The pioneering spirit has reawoken

Mr Mechler, you are sitting in an aircraft in the year 2050 and flying from Hamburg to Munich. How is it powered?

Probably still by kerosene. It’s highly likely that the aircraft will still have a turbine engine. I believe that the configuration of an aircraft will still be similar to that of today's aircraft even 29 years from now. We provide support in the area of aircraft construction to OEMs such as Airbus and the life span of an aircraft is at least 30 years. However, during this period, sustainable aviation will become increasingly important. I would estimate that, in the year 2050, its market share will be approximately the same as that of battery-powered vehicles in today's automotive market.

As an engineer and the CEO Aerospace at umlaut, you advise both customers such as industry-leading OEMs and aspiring start-ups and newcomers to the aviation industry. What are the challenges that unite these companies?

In all these companies, sustainable aviation is finally encouraging the return of the pioneering spirit. Small manufacturers are showing how a drone or a multi-rotor aircraft can be made from a helicopter – some are venturing further and are powering these machines with batteries, for example the start-up Lilium. Research is also being carried out into new powertrain and sources of energy. You can sense that there is an awakening across the industry and I find that very motivating. The only thing working against this is gravity. When the Wright Brothers first climbed up into the sky in 1903, they didn't know whether they would survive. People flying on vacation today primarily want to arrive safely. How green the flight is, is of secondary importance. Today every flight, and every test flight, must be safe. That's the top priority – and this costs time and money.

Apropos time. Preventing runaway climate change requires fast action. Are there any alternative drive systems that can be realised quickly?

It will be a good ten years before new aviation ideas are ready for the market. I believe that, in the short term, we will first of all see more efficient engines in the sky – there is potential for reducing fuel consumption through the use of open rotor concepts, improved or additional gearboxes, aerodynamic leading edges, as well as lighter and extremely rigid materials, they will above all increase efficiency. Today there are more than 25,000 aircraft in the skies which are able to carry more than 100 passengers and a small proportion of these are already flying with so-called geared turbofans (GTFs) – these can generate further savings in fuel consumption of ca. 15 percent per engine. The first hydrogen test aircraft will not be taking off for another 10 to 15 years at the earliest – and they will then need a further 15 years before they are market-ready. Battery-operated flights on short-haul routes will be possible sooner than this.

According to the statistics, the volume of air traffic doubles every 15 years. Where do you think the relevant areas for action will be if we are to make aviation climate-neutral?

Today, perhaps five percent of people use their privilege to fly. With the growth of the world's population and aspiring economic powers such as China, the aviation market is expanding by around four percent every year. We have now arrived at a point where aircraft for 50+ passengers are actually all configured in the same way: fuselage, wings, tail unit, two to four engines. With the Airbus blended wing body, the characteristics of a conventional "tube with wings" design are combined with those of the flying wing. This creates a lot of volume for the H₂ tank in the wings and means less friction loss and more lift.

I think it won't be long before the first hybrid concepts are being promoted. These solve the problem of needing to provide a lot of energy for take-off or for other high-performance manoeuvres – and yet fly in a resource-friendly way in cruise mode. In my opinion, air traffic control and the efficient automation of flight routes using data on weather or traffic volume are important areas of activity. Ultimately, however, mobility on the ground will also have an important role to play – electric vehicles to move the aircraft around on the ground or better local transport connections via rail.

More than 90 percent of the emissions created by airlines come from burning kerosene. Sustainable aviation fuels (SAFs) could already be in use today, but they are significantly more expensive than traditional kerosene. How could the price level be evened out?

The way I see it, there are still efficiency questions to be answered with SAFs. It takes a lot of energy to filter the required substances from the air and to eventually obtain sustainable kerosene and, at the end of the day, the exhaust fumes that are produced also pollute the atmosphere. They remain there for longer than they would on the ground, where they can be filtered much faster. I think we are all facing a challenge. Whether it's passengers, airlines, OEMs, research institutes or policymakers. The important thing is that we try out ten different routes, even if eight of them lead to dead-ends and two to a new fork in the road – that's how evolution works. It's important that we, as industrial nations, become role models so that emerging countries such as China or India recognise the added value of being able to breathe cleaner air.

Long-haul battery-powered electric aircraft are still seen as "Mission Impossible" – are there any impulses for e-flying that could come from the automotive sector?

Electricity itself doesn't weigh anything. However, the storage unit, the batteries, are still too heavy for aviation. Currently, one kilogramme of kerosene would be replaced by approximately 52 kilogrammes of battery. If my flight from Hamburg to Munich requires two and a half to three tonnes of kerosene, the equivalent would be at least 130 tonnes of battery – unthinkable. On the other hand, the greatest cost factor for today's airlines is the servicing and maintenance of turbine engines. By comparison, the costs of maintaining electric engines are extremely low. The automotive sector will optimise the energy density of their batteries and this will mean that ranges can be extended. Further impulses come from rapid charging and from power management. This could be especially relevant in the cabin.

Flying with hydrogen? Many people will think back to the "Hindenburg", the famous hydrogen airship launched in May 1937 that went up in flames and was destroyed in less than a minute. In your opinion, is safety the biggest challenge when it comes to hydrogen-powered aircraft?

Let's think about the expansion of air in a balloon. Hydrogen can only be stored in cylinder-like containers, at high pressures and low temperature. The energy density of hydrogen per unit mass is three times higher than that of kerosene and four times lower per unit volume. This makes it possible to realise two concepts: that of the fuel cell with high efficiency, as used in the hydrogen aircraft Hy4 developed by the German Aerospace Centre, for example, and also the hydrogen turbine where hydrogen serves as a replacement for kerosene. In the Airbus ZEROe concept aircraft, a good deal of passenger space will have to make way for these tanks. I believe that we will quickly be able to master any safety issues. I see greater challenges in obtaining, transporting and delivering green hydrogen on a large scale.

The 2050 aircraft is coming into land in Munich. What is your vision for sustainable air traffic on the ground?

I think we will fly much more from point to point and no longer from hub to hub – smaller airports will become more important. Today, we are already seeing higher utilisation of small long-haul aircraft, whether this is a good thing in either economic or environmental terms is debatable.

Let's assume instead that my journey to Munich will take place a couple of years later. Perhaps then our aircraft passenger cell will be more like a container that is released on the ground – and then quickly exchanged for one that is ready to set off again. Things will flow to a greater extent, especially in local traffic. And 50 years further into the future, it is possible that the aircraft will be hanging from inductive charging networks in the sky. That's something the Wright Brothers would have loved.