WorldWide eVTOL

Technology Roadmap Sections and Deliverables

• 2EVL Eletric Vertical take off and Landing

This indicates that we are dealing with a “level 2” roadmap at the product level (see Fig. 8-5), where “level 1” is a market level roadmap 1LUM (Low emissions Urban air Mobility)and “level 3” or “level 4” would indicate the specific technologies like vectored thrust, autonomous flight, electric propulsion etc.

Roadmap Overview

Enter description of the technology here:

eVTOLS (electric Vehicle Take Off and Landing) are airborne vehicles that use electric vectored thrust to take off vertically and transition from vertical thrust to horizontal thrust, thus making it flexible and efficient for Urban air commute. <ref>https://en.wikipedia.org/wiki/EVTOL</ref> The vectored thrust eVTOLs have a wing for an efficient cruise and use the same propulsion system for both hover and cruise. They are conceptually simple but difficult and risky to control. The tail-sitters rotate the entire aircraft. They are conceptually simple but difficult and risky to control. The Harrier configuration is called vectored thrust because it can orientate mechanically the direction of the thrust. The tilt-wings rotate the entire wing, the engines and the propellers as a single piece. Rotating the wing in hover avoids the impinging of the propeller slipstream on it, a problem that reduces the thrust in the hover of tiltrotors. The lift produced by the wing is augmented, at high angles of attack, by the blowing effect of the propellers. Autonomous eVTOLs are more versatile and can be efficiently used to transport passengers and cargo without any human intervention yet are often available as optionally pilotable. <ref>Electric VTOL Configurations Comparison by Alessandro Bacchini</ref>

<ref>Lilliumjet, architecture design principles</ref>

Design Structure Matrix (DSM) Allocation

The 2-EVL tree that we can extract from the DSM above shows us that the eVTOL (2EVL) is a solution to larger more fuel efficient methods of urban mobility (1LUM), and requires the following major subsystems: 3INT Interior, 3LHI Landing and Handling Infrastructure, 3EGM Energy Management, 3POP Propulsion, and 3NAV Navigation. These require the following level four component technologies: 4BAT Battery, 4CHG Charging Station, 4ELM Electric Motor, 4FAN Fan or Propeller, 4SEN Sensors, 4APT Auto-pilot and 4FCP Flight Computer.

Roadmap Model using OPM

We provide an Object-Process-Diagram (OPD) of the 2EVL roadmap in the figure below. This diagram captures the main object of the roadmap (eVTOL), its various instances including main competitors, its decomposition into subsystems (wing, flight-control, autonomous control, electric propulsion), its characterization by Figures of Merit (FOMs) as well as the main processes (hovering, wing tilt).

An Object-Process-Language (OPL) description of the roadmap scope is auto-generated and given below. It reflects the same content as the previous figure, but in a formal natural language.

Figures of Merit

The table below show a list of FOMs by which electric VTOL can be assessed. The first two and the last two are used to assess the aircraft itself. They are very similar to the FOMs that are used to compare traditional aircraft which are propelled by fossil fuels, the big difference being that 2EVL is essentially emissions free during flight operations. The other rows represent subordinated FOMs which impact the performance and cost of eVTOL but are provided as outputs (primary FOMs) from lower level roadmaps at level 3 or level 4, see the DSM above.

<ref>Back to the Future: A rough comparison of 70s VTOL concepts to current eVTOL designs - Mykhaylo Filipenko</ref>

Alignment with Company Strategic Drivers

Strategic drivers for the company:

Number	Strategic Drivers	Alignment targets
1	To develop hover and cruise configurations to lower the net cost to the passenger for intercity flights in a limited service radius. The design of the eVTOL itself should enable reduced CAPEX costs and OPEX costs for a flight over a limited radius. The current air transportation modes either result in high CAPEX (Airports) or high OPEX (Helicopters, multirotors) that drive the cost up.	This roadmap will target the technology selection that would address the need for high hover efficiency for take-off and landing and high cruise efficiency for covering higher distances. The state of the art technology of tilt rotors and tilt wing aircrafts seem to enable the use of a common propulsion system for hover and cruise, leveraging the best of both aircrafts and rotorcraft(conventional). This roadmap evaluates various configurations of eVTOLs and this driver is aligned with this roadmap.
2	To target higher PAX capacities while keeping a balance with a decent range to enable cost effective transportation to surrounding cities, making the hub & spoke transportation model a reality. Efficient propulsion systems would increase the efficiency of the eVTOL creating room for more passengers or higher ranges.	The development of the Li-ion batteries with higher energy density is crucial to increased payload capacity of eVTOLs. THe Li-ion energy density has tripled since 2010 to 300Wh/Kg. To achieve a long range flight, a target of 500Wh/Kg is expected by 2025. The weight of the eVTOL itself plays a major role in this. Use of lighter materials like aluminum and carbon fiber are expected for the construction of the eVTOL. This driver is in alignment of the 2EVL roadmap
3	To develop low noise hover systems with lower disc loading in order to allow for the eVTOL to take off from various landing ports in urban areas. THe reduced noise and disc loading will enable the construction of compact landing pads in buildings or courtyard without disrupting normal urban life.	The discloading of the aircraft severely impacts the noise level generated by the hover. The harrier jet generates 125 dB of noise when hovering at 100ft, whereas helicopters generate 108 dB at ground level. Reduction of these to 78 dB is required in order to achieve the desirable noise level. This driver is currently not aligned with the eVTOLs.

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Positioning of Company vs. Competition

The table below contains publicly available high level specification data for the key e-VTOL aircraft designs currently in the R&D, prototyping or production technology developmental phases.

