The Drive Towards More-Electric Aircraft
Dominic Cartwright, VP Business Development of TT Electronics, talks about the increasing electrification of aircraft
Dominic Cartwright, VP Business
Development of TT Electronics
TT Electronics is heavily involved in the move towards more-electric aircraft (MEA) design. The reasons behind MEA are simple: to reduce the weight of the aircraft, and so minimise fuel consumption and cut harmful greenhouse gas emissions.
Traditionally, aircraft systems have been driven by a combination of hydraulic, pneumatic, mechanical and electrical technologies. But recent technological advances in the field of power electronics, including electro-hydrostatic actuators, high-density electric motors, and new power generation and distribution systems, mean the MEA has become a reality.
The origins of MEA lie back in the early 2000s when the More Open Electrical Technologies (MOET) project was launched. This was a joint development project formed by 61 companies in the EU, aimed at establishing a new industrial standard for electrical systems design in commercial aircraft.
The plan was to strengthen the competitiveness of the aviation industry, reduce aircraft emissions and improve operational aircraft capacity. But there were other added benefits, such as improving maintenance requirements and reliability.
MEA is not a new concept – the Avro Vulcan’s electrohydraulic-powered flying control units (PFCUs) were designed in the UK back in the early 1950s. My experience of the more-electric aircraft goes back to the time when TT Electronics was involved in the design of the Airbus A380. The aircraft was so big that a more-electric approach was needed to keep the maximum take-off weight as low as possible. The A380’s wingspan is about 262ft (80m) – nearly the size of a football field – and its length is slightly less, making it the largest conventionally configured aircraft ever built.
The A380 introduced the use of electro-hydrostatic actuators (EHAs). EHAs are electrically powered, but use smaller hydraulic pumps and reservoirs that transform electrical power into hydraulic power. Airbus said the combination of higher hydraulic pressures and more electric flight control architecture led to a weight reduction of approximately 3,307 lb (1,500kg) for the aircraft.
TT Electronics now has components on the aircraft that enable fuel pumping and fuel control, and electromagnetic components that control the primary flight surfaces, including the ailerons, rudder and elevator.
The knowledge we gained through the A380 programme helped us develop other innovations, such as electric thrust reverser actuation. Like any aeronautical development, it’s a case of evolution not revolution.
Our knowledge has also been transferred into the military aircraft sector, where lower-weight components give fighter aircraft greater agility.
Our product line now comprises everything from cockpit and engine controls, through dynamic braking resistors for aircraft flight surface controls, to power modules and connectors for avionics and flight systems.
One of the challenges with more-electric aircraft design is dealing with the heat generated within components. Just as your body gets hot when you exercise, electric currents can generate a lot of waste heat that has to be dissipated. We’ve developed a number of innovative ways of doing this, such as adding heat sinks to the bottom of assemblies and using special resins over much larger surface areas. We continue to innovate in this field.
Another development has been the increasing use of composite materials for the aircraft’s skin and other components. Although this has helped reduce the weight of the aircraft considerably, it does throw up other issues surrounding the electrical characteristics of the air frame. For example, as composites can’t conduct electricity you no longer have the Faraday cage effect you get when metal surrounds electrical components, and which protects them from nearby strong electric fields. We’ve worked hard to find ways to minimise these effects and make sure that components are protected.
More aerodynamic wing design has also meant there is less space to fit components, so we have had to concentrate not only on losing weight, but also on making things smaller. For example, we reduced the footprint of the power control module for the Rolls-Royce Trent XWB engine on the Airbus A350 by 70%.
In terms of electrical power actuation there are still some pretty big hurdles to overcome in terms of improving reliability and overcoming initial ‘stiction’ – the challenge of overcoming friction to get mating surfaces to start to move.
We’ve enabled electric spoilers on aircraft and we’ve put electric back-ups onto rudders and ailerons, but we’ve always had primary hydraulic actuation.
One of the biggest reasons the MEA approach hasn’t taken off more quickly in civil aerospace applications is landing gear systems. As long as they remain heavy you’ll still need hydraulic power to lift them, but there are global organisations working on a solution for this now. But that doesn’t stop us looking at the problem and asking ‘what if’ questions for future MEA developments.
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