C Ommuniqué Issue # 3 Volume # 1

Transcript

Communiqué Issue # 3 Volume # 1 Low aspect ratio aircraft Part 1 Education Feb. 28, 2006 Photo from PS Magazine Dave Lauridsen Barnaby Wainfan’s full-size Facetmobile sits in pieces behind him. This radio-controlled version of the 2 seat Facetmobile, the FMX-5, sustains him while he slowly rebuilds the crashed prototype. DG2’s third speaker was Barnaby Wainfan. I hope Mr. Wainfan’s spirit and structure was captured in this following write up. He captivated us with his humor, opinions, theories, ideas and reflections of general aviations future. His vision for general aviation covers the spectrum of cost, performance, utility and a remarkable stealth fighter looking aircraft. Some say that in theory, there is no difference between theory and practice. But, in practice there is usually a difference. That’s where Barnaby Wainfan merges his talents to understand and practice these differences. Mr. Wainfan has fully participated in his theories. He built and flew an aircraft based on his theories and visions. Placing him in the special category of individuals many of us would like to be, dreamer, designer and builder. He speaks from personal accomplishment and knowledge. This makes a very significant statement about Mr. Wainfan’s opinions and assessments about low aspect ratio aircraft and how they fly. Mr. Wainfan did not just bring an aircraft design but insight towards a look ahead of current practices and technology, towards what might be. Looking directly at what it will take to make general aviation profitable and successful to a larger group of individuals. Will his vision be successful? Maybe not immediately, but general aviation needs free thinking visionaries like our early aviation pioneers. With out individual inspiration trying to move aviation forward, greater effectiveness will not happen. Many past ideas which where long shots in many individuals’ minds helped move aviation quickly to the forefront of technology. Wainfan’s Facetmobile is a total package idea encompassing cost, technology, and general aviations possible future growth for individual sport pilots. Most individuals find it impossible using their own money to buy a new aircraft within their desired specifications. Contrary to what aviation magazines frivolously (or thoughtlessly) call affordable, most people will not or can not afford to pay more for a plane than they have or will pay for their house. Are you not frequently dumbfounded by how surprised aviation magazines are by the declining General Aviation sales? In 1978, piston aircraft manufacturers in the United States had a record year, with shipments of 14,398 airplanes. It had been the best year for general aviation in the history of the business, and few had anticipated the dramatic downturn in the light aircraft industry during the 1980s. General aviation industry suddenly experienced a free-fall drop in sales. By 1986, Cessna stopped making single-engine personal-owner planes altogether, and Piper filed for Chapter 11 bankruptcy. By 1990, the industry only shipped 608 airplanes and it appeared that the general aviation industry would disappear from the domestic scene. There are lots of reasons and many theories about what has happened to cause this. 1 The reason is very obvious to Mr. Wainfan. Keep the price at the level of a luxury car while having acceptable performance and you can sustain a GA production line. With that comes used aircraft that drift down to others who can not afford (or unwilling to pay) the new price. He made a valid point with historical data. Showing that once an aircraft gets priced over a mid luxury car, sales fall and at 1.5 times that price the market collapses for that new aircraft. Buying any aircraft brings a cost verses performance dilemma. The aircraft that most people can afford will not meet their performance desires. A lot of performance requirements are more wishes then requirements. Wainfan’s solution, make the aircraft fit a mission profile with acceptable performance for sport aviation and you might have an acceptable design. Look to what has sold in the past in suitable numbers for ideas of what will work. As Barnaby Wainfan stated “Nobody builds a lot of a bad aircraft” He also sited easy handling and pilot protection as a high design consideration. You got to build a safe aircraft for the 50 hours a year flyer. Because, killing pilots is bad for business. Make it pleasant to fly and when the pilot does something dumb, you want it to take care of the pilot. “The aircraft has got to save the pilot, cause the pilot can not save the aircraft”. You want an aircraft that will not stall or spin with a “SPLAT FACTOR” that hits the ground flat and slow. Low aspect ratio aircraft are good at this with the safety of no spin and stall when designed correctly. His Facetmoble fits these qualities. bouncing past ahead of him. Mr. Wainfan then concluded, “Any time parts of the aircraft leave formation things are not what they should be”. Mr. Wainfan’s aircraft was equipped with a BRS parachute system. He did not need to use it during the power failure but was prepared to. He spoke very highly of the system and its designer and knew personnel of two incidences in which it had saved lives. The system is not a totally foolproof as history has shown, no system can be. Which allowed Barnaby to produce Wainfan’s Law “For every foolproof method (system) that exists; there exists an equal and opposite fool”. Nothing revolutionary has driven the cost of small General Aviation aircraft to a reasonable level, or performance up to exceptional levels. Composite where thought as a way to bring cost down. This did not really work because of labor cost and not seeing that each ply was counted as a part when assembling. Legacy aircraft where designed when labor was cheap and material was expensive. Labor can account for 25% of the cost just to drive rivets in some aircraft. NASA is even studying the 1940’s SeaBee to find how it was built to reduce cost. (See Write Up) Cost of production comes at you from many areas, parts, tooling, complexity, labor, etc. You might have to look at a revolutionary design to bring cost down. Mr. Wainfan did just that. He built something radical with the help of friends and family. This was possible because he had to answer to only himself and his wife and not bunch of other people. As a foreign visitor who saw his FacetMobile told him “In America anything is possible”. This is where Barnaby Wainfan juggling act with the many aspect of FacetMobile concepts and Low Aspect Ratio (LAR) design comes together as a revolutionary but viable design. Using flat panels in a Facet type design allows the use of manufactured panels. The flat panels are not as efficient as smooth contours on an aircraft. It is only costing you about 5% more in parasite drag. But, you do not have to build a mold which you could use as a swimming pool. Barnaby Wainfan’s FacetMobile which made the cover of Sport Aviation magazine. Look at how much room he has in the cockpit; can he even touch the sides? Once again personnel experience from propulsion failure on take off at Blythe airport has proven his theories. He turned back to the airport knowing his aircraft would maintain control as he landed at 30 knots. He made a skillful landing which would have most likely caused no damage, except, for hitting the airport fence. He knew there was a problem when he saw his wheel These panels can be cut with a CAD / CAM automated machines, thus reducing labor cost, lower parts counts, tooling and complexity problems are mostly eliminated. With the premade flat panels you can purchase job shop NC machine time with your tooling on a thumb drive. Basically you can have the panels cut by any qualified job shop. You do not have to buy any expensive machines, only time on expensive machinery. They are then designed to be self jigging with concepts and fasteners technology from space craft design. Accord to Barnaby’s wife you have the IKEA aircraft. Barnaby is working with Cerritos College and building a full outer panel which will go thru load testing to verify these concepts. 2 Low aspect ratio designs seem to have the same reputation for efficiency towards induced drag as the California Department of Motor Vehicle has with motorists. A High Aspect Ratio aircraft like a sailplane has the opposite reputation. Those long slim wings holler high aspect ratio and efficiency. For sailplanes L / D is the all out top issue, designed for total performance. They do their job of staying aloft very well on low amount of energy. But, sometimes you need a glider with LAR to get the job done, like Space Ship One. What this means is you design for a mission, exactly what Barnaby Wainfan has done with the Facetmobile. If you compare the overall package of a LAR aircraft to conventional design you will see an advantage. Induced drag is about more then aspect ratio. It is about wetted area, aspect ratio, and span loading. You must also look at parasite drag which is affected by skin friction. There might be more skin area in a low aspect design, but the drag is off set by other avenues. For one you have long cords on your airfoil, long chords equate into high Reynolds numbers (RE). The FacetMobile has an airfoil chord of about 14 feet which gives it a RE of about 14,000,000. This lowers your skin friction (Cf) down about 20%. Intersection drag is usually lower with a LAR because the wings, body, flight controls blend together with less intersections. When you combine all this together, you have an aircraft which can compete with a conventional design. With LAR you get a light structure. The FacetMobile’s weight was 370 pounds with a useful load of 300 pounds. Light structure reduces induced drag. Fuselage and wings become a total package giving a BIG cabin. By blending the body, wings and control surface you reduce parasite intersectional drag. The FacetMobile had a very tolerant weight and balance and C.G. travel. The 14.5 foot chord allows 15 inches of C.G. travel. Compared with a Cessna 150 which has 3 inches of travel. You also get a safe and well handling aircraft. In extreme emergency, pull the power, pull the stick, keep your heading, and your sink rate becomes about 1000 feet per minute in the FacetMobile. This is servable in most terrain for an emergency landing. the design of future Personal Air Vehicles. The study examines building a low aspect ratio airplane. This report NASA LARC NAG-1-03054 is worth reading. It is very well written and presented. It explains Wainfan’s concepts very well. I might make it an attachment to this newsletter. If not you can find it at this internet location. http://members.aol.com/slicklynne/pavreport.pdf There is hope that he will get a contract to fund phase two of this study. I can not see a better use of NASA funds then this. This concept could revitalize sales and general aviation. Good for sales, technology and American manufacturing. Barnaby Wainfan’s Facet concept could do for aviation what ATV and Jet Ski have done for off road and water sports. Also, I would like to see it take to the air Q/A with Barnaby WainFan Q: By moving the stabilizers inboard do you lose efficiency? A: Yes, a small amount, but by adding few more feet of wing span it works out the same. It is also cheaper to build with them inboard. Q: Did you play with cant angle on the wing tips? A: No, but on the FMX-5 the lower part was moved for dihedral effect. Q: How do you get in it? Barnaby Wainfan’s Facetmobile concept aircraft has safety, reliability and comfort, utility and reasonable speed. Not forgotten is cost effective construction. The aircraft should cost about half of today’s present two place aircraft. In the sweet spot; luxury car area of $50,000 to $60,000 while looking radical and different at the same time. By combining all these attributes he makes it a meaningful and reasonable proposition for aviations future. A: This is a problem. In the FacetMobile you get in through the bottom floor between the seats and rudder pedals. The door opens up and you go through the bottom. Future design might call for a plug door with retract steps. Doors on the bottom are great for working on the panel and other areas as you stand on the ground. In 2003, in partnership with the California Space Grant Foundation, Barnaby Wainfan won a NASA contract to study the application of Facetmobile low aspect ratio airplane concepts. This was to A: Similar to conventional aircraft. As you drop the Aspect Ratio down the slope of the lift curve gets lower. This means change of lift coefficient per angle of attack gets lower. So a given gust Q: How is it in gust and turbulence? 