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Elroy Air Conducts Groundbreaking Flight of Hybrid-Electric Cargo Drone

November 16, 2023
Elroy Air Conducts Groundbreaking Flight of Hybrid-Electric Cargo Drone
Elroy Air’s hVTOL Chaparral C1 takes flight from Byron Airport (C83) near San Francisco. [Courtesy: Elroy Air]

By Jack Daleo

The company calls the aircraft a turbogenerator-hybrid electric vertical takeoff and landing aircraft—hVTOL, for short—and claims it’s the first of its kind to fly.

Look up in the sky: Is it a bird? Is it a plane? No, it’s a turbogenerator-hybrid electric vertical takeoff and landing aircraft—and it’s the first in the world to fly, according to manufacturer Elroy Air.

The aircraft type is a mouthful, so we’ll use Elroy’s abbreviation: hVTOL. The San Francisco Bay Area-based firm, best known for manufacturing the autonomous Chaparral cargo drone, on Sunday took the hVTOL on its maiden voyage, claiming it is the first aircraft of its kind to leave the ground.

The model that flew, the Chaparral C1, is a new variant of the manufacturer’s flagship drone. Like the original, the C1 flies autonomously with distributed electric propulsion. But the source of that power is a “turbogenerator-battery architecture” rather than a hybrid-electric powertrain.

The inaugural C1 flight took place out of Byron Airport (C83) in Contra Costa County, California, where Elroy conducts flight testing. Using its turbogenerator system and batteries, the hVTOL took off vertically like a helicopter and flew for just less than a minute before descending slowly onto a landing pad.

For its maiden voyage, the aircraft was flown remotely by a ground team, with a control pilot stationed on a nearby deck. And according to Elroy, Sunday’s flight was only the beginning—further testing will follow with the U.S. Air Force.

“This is an exhilarating day for our team and the industry as a whole,” said Elroy co-founder and CEO Dave Merrill. “This marks a major moment for the industry, as hybrid-electric aircraft enable the dual benefits of runway-independent safe redundant propulsion and long-range flight well in excess of battery power alone.”

What’s in the Sky?

The Chaparral is built to load and unload a variety of preloaded cargo pods, each designed for different use cases, all by itself. It can fly as far as 300 sm (260 nm) at a cruise speed of 125 knots, zipping around with 300 pounds of cargo.

Compared to other delivery drones, the Chaparral is massive: more than 19 feet long, with a 26-foot wingspan. However, the airframe can be reconfigured to fit inside a 40-foot shipping container, or even the cargo hold of another aircraft. And despite its size, the aircraft’s redundant rotor design allows it to fly safely without a pilot, Elroy said.

As Merrill alluded to, the firm plans to use the aircraft to enable same-day shipping for customers such as FedEx, as well as resupply for the defense industry. Mark Esper, the 27th U.S. Secretary of Defense and a member of the Elroy board, provided light details on the latter.

“[Elroy’s] work to enable autonomous cargo delivery for the resupply of troops in the field will create a game-changing capability for supporting and sustaining the United States military and allied forces in future campaigns,” Esper said.

Recently, the company brought in aerospace engineer Zach Lovering—who brings plenty of electric vertical takeoff and landing (eVTOL) experience to the table—as vice president of engineering. Lovering was the architect behind the Vahana eVTOL program of Airbus’s Acubed, as well as several projects at Zee Aero (now Wisk Aero).

“This groundbreaking initial flight of the C1 will be followed by an ongoing envelope expansion campaign in coordination with the U.S. Air Force, in which we’ll advance the vehicle’s demonstrated flight capabilities through subsequent modes of airborne operations,” said Lovering. “These modes include expanded hover, system identification, transition, and cruise flight.”

A New Kind of Propulsion

The idea to combine distributed electric propulsion with turbine-based power generation, which Elroy called a “best-of-both-worlds” solution, was first suggested by NASA researchers in 2008.

Elroy explained that it picked a turbogenerator-hybrid system rather than a full battery-electric propulsion system—which is common among eVTOL air taxis and cargo aircraft—because it gives the C1 greater energy density, and therefore range.

The architecture also allows it to fuel up in locations without electric aircraft chargers, which are scarce, because the generator runs on an unspecified kind of liquid gas. And with industry stakeholders battling over aircraft charging standards, the aircraft’s lack of reliance on chargers could pay dividends for Elroy, at least until standards are settled or infrastructure is expanded nationwide.

“The use of hybrid electric powertrains is not trivial—balancing battery and turbogenerator power output to respond to load demand requires power management systems that are properly governed to facilitate effective and efficient flight,” explained Ashish Bagai, principal at vertical flight enabler BuGi Aero.

While working as an associate research scientist at the University of Maryland’s A. James Clark School of Engineering, Bagai helped design and build the Sikorsky X2 Technology demonstrator, a coaxial helicopter model that flew 100 mph faster than production designs at the time. Elroy characterized him as an advanced rotorcraft expert.

“Such systems for true VTOL and vertical flight-capable aircraft are more complex and demanding than for fixed-wing systems because of the discrepancies in power requirements in different flight regimes,” Bagai added. “[Sunday’s flight] is a major step in the development of hVTOL flight—one that underscores the potential utility value of DEP concepts. It’s very encouraging.”

Defense, Commercial Cargo, and More

Like many emerging aircraft manufacturers, Elroy so far has done much of its flying through contracts with the Air Force. Defense applications will likely be some of the first to come to fruition for Chaparral. But that won’t be the only use case.

Since working with the Air Force Special Operations Command (AFSOC), Elroy has obtained three contracts—two small business innovation research (SBIR) awards and a tactical funding increase (TACFI)—through AFWERX, the department’s innovation arm.

Those partnerships have helped Elroy and the Department of Defense explore cheaper, uncrewed aircraft to use for potentially dangerous military resupply missions.

“AFWERX is excited to see the progress in hybrid electric powertrains for transformative vertical lift aircraft,” said Colonel Elliott Leigh, director of AFWERX and chief commercialization officer for the Air Force. “Hybrid flight marks a key technical milestone for the industry to increase VTOL range and payload while validating the investment strategies of both AFWERX Prime and the AFVentures TACFI program.”

But Elroy said the Chaparral is also in “high demand” among customers in the commercial and humanitarian logistics industries. The firm claims its order backlog—which comprises letters of intent, memoranda of understanding, and a handful of firm deposits—translates to more than $3 billion in future revenues. In January, that figure was estimated at $2 billion. Its order book is estimated at just more than 1,000 aircraft, a number the company cited in an interview with Forbes.

FedEx is perhaps the company’s most notable partner. In 2022, the two firms agreed to test Chaparral by moving shipments between FedEx sortation centers, with an eye toward launching an autonomous aerial cargo network in the near future.

The partners did not mention any Chaparral deliveries. But on SMG Consulting’s Advanced Air Mobility (AAM) Reality Index, which tracks AAM aircraft orders, FedEx is listed as having placed a non-firm order for 250 aircraft. In response to an inquiry from FLYING, Elroy said it is not sharing order details at this time.

Elroy’s largest confirmed preorder comes from Mesa Airlines, which struck a deal for up to 150 Chaparrals. Another customer, London-based humanitarian aircraft operator AYR Logistics, said it plans to buy 100 aircraft over the next five years.

More recently, the company signed agreements with helicopter operators LCI and Bristow Group. In September, Bristow put down deposits for the early delivery of five aircraft in 2025, following a preorder for up to 100 Chaparrals last year. LCI, meanwhile, placed deposits on half of its 40 preorders in January.

While no deliveries have been made yet, the first are expected to happen in 2025.

Read more here.

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