13 Mar 2023
For many entrants in the race to develop electric vertical takeoff and landing (eVTOL) aircraft, the speculative air taxi market is the prize at the end of the finish line — one that could someday yield orders for thousands of aircraft to ferry millions of passengers around congested cities. However, with numerous regulatory and social barriers standing in the way of that market — on top of the very real technological challenges associated with building and flying eVTOL aircraft — this type of on-demand urban air mobility (UAM) could take many years to come to fruition.
But there are other potential applications for clean, quiet eVTOL aircraft that are driving innovation in the field. Notably, the biotech company United Therapeutics, under the leadership of CEO Martine Rothblatt, wants to use eVTOL aircraft to expeditiously transport manufactured human organs between its facilities and receiving hospitals. To that end, it is funding several eVTOL programs that together reflect an ambitious yet practical strategy for transitioning away from the fossil fuel-powered helicopters it uses to deliver organs today.
“Ambitious yet practical” is a guiding philosophy for Rothblatt, who in the 1990s created a new market as the founder of Sirius satellite radio (now SiriusXM). She established United Therapeutics after her daughter was diagnosed with pulmonary arterial hypertension; the company proceeded to develop a new medicine to treat it. More recently, the United Therapeutics subsidiary Lung Biotechnology has pioneered innovative ways of restoring damaged donor lungs, and its “remanufactured” organs have been successfully transplanted into hundreds of patients.
This is just the first step in realizing an ambition that, in its own way, is as radical as the vision for UAM. United Therapeutics is actively engaged in research related to xenotransplantation — the transplanting of animal organs into humans — which could dramatically increase the supply of available organs. Longer term, the company is also pursuing the 3D printing of organs, which it hopes will eventually lead to a world of “organs on demand.”
As Rothblatt told a 2016 gathering of the Tesla Motors Club, “When you’re talking about not a few hundred organs, but hundreds of thousands or millions of organs, you are going to need a very large fleet of helicopters delivering all these.” The emissions that would be generated by a conventional rotorcraft fleet of that size simply aren’t acceptable to Rothblatt, who is already well known for prioritizing solar power and other environmentally sustainable technologies at United Therapeutics.
“When people push back on me, and say, ‘Why are you so big on the solar?’ ... I do say to them, and I do believe, what is really the point of saving people’s lives with an organ transplant if all of humanity could be wiped out in a climactic existential event from global warming?” she explained. “If we just think a little bit harder, we can do the good thing and the green thing at the same time.”
Tier 1’s R44 eHelo
Just as United Therapeutics is simultaneously pursuing several different approaches to increasing the supply of available organs — each with a different horizon for implementation — the company is spreading its investment in eVTOL technology across several projects with varying prospects for certification.
The most straightforward of these is an electric-powered Robinson R44 helicopter, which provides a baseline for what eVTOL projects can achieve using already certified airframe technology. Lung Biotechnology partnered with Tier 1 Engineering in Santa Ana, California, to develop the modified aircraft, which on Dec. 7 set a Guinness World Record for the farthest distance traveled by an electric helicopter — 30 nm (56 km) — with test pilot Ric Webb of OC Helicopters at the controls.
Tier 1 modified an R44 for Lung Biotechnology to fly on battery power; Martine Rothblatt pumps her fists while receiving the Guinness World Record certificate for the farthest distance traveled by an electric helicopter. (Tier 1 photo)
The prototype replaces the heavy Lycoming IO-540 piston engine used on conventional R44s — which has a wet-installed weight of around 500 lb (225 kg) — with custom Yasa twin electric motors and a Rinehart motor control system that weigh just 100 lb (45 kg). Of course, this weight savings is offset by the aircraft’s Brammo lithium polymer batteries, which are attached under the belly and weigh approximately 1,100 lb (500 kg).