3 changes the lift coefficient less. Even though you have more area it comes out about the same. During turbulence there is a weather vaning effect. The effect on the two place with a wing load of 5 pounds per square foot wing load it will act like a Cessna 150. Q: How about cross wind landings? A: You have to work at it, but it has a lot of rudder power. It does want to point into the wind. The Facetmobile has landed in 12 knot crosswind with not much problem. You do not get the rolling effect as in a long wing conventional design. The landing gear is set for a negative lift with the nose wheel down. Slip it in, fly the gear down to the runway and use lots of rudder and brakes. Q: Stall effects? A: Similar to a canard aircraft limiting effect. Q: How high off the ground are you when getting in and out? A: High enough to be awkward, low enough to be awkward. You lift yourself in. Next generation might be taller and have boarding step/ladder or go over the top. Entry and exits is a problem but the issue has been dealt with on the Dyke Delta. Q: How big is the propeller and is there a gear reduction? A: 62” 2 blade I designed built by Sensenich on a Rotax Box. There was also a 60” 2 blade. Q: Do you have plans for a Radio Control model aircraft? A: There is an accurate 3 view on the web site: http://members.aol.com/slicklynne/facet.htm The Model Builder magazine has a peanut Scale from a friend of mine. There is an unauthorized electric model. I got a call asking where do I put the C.G. trying to help a fellow modeler I gave him the information. Then I was told that they where going into kit production. He did not even give me a kit. So the easy way to build a model is to buy one from the rat bast$%^& who ripped me off. If you like to see the aircraft it is located in the EAA Chapter 96 hanger. Mr. Wainfan stated he is usually (but not always) in the hanger on Sundays working on restoration from 10:30 to 3:30. Come on out, see the aircraft. The following article was appropriated from EAA Chapter 96, January 2005, Volume 1 Peninsula Flyer Newsletter Q: How did you determine location of the C.G.? A: Combination of analysis and flying radio control models. Classical delta wing math works just fine. Did a lot of conformation flying with models aircraft and moveable ballast to find the ugly areas. We where also able to get wind tunnel data before we flew the FacetMobile. Q: What are those ugly things you found when you started to moving the ballast back and forth on the model? A: The classic things you get with C.G. to far back it gets touchy in pitch. As the C.G. moves forward you run out of elevator power. But the design proved very C.G. tolerant. Q: Was the airfoil shape based on anything or pure experimental? A: No, not pure experimental. A whole lot of ideas came from American Aircraft Modeler, model aircraft called THE THING built by a man named (Bill Potter ?). This model was flat top and one day I flipped it over and it flew just fine. By building models looking at lifting body literature and British deltas. A lot of work was done to arrive at the shape. Many models died for the glory of science. Barnaby Wainfan The Man, The Myth, The Legend Excerpts from the Internet and publication: - Mike Hoedel Popular Science Great engineers can intuit how a design will come together, but their intuition is guided by a 'gut-level' understanding of how the laws of physics work. And then those engineers will go back and do the calculations to verify that their intuition was right. If the numbers don't work, then they start over again and solve the problems that were bedeviling their design. But no matter how much intuition they bring to the process, their final answer must be one that does not violate the laws of physics. And this brings us to Barnaby Wainfan. Simply put he is one of the brightest engineers I have ever met. And he understands - and can explain - the dynamic relationship between creativity and engineering better than just about anyone I know. Barnaby is the lead aerodynamicist at a major aerospace company. He designs and builds his own airplanes. He consults with various companies on aerodynamics. He has even appeared on an episode of Junkyard Wars where he led a team of people in the construction of a glider in just 10 hours. 4 Barnaby is not just a brilliant engineer; he is also a talented songwriter. Working with his friend Steve Desmond - Barnaby did the words, Steve the music and performance - they have put out a CD of their songs that captures a bit a Barnaby's outlook on the world. Barnaby Wainfan has seen the future of general aviation, and it looks like a stealth fighter. His design for an inexpensive home-built two-seat general aviation airplane, the Facetmobile, is a delta shaped blended-wing aircraft composed entirely of sharply angled flat planes— just like the Lockheed-Martin F-117, which was unveiled to the public six months after Wainfan began building his design. That’s a coincidence, says Wainfan, an aerodynamicist at Northrop Grumman. The F-117 is built with flat facets to reduce its radar signature; the Facetmobile, to cut costs. The parts are flat so that a home builder could make them on a table. “Airplanes are too expensive,” Wainfan says. “A new airplane should cost the same as a car, not a house. People tend to think about performance, performance, performance— higher, faster, farther. For me, it’s about simpler, safer, less expensive, more fun. The Facetmobile is for people who fly because it’s good for their soul.” says the penalty in drag is minor— and worth it, given the ease of construction. Wainfan, 49, a small, intense man with an unruly mop of gray hair and a bushy goatee, first flew the Facetmobile in 1993. That year, he flew it from his home airport in Chino, California, to Oshkosh, Wisconsin, and back, a distance of about 2,350 miles. The following year he was taking off from Blythe, California, when the engine quit at 500 feet. Wainfan walked away from the crash unscathed, but the plane was a wreck. Forecast: Calm - Today the Facetmobile, or what remains of it, resides under a dusty black tarp in the EAA Chapter 96 hangar in Compton, California. After it gets new landing gear and a new covering of fabric, it will be ready to fly again— if Wainfan ever gets around to it. “I’m trying to support a family of five with a job in the aerospace industry,” he says. “There are compromises you have to make. Like John Lennon said, ‘Life is what happens while you’re busy making other plans.’” No one doubts that the Facetmobile can fly, or that it could be built inexpensively. “It’s a safe, viable concept,” says Jack Cox of Sportsman Pilot magazine. The real question is whether Wainfan will ever find the time or money necessary to turn it into a viable business proposition. “If you have the resources to help,” his Web site appeals, “please contact us.” Wainfan’s primary influence was the Dyke Delta, a homebuilt delta-wing aircraft that was introduced in 1962. For more information, visit Barnaby’s website at: www.members.aol.com/wainfan/ NASA LARC NAG-1-03054 NASA PAV Wainfan’s primary influence was the Dyke Delta, a homebuilt delta-wing aircraft that was introduced in 1962. Futuristic-looking for its day, with a vertical tail but no horizontal stabilizer, the Delta could cruise at 170 mph and climb at 2,000 feet a minute. Wainfan’s Facetmobile achieved 110 mph with just a 46hp engine; a larger version with a bigger engine could easily match the Delta’s performance. The airplane’s flat-panel construction makes for rougher aerodynamics than the Delta’s (or those of virtually any other airplane out there, for that matter), but Wainfan (Personal Air Vehicle) Project Study http://members.aol.com/slicklynne/pavreport.pdf Radio Program with Barnaby Wainfan interview http://www.hour25online.com/Hour25_Previous_ Shows_2002-07.html#barnaby-wainfan_2002-0730 5 demonstrator made by conventional aviation construction methods. First flight was made on 30 November 1944. However, Republic Aviation's president Alfred Marchev realized that if Republic was going to win the expected post WW2 personal airplane market boom, they had to make something different at a price affordable for the masses. Marchev ordered a complete redesign of the Seabee to reduce the cost dramatically. The seemingly impossible goals Marchev set for his engineers were: a four seat amphibian aircraft at a sales price of $3500 - the conventional prototype would have an estimated sales price of $13000! The engineers took the challenge. Several changes were made; the tapered cantilever wings were replaced by constant chord strut braced wings, the partly buried retractable wheels of the RC-1 were replaced by wheel Design study of crashworthy general aviation aircraft via Karl Bergey. This is from the late 70’s or early 80,s Republic Seabee Dissected for NASA! Study the past to learn the future Barnaby Wainfan mentioned this in his speech so I looked it up. A few years ago NASA, together with some major universities and commercial enterprises started a project called SATS Small Aircraft Transportation System. The purpose of the project is to develop technologies to make personal aircraft affordable. In 2004 Munro & Associates, an engineering and manufacturing consultant company based in Troy, MI, purchased Seabee s/n 1054 for the purpose of studying the design and manufacturing methods used on the Seabee. The Seabee was delivered by truck to M&A on 15 March 2004 and soon work was started to dissect the Seabee for a detail benchmark study of the Seabee design. As a part of the SATS project, M&A made a Lean Design study of the Seabee for NASA. retracted in the free air. Numbers of parts were reduced substantially by introducing deep die press forming methods from the automotive industry, and wherever possible automotive parts and components were used in favor of overpriced aviation industry parts. In order to reduce the costs of the engine installed, Republic even acquired the engine manufacturer. Republic also negotiated large quantity rebates from the vendors. Unfortunately, several factors made big problem for the Seabee production and sales. When the Republic Seabee amphibian was put into production in 1946, this was the result of a design and development process never seen before in the aviation history. For the first time an aircraft manufacturer seriously looked to the automobile industry to take advantage of automotive design and manufacturing methods for reducing production time and costs. The first Seabee prototype, the RC-1 Thunderbolt Amphibian NX41816, was a concept 6 Important manufacturing tools such as sheet metal presses got delayed from the tool subcontractors, material and labor costs increased forcing Republic to increase sales price twice in less than a year. Production deliveries got delayed and production rates were never even close to the original goal of making 400 Seabees per month - 5.000 in one year. In June 1947 Republic was forced to stop production when sales failed, after only one and a half year and 1060 built. On 2 October 1947 Republic announced that the Board had made the final decision to terminate the Seabee project in favor of military aircraft such as the new F-84 Thunderjet fighter jet. Then - more than a half a century later - NASA starts looking into the future of personal aircraft transportation. It is realized that in the future it might be necessary to transfer more of the personal transportation from the roads to the air, to avoid further congestions. Select technologies can be common between automobiles and general aviation aircraft. The innovations and technologies being developed by MISATS are aimed at small aircraft private and business commercial smaller airports around the country. MISATS is the only SATS program working to improve the viability of the general aviation business model through aircraft design, manufacturing, training and infrastructure. Ultimately, MISATS plans are launching a compelling three year air vehicle design and fabrication program. The goal is to build a flying demonstrator that with the transition into a business venture that can provide these vehicles to the nation MISATS – The Michigan Small Aircraft Transportation System is a non-profit, government-industry-university consortium formed to transfer select commercial and automotive technologies to general aviation applications. Once developed, these technologies will be integrated into the SATS national research program. Innovations developed by MISATS will be eligible for commercialization by private companies with competitive business models. These companies will then be positioned for leadership in a revitalized and a commercially viable general aviation industry. MISATS is a contributor to the long-term NASA SATS vision of a National personal air transportation system that is safer and more efficient than the current commercial air travel system. SATS is a long range national vision with objective spanning out 25 years. The NASA goal is to reduce inter-city travel times by half in 10 years and by two-thirds in 25 years. NASA's strategy for general aviation revitalizations of aviation industry is challenging. The plans calls for the delivery of up to 20000 aircraft in 20 years, with some very demanding parameters. Aircraft price and cost of operation must be slashed dramatically, but improve performance and safety and vastly simplifying their operation. Munro & Associates started MISATS with the NASA approved goal to demonstrate that automotive style systems integration, Six Sigma quality, Lean Design and lean manufacturing can radically reduce aircraft complexity, while revolutionizing safety, efficiency and affordability. MISATS operates under the long term objectives that; aircraft can be designed and manufactured at unit cost comparable to automobiles. AIRFOIL SELECTION ISBN 9-9921-4657-5 Airfoil selection is an outstanding new book by airfoil expert Barnaby Wainfan which will aid the reader in understanding and choosing airfoils for light aircraft. This book is a collection of a series of articles originally published in Kitplanes magazine and reprinted in book form with the cooperation of Kitplanes editor, Dave Martin. All articles by Barnaby Wainfan. 