With seemingly daily announcements (e.g. yesterday’s Joby/Delta home to airport press release) about electric aviation, particularly electric vertical take-off and landing (eVTOL), it is easy to believe that we are at the peak of inflated expectations for this mode of travel.
Underlying the public proclamations, glitzy graphics, and slick video animations, there are thousands of smart people from credible organizations working on the nuts and bolts to make travel by air more ubiquitous, sustainable, and affordable. This brief post will look at one such effort; Boeing and Wisk’s recommendations for deploying Urban Air Mobility.
Their 64-page document, Concept of Operations for Uncrewed Urban Air Mobility, (PDF) is uplifting in its detail of how they plan on moving to safe, affordable, sustainable, and accessible autonomous flight. It offers great insight into the medium term where they envision autonomous, eVTOL flight integrating into the existing National Airspace System (NAS).
From City Core to Rural Edge #
The definition of urban stretches to the edge of rural outposts as they expect the typical flights to range between 30 to 60 nautical miles flying between 1,200 to 5,000 feet (page 19). This range covers a relatively large territory and has the potential to reduce windshield time and travel costs for those living outside the city.
For instance, the rural areas between Mankato, MN, St. Cloud, Rochester, and the Minneapolis-St. Paul International Airport falls well within the 90-mile range (with reserve) of Wisk’s 4-person, Generation 6 aircraft. The drawing below implies a hub-and-spoke approach, whereas, according to work from EAMaven co-founder, Darrell Swanson, aircraft like the Wisk Generation 6, would probably be deployed in more of a point-to-point mesh configuration.
This document doesn’t provide an explicit look at the economics and the specifics of their target market. One has to think that the 30 to 60 nautical mile range is what they anticipate to be competitive with land-based alternatives, such as car-based rideshare or driving one’s car into the core of a city and all the attendant costs (e.g. downtown parking).
The document offers some important clues as to how they will use automation, electrification, and sharing to reduce operating costs.
One of the advantages of vertical take-off and landing is that vast amounts of land aren’t necessary for flight operations. That is, a flight could originate at a helipad modified to support electric aircraft, on top of a modified parking garage, or at an existing airport.
The Boeing/Wisk document envisions three types of locations, generically known as vertiports, where their aircraft would operate.
|Key Characteristic||One take-off landing pad, like a helipad on the top of buildings||Gate infrastructure and multiple take-off/landing pads||Includes base maintenance and hanger space|
All of the above facilities would include aircraft charging stations. It is likely that the turn-around time at these facilities matches the 15-minute charge time specified on Wisk’s website. In other words, with its top cruising speed of 120 knots per hour, one to almost two flights per hour per aircraft could be expected in the typical 30 to 60 nautical mile range.
An Open Multi-Modal 3D Transportation Network #
Boeing/Wisk envisions that the air service provided via their aircraft will enable multi-modal service journeys from origination to destination.
Using a so-called Booking Platform Service (page 35), the service provider could be a combination of rideshare (e.g., Uber), an app (e.g., Google Maps), a public transit agency, and/or an airline. With open APIs (Application Program Interfaces), the implication is that these flying ride-shares could be integrated with multiple ground transport providers, as well as multiple airlines.
Although there will be no pilot onboard, skilled ground personnel, in the form of aircraft inspection (page 44) and on-site passenger hospitality management (page 45), will be necessary at the various types of vertiports. This leads to the question of what will be the minimum number of flights/passengers a day required for a given vertistop/port/hub to make economic sense?
It points out that the ground personnel might be provided by a third-party service provider, implying a vertistop/port/hub operator could serve multiple carriers. This sort of open approach could lead to ground operators that might view vertiports as a feature that adds to their core product and not the core product itself.
Look Ma, No Hands (But Remote Eyes and Control) #
Implicit to the economics is autonomous flight. In lieu of a pilot in the aircraft, Boeing/Wisk proposes, initially, that there is one MVS (Multi-Vehicle Supervisor) for up to three aircraft. The MVS is the pilot in charge of working out of a fleet operations center.
The MVS monitors the “airspace, flight path, and aircraft health.” (page 54, figure 15). At the same time, Boeing/Wisk is planning on leveraging the Minimal Operations Performance Standards of RTCA’s DO-365B for Detect and Avoid Systems to account for unforeseen obstacles.
Although the aircraft flies itself based on a pre-determined flight path, the MVS is monitoring its operation and “will be able to override any automatic and autonomic behavior of UAM aircraft,” if needed (page 14). There are contingency plans in the event of a loss of communications (e.g. land in a pre-determined safe spot, page 41).
A Robust Radio Link Is Critical #
Removal of an onboard pilot will require a robust Command and Control (C2) link between the aircraft and the MVS. They are looking at a link that is dedicated to a given flight, as indicated on page 34;
“Frequency and spectrum reservation will be required as part of flight planning to ensure that UAM operations will not be negatively affected by frequency congestion or lost-link states along routes.”
Air-to-ground radio links specified in RTCA DO-377A describe the minimum system performance.2 It isn’t clear what the minimum data rates are and whether it is just telemetry data or whether it will include real-time video. If Sabrewing, with its approach to creating a remotely piloted cargo drones, is an indication, then a subset of the data will probably only be required and not full-resolution video.
Although Figure 10 on page 47 indicates security checkpoints at vertiports, the bigger challenge in an autonomous and connected transportation system is in the cyber world. Cybersecurity is baked into their plan from the beginning.
The invisible threats, whether hijacking a communications link or spoofing a sensor, most likely pose a bigger threat in a world where the pilot is a computer. Section 3.1.7 (page 23) points to two more documents from RTCA (RTCA DO-326A &DO-356A), that will be their guiding light in ensuring secure operations.
Up, Up, and Away #
The sky is truly the limit if the technology can scale as promised to make flight competitive with terrestrial means of transport. The bigger challenge is in the nuts and bolts of operation. In the case of operation, it means integrating with the existing National Airspace System as well as laying the groundwork for a system that includes an increasing amount of autonomy and electrification. This whitepaper is a good step in providing a roadmap for getting to that future.
1 Note, that the specification sheet indicates miles ($3 per mile), while the concept of operations document uses nautical miles for the typical range. In miles, the typical range would be 34.5 to 69 miles translating to $103.50 to $207 for a one-way trip.
2Note, the RTCA, as the standards body under subcommittee SC-228 (PDF), will continue to work with the FAA UAS Integration Office and the UAS community to evolve this standard, which could include Satcom and Cellular Network integration. A whitepaper (page 5) providing recommendations for AAM surveillance and spectrum considerations has a planned release of December 2022, while standards for the use of the UHF spectrum band (page 5) for C2 Links used in type certificated UAS is slated for July 2023.