Fast-Forwarding to a Future of On-Demand Urban Air Transportation
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Posted by Jeff Holden, Chief Product Officer
Imagine traveling from San Francisco’s Marina to work in downtown San Jose — a drive that would normally occupy the better part of two hours — in only 15 minutes. What if you could save nearly four hours round-trip between São Paulo’s city center and the suburbs in Campinas? Or imagine reducing your 90-plus minute stop-and-go commute from Gurgaon to your office in central New Delhi to a mere six minutes.
Every day, millions of hours are wasted on the road worldwide. Last year, the average San Francisco resident spent 230 hours commuting between work and home—that’s half a million hours of productivity lost every single day. In Los Angeles and Sydney, residents spend seven whole working weeks each year commuting, two of which are wasted unproductively stuck in gridlock. In many global megacities, the problem is more severe: the average commute in Mumbai exceeds a staggering 90 minutes. For all of us, that’s less time with family, less time at work growing our economies, more money spent on fuel — and a marked increase in our stress levels: a study in the American Journal of Preventative Medicine, for example, found that those who commute more than 10 miles were at increased odds of elevated blood pressure.
On-demand aviation has the potential to radically improve urban mobility, giving people back time lost in their daily commutes. Uber is close to the commute pain that citizens in cities around the world feel. We view helping to solve this problem as core to our mission and our commitment to our rider base. Just as skyscrapers allowed cities to use limited land more efficiently, urban air transportation will use three-dimensional airspace to alleviate transportation congestion on the ground. A network of small, electric aircraft that take off and land vertically (called VTOL aircraft for Vertical Take-off and Landing, and pronounced vee-tol), will enable rapid, reliable transportation between suburbs and cities and, ultimately, within cities.
The development of infrastructure to support an urban VTOL network will likely have significant cost advantages over heavy-infrastructure approaches such as roads, rail, bridges and tunnels. It has been proposed that the repurposed tops of parking garages, existing helipads, and even unused land surrounding highway interchanges could form the basis of an extensive, distributed network of “vertiports” (VTOL hubs with multiple takeoff and landing pads, as well as charging infrastructure) or single-aircraft “vertistops” (a single VTOL pad with minimal infrastructure). As costs for traditional infrastructure options continue to increase, the lower cost and increased flexibility provided by these new approaches may provide compelling options for cities and states around the world.
Furthermore, VTOLs do not need to follow fixed routes. Trains, buses, and cars all funnel people from A to B along a limited number of dedicated routes, exposing travelers to serious delays in the event of a single interruption. VTOLs, by contrast, can travel toward their destination independently of any specific path, making route-based congestion less prevalent.
Recently, technology advances have made it practical to build this new class of VTOL aircraft. Over a dozen companies, with as many different design approaches, are passionately working to make VTOLs a reality. The closest equivalent technology in use today is the helicopter, but helicopters are too noisy, inefficient, polluting, and expensive for mass-scale use. VTOL aircraft will make use of electric propulsion so they have zero operational emissions and will likely be quiet enough to operate in cities without disturbing the neighbors. At flying altitude, noise from advanced electric vehicles will be barely audible. Even during take-off and landing, the noise will be comparable to existing background noise. These VTOL designs will also be markedly safer than today’s helicopters because VTOLs will not need to be dependent on any single part to stay airborne and will ultimately use autonomy technology to significantly reduce operator error.
We expect that daily long-distance commutes in heavily congested urban and suburban areas and routes under-served by existing infrastructure will be the first use cases for urban VTOLs. This is due to two factors. First, the amount of time and money saved increases with the trip length, so VTOLs will have greatest appeal for those traveling longer distances and durations. Second, even though building a high density of landing site infrastructure in urban cores (e.g. on rooftops and parking structures) will take some time, a small number of vertiports could absorb a large share of demand from long-distance commuters since the “last mile” ground transportation component will be small relative to the much longer commute distance.
