Air Force eVTOL Research and Development Programs Make Remote Pilot Progress

June 1, 2023

U.S. Air Force pilots completed remote-controlled flights of Joby Aviation’s S4 electric vertical takeoff and landing (eVTOL) prototype aircraft at the company’s California-based facility in April. It was the Air Force’s latest live eVTOL demonstration after airmen performed flights with LIFT’s Hexa at Eglin Air Force Base, Florida in November 2022.

The Department of Defense (DoD) has been providing access to testing facilities, early operational experience and offsets to research and development costs for Joby, LIFT and several other eVTOL companies and startups since launching the Agility Prime initiative.

AFWERX Agility Prime was formally launched by the Air Force in April 2020 with a focus on accelerating development of commercial eVTOL technologies. Through the Department of the Air Force Small Business Innovation Research (SBIR) and Small Business Technology Transition (STTR) programs, run by AFWERX AFVentures, the program works with the small business community to advance the eVTOL industry.

Three years later, Joby Aviation has emerged as a leader among the commercial eVTOL developers working with the Air Force. During the demonstration at Joby’s facility in April, four Air Force pilots assumed remote pilot-in-command of a routine transition flight. Lt. Col. Tom Meagher, AFWERX Prime Division Chief described the April flights as “an incredibly important milestone for the program, providing key insights to actual operations, maintenance information, and use case validation for Advanced Air Mobility aircraft.”

The flights preceded AFWERX Agility Prime’s April 25 announcement that it has entered into a third extension of its contract with Joby. The $55 million contract extension brings the total potential value of Joby’s current contract with the Air Force up to $131 million. Under the extension, Joby will deliver and operate up to nine of its eVTOL aircraft to the Air Force and other government agencies. The first two aircraft are expected to be delivered to Edwards Air Force Base, California, by early 2024, and will be used to demonstrate a range of potential logistics use cases, including cargo and passenger transportation, according to Joby.

In doing so, they are expected to become the first electric air taxis to be stationed at a U.S. military base.

“The Agility Prime program is a remarkably successful example of how public-private partnerships can deliver trailblazing technology at speed,” said JoeBen Bevirt, Joby CEO. “We’re grateful for the support of the program and for the U.S. government’s wider commitment to global leadership in this important new sector. As well as allowing us to explore the wide range of potential use cases across the U.S. government, our defense partners have also provided us with high-impact support as we prepare for commercial operations in 2025.”

Joby’s eVTOL Technology

Although the Air Force pilots controlled it remotely in April, Joby’s all-electric prototype eVTOL, the S4, has enough seating for one pilot and four passengers to fly up to 150 miles on a single charge at a 200 mph cruise speed. The S4 achieves vertical takeoffs, landings and transitions to forward flight using a distributed electric propulsion (DEP) system powered by commercial off-the shelf lithium-ion batteries, an 811 NMC cathode and a graphite anode cell.

DEP on the S4 is enabled by the six tilting propellers attached to the top of the aircraft’s conventional fixed wing and V-tail, according to airworthiness criteria and design details released by the Federal Aviation Administration (FAA) about the S4. Joby’s description of the S4 notes that four of those propellers tilt vertically to include the aircraft’s motor nacelle, and the other two tilt vertically with a linkage mechanism. S4’s aircraft structure and propellers are constructed of composite materials.

Shortly after completing the Air Force remote flight demonstration in April, Joby shared additional details about the S4’s embedded systems architecture in a first quarter letter to shareholders. According to the letter, Joby is designing, building and testing its embedded flight electronics systems, computers and wiring in-house.

“Our software also benefits from speaking a common language, with all of our hardware sharing common interfaces, meaning there are no layers of conversion or translation required in each connection. We will also be able to verify and deploy software updates more easily over the life of the fleet thanks to owning the majority of the tech stack,” the company notes in the shareholder letter.

Development of the S4’s flight electronics is being led by Nate Martin, Joby’s lead electrical engineer for the S4 development program. Martin first joined Joby in 2017, after serving as the lead electrical engineer for Tesla’s Model-S and Model-3 battery module boards. Martin credits the use of “integrated design” to enabling his team’s development of a flight computer — that weighs less than an iPhone — capable of receiving pilot inputs and sensor data from around the aircraft and translating it into instructions for the propulsion units and control surfaces. In a video highlighting the eVTOL’s flight electronics released by Joby shortly after their Air Force pilot remote flying demonstration, Martin said the S4’s network switch is smaller than a standard sheet of paper.

