Hybrid-electric propulsion combines fuel engines and electric systems to boost eVTOL range, efficiency, and sustainability—offering a practical path toward cleaner, smarter, and longer-endurance aviation.
The aviation world is in the middle of a green revolution 🌍. With mounting pressure to cut carbon emissions, engineers and researchers are reimagining how aircraft are powered. Fully electric planes are already flying short missions—but for larger aircraft and long-range eVTOLs, batteries alone just don’t have the energy density to compete with jet fuel.
That’s where hybrid-electric propulsion (HEP) comes in — the perfect blend of fuel energy 🔥 and electric control efficiency ⚙️. A new study from the Chinese Academy of Sciences, published in Aerospace (2025), offers a deep dive into how this technology is shaping the next era of flight 🚀.
Think of HEP as the “Prius of the sky” ✈️. Just like hybrid cars 🚘, hybrid aircraft use both a combustion engine (or fuel cell) and electric motors to share the work. The idea? Use fuel where it’s best (for high power or long range) and electricity where it’s most efficient (for low noise or quick bursts of thrust).
Hybrid systems come in three main flavors:
The engine doesn’t drive the propeller directly—it runs a generator that powers electric motors.
💡 Perfect for smooth control and distributed propulsion setups.
Both the engine and the motor can power the propeller together or separately.
💡 Ideal for flexibility—use electric power for takeoff, fuel for cruising.
A smart mix of both—switching between modes depending on flight phase.
💡 Best of both worlds: efficient climb, cruise, and descent.
Electric Vertical Takeoff and Landing (eVTOL) aircraft—those sleek flying taxis of tomorrow—are making waves in urban air mobility 🌆. Their runway-free design makes them perfect for city commutes. But battery limits mean they can only fly short distances before needing to recharge 🔋⏳.
The research points out that hybrid-electric eVTOLs solve this “range anxiety” issue. By combining batteries with fuel-based systems (like turbines or hydrogen fuel cells), these aircraft can:
Real-world examples are already flying:
Managing energy in hybrid aircraft is way more complex than in cars. Why? Because in aviation, every kilogram counts, and power demand changes drastically between flight phases—takeoff, climb, cruise, and descent.
The paper highlights the evolution of Energy Management Systems (EMS)—the brain of hybrid aircraft. Here’s how they’re advancing:
Together, these systems ensure that electric motors and engines cooperate intelligently, saving energy and keeping performance optimal across the mission.
Before anything flies, engineers rely on simulation and modeling to test hybrid propulsion. The study categorizes these models into:
Tools like NASA’s Numerical Propulsion System Simulation (NPSS) and Modelica-based frameworks are helping researchers create accurate digital twins for future hybrid aircraft.
Hybrid-electric flight is no longer just a lab dream. Aerospace leaders are investing heavily:
Meanwhile, Airbus, MTU Aero Engines, and Pratt & Whitney are collaborating under the EU’s Clean Aviation program to develop next-gen hybrid turbofan technologies, aiming for 25% CO₂ reduction by 2035 🌿.
One of the trickiest issues? Heat management 🔥. Hybrid systems combine electrical and thermal loads, demanding innovative cooling strategies. The paper emphasizes thermal-energy-coupled management, where the Energy Management Systems also monitors temperature across engines, motors, and batteries.
Moreover, hybrid systems must meet strict certification standards—airworthiness, redundancy, and fail-safety. The authors suggest a “certifiable EMS baseline” that balances performance with safety, integrating electro-thermal and health monitoring.
The study closes with a look into the future of hybrid-electric aviation:
Hybrid-electric propulsion is not just a bridge technology—it’s the foundation for a cleaner, more flexible air transport ecosystem 🌱. It brings together:
Together, they’ll enable long-endurance eVTOLs, regional hybrid aircraft, and even hydrogen-electric airliners in the next two decades.
The research provides a roadmap for engineers and policymakers alike—from simulation to certification—to make hybrid skies a reality 🌤️.
As this review makes clear, the future of flight isn’t purely electric or purely fuel-based—it’s hybrid. By merging the best of both worlds, engineers are unlocking the potential for sustainable, high-performance eVTOLs that can truly transform urban mobility and regional transport 🚁⚡.
So next time you imagine your city skyline filled with quiet flying taxis—remember: behind those smooth takeoffs and long-range flights lies a symphony of hybrid innovation 🎶✈️.
⚡ Hybrid-Electric Propulsion (HEP) - A power system that combines a traditional fuel engine (like a turbine) with electric motors and batteries to make aircraft more efficient and eco-friendly.
🚁 eVTOL (Electric Vertical Takeoff and Landing) - A type of aircraft that can take off and land vertically using electric or hybrid power — think flying taxi for cities of the future! 🏙️ - More about this concept in the article "Smarter Skies Ahead ✈️ How Bézier Curves Could End Airport Traffic Jams".
🔋 Battery Energy Storage System (BESS) - The onboard battery pack that stores electrical energy used to power electric motors during flight. - More about this concept in the article "Smarter Energy Management ⚡ for Modern Homes".
🔥 Gas Turbine / Turboshaft / Turbofan - Engines that burn fuel to spin turbines, producing thrust or electricity — often used in hybrid systems to keep the batteries charged.
💧 Fuel Cell - A device that converts hydrogen and oxygen into electricity — clean energy with water as the only emission! - More about this concept in the article "Smarter Microgrids, Cleaner Energy! 🔋 How Adaptive Droop Gains Help Microgrids Use More Solar and Less Fuel".
⚙️ Series Hybrid System - All power flows through the electric system — the engine drives a generator, which powers motors that move the propellers.
🔁 Parallel Hybrid System - The engine and electric motor work together, both capable of driving the propeller directly depending on flight needs.
🔄 Series–Parallel Hybrid System - A smart combo of both series and parallel designs — it switches modes between electric and fuel power for the best efficiency.
🧮 Energy Management System (EMS) - The “brain” of the hybrid aircraft — it decides how to split power between the fuel engine, batteries, and motors for maximum efficiency and safety.
🤖 Rule-Based Control - A simple EMS method using “if-this-then-that” rules, like “Use electric power during takeoff; switch to fuel in cruise.”
📈 Optimization-Based Control - Uses math and algorithms to find the most fuel-efficient power balance in real time.
🧠 Reinforcement Learning (RL) - An AI-based approach where the system learns from experience to make smarter power decisions during different flight conditions. - More about this concept in the article "Smarter, Stable Smart Grids ⚡ Hybrid AI".
🌡️ Thermal Management - Keeping all systems — especially batteries, motors, and engines — at safe temperatures to prevent overheating or energy loss.
🧩 Modeling and Simulation - Creating virtual versions of the aircraft and its systems to test performance, safety, and energy flow before building real prototypes.
🌍 Clean Aviation / Sustainable Flight - A global push toward low-emission air transport, using technologies like hybrid-electric propulsion and hydrogen fuel.
Source: Yu, F.; Chen, J.; Gao, P.; Kong, Y.; Sun, X.; Wang, J.; Chen, X. A Review of Hybrid-Electric Propulsion in Aviation: Modeling Methods, Energy Management Strategies, and Future Prospects. Aerospace 2025, 12, 895. https://doi.org/10.3390/aerospace12100895.
From: Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS); University of Chinese Academy of Sciences; Ningbo University.