57 pages, illustrated Future Thought We would like to hear from anyone who has an idea for a future presentation: Example would be a PLANS DAY: Some of use would bring in plans which we have studied. Then we could explain or just let others view and look at them. There is always something to be learned when you see what other designers have done to solve a problem or design idea. 7 Or a Build and Break it project: Something small a wood rib, small spar, etc. Design it as a group, determine what it will hold and break it to find out if we were right. Bring your idea for a design day: Even if it is only on a napkin, a few words would always be welcomes about you idea. Please bring any ideas, every idea is welcomed or send it and it can be published in the newsletter. FlaBob High John spoke about Wathan Aviation High School at the meeting. If you know of anyone who might be interested in going to this High School please contact them. There is a flyer with phone numbers and details attached to this newsletter. Print it and pass it around. There were some outstanding displaces on aviation related subject in the hanger. The students did a great job detail specific aviation subject matters. I enjoyed looking them over. I wish I had brought a camera so there would have been pictures for the newsletter. Next Time. Build your own FACETMOBILE Card Modeling or Paper Modeling is the art of creating scale models with paper. Models are built up from appropriately colored, cut, and folded pieces of paper, usually a stiff cardstock. Many models are available as kits, with preprinted pieces to be cut out and assembled by the modeler. It's also possible to build entirely from scratch. Paper models can be surprisingly sturdy, and can stand up to handling well. They derive their strength from their structure; even seemingly flimsy paper can be strong when it's shaped properly. This model builds into a 1:48 scale replica of the Facetmobile, and may be built as a static display model or (without propeller and landing gear) as a glider. You will need a printer capable of handling card or cover stock to print the parts sheets. I built this paper model and it does fly. I transferred ownership and further test flying to Robert Jordan, have him fly it for you. What this is and what it is not! It is important to remember that this newsletter is merely a conduit for information passed among members sharing their experiences. Its established purpose is fellowship and encouragement. It is NOT the intent to give authoritative advice on aircraft construction or design. The Editor and the contributing writers disclaim any liability for accuracy or suitability of information that is shared. You can assume that all or some of the information in each issue is not correct for aircraft design. This is simply a collection of notes which where taken at the Design Group meeting and placed with other items into a newsletter format. Lots of items will come from the meeting as best as one can interpret what is stated. Many items will come from other sources such as books and internet files (Grabbing from any source to make it useful and a lot will come from the internet to expand what was talked about at the meeting, like the V-173 and Aspect Ratio material in this issue. (I will take it where I can get it). Speak out if you were wrongly quoted or something misinterpreted, no harm was implied, only lack of knowledge in understanding and interpreting what was said. This will only be sent by email to anyone whom would like to receive it. If others would like to contribute articles, stories and materials in the future feel free. The newsletter should provide a way for us to communicate with each other. It is a place for those of us who want to network, connect and share information to do so. Anyone can write anything to whomever about any aircraft or aviation design ideas. With any luck we will learn something from everyone and hopefully someone can learn one thing from us. This newsletter is also located at this Web Site for download or viewing. This Web Site is hosted by EAA Chapter One and I would like to thank them for this services. http://www.eaach1.org/design.html I have included this model with the newsletter, build it its fun. Also go to this site, there are many types of these paper aircraft being offered. http://www.currell.net/models/mod_free.htm Next Issue Part 2 Low Aspect Ratio Paraplane and Ed Marquart 8 ASPECT RATIO In aerodynamics, the aspect ratio is an airplane's wing's span divided by its standard mean chord (SMC). It can be calculated more easily, however as span squared divided by wing area: they must be as efficient as possible in every respect in order to stay aloft. To better understand low aspect ratio you need the theory about the Cl / Cd curve and its meaning, the relation between glide ratio and the needed power to keep flying. Also; Reynolds numbers and surely about induced drag. Why don't all aircraft have high aspect-ratio wings? There are several reasons: Aspect ratio or (or AR in many other books) can be defined also as: = b2 / S = S / k2main = b / kmain With: = aspect ratio S = wing area b = span kmain = main chord Informally, a "high" aspect ratio indicates long, narrow wings, whereas a "low" aspect ratio indicates short, stubby wings. So, low aspect ratio's are airplane with a small span in relation to their wing area. Aspect ratio is a powerful indicator of the general performance of a wing. Wingtip vortices greatly deteriorate the performance of a wing, and by reducing the amount of wing tip area, making it skinny or pointed for instance, you reduce the amount of energy lost to this process, induced Structural: the deflection along a high aspectratio wing tends to be much higher than for one of low aspect ratio, thus the stresses and consequent risk of fatigue failures are higher particularly with swept-wing designs. Maneuverability: a high aspect-ratio wing will have a lower roll rate than one of low aspect ratio, due to higher drag and greater moment of inertia, thus rendering them unsuitable for fighter aircraft. Stability - low aspect ratio wings tend to be more naturally stable than high-aspect ratios. This confers handling advantages, especially at slow speeds. Practicality - low aspect ratios have a greater useful internal volume, which can be used to house the fuel tanks, retractable landing gear and other systems. Looking at a low aspect ratio will help you believing that it is less trouble to fit the cockpit, engines, fuel and cargo into the wing. The result is a clean wing without humps or any extra external volumes as fuselages, engine pods and stuff. A clean wing leads to less overall parasite drag. This could lead to a better glide ratio if there wasn't something as induced drag. But there is. Just look at the size of the wingtips. Can you imagine the air leak over this wingtip? I bet you can. So, to get a Cl / Cd curve of the total airplane you don't need to add the drag of things like fuselage, engine pods or so, but you sure need to add the induced drag. And it is not small ! The L/D ratio is very important. Not only does it determine the glide performance of the aircraft, but as we will soon see, it determines range, endurance and climb performance as well. It therefore behooves us to consider what factors determine the value of the L/D ratio. Since the L/D ratio is simply lift divided by drag we will start by doing the algebra: L = CL x S x ½rV2 D = CD x S x ½rV2 Notice that S, r and V cancel out. These elements affect both Lift and Drag equally and therefore cancel out in the ratio. drag. This is why high performance gliders have very long, skinny wings; with no engine power, Thus, the L/D ratio is simply equal to: L = CL D CD You can see that the higher aspect ratio aircraft clearly has a much higher L/D max. Therefore, the high aspect ratio aircraft will glide much further. CL changes only with angle of attack. But what about CD? You can also see that the optimum CL is much lower for the low aspect ratio aircraft. CD is the sum of Cdi and CDP. We also learned that Cdi changes with angle of attack. But, CDp changes only when the shape of the aircraft changes (for example when gear or flaps are extended.) This means that aircraft with short wings must fly at a small angle of attack in order to be efficient. Conversely, an aircraft with longer wings will be more efficient at a somewhat higher angle of attack. The higher the aspect ratio the greater the angle of attack the aircraft must fly at in order to be efficient. Mathematically we can express L/D as follows: L = CL = CL D CD (CDp+ CL 2 / peAR ) From the above we can see that L/D changes with angle of attack (i.e. CL) changes in configuration (i.e. CDp) and changes in design (i.e. AR. and e.) If you have a calculator capable of plotting an x-y coordinate graph program the L/D equation above into your calculator. Choose representative values for e and CDp: e.g. e =.8 CDP = 0.025 It is important to remember that small angles of attack correspond to high indicated airspeeds (relatively speaking) Large angles of attack correspond to relatively slower speeds. Thus, we can summarize by predicting that a glider, with its long wingspan will have a high L/D max, and as such will be able to glide a long way. However, it will inherently need to fly at a large angle of attack and therefore, be quite slow. A low aspect ratio jet fighter will not be able to glide very far. However, it will be at its most efficient when skimming through the air at a relative low angle of attack and high speed. Most birds have wings with a high aspect ratio, and with tapered or elliptical tips. This is particularly noticeable on soaring birds such as the albatross and eagle. Doves and woodpeckers have a low aspect ratio. To get away from predators quickly these birds make sharp turns. The shape of their wings allows them to do so. On the other hand, falcons and frigate birds have high aspect ratios, giving them the ability to sustain high-speed flight for long periods. However, these birds do not have wings that can be flapped as rapidly as their woodpecker cousins who have better maneuverability. Then choose a value for AR. If you choose a low value for AR (e.g. 3 or 4) you will get a graph similar to the one shown to the above. If you choose a higher value for AR (e.g. 9 or 10) you will get a graph similar to the second one above. In addition, the V-formation (echelon) often seen in flights of geese, ducks and other migratory birds can be considered to act as a single swept wing with a very high aspect ratio - the vortices shed by the lead bird are smoothly transferred to the next and so on. This confers a huge efficiency advantage to the flight as a whole perhaps as much as a 100% improvement compared to a single bird in flight. Note that the usual common explanation of the V-formation that following birds are "shielded" from air resistance by the bird in front - may be misleading. While birds do "take turns" at being the lead bird, it is probably to give those at the tips a rest - they are the ones that will experience the most drag when the vortices are finally shed. However, the full explanation of this behaviour is still the subject of research and debate; scientists still do not claim to have fully understood the phenomenon. The wetted aspect ratio The wetted aspect ratio is a good indication of the aerodynamic efficiency of an aircraft. It is a better measure than the aspect ratio. It is defined as: where Sw is the wetted surface of the whole aircraft in contrast to the wing area used for the definition of the aspect ratio. A good example of this is the Boeing B-47 and Avro Vulcan. Both aircraft have very similar performance although they are radically different. The B-47 has a high aspect ratio wing, while the section (the critical section) reaches its 2-D maximum Cl. When the sweep is very large, or aspect ratio low, this approach does not work. Separation tends to occur near the leading edge of the wing, but unlike in the low sweep situation, the separated region is not large and does not reduce the lift. Instead, the flow rolls up into a vortex that lies just above the wing surface. Rather than reducing the lift of the wing, the leading edge vortices, increase the wing lift in a nonlinear manner. The vortex can be viewed as reducing the upper surface pressures by inducing higher velocities on the upper surface. The net result can be large as seen on the plot here. Avro Vulcan is a low aspect ratio blended wing body. They have, however, a very similar wetted aspect ratio. The Vulcan is a Thick Delta which has a L/D of 17 about the same as the B47 but a aspect ratio of 3. Low Aspect Ratio Wings at High Angles of Attack At high angles of attack, several phenomena usually distinct from the cruise flow appear. Usually part of the wing begins to stall (separation occurs and the lift over that section is reduced). An approximate way to predict when this will occur on well-designed high aspect ratio wings is to look at the Cl distribution over the wing and determine the wing CL at which some The effect can be predicted quantitatively by computing the motion of the separated vortices using a nonlinear panel code or an Euler or Navier-Stokes solver. This figure shows computations from an unsteady non-linear panel method. Wakes are shed from leading and trailing edges and allowed to roll-up with the local flow field. Results are quite good for thin wings until the vortices become unstable and "burst" - a phenomenon that is not well predicted by these methods. Even these simple methods are computation-intensive. where Λ is the leading edge sweep angle. If this acts as an additional normal force then: Cn' = Cn + (Cn sin α - CL2/π AR) / cos Λ and in attached flow: CL = CLa sin α with Cn = CL cos α