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Answering the question: Do eVTOL air taxis have a place in sustainable cities?

By Rex Alexander

Published on: April 1, 2020
Estimated reading time 15 minutes, 36 seconds.

Vertical Flight Society infrastructure advisor Rex Alexander takes a deeper dive into issues surrounding air taxi infrastructure and sustainable cities.

In an opinion piece published March 16, Peter Powell posed the question, “Do eVTOL air taxis have a place in sustainable cities?” My answer to this is: “Yes — but only if done correctly.”

Uber air taxi vertiport
A vertiport concept developed for Uber by Humphreys & Partners. The exact forms that infrastructure for eVTOL air taxis will take in the future have yet to be determined. Uber Image

The number of theories regarding the feasibility of urban air mobility (UAM) are rivaled only by the number of related aircraft concepts, which is now in excess of 250. In this ambitious journey we are setting out on, there are tens of thousands of steps we must take before we see this transportation model reach its full potential. Figuratively speaking, we have barely left our own neighborhood.

In this article, I’ll take a deeper dive into some of the issues raised by Powell with respect to vertiports and the structures that will accommodate these new types of aircraft. Just as is the case for heliports today, there will never be a “one size fits all” vertiport design. Each location comes with its own idiosyncrasies that must be taken into account when assessing whether a proposed vertiport has the potential for success or is doomed for failure. Having conducted hundreds of these types of assessments for heliports over the past 20-plus years, I have rarely found two projects to ever be the same.

So, is eVTOL transportation right for your city? Only through careful analysis can anyone hope to answer that question correctly. The vertiport applicant will be the one who bears the brunt of this responsibility, and must be properly informed so as to get things right the first time. There is a real risk that applicants may end up investing significant time, effort, and money just to have urban planners not accept their application for vertiport infrastructure because it is not suitable for the community it is meant to serve.

The eVTOL ‘moon shot’

First, what is a sustainable city? The Global Platform for Sustainable Cities has defined the term using four key outcome dimensions. These include robust economic growth, prosperity, and competitiveness across all parts of the city; protection and conservation of ecosystems and natural resources into perpetuity; mitigation of greenhouse gas (GHG) emissions while fostering overall city resilience; and inclusiveness and livability, mainly through the reduction of city poverty levels and inequality.

I believe that eVTOL air taxis can contribute positively to all of these outcomes, but there are admittedly significant technological, regulatory, and social challenges standing in our way. The collective goal of the Vertical Flight Society (VFS) is to find solutions to these challenging problems. In my capacity as infrastructure advisor to VFS, I have personally witnessed a tsunami of interest and technical prowess being leveraged to solve each challenge we face. I personally like the way our executive director, Mike Hirschberg, describes this effort as being “equivalent to this generation’s moon shot.”

Having worked in the circles of Federal Aviation Administration (FAA) rulemaking and advisory circular creation for more years that I care to remember, I can attest to the fact that the regulatory piece of this puzzle will be a key challenge moving forward. On average, it takes six years for the FAA to go through a formal rulemaking process, and a new advisory circular can take upwards of three years to develop. Our problem now is that technology is outpacing policy so quickly we find ourselves in catch-up mode and are currently about two to three years behind. For this reason, VFS is vigorously coordinating efforts between industry and government to facilitate the necessary research and standards development needed to move policy forward so as to catch up to technology.

These efforts include working directly with the FAA and NASA to conduct technical workshops with industry, as well as identifying and making available subject matter experts to government, the National Academies, the National Fire Protection Association, International Civil Aviation Organization, ASTM International, and SAE International, to name a few. One key stakeholder that VFS has partnered with is the General Aviation Manufacturers Association, which through its tireless efforts has been making significant strides in moving eVTOL technology forward.

I agree with Powell that we must be very careful as to the standards to which we design our infrastructure. We want to ensure that cities and municipalities do not invest money and political capital in, or provide costly incentives for, the development of eVTOL air taxi infrastructure today, only to see it become obsolete in a few years due to changes in aircraft design, increases in aircraft size, or increases in gross weight. We must proceed carefully and constantly re-evaluate our assumptions.

