The Future of Advanced Air Mobility

H3X Aims To Deliver 2.8-MW Electric Drive To Convert Airliners

Technology start-up H3X is working to develop an integrated modular motor drive that it says will deliver the quantum leap in power density and fault tolerance needed to convert existing 50- to 100-seat aircraft to all-electric propulsion. It says it is in talks with aircraft manufacturers about possible applications for the 2.8-MW HPDM-3000 drive, which is expected to deliver a continuous power density of 12.5 kW/kg.

According to co-founder and CEO Jason Sylvestre, the 220-kg HPDM-3000 will offer a compact and adaptable architecture for flexible integration with existing and new powertrains and be able to drive propellers or high-bypass turbofans without a gearbox. The H3X engineering team is prioritizing fault tolerance and redundancy with 12 independent drive sectors that will allow the propulsion system to continue operating with up to 90 percent power in the event of a non-recoverable fault in one of the sectors.

“We haven’t seen anything else being commercially offered with more than one or two sets of redundant windings/inverters,” Sylvestre told FutureFlight. “The electric regional and narrowbody jet market is still in its infancy. Airframers need high power density, aviation-grade systems in the MW class to electrify their aircraft, and those currently don't exist. This electric-propulsion unit will serve a critical unmet need in the supply chain and trigger an acceleration of progress toward widespread carbon-free, sustainable aviation."

Major aircraft engine manufacturers, including Rolls-Royce and Safran, are investing heavily in electric propulsion, with active programs focused on both all-electric and hybrid-electric powertrains (see below). Start-ups, including MagniX, Ampaire, and VerdeGo Aero, are also advancing electric propulsion systems for retrofitting existing aircraft and supporting new platforms.

The new drive is based on the same core technology H3X is proving out with the 250-kW HPDM-250 integrated motor drive that it has developed as a technology demonstrator to showcase innovations in electric machines, power electronics, material science, and advanced manufacturing. The drive weighs just 18 kg (40 pounds), and the company claims this is around one-third the weight of currently available motor drives at the same power level.

Detailed design work for the HPDM-3000 should be complete by the end of this year, with a full-scale prototype expected to be ready for testing in the third quarter of next year. Additional units will be available for customers and partners in 2024.

Sylvestre explained that by integrating all the elements of the propulsion system, including inverters, into a single housing H3X will reduce the mass of the hardware required, including expensive phase cabling and connectors. He said that the modular HPDM-3000 can be stacked up to six times to deliver up to almost 17 MW of propulsion power for even larger aircraft.

The H3X team says it is agnostic regarding the energy storage used with the EPU, and so this could be employed with battery or hydrogen fuel cells. Additionally, the HPDM-3000 includes 12 HVDC connectors so it can be powered from multiple independent energy storage strings to increase fault tolerance and redundancy upstream in the system.

Sylvestre said H3X is looking to partner with other propulsion innovators as well as aircraft manufacturers to bring this technology to market. “We see this becoming the gold standard for regional and narrowbody electric aircraft propulsion,” Sylvestre commented. “There is nothing out there that compares in terms of power density, fault tolerance, and modularity.” That said, he acknowledged that these bullish claims will need to be backed up with extensive testing. H3X’s goal is to refine the design of the drive for a  specific customer application.

The young company’s engineering cohort draws on colleagues with past experience at companies such as General Electric, SpaceX, and Tesla. It raised an initial $6 million in seed funding, and it hopes to launch a Series A funding round later this year to increase its war chest to complete the development and launch production of the HPDM-3000.

Last week, Rolls-Royce announced plans to develop new turbogenerator technology to support hybrid-electric powertrains with power requirements of between 500 kW and 1.2 MW. Last year, the company’s Power Generation System 1 test bed generated more than 1 MW of power in ground trials, with a goal of achieving an output of 2.5 MW in further testing. It is also developing all-electric propulsion systems for four-passenger eVTOL aircraft being produced by Vertical Aerospace and Eve.

In February, Rolls-Royce and Brazilian airframer Embraer launched a joint study to evaluate multiple propulsion options for a proposed new regional airliner. Embraer has plans for a new Energia family of zero-emissions aircraft with between nine and 50 seats. Rolls-Royce is also working with Italy’s Tecnam to provide a propulsion system for the P-Volt electric version of its P2012 aircraft.

France-based Safran expects to start deliveries next year of its EngineUs family of electric motors, which currently offer power outputs of between 50 and 500 kW. These have been selected for hybrid-electric aircraft being developed by Aura Aero and VoltAero, and also for Bye Aerospace’s all-electric eFlyer family of two- and four-seat light aircraft.

In the U.S., MagniX is producing a family of 350-kW to 650-KW electric propulsion units. These are intended to convert existing commuter aircraft such as the Cessna Grand Caravan and the DHC-2 Beaver, and also to power Eviation’s new nine-seat Alice model.