According to Tier 1 principal Glen Dromgoole, his team was able to accomplish this retrofit without any modifications to the R44’s flight controls or drive system. “From an engineering perspective, I’m so impressed with the design, and the simplicity of the design. That’s really what makes it such a great electric helicopter,” he said in an interview in December. Crucially, the aircraft retains the ability to autorotate, a well-established safety feature that facilitates certification.
Dromgoole confirmed that the aircraft that set the Guinness World Record (N3115T) is the same one that first flew in September 2016, and set other records in early 2017. Tier 1 then paused flight testing to refine the aircraft’s underlying battery and motor technology. Now, it’s in the process of incorporating those improvements into a second prototype that it expects to fly sometime this year. With this version, Tier 1 is aiming for at least an hour of flight time with 600 lb (270 kg) of useful payload, a goal that Dromgoole characterized as “very achievable.”
Such an aircraft could readily accomplish some of Lung Biotechnology’s shorter organ transports, even if it’s still impractical for most operations performed by conventional helicopters. According to Dromgoole, Tier 1 intends to pursue a supplemental type certificate for this second version of the electric R44. Indeed, the company has already submitted a certification plan to the Federal Aviation Administration (FAA), which so far has been “extremely supportive and interested in this project,” he said.
Tier 1 said in 2016 that had been contracted by Lung Biotechnology to create an electrically-powered semi-autonomous rotorcraft for organ delivery (EPSAROD).
Beta Technologies’ Ava XC
While the R44’s efficient rotor system and lightweight airframe make it a particularly good fit for conversion to electric power, conventional helicopter designs will never be able to fully realize the mechanical and aerodynamic efficiencies enabled by distributed electric propulsion (DEP). Consequently, United Therapeutics is also investing in eVTOL projects that leverage more of the advantages of DEP, even though they might face longer paths to certification.
One of those is the Ava XC demonstrator that was unveiled by Burlington, Vermont-based Beta Technologies in January. Piloted by Beta founder Kyle Clark, Ava is already more than 180 flights into a demanding FAA-approved flight test program, with another 50 or so left to go. Once the flight test program wraps up, Clark intends to fly Ava across the United States on an exhibition certificate, supported by a 1982 Eagle bus that Beta has converted into a mobile charging platform with biodiesel generator.
The two-ton Beta Ava XC is built around a Lancair ES cabin with wing and tail modifications from RDD Enterprises. Ava made its first tethered flight on May 23, 2018, and its first free flight on June 22. (Photo by Eric Adams. Used with permission.)
Close-up of the front outrigger. The two motors are powered two separate battery packs located in the aircraft’s nose, shown in the background with the skin removed. (Photo by Eric Adams. Used with permission.)
Ava XC is a testbed for Beta’s future eVTOL concepts for Lung Biotechnology’s organ transportation. (Photo by Eric Adams. Used with permission.)
The approximately 4,000 lb (1,815 kg) aircraft is built around a Lancair ES cabin, with a 35 ft (10.7 m) fixed wing and tail modification from RDD Enterprises. Extending from either side of the nose and tail are lightweight, carbon fiber outriggers developed by Blue Force Technologies, which provide mounting points for four pairs of counter-rotating propellers, each driven by a pair of 124 hp (92 kW) permanent magnet motors. The aircraft is powered by two lithium-ion battery packs — one for the top and one for the bottom layer of motors — which together total 166 hp-h (124 kW-h).
Because the Beta team believes that fully autonomous eVTOL aircraft are still many years from certification, Ava has been developed as a piloted aircraft, with hybrid flight controls. In the pilot’s left hand is a collective lever that resembles a helicopter collective; this modulates the speed of the propellers and, therefore, thrust.
With the right hand, the pilot manipulates a sidestick with tripleredundant sensors that is coupled to both the mechanical flight control surfaces and the fly-by-wire controller for distributed propulsion. The right thumb controls a bump switch that tilts the nacelles, allowing the pilot to modulate the angle as a function of sink rate. Traditional foot pedals control the rudder and the clockwise/counter-clockwise differential of the rotors while hovering, and allow for differential braking while on the ground.
