At EAS V, Synergy Chief Operating Officer John Paul Noyes framed his presentation of the Synergy aircraft by showing a picture of a 1973 portable telephone, then comparing it to a current model. The clunky size, heft and limited utility of the former compared with its slim, feature-laden modern counterpart tells a story of intense design improvements, quantum increases in capabilities and far lower costs for a significantly better product – something usually anticipated in the history of modern products.
Along with that historically comparative pairing, though, he showed pictures of a 1973 Cessna 182 and its Lycoming engine along with shots of modern examples of the two. Not much other than the paint scheme distinguishes today’s Skylane from its antecedent. Following Noyes’ outlook, it’s a bit disheartening to review Wikipedia’s specifications for 182s for the past 54 years. Little, other than the introduction of improved instruments and Omni-Vision, has changed. Although a great deal of this is due to regulatory and insurance considerations, Team Synergy feels that such brakes on progress have no part in real-world aerodynamics.
Synergy, the stunning design Dr. Larry Ford revealed as part of his Green Flight Challenge introduction at the fifth annual Electric Aircraft Symposium in Santa Rosa, California at the end of April, is a contender, and one that expands the bounds of what’s possible. Designer John McGinnis explains that it’s really an “SUV” of a practical airplane – a description at odds with the initial impression of its fighter-like appearance.
His video on building Synergy and Friday’s closing presentation drew a strong reaction from attendees at the Symposium. Part of his approach is to simplify construction and lower the number of parts, making the airplane not only high-performance, but inexpensive – again at odds with its swoopy styling.
John discussed his aspirations with Tim Seeley following the Symposium and confirmed that he had a serious and new approach to making airplanes go fast economically.
Specification wise, the GFC version of Synergy has a wingspan of 32 feet and a total wing area of 156 square feet. With a competition weight of around 2,400 pounds, the design currently is shown with five seats. It is powered by the 180-horsepower Delta Hawk two-stroke, V-4 Diesel engine. By sucking the air ingested by the engine’s turbocharger through the cowling to control the fuselage boundary layer, he is able to provide some pressure thrust. He is reluctant to call the hybrid scheme pure “Goldschmied pressure thrust”, but the aggressive pressure recovery and laminar flow control, combined with drag recovered by the “wake impeller,” gives additional power efficiency. Cooling air is directed through carefully-designed channeling to cool various engine heat loads and joins the exhaust in a high speed, scavenged exit just ahead of the multibladed prop. He thinks he will get net cooling thrust, rather than the drag normally associated with engine cooling.
John’s web site explains a few details and gives some insight into his design philosophy, part of which is to recover the energy lost by wake vortexes through the double box tail configuration. Expanding on Burt Rutan’s use of winglets to, “Create yaw stability while reducing the energy of wake vortex,” McGinnis notes that putting airfoils in the 360-degree swirl of the vortex can bring benefits. “Depending on where they are located and how they are oriented, we can redirect the molecules we had previously whipped off into a frenzied spin and use them to create stabilizing forces… while leaving them slightly less energized than they were when we slammed into them. The ‘cost’ of doing this at the wing tip is therefore mostly ‘paid for’; whereas on most aircraft we pay double: first we throw air at the ground, paying an induced drag penalty, then we catch some of it (right in the middle of the downwash, where we tried to move it the fastest) and pay another induced drag penalty at the tail while we reduce the lift we just made. Even when we minimize the downforce of a tail, going faster brings it right back into focus because our most efficient airfoils have a strong negative pitching moment.
“After decades of study, I have discovered that the ideal place for a tail is connected to a wingtip by a tall, shared vertical winglet. In this location a deliberately strong negative lift from the tail can achieve its stabilizing action by reducing the strength of wake vortex, while constructively interacting with the other flight surfaces from the proper safe distance. Its downward force reduces wing bending moment, and in a swept wing design, counters wing twist.”
As explained in the videos, the approaches McGinnis and his team have taken amount to more than the sum of their parts, a working definition of the benefits of synergistic interactions. He noted that Synergy could achieve an 80-percent reduction in drag over that of a traditional configuration, but much of that is because the comparison would have to be made at Synergy’s much higher top speed.
Because the airplane is meant to go fast and carry a substantial payload, McGinnis doesn’t consider the 200-mile GFC the best showplace for the capabilities his creation can really show. He notes that in five-seat mode, he has only to obtain 40 mpg at a speed he doesn’t want to reveal just yet to qualify for the 200 passenger-mile-per-gallon criteria.
Lt. Colonel Tom Reynolds, with a long NASA test flight history, will pilot Synergy along with Noyes. Considering that many competitors have chosen a motorglider-like approach to their GFC designs, it will be fascinating to see how the different approaches compare in the actual Challenge.