Thus, Cn' = CL cos α + (CL cos α sin α - CL2/π AR) / cos Λ = CLa sin α cos α + (CLa sin α cos α sin α - (CLa sin α)2/π AR) / cos Λ = CLa sin α cos α + CLa/ cos Λ sin2 α cos α - CLa2/(π AR cos Λ) sin2 α CL' = CLa [sin α cos2 α + sin2 α cos2 α /cos Λ - CLa/(π AR cos Λ) cos α sin2 α] = CLa sin α cos α (cos α + sin α cos α/ cos Λ - CLa sin α /(π AR cos Λ)) If we take the low aspect ratio result: CLa = π AR/2, then: Polhamus Suction Analogy A simple method of estimating the so-called "vortex lift" was given by Polhamus in 1971. The Polhamus suction analogy states that the extra normal force that is produced by a highly swept wing at high angles of attack is equal to the loss of leading edge suction associated with the separated flow. The figure below shows how, according to this idea, the leading edge suction force present in attached flow (upper figure) is transformed to a lifting force when the flow separates and forms a leading edge vortex (lower figure). CL '= π AR/2 sin α cos α (cos α + sin α cos α/ cos Λ - sin α /(2 cos Λ) ) Cross-Flow Drag Analogy An even simpler method of computing the nonlinear lift is to use the cross-flow drag analogy. The idea is to add the drag force that would be associated with the normal component of the freestream velocity and resolve it in the lift direction. The increment in lift is then simply: Δ CL = CDx sin2α cosα. The plot below shows each of these computations compared with experiment for a 80° delta wing (AR = 0.705). In these calculations a cross-flow drag coefficient of 2.0 was used. The suction force includes a component of force in the drag direction. This component is the difference between the nosuction drag: CDi = Cn sin α, and the full-suction drag: CL2 / π AR where a is the angle of attack. The total suction force coefficient, Cs, is then: Cs = (Cn sin α - CL2/π AR) / cos Λ Another case with much higher aspect ratio is shown below. Note that the very simple model seems to do nearly as well as the more involved suction analogy. Flaps are often not used on SST designs due to difficulties with longitudinal trim. Designs with tail surfaces or canards can employ some flaps, increasing the effective alpha limit by 2-3 degrees. Clearly, conventional slats do not help these designs as they produce little change in CL at a given angle of attack. However, studies have shown that some types of leading edge vortex flaps, intended to strengthen the leading edge vortices can be used to further increase the maximum usable CL. Span Loading Low aspect ratio seems to go against the principle of using a high aspect ratio design to keeping induced drag down. Not really, when you look at the numbers; CDi = CL2 / πAR The maximum lift of a low aspect ratio wing is significantly increased by the presence of these vortices and is limited either by vortex bursting or by allowable angle of attack. Vortex bursting is a phenomenon in which the structured character of the vortex is destroyed resulting in a loss of most of the vortex lift. It occurs due to adverse pressure gradients acting on the vortex. When the vortex burst occurs on the wing (as opposed to downstream of the wing) the lift drops substantially. Although there are some empirical methods for predicting vortex burst, the phenomenon is quite complex and difficult to predict accurately. For many SST designs, however, the maximum CL may be predicted by assuming that the vortex does not burst at the maximum permissible angle of attack. Because of the length of the fuselage, this angle may be restricted to a value of 10-13 degrees. Using this value in the above expression for CL leads to a reasonable estimate for maximum lift on such designs. A flow pattern, similar to that of the highly swept delta wing, is found at the tips of low aspect ratio wings and over fuselages. The vortex formation significantly increases the lift in these cases as well. Especially in the case of fuselage vortices, the airplane stability is affected. Interaction with downstream surfaces is often important, but hard to predict. Computations of lift at a specified angle using the cross-flow drag analogy can easily include the component associated with fuselage lift as well. If we do a little substituting with CL and AR we get; L2 / q2S2 S / π b2 Multiply the coefficient by qS , so you get actual drag you have; Di = ( L / b ) 2 . ( 1 / π q ) Look at this part it is squared, this has a lot of effect on your design. Anytime something is squared it can help you or cause you major concerns. When a number is squared growth climbs fast. Lift is needed to over come weight and weight has a terrible effect on induced drag. Induced drag rises with weight and it also goes down with weight reduction. (This kind of works like that great tasting chicken at the EAA Chapter 1 provides at their meetings. A few grams of chicken in our airframe become pounds of payload on our bodies.) LAR aircraft have the ability to make light structures keeping this formula in check. What this is telling us is that SPAN LOADING HAS A MAJOR EFFECT ON INDUCED DRAG! Arup S-4 (foreground) demonstrates the practicality of a low aspect ratio wing. Both Arup S-2 (background) and the S-4 were frequently used as flying billboards during their accident-free careers. Snyder's first aircraft was known as the Dirigiplane, Monowing, and finally Arup S-1, at various stages of its development. Rudders are at the after edges of-the vertical stabilizers; elevator extends across the wing trailing edge; ailerons are at the top of the vertical stabilizer, forward. A podiatrist from South Bend, Indiana, was responsible for one of the more distinctive and successful tailless designs of the Depression. Dr. C.L. Snyder, intrigued with the flying qualities of a felt heel lift that he had idly tossed through the air one day in 1926, pursued his idea from the primitive model stage to unpowered and powered gliders, and finally to several highly successful disc-type aircraft. Like Junkers, Soldenhoff, and Rumpler, Snyder's goal was to develop of the flying wing for air transport purposes. He envisioned an aircraft with a wing 15 feet thick with a 100foot span and a 100-foot chord. The passengers were to be seated in the wing with a clear view forward through the plastic leading edge of the wing. Snyder's early glider experiments led to the formation of the Arup Manufacturing Corporation in 1932 to refine his initial experimental configuration to a practical aircraft. Aided by the engineering skills of Raoul Hoffman and with Glenn Doolittle (racing pilot Jimmie Doolittle's cousin) acting as test pilot, Dr. Snyder produced three more variations of the basic disc-shaped Arup S-1 powered glider. Of the three, Arup S-2 and S-4 proved to be more durable and practical, making hundreds of flights during the mid-1930s, including impressive demonstration flights for the NACA, CAA, and the Army. The Arup experienced an accident-free service life. Some of its pronounced advantages over more conventional aircraft were greater lift and safety, increased cruising range, lower takeoff and landing speeds, and stall-proof flight characteristics. Dr. Snyder's Arups were not commercial successes, however. He had inadequate working capital, inexperienced management, and an aircraft that just did not "look right." Raoul Hoffman, Dr. C.L. Snyder's engineer at Arup, left that company in 1933 and moved to Florida where he designed an Arup-type aircraft for a Chicago industrialist. The Hoffman flying wing, like the Arups, had performance figures that were guaranteed to appeal to those citizens who wanted to replace the family automobile with an "air flivver." Unfortunately, Hoffman's aircraft caught fire in flight from a broken fuel line and crashed, killing the pilot. The airfoil was stated to be a Munk-designed, reflexed NACA M-6 of about 12% thickness. Built in St. Petersburg, Florida, this unusual tailless aircraft resembled the Arup disc designs. A 1934 design by former Arup engineer Raoul Hoffman, the wing was a semicircle to which floating tip controllers were added to serve as ailerons. Elevators were located in the wing's trailing edge. S-2 aka Snyder A-2 1933 = 1pC flying wing; 36hp Continental A-40; span: 19'0" length: 17'2" v: 97/x/23; ff: 5/28/33 (p: Glenn Doolittle). Raoul Hoffman, C L Snyder. Developed from Snyder's flying-wing glider, Arup 1 Dirigiplane, which was ultimately fitted with a Heath-Henderson motor. Wing-tip "ear" ailerons, STOL flight characteristics. POP: 1 [X/R12894]. S-3 1934 = 2pC flying wing; 70hp LeBlond 5DE; span: 22'0" length: 17'6" load: 490 v: 97/90/20; ff: 7/15/34. Larger version of S-2 with ailerons moved flush with the wing-tips, tricycle gear. POP: 1 [14147], destroyed by an unsolved arson fire after its test flight. S-4 1935 = Remake of S-3, with 70hp LeBlond; span: 22'0" length: 18'6" load (included two parachutes, just in case): 550 v: 110/x/28 ceiling: 9,000'; aspect ratio 1:1.78; ff: 3/19/35. Small elevators added atop fin. Some reports tell of a return to conventional gear, but photos in Aug 1935 Popular Aviation show a nose gear. POP: 1 [14529]. Disposition unknown. US patent #2,062,148 assigned to Cloyd Snyder in 1937 for a variable wingform aircraft. A smaller 1p replica was built and flown c.1985 in Bristol IN. SNYDER, C.L. (later w/HOFFMAN, R.): U.S. Pat. No. 1,855,695: “Aircraft”, 4/26/32 (filed 9/8/30; a controllable “compartment” lifting body with straight l.e. joined to curved t.e., and length approximately equal to span; pref. embodiment describes pilots, passengers, engines, etc. inside airfoiled, possibly buoyant body): The Arup S-1 was nicknamed "The Dirigiplane" as it was designed to hold buoyant gas. It did use a classic Clark-Y airfoil. Another nickname was "Monowing". The Arup S-2 did fly in 1933. It had an enclosed cockpit, a engine in front and a single vertical tail. There are two pictures of the Arup S-2 and both show a different placement of the ailerons. The first picture (seen on nurflugel-website) shows ailerons added to the wingtips as extra surface in the shape of a half moon. The ailerons were fully rotating, which means that this extra surface did completely turn around a axis and was not made in two separate parts (one fixed, the other rotating). The other picture shows ailerons placed next to the elevator at the rear of the airplane. The picture of the Arup S-4 on the Nurflugel-site shows the Arup S-2 in the background with the last mentioned ailerons. Clearly it was planned for mass production. But it was a bad economical time, the "Great Depression", and no buyers were found. Pity... because it flew well. The S-2 flew hundreds of hours and Dr. Snyder took his young son and daughter with him on several trips. That is something you don't do if you are not sure about safe flying. The Arup S-3 and S-4 did probably have the same airfoil as the S-2. They were further refinements of the S-2. Both did have a classic tail. The S-4 had ailerons placed in the trailing edge of the wingtips. South Bend Regional to unveil historic display 05/15/2003 Dr. Snyder’s low-A/R “Dirigiplane” glider flew and was then motorized in 1932 as the S-1. Highly successful powered versions, like the 1933 ARUP S-2 (above), grew protruding fuselages with airfoil contours to the extent thought necessary on such a small plane. While the aircraft and proposals appearing below featured patented ideas that could serve as bases for all-wing or BWB aircraft, the following aircraft incorporate pertinent features which appear not to have received patent recognition. Related patents are mentioned. These all reflect a shared adventurous spirit among a variety of Burnelli’s contemporaries working independently, but embody relevant ideas appearing before and up to the filing or publication dates of Burnelli’s tailless aircraft patent. A full-size replica of a "flying wing" aircraft designed in the 1930s by a South Bend podiatrist turned aeronautical engineer goes on display Friday at the South Bend Regional_Airport. The two-seat replica of Cloyd Snyder's "Arup Flying Wing" was assembled by retired engineer Bernard Rice. Snyder dreamed up his revolutionary aircraft design in the spring of 1926 after he threw a felt boot heel across a room and noticed that it flew quite well. Four versions of the plane were developed during the 1930s, but the Great Depression forced Snyder to abandon plans for a commercial 100passenger model. All four Arup models were eventually destroyed by vandals. Rice reconstructed his model from photographs. It's 19 feet long with a 22-foot wingspan. Vought-Sikorsky V-173 "Flying Pancake" Type: experimental prototype (Fighter) Crew: 1, Pilot Armament: none Specifications: Length: 26' 8" Height: 12' 11" Width: 23' 4" Gross Weight: 2,258 lbs Propulsion: No. of Engines: 2 Powerplant: Continental A-80 Horsepower 80 hp each Prop diameter: 16' 6" Performance: Range: limited (20 gal. of fuel) Max Speed: 138 mph sea level Climb: to 5000 ft in 7 min Ten years after the first Arups appeared in the 1930s, another disc-shaped oddity could be seen flying around the Connecticut countryside. The Vought V-173 "Flying Pancake" was the brainchild of Charles H. Zimmerman, who built his flying wing while employed as an engineer with the National Advisory Committee for Aeronautics (NACA). NACA's light-plane research study of 1933, which provided the incentive for other tailless designs in the 1930s, also inspired Zimmerman to design a passengercarrying aircraft that would land and take off like a helicopter and once airborne, convert to conventional flight. Perhaps influenced by the Arup design, Zimmerman built test