eVTOL air shuttles, air taxis, and flying taxis- air mobility services for the average Joe/Jane or just a Jetson fantasy?
The press is full of articles on Advanced Air Mobility and how many existing and aspiring plane makers are soon going to be building electric air taxis and flying cars for air taxi services in our major, and very congested, cities.
Air/Flying taxis are nothing new and helicopter charters are available globally to transport the rich and corporate executives, who do not own their own helicopters, into the city and across the region. In fact, the first air taxi (helicopter) to be certified for civilian passenger transport was the Bell 47 in 1946. New York Airway offered the first airport air shuttle / taxi service in 1953 from LaGuardia into NYC using Sikorsky S-55 helicopters. Aviation had ride hailing sharing before Uber, when Evolux introduced the first flight hailing/sharing (aerial ride hailing/sharing) app in 2008.
The biggest hurdle any aspiring civilian passenger eVTOL maker faces is certification by civilian aviation authorities like the EASA or FAA. At this stage only 4 eVTOL aircraft makers have formal FAA type certification process in process and one of those is for a pure cargo eVTOL, while Volocopter are in the EASA process with the VoloCity and Ehang’s 216 with the CAAC. Given the nature of the process and the need to develop standards for electric propulsion in aviation, it is likely that certification could be in 2023 at the earliest. A major certification requirement for rotorcraft and other VTOL aircraft has always been the ability to glide or perform an auto-rotation landing in the event of loss of power. Ballistic parachutes are an option but would need some way of maneuvering the aircraft when the parachute is deployed to guide it to a safe landing spot in congested areas.
Air taxis and flying cars will never be a mass transit option, given that basic aviation safety dictates a minimum height above the ground and minimum separation between aircraft and cities radiate out from a central business district or city center with limited safe, unrestricted airspace, together with the need for licensed public helipads and the limited number of approved flight corridors / lands, limits the number of aircraft of all types operating above the city at any point in time. Digital ATC and UTM systems will assist in optimizing the safe use of such airspace as will mandatory ADS-B and remote ID with detect and avoid systems.
The minimum final approach and take off (FATO) requirement for a helipad / vertipad is 100 by 200 feet (20000 square feet) while a 2 take off and landing pad vertiport with six parking/charging bays will require 64000 square feet with clear approaches and climb areas. Given that a vertipad with no separate aircraft parking areas can safely handle 15–20 air movements per hour vs 60 or so for a two take and landing pad vertiport with parking, every 1000 passenger hourly capacity requires at least 8 vertiports or 4 times as many single vertipads,
The wind effects, wind channels and turbulence created by big tall building in cities has a significant impact on the operating heights, the minimum size of aircraft, and the siting of landing areas / helipads — See the BBC article: The problem with the skyscraper wind effect: https://www.bbc.com/news/magazine-33426889
The technical challenge is how to power the electric motors and while Lithium Ion batteries dominate the car market, thoughts of Boeing 787 battery fires and aviation authority concerns with electronic device batteries aside, batteries are too heavy and have too low an energy density and when you need 20 minutes power reserve, will be challenged to provide sufficient range for more than one 20 minute revenue flight and in keeping aircraft weight down. Drone and UAV makers lead the way here with fossil fuel genset hybrids and fuel cell powered aircraft. While fossil fuel hybrids are most likely to dominate the early eVTOL market, fuel cell power (especially if they use hydrogen produced onboard from green Liquid Organic Hydrogen Carriers) is a viable climate friendly choice.
What muddies the waters, is the idea that air taxis will be fully autonomous from day one. Despite the fact that the first autopilot was developed by the Sperry Corporation in 1912 and auto throttle, autopilot and autoland are a standard feature on almost all commercial aircraft, even the most sophisticated planes still have a human pilot taking off and doing many of the landings. Artificial Intelligence (AI) not only lacks human feel, intuition, judgement and EQ, but also lacks the unique human ability to do things that have never programmed to do, learnt or been taught to do, especially in an emergency. One shudders to think what the outcome of the US Airways Flight 1549 water landing (on the Hudson River on January 15, 2009), or the Air India flight 191 emergency landing (pilot lands at Newark airport despite multiple system failure, adverse weather, lack of fuel) on September 11, 2018) would have been, if these had been autonomous flights. AI, like existing autopilots, is still dependent on data provided by a myriad of sensors and needs to be used with a human pilot — AI should assist not replace a human pilot and vice versa especially when one considers that you will still need an on-board human officer in command to deal with not only the odd passenger panic attack or unruly passenger, but to take control and press the reboot/reset button when required.
Passenger drones (pilotless aircraft) may be great for theme parks and are best suited for military use (like casevac and special operations), but even the military after 103 years of powered drone use have yet to transport troops in pilotless aircraft operationally even over the wide open unpopulated test ranges. Civil aviation authorities, like the EASA and FAA, and governmental security agencies are unlikely to allow commercial passenger operations for decades to come. AI holds great promise as an enhancement to, or even replacement of current autopilot systems on commercial passenger aircraft as demonstrated by Airbus’ ATTOL system.
eVTOL is here and it will be a major game changer by bringing more affordable, climate friendly eAviation to the airspace above us. It will revolutionize emergency services, provide better aid and relief response, provide law enforcement and nature conservation with cost effective air capability, and provide much needed rural air mobility for remote communities, especially in developing countries where helicopters are just too expensive to operate.
eVTOL air shuttle services are likely replace conventional aircraft between cities by providing faster city center to city center connections, while air taxis will provide more affluent commuters, business people and wealthy commuters with a faster alternative means of traveling in cities, but air shuttles from outlying or hard to reach suburbs (where the number of commuters does not justify building or upgrading roads and highways or building new railway lines) and airports to the city center will dominate urban air mobility.
In closing, even if eVTOL operating and maintenance costs, turn out to be as cheap many start-ups claim — qualified pilots do not come cheap and landing fees are and will still be a significant cost item, so while passenger urban air mobility will be more accessible to the average Joe or Jane, it will still be a premium transport option, compared to a bus, car or train for the average person.
Original article published on Linkedin, September 18, 2018