Electric Aircraft Propulsion and How it Works

There’s more than one way to propel an airplane.

While it’s true that most aircraft engines today run on fossil fuels like Jet A, Jet B, Avgas or diesel, many readers may be shocked (pun intended) to learn that electric technology will change the way we think about aircraft propulsion – and sooner rather than later.

In fact, around 215 types of electric-powered aircraft are currently being developed worldwide, and industry observers say electric airplanes will be commonplace before the end of the next decade.

Unmanned Aerial Systems (UAS), Urban Air Mobility (UAM) platforms, other small passenger and cargo aircraft and – eventually – larger commercial passenger planes are all good candidates for electric and hybrid-electric propulsion architectures. But no matter what form these new aircraft take, they will be more efficient, quieter, safer and much greener than aircraft relying only on traditional internal combustion engines.

At Honeywell, we’re applying our unique expertise from across our Engines and Power Systems portfolio and working with DENSO, a world leader in electric motors and controllers for the automotive industry, to transform aircraft propulsion as we know it. Together, we aim to deliver innovative and integrated solutions to current (retrofit) and future (clean-sheet) customers in the rapidly-growing electric aircraft space.

The logical path toward electric propulsion

Two key technologies for the future of flight have a long history. Electric motors were invented in the 1830s, and battery-powered cars were first manufactured in the 1890s. Their descendants are found across various industries today, including in modern airplanes that already rely on electricity to power avionics, fly-by-wire, actuation and other systems, and perform tasks once done by mechanical equipment.

Onboard electric power is generated by the main engines and super-efficient auxiliary power units, which Honeywell pioneered over 50 years ago. All this sets the stage for electric propulsion, which is the next step in the evolution toward electric aircraft.  

When we talk about electric propulsion, we’re talking about a range of propulsion architectures designed to meet the needs of specific aircraft that are using electrically driven motors to provide thrust. There is no “one-size-fits-all” or “best” solution without understanding the key customer requirements and mission profile of an aircraft.

Honeywell has studied several different propulsion architectures – ranging from the legacy engines on most aircraft today to all-electric, battery-based solutions. There are various hybrid architectures across that continuum – including Turboelectric, Partial Turboelectric, Series Hybrid, Parallel Hybrid and Series-Parallel Hybrid. All of these deploy electric motors in various ways as part of the overall propulsion system.

Each architecture has its own strengths and characteristics, so Honeywell also developed a sophisticated software tool that can analyze tradeoffs between weight, range, altitude, speed, and different battery chemistries to help aircraft manufacturers pick the optimal solution to meet their particular requirements.

How electric propulsion works

In contrast to propulsion systems built solely around an internal combustion engine, all-electric and hybrid-electric architectures utilize an electric motor. The motor can be the sole source of thrust or it can be used in combination with a conventional engine, by either providing another source of thrust or even a boost of power to the propulsion system during key stages of flight.

In addition to the motor, a fully-integrated electric propulsion system includes other critical components like motor controller hardware and software, gearboxes and cooling systems. This integrated system is known as an electric propulsion unit (EPU), and Honeywell and DENSO are developing state-of-the-art solutions to meet today’s and tomorrow’s needs.

While battery technology matures, hybrid-electric aircraft will need both batteries and other power sources – like ultraefficient generators or fuel cells – to power the aircraft, recharge the batteries and improve aircraft safety, efficiency and range. 

Power generation and conversion are core strengths for Honeywell, and our innovative engineering teams have made enormous advances in generators in recent years. For example, we are developing a one-megawatt turbogenerator that can run on biofuel to reduce carbon emissions even further. Additionally, Honeywell’s recent acquisition of Ballard Unmanned Systems places us squarely in the middle of another important means of providing power: hydrogen fuel cells, which are already being used to generate power for smaller Class I and Class II UAS platforms.

What’s behind the Honeywell-DENSO partnership?

Electric propulsion will quickly mature to meet the needs of the emerging UAS/UAM segment, which will permanently change the way we travel across town, transport goods to remote locations and perform many important tasks done today with airplanes, helicopters and ground vehicles. Thousands, and eventually millions, of small, highly-capable aircraft will become part of the global aviation infrastructure.

There is important work to be done to ensure quality and certification to aviation standards, which are very familiar to Honeywell and other experienced aviation companies. But many other challenges in meeting these new customers’ needs are more germane to the automotive industry.  Our partner DENSO has the proven ability to mass-produce complex systems – like EPUs – at scale, while maintaining the highest standards of quality and reliability.

That’s why Honeywell and DENSO decided to form an alliance, to combine the respective strengths of two leaders, to create best-in-class electric propulsion units.

The Honeywell/DENSO team is already working on some very exciting development programs, and we’re always looking for new opportunities.