Here you’ll find the answers to our most frequently asked questions. If your question isn’t answered here, or on our technical pages, you can contact us directly.
In 1974, champion model aircraft builder Burt Rutan, having become an aeronautical engineer, flew his jet-like VariViggen homebuilt airplane to Oshkosh after eight years building. This was a feat that Pat McGinnis and his young son admired greatly, and hoped to one day emulate. In subsequent years Burt Rutan’s profoundly innovative designs continued to inspire the world, including the McGinnis family.
As a student pilot in high school, John wrote to Burt, expressing his deep admiration and desire to apply his similar skills at the Rutan Aircraft Factory during or after college. By the time Rutan offered his self-proclaimed protege a job as his ‘right hand man in engineering’ at the fledgling Scaled Composites, other opportunities and developments had outshined John’s potential career in Mojave, but his fascination with Burt’s work and the unchanging physical principles behind it remained.
In 2005 a derivative of a Rutan design, the five seat Velocity XL, had become the top contender in a marketing plan/transportation solution for the snowboard company John and Pat had started…and all was well until studies to improve its performance for an electric motor option resulted in a truly fundamental breakthrough that solved several aerodynamic puzzles at once. A question John could not receive an answer to in 1978 suddenly had a million of them, and many would quickly receive their due attention as calculations revealed their merit.
John always wanted to ‘sit on the pointy end of a zoomy, go-fast airplane’ and he was delighted to learn that the best class of demonstrator for his subsequently patented technology was a plane that offered all of that and much, much more.
Yes! Our wind tunnel measured over a quarter mile square and 400 feet deep. Testing began in 2007 and concluded in 2015.
There are important rules about how one conducts scale model testing for relevant results, the most important of which concern power loading and wing loading, which scale at different rates (power loading 1:1). Mass distribution and Reynolds number effects must be accounted for. All in all, instrumented testing in the unconstrained atmosphere offers many advantages over the artificial and extremely limited wind tunnel environment.
For Synergy, which reduces wake vortex, one simply cannot have a wind tunnel chewing up the wake vortex thousands of feet before it is fully developed. Boeing learned this long ago and developed ways to test the 747 models outside, on a cable rig.
We’re pretty sure their engineers would have been jealous of our telemetry and RC gear back then.
Mandatory equipment is already providing the technical side of the solution, but we don’t need to invoke smartplane ™ technology to address this concern. Just as one busy restaurant can only feed a certain number at a time, the present volume of aircraft manufacturing would take decades to put a few airplanes at every airport, let alone clutter the empty sky. But for other reasons, there really is not, nor will there be, “air traffic” in the sense people imagine, once we no longer need to concentrate everyone at huge airports.
Most people form their ideas about this topic without small aircraft experience, or with it in a very urban context, or perhaps from a bit of sci-fi movie magic. By the time a few thousand quiet small airplanes start to slowly repopulate empty community airfields one at a time, our perspective will have profoundly shifted away from sprawling airports that concentrate people and planes for “convenience.” Modern flight expands our habitat exponentially, diluting all traffic, and even the urban role in creating it.
Think about it: passengers from all over a five-million-acre region are first funneled to these packing centers (making traffic), then screened and made to wait, so that they can distribute from another such site upon landing into another five million acres of potential actual destination. Why not just come and go directly, to and from wherever? A hub airport hallway is bigger than a Synergy landing site, and can be (or already is) located anywhere.
Taking people directly to and from their closest airfields in a car-like modern airplane makes older concepts of “traffic” utterly disappear. It can be hard to see this at first because the confining 2-D ribbons of congestion on the ground paint a greatly distorted picture in our minds. Pilots escaping the traffic prison marvel at the truth, which is that one can fly all day yet never even see the occasional fellow aviator pointed out on his screen, many miles away. It’s a freedom we dare you to think about, for the good of humanity.
Try this, the next time you’re stuck in traffic wanting your own Synergy: imagine leveling every obstacle, bump, and building for a thousand miles in every direction. Now imagine it all paved as smooth as a tennis court, devoid of cars, and give yourself permission to drive anywhere you want on it, avoiding anything that even looks scary. Now imagine stacking each empty three-million-square-mile-patio you just made, like a parking garage five miles tall. Now…put every car and truck on a different level…and think about how quickly they’d make room for each other anyway, when not confined to a 12-foot wide lane. That’s the networked smart sky, AFTER companies make 100,000 airplanes a year for a thousand years, thereby finally catching up with auto numbers today.
Coruscant will never happen, it’s physically impossible. The earth is far too huge. Simulation studies reveal that even uncontrolled air traffic isn’t a problem, yet soon every aircraft will talk to each other. Our tech industries today are thrilled to provide a proven, pocket-sized solution that can easily handle even hypothetical levels of traffic. Comparatively speaking, autonomous airplanes are a cakewalk compared to self-driving cars. We’ve had fully capable autopilots for decades.
Synergy is working with a number of advanced initiatives for future on-board systems that will make operating your own smartplane ™ the most relaxing transportation experience you’ve ever had.
Although it’s by far our #1 FAQ, unfortunately, you can’t right now. This is a project determined to succeed, and taking orders for high-demand airplanes ahead of churning them out by the hundreds is historically just slow financial suicide.
It’s not about making one, or twenty, or two hundred. It’s about making enough of them, which means knowing what that number is, designing production accordingly, then executing perfectly.
