Honeywell’s New Opening Space in Electric Propulsion

An interview with Honeywell

The transition of energy from one to another makes for some of the most watershed moments in human history. From steamed-powered trains to high-speed railways, the power for land transportation has evolved from boiling water to a greener alternative: electricity. It was not until 100 years later that the first airplane was invented, but the shift of energy up above the sky has only just begun.

Honeywell Aerospace is one of the key players spearheading the transition. The U.S. based aviation company is developing the world’s first generation of electric vertical take-off and landing (eVTOL) aircraft motors. Once its vision of electric air taxis flying around the city becomes a reality, the electric propulsion technology for urban air mobility (UAM) or advanced air mobility (AAM) will transform the way we think of aviation, once again rewriting the history of human transportation.

The Democratization of Aviation

Anticipating the tremendous opportunities behind this “new opening space” for aviation, Honeywell Aerospace embarked on its UAM journey three years ago. As an already established engine manufacturer in the aviation industry, Honeywell envisions electric motors as a new way to reshape people’s everyday lives.

Unlike helicopters or fixed-wing aircraft, eVTOLs will be closely connected to urban areas in some of the world’s highly-populated cities and are designed to be accessible to a wider community while introducing a more efficient and sustainable means of travel.

This is kind of a new opening space for aviation, a new way to democratize aviation, to make it pervasive and a different way to enter all of our lives.”

It’s a great sandbox for building technologies like electric propulsion,” said Xu Jia, Chief Technology Officer, Honeywell UAM and UAS, in an interview with Asian Sky Group, adding that Honeywell envisions a future of air taxis carrying people around the city and making a 100mile commute in under 45 minutes.

To unleash the economic and connectivity potential of advanced aerial mobility, Honeywell has a product line of electric motors as well as avionics and fly-by-wire systems. With both being an indispensable part for the integration of the operation system, electric propulsion is key to air taxis taking flight and an integral part of the whole new concept of eVTOLs.

“Without distributed electric propulsion, eVTOLs wouldn’t really exist as a concept. It’s really at this technology inflection and the potential market demand that drove the development of this key technology,” Xu said.

However, achieving the monumental technological breakthrough during the new journey calls for more than one player. Honeywell is working closely with companies including Lilium, DENSO, Archer and Supernal in developing electric motors and achieving specific goals like safety and noise, as well as optimizing the entire propulsion system.

Honeywell formed a joint research program with vehicle engine manufacturer DENSO in 2019 and signed an alliance agreement to develop an electric propulsion system for eVTOLs in 2021. The engineers are working together on a daily basis to develop e-motors for the Lilium Jet.

To meet the requirements of each OEM, Xu said cooperation is always about communication and tradeoffs and finding the right optimization between the aircraft and the motor systems. For example, the unique configuration of the Lilium Jet needs as many as 36 small motors to achieve the aerodynamic performance required. While for more conventional lift plus crews and tilting rotor configurations, architects are working on bigger motors.

Every Pound Matters: The Snowball Effect

While working with the right partner helps, Honeywell’s most important task is to generate enough electric power to lift an aircraft vertically in a safe, efficient, and coherent manner.

“It’s one thing to build an electric motor for small drones or drone application, but when you want to build safe and certifiable electric motors at the scale that’s needed to enable human or even cargo transportation over populated area, you very quickly get into some complex engineering problems and certification problems,” Xu explained.

“One of the key challenges of vertical takeoff aircraft is we have very limited control authority at low speed right at high speed. The air is washing over the aircraft. We have a lot of energy in the air that we can play with to maneuver the aircraft at high speed, but at low speed when you’re taking off, that’s been really challenging,” Xu added, saying that Honeywell is building electric motors that have a smart level of redundancy on both the power electronic side, the control side as well as the active component of electric machines.

For Honeywell, the “secret sauce” for building electric motors to achieve a high level of reliability is to ensure that the propulsion system still recovers and completes the flight if one of the motors fail. To achieve the safety and reliability goal, the architects divide the motor into numerous units that operate separately with the same amount of power. That said, the design has to be simple and light weight.

The weight of eVTOLs is a fundamental factor to consider during aircraft construction, as it directly impacts the cost, with heavier models being more expensive. Studies show that each pound of empty weight costs around US$700 for aircraft acquisition. From the aircraft building side, even a slight change in weight can have a cascading effect, altering every aspect of aircraft design.

“We understand the trade offs thatequip the tail with aircraft level, you know every pound that we put on an airplane in the form of a system, we have to build five more pounds of the aircraft right for these EV total platforms just because you put on this motor, the motor gets a little bit bigger. Now the whole aircraft gets a little bit bigger because we need more batteries to fly the same mission. The wing has to get bigger because we now have to sustain that flight, that cruise phase as well,” Xu said.

Beyond the technological challenges, the successful take-off of air taxis needs a high level of integration in the development stage.

The critical role of Honeywell being a system integrator is to preintegrate every aspect of the system to optimize the performance, weight, and power consumption before an eVTOL gets ready for the unprecedented task of mass production and commercialization. “When you look at aerospace, that’s something that we haven’t really been doing historically,” Xu commented, emphasizing that building the complex electric aircraft system must go beyond individual companies.

“Successful is to have suppliers and integrators like Honeywell that will take some of that burden off of the system development and integration and bringing established expertise and experience in building an integrated certified systems into the space.”

Engaging the Industry

As the advancement of technologies outstrip the pace of the development of regulatory guidance, the challenge that comes along next is certification. The process takes several years to complete due to the complex and extensive testing and validation required.

To navigate this complex issue, Honeywell recently launched the industry’s first certification reference guide. The document summarizing Federal Aviation Administration (FAA) and European Union Aviation Safety Agency (EASA) rules across multiple AAM segments is constantly updated and shared among the industry.

“So there’s been a lot of progress and what we’ve noticed is that to elevate the level of discussion in the industry about certification and the pathway to get there, as well as the gaps that still in the regulatory system. We’ve decided to write all of this down and produce this handy one pager guide to where certification is for different segments of that advanced aerial mobility,” said Xu.

Reaffirming the progress that has been made among AAM companies and regulatory bodies in the U.S. and Europe, Xu hopes to engage the industry in a dialogue through the reference guide. By working closely with other companies, Honeywell is positive about introducing a whole new aircraft category, which will not only transform the way people travel but also other segments of aviation.

“It’s going to change profoundly how we design other kind of aircraft.” Xu added. “I think that’s incredibly exciting in terms of reducing fuel burn and increasing the sustainability of the aircraft, because suddenly as a designer, you have all of these new options to put power and control anywhere on the aircraft that you think is important to have. So, it’s going to open up totally new kinds of aircraft configurations and that’s incredibly exciting.”