• 28 Aug 2024 12:00 PM
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Elroy Air Tackles Cargo Delivery

Featured Image: Elroy Air’s autonomous, hybrid-electric Chaparral C1 prototype in flight. (Elroy)

By Pat Host
Vertiflite, September/October 2024

Elroy Air is leveraging cutting-edge technology in both propulsion and vertical lift aircraft design in its push for success in the commercial and military cargo delivery markets.

On Nov. 12, Elroy Air set an aviation milestone when it flew the world’s first turbogenerator-powered hybridelectric vertical takeoff and landing (eVTOL) aircraft, the Chaparral C1 prototype, the company said in a press release. Utilizing both its turbogenerator system and highpower batteries, the Chaparral C1 took off vertically and flew for 57 seconds at its test flight facility in Byron, California. 

Elroy Air is setting new standards in turboshaft propulsion with a creative approach to hybrid-eVTOL (heVTOL). David Merrill, Elroy Air co-founder and CEO, told Vertiflite that the company uses a PBS TS100 turboshaft engine coupled to an electric generator. Merrill said this is important because electrification has many benefits in redundancy, which creates safety, with the simplicity and robustness of electric motors, which feature a single moving part.

Merrill said the Chaparral, with its series-hybrid design, takes the electricity produced by the turboshaft engine, coupled with the electric generator to power the aircraft and charge a small onboard battery. This provides an onboard-produced source of electrical power. Merrill said the company picked the 241-shp (180-kW) TS100 because of its light weight of around 130 lb (59 kg), its prior use in aviation and its availability. První brněnská strojírna (PBS) — “First Brno Engineering Plant” — was originally founded in the Czech Republic but has had offices in the US for more than a decade, and is a qualified US Department of Defense (DoD) supplier.

Merrill said integrating a commercial-off-the-shelf turboshaft engine with an electric power-generator and battery to drive the electric propulsion required Elroy Air to overcome several difficult technical hurdles. The primary challenge of the heVTOL aircraft, he said, is the coordination of power production with power consumption.

Electric motors used for propulsion can increase and reduce power demand rapidly, especially in hover to reject disturbances, while a turboshaft engine operates with a significantly slower time constant — it does not ramp quickly. Merrill said Elroy Air’s integration work, including coordinating how the vehicle’s onboard battery sinks and sources electrical current, ensures that propulsion power demands are met during flight.

“Making this powerplant — having elements with diverse time constants — work for a lift-plus-cruise VTOL aircraft was a novel problem that our team was the first to solve,” Merrill said. “In order to move the C1 vehicle into flight test, we first had to push through substantial technical development and integration.”

Elroy Air is also utilizing the lift-plus-cruise design with the Chaparral, which allows the aircraft to minimize hover time during takeoff and landing, the two most energy intensive portions of flight.

Elroy Air has two prototypes of its C1 Chaparral: The C1-1 technology demonstrator and the new C1 prototype, which is now in assembly. As of late July, Merrill said the company had made 20 flights on the C1-1, utilizing its hybrid powertrain since November. The majority of these have taken place at Elroy Air’s test facility with several at Yuma Proving Ground in Arizona.

The aircraft’s eight vertical propellers and four forward-facing propellers also leverage the Chaparral’s 26.3-ft (8-m) wingspan. Andrew Mearns, a sales coach and consultant with Multicopter Aerospace Consulting, told Vertiflite this dramatically reduces energy consumption during forward cruise flight.

Mearns said he liked the effectiveness of the Chaparral’s design. Not only does the aircraft have plenty of redundancy in case a motor fails, but the wing provides aerodynamic efficiency while the powerplant structure with the generator and battery work in tandem to supply as much power as necessary for each flight phase. Mearns said this allows the powerplant to be small, with a relatively low fuel burn requirement.

Mearns also said the Chaparral’s hybrid-electric design’s improved range compared to a purely battery-powered aircraft provides safety and reliability benefits, especially in autonomous operations. These include having to fly around poor weather or land at an alternate airport or landing site. The Chaparral has a range of 300 miles (483 km) and a 300-lb (136-kg) payload capacity.

Merrill and his co-founder, Clint Cope, were inspired to develop the Chaparral after hearing laments from commercial shippers and US military logisticians about the dearth of large delivery drones. Other delivery drones on the market featured very small payload capacities. Wing, a subsidiary of Alphabet, can carry packages weighing around 2.5 lb (1.1 kg), while Zipline drones can carry payloads weighing up to 8 lb (3.6 kg).