We have an extraordinary plan that eventually gets everyone who wants one a Synergy Prime smartplane, much sooner than if we told everybody what they wanted to hear. It’s a plan every bit as good as the airplane, but equally dependent on time and capital. Our job therefore is to be ready on the business front, ahead of factorial demand created when Synergy flies. We are gathering the team and resources it will take to launch that effort now. Please spread the word.
One aspect of our plan is similar to how Tesla began, but it bears noting that Tesla Roadster buyers at least had a Billion other vehicles on the road, each providing for the same basic societal need. The core mission of ‘moving people quickly and economically’ could be met with many options. For Synergy buyers, however, there is no such thing as time-efficient, on-demand, point-to-point, affordable transportation for small groups of people. It doesn’t exist yet… but a billion people want it to.
If the horizontal tails were wings to make lift, Synergy would be like any other box wing, a configuration showing very little value over the many decades it has been tested. Besides those real shortcomings, though, the answer is that doing the opposite of a box wing turns out to provide dramatically superior results if done well.
For those familiar with the latest non-planar wing configuration studies or the work of Prandtl/Horten/Bowers, some of the underlying theory is old news, but most experts today have no operational experience or practical benchmark for mere theory. Likewise, in the 1930’s, biplane theory left 25% of its domain unexplored; a domain now pioneered by the patentedDouble Boxtail configuration, which combines multiple theories and objectives into new ones, with unexpected results.
Our accurate scale models are dynamically similar, with full scale power loading, so not much is different except that “bigger flies better.” Five to seven seat versions should fly even better than our properly scaled models. Aircraft larger than our 12-seat version would benefit from modified shapes, unless they’re intended to be slower.
Many people are fearful of airplane design, yet think it’s necessary to put a human inside a plane to know what it will do. That hasn’t been the case for decades.
Testing smaller airplanes instead of larger ones is cheaper, but smaller aircraft are especially helpful in design because they amplify flaws. NASA spends millions on it. If you’re curious, the linked paper provides a general overview of how scaling laws apply to the design, test, and analysis of real airplanes.
It makes no difference whether they are manned or unmanned. The most important thing to understand is that the power-to-weight ratio never changes for a properly scaled aircraft. If your target size weighs 12 lbs per horsepower, your smaller ones must also.
Shrinking a full scale airplane properly helps engineers finds hidden tendencies too minor to show up at full scale. Test models are real airplanes that mean life and death to an aircraft program. Many cost millions of dollars to make.
Scale model builders know: a perfectly shrunken popular airplane often flies terribly! That’s one reason why modelers so often overpower them and build them so light. Modelers seldom fly heavy airplanes with very little power, which is what we must do in properly testing our heavy subscale aircraft models.
Our UAVs also provide us a worst-case example for both their drag coefficients and their handling behaviors. It was especially reassuring to investigate post-stall behaviors at high angles of attack without loss of control. When we ‘asked them to stop flying’ by way of extreme control inputs, they comply, consistently and predictably; “falling with style” in a manner akin to Rutan’s SS1. When commanded to ‘start flying again,’ the result was “total control and instant recovery to level flight.” For us, this was an amazing behavior to study.
What we learn aerodynamically, by controlling a real airplane without a human in it, can exceed what is refined later from inside. Dynamic scaling for flight test purposes follows a demanding protocol, requiring the planes to be the right weight for their wing area (much heavier than recreational models) with similar mass distributions. As mentioned, we maintain the same power loading as the larger aircraft will have. Under that scenario, this chart from the linked paper illustrates how ‘deep stall behaviors,’ when made possible, have less hysteresis at full scale.
All of our Synergy scale models fly great already, without lots of power and despite their 100% scale airfoils. Their mass distributions and dynamic similitude to larger vehicles thereby allow direct comparisons. They slow down well and are very stable and easy to fly.
Modelers advanced enough to correctly build similar aircraft from scratch find that they are fun and forgiving. Maybe even a little boring compared to the typical RC insanity that’s possible at model sizes. They also learn that designing and building this aircraft is not easy to attack as a weekend project: even a ‘flat foamie’ model presents an engineering challenge.
So, with the above in mind (and of course many years of in-depth analysis, including full spectrum flight simulation, and CFD studies at full scale/high Reynolds number) we can expect a full size aircraft to be exactly as we want it to be. Early versions met all expectations, from the beginning. Most of the important traits can easily be seen in model behaviors.
OK, so having said all of the above, sailplane pilots and model builders can be a skeptical audience regarding the drag reduction initiatives this aircraft uses. Synergy operates at more than nine times the Reynolds number of many sailplanes, a much different domain of size and speed Those having little personal experience with 300+ MPH airflows, where inertial effects and viscous effects are closer to parity, tend to quickly get lost in what we’re saying.
You see, at model airplane size or sailplane speeds, things like ‘pressure thrust’ and ‘active boundary layer control’make NO DIFFERENCE whatsoever. The air is too thin, the speed is too slow… not by a little bit, but by huge multiples!
Fast model airplanes tend to have a few obvious traits in common, like minimal fuselage size. A fast, ‘conventional model airplane’ is already far faster than a ‘scale Synergy.’
