Preparing Your Airport for Electric Aircraft and Hydrogen Technologies (2022)

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6 Emergence of Electric Aviation 1.1 Introduction Future generations of aircraft require moving from current fuel sources to alternative sources for aircraft power and energy, and the global aircraft industry is setting ambitious goals toward reducing greenhouse gas (GHG) emissions and evaluating noise implications and aviation energy use. Sustainable aviation fuels, electric aircraft, and hydrogen technologies are key ele- ments toward achieving net-zero carbon emissions by 2060. C H A P T E R   1 Did you know? Aviation has been working aggressively to reduce its environmental footprint since at least the 1970s, and the carbon-specific awareness has accelerated throughout the 1990s. In 1999, the Intergovernmental Panel on Climate Change of the United Nations released its special report, Aviation and the Global Atmosphere, which triggered research and development efforts around the world that led to significant emissions reductions on the newest aircraft technologies. Through its Waypoint 2050 report (published in 2020), the Air Transport Action Group identified several pathways it could take to follow its pledge to reduce net carbon dioxide (CO2) emissions by 50 percent in 2050 compared to 2019 levels. With the support of governments and the research community, global aviation will be in a position to reach net-zero CO2 emissions by 2060. The strategic thrust set forward by industry groups has been met with a host of new technologies and proposed operational concepts for future aircraft systems. Electric aircraft propulsion systems are one of the most disruptive of these ideas (requiring the most change), where electric motors provide all or part of the mechanical power required to drive the aircraft’s propulsive device (one or more propellers or turbines). These configurations can draw stored energy through various combinations of electrochemical solutions, including batteries, fuel cells converting hydrogen into electricity, or more conventional thermic-electric generators using hydrocarbon aviation fuels. 1.2 A Brief History of Electric Aviation Attempts at electric propulsion started in the early years of the aviation industry. In 1917, the Austro-Hungarian Petróczy-Kármán-Žurovec (PKZ-1) was the first electric-powered helicopter ever flown. The helicopter featured four arms with 3.9 m four-bladed rotors. The vehicle was powered by a 140-kilowatt (kW), 190-horsepower (hp) motor and was able to fly three people. Three flights were carried out before the motor failed, and the vehicle was abandoned.

Emergence of Electric Aviation 7   The advent of nickel-cadmium batteries brought a renewed interest in electric aircraft. The Militky-Brditschka MB-E1 was the first manned, fixed-wing electric aircraft, which flew on October 23, 1973, in Austria. The flight lasted less than 15 minutes. The aircraft was a conver- sion of a small Austrian HB-3 motor glider with an electric-engine Bosch KM77 of 10 kW. The first solar-powered plane took to the air six years later, on April 29, 1979, at Flabob Airport, Rubidoux, California. The plane was an experimental conversion as well and based on a UFM Easy Rider motor glider retrofitted with a Bosch 2.6-kW electric engine and nickel-cadmium batteries. It flew for a few minutes for half a mile, about 40 feet above the ground. Other small experimental aircraft were built and flown throughout the next decades. The long-endurance solar-powered e-aircraft. From 1983 to 2003, NASA and AeroVironment, Inc. developed and tested the following high-altitude, long- endurance, solar-powered, unmanned electric aircraft: Pathfinder, Pathfinder Plus, Centurion, and Helios. In October 2010, Solar Impulse 1 performed a 26-hour-long flight. In 2015 and 2016, André Borschberg and Bertrand Piccard flew Solar Impulse 2 around the world in 17 legs for a total flight time of 558 hours and 7 minutes. These performances demonstrated the feasibility of long-endurance, zero-emission electric flight. The first commercially available electric plane was the Alisport Silent Club “self-launching” glider of 1997 that was optionally equipped with a 13-kW electric motor and a 1.4 kilowatt-hour (kWh) battery. The next decade saw the electric aircraft concept gaining traction with new bat- teries and fuel-cell technologies being developed and the world realizing more and more the climate change threat. In 2003, the Lange Antares 20E was the first electric aircraft to receive an airworthiness certificate. The Lange Antares 20E is another self-launching glider, using a 42-kW motor and lithium-ion batteries to facilitate its climb up to 3,000 meters (at the time of this report, 50 Lange Antares aircraft have been produced). In 2007, the Comparative Aircraft Flight Efficiency Foundation held the first Electric Aircraft Symposium in San Francisco, California. Boeing flew its one-seat Fuel Cell Demonstrator based on a Diamond HK-36 Super Dimona the following year. The National Aeronautics and Space Administration (NASA) organized its first Green Flight Challenge in 2011, which was won by the Pipistrel Taurus G4. The Taurus G4 (powered by lithium-ion batteries) is a two-seat, self-launching sailplane able to fly up to 17 minutes and reach 2,000 meters using its single 40-kW motor. In 2009, the Yuneec E430 was the first elec- tric aircraft developed for commercial production in volume, either as a kit or as a light-sport aircraft for the U.S. market. It can last 2.5 hours with a useful load of 390 pounds and features a 40-kW brushless motor powered by lithium-polymer battery packs that can be recharged within 4 hours using regular electric plugs. In 2013, the Long ESA (a Rutan Long-EZ retrofitted with an electric powertrain) outperformed several 100LL-powered aircraft in comparative flights under the control of the Fédération Aéronautique Internationale (or World Air Sports Federation). Figure 1 offers a timeline perspective. 1.3 Toward Electric Air Transportation Current limitations in battery-specific energy density have curbed the capabilities of electric airplanes and their appeal to the market. While current electric aircraft programs have demonstrated the feasibility of these aerial vehicles, they have also highlighted their

