Hybrid Aircraft Archives - FLYING Magazine https://cms.flyingmag.com/tag/hybrid-aircraft/ The world's most widely read aviation magazine Tue, 22 Oct 2024 18:14:27 +0000 en-US hourly 1 https://wordpress.org/?v=6.6.1 FAA Finalizes Rules for Powered-Lift Aircraft https://www.flyingmag.com/modern/faa-finalizes-rules-for-powered-lift-aircraft/ Tue, 22 Oct 2024 16:59:02 +0000 https://www.flyingmag.com/?p=219886&preview=1 Rule covers pilot training and operations of powered-lift aircraft, such as electric air taxis.

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The FAA on Tuesday published a highly anticipated special federal aviation regulation (SFAR) that charts the flight plan for a new generation of aircraft.

At the National Business Aviation Administration-Business Aviation Convention and Exhibition (NBAA-BACE) in Las Vegas, FAA Administrator Mike Whitaker signed the SFAR, which contains initial operational rules and pilot training requirements for powered-lift aircraft and will remain in effect for 10 years.

“It’s here today,” Whitaker told NBAA-BACE attendees Tuesday morning. “It is now a final rule.”

The FAA called the SFAR the “final piece in the puzzle” for introducing powered-lift aircraft, which could begin flying passengers, cargo, and even ambulance services in rural and urban areas as soon as next year.

The category is a relatively new, special class of aircraft covering designs that take off vertically like a helicopter but cruise on fixed wings like an airplane. To be considered powered-lift, the aircraft must generate lift primarily from its engines—which can be electric, hydrogen, or hybrid-powered—while relying on rigid components, usually wings, for horizontal flight. They will become the first new category of civil aircraft since helicopters were introduced in the 1940s.

The FAA sometimes refers to these as vertical takeoff and landing (VTOL) or advanced air mobility (AAM) aircraft, the latter term covering new aircraft technology more broadly.

FAA test pilots take Beta Technologies’ Alia electric VTOL aircraft on an evaluation flight. [Courtesy: Beta Technologies]

For years, the agency communicated to the aviation industry that there would be a pathway for powered-lift designs—such as electric air taxis being developed by Joby Aviation, Archer Aviation, and others—to be certified as Part 23 normal category aircraft.

But the regulator unexpectedly reversed course in 2022, determining instead that they would be certified as Part 21 special class aircraft. That kicked off a yearslong effort to develop an entirely new set of rules for powered-lift pilot training, operations, maintenance, and more.

The FAA last year released a proposal addressing several of those areas. It was panned by a collective of industry groups, however, who argued that the proposed pilot training requirements were too strict. They also clamored for performance-based operational rules—drawing from aircraft and rotorcraft guidelines as appropriate—rather than the creation of a new powered-lift operational category, as the FAA proposed.

FAA and Department of Transportation officials have promised to address the industry’s concerns. According to Whitaker, the SFAR does exactly that.

“For the last 80 years, we’ve had two types [of aircraft], rotor and fixed wing,” he said. “We now have a third type…and this rule will create an operating environment so these companies can figure out how to train pilots. They can figure out how to operate.”

The SFAR applies helicopter rules to certain phases of powered-lift flight, regardless of whether the aircraft is operating like a helicopter or an airplane. But in response to the industry’s feedback, it uses performance-based rules for certain operations, applying airplane, rotorcraft, or helicopter rules as appropriate.

For example, powered-lift aircraft can use helicopter minimums for VFR and IFR fuel requirements and minimum safe altitudes when they are capable of performing a vertical landing at any point along the route, as a helicopter is. This will allow manufacturers to get around the issue of low battery energy density, for example, by lowering the fuel reserve requirement.

“The rulemaking approach now is to really focus on performance and making sure you can prove that you can operate safely, or you can meet certain performance metrics, rather than being prescriptive and telling you exactly how to do it,” Whitaker said. “So we’re trying to create a larger envelope to have different means of compliance for some of the requirements and the rules.”

The approach mirrors the European Union Aviation Safety Agency’s (EASA) special class for VTOL (SC-VTOL) rules, which base operational guidelines on situational factors—like reserve fuel levels—instead of aircraft design. It’s a change that will be welcomed by manufacturers, who can now design aircraft for a wide range of operations rather than those defined by a narrow powered-lift category.

“We need to have the flexibility to allow these businesses to succeed, do so safely, and adjust our approach as we go along,” Whitaker said.

The other major difference between the SFAR and the FAA’s initial proposal is the creation of a pathway to train powered-lift pilots with a single set of flight controls. Some programs will still require dual controls. But throwover controls and simulator training will be acceptable substitutes. The change is a big one, as many powered-lift manufacturers designed their aircraft—including trainers—with single controls.