Elroy Air is using a variety of technologies from the robotics and automotive industries to enable the Chaparral to automatically pick up and drop off cargo without much human attention. The company embeds ultra-wideband beacons onto the Chaparral and the cargo pod. Each cargo pod has a unique identifier, which allows the Chaparral to triangulate the positions and distances. Merrill said the Chaparral, with electric motors in its wheels, can taxi itself and perform basic warehouse navigation on the ground.

The Chaparral debuted in January 2022 at the Hiller Aviation Museum in San Carlos, California, in conjunction with the VFS Transformative Vertical Flight 2022 conference. The Chaparral is designed to autonomously find and load/unload a cargo “canoe.” (VFS staff photos)

The Chaparral also features automotive light detection and ranging (lidar) to safely navigate on the ground without bumping into objects. The aircraft charts its course, drives until it is over the cargo pod and then uses lidar to perform the final alignment with the cargo pod. The Chaparral then uses a proprietary robotic system that lifts the cargo pod and latches it to hardpoints on the vehicle for flight. Upon landing, the Chaparral performs that series of tasks in reverse by setting the cargo pod on the ground, unlatching and driving away.

“You don’t need a person to come out and stuff boxes or pallets into the aircraft one at a time,” Merrill said. “Just pick up the whole payload [and then] drop off the whole payload.”

Elroy Air also has extensive military business and is participating in a key US Navy demonstration. This could eventually lead to deliveries of the Chaparral cargo delivery system for use in worldwide military autonomous logistics missions.

Merrill said Elroy Air has received six Pentagon awards to develop an autonomous aerial logistics capability. These include contracts with US Air Force (USAF) Special Operations Command and AFWERX, the USAF’s venture division, each focused on testing and maturing a set of core technologies. Elroy Air recently began working with the US Army on a contract to adapt Chaparral systems for ground operations in the most austere environments as contested logistics have come into sharper focus.

Elroy Air, serving as subcontractor to Leidos, was approved to demonstrate an autonomous prototype in the Medium Aerial Resupply Vehicle-Expeditionary Logistics (MARV-EL) competition for the Navy and Marine Corps Small Tactical Unmanned Aircraft Systems (PMA-263) program office. Merrill said MARV-EL is the Marines’ medium cargo uncrewed aircraft system (UAS) program and one of the first assessments of larger cargo UAS across the DoD (see “Advancing Autonomy for Cargo,” pg. 28). The development and testing are part of a contract awarded in 2022 to develop and demonstrate a UAS that can autonomously resupply forward-deployed ground forces for the Marine Corps. Elroy Air in July demonstrated various Chaparral capabilities at Yuma Proving Ground that the company has been testing over the past six months. These included flying with heavier payloads, at higher temperatures, wind envelope expansion and autonomy features.

Merrill said the Chaparral being the first turbogenerator heVTOL aircraft to fly was a significant milestone for two reasons. The first is that the C1 is the configuration of the aircraft that Elroy Air plans to build its business around. The second is that hybridelectric is an important next step in aviation because it serves as a next plateau of productivity and value for aircraft design as aviation moves toward electrification.

Merrill believes electrification is inevitable in aviation because it solves many problems and is inherently clean. While battery technology is currently not good enough to power a lot of useful missions, being able to leverage the greater energy density of fuel adds range and operational flexibility.

“Being able to base the aircraft in places where you don’t necessarily have charging is extremely important for logistics,” he said. Charging infrastructure at these locations will either not exist or will be very difficult to develop. But these locations will have fuel, Merrill said.

The early stages of Elroy Air’s business emphasize defense, along with humanitarian and commercial partners that operate largely outside the US. Merrill said the company is already generating revenue with its multiple DoD contracts. He also believes the certification and regulatory requirements for early defense deployments will be more straightforward to satisfy. This is due to early deployments in austere operating environments having low risk to personnel, such as flights over water. This early chapter will enable Elroy Air to mature the Chaparral and gain substantial operational experience on the path to significant commercial business, which will scale later, Merrill said.

Jonas Murby, a principal with AeroDynamic Advisory, told Vertiflite that he was impressed with Elroy Air’s approach to automation on functional architecture. Combining the fixed wing with the lift, he said, is probably easier to implement without too much development compared to other aircraft architectures. Murby also said that Elroy Air’s approach to automated heVTOL commercial cargo delivery has a lot of potential in the long run as transportation networks gradually adapt to new technologies.

About the Author
Pat Host is an experienced Washington media relations and news professional. He’s previously covered aviation technologies for Janes, Defense Daily, Rotor & Wing and other news sites, and his work has appeared in publications such as Vertical and Aerospace America. He can be reached at patrick. host@gmail.com.