“Since we own the entire tech stack, we’ll be able to verify and deploy software updates over the life of the fleet following FAA approval. The flight electronics are just one piece of the hard engineering challenges we’ve tackled at Joby,” Martin said.

While Air Force pilots traveled to Joby’s facility in California to perform the remotely piloted flights in April, Joby, in its latest annual report published in March, Joby said it does not plan on selling its aircraft to individual or independent third parties or customers. Instead, they will manufacture, own and operate the aircraft and deliver vertically integrated transportation services. In the case of the Air Force, this will occur in a “contractor-owned, contractor-operated model” on U.S. military installations.

LIFT Aircraft’s Hexa

In November, Eglin Air Force Base, Florida, hosted a remote-controlled eVTOL demonstration similar to the one performed at Joby’s facility in California, with a much different aircraft — LIFT Aircraft’s Hexa. The test flight was described by the Air Force as an “early step in creating a training program to incorporate Airmen into the aircraft’s flight operations.”

The training served as a proof of concept for how to develop responsive training programs for future government operators of uncrewed cargo-carrying eVTOLs. “Our team’s prior rotary wing experience gave us a framework of reference to work from regarding aerodynamics that apply to vertical takeoff and lift aircraft, crew resource management, and general flight operations at a military airfield,” said Maj. Victoria Snow, a 413th FLTS helicopter pilot who participated in the Hexa training. “Even though the technology is vastly different, understanding the mechanics of helicopter flying translates well to operating the Hexa.”

Hexa is a single seat eVTOL powered by 18 independent overhead electric motors and propellers that also uses DEP. The aircraft’s main interface is a seven-inch touchscreen accompanied by a three-axis joystick inside the cockpit. Hexa’s airframe is built entirely of carbon fiber and weighs 432 pounds.

LIFT Aircraft was first established in 2017 and went public with the Hexa design the following year, prior to becoming one of 15 eVTOL developers to join the Agility Prime initiative in 2020.

While the Eglin demonstration involved the Air Force in teams of two pilots each remotely controlling the aircraft, LIFT’s certification path involves a plan for one person onboard, with no pilot’s license required. The Austin, Texas-based company is pursuing a certification path under the FAA’s Part 103 regulation of ultralight aircraft that are used for recreation and sport.

Hexa’s participation in the Eglin Air Force Base demonstration in November helped to familiarized Air Force pilots with the basics of operating the aircraft. The three Airmen who participated – an officer and a senior NCO from the 413th Flight Test Squadron and a senior NCO from Air Education and Training Command’s Detachment 62, had background in rotary wing aircraft.

The team began with classroom and simulator training before taking remote control of Hexa during the two-week familiarization training. The flight requires a two-person team. One person controls the movement of the aircraft, while the other monitors the aircraft systems, batteries and other critical flight performance parameters.

“My first flight experience was both rewarding and insightful,” said Snow, who has been observing and advising on Hexa test operations since March. “Getting the chance to fly the Hexa gave me a deeper understanding of the system’s inner workings and an understanding of how stable and responsive the Hexa aircraft is and of its possible future capabilities.”

According to a March 16 press release about a flight demonstration of Hexa completed in Osaka Japan, LIFT “has formally concluded Phase 1 flight test and beginner flight envelope development with the U.S. Air Force.”

Next Steps in Air Force eVTOL R&D

A Request for Information (RFI) published by the Air Force Life Cycle Management Center’s (AFLCMC) in October 2022 provides a preview of some of the earliest use cases that the Air Force is considering with eVTOLs. A key aspect of electric-powered aircraft that the Air Force and other DoD agencies want to address is the cost of operating them versus its existing conventional rotary wing assets, mainly helicopters. As demonstrations continue, DoD officials want to ensure the cost of operating and maintaining eVTOLs will not exceed the existing cost of completing the same missions with helicopters. In the RFI, the Air Force notes its focus on “evaluating eVTOLs for business use-cases of eVTOL aircraft for distinguished visitor, or DV, transport and test range logistics support missions by supplementing current Department of Defense capabilities in each of those mission areas.” The next major milestone for the Air Force will come in early 2024, when Joby is expected to deliver its first two aircraft to Edwards Air Force Base.

This article was written by Woodrow Bellamy III, Senior Editor, Aerospace & Defense Technology.

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