Engines (including BLI19, Hybrid Electric, Increased Efficiency of Gas Turbines).

Important guidance is provided in the latest revision document ARP 475 (Guidelines for Development of Civil Aircraft and Systems) and ARP 476124 (Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment). 

The recently launched CLEEN Phase-III focus areas include fuel burn reduction via fan module technology, combustor and HPT technology, open fan technology, and highly integrated hybrid-electric systems (see Figure 5).

Another focus area is SAF development – both qualification/ASTM standards maturation and increasing blend ratios to up to 100%. Europe’s Clean Sky 2 joint technology initiative aims to develop and demonstrate breakthrough technologies for civil aircraft that could reduce C02 emissions by 20%  (2025) to 30% (2035). Focus areas have included contra rotative open rotor (CROR) demonstration, design/test of a turbofan LP spool and nacelle technologies demonstrator, and testing of very high bypass geared engine technology for widebody aircraft (Figure 6).

 The new Clean Aviation2 framework will further mature key engine concepts linked to three main pillars. The first pillar is focused on ultra-efficient aircraft and concepts such as truss-braced wings, boundary layer ingestionand the open fan engine. The second pillar is dedicated 21 BLI, Boundary Layer Ingestion, ro electric and hybrid-electric engines covering a wide range of power and energy levels. The third pillar addresses hydrogen powered aircraft with a focus on compatibility of engines and fuel systems (Figure 7).

 Finally, the EU Horizon 2020 program is funding disruptive concept studies such as ULTIMATE (propulsion conceptsincluding topping/combined/recuperative cycles), IMOTHEP (distributed electric propulsion), and ENABLEH2 (addressing H2 challenges such as combustion & fuel system design).