Figure 1. Timeline of the emergence of electric aviation (1917–2020).

Emergence of Electric Aviation 9   shortcomings in terms of range, endurance, and payload. These limitations explain why these aircraft have mostly targeted the gliding and the flight training businesses: training flights are usually shorter with limited payload requirements, allowing the carriage of batteries. Fully electric configurations are commonplace for small-scale aircraft and unmanned aerial systems (UAS). Recent improvements in battery-specific energy density are sufficient enough to make smaller aircraft more attractive and to warrant economically viable electric transport aircraft. As improvements in battery technology, electric machines, power electronics, power distribution, and circuit protection systems continue to occur, high-power electrified aircraft concepts have become increasingly feasible. Even now, prototypes of clean-sheet aerial vehicles and experi- mental variants of existing aircraft retrofitted with electric powertrains have provided a growing number of demonstration flights. Electric aircraft configurations with up to a nine-passenger capacity have been flown to date, with future programs planning expansion to larger platforms. A thriving community of OEMs. Since the early 2010s, the number of electric air- craft projects—including electric vertical takeoff and landing (eVTOL) vehicles— has skyrocketed. No fewer than a hundred original equipment manufacturers (OEMs) are working on components or full aircraft concepts, with a majority being based in the United States. The advanced maturity of the technology, the commitment of the industry toward a “greener” aviation, and the capabilities and cost models of these vehicles being able to provide a different type of air mobility have attracted investors, entrepreneurs, innovators, and engineers with the support of governments and institutions. Recent programs tend to seek a “type certificate” or “supplemental type certificate” to get out of the experimental aircraft niche. For instance, Harbour Air and electric powertrain manu- facturer magniX flew a retrofitted DHC-2 Beaver seaplane in December 2019 and has applied to the Federal Aviation Administration (FAA) for a supplemental type certificate. In 2020, the two-seater Pipistrel Velis Electro became the first fully electric aircraft to receive a type certificate from the European Union Aviation Safety Agency (EASA). This development represents an important milestone for electrified aircraft systems, signifying the advent of practical, certifiable electric aircraft into the aviation ecosystem. Also, in 2020, magniX started trials of a retrofitted Cessna 208B Grand Caravan and announced a partnership with Universal Hydrogen to develop a solution for converting the De Havilland Canada Dash 8 (Q-Series) to an electric propulsion system powered by fuel cells. (See Figure 2.) Figure 2. Nearly 50 years of e-Aviation: Militky-Brditschka MB-E1, Pipistrel Velis, and magniX Cessna e-Caravan.