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.
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.
Uber believes 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
Market Feasibility Barriers
The Uber flying taxi vision is ambitious, but they 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 longrange 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. They 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.
They envision lowaltitude 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.
affordable vehicles and operations.
● Safety. We believe VTOL aircraft need to be safer than driving a car on a fatalities-perpassenger-mile basis. Federal Aviation Regulation (FAR) Part 135 operations (for commuter and on-demand flights 12 ), 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 13 ) 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.
Speed and Range
VTOL ridesharing networks will eventually need to have a variety of vehicle types, just as automobile ridesharing services offer customers today. VTOLs will likely be developed across a number of different speed and range capabilities. A VTOL optimized for shorter trips (less than 50 miles) won’t require as much speed as a VTOL capable of meeting the needs of longer distance commuters, such as those identified in the U.S. Census Mega Commuter and New York University Super Commuter studies with typical travel distances of 100 miles or more daily. Super Commuters are growing at a rapid pace in the U.S., with more than 600,000 commuters matching this description.
Studies suggest that 150-200 mph is where DEP becomes most efficient.
An upper limit (in the US) is the FAA speed limit of 287 mph for flight operations at lower than 10,000 feet. In certain sensitive geographic locations, the FAA has decreased this maximum speed to 230 mph (i.e., Washington D.C). Balancing the higher efficiency of lower speed with the desire to achieve high vehicle productivity to amortize costs across more miles of travel will likely yield a compromise of a desirable VTOL vehicle speed between 150 and 230 mph. Few helicopters are capable of flying at these high speeds and are unable to do so with reasonable efficiency.
According to the US Census Bureau, 123M of America’s 143M workers (86%) commuted to work in 2013 via private vehicle; 89% of those drove alone. Of these, 18.9M (15.0%) had a commute exceeding 30 miles and 7.9M (6%) longer than 60 minutes - this includes 27.4% of all D.C. workers, the highest of any state.
Although urban commute distances are typically 8.5 miles each way according to the U.S. Census, this is unlikely to be a good early use case due to the dense support infrastructure that would be required. Mega Commuters (within the same metropolitan area) have average daily commutes of 93 miles each way. While these longer trips need much less infrastructure, they would require vehicles that are cruise efficient, or that employ some sort of hydrocarbon based range extender (to compensate for relatively low battery specific energy), to be able to do more than a single trip on current battery energy storage solutions.
Current commuting practices suggest that a minimal effective VTOL range in the near-term is to conduct two 50 mile trips at maximum speed, with sufficient energy for two takeoffs and landings, while meeting the FAA Instrument Flight Rules (IFR) 30 minute reserves (plus flight to an alternate location).
Uber analysis says the design mission range can likely be met within the next 5 years—this means embracing VTOL designs that can achieve cruise aerodynamic efficiencies with a Lift/Drag ratio of greater than 10 (with 12 to 17 desirable) and battery cell specific energy of 400 Wh/kg55. Electric VTOLs will likely use large battery packs, nominally a 140 kWh pack for a 4 person aircraft. Use of a large battery pack ensures the specific power of the batteries is well matched to achieving high specific energy. Nominally, battery packs that can discharge at less than 3C ratings are able to avoid severe penalties to the specific energy. High vehicle utilization requires the ability to perform more than one average trip distance prior to requiring recharge, which further supports the use of a larger battery pack. Essentially this is similar to the way that Tesla designs electric cars versus others, with larger battery packs and improved specific energy due to the limited discharge rates.
Major investments are being made in batteries since so many products value higher specific energy (i.e., laptops, smart phones, cars, etc.), with many new chemistry approaches being tested. Particularly exciting are recent Department of Energy (DOE) investments which align so well with VTOL priorities. The DOE Battery 500 project is spending $50 million over the next 5 years to develop 500 Wh/kg batteries along with high capacity 350 kW chargers. This collaboration between DOE labs and universities is focusing on lithium-metal batteries, overseen by an industry panel board including Tesla, IBM, and PNNL to ensure manufacturable solutions. While this effort is pursuing a 1,000 cycle life, it’s also pursuing a cost target of less than $100 per kWh. If this cost threshold can be achieved, the cycle life would be highly acceptable. Sony is aiming to commercialize 400 Wh/kg Li-S battery packs by 2020. Equally exciting are the high energy chargers which would be capable of recharging in as little as 10 minutes. Additional research into pulse chargers is already showing improved cycle life and maintaining improved maximum charge capacity over time. Achieving rapid charging for large battery packs is as important, if not more important than achieving high specific energy batteries.
Pilots, ground based operators and then robotic flight
Ground-based operators—just like the pilots who will initially fly these VTOLs—will need to be trained and licensed. As part of certification of a new vehicle, manufacturers will need to define ways an operator can monitor vehicle airworthiness and its ability to make flight safety decisions remotely. This move to remote piloting will likely need close coordination with the FAA Unmanned Aircraft Systems efforts as they address similar issues with large drones in civilian airspace.
Making it happen
The first 25 vertiports that Uber chooses capture 60% of all long-distance trips in Los Angeles and 35% in London.
After a savings threshold of 70% and 75% in London and Los Angeles, respectively, no time-saving VTOL trips were possible. This makes sense intuitively because average driving speed directly between two vertiport/stops would be at least 40 mph as compared to a VTOL at 170 mph (assumption for this analysis) so the savings for any given VTOL itinerary asymptotes near 70-75%
VTOL will provide the greatest time savings for lengthier trips; as such, a city with greater spread between commute endpoints may exhibit more latent demand for urban flight alternatives to their automobile commutes.
Uber VTOL assumption includes:
● Capacity: 4-place capacity (including pilot, if there is one)
● Load Factor: Pooling match rates will allow for an average of 67% of revenue producing seats to be filled by a paying passenger
● Gross Vehicle Weight: 4,000 lb
● Batteries: 400 Wh/kg specific energy batteries at the pack level with 2,000 cycle life,
● Power: 500 kW short-term takeoff power with 1 minute of full power at takeoff and landing,
○ 71 kW power required at 150 mph cruise, 120 kW required at 200 mph,
● Utilization: 2,080 hours of annual utilization
● Electricity Cost: $.12 per kWh electricity cost
Uber believes there is a path to making VTOLs economically favorable to private vehicle ownership and a viable alternative to ridesharing on the ground, so long as VTOL customers are willing to trade off some cost and/or privacy for large gains in speed. They expect an initial carpooled VTOL product will be priced similarly to uberX today, and as ridesharing prices on the ground decline with advancements in self-driving technology, our analysis indicates that VTOL pricing will decrease even more steeply. Ultimately, an uberX on the ground will have a similar price to an uberPOOL in the air; a VTOL uberX would be more expensive due to lower load factor. With this, they offer urban air commuters a value proposition that hits the privacy/speed/cost curve in a similar way that uberX and uberPOOL do for our car service today.
Uber plans to convene a global Elevate Summit to bring together a wide set of vehicle manufacturers, regulatory bodies and public and private sector city stakeholders. They will do so with the intent of exploring the issues and solutions that are raised during our outreach and to surface joint, shared perspectives as well as solutions that can help to accelerate urban air transportation becoming a reality. We view this event as an
excellent opportunity for cross-pollination of ideas and networking with a view toward creating lasting working relationships that best serve the future of urban mobility. they are planning for this to occur in early-2017 and will be extending invitations in the near future.