Innovation in Aviation

The Sun Flyer 2

The Bye Aerospace Sun Flyer 2, Englewood, Colorado. (Photo by Mike Straka)

It could be argued that human flight – powered human flight – is one of the most innovative and significant developments in all of human history.

After thousands of years watching birds fly and wondering what it would be like to see the world from the same vantage point, and after many many failed attempts with sometimes zany mechanical contraptions, humans finally achieved powered flight on the beaches of North Carolina in 1903.

In just a little over a decade after that historic first flight, aircraft became instrumental for both sides during World War I. And a couple short decades later, air power proved to be a decisive factor during World War II.

Between the 1940s and 1960s, the massive investment during World War II as well as technological innovations in aviation and aerospace helped propel the U.S. into a position of global economic leadership and landed humans on the moon. Air travel has progressed from being solely the domain of the affluent to being accessible and indeed necessary for conducting business and driving the global economy. Civil aviation is now available to almost anyone with the need or desire for travel.

Over the past 20 years or so, general aviation has exploded in the number of types and designs of aircraft to include amateur-built, home-built, ultralights, gyrocopters, motor gliders, and so on. One need only visit the Experimental Aircraft Association’s website at to get an idea of how many kinds of flying machines are out there. The number of amateur- and home-built machines is now approximately 33,000, double the number in 1994.

To illustrate the economic impact of aviation worldwide, the International Air Transport Association (IATA) states that globally, aviation accounts for moving fully a third of all goods brought to market and supports 65.5 million jobs. In the U.S., civil aviation supports 10.6 million jobs, and the aerospace sector typically has a positive balance of trade, by $84 billion in 2017 alone.

In this space we’ll periodically talk about innovations driven by aviation and aerospace, and how these current and future developments might impact our lives and livelihoods.

Amid a newly arisen awareness of environmental issues assisted by a substantial increase in noise complaints nationwide over the past 10 years, the aviation industry has been making significant advances in turbofan technology. The result is that these are no longer your father’s jet engines. They are much quieter and consume less fuel than the engines of the 50s, 60s, 70s, and 80s. Of course, there many aircraft remain in service with the older engines so a complete changeover to the newer, more efficient engines will likely take another decade or two.

Related to environmental considerations but with an eye toward achieving sustainable operations, particularly as the aviation industry expands worldwide, innovation in the development of alternatives to the carbon-rich fossil fuels Jet-A and 100LL has also accelerated. In this area the results have not yet matured and are decidedly more mixed compared with advances in engine technology.

But before discussing alternative fuels, I should note that some significant advances have been made to improve the standard piston aircraft engine. These are perhaps best exemplified by Rotax engines, whose 912 model with its small size and liquid-cooled cylinder heads has taken the Light Sport category by storm. Combined with amazing fuel efficiency and extremely aerodynamic LSA designs, the 80-horsepower Rotax 912 will yield 120 knots true airspeed on 3.8 gallons per hour. The Rotax 915iS promises to spur even more innovation in airframes specifically designed from scratch to meet its performance numbers. The 915iS features will generate 135-150 horsepower, is fuel injected, turbocharged, partially liquid-cooled, drinks autogas, and has a redundant electronic ignition. Depending on the airframe, true airspeeds will be around 140 knots on 4.6 gallons per hour.

The airframe development just mentioned will benefit from advances in composites and additive manufacturing (3-D printing), the latter of which will greatly speed up production/turnaround times and presumably lower costs.

Getting back to alternative fuels/propulsion technologies, there are three classes in various stages of development: petroleum-derived diesel, biofuels, and electric.

Since diesel engines can burn jet fuel they have a lot of potential, and its worldwide availability  is one advantage of diesel engines, as is their lower fuel burn rate. However, progress in developing diesel aircraft engines has been relatively slow, and engine conversions are expensive.

After several years of development and technical review by airframe and engine manufacturers, and oil companies, biofuels were approved for commercial use in 2011. Biodiesel in particular has found a niche in commercial use, with United fueling at least some of its aircraft with a 30% biofuel mix. There are a plethora of biofuel manufacturers, but production at the scale needed for commercial aviation is nowhere near what it needs to be. Nevertheless, the motivation to continue development of biofuels is strong, given the widespread concerns over emissions and the growing desire to reduce the industry’s carbon footprint given the forecast expansion of air travel worldwide.

What appears to be the most promising innovation in future aircraft propulsion technology lies in hybrid, electric, and solar/electric. However on a large-scale practical level, the infrastructure required for nationwide recharging is nowhere near implementation. And as is always the case with battery power, the energy density needed for aircraft is just barely there even for short training flights.

Two aircraft design firms are leading the pack in terms of progress toward certification: The Pipistrel Panthera is one that seems to live up to its marketing hype. A 4-place prototype is undergoing flight testing with its conventional serial hybrid powertrain consisting of a Siemens electric motor driving the propeller and a Lycoming IO390 gasoline engine to power the generator to keep the batteries charged. It will attain 170-175 knots true airspeed at cruise power while burning 9.6 gallons per hour. The downside is that this aircraft in the hybrid configuration is pushing $500,000, so any economy achieved by the hybrid is likely offset by the price.

Another aircraft undergoing certification testing is the solar-electric Sun Flyer by Bye Aerospace at Centennial Airport in Colorado. Its 115-horsepower Siemens motor will attain 138 knots compared to 122 knots for the Cessna 172, and its solar cells will extend battery life to enable a 3-hour flight on a single charge. This translates into a cost of about $3 per flight hour. The payload of the Sun Flyer 2 is comparable to the 172 at 440 pounds vs 450 pounds. In addition, the Sun Flyer 2 has a significantly higher lift-to-drag ratio of 20.6 compared to the 172. This is in no small part attributable to Bye’s experience working with the solar-electric Silent Falcon small UAS system.

Aspen Flying Club, part of the American Flight Schools family, has placed an order for 30 of the 2-place Sun Flyer 2 models as it builds an electric fleet to complement its standard piston fleet. The Sun Flyer 2 will retail (without options) for just under $290,000 and the 4-place Sun Flyer 4 will go for $390,000.

Finally, electric and hybrid-electric vertical takeoff and landing (eVTOL) aircraft have been pushing the envelope of possibilities for explosive economic growth through greater access to the benefits of aviation. One research firm estimates that the eVTOL air taxi market will reach $1.5 trillion by 2040. We’ll see how this pans out, but airport managers and community leaders would be well-advised to be cognizant of these developments and their potential for huge economic benefits, and position themselves and their communities to accommodate them as best they can.


Mike Straka, PhD
HN Contributing Author & Technical Support
Executive Director, Colorado Aviation Business Association