We also believe that in the long-term, VTOLs will be an affordable form of daily transportation for the masses, even less expensive than owning a car. Normally, people think of flying as an expensive and infrequent form of travel, but that is largely due to the low production volume manufacturing of today’s aircraft. Even though small aircraft and helicopters are of similar size, weight, and complexity to a car, they cost about 20 times more.
Ultimately, if VTOLs can serve the on-demand urban transit case well — quiet, fast, clean, efficient, and safe — there is a path to high production volume manufacturing (at least thousands of a specific model type built per year) which will enable VTOLs to achieve a dramatically lower per-vehicle cost. The economics of manufacturing VTOLs will become more akin to automobiles than aircraft. Initially, of course, VTOL vehicles are likely to be very expensive, but because the ridesharing model amortizes the vehicle cost efficiently over paid trips, the high cost should not end up being prohibitive to getting started. And once the ridesharing service commences, a positive feedback loop should ensue that ultimately reduces costs and thus prices for all users, i.e. as the total number of users increases, the utilization of the aircraft increases. Logically, this continues with the pooling of trips to achieve higher load factors, and the lower price feeds back to drive more demand. This increases the volume of aircraft required, which in turn drives manufacturing costs down. Except for the manufacturing learning curve improvements (which aren’t relevant to ridesharing being applied to automobiles), this is very much the pattern exhibited during Uber’s growth in ground transportation, fueled by the transition from the higher-cost UberBLACK product to the lower-cost and therefore more utilized uberX and uberPOOL products.
Market Feasibility Barriers
The vision portrayed above is ambitious, but we believe it is achievable in the coming decade if all the key actors in the VTOL ecosystem — regulators, vehicle designers, communities, cities, and network operators — collaborate effectively. The following are what we perceive as the most critical challenges to address in order to bring on-demand urban air transportation to market.
● The Certification Process. Before VTOLs can operate in any country, they will need to comply with regulations from aviation authorities — namely the US Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA) who regulate 50% and 30% of the world’s aviation activity, respectively — charged with assuring aviation safety. VTOL aircraft are new from a certification standpoint, and progress with certification of new aircraft concepts has historically been very slow, though the process is changing in a way that could accelerate things significantly. We explore this topic in depth in the Vehicle: Certification section.
● Battery Technology. Electric propulsion has many desirable characteristics that make it the preferable propulsion choice for the VTOL aircraft contemplated in this document, and electric batteries are the obvious energy source. That said, the specific energy (the amount of energy per unit weight provided by the battery, which ultimately determines the gross weight of the vehicle) of batteries today is insufficient for long-range commutes. Additionally, the charge rate (how quickly the battery can be brought back to a nearly full charge, which determines operational idle time) of batteries today is also too slow to support high-frequency ridesharing operations. Cycle life (the number of charge/discharge cycles the cell can sustain before its capacity is less than 80% of the original, which determines how often the battery must be replaced) and cost per kilowatt-hour (which determines the overall battery cost) are also important to the economic viability of electric aircraft. We discuss the current state of the art battery developments, as well as promising (required) advances that are likely to occur in the coming several years in the Vehicle Performance: Speed and Range section.
● Vehicle Efficiency. Helicopters are the closest current-day proxy for the VTOLs discussed in this paper, but they are far too energy inefficient to be economically viable for large-scale operations. Helicopters are designed for highly flexible operations requiring vertical flight. With a more constrained use case focused on ridesharing, a more mission-optimized vehicle is possible, e.g utilizing distributed electric propulsion (DEP) technology. Large efficiency improvements are possible because DEP enables fixed-wing VTOL aircraft that avoid the fundamental limitations of helicopter edgewise rotor flight, and wings provide lift with far greater efficiency than rotors. But no vehicle manufacturer to date has yet demonstrated a commercially viable aircraft featuring DEP, so there is real risk here. We cover this topic in the Economics: Vehicle Efficiency/Energy Use section.
