It is a well known fact that we can expect air traffic to grow rapidly over the coming years—though the sector disagrees slightly on exactly what that yearly growth will be. At this year’s International Air­show in Farnborough in the UK, for instance, Airbus and Boeing were talking about a global growth rate of 4.5 percent per year up to 2035, while the Inter­national Air Transport Asso­ciation (IATA) puts the increase at a some­what more modest 3.8 percent per year. Still, we are long past quibbling about how large exactly the increase in air traffic will be—today, the important questions are where that growth will take place, what impact it will have and how we can keep pace with the soaring demand for mobility.

According to the current forecasts of the United Nations, the bulk of global population growth—and thus potential passenger increases—will take place in cities. Back in 1950, just 30 percent of the popu­la­tion lived in urban areas, a figure that now surpasses 50 percent and which experts expect to exceed two thirds of the population after 2050. While ur­bani­za­tion has reached an ad­vanced stage in the countries of the West, it is just taking off in Asia, Latin America and Africa. In China and India in particular, cities have boomed, bringing with them an af­flu­ent and consumer-oriented middle class. As income in­creases, these people can afford to fly more. If popu­lation growth remains on or near its current course until 2050, we must be prepared for a three- to fourfold increase in air traffic.

Infrastructure on the ground

“The question is how infra­struc­ture can keep pace with mobility needs in such rapidly expanding cities,” says Kay Plötner from the Bauhaus Luftfahrt think tank in Munich. The aero­space engineer is one of those involved in a concept that could provide an elegant solution to the problem: new, smaller-sized air­ports located directly in city centers and offering direct links to each other and other already existing air­ports. Plötner and his col­leagues have called the study, which they presented at the 2016 Berlin Airshow, “CentAirStation.”

The idea is to build four-storey buildings over existing under­ground and municipal rail­way lines, providing a place for air­craft to take off and land. You could think of it as a sort of air­craft carrier, just on land, says Plötner. The flight deck is 650 meters long and 90 meters wide, while the floor below is used for board­ing and clearance. One floor below that, there is security and luggage drop-off as well as restau­rants and shops acces­sible from the trains arriving at ground level. “Our vision is that passen­gers should be able to take off no more than 15 minutes after arriving on the train, and be able to exit the building within 10 minutes of landing,” says Bauhaus researcher Plötner.

It should be noted that the CentAirStations are de­signed to work only with a new type of aircraft, the “CityBird.” Plötner explains that this would be a short-haul air­craft with around 60 seats and a range of 2,700 kilo­meters. Engines with a high bypass ratio are to combine modern turbo com­po­nents with piston tech­nol­ogy, allowing for par­ticu­larly low NOx emissions. MTU Aero Engines is one of those who has worked on the pio­neer­ing composite cycle engine concept. In addition, a catapult launch is to boost the drive power needed for take­off, making operations even quieter. However, the CityBird is also designed to be able to land and take off from traditional airports—ultimately, the idea is to com­ple­ment existing air­ports, not replace them, says Plötner.

Four hours door to door

Bauhaus’s idea could play an important role in ful­fill­ing one of the European Commission’s ambitious targets for “Flightpath 2050”: that, by mid-century, 90 per­cent of all journeys in Europe should take no longer than four hours door to door. Florian Rudolph, a researcher at the German Aero­space Center DLR’s Institute of Air Transport and Air­port Research, il­lus­trates just how dif­fi­cult that is in today’s world: “If I want to fly from Braun­schweig to Paris via Hannover and be sure of catching my flight, I have to factor in a buffer for any bus and train delays and set off from home three hours before my flight,” says Rudolph. When you add in the flight time, the four-hour target is long surpassed.

In the DLR Optimode research project, Rudolph and his col­leagues have examined how buses, trains and air­lines can be better co­or­di­nated so that travelers can be sure of catching their flights without having to plan in buffer time. “If air­lines, bus and train com­pa­nies know that air passen­gers are sitting in a bus or train on their way to the air­port, they can calculate al­ter­na­tive routes, put on extra con­nec­tions or ar­range speedy boarding in the event of any delay,” says Rudolph. “Passengers would be kept informed about these de­vel­op­ments via a live app. Should the delay prove too great, the system would cal­cu­late a new connec­tion and get the passen­ger to their desti­nation by another route,” says Rudolph.

