How do you create a new form of aviation? By collaborating, Uber contends. To realize its Elevate vision of urban air transport, the ride-hailing giant has assembled a phalanx of partners across the entire ecosystem from vehicles to vertiports.

Uber is also investing in internal teams to tackle what it sees as key gaps in industry’s ability to build ride-sharing networks of electric vertical-takeoff-and-landing (eVTOL) air taxis within cities, including noise, batteries, airspace and infrastructure.

At its second Elevate Summit in Los Angeles on May 8-9, Uber is assembling the entire urban air mobility (UAM) ecosystem and unveiling models and tools it is developing to help industry design new classes of aircraft with which it has no experience.

“Manufacturers know how to produce aircraft, but none have developed an eVTOL for urban air mobility,” says Rob McDonald, Uber’s head of vehicle engineering. “We look for gaps in technology, tools and testing and spend money to fill those gaps and share the results with our partners.”

Taking a leaf out of NASA’s book, Uber is developing distributed-propulsion eVTOL common reference models (eCRM) that industry can use to develop and validate designs. The company is releasing its first eVTOL concepts to industry at the summit, with more to come.

The first, eCRM-001, has four sets of paired rotors for vertical lift and tilting wingtip propellers for vertical lift and forward thrust. Another concept, eCRM-003, has four sets of rotors for vertical flight and a tail-mounted propeller for cruise flight.

NASA uses the CRM to enable different teams to work on the same hard problem—the design of a high-lift system for commercial aircraft—and share their results. Uber sees five uses for its eCRMs, says former NASA engineer Mark Moore, director of aviation engineering.

“All these vehicles have complex flow problems, where propulsion, aerodynamics and control interact, and acoustic issues,” he says. “This requires variable-fidelity toolsets that need to be validated and compared, similar to what NASA does with the high-lift CRM.”

Secondly, eCRMs act as reference concepts for trade studies as developers look across many different configurations. Uber’s models also are intended to help socialize new ideas, “like concept cars that automotive manufacturers never intend to build but use to get ideas across to stakeholders,” Moore says.

A fourth function is to validate that the requirements Uber has developed are correct. “We have developed an extensive requirement set, and the eCRMs help validate that the requirements are correct and show they are achievable,” says Moore.

Fifth, the common reference models will advance eVTOL by allowing developers to understand if technologies buy their way onto different vehicle concepts. “It is not about any one vehicle,” he says. “It is about understanding a bunch of vehicles that are so different.”

The eCRMs will help industry make the tradeoffs between the complexity of articulation and the redundancy of distributed propulsion. “Those are the big questions in eVTOL, and we are making a tremendous effort in those two directions,” says Moore.

The eCRMs are being developed internally by Uber’s vehicle team located in San Luis Obispo and San Francisco, California, to support its partners as they develop their vehicles. Partners onboard to date are Aurora Flight Sciences, Bell, Embraer and Pipstrel Aircraft. More partners will be announced at the summit.

The first eCRMs are representative of the broadest sets of eVTOL configurations with the potential to meet Uber’s requirements: designs that use separate propulsion systems for lift and cruise and those that articulate—tilting wings, rotors or ducts—to transition between vertical and forward flight.

They are not entirely generic and feature technologies Uber intends to investigate with its partners. These include the stacked corotating rotor—a lift rotor with dual propellers that rotate in the same direction. This avoids the wake interference problem that makes contrarotating rotors loud, says Moore.

The blade pairs are not at 90 deg., but are spaced just 10 deg. apart. This has two beneficial effects. One is that the blade pairs act like a high-lift flap on a wing and increase performance. The second is that nonuniform blade spacing produces a different and quieter acoustic signature.

The two propellers in each pair are driven independently, which provides redundancy, and digital control allows precise management of the phase between the rotors to minimize noise, says McDonald.

Uber also is investigating how to address gaps in the design tools available to its partners. This includes developing toolsets that enable acoustics to be brought into conceptual design. “Low noise is usually brought in late in the design process; it’s one of the last things to be considered,” McDonald says.

“The acoustic community has spent decades developing tools appropriate for late in the design process. They are high-fidelity and rigid and not suitable for the early, creative design process,” he says.

Urban air mobility will be a nonstarter if the public decides the vehicles are too noisy. Uber does not believe the existing tools are sufficient to meet its aggressive noise goals—which essentially are to blend into the background noise around vertiports in a busy city.

“We are very focused on being able to design for ultra-low community noise. That is the differentiator [for eVTOLs over helicopters] in this market. And the industry has not done that before,” Moore says. “So we’ve focused on developing low-fidelity tools that can be used up front in conceptual design.”

These tools are dedicated to the design of the partners’ vehicles, which cannot be shown, and the eCRMs are a way to showcase the results without giving away proprietary designs. This is part of Uber’s strategy to share information as widely as possible to advance the art of eVTOL design across industry.

Already, M4 Aerospace Engineering has applied Uber’s eCRMs to developing weight-prediction methods for some of the most unique features of eVTOLs. Georgia Tech has used these concepts to perform analyses to compare and contrast the safety of different concept approaches.

Uber and Empirical Systems Aerospace are developing a physics-based modeling and assessment tool to evaluate eVTOL performance and controllability during transition between hover and cruise. The tool will help Uber and partners better understand new configurations through static and dynamic vehicle flight modeling.

Most of Uber’s effort involves taking existing design tools and streamlining and automating the connections between them so they can be used more easily in the early stages. This encompasses connecting vehicle geometry to unsteady aerodynamic modeling to acoustic propagation and post-processing tools that simulate how sounds are perceived by humans.

Uber is funding research on developing vortex particle code for unsteady aerodynamics and better metrics to measure the annoyance caused by vehicles that have acoustic signatures quite different to those of conventional helicopters.