By the time we get to airliner sizes and speeds, the skinnier shapes actually start to work out again (!) reinforcing the conclusion that nothing need be different in between. However, at mid-subsonic speeds, the air hits a plane more like water. ‘Skinny’ shapes actually create a drag problem until you go fast enough… in fact, to get through the ‘sticky’ range of speeds efficiently, conventional airplanes resorted to blasting through as fast as possible, using a lot of power. (They succeed, but that is what the present opportunity space is all about.)
Ideally, a body in this domain would have a length to width ratio just under three to one.
Lutz & Wagner, Stuttgart
Efficiency in the 200-400 MPH range really is a foreign realm that prior designers have not mastered, and the shapes required are different than those that work at slower and higher speeds. The basics implied by the chart above have been known for over half a century, but we haven’t had good ways to follow what it teaches until now.
Thanks in large part to the experimental value of actually flying REAL airplanes in the REAL atmosphere, Synergy leads the way in getting the physics of this new frontier just right.
Our models have also shown that it will be a long time before ‘how Synergy does what it does’ becomes common knowledge. Principle-driven, algorithmic drag reduction is a new field in which we have many unpublished and proprietary advantages.
One is our subscale flight modeling. It provided rapid, accurate analysis and invaluable insight, even though in the words of our test pilots it was already “such a creampuff” and “a dream to fly.” John can’t wait to get his largest one airborne, and we can’t wait to ride in it.
Synergy is an amazingly stable aircraft. For many that’s apparent when watching various models fly. Pilots of our prototypes report that it’s like a sled on rails. But because people are more used to long-tail airplanes than the more efficient physics that birds use for stability, the question comes up anyway. Synergy designer John McGinns has been granted two US Patents about creating drag reduction through increased stability and control. So let’s start from the beginning.
Yaw stability
Synergy has four vertical tail surfaces of generous size, all intentionally loaded (flying at an angle of attack) so as to actively stabilize the aircraft in all directions, even when flying straight ahead (less hunting or tail wagging). These also direct the airflow where it will cause a drag reduction. At the wingtips, the loading counters wake vortex. At the boom tubes, the loading fills the wake efficiently. The ‘vertical tail volume coefficient*’ that results is appropriate for a pusher. Stable! (A tractor prop is destabilizing, an aft prop is stabilizing.)
However, even the need for yaw stabilization is already greatly reduced. Because of the downloaded elevons at the wing tips and their effect on tip vortex, Synergy is like the ultimate implementation of the Bell Shaped Lift Distribution that makes the best flying wings. Negatively loaded wing tips bring difficulties for many wing-only designs, but having the BSLD negative load placed above and behind the tips- on a controlled airfoil- well that’s just nifty. Synergy is so stable in yaw it may not even need the vertical surfaces it has (so we put them to work in other ways.)
Pitch stability
When reminded that many tailless aircraft, such as hang gliders, have a swept wing planform like Synergy, many people recognize that we’re already set up to be quite stable in pitch. Swept wings like ours don’t necessarily even need a tail. Their stability comes from the lift distribution, center of mass, and the pitching moment of the airfoils, and it’s all easily achieved on a swept wing.
Straight wing airplanes…not so much. Their wings are usually inherently unstable about the pitch axis.
Ignoring the fuselage, then, Synergy might be regarded as a stable flying wing, in which we’ve added a very large pair of tails… AND, fly them with an intentionally stabilizing, significant download (7-8% of vehicle weight!)
Our ‘horizontal tail volume coefficient*’ is also quite conservative, due to the large size and aft location of these horizontal control surfaces. (*Tail volume coefficients are numbers used to express the relative ‘aerodynamic leverage’ of a tail surface. They allow engineers to quickly compare apples to oranges among very different designs, where Synergy ‘s numbers have plenty of company among noteworthy safe airplanes.)
Next, an aeronautical design principle called decalage teaches that the difference between the incidence of the wing and the tail has a big influence on the quality of pitch stability. More decalage (more difference) equals more stable, less decalage equals less stable. Synergy has more decalage than is common for a long-tailed airplane. Our tails interact with the source of the forces that a long tail tries to resolve after the fact, moderating them directly. Finally, in a long-tail airplane, the tail and the wing hit gusts at slightly different times, the delay causing the tail to amplify the resulting disturbance by inducing greater angle change. In Synergy, bumps are less amplified, and there is less ‘weathervaning’ due to crosswinds.
Finally, rather than comparing to short-coupled straight wing airplanes, consider that Synergy is interactively coupled. Swept wing and swept tail work together to shape the pressure distribution between them, giving a noteworthy advantage no conventionally tailed aircraft has had before.
Prototype test pilots all agree, it’s “such a creampuff” that their only disappointment is not getting any bragging rights. One said, “I was expecting it to be more touchy, but it flies like a trainer.”
Ouch. So far, every form of analysis and testing says we are naturally convergent and well damped, and we have plenty of ways to tune system behaviors for our preferences later. Ground Vibration Testing and future aeroelastic tailoring will help refine these patented methods to provide stability and efficient control while simultaneously reducing the penalty of induced drag.
Connecting the aft horizontal surfaces by means of a horizontal connecting airfoil is an option described in John McGinnis’ ‘boxtail’ aircraft design patents. Many people imagine it would make things stronger and lighter, but it turns out differently.
It’s true that connected-box-wing designs are what people are more used to seeing, since ‘box wing’ and ‘tandem wing’ aircraft concepts have looked that way for more than forty years.