“Some pilot training can happen in the normal way that it’s always happened, with an instructor that has a set of controls and a student that has a set of controls,” Whitaker said. “But sometimes it’s a single set of controls that are accessible to an instructor, so we have rules that allow for that type of operation. And sometimes they have other configurations. So there again, we put in performance metrics to make sure that the companies can train instructors, and the instructors can train pilots.”

Last year, the FAA released a blueprint intended to serve as a framework for policymakers, describing a “crawl-walk-fly” approach to integrate powered-lift designs alongside conventional aircraft. The agency predicts they will initially use existing helicopter routes and infrastructure, and pilots will communicate with air traffic control as needed.

But Whitaker on Tuesday said the FAA will continue developing a new ecosystem for powered-lift aircraft. Critical to its blueprint is the construction of vertiports: vertical takeoff and landing sites equipped with electric chargers and other powered-lift infrastructure.

“The blueprint that we put in place 16 months ago for introducing this technology includes vertiports, and we’ll continue to work on that issue,” Whitaker said.

Plenty more work must be done in order for powered-lift designs to take to the skies at scale. But the SFAR gives the industry a practical pathway to begin flying.

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Aura Aero’s Integral S Moves Closer to Its First Flight https://www.flyingmag.com/aura-aeros-integral-s-moves-closer-to-its-first-flight/ Mon, 24 Apr 2023 20:21:31 +0000 https://www.flyingmag.com/?p=170609 The French startup says EASA has cleared the way for its new aircraft’s permit to fly.

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Aura Aero, a French aviation startup, said the European Aviation Safety Agency, EASA, has issued a flight conditions approval for the Integral S, a two-seat airplane that the company is developing.

The recent approval, which Aura calls a “prequel” to the aircraft’s first flight, clears the way for the French civil aviation authority, or DGAC, to issue a permit allowing the company to begin flight testing. After successful completion of flight testing, the aircraft would be ready for CS-23 certification, which applies to small aircraft, Aura said. 

The Integral design represents a family of two-seaters that are capable of aerobatics. In addition to the S model, which has tricycle landing gear and a conventional engine, the company is developing the Integral R, a conventionally powered taildragger version, and the Integral E, an electric-powered version available with either landing gear layout.

“The entire Aura Aero team is very proud today to reach a new milestone in the Integral adventure,” said Jérémy Caussade, Aura’s co-founder, president, and chief engineer. “We are eager to see this new plane take off. The Integral family is already a great success, with

over 400 orders or letters of intent.”

Aura, founded in 2018, says its goals include decarbonizing aviation. The company is also developing the ERA, or electric regional aircraft, a 19-seat airliner for which it says it has received numerous letters of intent. The company said it plans to conduct the ERA’s first flight in 2026, with the aircraft entering service in 2028.

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Technicalities: I Sing the Airplane Electric https://www.flyingmag.com/technicalities-sing-airplane-electric/ https://www.flyingmag.com/technicalities-sing-airplane-electric/#comments Tue, 28 Apr 2020 15:21:04 +0000 http://137.184.62.55/~flyingma/technicalities-i-sing-the-airplane-electric/ The post Technicalities: I Sing the Airplane Electric appeared first on FLYING Magazine.

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As I taxi out, a crisp shadow follows on the taxiway beside me. I give a little burst of power, then pull the throttle lever back to idle. Out of the corner of my eye, I see the shadow of the prop stop. “Uh-oh,” I think. “The engine quit.”

But no.

The airplane is a pod-and-boom single-seat ultralight converted by Mark Beierle and Gabriel DeVault to electric power using components from a Zero electric motorcycle. This is the first electric airplane I’ve been in, and I’m learning its peculiarities. One of them is, on the ground, if you pull the throttle—well, power lever—all the way back, the prop stops. You have to be careful of people standing around because when the master switch (or “kill switch”) is on, the motor is on as well, even when the propeller is not moving. It can silently spring to life at an inadvertent bump of the throttle.

The flight instruments are the minimum required and conventional; the powerplant instruments, on the other hand, consist of digital displays showing how much power you have left, how fast you’re using it, and how hot various parts of the system are. Having arrived at the runway, I am briefly frustrated by the lack of anything to do before takeoff. There’s no run-up and nothing to check. Not only that—the airplane, being an ultralight and beneath the notice of the FAA, has no N number. “Ultralight taking Runway 20 for takeoff, straight-out departure,” I report, with a persistent feeling that something is missing.

