Rotor & Wing International
Found inFeature

A Disruptive Future

Fifty years from now, a reader curious about ancient thought on aviation may call up an hvpd (hologram virtual paper document) of this issue.

Fifty years from now, a reader curious about ancient thought on aviation may call up an hvpd (hologram virtual paper document) of this issue, available as part of R&WI’s 100th anniversary edition, and listen to this article with eyes closed — lips pursed in a wry grin, no doubt — while enjoying a safe, quiet, relaxing ride in a fully electric, fully autonomous, vertical-takeoff-and-landing (VTOL) air taxi.

“Electric and hybrid-electric VTOL aircraft are in their infancy today, but they will clearly begin flying commercial services within the next five to 10 years,” predicts Mike Hirschberg, executive director of the American Helicopter Society International. “Within a few decades, eVTOL will become ubiquitous.”

Helicopter industry advocate Hirschberg is a leading promoter of eVTOL technology as well, and he’s hardly alone in his belief that the next 50 years of vertical flight will see electric air taxis become as normal as automatic elevators. A couple of dozen industry and government speakers made that clear to several hundred receptive attendees during “Elevate Summit,” convened by cellphone ride-sharing service Uber in Dallas April 25 to 27.

A feature for R&WI’s 25th anniversary predicted greater acceptance of vertical lift and rapid expansion of technologies.

Need to get somewhere not too far away in a hurry, without wasting time sitting in a car stuck in traffic? Whip out your cellphone, call up your Uber app, enter your destination, reserve a flight, then wait for an Uber to come take you to the nearest rooftop “vertiport” for your private or shared eVTOL flight. That’s Uber’s vision of the future — a network of vertiports and eVTOLS that can carry up to four passengers on short hops of 50 miles or less at speeds far faster than cars (150 to 200 mph) and for about the same cost as a non-shared UberX car ride.

Uber hopes to start test runs in Dallas and Dubai in 2020. If — and that’s a big “if” — the many technological, regulatory, economic, environmental, market and cultural barriers can be overcome, and the necessary infrastructure can be developed, “in the long term, VTOLs will be an affordable form of daily transportation for the masses, even less expensive than owning a car,” Uber predicted in a white paper issued last October.

Of course, as Yogi Berra famously, or at least supposedly, said, it’s tough to make predictions, especially about the future. Here’s another prediction about VTOLs:

“A vehicle that can take you from your home to your office, to your country club, to your bank or to your friend’s house, by air or by road, whichever is most convenient, will have a vast usefulness. It will become a competitor of the automobile. Such a machine can and will be built.”

James G. Ray, famed test pilot, said that at a Philadelphia conference on VTOL aircraft — in 1938. But while a lot of people have designed and developed flying cars in the nearly 80 years since, and some of those cars have gotten airborne, the concept has never taken off.

That doesn’t worry eVTOL advocates, because neither Uber nor most of at least a dozen companies developing prototype air taxis are striving for flying cars. Their less formidable but equally exotic goal is electric air vehicles that take off and land vertically and fly reasonably fast without the noise and expense of a helicopter. That’s no snap, but neither was the helicopter.

What future historians might call the “Helicopter Age” began just less than a year after Ray, test pilot for Autogiro Co. of America (formerly Pitcairn Aircraft), envisioned flying cars giving Henry Ford a run for his money. On Sept. 14, 1939, Igor Sikorsky piloted the first flight of his VS-300, the first practical single-rotor helicopter, an event that proves the Yogi Berra Theory of Predictions. A mere three years earlier, in 1936, no less an authority than Orville Wright had written in a letter to a fan that “the helicopter type of aeroplane offers several seemingly insurmountable difficulties.”

After observing that the U.S. government already had “discontinued experiments” with helicopters “after spending more than $200,000,” and explaining that it was “quite easy to build a small helicopter which can lift itself,” but that physics made it “impossible to extend the size,” Wright concluded, “Experiments with this kind of machine are so costly, and the chance of developing anything having a commercial value so remote, I do not think any individual can afford to undertake them as a business proposition.” Wright was wrong, of course.

In addition to advocating eVTOLs, AHS’ Hirschberg is quick to add: “The helicopter is here to stay. There is no better machine for missions that require long hover times.”