models that received NACA endorsement. Few aircraft flown during World War Two can surpass the Vought V-173's startling frisbee-like appearance or its remarkable capabilities. The unprecedented speed range of this low-aspect wing type of aircraft potentially ranged from under 48 kph (30 mph) to more than 805 kph (500 mph). The experimental V-173 performed well enough during testing to warrant the development of a full-scale military version. Unfortunately, enthusiasm for new turbojet powered aircraft reduced interest in slower-speed tactical aircraft such as the XF5U, the V-173's successor and the type became an aeronautical dead-end. Scientific experimentation with low-aspect ratio flying wings (short wingspan and long chord) began in the late 1920s, under the guidance of Dr. Cloyd Snyder, an Indiana podiatrist with a fascination for aviation. He became intrigued when he tossed a felt heel inset and discovered that it glided remarkably well. Conventional wisdom, up to that time, dictated that an airplane wing was most efficient if the ratio of the wingspan to its chord was 6:1. Nonetheless, in the early 1930s, Snyder enthusiastically devoted his savings and time to experiments that demonstrated the practicality of low-aspect ratio wings, especially in low-speed flight. Snyder's greatest contribution over earlier tests of lowaspect ratio wings was the substantial rounding out of the normally square trailing-edge corners of the wings, which significantly improved the liftto-drag ratio of the airfoil. His first effort was a horseshoe-shaped glider, later converted to a powered model. Three other Snyder Arup models verified the benefits of the low-aspect ratio design, which held the promise of takeoffs and landings at speeds under 48 kph (30 mph) and cruise speeds of more than 209 mph (130 mph). Before his company went out of business, Snyder inspired several other pioneers. One of these, Charles Zimmerman, an engineer for the National Advisory Committee for Aeronautics (NACA forerunner of NASA), became intrigued with the short-takeoff and landing potential of the horseshoe-shaped wing after witnessing a 1933 ARUP demonstration in Washington. He quickly set about conducting his own experiments. Zimmerman's access to NACA wind tunnels allowed him to explore the most efficient variations of Snyder's wing designs. By 1935, Zimmerman had settled on an improved twin-engine version of the Snyder wing and completed a single-person prototype powered by two 25horsepower motors. The model never flew because of engine difficulties, but a number of large rubber bandpowered models arrangement was awkward and uncomfortable. Vought engineers then constructed a conventional cockpit with the pilot in a seated position, although the lowered instrument panel and leading edge windscreen remained in place (though this proved to have little value). To allow sufficient ground clearance for the enormous three-bladed propellers, the fuselage inclined upwards at a twenty-two degree angle when sitting on its fixed landing gear. The pilot entered the cockpit through a trapdoor in the floor, which he reached by ladder. Zimmerman intended the V-173 to "hang on its props" by hovering in a vertical attitude. This, combined with the requirement of the low-aspect ratio wing for a large induced airflow, necessitated enormous (16 ft 6 in) diameter propeller blades. However, he was never able to convince Vought to expend sufficient convinced his funds to develop an The all-movable, or "flying" tail of the V-173 superiors to allow him adequate control "Zimmer-Skimmer" is quite evident in this view of to approach aircraft system for hovering or the disc shaped aircraft. During its successful manufacturers to ultra low-speed flight, flight test program, the "Flying Pancake" construct a full-size and the aircraft never experienced several crashes, but sustained little low-aspect flew in this flight damage because of its very low landing peed. Test demonstrator. With regime. On one pilots Were unable to spin the aircraft and were NACA’s concurrence, occasion, Zimmerman amazed at its rapid deceleration as it was pulled in 1937, Zimmerman bypassed Vought into a tight turn. approached United entirely and submitted Aircraft and Vought this proposal directly made a proposal to the US Navy on August 15, to the Bureau of Aeronautics, who rejected it 1939 for a full scale prototype. On May 4, 1940, a specifically because he had bypassed Vought. contract was in hand. Zimmerman was very personally involved with the project and plant personnel took to calling the unusual aircraft the "Zimmer Skimmer." Zimmerman found success with the Vought The V-173 made its first flight on November 23, Division of United Aircraft, which was on the 1942, with Guyton at the controls. Heavy control lookout for innovative approaches to fighter forces almost led to a forced landing during the aircraft design. By 1938, Zimmerman, now otherwise successful test, but the addition of working full-time for Vought, had constructed the large trim tabs between the rudders, referred to V-162, an electrically powered remote control as stabilizing flaps, helped to alleviate the model with a 0.91-meter (3-foot) wingspan that problem on subsequent flights. Other problems flew well enough to earn Navy research funds. included poor visibility over the large wing and By March 7, 1939, Vought had completed resonance vibrations from the large propellers designs for a full-size wood and fabric prototype, operating at high angles of attack, which the V-173, and submitted them to the Navy. On necessitated the addition of dampers. As the May 4, 1940, the Navy issued Vought a induced airflow of the propwash generated much construction contract for the aircraft. The twinof the lift on the low aspect ratio wing, an engine engine design relied on a 7.01-meter (23-foot) failure could result in an immediate loss of diameter horseshoe shaped wing, equipped with control, which added to the stress of flight-testing. twin vertical stabilizers. On the V-162, the entire Additionally, power-off gliding characteristics rear section of the fuselage hinged like an were substantially different without the induced elevator, but on the V-173, two small "ailevators" airflow of the propellers. (aileron/stabilator) extended outward from curved One problem inherent in low-aspect ratio wings tail of the horseshoe wing. Twin vertical was a significant amount of induced drag. stabilizers and rudders stood up from the wing, However, Zimmerman came up with a novel aft and inboard of the stabilators. Zimmerman solution. The V-173's large propellers counterimbedded the cockpit in the leading edge of the rotated away from the fuselage so that the airflow wing with the intention that the pilot would fly the from the prop wash would help to mitigate the aircraft while lying prone to reduce drag and large wing-tip vortices produced by the lowmaximize the effect of the induced airflow from aspect ratio wing. The landing flare also proved the propeller thrust. However, the program test pilot, Boone Guyton, quickly found that the problematic as the large ground effect "cushion" of the wing prevented the tail from quickly settling to the ground upon landing, thus greatly extending the landing roll. Heavy braking was not an option because it could cause the top-heavy aircraft to nose-over. The solution was the addition of a spoiler on the aft edge of the low aspect ratio wing, which the pilot could deploy after touchdown to bring the tail-wheel rapidly into contact with the runway. In spite of teething troubles with the innovative aircraft, Guyton and other pilots found the V-173 to be a remarkable aircraft. In addition to its short-field capabilities, the broad speed eed range of the aircraft proved to be an important asset in emergencies. One example occurred on June 3, 1943 when pilot Richard Burrough's experienced an engine failure and made a forced landing on a beach that resulted in the aircraft flipping over. However, the V-173 touched down at a mere 24 kph (15 mph) and did not suffer significant damage. Burroughs was uninjured. Charles Lindbergh developed a keen interest in Zimmerman's project, which he observed during his visits to the Vought-Sikorsky plant while he served as a consultant. However, he initially declined Zimmerman's invitations to fly the aircraft. Lindbergh correctly ascertained that if the tall, slender landing gear encountered soft ground, the aircraft would flip over onto its back with nothing but the fragile canopy to keep the V173's weight off the upended pilot. When he witnessed Richard Burrough's crash on the beach, which proved the canopy would safely protect the pilot, Lindbergh decided that he would take the airplane for three uneventful trial flights on November 15, 1943. Subsequently, the V-173 suffered through two other crashes, though neither was severe. On May 26, 1945, Burroughs made a forced landing on a golf course. In 1947, Boone Guyton crashed into high-tension wires on takeoff, though both he and the aircraft survived relatively intact considering the nature of the accident. While the unusual shape of the aircraft attracted considerable attention in the local community, the innovative nature of the technology kept it out of the media, and security was heavy around the aircraft. Germany also conducted its own lowaspect ratio research during the war, including the development of the Sack AS 6 (the "flying beer tray"), similar to the earlier Snyder designs. The V-173 proved to be under-powered, yet its low aspect ratio wing allowed it to take-off at a mere 46 kph (29 mph). In calm winds, this required a take-off run of only 61 meters (200 ft). Landings were possible in considerably less distance. It could successfully maintain controlled flight at a 45 degree angle-of-attack - three times that of aircraft with conventional wings. The aircraft bled speed rapidly when entering a tight turn - a characteristic that could prove highly advantageous in a dogfight. The V-173's unique flight characteristics substantiated Navy interest in a full-size fighter or attack aircraft as the wind-speed generated by an aircraft carrier or other naval vessel steaming into a breeze would allow for vertical takeoffs and landings. This increased the amount of deck space for other aircraft or allowed for the construction of smaller ships. In September 1941, even before the first flight of the V-173, the Navy was so intrigued in the concept that it contracted with Vought-Sikorsky to build two VS-315s, which were larger fighter versions of the V-173. Funding problems and technical difficulties delayed completion of the aircraft, designated the XF5U, until 1947, by which time the Navy had become more interested in high-speed jets than a propeller-driven fighter with short take-off and landing capability. The Navy had the XF5U scrapped before it could make its first official flight, though it had reached completion and had begun taxi tests. Guyton flew it briefly in ground effect so that he could say it had flown. The XF5U was a remarkable aircraft in concept, though its construction posed serious technical challenges. The large Pratt & Whitney R-2000-7 engines could not drive the propellers directly because of the curve of the wing that arced towards the rear of the aircraft. This necessitated an extended transmission system with a gearbox that turned ninety-degrees as well as ninetydegree drive shaft coupling in the engine, which together greatly increased the complexity of the aircraft. The likelihood of gearbox failure in the system was high and would have immediately caused the aircraft to go out of control. The large, four bladed propellers incorporated a novel flapping hinge system to allow them to cope with the asymmetric loading conditions at high-angles of attack. This system, although innovative, would have taken considerable time to perfect. Vought rolled out the V-173 during public displays for several years after it had finished its 132 flight hours of testing on March 31, 1947 - its 190th flight. In 1949, the company officially transferred the V-173 to the Smithsonian Institution. The internal structure of the aircraft rendered it unsuitable for disassembly and the aircraft had to travel by barge from Connecticut to Virginia. Overview The basic wing area (427 sq ft.) and planform (less ailevators and propeller nacelles) of the V173 and XF5U-1 were identical. The airfoil was the NACA 0015 section on the V-173 and the NACA 0018 section on the XF5U-1. Two Continental A-80 engines, rated at 80horsepower each, turned two 16.5-foot threebladed propellers on the V-173. The aircraft had long fixed main landing gear and a 22-degree nose-high static ground angle. Wheel fairings were added after the first flight. The pilot cockpit enclosure had a windowed leading edge ahead of the pilot for down vision, and four segmented leading edge inlets (left and right) for engine air. For light weight, the airframe structure was made of wood with fabric covering. With a wing loading of only 5 lbs/sq ft, the V-173 could lift off in 200 feet in a calm, and with a zero run against a 25knot headwind. However, with a power loading of 14-lbs/hp maximum, level flight speed was only 138 mph. The pilot could enter or egress from the cockpit through a hatch in the cockpit floor or through a sliding canopy. The first flight was of only 13 minutes duration because of very heavy longitudinal stick forces, and having only 20 gallons of fuel aboard. The stick forces were subsequently lightened by adding the trailing-edge stability flaps and ailevator