Congestion, Safety Concerns as UAM Vehicles Enter Airspace Over Next 10 Years

September 2019

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The number of airline passengers per year will double by 2037 to 8.2 billion, with the largest growth in Asian markets, according to an October 2018 prediction by the International Air Transport Association. To accommodate those passengers, the number of commercial airliners worldwide will also increase, from 29,093 in 2017 to an estimated 46,878 in 2037. 

 The exponential rise in demand for air travel and the corresponding increase in airline traffic comes at a time when the urban air mobility (UAM) industry is just getting off the ground, figuratively and literally. Uber has updated the target dates for its Uber Elevate shared air transportation program to begin in Dallas, Los Angeles, and Melbourne, Australia, using small four-passenger electrical vertical takeoff and landing (eVTOL) vehicles. Working with six eVTOL manufacturers, three municipalities, and the aviation governing bodies in the U.S. and Australia, Uber plans to begin demonstration flights in 2020 and commercial operations in 2023. 

With the ever-increasing number of aircraft, and soon UAM vehicles, crowding the skies, congestion and safety are rising concerns. To help mitigate congestion at major airports in the U.S., NASA recently introduced ATD-2 Integrated Arrival, Departure, and Surface (IADS) Operations at Charlotte Douglas [North Carolina] and Las Vegas McCarran International airports. Part of the Airspace Technology Demonstration (ATD) project, ATD-2 integrates technologies already implemented by the FAA and the airline industry to streamline ground, arrival, and departure procedures. 

Communication between the tower and various airport surface stakeholders— including aircraft at the gate or in various stages of arrival and departure—is key to the program’s success. For example, ATD-2 departure metering may recommend that a flight hold a few minutes longer at the gate rather than waiting in a long departure queue at the end of the runway. This can save fuel, reduce emissions, and reduce surface congestion and delays. During the field-testing phase at Charlotte, from Sept. 29, 2017 through May 31, 2019, ATD-2 saved airlines 298.2 hours of surface delay and 357,181 gallons of fuel, resulting in reduced carbon-dioxide emissions equivalent to 55,954 trees.
 
While a November 2018 NASA UAM market study finds a ubiquitous air-taxi system such as Uber Elevate “unlikely to be profitable” through 2030 due to infrastructure costs, governmental barriers, and public distrust, the study still predicts 40,000 unmanned aerial system (UAS) vehicles could be flying “last-mile” package deliveries by 2030, and an additional 23,000 UAM vehicles could be flying point-to-point routes in metropolitan areas by that time, despite public barriers. Even Uber is beginning its quest to conquer autonomous flight with Uber Eats deliveries by drone; test deliveries commenced in San Diego in July 2019.

One barrier to UAM operations is the current regulatory environment, which does not permit the types of vehicles and operations that would make UAM feasible. However, several government agencies are working with industry leaders to develop the vehicle-certification requirements, traffic-management requirements, and safety regulations necessary to allow UAM operations. To mitigate congestion once regulations allow UAS and UAM operations on a large scale, the FAA and NASA are working on a UAS traffic-management system (UTM) to determine how UAM vehicles will be separated and controlled in public airspace.  

“We live in an air-traffic-management [ATM] infrastructure, which means the aircraft is talking to someone on the ground, usually ATC, and that will initially continue with UAM,” said Mike Ingram, VP of Cockpit Systems at Honeywell in Phoenix. “But there’s a huge amount of discussion and rulemaking around autonomous flight, UAS traffic management [UTM] and defining UAM  corridors. Likely, the scheduled or monitored traffic will stay out of these [UAM] corridors, and vehicles within these corridors will have to self-separate and regulate themselves.”

The UAM vehicles using the proposed corridors will be equipped with technologies to detect and avoid (DAA) obstacles, aircraft, and other UAM vehicles. Products such as Honeywell’s IntuVue RDR-84K Band Radar System provide DAA functionality by gathering data through multiple sensors, using onboard software to process the data, and sending appropriate signals to the vehicle’s operator or flight- control systems. The IntuVue RDR-84K phased array radar uses multiple beams that detect several inputs simultaneously, including weather, aircraft, people, and other obstacles.
  
“Our high-frequency, short-range radar systems [like the IntuVue RDR-84K] can detect small flying obstacles such as birds and even a helium balloon going by the aircraft,” said Ingram. “So the UAM vehicles will be able to more easily avoid these unforeseen objects.”

Safety during navigation can also be a concern for UAM vehicles. While GPS provides enough precision location information for aircraft to reliably land in open areas like airports, urban environments often have dead spots where GPS information isn’t obtainable or reliable enough to safely operate unmanned vehicles. To address this problem, manufacturers such as Honeywell are developing new types of location technologies, including visual-based navigation, various types of radar, and inertial sensor navigation.
 
“In a wide-open sky, GPS works great, but we will need to have something supplemental to GPS for UAM operations,” said Ingram. “Honeywell has a large product line of inertial sensors used on civil and military air transports and there are other technologies like vision, telemetry, and terrain mapping that can be used either as primary or backup navigation systems.”

Honeywell also offers ground- and satellite-based augmentation systems (GBAS/SBAS) that improve navigation reliability and accuracy and may be options for UAM operators. Honeywell’s SmartPath GBAS uses four GPS receivers, an electronics rack, and a VHF antenna to send up to 26 available GPS approaches to aircraft. This type of ground-based system might be used at a UAM vertiport or by a network of vertiports that are in the same geographical area or owned by the same operator.

Honeywell’s KGS-200 GPS/SBAS system improves the accuracy and reliability of GPS position in the aircraft by using measurements taken by reference stations across a continent to correct GPS signal-measurement errors and provide information about the accuracy, integrity, continuity, and availability of signals. 

The ultimate goal for most UAM operators is to take the pilot out of the cockpit and fly autonomously. Since it will take a while for the general public to feel comfortable flying without a pilot, and for regulators to allow passenger-carrying autonomous flights, UAM manufacturers are exploring ways to safely simplify vehicle operations to make the vehicles easier to fly.  Also in parallel, there is a push to reduce the pilot qualifications thus allowing more, less-skilled pilots in the cockpit.  In the end, the pilot-less vehicles must be able to land safely in an emergency either autonomously, by a controller on the ground or by the occupants on board, this is yet to be determined.

“Most of these [UAM manufacturers] are beginning their flight testing unmanned, testing out their flight-control systems, the [software] logic to prove out the vehicle before they put a pilot in it,” said Pete Bunce, CEO of the General Aviation Manufacturers Association.  “They’re going with the idea that they can in fact operate with or without a pilot and can therefore simplify the interface.”

Simplified interfaces can take advantage of small but robust avionics systems such as Honeywell’s Compact Fly-by-Wire system for Part 23, eVTOL, and UAM platforms, which provides a redundant triplex architecture to seamlessly transfer control without disturbing aircraft control and keeps the aircraft within prescribed flight-envelope limits even if a pilot becomes disoriented. 

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