• 

  Volocopter 2x

• 

  E-Hang

• 

  Lilium Jet

• 

  Vahana

• 

  Cora

• 

  Aurora eVTOL

• 

  Rolls Royce eVTOL

• 

  NeoXcraft

• 

  Joby Generation 1

• 

  Nexus

• 

  Alakai Skai

• 

  Hyundai eVTOL

It is worth noting here that this table contains data for a variety of e-VTOL flight configurations. Each configuration has its pros and cons and the industry has not yet converged to an optimal configuration yet. Multicopter aircraft are typically designed to serve short-haul intra-city demand whilst tilt-wing, tilt-rotor and lift+push configurations achieve efficiency in cruise flight and therefore typically serve inter-city demand. Not all of these aircraft are in at the prototyping or production stages; some still remain conceptual. Performance specifications from such designs are subject to change in the future.

This figure highlights the trade-off that exists between flight range [km] and max payload capacity [kg] and presence of a pareto front that pushes to the top right of the chart. With e-VTOLs first making headlines in 2010 with the e-Hang announcement, players have adopted different methods to move closer to the utopia point. This chart is somewhat skewed by Alakai Technologies' Alakai Skai and Rolls Royce's e-VTOL aircraft. Both are still conceptual designs with to-market strategies in the late 2020's and early 2030's. Both promise exceptional range and PAX capacity with substantially larger aircraft airframes than what is currently seen on the market today. Alakai Skai is also unique in that it is the only e-VTOL with a hydrogen-powered fuel plant, a technology that underpins their bullish performance metrics.

Both Volocopter and e-Hang are focused on the intra-city short-haul transportation market whilst players such as Lilium and Joby are more focused on inter-city operations. In the early 2010's, we see a focus on range over PAX capacity in an effort to dissolve doubts around operational feasibility. With that said, more recent e-VTOL designs sport large PAX capacities for similar or more range, signaling a shift from technological development and R&D focused on core performance parameters such as range to more operational considerations such as PAX capacity. This industry has not yet seen any notable consolidation efforts in part because it remains a nascent industry without any realized demand. With that said, as certification processes begin to hinder to-market strategies, consolidation may occur between players with compatible technology or operational synergies. Furthermore, whilst the market is crowded with feasible e-VTOL designs, competition is not necessarily fully realized in as the industry grows as players will likely benefit from co-existence. We can expect to see synergies between direct competitors with regards to certification processes, driving customer and public acceptance and any infrastructure-related investment that is required at the industry level.

Key Patents and Publications

Patents

• Karem Aircraft: EVTOL Aircraft Using Large, Variable Speed Tilt Rotors

This patent, US 10,351,235, covers a specific eVTOL architecture consisting of four electrically driven rotors, and a horizontal wing-tail configuration. The aircraft is described to have a payload of 500-1300 lbs, and the range is not specified. This aircraft concept achieves vertical flight through articulating “tilt-rotors” on each of the four rotors in the concept. During vertical flight, they are all operating in the horizontal plane, providing vertical thrust for vertical take-off and landing. The aircraft has a long major wing, and a smaller tailplane behind it, each with two of the motor-propeller assemblies. In translational flight, the aircraft relies on the wing for lift, and the motors are responsible only for producing thrust. The rear rotors are on the ends of the horizontal tailplane, while the main rotors are near the end, with a wing extension protruding beyond.

Karem Aircraft eVTOL Patent Image

• Joby Aviation: Aerodynamically Efficient Lightweight Vertical Takeoff and Landing Aircraft with Pivoting Rotors and Stowing Rotor Blades

US patent 20160031555A1 by Joby Aviation covers three different concepts of tiltrotor aircraft, each of which rely on pivoted electric rotor assemblies for vertical thrust, and on wings for lift in horizontal flight. One of the key features of this aircraft concept is the forward-swept wing with either three or four electric rotors on each side. This is due to mass balancing, and wing spar placement considerations. Additionally, the patent covers Joby’s plan to have rotors that can articulate and nest within the nacelle during forward flight. Because the rotors have to provide all of the lift in vertical flight, the rotor system is sized for this condition, not for the thrust needed in horizontal flight. By stowing the motors when they aren't needed, significant aerodynamic gains can be achieved. Lastly the rotor assemblies are able to pivot with respect to the engine nacelles due to a design shown in detail in the patent. The actuator-driven pivoting of the motor/propeller assembly can potentially simplify the architecture, as the surrounding wing structure does not have to accommodate a pivoting nacelle.

Joby Aviation eVTOL Concept

• Opener: Electrically Powered Aerial Vehicles and Flight Control Methods

US Patent 9,346,542 by Opener describes the core technology and configuration for their Blackfly eVTOL aircraft technology. The overall layout of this aircraft is two straight wings that are located in the front and back of the aircraft and are vertically staggered from each other. Each wing has four motor-propeller rotor assemblies which are powered from a central battery. Currently, the Blackfly technology is only a single-seat aircraft and the patent describes it as such. Each wing assembly with embedded rotors rotates about its own axis to provide thrust for both vertical and horizontal flight. Additionally, this design has no control surfaces. The control and navigation of this concept is controlled by modulating the thrust provided to each independent rotor assembly. Through this differential thrust, the aircraft is able to pitch, roll and yaw, along with possessing control capabilities while hovering. The patent also covers a detailed energy and information flow diagram that shows how both power and control information are provided to each motor assembly. This patent does not cover the mechanics of the wing assemblies, their rotation, or any mention of the intended uses of the aircraft. Overall this patent concisely describes the single-person aircraft from a high level, but does not mention any specifics about some of the mechanical challenges that this design possesses.