However, it’s worth noting that box wing designs have not become successful during that period. The ‘connector wing’ is, frankly, part of the reason for that. It causes more harm than good.
An airplane wing flexes up and down in turbulence, which can improve the ride and help achieve structural optimums. Making it stiffer requires ever stronger materials, which costs money or adds weight, or both.
Now when we attempt to brace a flexing wing, all the force that makes it flex in the first place is still there. Any bracing scheme just makes that force go somewhere else.
This is a very important concept to understand, because when one wing or tail is above or below another, using one to brace the other through rigid vertical supports (without diagonal connections) requires a corner connection that is very stiff and strong. This type of corner connection receives the ‘moment load’ we can visualize below, and it will fail under that load unless it is either extremely strong or extremely flexible. In the latter case, any bracing benefit from the connection is lost, and in the former case, the structures needed are excessively heavy in comparison to merely building the wing stronger in the first place.
In a boxwing design, much of the moment load normally only seen at the wing root also goes straight into the corners of the box at the wingtips. You can visualize this by removing the ends of a cardboard box to form a parallelogram representing the left or right half of a boxwing aircraft. Look through the opening and visualize the upper and lower “wings”, “winglet” and “central plane of symmetry” while holding the central “fuselage side” of the box. Now, flex the “wingtips” up and down on the “winglet” side. The corners fold easily (and would have to, even if they were stiffer.)
Synergy has, instead, a double boxtail design that allows the wing to flex and for the loads to be distributed without excessive concentrations. The tail is naturally holding the wingtip down, while the wing is naturally holding the tail up (against the downward load of the tail) …but both can flex together with the wing. This creates a system in balance with itself and reduces connection weight in comparison to a centrally connected rear wing/tail.
The short answer is yes, but we are not willing to go into much detail concerning which systems are being researched at this time. The basic idea is that many deicing schemes destroy laminar flow. That is an unacceptable result, because it is clear that many anti-icing schemes are compatible and complementary with laminar flow. Our strategies do not accept aerodynamic or safety compromises.
The longer answer, which may strike some as controversial, concerns why anti-icing in the future has a different priority than has been the case historically. Let’s be clear: any kind of scheduled air service or flight to a rigid time and place demands that an aircraft have ‘flight into known icing’ capability (FIKI). It’s always a good thing to have. However, while companies race to develop such commercially valuable aircraft, society’s broader adoption of affordable personal aircraft will be quietly moving the target. It will not be quite as important for the majority of future aircraft.
Air travel as it stands now is an out-of-control monster. Billions of dollars are spent on the sprawling ‘cities’ required not only to land and load our giant Air Busses, but to process the hordes who have to spend several hours getting to and through them, at times that are very inconvenient to start with. Yet extreme punctuality is key, or it just gets worse. For scheduled GA aircraft, which currently lack the speed, economy, and range to provide a financially sound alternative to the hub-and-spoke regional transportation system, FIKI is even more safety-crucial.
However, when people gain control of their travel options, as they have with their cars, they will not choose to fly in bad weather. When they are flying and discover it would be nice to take a potty break, grab some lunch, and take in a cultural experience somewhere off the beaten path, rather than proceed into worsening conditions, they have the option to do so because there are beautiful little airfields almost everywhere. For the majority of such uses, Synergy’s most basic level of ice protection will provide safety and peace of mind because its performance and range allow unscheduled travel to and from anywhere.
Yes, John McGinnis and Team Synergy volunteers post updates several times per year on the Synergy Aircraft Facebook page. An album related to the build is here.
Yes. A large number of tests have now been run using Large Eddy Simulation for the v.32 aircraft in both the powered and non-powered condition. The results of all tests are very exciting, and have confirmed our success in areas that are more difficult to validate using conventional methodologies. All expected performance capabilities appear to be well in hand, and basic qualities have long been well understood through unmanned developmental flight testing.
Our numerical simulations confirm that Synergy has the expected drag numbers: small enough to start a barfight in Carmichael’s famous Laminar Joint.
What little remains occurs in areas we’ve designed to benefit from the use of power. Its beyond-the-textbook design principles have now been qualitatively AND quantitatively validated, and that approach was perhaps the most significant of our technical risks. (When we completed the design to the level required to start building it, the cost of this level of analysis was much greater than the cost to complete the first full size aircraft.) We have now reduced these capabilities and principles to a “next generation” algorithm for greatly enhanced conceptual and preliminary aircraft design.
We’ve also created such a powerful resource… world class, in fact… that it IS possible to test all of the things aircraft designers dream about. We’re doing it, and can do it for anyone else, too. Details here.
Probably. By the time most people see new developments in aviation, engines, or technology, those working inside the industry have known all about it for years. Of course, every once in a while something will stay truly secret for good reason, surprising everyone when it arrives.
We get a ton of emails from people watching the new developments closely, and we appreciate it. Naturally, most are late to the party, however, so this FAQ will be updated from time to time with links to some of the other cool things going on out there while we’re busy.
It doesn’t mean we endorse it or agree with it, or even that we think it’s worth a look. There is a lot of stuff happening these days, and some of it needs commentary!
Sure. Right now, DBT Aero, Inc. holds the patent IP and is focused on efforts to commercialize a specific family of the many patented BoxTail aircraft types. We’re also able to consider licensing rights to others, especially for other aircraft, such as business jets, UAVs, etc. (Why should they?) A related technology for stability and control through induced drag reduction applies to more conventional wing and tail designs, as well.