● Vehicle Performance and Reliability. Saving time is a key aspect of the VTOL value proposition. In the ridesharing use case, we measure and minimize the comprehensive time elapsed between request and drop-off. This is affected by both vehicle performance, particularly cruise speed and take-off and landing time, and system reliability, which can be measured as time from request until pick-up. In this context, key problems to solve are vehicle designs for 150–200 mph cruise speeds and maximum one-minute take-offs and landings, as well as issues like robustness in varied weather conditions, which can otherwise ground a large percentage of a fleet in an area at arbitrary times. The Infrastructure and Operations section and the Operations: Trip Reliability and Weather sections address the challenges and compelling technology advances in these areas.
● Air Traffic Control (ATC). Urban airspace is actually open for business today, and with ATC systems exactly as they are, a VTOL service could be launched and even scaled to possibly hundreds of vehicles. São Paulo, for example, already flies hundreds of helicopters per day. Under visual flight rules (VFR), pilots can fly independent of the ATC and when necessary, they can fly under instrument flight rules (IFR) leveraging existing ATC systems. A successful, optimized on-demand urban VTOL operation, however, will necessitate a significantly higher frequency and airspace density of vehicles operating over metropolitan areas simultaneously. In order to handle this exponential increase in complexity, new ATC systems will be needed. We envision low-altitude operations being managed through a server request-like system that can deconflict the global traffic, while allowing UAVs and VTOLs to self-separate any potential local conflicts with VFR-like rules, even in inclement weather. There are promising initiatives underway, but they will play out over many years and their pace may ultimately bottleneck growth. The Operations: Air Traffic section expands on the issues here and summarizes current ATC initiatives.
● Cost and Affordability. As mentioned above, helicopters are the closest proxy to the VTOLs contemplated in this paper, but they are prohibitively expensive to operate as part of a large-scale transportation service. They are energy-inefficient and very expensive to maintain, and their high level of noise strongly limits use in urban areas. Demand is accordingly modest for helicopters, and this translates to low manufacturing volumes: current global civil rotorcraft production is only approximately 1,000 units per year, lacking critical economies of scale. Simpler, quieter and more operationally efficient vehicle designs are proposed which leverage digital control rather than mechanical complexity. We expect that this shift can kickstart the virtuous cycle of cost and price reduction described earlier. Our Vehicle and Economic Model section goes into detail concerning the evolutionary pathway to a mass market through affordable vehicles and operations.
● Safety. We believe VTOL aircraft need to be safer than driving a car on a fatalities-per-passenger-mile basis. Federal Aviation Regulation (FAR) Part 135 operations (for commuter and on-demand flights), on average, have twice the fatality rate of privately operated cars, but we believe this rate can be lowered for VTOL aircraft at least to one-fourth of the average Part 135 rate, making VTOLs twice as safe as driving. DEP and partial autonomy (pilot augmentation) are key pieces of the safety equation, discussed in further detail in the Vehicle: Safety section.
● Aircraft Noise. For urban air transportation to thrive, the vehicles must be acceptable to communities, and vehicle noise plays a significant role. The objective is to achieve low enough noise levels that the vehicles can effectively blend into background noise; ultimately we believe VTOLs should be one-half as loud as a medium-sized truck passing a house. That said, a more sophisticated measure of “noise” is required in order to properly characterize the impact of vehicle sound on a community. Electric propulsion will be critical for this objective, as well: it enables ultra-quiet designs, both in terms of engine noise and propulsor thrust noise. The Vehicle: Noise section addresses this issue.
● Emissions. VTOLs represent a potential new mass-scale form of urban transportation; as such, they should clearly be ecologically responsible and sustainable. When considering helicopters as the starting point, there is a substantial opportunity to reduce emissions. We consider both the operational emissions of the vehicle, i.e. emissions produced by the vehicle during its operation, and lifecycle emissions, which accounts for the entire energy lifecycle associated with the transportation method, including (in the case of electric vehicles) the production of electricity to charge VTOL batteries. Among the advantages of electric propulsion designs is that they have zero operational emissions. This leaves energy generation (which today is still largely coal, natural gas and petroleum-based) with its associated emissions as the primary concern. This topic is covered in the Vehicle: Emissions section.
