The mockup of Bell’s (Booth No. N1816C) Nexus concept urban air mobility vehicle (UAM) is making its NBAA debut this year. Bell unveiled the design in January and has formed “Team Nexus”—a development team of seasoned industry OEMs including Safran (engines/hybrid propulsion), Electric Power Systems (battery and battery management), Garmin (autonomous vehicle management computer systems), Thales (flight control systems and avionics), and Moog (flight control actuation systems). Bell is also partnering with Japan’s Sumitomo to provide a variety of related services, including air taxi. Bell hopes to have a product to market by the mid-2020s, said Chad Stecker, program manager for the Nexus. Stecker declined to offer additional specifics with regard to the program’s timeline.
As currently envisioned, the Nexus features a 4 +1 cockpit/cabin layout, a central wing, integrated landing skids, and a modified V-tail topped by a short horizontal stabilizer. The +1 in the cabin layout is designed for the pilot. While it is likely early UAM vehicles such as electric vertical takeoff and landing (eVTOL) aircraft will be required to have a pilot on board, a growing number of industry executives believe that fully-autonomous vehicles will be required in order to drive down operating costs to the point where they can appeal to a mass market. Earlier this year, Scott Drennan, Bell vice president of engineering innovation, told an industry conference, “I want it to be [full] autonomy right away, and I think the technology is there to do that.” Drennan cited the need for 10,000 additional vehicle pilots just for UAM’s early-stage deployment and how the addition of those pilots would inflate direct operating costs.
The Nexus flight model will use a hybrid/electric distributed propulsion system feeding six tilting ducted fans, each powered by individual electric motors. The ducted fans also offer improved performance and a quieter noise signature than comparable open-rotor designs, according to the company.
Bell is no stranger to tilting, ducted-fan technology. Its X-22 prototype ducted-fan V/STOL flew between 1966 and 1988 as part of a U.S. Navy research program. That eight-seat aircraft used a quartet of ducted fans powered by four GE YT-58-GE-8D turboshafts to reach speeds of up to 220 knots. While the X-22 was comparatively heavy at an mtow of 17,640 lbs. and somewhat less than fuel efficient, certain design aspects translate directly into Nexus, such as control surfaces inside the ducts. However, Team Nexus understands that to succeed in the UAM market, it needs to offer a vehicle that is lighter, greener, faster, and more economical to produce and operate than the X-22 or even today’s helicopters, Stecker said.
Systems Design
“Our goal is to bring the convenience of that [urban air] mobility and on-demand model to the mass market. We understand to do that it needs to be not only operationally effective but also at a price point that is commercially viable for the general public. Our goal is to bring the vertical dimension to everyone,” Stecker said. While declining to speculate on a price point for the vehicle, Stecker said, “Everything we are doing is through the lens of complexity and costs and bringing those technologies forward to be safe, reliable, and affordable transportation.”
That means creating a very different vehicle and building it in a very different way as opposed to conventional helicopters that take sometimes a decade or more to develop and bring to market. “Everything we do is designed to move us faster through the development program and shorten those cycles of learning,” Stecker said. “We actually have a rapid prototyping section that resides within our technology and innovation organization. Manufacturing is one of the four frameworks we are focusing on and we are developing dependable, repeatable assembly processes that are critical to our technologies on the program. That’s what you need to be successful in the urban mobility space.”
That includes using new manufacturing techniques such as 3D printing, Stecker said. “Nothing is off the table. We are working on various technologies that are at various levels of readiness. This is a different program and a different market. We have to able to design it [the vehicle] differently, manufacture it in a green manner, and produce it in quantities that are higher than traditional programs.”
However, the level of resourcing Bell has decided to devote to Nexus remains something of a mystery. On a conference call with stock analyst earlier this year, the chairman of Bell parent Textron, Scott Donnelly, called it “relatively small,” and added “we need to see how does that market really play out. I think there is a lot of uncertainty.” Donnelly said Bell’s more pressing priority was effectively competing for the Pentagon’s Future Vertical Lift (FVL) program with products such as Bell’s V-280 tiltrotor technology demonstrator.
While declining to disclose what the development funding for Nexus is, Stecker said that Bell is “a mature OEM that understands [aircraft] development. Flight is something we do every day.”
Earlier this year, Bell’s Drennan characterized Nexus as a “full-blown development program” that was ramping up to a dedicated staff of more than 100. Donnelly told analysts that, if urban air mobility happens, “clearly, our team at Bell can design and build aircraft that would fit that marketplace.”
Stecker said Bell already is developing components, subsystems, and systems for the aircraft. While initial designs are likely to feature hybrid propulsion, he said that full electrification was still likely at some point. “We do believe in the future of full electrification.”