In conducting master planning and modeling for any location, we must look at least 30 years into the future and plan for change, expansion, and a municipality’s integration of the unknown. Those who attempt to implement programs today based on a myopic and uneducated thought process for the integration of a UAM transportation model will most likely be rewarded with some very painful and expensive lessons.

Tackling the challenges

Let’s examine some of the specific infrastructure concerns raised by Powell, starting with electrical grid capacity. Working closely with power companies and electrical grid experts across the country, VFS is helping to better understand what our current grid system is capable of and what must still to be done to carry the load of this new transportation ecosystem. When considering the time constraints for recharging of aircraft, the goal is to achieve the necessary charge for an air taxi journey in 10 minutes or less during peak operational hours, with longer deep cycle charging being accomplished during off hours. Once this is achievable, turnaround time between flights can be significantly reduced, allowing for a higher volume of throughput.

Uber air taxi cabin view
The simulated view from an Uber Air eVTOL. Uber is one of the principal companies driving the vision for urban air mobility. Uber Image

As to the physical dimensions of a vertiport, this has yet to be determined. While many point to the fact that heliports are designed based on the physical size of the “design helicopter” and its main rotor diameter and overall length, this underlying criteria is actually based on a helicopter’s performance characteristics. This performance research was conducted in and around 1987 and is referenced in numerous Department of Transportation/FAA research and development documents.

Even if this research had been conducted with brand-new aircraft at the time (which I highly doubt), this research is now over 30 years old and is based on technology that is at least 40 to 50 years old. This same type of testing needs to be accomplished with eVTOL aircraft before we can successfully develop defensible vertiport dimensional standards. Until then, we can only make calculated assumptions with the realization that for these new aircraft to provide viable and safe transport, they will need to perform at least as well as, if not better than, their helicopter cousins. (This may be an opportune time to conduct follow-on helicopter research based on the newest technology as well.)

Our friends in the FAA who will be responsible for the development of vertiport design standards in the U.S. have gone on record saying that they will not develop any standards until they have relevant performance data from these new aircraft. Of course, this is a bit of a challenge at the moment, in that many of these aircraft are still in early stages of development.

However, before we get to the point of developing design criteria and standards for vertiports, we must first all align on what actually defines a vertiport. In this capacity, VFS is working closely with ASTM International in helping to develop an internationally recognized consensus-based standard as a starting point. Are vertiports different enough from airports or heliports to have their own specific standards, or are they similar enough to be blended with airports and/or heliports? These questions have yet to be answered.

Powell references a requirement for 200-foot (60-meter) spacing between final approach and take-off areas (FATOs) in current heliports. This is for a case when simultaneous operations are to be conducted. It should be pointed out that the FAA does not do a very good job in its heliport design guide of defining what these “simultaneous operations” at heliports are. There is also an internal FAA discrepancy when the heliport design guide is compared to guidance for air traffic control, which indicates that this 200-foot distance is measured from the center of each FATO, rather than from the edge. While this may not sound like a lot, it can equate to a difference of around 70 feet (21 meters).

The sustainability balancing act

I expect the decision as to whether or not UAM is right for a specific municipality will be one of the toughest balancing acts many planners have ever faced. They must weigh the different factors that contribute to sustainability, including economic prosperity, environmental protections, climate impact, and equity. No one piece in the complex puzzle of urban design and planning is a winner in all of these; the best planners can do is to look at the package as a whole and understand the tradeoffs. To accomplish this, city planners will need to arm themselves with the best knowledge and education on UAM and eVTOL transportation available.

One VFS partner that is working to address these needs of municipalities and cities when it comes to understanding UAM is the Community Air Mobility Initiative (CAMI). Through early involvement and education at the local level, CAMI and VFS hope to help municipalities make good UAM infrastructure and integration decisions. For this to actually take place, there will need to be federal and state standards for municipalities to reference.

Time has always been the ultimate equalizer for technology. Case in point, in 1956 IBM created a first-of-its-kind computer hard drive with five megabytes of storage, which was mind-boggling at the time. Although it could only hold the equivalent of a few digital photos, it took several men and a forklift to move and it cost $3,200 a month to rent, equivalent to $28,000 today. If I were to have told the individuals who were in charge of that project that someday they would be able to hold in one hand a hard drive that could store more than 12 terabytes of data, don’t you think they might have been just a little skeptical?