Since any aircraft requires such a focused commitment to development, there is ample room for other companies to establish market category leadership through patent licensing, with or without category exclusivity (which is a possibility). Any company seeking to develop aircraft under license may contact the company for a pain-free licensing experience.
Requests for aeronautical design and development under contract may be considered by us directly, or could be sourced through our partnerships with service providers.
We’ve completed and flown many prototypes, using the most proven method; one that tends to reveal and amplify any negative inherent traits. Sub-scale aircraft development is how virtually every aircraft is tested, because big planes are easier in terms of improving the basic character seen in smaller models (that are underpowered and overloaded compared to recreational R/C airplanes). This process has removed many technical obstacles, allowed development and testing of full scale systems like landing gear, speed brakes, and wing removal, and is now mostly complete.
As to John’s full scale aircraft, we don’t know yet. A huge amount of the work has been done, and what remains is well in hand. However, it is quite expensive. Our 2016 timeline was half funded by profitable operations, but the second half was not, nor has there been enough cash available for him to preserve the 2017 timeline. Assuming we raise ALL the capital required for our business plans, we’re presently less than a year from flight of his or other prototypes.
The Company has a bigger agenda and more options as we go forward. In fact, we will be making short-run molds from John’s parts before they are assembled, which is part of the reason they cannot be joined together for the sake of showing progress. A few Alpha prototypes will be built from those molds, and having worked all the details out, they will build fast. Completion of one or more of them could theoretically occur ahead of the original, then we will submit them to extensive testing and analysis.
Beta prototypes built from production-candidate tooling designs will be the first planes a member of the public could obtain, but we expect a bidding war until we go forward with a production timeline and product announcement. Our goal is to be the first aircraft company to deliver affordable aircraft in adequate quantity to meet demand, and we’ll share the details on how that can be achieved…sometime ahead of creating even more demand.
Don’t worry: No one will miss the news when Synergy is ready to go.
Yes, Synergy is intended to become an incredibly easy-to-build kit aircraft while we work to bring it to you in certified form.
Kit aircraft are certificated one at a time by their builders, whereas completed, ready to fly airplanes require a ‘type certificate’ and then a production certificate. These rules have been improved for a shorter process, and all varieties can coexist while the work is done.
Obviously, the goal is to reach production certification, and we’ll use the experience we gain operating in kit production to empower our certification efforts in a separate undertaking.
From a strictly business standpoint, it is very unwise to ignore the kit market.
Kit airplanes represent about half of the new aircraft completed each year (!) and they can be (and often are) a flying showcase of the most advanced technologies and safety features available.
They’re not necessarily daunting projects, but ours will be downright easy. We will have a program to assist anyone to complete their aircraft in a Synergy build center, starting here with us.
The Glasair Sportsman is one of the leading fast-build kit airplanes.
Although newbie airplane companies sometimes rush off headlong into spending hundreds of millions of dollars, racing to certify processes and parts that aren’t even finalized, and shouldn’t be, it’s long been clear that the kit market provides the very best path to lower costs, lower risks, and a thoroughly refined product offering.
By harvesting the collective brilliance of the industry’s most passionate craftsmen, engineers, businessmen, and aviators while operating profitably, our Synergy kit products will advance only the most proven methods and processes.
Documenting everything necessary to speed an FAA-friendly aircraft through to commercial certification requires time and a stable process, which is why the positive cashflow and much lower risk of the kit market supports higher growth toward mass production.
An aircraft built from a kit can’t be used to make money or fly passengers for hire, but its owners can basically use it with the same and greater freedoms otherwise. However, due to Synergy’s economy, capabilities, and configurational potential, we expect to be on the certified aircraft trail in parallel, from the very beginning of kit production.
Ultra-quality fast-build kit planes are the way to get started today, and when the market wants so many of them that low cost and certification of complete airplanes can be an industry-invested result with a reasonable timeline, everybody wins.
No, they flow from classic methods including 2-D flow solvers, spreadsheets, proprietary analysis, and panel codes. The excellent results were highly consistent and are backed by scale model flight test. Recent high-end CFD assessments using Large Eddy Simulation have, however, further confirmed all statements both qualitatively and quantitatively. None of the early work attempted to validate any active drag reduction measures, just the passive results of natural laminar flow etc.
Especially with recent CFD validations, including under power, we greatly prefer to first publish actual flight test data at full scale, rather than merely fuel further debate over calculations involving open thermodynamics. We are happy with the numbers. Just like every ‘active drag reduction’ experiment to come before it, Synergy challenges the industry’s conventional wisdom regarding preliminary design calculation.
By analyzing the pressure and velocity distributions required to maintain an attached boundary layer. Natural laminar flow is relatively easy to achieve and quite well established today, although many myths persist. Powered ‘boundary layer control’ makes it even easier to achieve, but the benefits are minimal for the speeds where the most research has been done. Its ideal application is to small airplanes at mid-Mach numbers, not the sailplanes and fighter jets often used for testing the concept.
Pioneering work by August Raspet in the 1960s showed that up to 100% laminar flow is easily achieved at general aviation Reynolds numbers if one is able to use power. Suction, applied to perforated wing skins at a rate of 0.0137 horsepower per square foot of wing area, provided laminar flow on turbulent airfoils and very high maximum lift coefficients, on full scale aircraft.
