Nachhaltigkeit - Sustainability in Aerospace

10 November 2026, Andreas Strohmayer

Alternative Technical Concepts

• ACARE’s “Fly the Green Deal” set highly ambitious goals for emissions of CO2, NOx and noise
• “Radical technologies” in aircraft design and sustainable fuels aim for:
  • increased overall efficiency
  • no / less in-flight emissions
  • less community noise
  • viable operating cost and increased reliability

Aviation emissions about 1/3 "$CO_2$ effects", 2/3 "Non $CO_2$ effects"

How to Change

The issue with full electric flight: Needed power for regional single-aisle aircraft is about 20MW, way more than any currently flying electric aircraft

A lot of energy is needed even for single aisle commuter aircraft (more than 10000 kWh), while todays batteries have very low volumetric and gravimetric energy density compared to Jet A-1 fuel - Focus shift on hybrid-electric propulsion

Hybrid Electric

Propeller is most efficient while rotating as slowly as possible and being as big as possible A broad range of possible architectures:

• all-electric architecture
  • battery poweres motor, very simple
• serial architecture
  • fuel is used to power generator to generate electrical power
  • battery is used as well (serial) and can be used on its own or alongside generator (e.g. during take-off)
• parallel architecture
  • electric motor powered by battery poweres / supports combustion engine on same shaft
• turbo-electric architecture
  • no battery is used, only fuel is burned to run generator to run electric motor
  • can be used for hybrid approaches with very low hybridization degree (~3%) to vastly extend range by having the propeller in the back (electric motor is way smaller and lighter) or distributing many propellers over the wingspan

Synergies are key to viable hybrid-electric flight

also another problem: cooling fuel cells, which are not in the open air stream, like traditional engines

Aircraft design parameters affecting the figures of merit

• aircraft geometry
  • configuration
  • dimensions
  • masses
• hybrid-electric erchitecture
  • hybridization factor
  • selection of technologies
• energy management strategy
  • operation in different flight segments (all-electric take-off and landing, gas turbine optimized for cruise, electric boost for take-off, ...)