that will feature more electric systems. “You've got on those aircraft the number of hours, the number of people, the economics to make it worthwhile to invest in saving every kilogram of weight that you can,” claimed Clerkin. “It's the operating costs that are the most compelling. So if you want to take mechanical off and put electric on, it's got to have some benefit – lighter, more reliable, easier to maintain and reduce fuel burn. So that generation is likely to be the next truly More Electric platform.”
The product Raytheon was demonstrating at FIA was a primary power converter. Scalable to 90kW, this bi-directional non-isolated power supply is capable of converting 3-phase 115V AC generator supplied power into 540V DC (to meet the aircraft’s varying electrical load requirements) and also converting DC into 3-phase AC for engine start duty; i.e. the generator becomes a motor. In addition, the converter utilises Silicon Carbide power semiconductors, high frequency switching and liquid cooling to minimise size and weight.
Raytheon’s primary power converter utilises Silicon Carbide power semiconductors to minimise size and weight.
The development of the demonstration converter incorporates technology developed during a series of Aerospace Technology Institute (ATI) / Innovate UK funded projects including the Rolls-Royce led ‘Siloet2’ project and the Airbus led Integrated Power & Propulsion Architectures (IPPA) project, which is providing aerospace engineers with data to optimise tomorrow’s aircraft electrical systems for greater efficiency, minimised emissions and reduced operating costs. Also, IPPA has brought together UK suppliers for many of the major elements in an aircraft’s electrical system, including engines, generators, power distribution and electrical loads (such as motors and actuators).
“Raytheon’s role within IPPA has been to help develop a clear understanding of how the More Electric Aircraft’s power architecture can be modelled and subsequently optimised” said Dr Grant MacLean, Technical Lead for Power & Control within Raytheon’s IPS business unit. “We’re now bringing our power design expertise, which ranges from semiconductor fabrication through to system-wide power architecture modelling, to develop fit-for-purpose, reliable and high-density power converters and other products to support the More Electric aircraft.”
Raytheon believes it is out on its own in terms of power conversion and power conditioning in such harsh environments. Clerkin observed: “Some of the other businesses in trains and transportation and so on are probably doing equivalent systems but not in the same harsh environment, and certainly not the same altitude, temperature range, EMC and EMI challenges that we have to overcome on an aircraft. Those industries can do great power conversion, but they don't have all of the restrictions that we are exposed to in aerospace.
Current designs are aimned at the Nore Electric aircraft. “What we have to have is scalable equipment,” claimed Clerkin, “so we don't have to redefine every time. We can design something that will deliver 100 kW or we can scale it up to a couple of hundred kilowatts and that's probably good enough for what the market needs today.
However, to get the architecture working on the aircraft it requires collaboration with other supply partners, as Clerkin described: “There is no point of designing in isolation. An electrical system should be treated like an entire system end-to-end, from a generator all the way to the galley. Certainly for the major loads like wing de-icing and air conditioning, you have to understand the behaviour of the entire system for you to be able to design the right equipment and optimise your equipment throughout that design cycle. If not, you'll get 15 or 20 people who are all designing in isolation and everybody will build in redundancy, everybody will build in risk and your equipment will be possibly twice the size and weight that it needs to be for the aircraft.
“So collaborative efforts, working with innovative planners and people that want to come together to put a compelling bid together, that's the way to really put a system together for tomorrow's more electric aircraft.”
The 787 Dreamliner can generate 1.5MW off its generator.
Virtual design at Airbus Group Using virtual or augmented reality in the design process is emerging as a useful tool for assessing customer or user acceptance. But so far its use directly as a design tool is in its infancy. One company that has embraced the technology and its possibilities is Airbus Group, as Paul Hannah, creative director of future concepts, explained: “There are applications already that allow you to edit and work within the 3-D environment and create a model, all within that. There is a possibility to allow a customer to go into a cockpit or into a cabin and allow them to be modifiable in real time.” The programme Airbus Group uses is Unity, which is primarily a games engine. “It's a very powerful engine and allows for very quick prototyping,” continued Hannah. “It allows for very quick build times and then you can take that information, export it and then use it inside the CAD environment for more rigorous testing. But all of those systems like Unity and Unreal Engine have mechanisms to allow the designers to go in and actually work within the 3-D virtual space. Andrew Anderson, who is COO of the company’s Corporate Technology Office, commented: “I think what we're doing at the moment in virtual reality is really exciting. Understanding how we can use products in the future, how we come together with customers to find requirements for missions and products - those are really good things. “We use it as a design tool. We use it in defining mission situations with customers. And we use it also in maintenance scenarios as well. So there are three areas at the moment that it's being used in and growing very fast.” |