DeVault has told me that the full-power climb is unexpectedly steep, and the airplane is somewhat nose-heavy, and so, when landing, I should fly it on rather than attempt to stall it on. I retain the first of these warnings and forget the second. He’s right; the angle of climb is impressive, as is the deck angle, and I’m not even using full power. I climb straight out to 1,000 feet and turn northward along the coastline of Monterey Bay in California. It’s a beautiful day, the scenery is lovely, Santa Cruz serenely puffs cannabis in the middle distance. There is no vibration, but the airplane is noisier than I expected. You imagine an electric motor will be practically silent, and maybe it is, but the propeller, chopping its way through the disturbed wake of the pod and wing, isn’t. (DeVault has posted a bunch of in-flight videos that give a good idea of it. Search for “Gabriel DeVault electric airplane” on YouTube.)

Electric cars added the phrase “range anxiety” to our vocabulary. Flying an electric airplane is like flying a conventional airplane when you’re down to the last hour’s fuel. But at least in the electric airplane you know precisely, to two decimal places, where you stand; there’s none of that “Does the width of the needle count?” feeling. DeVault told me to come back when I’m around 30 percent of charge. After 40 minutes in the air, I am there and do. My landing is atrocious. Forgetting I’m not supposed to stall it on, I let the plane develop too much of a sink rate and then find I don’t have the elevator authority to arrest it. After I collide with the runway, an inept dance on the heel brakes ensues. Luckily, the landing gear is pretty stout—DeVault says that Beierle, the airplane’s designer, demonstrates it by veering around on rough ground like an SUV in a TV ad.

Well, I thought, that was fun—except for the end.

The fuel of electric airplanes is kilowatts. The watt is a unit in the metric system—our light bulbs have been metricated all along—and is the power of one volt at a current of one ampere. A kilowatt is 1,000 watts and equals 1 1/3 horsepower. Eventually, you stop having to make conversions, but as a novice, I still multiply kilowatts by 4/3 to get back to familiar territory. (For instance: The 100-watt bulb in my reading lamp draws about 1/7 horsepower.) DeVault’s motor has a peak output of 45 kW (60 hp) but, at that level, will soon overheat; it can run continuously at around half that power, but only 10 kW is required to maintain a stately cruising speed of 55 knots.

Gabriel DeVault with the electric Thunder Gull
DeVault prepares to plug in the battery for a recharge following the author’s flight. Courtesy Peter Garrison

The battery capacity is given in kilowatt-hours. It is as if we measured the capacity of fuel tanks in horsepower-hours rather than gallons. A 50-gallon fuel capacity is around 650 hp-hr and will keep you aloft for five hours at an output of 130 hp. The lithium-ion battery, with about one-fiftieth of the per-pound energy capacity of avgas, stores around 11 kWh. Charging time is a function of supply voltage; a 220-volt outlet will top a completely drained battery in an hour, provided a 50-amp circuit is available (because 50 multiplied by 220 equals 11,000). At typical electric rates, the cost of a full charge is $1.20. Alternatively, a 20-by-25-foot patch of solar cells—retail cost around $7,000—will do the same for nothing, assuming the sun is shining.

Read More from Peter Garrison: Technicalities

The motors of electric airplanes are much lighter and more compact than comparable internal combustion engines. Their power output is limited by, among other things, rpm—which, in aviation applications, can’t exceed around 3,000 because of propeller-tip speed—and importantly, by cooling. Being so compact, electric motors do not have a large surface area to dissipate waste heat; high-performance motors use liquid cooling and sacrifice some of the advantage of their small frontal area to the need for a radiator.

The electric motor’s throttle is its “controller,” which looks like an old-fashioned hi-fi amplifier with cooling fins. The controller works by interrupting the flow of electricity from the battery to the motor with fast solid-state switches. The more power you ask for, the more of the time the switches are “on.” The tempo of the switching is so rapid, the flow of power appears to be continuous.

As everyone knows by now, lithium-ion batteries have just enough energy per pound to permit flight, if at only low speeds and for short distances. Partisans of electric airplanes regularly predict imminent increases in battery capacity, but for the moment, what gets from a battery to the propeller is about one-fifteenth, per pound, of what we get from avgas. There are battery chemistries that are considerably more power-dense than lithium-ion but lack its virtues of rapid rechargeability and long useful life.

(The difference between the one-fiftieth I mentioned earlier and the one-fifteenth in the previous paragraph is the fact that electric motors are about three times more efficient than piston engines.)

I have it on good authority that no fewer than 230 companies, worldwide, are developing one kind or another of electric aircraft. Many of these are of the short-range, multirotor, VTOL, urban-taxi variety, for which electric propulsion is uniquely suitable. How suitable pure electric—as opposed to hybrid—systems prove to be for other kinds of aircraft will depend on still-unforeseeable developments in battery technology. Where there’s a will, there’s a way—but it might be a long way.


This story appeared in the March 2020 issue of Flying Magazine

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