The other thing helicopters do well is land where there’s no airport. But thanks to the aerodynamics of rotors, helicopters can’t fly very fast, and they make a fair amount of noise. Helicopters are also expensive to operate and maintain.

Cost and noise are the chief reasons why helicopter air taxi services started in the 1950s and 1960s never succeeded, though some still exist, serving small numbers of wealthy clients.

Aurora Flight Sciences’ eVTOL aircraft would provide on-demand transportation to minimize long commutes in heavy traffic and populated areas.Photo courtesy of Aurora

The need for speed, meanwhile, is why at least 45 combustion-engine VTOL, short-take-off-and-vertical-landing (STOVL) and vertical-or-short-takeoff-and-landing (V/STOL) aircraft able to fly faster than helicopters were built and tested in the last half of the 20th century. But only four ever went into production — a legacy represented by the “V/STOL Wheel of Misfortune,” an online graphic that Hirschberg updated in the 1990s and maintains today.

The ones scrapped “were extremely complex mechanically,” Hirschberg said. “Many of them had four or six — or as many as 10 — engines to try to have distributed propulsion. But the capability was never compelling enough to justify the cost, complexity and poor reliability of all those engines, transmissions, driveshafts and gearboxes.” The weight all that complexity added would have been enough alone to break the camel’s back in most cases. But that was before the drone revolution.

The last two decades have seen a frenzy of development of unmanned aircraft of all sizes, but especially little quadcopters and other hobby drones. Many eVTOLs now under development resemble those little drones because they make use of the same underlying technologies, including GPS, digital communications, miniature computers, lithium batteries, better electric motors and controllers, distributed electric propulsion, improved sensors, autonomous flight controls and lightweight composites. Those technologies, especially electric propulsion and autonomy, are what have led eVTOL developers to tackle a challenge not unlike the one Orville Wright viewed as insurmountable in the case of the helicopter. They are sizing up technologies proven to work well on a small scale.

Guaranteeing the safety of VTOL configurations unable to autorotate and using electric propulsion to generate enough power to lift useful amounts of weight are perhaps the biggest technical barriers to the anticipated eVTOL revolution. But if it arrives, the key enabler will be distributed electric propulsion. The ability to use wires or other conductors to transmit power to propellers or fans driven by electric motors allows designers to place rotors, propellers or ducted fans most anywhere on a flying machine, enabling configurations that promise to solve some of the stubborn aerodynamic problems that hamper combustion-engine VTOL and STOVL aircraft.

Airbus’ A3 envisions an eVTOL vehicle called Vahana.Photo courtesy of Airbus

GPS, digital communications and miniature computers, meanwhile, are the building blocks of robotic and autonomous avionics and flight control systems which (unlike a human pilot) can fly more complex, less inherently stable configurations — making the pilot optional.

This is important for eVTOLs, which advocates hope will be fully automated by the 2060s, but also for the military. Combat helicopters will still be around in great numbers 50 years from now, and human pilots will be flying many of them. But optionally piloted or drone helicopters will likely be doing “dull, dirty and dangerous” missions such as delivering cargo, something with which the U.S. Marine Corps has experimented in Afghanistan already. The U.S. Defense Dept. also is experimenting with hybrid-electric configurations to reap the advantages of distributed electric propulsion without relying for power on batteries, the “energy density” of which today is inadequate for all but the most limited air missions.

Techno-optimists are certain the battery problem will be solved, either by the advent of better batteries or other sources of electric power, such as hydrogen fuel cells. They’re also sure ways will be found to make eVTOLs safe and quiet. If they’re right, helicopters and fixed-wing airplanes will be sharing the skies 50 years from now with unmanned tilt-wings, unmanned tail-sitters, new kinds of tiltrotors, speedy compound helicopters and fleets of short-range eVTOLs.

A few months before that 1938 Philadelphia conference, famed aeronautical engineer Alexander Klemin described the Holy Grail of aviation. “The conquest of the air in its broadest sense,” Klemin said in congressional testimony, “will only come when we can do in the air substantially everything that a bird can do in the air.”

In 2067, thanks to the technologies of the drone revolution and electric propulsion, the 100th anniversary edition of R&WI may include a beautiful new graphic: The Electric VTOL Wheel of Good Fortune. Through the haze of the future, the Holy Grail is in sight. RWI