Like many others, our custom ‘natural laminar flow’ airfoils have a very flat pressure and velocity distribution, easily maintaining laminar flow up to 60% of the wing ‘chord length’. Suction is applied beyond this point, which not only stabilizes the boundary layer, but through our proprietary technology, creates ‘pressure thrust’ to result in extremely low drag. We use a number of commercial grade airfoil analysis codes to compare similar airfoils having flight test data, as well as high-end CFD.
There are several reasons why prior boundary layer control initiatives failed commercially. First, aero research at the time was all about transonic flight and very large airplanes, where it was hard to achieve and not helpful. Second, some aspects, such as contamination, water entry, maintenance, and so forth, require significant effort to address. Third, dependencies can be created, in a powered lift system, that create both real and imagined safety issues which must be understood, respected, and mitigated. Fourth, airplanes that could use it really weren’t changing, and it didn’t adapt well to old designs. Finally, a push toward blowing, rather than suction, goofed up the ability for designers to capture what they’re really trying to do, in physical terms.
Today, powered BLC is seldom seen as the easy recipe that it is. Much emphasis is given to using specific ‘proven’ details of hole size, pattern, placement, and so on, without insightful consideration of the simple physics of pressure gradient. Thus the attitude: active laminar flow is complicated and expensive. Probably not worth it!!!
Synergy does not require active flow control to achieve its potential, but it does demonstrate its value.
Definitely. In both Single Stage To Orbit and aerial launch to space, aerodynamic drag is a major design factor. To focus briefly on the comparative relevance of Synergy toward the WhiteKnight/SpaceShip One model, it can be seen that a successful mothership vehicle requires attention to low induced drag, high strength, light weight, and high payload capacity. Uncomplicated twin fuselage design is also helpful.
For the reentry vehicle, favorable wave drag and transonic behaviors; short, strong wings; and control under high-alpha deep stall conditions are required.
In all of these respects, Synergy introduces new and useful solutions. High span efficiency and greatly reduced fuel requirements allow designers to imagine much higher achievables than allowed by prior technology.
No. The presumption of inherent loss due to swirl is an artifact of early math. Fluids swirl. The objective of Synergy propulsion is minimum enthalpy mass flow. For wake props in particular, an unimpeded, lightly swirling propwash displaces a tapering column of airflow efficiently downstream of the aircraft.
Along the same lines, counter-rotating props are frequently suggested, and we likewise find against it. The best reason to accept the noise, weight, complexity, liability, and inefficiency of counter-rotating props is to mitigate the extreme torque of a high-horsepower, tractor-mounted piston engine. Synergy is a very effective way to counter torque: elegantly.
Yes. None of our performance claims depend upon having Oswald efficiency greater than one. Flight simulation has typically employed a highly conservative Oswald e = 0.985. Our actual true span efficency is, like many real aircraft with optimal loading and nonplanar wings , much higher than 1. Kroo, in reference 5, summarizes wake-based studies confirming values of e reaching all the way to Prandtl’s theoretical limit of 1.47 for a wide range of nonplanar forms. Though often confused with span efficiency, and (incorrectly) used interchangeably, Oswald efficiency is based upon the teaching that elliptical loading is the only ideal, whereas for nonplanar configurations this assumption is false.
Defined on the basis of span efficiency and aspect ratio, K = .0307. K reaches similar values using either e = 1.46 or AReq = (bs + .45bh + .45be )/ Cavgwith e set to unity.
At cruise Reynolds numbers, without active BLC or propulsive influence, X-Foil and other 2-D analysis codes yield fuselage Cd = .0026, wing Cd = .0026-.0036, and stabilizer Cd = .0045. Since these values reflect natural laminar flow beyond 62% of chord, expected Cd for the 100% laminar flow condition is actually less than the conservative .0020 polar minimum used to calculate our suction BLC condition. Confirmed values of .0008 to .0014 have been demonstrated experimentally by Pfenninger and others.
Preliminary calculation of an aircraft is where many designs go wildly astray. There is an explicit assumption buried in the equations used since the first decade of the 20th century, and for many conditions in the domain where viscosity and inertia are equally implicated in the creation of drag (small aircraft at Mach 0.3 to 0.5), this assumption has been shown to be totally invalid. In the case of Synergy, however, experimental and 3-D CFD testing have revealed that using this conventional approach was conservative.
Synergy clearly promises the largest practical fuel economy breakthrough in history. Its architecture correctly and intelligently integrates many proven technologies, each having a huge impact on power requirements and fuel consumption. The design supplies strength, safety, and manufacturing economy without complexity; while eliminating trim drag and cooling drag.
Now that a full suite of assumption-free, power-on tests have been concluded using the most powerful fluid dynamics software on the planet, it is clear that we nailed it. Real-world atmospheric flight testing using large, subscale UAV versions (that amplify undesirable traits) further eliminate surprises. However, this level of clarity is not available to a room full of outside experts, nor typical students of classical aerodynamics.
As reviewer George C. Greene put it (FAA Chief Research Scientist; NASA Langley, retired), “the thing that makes it so hard for me, and probably for others, is the synergy. You are doing so many things (well) at the same time that you have to look at all of them (together). And when you talk about synergy, as you know, they don’t add in a linear way as most classical aero stuff assumes… I don’t think I could put the pieces together the way you did – that is true insight.”
