An electric vertical take-off and landing aircraft, eVTOL, will make mobility in the skies more accessible for people.
Honda believes that it is the power unit that determines the range and how convenient eVTOL can be for people. Infusing its aero engine and F1™ power unit technologies, Honda is developing an innovative hybrid-electric propulsion system for eVTOL, to enable long distance inter-city flights. Honda eVTOL will provide a new value for mobility in the skies.
Making travel of 400 km (approx. 249 miles) or farther faster and more convenient -
Introducing challenges Honda is taking on to bring significant value to inter-city transportation.
Various companies, mainly startups, are currently developing eVTOL. Most of them are all-electric eVTOL, which fly only on battery power and are limited to short-distance flights with a range of about 100 kilometers (approx. 62 miles). However, market research has identified that eVTOL transportation in the biggest demand is for inter-city travel with a range of up to 400 kilometers (approx. 249 miles) or so. Today, and probably even 20 years from now, it will be difficult for aircraft to fly long-distance solely on batteries. Therefore, Honda decided to develop the Hybrid eVTOL that features a power unit utilizing a gas turbine generator and battery to realize the long range travel.
In general, aircrafts are more often used for travels of over 400 kilometers (approx. 249 miles). For example, in North America, for travel of up to 400 kilometers (approx. 249 miles), many people choose to drive their car, taking 3 to 4 hours to get to the destination. On the other hand, Hybrid eVTOL, like helicopters, can take-off and land as long as there is a certain amount of space, enabling passengers to get in and out of the eVTOL at a familiar location, such as the rooftop of a popular building, and eVTOL fly at a speed of more than twice as fast as a car. This enables passengers to travel 400 kilometers (approx. 249 miles) in only about 2 hours, providing significant value for people. Need for such convenient inter-city transportation exists not only in North America, but in other regions as well.
Another reason why we chose to develop Hybrid eVTOL is Honda's core technologies. The development of the innovative hybrid-electric propulsion system (“Gas Turbine Hybrid System”) was made possible by Honda’s original technologies amassed through a rivalry among Honda engineers with all kinds of expertise in various mobility-related technologies.
Honda began its research into aero engines in 1986, and in 2003, the HF118-2 aero engine developed independently by Honda was installed in the HondaJet experimental aircraft and successfully completed its first flight. Based on the HF118-2 technology, Honda began joint development of the HF120 engine with General Electric (GE), which received airworthiness certification from the U.S. Federal Aviation Administration (FAA) in 2013. The HF120 is now installed in HondaJet and flying around the world.
The aerodynamic, combustion and other technologies amassed through the development of aircraft engines are now being applied to engines for gas turbine generators.
Based on the HF118-2 developed by Honda, this compact turbofan engine was jointly developed by General Electric (GE) and Honda, and achieved the best-in-class fuel efficiency, environmental performance, and durability.
Honda has a proven track record of offering a number of hybrid vehicles to customers all around the world and also developing the ultimate hybrid power unit for F1™ racing. The motor, battery and energy management technologies Honda has amassed through hybrid system development are being optimized for our eVTOL, and the energy regeneration technology of the F1™ power unit is being leveraged for the ultra-high RPM gas turbine generator.
To obtain the type certification, precise quality control such as procedures related to design and analysis, procurement and manufacturing of materials and parts, assembly and delivery of power units, and traceability of parts and the demonstration of various certification criteria related to the system and the performance is required in every aspect. Honda has experience in obtaining certification for the HF120, an aero engine developed jointly with GE. This experience will be useful to conduct development and evaluation which take into account the precise standards for durability, performance, safety, functionality and reliability set by the authorities.
Combining a wide range of technologies, Honda develops a power unit only Honda can create.
Leading the way with experience and creativity.
Honda eVTOL will be equipped with a series hybrid system that generates lift and thrust by driving a motor that turns propellers (rotors) with electricity from a gas turbine generator and battery. During vertical take-off and landing, when high output is required, the electricity from the gas turbine generator and battery are combined to power the eVTOL. During cruising after reaching proper altitude, the eVTOL flies with motors while storing generated electricity in the battery. Honda is pursuing energy management suitable for an eVTOL, so that it can safely fly longer distances using less fuel.
Component structure of "Gas Turbine Hybrid System"
Honda utilizes aerodynamic and combustion technologies amassed through its long history of aero engine development to achieve lighter weight, more compact size and higher efficiency of its gas turbine engines, which are indispensable to achieve long-distance transportation.
Honda technologies for the MGU-H*, one of the components of F1™ power units, is being utilized to reduce the weight and increase the efficiency of the generator. The rpm of a reciprocating engine for hybrid vehicles is in the several thousands, whereas the rpm of a gas turbine generator for Honda eVTOL will be several tens of thousands, and the power density will also be more than 10 times higher than that of a mass-produced hybrid vehicle.
*MGU-H (Motor Generator Unit Heat): A regenerative system that converts engine exhaust gas into electrical energy.
For aircraft, weight is directly linked to performance, such as range. Therefore, we are striving to reduce the weight and size of the “Gas Turbine Hybrid System” and the airframe. The gas turbine generator is made compact through improvements to engine efficiency by applying aerodynamic and combustion technologies we have amassed over many years, and by adopting an integral structure which directly connects the gas turbine and generator without a reduction gear.
In addition, the battery has been made lighter by adopting cells that focus on the output side, which is an appropriate characteristics for a hybrid system, and also by increasing power density per unit weight. We also leveraged technologies for F1™ battery packs to achieve both high performance and weight reduction.
Reducing CO2 emissions has been a global challenge, even for the field of mobility in the skies.
Honda is reducing its environmental impact by electrifying its automobiles and other ground-based mobility products, and by applying hybrid technologies for aircraft, which is difficult to electrify completely. Moreover, Honda is researching sustainable aviation fuel (SAF) generated from atmospheric CO2 and hydrogen from renewable energy sources.
Honda eVTOL is designed to reduce fuel consumption by increasing the fuel efficiency of the gas turbine generator and through optimal energy management of the hybrid system. Ultimately, we are aiming to achieve carbon neutrality by using 100% SAF.
Moreover, if it contributes to carbon neutrality in the skies, we would like to consider expanding applications of our technologies to other aircraft in the future. Furthermore, from a broader perspective, our power unit technologies can create new value for mobility even beyond the skies. With this in mind, Honda will continue to refine our technologies.
■All measurements included in this story were measured internally by Honda.