There is a LOT to learn about this counter-intuitive airplane, but the most obvious thing about Synergy is its distinctive tail configuration. It taps into a technology that could give any well-designed airplane a fundamental advantage.
Every airplane has a wingspan, and a weight. Our underlying breakthrough is a technology that makes a given wingspan work much better at a given weight. This is called span efficiency, and unlike any normal wing, the DBT configuration can reach the theoretical limit for it.
As weight increases, such as for an electric aircraft, more payload, or longer endurance, the advantage of span efficiency increases exponentially. This technology especially applies to all planes that have to weigh more, or fly higher or faster, or maneuver efficiently under G-force loading. Our patented “Double Boxtail” configuration (DBT) causes the drag penalty of weight to greatly diminish for a particular wing span.
The DBT configuration (US8657226, 9545993) is also the right starting point for using other, more technical drag-reducing technologies, such as laminar flow, wake propulsion, pressure thrust, and boundary layer control. In fact, it is easily the best arrangement to allow a car-like passenger plane to reach the speeds where such technologies bring benefit.
Our name is not a buzzword. When taken together synergistically, these technologies improve aerodynamic performance to the Gabrielli-von Karman limit, a benchmark that is anywhere from two to fifteen times as efficient as typical powered aircraft, depending on their speed. No manned airplane has ever come remotely close to such fuel-efficient high performance in this speed and weight category.
Here are some of the benefits of the unique new DBT technology, as it applies to our first aircraft in particular.
- The Synergy configuration lowers induced drag (the drag due to lift) to the theoretical limit for a given wingspan. Its ‘non-planar’ span efficiency is 1.46 times that of an optimally loaded planar wing of the same span, allowing a strong, compact form more capable of higher speeds than a long, glider-style wing. Decreasing the induced drag of an airplane provides benefits in climb, at lower speeds, when racing or maneuvering, at higher weights, and at higher altitudes.
- The Synergy configuration eliminates complexity. Its simple, seamless wings need no control surfaces or the many parts that would impose; for example, to achieve the major benefits of a sealed gap. Instead, only two moving surfaces are needed to provide a majority of flight control, and these two ‘high aspect ratio elevons‘ are equally simple, one-piece airfoils; merely supported at both ends so they can be rotated for control. (Thanks to its natural turn coordination, Synergy’s twin, V-tail-mounted rudders are rarely required in flight, but yes, we have (two) rudders on the full size aircraft!) Reduced complexity translates directly into reduced weight and reduced cost.
- The weight distribution of the structure is inherently ideal for keeping the structural costs down and the balance right. When flown solo and light, from the front seat, the balance provides nimble handling. As the aircraft gains more people or payload, it remains in proper balance and increases in stability. At maximum weights all remaining payload is carried right on the CG itself, and the aircraft achieves its most stable configuration. (Many airplanes suffer from the exact opposite condition as they get heavier: less stable, less safe.)
- Laminar flow and high span efficiency allows a bigger, stronger wing in comparison to typical high-performance designs. Providing increased fuel storage and slower landings, the wings can be stronger and stiffer for a given span loading. Wingtip twist, associated with swept wings, is balanced out of the system under G-loading by an always-proportionate, opposing downforce from the tails. Note, however, that Synergy doesn’t really have any ‘wingtips’. (How many do you see on other aircraft, counting every lift-producing surface? Each one is a drag source.)
- The DBT configuration creates a (patented) novel method for the prevention of stalls, and many DBT aircraft exhibit pre-stall behavior similar to the canard configuration. The Prime version uses a conventional method, in that its controls provide full authority without creating excessive wing angle of attack. In other words, the aircraft won’t even stall at all! However, in testing, with controls set to allow the excessive authority required to create a wing stall, recovery from intentional stalls was also instantaneous and without altitude loss, due to the large elevons becoming additional flap-like wing area (and, wing airflow control devices !) when commanded to lower the nose. Several versions of Synergy also show promising control behaviors during intentional ‘deep stall descent’ at relatively low vertical speeds. Total control of flightpath and attitude during fully stalled flight, with instantaneous normal flight recovery on command, has been demonstrated in a range of conditions. Certification of such potential requires that every possible combination of conditions be tested. We will not be configuring to allow intentional stalls or deep stall control potential until it has been exhaustively refined in full scale flight test. We do intend to offer a vehicle that has proven to be basically incapable of stall/spin departures from controlled level flight.
- The volume of air that is progressively displaced by Synergy in flight changes smoothly along its length in a way that properly matches an optimum ‘body of revolution’ shape in its speed range. This objective, called ‘subsonic area ruling‘, is quite different in character than for supersonic aircraft. Its shape is designed to promote stable near-field pressure gradients in all phases of flight, drastically reducing the true source of catch-all “interference drag” and turbulence. It takes an extraordinary aircraft to benefit from, or preserve, refinements in this category. Normally the esoteric benefits of pressure field tailoring at subsonic airspeeds are lost before they can be seen, let alone studied, because of high turbulence in the fuselage region. Thus, conventional wisdom ignores subsonic volumetric tailoring entirely. (Nature, however, doesn’t, and this is part of the reason we can often accurately associate efficiency with beauty.)
- The Synergy DBT configuration exhibits superior handling at all speeds, including ideal turn coordination. Most aircraft require a vertical tail and/or rudder input to counter adverse yaw. Synergy carves turns like a finely tuned motorcycle.
- The DBT configuration creates a smoother ride in turbulence, and a noticeably more stable platform overall, thanks to moderate wing sweep and effective ‘decalage.’ Synergy’s remarkable stability provides the opposite of a ‘short-coupled’ aircraft. Like a strong man with his hands and feet wedged into the corners of a doorway, Synergy intentionally leverages against the atmosphere with every flight surface, despite having a wing planform that doesn’t, technically, even require tails. (!) This stability actually increases as the angle of attack is increased, which is opposite to many aircraft and highly beneficial.
- Synergy’s double boxtail configuration creates constructive, beneficial wing-tail interaction, rather than (destructive) “biplane interference”, allowing wing and tail to cooperate together for lower drag. In addition, all airfoil surfaces continue the low pressure or high pressure assignment of the surface adjacent to it, virtually eliminating the famous interference drag problem common to box wing designs.
- Pilots and passengers can see in every direction, and the jet-like nose allows all kinds of doors and nose openings to be used for passengers, cargo, and medical access purposes.
Various DBT models have been making the above obvious for some time. Wanna see it fly?
Presently, Synergy Prime, Synergy derivatives, and other DBT aircraft designs are being developed and studied by governments, industry, hobbyists, and universities. A large, fast aircraft is required to achieve the size/speed regime where our (equally valuable) high speed drag reduction technologies make on-demand regional transportation possible, but it’s truly exciting that these many DBT benefits typically result in beautiful, well-mannered aircraft that are a joy to fly.