So, does eVTOL transportation have a place in your city? That all depends on your city’s individual needs, assets, funding, and transportation model. The needs of Bismarck, North Dakota, are very different from those of Los Angeles, California, and that is OK. UAM will never be a one-size-fits-all solution. But it can be a tool in a city planner’s toolbox for providing a sustainable urban design when it does fit.

We undoubtedly face a multitude of challenges in moving this new transportation model towards reality. Just as it was for the folks working towards the first moon shot, this represents one of the most ambitious crawl-walk-run projects ever undertaken by mankind. Within the ever-advancing ecosystem that is vertical lift technology, VFS’s goal is to help provide the synergy necessary for all stakeholders to identify and overcome these challenges through a concerted community effort. We hope that you will join us on this exciting journey.

Join the Conversation


  1. Let the eVTOL, Hybrid-Turbo Electric, Bio-Fuel, and Hydrogen Economy take place.

  2. Interesting article.
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    wishing to future proof their buildings.
    Advice for early adopters cannot be prescriptive but there are some basic assumptions and design characteristics which will create a Skyportz “shell” which may have to be adapted to future specific requirements.
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  3. Thank you for this very comprehensive and insightful article.

    In the predictable future, which will be determined by the current events related to the global COVID-19 crisis, we have to rethink our efforts to create a new ecosystem in air transportation – which neither should rely on battery-powered eVTOL aircraft only nor should it end at the edges of sustainable cities. If such cities will exist anymore in a few years as per definition stated in this article.

    A lot will depend on the speed and the strength of the revival after the crisis. But to do nothing meanwhile and to wait for the outcome would be poisonous to our society. A proactive approach to new solutions spec. in air transportation is urgently needed instead.

    Just to name some:
    – eVTOL aircraft should be able to operate independently and autonomous / remote controlled within / up to 1.000km / 620mi.
    – eVTOL aircraft should have a modular design to adapt these aircraft to several kinds of use in short time and for low costs.
    – eVTOL aircraft should be able to start / land on unfixed places and hillsides
    – for safety reasons and noise reduction eVTOL aircraft rotors and propellers should be shrouded or enclosed
    – eVTOL aircraft should be able to move independently on short distances.

    The reason for this high demands / rapid changes we find in the situation today, the 2nd April 2020.
    – There is no sustainable city per definition, even not Vienna or Munich, where I live.
    – HNWIs and VIPs have left NYC and other wealthy cities and it is unknown, when they will return – if ever.
    – There is a shutdown on all major passenger airports except those, which also serve as hubs in express goods service.
    – In some countries the state of war has been declared or is in consideration / preparation at least partially.
    – There is an urgent, but unsatisfied need for the transport of medical staff & equipment to hotspots and IC patients to hospitals with free IC capacities. Here in Europe that means to go over the Alps between Italy and Germany.

    There are and will be other needs as well – key word climate change. Alltogether it would make sense to learn from COVID-19 reality, to understand the resulting needs and to take a proactive approach to create an effective, useful, resilient, versatile and sustainable ecosystem in air transportation, based on modular eVTOL aircraft.

    “We should try the impossible to achieve the possible.” Hermann Hesse – writer and Nobelist

  4. Excellent take on UAM sustainability, Rex. In the end, it will depend on municipalities and the previous they did on sustainability. How they will integrate future UAM technology and routes with their green initiative will be key.
    I hope cities are already planning the integration carefully making use of local renewable energy companies and consultants to set a sustainable energy platform for our UAM future.

  5. These requirement list are great for us engineers. The requirements should not however, also include a solution.

    There is such incredible technology today, and through our digital infrastructure, have the ability to develop Solutions a hundred times faster than even 10 years ago.

    The fundamental core problem is aeronautical engineers today, do not understand hovering. The designs are for the most part based on toy drones, which does not scale up. This is the reason no one has put together a passenger carrier drone and have it fly upon assembly.

    We have VTOL patent application for a design that makes no noise, completely silent, and is four times more efficient. It’s based on core, fundamental physics. We are looking for funding.

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