Beta Technologies CEO and test pilot Kyle Clark flies the Ava simulator, developed by Austin Meyer, the creator of the X-Plane flight simulation software. (Photo by Eric Adams. Used with permission.)
According to Clark, Ava has already achieved speeds of up to 72 kt (133 km/h) and a maximum altitude of 100 ft (30 m), and flight in winds as high as 25 kt (46 km/h). Clark has also been demonstrating various failure modes in flight, including failures of individual motors and battery packs, and failure of the inertial measurement unit (IMU). The aircraft’s tall, springy test gear has been designed specifically to accommodate such tests with minimal damage to the airframe.
In its current form, Ava has an estimated maximum range of 130 nm (240 km), which is still very limited compared to conventional VTOL aircraft. However, Clark plans to unveil a successor to Ava as early as this year, which will reportedly look much different and be capable of flying as far as 250 nm (465 km).
An Autonomous Future
United Therapeutics has interests in other eVTOL projects, too. In 2017, it commissioned Zenith Altitude of Bromont, Québec, to work on a semi-autonomous tiltwing concept called EOPA (for “Electrically-powered Optionally-piloted Powered-lift Aircraft”). Other Canadian organizations — including NGC Aerospace, Optis Engineering, Brio Innovation, and the Center for Advanced Technologies at the University of Sherbrooke in Québec — have partnered with Zenith to develop the aircraft, with a range similar to the one envisioned for Ava’s successor. Reportedly, the team has already demonstrated the feasibility of aircraft control during tiltwing transitions.
Zenith Altitude’s concept for its Electrically-Powered Optionally-Piloted Powered-Lift Aircraft (EOPA) for rapid transportation of human organs and other missions. (Zenith Altitude image)
Last year, the Sherbrooke-based newspaper La Tribune reported that an offshoot of Lung Biotechnology called Unither Bioelectronics — “Unither” is a common contraction for United Therapeutics and its subsidiaries — had broken ground on a new research and development center in Bromont. The company has also purchased a site on which to build a manufacturing plant for electric aircraft production, which could commence in the 2024-2025 timeframe, according to the report.
Meanwhile, in May 2016, Lung Biotechnology announced a collaboration with the Chinese drone manufacturer EHang — which unveiled its single-seat autonomous electric multicopter, the EHang 184, earlier that year — to develop an evolved version of the 184 called the Manufactured Organ Transport Helicopter (MOTH). The agreement has the companies working together over the next 15 years to deliver as many as 1,000 MOTH units for automated organ deliveries.
EHang has built more than 30 of its model 184 single seat demonstrators and could sell 1,000 more as the Manufactured Organ Transport Helicopter (MOTH) for Lung Biotechnology. (VFS photo)
In a press release at the time of the announcement, Rothblatt stated, “The well-known locations of transplant hospitals and future organ manufacturing facilities makes the EHang technology ideal for highway-in-the-sky and low-level [instrument flight rules] IFR route programs. We anticipate delivering hundreds of organs a day, which means that the MOTH system will help save not only tens of thousands of lives, but also many millions of gallons of aviation transport gasoline annually.”
Placing Multiple Bets
Rothblatt’s vision for electric on-demand organ transportation and transplantation appears to be serious enough that she’s funding multiple companies to explore different approaches; additional companies may also come to light.
Naturally, such a project involves many contingencies. First, United Therapeutics and its subsidiaries must successfully develop the technologies needed to manufacture organs on the scale they envision, then secure timely approval from the US Food and Drug Administration, which is hardly guaranteed. On the same timeline, the FAA must develop and implement the certification guidelines and infrastructure to accommodate fully autonomous eVTOL flights in urban airspace — also not a sure thing.
However, while this vision for an enormous fleet of organcarrying drones might seem wildly improbable when considered in isolation, it makes a lot more sense as the culmination of a deliberate progression of research and development, on both the aviation and the medical side. Rothblatt has already accomplished many things that people told her were impossible to do. If she pulls off this grand ambition, we’ll all be better off for it.