trim tabs. The airplane accumulated 131 hours in several hundred flights, many of which were flown to exhibit the outstanding STOL characteristics. Vought’s Chief experimental pilot, Boone T. Guyton, made 54 flights. Guyton summed up his observations as: I was able to apply full power, raise the nose as high as it could be held, and have control about all three axes without stalling. The aircraft could not be completely stalled or even approach a spin condition. A notable characteristic was high deceleration in a tight turn due to the aspect ratio (drag due to lift), and low power loading. Engineand propeller- related vibration showed the need for articulated (i.e., flapping) propellers. Today, with its vertical tails and ailevators removed, the V-173 is in storage at the Smithsonian Institution’s Air Museum warehouse in Silver Hill, Maryland. Charles H. Zimmerman promoted his “Flying Pancake” design from 1933 to 1937 while working for the National Advisory Committee for Aeronautics (NACA) at Langley Field, Virginia. He filed for a design patent on April 30, 1935 and was granted patent #2,108,093 on February 14, 1938. With the concurrence of NACA, Zimmerman approached United Aircraft Corporation with his novel design in 1937 and joined United’s Chance Vought Aircraft Division in that year as project engineer. By August 15, 1939, drafting, engineering design, and aerodynamic studies were far enough along for Vought to submit a proposal to the U.S. Navy for a full-scale prototype of the V-173. The U.S. Navy placed a contract for one V-173 on May 4, 1940. First flight of the airplane was on November 23, 1942. Success!! To best appreciate the very-advanced V-173 design concept, one must go back to 1930 when Charles Zimmerman graduated from the University of Kansas with a degree in electrical engineering and an introductory course in aerodynamics that helped him secure a job with NACA. Initially, Zimmerman made a name for himself by designing a free-spinning wind tunnel and then a free-flight wind tunnel. What made airplanes fly was the stuff that young NACA engineers lived and breathed. This fascination led Zimmerman to design the V-173 as a flying wing, to minimize wetted area and parasite drag, and to put the propellers at the wing tips, rotating so as to oppose induced drag. It was known that a finite aspect ratio wing had a bound lifting vortex along the quarter chord line which, when viewed from the rear, rotates clockwise at the port (left) wing tip, and counterclockwise at the starboard (right) wing tip, causing downwash aft and rotates the lift vector back to cause induced drag such that: CDi = CL2/pe Aspect Ratio Where “e” is the airplane efficiency factor determined by wind tunnel test. Zimmerman knew that a right-hand propeller generates a strong right rotational component to the slipstream. Hence, a right-hand propeller on the starboard wing tip and a left-hand propeller on the port wing tip should reduce induced drag. The theory of wing lift and induced drag, together with experimental data available for propeller slipstream rotation lead to: CDi = CL2/pe (1-FOO) Aspect Ratio That’s right, it was called “FOO Factor” or FQ , and had theoretical values from 0 to 1 or more, depending on shaft horsepower. With power off, FOO=0 and induced drag was proportional to lift coefficient squared and inversely proportional to wing aspect ratio. In a high-powered climb, FOO could be greater than one and induced drag became induced thrust. This was true not only theoretically, but actually, as shown by powered tests of a 1/3-scale V-173 model in the Langley full-scale wind tunnel (December 1941). Numerous free-flight (rubber-band and electricpowered) and captive wind tunnel tests were conducted between 1933 and 1943. These tests showed that: Symmetrical trailing edge flaps provided insufficient roll and pitch control. Therefore, “ailevators” were added to the basic design. (Ailevator was coined from aileron plus elevator and the spelling was later changed to ailavator.) Propeller cross-shafting was required for safety of flight with one or both engines out. Twin fins and rudders were always part of the design for directional stability and control. Vought VS-315 (XF5U-1) Large diameter propellers at the wing tips, rotating up inboard Ailavator surfaces for roll and pitch control The XF5U-1 was designed as a land-based or carrier-based fighter to be used with or without a catapult, with an arresting gear. The airplane incorporated certain unusual design and structural features. The letter of intent for the Vought VS-315 (XF5U1) was issued September 17, 1942. The XF5U-1 was a twin-engine, single-seat, low aspect ratio flying wing type of airplane, manufactured by the Chance Vought Division, United Aircraft Corporation, Stratford, Connecticut. The first XF5U-1 airplane (Bureau Number 33958) was used for static tests; proof loads, extended to ultimate, largely confirmed structural design predictions. The second XF5U-1 airplane (Bureau Number 33959) was used for experimental flight test and concept validation. It was never flown because many hours of engine run-up showed excessive mechanical vibration between the engine-propeller shafting, gear boxes, and airframe structure. The airplane was taxi tested on February 3, 1947 at Stratford, Connecticut, but, again, vibration levels were considered excessive. The airplane was being readied for shipment by sea through the Panama Canal to Edwards AFB, California, when the contract was canceled (March 17, 1947) because of still unsolved technical problems and the lack of Navy R&D money. The jet age had arrived, but V/STOL had not. Basic characteristics were: Flying wing, elliptical platform The wing, the basic outline of which was defined by two ellipses, so arranged that the major axis of one coincided with the minor of the other, comprised the main structure of the airplane, with the exception of the pilot’s cockpit and the horizontal and vertical tail surfaces. The greater part of the wing surfaces and internal structure was composed of Metalite, a “sandwich” material providing a particularly strong and light type of construction. The four-bladed counter-rotating propellers were driven by cross-shafting and gear boxes connected to both engines. If one engine failed, it could be de-clutched from the system and the airplane flown with the remaining engine and both propellers operating. Circular air intakes in the wing leading edge provided carburetor, engine and oil cooling air. Two vertical tails with rudder and fins provided directional control. Two Metalite ailavators, with trim tabs across 70% of their trailing edge and with balance weights on the tips, provided lateral and longitudinal control. The pilot’s cockpit was a complete monocoque shell with a formed plexiglass canopy. The stick and rudder flight controls were manual except for proportional hydraulic boost to the ailavators. Neither the first nor second airplane had armament, although there were provisions for six 50-caliber machine guns and ammo boxes. Two Pratt and Whitney R-2000-7 radial engines with cooling fans and superchargers were mounted upright in the wing. The 16-foot diameter propellers were unique for the time and bear some mention. Because of the activity factor, twist and shape, the props were manufactured by Chance Vought Aircraft of Stratford, Connecticut. The two hydraulically operated, fast-acting, electro-mechanically governed propellers each had four Pregwood blades and load-relieving hubs which differed from the conventional four-way hub in that the blades were free to “flap” in pairs about the shaft axis. Low pitch stop was 15 degrees, high pitch stop was 70 degrees. The propeller pitch control set the left-hand propeller governor mechanism which controlled the right-hand propeller governor mechanism electronically and adjusted the propeller blade angle. Movement of the pitch control lever upward decreased pitch, and downward increased the pitch. Full forward position governed takeoff rpm (2,700): full aft position gave approximately 1,300 rpm in take-off slot and 800 rpm for flight. These were propeller rpm’s. There was also the more conventional throttle control which operated in three slots: “WARM-UP”, “TAKE-OFF” and “FLIGHT”. Rear View on 21 August 1947 with taped-on work areas and engine panels removed. The good size "stabilizing flaps " can be seen between the two vertical fins. Another unique feature of the XF5U-1 was the stability flap, located symmetrically about the centerline of the airplane at the wing trailing edge. The 15 sq. ft. hinged surface required no pilot control but automatically provided for change in airplane trim with change in attitude. The air loads upon the flap adjusted deflection against a spring loaded strut. The stability flap was linked to the tail wheel to insure locking in the up position when the tail wheel was extended. Mr. Matthews seems to be enamored of the XF5U-1. Also that we had whole squadrons of Go-229 (Horten) flying wings zooming over the snowy slopes of Mt.Ranier-in'47. Well, the Flapjacks were certainly cutting edge,but wrong edge,Propellers even those turned by gas turbines even the abilty to hover was secondary to going fast and far.The steam catapult, angled flight deck and far more relialble pure jets (also the breaking of the sound barrier) finished Propeller driven Naval Aircraft.Period ,no more,with the A-1 skyraider and the F4U- drived AU-2 soldiering on. Mr.Barrett Tillman is an execllent aircraft historian, his books on Naval Aviation are at the top of the Historian's Craft.-With no mention of any speculation of the XF5U-1 being other than a one-off (actually there was a static test airframe) prototype. Another source "U.S.Naval Fighters 1922 to 1980,s" by Lloyd S. Jones (Aero Pub. 1977.) has a very consistant, accurate,(and a great three view of the XF5U-1) account of the whole V173/XF5U-1 saga-including the Protoype's Demise at Edwards in a very public death by wreckingball,exactly 50 years ago to the day March 17,1949. Also contained in "Naval Fighters" is a history of all the Protoypes of fighter aircraft used by the US Navy.Insightful.Why fool around with nasty, unreilable turboprops such as the Allison T-40 the only reasonably available big (ah ,notice I didn't say reliable) Turboprop. by the time the XF5U-1 was at Edwards, the N. American F86/FJ-2 was already in production, along with the Grumman F9F Panthers and of course that particularly nasty surprise-the MiG-15 in Korea. It' easy to see why the XF5U had no merit because of the advances in Technology. The XF5U discoidal aircraft was an invention of Charles H. Zimmerman, who conceived the design in the early 1930s. He won a 1933 National Advisory Committee for Aeronautics (NACA) design competition with a disc-shaped concept capable of flying at high speeds or hovering; NACA rejected further development because they thought the design was "too advanced". Zimmerman was not discouraged and in his spare time built a number of test models, including a rubberband powered flying version. His original plan was an aircraft which carried three crew, in a prone position to allow maximum streamlining. The idea was subject to a 1938 patent he filed. Zimmerman joined Chance Vought Aircraft in 1937, and there was able to produce an electric powered model of his design, designated V-162, flown by remote control in test situations, tethered in a hangar. The rear fuselage was hinged to act as an elevator. Zimmerman provided an original blueprint to the US Navy (featuring no horizontal stabilisers) in March 1939. A month later, the Navy asked NACA (which later became NASA) to investigate the proposal. In October 1939 manufacture by Chance Vought of a small scale model for wind tunnel testing was approved. The design was referred to as V-173. This revealed problems with the trailing edge "ailevator" design, and horizontal "flying tail" stabilisers were introduced. After full-scale wind tunnel tests in September 1941 at Langley Field, Va., the Navy asked Vought to build two military versions of the aircraft, to be designated XF5U-1. One would be for flight testing and the other for static testing. The first flight took place of a V-173 on 23rd November, 1942. Soon after takeoff, Boone T. Guyton, Vought's chief test pilot, found the controls sluggish, and had to struggle to make a wide turn back to base. Otherwise the design was a promising one, and a wooden mock-up XFU5-1 was completed the following June. Flight tests progressed slowly but satisfactorily. On July 15, 1944, a development contract consolidated the V-173 and XF5U-1 programs. By the end of the V-173 flight tests convinced Boone Guyton and designer Zimmerman that the design had potential. They had faced financial and technical problems but had persisted. One major problem was the propellers, initially the same as those used on the F4U-4 Corsair. These had to be replaced with flapping blades to avoid vibration; a four-bladed design was finally produced, each propeller having one pair of blades staggered ahead of the other pair set at right angles. The twin 1,350 hp Pratt & Whitney engines gave the XF5U-1 an excellent speed range of 40 mph to 425 mph, much better than the usual 1 to 4 ratio of landing speed to top speed of other good designs. Water injected engines gave a 20-460 mph range, and gas turbines allowed 0-550 mph. The ship carried 261 gal. of internal fuel, and six 20 mm cannons, three stacked vertically in each "wing root". In June 1947, Boone T. Guyton flew the V-173 to Floyd Bennett NAS for a Navy Day display. As he