Highlighting the increasing awareness and appeal of vertical takeoff and landing (VTOL) solutions outside the traditional domains of the rotorcraft industry, Bell returned this week to the annual Consumer Electronics Show (CES) in Las Vegas with its "full vision" of a practical urban air taxi, dubbed the Bell Nexus.
"As space at the ground level becomes limited, we must solve transportation challenges in the vertical dimension," said Bell president and CEO Mitch Snyder. "We believe the design, taken with our strategic approach to build this infrastructure, will lead to the successful deployment of the Bell Nexus to the world."
The full-scale Nexus display builds upon the fuselage mockup unveiled at last year’s CES and features a central wing, integrated landing skids, and a modified V tail topped by a short horizontal stabilizer. The flight model will use a hybrid/electric distributed propulsion system feeding six tilting ducted fans, each powered by individual electric motors.
The six-fan design is a compromise between quad- and octo-rotor designs seen on other urban VTOL designs to provide system redundancy and space for passengers to safely embark and disembark the vehicle while operating. The ducted fans also offer improved performance and a quieter noise signature than comparable open rotor designs, according to the company.
Bell also announced four collaborating partners on Nexus, with Safran providing the hybrid propulsion and drive systems. Thales will provide flight control computer hardware and software, Moog will develop flight control actuation systems, and Garmin will integrate the avionics and the vehicle management computer.
'Working the Problem' with Current and Near-Future Technologies
While not expected to enter widespread service until the mid-2020s, the Nexus features a mix of existing and forward-leaning technologies intended to surmount today’s market concerns and regulatory hurdles while also providing a path towards future evolutions.
For example, the Nexus propulsion system incorporates a series hybrid layout in which a turbine engine feeds an electrical distribution system, which in turn routes power to a battery pack that drives the fan motors. In addition to providing system redundancy in the event of turbine failure, the series hybrid architecture offers an upgrade path towards eventual fuel cell and/or full-electric propulsion.
Similarly, the prototype's cabin is configured in a "4+1" layout with room for a single pilot/operator in addition to four passengers—a bridge between existing capabilities and regulations, and a future that might ultimately enable fully autonomous Nexus operation.
"We believe the great engineering endeavor of all these things is working the problem," said Bell vice president of innovation Scott Drennan. "That is the only way the operational, certification, manufacturing and technology frameworks [required for practical urban air taxis] will come to be solved to offer a safe and reliable solution to the future of mobility."
While Bell’s CES 2018 display emphasized the passenger experience onboard an urban air taxi, this year the company will focus on the pilot/operator of such vehicles. An array of augmented reality Future Flight Controls (FFC) simulators—fitted in single-, dual- or tri-control configurations, the latter essentially emulating current helicopters—will help Bell gauge feedback on what could evolve as the final control configuration for the Nexus and other urban VTOL vehicles.
Bell will incorporate user data from each configuration to determine the actions and interfaces that are most intuitive to remain under the control of a human operator, and which aspects of vehicle control might be automated. The company plans to feature the portable FFC simulators in a variety of venues, ranging from aviation industry events and trade shows to high schools.