It all sounds quite simple, but it is a real chal­lenge in practice. Cur­rent­ly, air­lines only know for sure that a passen­ger is actually going to fly when they board on the day of their flight. So that trans­por­tation ope­ra­tors can react flexibly, trav­el­ers would have to be pre­pared to share details about their lo­ca­tion with bus and train companies as well as with the air­line. The experts at the DLR envisage that this will happen auto­matically, for instance by scanning a bus or train ticket and comparing it against GPS co­or­di­nates relayed by a smart­phone. When the passen­ger enters the air­port, they con­firm that they have arrived with a barcode scan. Still, even though the first Opti­mode proto­type has received exceed­ingly positive feed­back, the re­search­ers are clear that their project is a venture into the unknown. “Until now, individual operators have focused on op­ti­mizing their own systems,” says Rudolph. “The challenge now is to convince them to move away from their indi­vidual priorities for the benefit of trans­por­tation as a whole.”

Big data is transforming aviation

What Optimode has already shown is that raw data will have just as big an impact on aviation as urbani­zation. Airlines will be able to make use of pas­sen­ger infor­mation to optimize the service they provide, offering a pas­sen­ger’s favorite hotel with their flight booking, for instance, or directly noting in-flight food preferences. Not only that, but check-in will be a much smoother process as well: suitcases marked with radio chips will be able to be deposited well before the airport—automatically locating the relevant pas­sen­ger later on in the journey. Industry experts anticipate that waiting at baggage reclaim will be the exception rather than the rule within the next de­cade.

“The digital transformation presents aviation with enormous op­por­tu­nities. It makes flying safer, more comfort­able and more efficient, as well as making the manu­facture of air­craft and air­craft components cheaper and more flexible,” says Bernhard Rohleder, CEO of Germany’s digital asso­ciation Bitkom. Dr. Friedhelm Kappei, Senior Manager Central and Per­for­mance Engineering at MTU Main­tenance Hannover, knows the potential of big data analysis first hand through the MTU ^Plus Engine Trend Monitoring software, which monitors engine para­meters such as engine speed, tem­pera­ture and pressure both at take­off and during flight. When the aircraft lands, these data are relayed to MTU.

Work on the Engine Trend Monitoring solution began around 15 years ago, and as much as 30 years ago in the case of the geared turbofan tech­nol­ogy that is just now going into regular service in the latest gen­era­tion of engines, says MTU market expert Dr. Marc Le Dilosquer. “It goes to show that we have to start work on changes in the aviation sector today in order to be able to reap the fruit in the future.” He does not antici­pate a revolution of air travel given the current situa­tion, but rather a steady evolution. This is in part due to the fact that the expensive infra­struc­ture is largely in place and must continue to be used where possible. As to whether it makes sense to expand an existing air­port, this can now be evaluated using an adapted piece of DLR software that was originally used to predict the develop­ment of stars’ luminosity.

More flying, less noise

All those involved know that changes in aviation can be imple­mented only with the accept­ance of the public. “Above all, it’s a case of making air­craft so quiet that they make no or minimal dis­turb­ance,” says Roland Gerhards, CEO at the ZAL Center of Applied Aero­nautical Research in Hamburg. While electric flying has the potential to reduce noise in the long term, fuel cells and small electric motors in the landing gear are prime candidates for sig­nifi­cant­ly reducing noise in the short term, says Gerhards. “This would allow air­craft to coast their way silently to takeoff.” Both topics are cur­rent­ly being re­searched at the ZAL and could be ready for im­ple­men­ta­tion within the next five to ten years.

Noise reduction also is an issue for aero engine manu­facturers: The new generation of geared turbofan engines not only reduce fuel consumption and harmful emissions, but also reduce the noise foot­print by up to 75 percent. This cuts the noise levels around an air­port to a quarter of their pre­sent levels. As a result, it is possible to operate more air­craft without creating too much noise in the sur­round­ing area, opening up room for future growth.