Building a sustainable and climate neutral future for aviation is an inevitable requirement for a society with increasing mobility needs. If we are to stabilise the global temperature below the 1.5°C threshold set by the Paris Agreement, rapid action is to be taken. MINIMAL will contribute to a radical transformation in air transport by providing disruptive ultra-efficient and low-emission technologies that will, in combination with the aviation ecosystem, sustainably reduce the climate impact of aviation. The MINIMAL project will, through an unprecedented effort between European engine OEMs, world leading atmospheric physics scientists, and lead researchers in combustion and propulsion, attack the major sources of non-CO2 and CO2 emissions in aeroengines. This will be accomplished with the introduction of climate optimised new propulsion systems based on composite cycle engine technology, that provides unparalleled flexibility with respect to operations, and that has the potential to eliminate the large sources of effective radiative forcing by 2035: 80% reduction from contrails, 52% reduction from net-NOx, and 36% fuel burn reduction resulting in 36% to 100% CO2 reduction, depending on the fuel used. Results will allow assessing the interdependencies between non-CO2 and CO2 effects already during the early stages of aero-thermal-mechanical design and converge into engine options that have minimum climate impact. The findings are supported by numerical (TRL 2) and experimental (TRL 3) proof of concept of Low-NOx opposed-piston constant volume combustion technology with pre-micromixing of hydrogen. In MINIMAL we understand the urgency and aim for maximum impact. Aggressive, but realistic roadmaps will be outlined together with regular exchanges in major industry research centres to develop these technologies into products and bring them to in 2035-2040.

HEROPS aims to introduce climate-neutral propulsion into regional aircraft by developing MTU’s Flying Fuel Cell (FFC) propulsion system concept for entry into service in 2035. This disruptive hydrogen-electric propulsion system uses fuel cells as sole power source and a liquid hydrogen fuel system, without the need for high-power batteries. Integration of both the fuel cell system and the electric propulsion unit into a compact engine nacelle will ensure an efficient system at high power-to-weight ratio. HEROPS targets to demonstrate a 1,2 MW propulsion system based on a scalable 600 kW core module at TRL4. The core module and all further sub-systems will be validated up to TRL5. Complemented by simulation and electrical network testing of the overall modularised system, scalability to the 2 – 4 MW power level will be confirmed. The certification programme will build upon on-going certification activities, enabling timely maturation of the aviation-native HEROPS technology against relevant certification requirements. The two-phase approach of the overall programme - including extensive development, test and validation cycles at each stage - is expected to advance the FFC concept to TRL6 for integration and demonstration on a regional aircraft by 2028. It will pave the way for commercial prototyping and entry-into-service by 2035, delivering a key propulsion technology to reach the European Green Deal’s objective of climate-neutral aviation by 2050 with 100% prevention of CO2 and NOx emissions and up to 80% reduction of the climate impact from contrails and contrail cirrus. The HEROPS project will meet this challenge with a European consortium of aircraft propulsion system integrators, electrical system experts, key tier 1 suppliers and leading researchers in stack technology, mechanics and propulsion, leveraging relevant and effective synergies between European and national programmes.

With the ULTIMATE project five experienced research groups and four major European engine manufacturers will develop innovative propulsion systems to fulfill the SRIA 2050 key challenges. One of the most challenging targets is the 75% reduction in energy consumption and CO2-emissions. Technologies currently at TRL 3-5, cannot achieve this aim. It is estimated that around a 30% reduction must come from radical innovations now being at lower TRL. Thus, European industry needs synergetic breakthrough technologies for every part of the air transport system, including the airframe, propulsion and power. The ULTIMATE project singles out the major loss sources in a state of the art turbofan (combustor irreversibility, core exhaust heat, bypass exhaust kinetic energy). These are then used to categorize breakthrough technologies (e.g. piston topping, intercooling & exhaust heat exchangers, and advanced propulsor & integration concepts). This classification approach gives a structured way to combine and explore synergies between the technologies in the search for ultralow CO2, NOx and noise emissions. The most promising combinations of radical technologies will then be developed for a short range European and a long range intercontinental advanced tube and wing aircraft. Through the EU projects VITAL, NEWAC, DREAM, LEMCOTEC, E-BREAK and ENOVAL, the ULTIMATE partners have gained the most comprehensive experience in Europe on conception and evaluation of advanced aero engine architectures. Existing tools, knowledge and models will be used to perform optimization and evaluation against the SRIA targets to mature the technologies to TRL 2. Road maps will be set up to outline the steps to develop the technologies into products and bring them onto the market. These road maps will also provide a way forward for future European propulsion and aviation research.

The SWITCH project is an ambitious initiative aimed at addressing the challenge of achieving climate-neutral short- to medium-range air transport by developing a revolutionary sustainable gas turbine propulsion system. This project is tightly aligned with the strategic goals of the Clean Aviation program, which seeks to foster innovation and sustainability in the aviation sector. The primary objectives of the SWITCH project are improving fuel burn and energy consumption by 20% and achieving a 50% reduction in the climate impact of both NOx emissions and contrails, compared to a state-of-the-art engine, hereby significantly reducing the three major warming effects of aviation on the climate — CO2, NOx, and contrails. This 20% reduction in fuel burn meets the foreseen contribution from propulsion system side to the -30% goal on aircraft level as laid out in the Clean Aviation Strategic Research and Innovation Agenda (SRIA). To achieve these objectives, the project develops the Dual-spool-hybridized heat recovering Second-Gen Geared Turbofan, which features a dual-spool hybrid-electric architecture, combining two Collins Aerospace megawatt-class electric motor generators within a Pratt & Whitney GTF™ engine, introduces Waste Heat Recovery to further improve thermal efficiency beyond the 2nd Gen GTF, and a low-emissions combustor to reduce NOx and nvPM emissions. The development of lightweight multifunctional structures and an optimized nacelle and thrust reverser support the integration of novel technologies into the powerplant. Local air quality and noise levels around airports are improved through electric taxiing. The propulsion system will be compatible with 100% drop-in Sustainable Aviation Fuel (SAF) and its principle is suitable for powerplants that burn hydrogen. It addresses all climate-relevant market segments: short-, medium-, and long-range. The SWITCH project is conducted by a global consortium, involving aircraft, engine and system OEMs, key tier I suppliers and leading research institutes in combustion and propulsion. This unprecedented collaborative effort will leverage synergies between European and national programs, ensuring that the project is well-placed within the context of the Clean Aviation initiative. In 2026, SWITCH matures the dual-spool hybridized turbofan to Technology Readiness Level (TRL) 5 through ground demonstration of the full propulsion system, and the waste heat recovery concept to TRL 4 through validation of its key enabling technologies. In Phase 2 of Clean Aviation, the dual-spool hybrid-electric configuration is flight tested and matured to TRL 6 by 2030, and Waste Heat Recovery System demonstrated to achieve TRL 5 by 2030. Results from SWITCH will reinforce confidence in the climate reduction potential of the Dual-Spool- Hybridized heat recovering Second-Gen Geared Turbofan and form the technological foundation to enable the innovation to enter the market by 2035. This concept will significantly reduce aviation's climate impact, contributing towards the European Green Deal's goal of climate neutrality by 2050. Overall, the SWITCH project is ready to make a substantial contribution to sustainable aviation, driving innovation, and reducing the environmental impact of air travel.