Not yet. Synergy designer John McGinnis is a Senior Member of the AIAA. Several technical papers are in the works for publication after full scale flight test.
These principally concern novel and proprietary aspects of integrated propulsion that are not yet public, such as suction details and wakefan design. The ‘will-it-fly-well’ aspects have been well established in the conventional manner and are taught in the published and pending patents. Dynamically scaled (unmodified v.18 full scale geometry) electric models have been flying under appropriate low power loading for several years, and extensive CFD work has been carried out.
Long before Synergy’s first public unveiling, more than a dozen respected aeronautical authorities received an early look at Prime versions 18-23 under formal confidentiality agreement. Their opinions, while not purchased for publication, were overwhelmingly positive.
First reactions varied initially, as nearly all failed to grasp that Synergy was not ‘another box wing,’ nor that there might be hidden symbiotic benefits to discover, such as the absence of interference drag. However, upon more thorough review of the design details and relevant studies in the literature, all but one eagerly agreed that the premise and its execution have significant merit. No one raised any issues not already considered, and the informed consensus was that the work will succeed and will speak for itself.
Since our unveiling, popular acclaim has been universal and criticism highly polarized, mostly because so little can be evaluated without pursuing the matter in great depth. Negativity requires neither effort nor understanding, and is fueled by the same human factors that block progress in all technical endeavors.
Extreme interest is continually expressed for getting the full scale (v.32) prototype airborne! Most engineers can’t add anything to the body of research we have obtained to date without it.
Yes, although a better choice would be a small, multiblade turboprop or unducted turbofan, in terms of efficiency and in keeping with the quiet advantages of the concept. Other engines are also possible, but the configuration is not highly suitable for use with air-cooled engines. This intentional bias may help advance the use of liquid cooling in aircraft.
Originally, John intended it to be electric powered, which is how every detail came to be scrutinized and the aerodynamic breakthrough occurred. High torque electric motors, whether pure electric or hybrid, are the preferred eventual powerplant for Synergy designs. Hybrids provide the unique opportunity to lower the risks associated with the use of low-cost, high-volume automotive engines.
With regard to jet propulsion, Synergy supports a host of new technologies that will allow the advantages of a jet without many of their drawbacks. Old ‘reaction thrust’ jets are obsolete.
No kits will be offered until they are real, and that will take a long time and a lot of money. The answers are driven by things that happen after a presumably successful flight test regimen, followed by capitalization, production development, and production flight test.
It is rare to have the opportunity to influence such things fundamentally and at the ‘systems’ level. So, given that we know how much it costs to build similar aircraft using less efficient methods, we can confidently predict that it will be possible for Synergy to substantially lower the cost of market entry. However, it won’t start off that way, given the demand and Synergy’s expected capabilities. Still, early adopters will find the price highly attractive and competitive, and costs will drop when production hits its stride. Our goal is always to offer unmatchable value.
Synergy has an empty weight of 1650 lbs, 200HP, and 156 sq ft of wing area on a 32 foot wingspan. Casual use of these numbers would be misleading, however, because of our high span efficiency, laminar flow fuselage, and powered lift / powered drag reduction system.
Synergy will offer high performance at both ends of the speed spectrum, but specifications won’t be used for marketing purposes until they have been demonstrated in full scale atmospheric flight testing. More details are found on the technical info page, and with formal non-disclosure agreements we can share more detailed information with prospective partners and collaborators.
We are on track to produce certified and builder-constructed versions of a highly refined airframe design. Once we’ve done so, many other versions may become possible.
However, the size and shape of Synergy’s fuselage is not about a certain number of seats, but rather is a function of fundamental aerodynamic opportunities at the speeds we targeted. Thanks to extremely low drag, it does not need to be smaller, as it is already light and slippery.
Synergy with one or two seats filled will easily outperform most two seat aircraft on the same or less fuel flow. It’s also smaller than a Cessna 172 in terms of hangar footprint (L,W,H) even though it can seat six without anyone touching anyone else (!) Yes, it fits fine in a T-hangar.
Our Deltahawk diesel engine has already shown a 4 GPH cruise in the Velocity aircraft at 146 kts. We can do better than that. At the high end, and on other powerplants (8-24GPH ), well, we’re not saying, but air race records will be shattered.
Some kit builders will like it as a one-to-three seat air camper with a pickup bed in back. The biggest single-pilot market initially is for certified air cargo versions, along with a derivative for air ambulance usage.
Actually there are already THREE places where we can fly the airplane from, and all of them have a fabulous view.
There is side by side pilot-copilot seating, with a choice of control configuration, right behind the front seat. The left seat is usually where the pilot in command will choose to sit, when there is more than one person aboard. “Solo” can only be flown from up front, but “dual” can be flown side-by-side OR tandem.
You can also have one instructor with two students, or a VIP passenger up front. (It’s hard to tell the first side-by-side seats are pilot locations in some pictures because the back instrument pylon isn’t visible yet and the controls attach to the wing center section, still being built.) Some people will prefer two seats up front instead of one; it’s an option.
Synergy offers side by side and tandem pilot seating. Solo is flown from front seat only, but passengers can sit there too.