neared the base, bathers on the Long Island Sound beaches saw a silver and yellow disc moving slowly overhead and rushed to report a "flying saucer". Guyton participated in the display then returned to the Vought factory at Stratford, Conn. This was the final performance of the Flying Flapjack. On March 17, 1947 the Navy had cancelled the XF5U-1 development, preferring to go with jet aircraft. The static test aircraft had already been demolished during laboratory tests, and the Navy ordered destruction of the flying version. Its engines, instruments and other salvageable items were removed and the airframe placed under the steel ball of a demolition crane. The first few drops failed to dent the aircraft. After careful measurements the ball was dropped between the main beams and spars, and the aircraft was eventually reduced to crumpled wreckage. The V-173 was approved for display at the Smithsonian. Air Age Publishing Apr 2005 Before the V-173 was flight-tested, the full-size aircraft was put through its paces in the Langley Field wind tunnel. Vought's chief test pilot, Boone Guyton, Richard Burroughs and several Navy pilots flew it for a total of 131 hours. It also made several forced landings because of mechanical problems, but there was little damage because it flew so slowly. Following numerous successful V173 test flights in 1943, the design work on the XF5U-1 full-power Navy fighter was begun. In planform, size and configuration, the XF5U-1 was identical to the V-173 prototype. The differences between the two lay in engine power and weight The V-173 weighed 2,250 pounds and-had 160hp. The XF5U-1 weighed five times as much and was powered by two Pratt & Whitney R-2000-7 air-cooled radial engines, each capable of 1,600hp. Propeller feathering could be adjusted by the pilot, and the articulation selfadjusted through 20, 1-degree arc positions. The XF5U-1 was designed to carry bombs or belly tanks on pylons under its wing. Its armament consisted of six, 20mm cannon, and its top speed was calculated to be around 500mpb with a range of approximately 1,000 miles. By March 1948, the work had been completed, but when further test were canceled, the Navy ordered Vought to destroy this remarkable aircraft and all the drawings and photographs pertaining to it! Fortunately, some photos and drawings did survive. The official explanation of the Navy's seemingly irrational decision to destroy all traces of the XF5U-1 was that it could now operate jet aircraft from its carriers. It considered propeller-driven fighters to be obsolete. Although it can't be substantiated, a more logical rationale for the destruction of the XF5U-1 might be found by taking a closer look at the official explanation. After the end of WW II but before the conflict in Korea, Congress was understandably reluctant to spend more money on the military. The Navy was seeking appropriations for additional carriers. If the honorable gentlemen on the hill were to learn that the Navy had a highperformance fighter that could be flown off any small vessel, why would any new aircraft carriers be needed? We can only empathize with Charles Zimmerman and imagine what he must have felt as he watched 15 years of pioneering work destroyed by a wrecking crew's steel ball. The real loss, however, is discovered in the realization that more than half a century ago, we were offered a new, potentially safer, form of flying. After the "Skimmer" program was ended, Charles Zimmerman returned to the Langley Research Center in Virginia and was eventually appointed director of aeronautics at NASA headquarters. One of Zimmerman's most intriguing theories was that of the vector flight principle. Canadian engineer Lewis McCarty adopted it to design and build one of the world"s simplest helicopters. With the DeLackner Aircraft Co., he built and successfully flew a number of very unusual rotary-wing aircraft. Luckily, the V 173 was spared the fate of the XF5U-1 and is now in the possession of the National Air Museum. Plans are in the works for a group of Vought retirees in Dallas, Texas, to restore this rare old bird. Before he died in 1996, Charles Zimmerman's lifetime achievements were recognized when he was made a Fellow of the American Institute of Aeronautics and Astronautics; he was also awarded the Wright Bothers Medal. -Frank Gudaitis SACK AS-6 In June of 1939, the first National Contest of Aeromodels with Combustion Engines took place at Leipzig-Mockau. Arthur Sack, who dreamed of a circular-winged aircraft, entered his AS-1 model, but unfortunately, it had to be launched by hand and had poor flying characteristics. Ernst Udet, who was at the time Germany's Air Minister, encouraged Arthur Sack to go on with his research. Sack built four additional models of increasing size, culminating with his first manned aircraft, the Sack AS-6. The AS-6 was constructed at the Mitteldeutsche Motorwerke company, with the final assembly taking place at the Flugplatz-Werkstatt workshops at the Brandis air base in early 1944. The AS-6 was a strange conglomeration from other planes, including the cockpit, seat and landing gear from an old, wrecked Messerschmitt Bf 109B and the Argus As 10C-3 240 horsepower engine from a Messerschmitt Bf 108 liaison aircraft. The wing assembly was new, with plywood forming both the ribs and covering. Ground taxiing tests were performed in February 1944, with the first test proving that the rudder was not strong enough and some structural damage ensuing. Five takeoff runs were made during the second test on the 1200 meter (3940') Brandis landing strip. During these tests, it was determined that the control surfaces were in the vacuum area behind the circular wing, and thus did not operate adequately. The right landing gear leg was also broken during the final attempt of the second test. It was thought that the problems arose due to the low power output of the engine, but because of a wartime shortage of more powerful engines, it was decided to change the incidence angle by moving the landing gear backwards by 20 cm (8"). Since the next wingspar was located 40 cm (16") farther aft, it was purposed to attach the landing gear here, but this introduced the problem of having the landing gear too far aft and thus the plane could tip forwards on takeoff, destroying the propeller. To compensate for this, brakes from a Ju 88 were installed, 70 kg (154 lbs) of ballast was added just ahead of wingspar number 3 and the tail control surfaces had 20 mm (3/4") of corrugated plate added. The third test took place on April 16, 1944 on the 700 meter (2300') Brandis landing strip. The plane traveled 500 meters (1640') without the tail lifting, although a small, brief hop was achieved. On the fourth and final test, the jump was longer, and the AS-6 became airborne, but an immediate bank to the left due to the torque of the engine became evident. The small span wings were too short to compensate for the engine's torque. The pilot recommended a more powerful engine and more wind tunnel tests, and Arthur Sack went back to the drawing board for the remainder of the war. During the summer of 1944, JG 400, who flew the rocket-powered Messerschmitt Me 163B "Komet", was moved to Brandis. They found the AS-6 there and tried to fly it, but the only attempt resulted in a collapsed landing gear leg. The AS-6 was damaged in a strafing attack during the winter of 1944-45, and was broken up to salvage the wood. All that was left was the miscelleneous metal parts, and these were thrown into the aircraft salvage area. In all probability, this is why American troops who entered the Brandis air base in April 1945 found no traces of the Sack AS-6. ZERO ASPECT RATIO ? Zimmerman Flying Platform "Whirligig" Charles Zimmerman conducted some of the more unusual vertical flight experiments of the late 1940s and early 1950s with several flying platforms controlled by the pilot's balance. These unusual aircraft successfully vindicated his belief in the feasibility of an extremely simple aircraft that flyable by anyone that was capable of riding a bicycle. Unfortunately, Zimmerman's prototype flying platforms were not scaleable into larger models suitable for production. However, several of the engineering principles pioneered in Zimmerman's projects have found new life in other segments of aeronautical engineering. Most notably, the ducted fan remains one of the most efficient means of vertical lift. The roadblocks encountered by Zimmerman and his successors have not stopped a number of dreamers and visionaries over fifty years later from attempting to create their own "flying carpets" that are similar to the ideas espoused by Zimmerman. Charles Zimmerman worked at the Langley Aeronautical Laboratory as an engineer for the National Advisory Committee for Aeronautics (NACA - forerunner of NASA) until 1938. He left to work for Chance-Vought developing his ideas for a Short Takeoff and Landing (STOL) aircraft, that eventually took form as the V-173 "Flying Flapjack" (see NASM collection). After the Navy cancelled an improved version (XF5U-1) Zimmerman struck out on his own to develop a small, vertical takeoff aircraft that an average person could easily fly. He hypothesized that if a small horizontal platform, with a person balancing on top, was lifted upward by thrust vectored downwards, then the pilot's innate kinesthetic responses would stabilize the platform and provide for pitch and roll control. Although the high center of gravity of such a configuration would seem inherently unstable, Zimmerman proved otherwise. Like riding a bicycle, if the platform tilted in one direction, then the pilot would naturally lean in the other direction to remain upright. This natural balancing tendency placed the center of gravity above the thrust axis, creating an upward pitching moment that counteracted the toppling action that resulted in neutral stability. The pilot could then control the aircraft by simply leaning in the desired direction and the platform would tilt and gain momentum. The gyroscopic action of the rotors further increased stability, and helped to dampen abrupt movements. In 1947, Zimmerman completed a prototype aircraft to validate his hypothesis. Known as the "Flying Shoes," this tiny construction consisted of a steel tube truss with two vertically-mounted 65 hp four-cylinder, two-stroke target drone motors driving 76 cm (30 in) diameter rotors. The pilot stood on top of the truss and relied on a vertically mounted pole for balance. The "Flying Shoes" flew no more than a foot off the ground while tethered. Because two motors almost never produced identical amounts of thrust, the platform exhibited considerable instability and tilted into the lower-powered engine, regardless of the balancing action of the pilot. Zimmerman filed a patent application for an improved model that surrounded the rotors with an airfoil shaped ring. This "ducted-fan" increased thrust by reducing the induced drag of the propellers, and increasing their efficiency, as well as creating a venturi effect that increased the airflow through the rotor. The net effect of the ducted fan was equivalent of using propeller blades 40 percent longer, but without the need for a bigger engine to drive them. In 1948, Stanley Hiller, president of Hiller Helicopters, became aware of Zimmerman's work, and seeing a future opportunity for his company, purchased the rights to the "Flying Shoes." Zimmerman was not interested in forming a business to pursue the development of his discovery and elected to return to Langley Aeronautical Laboratory to pursue his aeronautical research. Although, he made considerable progress in the advancement of hypersonic theory, he did not give up on his flying platform research. After discussing his ideas for a new platform with his superiors, they allowed him time to pursue the development of small flying platforms to support the growing interest in alternative forms of vertical lift. Determined to avoid the difficulties he experienced with the "Flying Shoes," caused by the differential thrust of its engines, Zimmerman came up with a novel solution. His next flying platform, known as the Jet Board, would not rely on any engines at all. Instead, it used pressurized air for thrust. The jet board deserves recognition the one of the simplest manned vertical takeoff aircraft in history. The 48 cm (19 in) x 74 cm (29 in) platform had foot straps for the pilot, a simple steel-tube landing gear, and connections for the two fire hoses that supplied the thrust from the ground-mounted gas bottles. The pilot wore a parachute harness attached by a static line to an overhead cable to prevent injury in case the operator lost control, though the platform itself was not tethered. Zimmerman made the first flight of his new platform on February 2, 1951. The platform was so stable that he did not even realize he had left the ground. Even in gusty winds, the intuitive balance response of the pilot was enough to keep the platform level. Zimmerman also experimented with small gas bottles mounted to the platform, which allowed it to fly freely, but with a very limited endurance. While the Jet Board underwent testing, Zimmerman began work on a rotor-driven model. This was necessary as the fire-hose/gas bottle system was clearly not practical for free-flying aircraft, and Zimmerman's funding originated from a NACA program dedicated to the construction of propeller-driven vertical flight aircraft. The new design, nicknamed the Whirligig, used a 2.13 m (7 ft) diameter twobladed rotor mounted on the underside of the platform. As on the Jet Board, a