© Siemens AG

Do we have a choice? I'm certain that we don't. Aviation will increasingly rely on electrical engines. There will be no stopping this development.

Why?

One of the reasons is 'Flightpath 2050', the position paper tabled by the European Commission which specifies ways in which the aviation business will have to change in the future. At the heart of this document is a target for carbon emissions from the sector to be cut by up to 75 percent by 2050, thanks to the use of new technologies and procedures. This is to be achieved over a time span in which experts think the volume of air transport might double.

At present, we are still far away from achieving this in practice. Global passenger transport is dominated by aircraft propelled by gas turbines. Whilst it is true that these turbines have continuously become more efficient and lower in emissions, this alone will certainly not make it possible for us to achieve the targets set out in 'Flightpath 2050'.

We won't be able to cut emissions this drastically without electrifying aviation. Hybrid-electrical propulsion systems use electricity to drive fans or propellers and generate this electricity in gas turbines that can be fine-tuned to deliver the exact output needed for the journey. During the climb phase, additional energy is provided from batteries. Separating energy conversion and thrust generation in this way open up new opportunities in aircraft design. For instance, it makes it possible for the centralised energy conversion system and the decentralised system of electrical thrust generation to be optimised separately. Furthermore, it could be possible to reduce the aircraft's fuel consumption and its emissions by 25 to 50 percent, and to massively reduce noise pollution.

Electrical aircraft have the potential to be much quieter than traditional aircraft. This could benefit people living in the vicinity of airports and open up opportunities for flights to depart and arrive at night where this is currently not permitted under noise-control rules.

So there are clear advantages to using hybrid-electrical propulsion systems. These will, of course, continue to benefit from all future improvements made on gas turbines and sustainable fuels. After all, they will continue to rely on gas turbines for extracting energy from the fuel carried on the aircraft. Having said all this, it won't be possible to electrify the entire aviation sector just like this. New propulsion systems have yet to be brought to maturity and certified, which will require a massive amount of research and development work. But we must take on these challenges. We have no choice. The world is becoming increasingly electrified, whether it is on land, at sea, or in the air.

Dr Frank Anton is Head of eAircraft, Corporate Technology, at Siemens AG.

© MTU Aero Engines AG

Recent discussions about air transport and its environmental impact have often been focused on eAircraft. This is good news, because widespread interest helps spark creativity in research. At the same time, this kind of attention tends to result in high-flying expectations that aren't realistic. This is why we would be well-advised to approach this from a factual angle.

So where are we, in terms of technical development? We are starting to see electrical engines and batteries successfully being used in motorgliders and smaller sporting aeroplanes. Passenger aviation is a whole different story. Bear in mind that the A320neo, for instance, requires 18MW (24,500 PS) of output during start-up; even small short-haul aircraft would have to be fitted with batteries at least 10 times more powerful than today's cutting-edge technology. So far, nobody has even hatched an idea on how this could work in theory. And battery development is not the only major challenge that would have to be overcome. Others include the development of supra-conducting ultra-low-weight eEngines, a whole host of questions around safety and reliability, and the need to fit airports with new infrastructure, which would have to cater to different types of aircraft in parallel and for many years.

Hybrid drive systems might mark a first step towards electrical air transport. Such a system would have to demonstrate that it offers advantages that justify the higher weight and much higher complexity required. There can be no doubt that eAviation is a most challenging choice of technology when it comes to meeting the ambitious environmental targets for the aviation sector in a sustainable way. Achieving this will require a very long phase of technical development.

At the same time, there are already engine solutions for how emissions from conventional aircraft can be reduced quite considerably, for instance the geared turbofan (GTF) engine. Concepts like these must be rigorously and consistently pursued, just like the development of alternative fuels which hardly emit any carbon at all. We are working on all these fronts whilst also keeping eAviation in mind – and it goes without saying that the electricity would have to be generated from sources that are low in emissions.

Dr Rainer Martens is Chief Operating Officer at MTU Aero Engines.