There’s a fourth pilot already, as well. Our autopilot has an emergency auto-approach to landing interface using technologies to safely and automatically put the airplane on the safest available runway by simply engaging the autopilot system (literally, pushing the big red button). Many new features along these lines are already in the market or shortly available to help power the semi autonomous smartplane revolution.
If landing isn’t looking too good for some reason, a pull of the “big red handle” will deploy the ballistic airframe parachute, a very proven technology.
Many other safety features are designed right into this aircraft from the conceptual level onward, including energy absorption, stall resistance, and outstanding low speed handling. The latter two involve a most remarkable, patented ability to avoid stalls and spins, the number one cause of GA accidents. Should one insist on having that capability, Synergy further offers a patented ability to recover instantly from a fully stalled flight condition. You can read more on this feature here.
Although it reaches unprecedented speed on only 200 HP, let’s just say that Synergy is faster than we need to assert at this time.
For safety reasons, our service ceiling is 25,000 ft, but in simulation we’ve flown far higher. Our ‘low induced drag’ advantage especially shines at high altitude, yet our ‘active drag reduction’ means you don’t have to climb high just to go fast or gain economy.
Interference drag occurs when the interaction between objects moving through a three dimensional volume creates unfavorable pressure and velocity distributions, resulting in turbulence. The amount of turbulence that can be created at intersections between wing and fuselage, and wing and winglet, for example, can be surprisingly high. Knowledgeable reviewers of the Synergy conceptual design (shown in early work without a wing fillet) are therefore quick to point this out.
However, shaping these elements is a critical design task. Rather than blindly implement the usual wisdom, which oversimplifies, we strive to work the problem parametrically in 3-D. This approach eventually yields a superior result, without compromising wing placement, or detracting from the propulsive potential of the fuselage in pressure thrust. Due to a nearly ideal volumetric displacement and laminar flow, we also have a more tolerant condition than meets the eye.
Early on, wing-fuselage interference was intended to be captured for cooling. Later optimizations allowed a cooling thrust design, so a preliminary fillet was designed around high-recovery pressure thrust attributes. This feature will be highly refined for the final product.
With continuity of higher pressures on one side of the airfoils and continuity of low pressures on the other, Synergy doesn’t create the kind of conditions that cause ‘interference drag’ (which is really just a catch-all term for unanticipated turbulence.) The intersection of our airfoils is also optimized to provide minimal shed vortices, which is likewise a symptom of discontinuity. Our approach goes beyond a blended winglet design in favor of a temporally optimized volumetric displacement, a true 4-D solution.
There is a LOT to learn about this counter-intuitive design, but the most obvious thing about Synergy is its distinctive tail configuration. It’s a technology that could give any well-designed airplane a fundamental advantage.
Our underlying breakthrough is our founder’s patented technology for high span efficiency through stability: using the tails to help the wings make less drag.
Every airplane has a wingspan, and a weight. More span efficiency means that ‘a given wingspan’ will work better at a given weight, up to 32% better than a normal wing. Unlike any normal wing, including tailless ‘flying wings’, the Synergy configuration can reach the minimum induced drag for its wingspan and weight.
As weight increases, such as for an electric aircraft, more payload, or longer endurance, the advantage of high span efficiency increases exponentially. It especially helps planes that have to weigh more, or fly higher, or slower, or maneuver efficiently under G-force loading, such as airliners and racing planes.
Synergy’s Double Boxtail (DBT) configuration (US8657226, 9545993) is a broad technology that benefits slower and heavier airplanes even more than it does ours.
Yet because this arrangement is more suitable for high speed flight than longer wings are, DBT 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 configuration to allow a car-like passenger plane…of affordable horsepower…to reach the previously unattainable speeds where these initiatives bring exponential new benefits.
Our name is not a buzzword. When taken together synergistically, these drag reduction 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. Its 3-D span efficiency is 1.46 times that of a normal wing of the same span, in a strong, compact form more capable of higher speeds than a long, glider-style wing. Lowering 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 because none of our simple, seamless flight surfaces have any controls or spanwise gaps in them. Two moving surfaces provide a majority of flight control. Like a flying wing (which is a less efficient configuration than DBT), pitch and roll controls are combined. We don’t have separate elevators and ailerons; our two elevons are just simple, one-piece airfoils, supported at both ends and 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 25% scale model doesn’t even have rudders. Two simple surfaces provide fully coordinated turn control.
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 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. The twisting tendency of a swept wing is balanced out of the system under G-loading by an always-proportionate, opposing downforce from the tails.
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. Synergy employs conventional stall prevention, in that its controls can provide full authority without ever creating excessive wing angle of attack. In other words, the aircraft won’t even stall at all! However, we’ve tested stall behaviors anyway, with controls set to allow that authority, and discovered another amazing benefit: recovery from intentional stalls is 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 than the area ruling used for supersonic aircraft. Its objective is to promote stable near-field pressure gradients in all phases of flight, drastically reducing the true source of catch-all “interference drag” and turbulence. 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, or because of mistakenly applying Whitcomb’s area rule to a subsonic airplane. Thus, today’s conventional wisdom tends to ignore subsonic volumetric tailoring entirely. (Nature, however, doesn’t, and this is part of the reason we can often accurately associate high efficiency with the volumetrically-tailored beauty of fast marine life and birds.)
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. Every wingtip or stabilizer tip is a drag source on an airplane. There are no wingtips on Synergy.
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 economical 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.
