Claire technology agenda

MTU’s technology agenda is called Clean Air Engine (Claire). In it, we lay out potential solutions and concepts for sustainable commercial engines to pave the way for emissions-free flight. All efforts are aimed at reducing climate impact—that is, CO₂ and NO_x emissions and contrail formation. Reducing energy consumption is also a crucial outcome.

Key elements are evolutionary enhancements of the gas turbine engine based on the geared turbofan (GTF), and completely new, revolutionary propulsion concepts, such as the Revolutionary Turbofan and the Flying Fuel Cell^TM. Sustainable aviation fuels (SAFs) and hydrogen play an important role.

There are three stages on the journey to emissions-free flight: The first stage is marked by the geared turbofan, which has been a standard component since 2016. In conjunction with SAFs, it can already significantly reduce climate impact today. In the second stage, MTU aims to realize not only the next generation of the GTF but also the Revolutionary Turbofan for all thrust classes and the Flying Fuel Cell for short-haul regional routes—all by 2040. A state-of-the-art turbofan powered by hydrogen is also possible. Stage three will begin in 2050 and is aimed at further improving the efficiency of all propulsion technologies and introducing the fuel cell on short- and medium-haul routes.

Geared turbofan

The first Claire stage was achieved with the highly efficient engines of the Pratt & Whitney GTF^TM engine family. MTU contributes key technologies to these engines. They are used in modern narrowbody aircraft and reduce fuel consumption and CO₂ emissions by 20 percent each per trip compared with their predecessors.

Work has as well already started on the second generation of geared turbofan engines, which boast additional improvements. When powered by SAF or liquid hydrogen, next generation turbofans could reduce the climate impact of aircraft by as much as 65 percent compared to a gas turbine from the year 2000.

Revolutionary Turbofan

The evolutionary enhancement of the gas turbine engine alone won’t be sufficient to realize the ambitious targets of the Paris Agreement. New revolutionary propulsion concepts are needed, and we’re working on that as well. Our main approach is the utilization of exhaust heat to improve overall efficiency.

Building on a Pratt & Whitney geared turbofan, the SWITCH consortium is combining the Revolutionary Turbofan concept with hybrid-electric propulsion elements for future engines. SWITCH is a research project funded by the EU’s Clean Aviation research program. The project partners include MTU, Pratt & Whitney, Collins Aerospace, GKN Aerospace, and Airbus, as well as other players in the aviation industry. MTU leads the consortium. These new technologies are also suitable for operation with SAF. The future use of hydrogen as an energy source is also being evaluated.

Flying Fuel Cell™

In another revolutionary propulsion concept, MTU is investigating options for a full electrification of the powertrain. This, too, forms part of the second stage of Claire and is scheduled for completion by 2035. We see the greatest potential in converting hydrogen into electricity with the help of a fuel cell. We call this concept the Flying Fuel Cell^TM, or FFC for short.

The FFC is set to be deployed initially on short-haul routes in regional air traffic. It can reduce climate impact by 95 percent, to virtually zero, which means it is nearly emissions-free: it emits only water. With improved efficiency, plans call for the FFC to be used in short- and medium-haul flights as well starting in 2050, further reducing the climate impact of commercial aviation.

Alternative fuels

A swift and significant reduction in climate impact can be achieved with sustainable aviation fuels, as they can be used immediately as drop-in fuels, i.e. without the need to adapt the aircraft or engine.

Known as SAF, these result in a largely closed CO₂ cycle. In the best-case scenario, the CO₂ released in flight is fully recaptured from the atmosphere for use in fuel production. SAF can also significantly reduce the formation of contrails.

In the long term, hydrogen will serve as the basis for climate-neutral propulsion of the future. We see three application possibilities: it can be burned directly in a gas turbine engine, converted into an SAF, or converted into electrical energy by means of a fuel cell.