● Vertiport/Vertistop Infrastructure in Cities. The greatest operational barrier to deploying a VTOL fleet in cities is a lack of sufficient locations to place landing pads. Even if VTOLs were certified to fly today, cities simply don’t have the necessary takeoff and landing sites for the vehicles to operate at fleet scale. A small number of cities already have multiple heliports and might have enough capacity to offer a limited initial VTOL service, provided these are in the right locations, readily accessible from street level, and have space available to add charging stations. But if VTOLs are going to achieve close to their full potential, infrastructure will need to be added. The Infrastructure and Operations section goes into this issue more deeply and provides the results of a simulation to determine optimal vertistop/vertiport placement.
● Pilot Training. Training to become a commercial pilot under FAR Part 135 is a very time-intensive proposition, requiring 500 hours of pilot-in-command experience for VFR and 1200 hours for IFR. As on-demand VTOL service scales, the need for pilots will rapidly increase, and it’s likely that with these training requirements, a shortage in qualified pilots will curtail growth significantly. In theory, pilot augmentation technology will significantly reduce pilot skill requirements, and this could lead to a commensurate reduction in training time. See the Vehicle: Pilot Training section for more on this.
Industry Assessment of Market Feasibility Barriers
NASA and the FAA recently spearheaded a series of On-Demand Mobility (ODM) workshops to bring the VTOL ecosystem together — emerging VTOL vehicle manufacturers, federal agencies, private investors, professional societies, universities, and international aviation organizations — to identify barriers to launching an on-demand VTOL service. The barriers identified by the ODM workshops group (in the below diagram) align quite well with the challenges identified in our foregoing assessment.
The remainder of our paper delves into these challenges for achieving a successful VTOL market, with an eye to surmounting them as quickly as possible, as well as our view on rider experience requirements. Our intent here is to contribute to the nascent but growing VTOL ecosystem and to start to play whatever role is most helpful to accelerate this industry’s development. Rather than manufacture VTOL hardware ourselves, we instead look to collaborate with vehicle developers, regulators, city and national governments, and other community stakeholders, while bringing to the table a very fertile market of excited consumers and a clear vehicle and operations use case. At the end of the paper, we introduce an upcoming summit for vehicle developer entrepreneurs, regulators and cities, which we hope will help advance discussions and collaboration to bring on-demand urban air transportation to life.
We welcome all feedback at firstname.lastname@example.org.
 For example, the UK’s proposed High Speed 2 railway would cost taxpayers £27B ($33B) over nine years for a single straight-line route between London and Birmingham — that’s nearly $280M/mile, a projection that continues to increase (source). This is just one example project; our point is that new technology can create options for transportation infrastructure that are far lower cost.
 “Operational emissions” refers to the emissions from the vehicle during operation, which is only a portion of the full life-cycle emissions. There is great value in achieving zero operational emissions: see the Vehicle: Emissions section for a deeper discussion on this topic.
 Not only are aircraft and helicopters dramatically more expensive than cars, but also the components going into the vehicles. The 430-horsepower Corvette LS3 6.2 liter crate complete engine has a MSRP of $7911 from GM. yet is far more complex than an aircraft engine, such as the Continental IO-550C 300 hp engine which has a MSRP of $46,585. See the Economics section for more details.
 Our economic modeling shows that these performance numbers are necessary for feasible long distance commuteVTOL service. Shorter trip distances could utilize slower vehicles, with a penalty of having lower vehicle productivity.
 Current helicopters have a myriad of parts that are single fault flight critical components which require tight oversight on part production quality as well as frequent maintenance checks of individual components for wear and tolerance due to the harsh, high vibration operating environment.