fire hose/gas bottle propulsion system powered the rotor with high-pressure gas exhausted at the rear of the rotor tips. However, the Whirligig's platform was considerably larger and heavier to prevent the pilot from inadvertently contacting the rotor. Consequently, the pilot had to use larger movements to make the weight-shift control more effective. A handrail surrounded the pilot, which allowed the pilot to make safe and smooth adjustments. The Whirligig made its first flight on October 21, 1953. Testing proceeded smoothly, first indoors, then outside. However, Zimmerman noted that the Whirligig was less stable than the Jet Board, especially in windy conditions. This resulted from the greater weight of the Whirligig, which made it harder for the pilot to adjust the center-of-gravity of the platform effectively. Additionally, the larger surface area of the platform created turbulence in forward flight, further reducing its stability, compared to that of the smaller Jet Board. The U.S. Army and Navy developed an interest in flying platforms as personal air scooters for a variety of military applications and subsequently issued contracts to Hiller Helicopters and De Lackner Helicopters for development of a practical flying platform. However, the Hiller VZ-1 and the De Lackner HZ-1 possessed several technical flaws that made them unsafe to fly operationally. On both designs, the high loading of the propeller blades prevented autorotation, and production models would have required a backup engine to prevent the fatal consequences of an engine failure. Combined with the substantial fuel load required for operational missions, the weight of the platforms exceeded the level at which weight shift alone could provide effective control, which necessitated control surfaces. This eliminated all of the advantages of kinesthetic control. The idea reappeared during the 1970s, in a project that relied on a reliable, lightweight cruise missile motor for propulsion. However, stability problems and noise issues doomed the project. Hiller and several other manufacturers experimented with the ducted fan in an Army "flying jeep" contract, but the performance levels of these machines fell below that provided by conventional helicopters, and budget priorities prevented further work. More than four decades later, similar flying car proposals occasionally resurface. Charles Zimmerman's flying platforms did not ignite a transportation revolution of the twentieth century, but are undoubtedly one of the most innovative approaches to vertical flight, and may yet have a role to play in personal transport. EXHIBITS Flying Platform: The Hiller Aviation Museum houses some of the most unique flying machines imaginable. One such craft, the Flying Platform, is the prototype developed from National Advisory Committee for Aeronautics (N.A.C.A.) engineer Charles H. Zimmerman's concept known as the "Flying Shoes". Charles Zimmerman, to the amusement of his engineering peers, proved the theory that rotors on the top (i.e. helicopters) are inherently unstable. Zimmerman theorized a person's natural balancing reflexes would suffice in controlling a small flying machine. Charles coined the term "kinesthetic control," similar to riding a bicycle or balancing a surfboard. Complementing Zimmerman’s "kinesthetic" theories, the Hiller Advanced Research Division (A.R.D.) incorporated a five foot fiberglass round wing, (ducted fan) with twin counter rotating coaxial propellers powered by two 44hp/4000 rpm, four cylinder opposed, two-cycle, Nelson H59 Engines. The Nelson engine was the first twocycle engine certified by the FAA for aircraft use. Utilizing the Bernoulli principle, 40% of the vehicle's lift was generated by air moving over the ducted fan's leading edge. The remaining 60% of lift was generated by thrust from the counter rotating propellers. Hiller Helicopters, on 17 September 1953 signed a contract with the Office of Naval Research's Naval Sciences Division (ONR) to incorporate Alexander Satin's ducted-fan research with Charles Zimmerman's "kinesthetic" theories. The classified project was turned over to the ARD at Hiller Aircraft, and construction began in January 1954. Nine months later the ARD group, working in complete secrecy, delivered the prototype model 1031 Flying Platform. The first free flight of the Flying Platform took place on 27 January 1955, and went in the record books as the first time man had flown a ducted fan vertical take off and landing (VTOL) aircraft. In April of 1955 the veil of secrecy was lifted and all the world wanted a vectored thrust vehicle for their own NASA PIONEER DIES; HE REVOLUTIONIZED AIRCRAFT, FLIGHT TESTS DATE: Wednesday, May 8, 1996 Charles H. Zimmerman, an aerospace research pioneer at NASA's Langley Research Center, died Sunday in Hampton. He was 88. He joined the Langley Laboratory of the National Advisory Committee for Aeronautics, forerunner of the National Aeronautical and Space Administration's Langley Research Center, in 1929. He conducted studies on aircraft stability, tail spinning and low-aspect-ratio airfoils. He wrote several NACA reports on his airfoil concept. ``Charlie was a great inventor. Those airfoils were like early unidentified flying objects,'' recalls John Duberg, a fellow researcher who became an associate director at the Langley center from 1975 through 1980. Zimmerman invented the world's first free-flight wind tunnel at the Langley center and was in charge of the development and testing of the original NACA free-spinning wind tunnel. He also invented a V/Stol (vertical/short takeoff and landing) flying wing aircraft in the 1930s. In 1937, Zimmerman joined the Chance Vought Division of United Aircraft Corp. to supervise construction and flight testing of the V-173 Flying Wing and construction of the XF5U-1 flying wing fighter. In 1948, he returned to Langley to supervise research on aircraft stability and to lead research on advanced aircraft wings. He was one of a three-man study group who recommended in 1953 that the nation become involved in research for space flight. He headed the Space Task Force in NACA headquarters in 1958, then became chief of the engineering and contract administration division for Project Mercury, the nation's first manned space flights. In 1962, Zimmerman was named director of aeronautics at NASA headquarters in Washington. A year later, he became chief engineer and retired in that position at the U.S. Army Materiel Command in 1967. A memorial service will be held at 10 a.m. Wednesday at St. John's Episcopal Church in Hampton. Assembly instructions for the FMX-4 “Facetmobile” About the Facetmobile The FMX-4 Facetmobile is the creation of aviation engineer Barnaby Wainfan. It is a homebuilt, one-person aircraft designed on the lifting body principle. Unlike a conventional aircraft, where lift is created by wings, the entire body of the Facetmobile generates lift. The FMX-4 has flown over 130 hours since 1993 and has apparently very good flight characteristics. In 1995 the plane was damaged when an engine failure caused a forced landing, but it is presently being repaired and will some day fly again. A larger two-seat version is also planned. More information about the Facetmobile can be found on the internet at http://users.aol.com/slicklynne/facet.htm The Model This model builds into a 1:48 scale replica FMX-4. It may be built as either a static display model or a glider. A word of caution: this model is not suitable for assembly by very young children, due to the use of sharp tools and the complexity of some assembly steps. Previous experience with card modeling would be helpful. If you have any comments or suggestions regarding this kit, I can be reached by e-mail at [email protected] Model parts are contained in the document fmx4_parts.pdf. Print out the parts document on 8.5"x11" or A4 size white paper card stock suitable to your printer. 67 lb. cover stock (approx. 8.5 thousandths of an inch or 0,2 mm thick) is recommended. Tools Before beginning, you will need the following tools and materials: a) a sharp knife for cutting e) a scoring tool or blunt knife for creasing the fold lines b) a flat cutting surface f) a glue applicator such as wooden toothpicks or a small paintbrush c) a ruler or straight edge g) (for static display model only) a paper clip or similar stiff wire d) white glue h) (for static display model only) needle-nose pliers to bend wire to shape Hints a) b) c) d) e) Select a well-lit, comfortable work area that will remain undisturbed when you are not there. Keep your hands and tools clean when working, to avoid getting glue on visible parts of the model. It’s easier to stay organized if you only cut out those parts you need for each step. Make sure your knife is sharp. When cutting straight lines, use a straight-edge. Study the diagrams carefully, and always test-fit the parts before applying glue Assembly In these instructions, the directional terms are given from the pilot’s point of view. “Port” and “starboard” refer to left and right sides respectively. Scoring of parts is indicated by thin black lines outside the part’s outline, and by dashed or shaded lines on the part’s surface. Score parts before cutting them out. In the diagrams, subassemblies are identified by a number within a circle (e.g. ), corresponding to the step in which it was assembled. (Step 1) fold and glue the internal formers to the non-printed side of base A5. Attach A15 first, aligning the bottom fold with the front fold line of A5. Glue A8 to the base and to the shape printed on A15. Fold and glue the inside tail fins, and attach to the base (step 2). Add nose weight to the base (step 3). If building a glider model, a weight of 2.5 grams (roughly the weight of a U.S. penny) is recommended. For a static display model, use two pennies (5 g) or more. Attach connecting strips A4 to the non-printed side of top surface A1 (step 4). Glue the upper body to the base (step 5). This is best done by gluing the rear control surfaces together first, followed by the middle glue tabs on the upper body. Finally, attach the nose section of the upper body to the base, using the front tabs and the connecting strips as gluing surfaces. Add the upper engine housing A9 using the locating slots (step 6). Fold and attach the outer fin surfaces A2 and A3. If building the static model, cut and bend a paper clip or other stiff wire to the shapes shown on the parts sheet. Slide plate A11 over the nose strut and glue to the model underside (step 7), ensuring the strut lines up with the printed locating guide. Attach the lower engine housing A14 using the locating slots (step 8), sliding over the nose strut if present. Glue the engine plate A12 to the front of engine housing. The remaining steps are only applicable to the static display model. (Step 9) attach the main struts to the mounting plate A13, sandwiching each strut between the side flaps of the mounting plate. Glue the plate to the model underside as indicated by the printed shape. Glue the propeller halves together (step 10) and attach to the aircraft nose. Assemble the wheels and attach them to the wheel struts. Flight (glider version) First attempts at flight should be done in a grassy or carpeted area to avoid damage to the model. Bend the rear control surfaces up slightly and throw the model forward. Try different rudder and aileron positions to see what works best. fmx4_inst.pdf v1.0 August 2002 © Ralph Currell www.currell.net Page 1 of 2 1 A15 Internal structure 2 Attach this part first. A8 3 Nose weight Upper body connecting strips Flying model: use 2.5 grams (1 penny) A10 A4 Static model: use 5 grams (2 pennies) or more A1 A5 Open slots (2 places) (Inked side facing down) 4 (Inked side facing down) 5 Fins (inside surfaces) Attach upper body to base A7 Glue upper body to base in three stages: port top A7 Open slots (2 places) First Top view of finished assembly Glue tabs together as shown port top 3 Second Third (also glue body surface over connecting strips added in step 3) 4 A6 (mirror image of A7) 6 7 Fins and upper engine housing A2 8 Nose wheel strut (omit this step if building flying model) Lower engine housing A14 A11 N11 Slide over strut, if present Slide over strut 7WD Nose strut A3 A2,A3 (mirror image) A9 N11 Make from paper clip using template on parts sheet 7WD A12 9 Main wheel strut (omit this step if building flying model) 10 Wheels and propeller (omit this step if building flying model) A17 A16 Assemble as shown A18 2 pieces Main strut A13 Make from paper clip using template on parts sheet fmx4_inst.pdf v1.0 August 2002 © Ralph Currell www.currell.net Page 2 of 2 ins A Nose wheel cm Main gear top view front view 1 Open slots in nose (2 places) W D side view 11 7 2 N 3 N D W 11 7 4 5 Open slots in nose (2 places) ar bo ar d to p 6 po r tt op st ins Templates for landing gear struts (paper clip or other stiff wire) 8 7 9 10 11 Open hole 12 15 16 14 18 Open hole 13 Open hole (2 places) 17 Open hole (2 places) fmx4_parts.pdf v1.0 ©2002 by Ralph Currell cm A Design Group 2 Meeting # 5 April 15, 2006 10:00 am M eeetting ing S chedule: Me Schedule: 2006 Meeting Schedule 10:00 am FlaBob Airport Chapter One Hanger April May June July August September October November December At FlaBob Airport 15 27 24 15 26 16 28 18 16 Check this site for any schedule updates and changes. In Chapter One Hanger http://www.eaach1.org/calen.html Check this site for newsletters http://www.eaach1.org/design.html John D. Lyon Will present at the next meeting Thoughts on a Project to Reproduce the Lockheed Model 33 "Little Dipper