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CONTACT! ISSUE 110 PAGE 1
Article and photos by Anthony J. Liberatore Many a pilot has been attracted by the allure of the amphibious aircraft. With the amphibian’s ability to make your favorite lake not only a runway but also an adventure, who could resist? But as some of us are aware, owning and operating an amphib is not all that easy. With the added complexity and maintenance just for starters, ownership is certainly a challenge with a production bird let alone an experimental. However, there is one individual who not only has succeeded within the experimental, amateur-built rules (while incorporating a host of other enhancements that have truly improved the breed), but has done so with an automobile conversion. That individual is Randy Hebron.
Contemplating and executing such changes was not a stretch for Randy, given his homebuilding background; in fact his name may ring a bell with many KR enthusiasts. In the late ‘70s, Randy and his brother Scott built a highly modified KR-1 that was featured in the July 1980 issue of EAA’s Sport Aviation Magazine.
Randy purchased his VJ-22 Sportsman amphibian in damaged condition after an accident in 1982 destroyed its fuselage, forward of the wings (see the 1987 Water Flying Annual). After his completion of the rebuild process, Randy continued to fly N6857 with its Lycoming O235-C1 mounted in the tractor configuration. This continued for 12 years until one day while airborne, the Lycoming stuck a valve. Fortunately, Randy was flying over a Michigan lake and he proceeded to execute a safe emergency water landing. It was in the initial stages of the engine rebuild that Randy started to give serious consideration to an auto engine conversion, primarily in response to the sticker shock while pricing out a set of rings for the aged Lycoming.
A vintage photo of Randy’s VW powered KR-1, as featured in the August 1980 issue of Sport Aviation. The article was written and the above photo was shot by then Editor, Jack Cox. Jack is now publishing his own aviation magazine, Sportsman Pilot.
A NEW ENGINE
With that “can do” attitude and experience, Randy chose to replace the Lycoming in the Volmer with a Subaru EJ22. With its water cooling, electronic fuel injection, and many other features, it is truly a modern engine. In order to get the propeller tip speed subsonic for this amphibi-
Although the Volmer flew fine with the Lycoming in the tractor configuration, an additional goal of Randy’s was to turn his Volmer back to the original pusher configuration and move the propeller farther away from the cabin. www.ContactMagazine.com
With its updraft cooling, full span flaps, spoilers, and GAPC-1 airfoil, the highly-modified KR-1 was capable of a top speed of 179 MPH on a 1600cc VW engine and a stall speed in the 45 MPH range. While competing in the Lowers-Baker-Falck efficiency and speed competition in 1981, Randy's highly modified KR-1 was a strong contender. In fact, during the Baker portion of the competition, Randy and his KR-1 took 2nd place
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MODS
an’s installation, Randy utilized one of Don Parham’s RFI Power Systems* belted redrives for a pusher-mounted prop. Randy’s overall execution of the Subaru installation in the Volmer is quite conservative and, in fact, is an exercise in common sense. Randy’s installation predates Steve Lantz’ Robinson Conversion Chevy powered Lake Tahoe Special (Experimental Seabee, see CONTACT! Magazine issue #81) by a number of years and actually follows the same common theme of keeping the engine as stock as possible and the installation as simple as can be.
Once the Subaru’s engine installation was completed and test flown, Randy proceeded with a host of modifications to enhance the Volmer’s performance. For starters, different propellers were tried: a Warp Drive and a borrowed Prince Prop but ultimately Randy, in true homebuilder fashion, carved his own. The current hand carved propeller is based on tried and proven NACA planform and twist distribution, and appears to be robust. Along the way, the propeller was “dimpled” to compliment the Hoerner style prop tips, which were an original feature when it was carved. The results of the “dimpling” were profound, netting an increase of 100-RPM static and a 1 inch drop in manifold pressure on climb-out.
SIMPLE IS USUALLY BETTER As examples of simplicity, Randy utilizes the stock ignition and electronic fuel injection. A stock Hyundai radiator is used as well, although mounted at an angle for a lower cowling profile. After building some time on the Subaru installation, Randy noticed that his engine oil temperature would occasionally go higher than 220°F, a temperature he was not comfortable with. Randy’s solution (mirrored by the Lake Tahoe Special) was to route the engine oil though the automatic transmission cooler which is integral to the radiator. This change helped to keep the engine’s oil temperature within the green arc. What I find particularly noteworthy is that two homebuilders independently developed nearly identical solutions to overcome some of the technical and design concerns associated with their auto engine conversions geared towards amphibious use.
For more information on the RFI belted redrive, visit www.geocities.com/rfisubaru/rfi.html or contact Don Parham, RFI Power Systems P.O. Box 263 Indianola, OK 74442 Phone: 918-823-4610 Fax: 918-823-4690 e-mail rfi@oklatel.net www.ContactMagazine.com
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propeller installation’s noise signature is no more obtrusive than a current generation personal watercraft or family boat. After taking off from water or land, the Volmer just seems to levitate and reaches pattern altitude rather quickly. On the water, with two aboard and using the one-thousand-one, one-thousand-two counting system, once power is fully applied Randy’s Volmer is off the water consistently in the 10-13 second range, as was observed during a recent EAA Chapter “Splash-In,” in which many different passengers occupied the right seat. One might say Randy’s Volmer is “dialed-in” and really gets out of its own way!
This is not the best shot to illustrate the installation of VGs along the upper surface of the wing, but I just like this photo. ~Pat Attention was further directed towards the Volmer’s aerodynamics by fabricating and installing vortex generators (VG). These were not only added to the traditional VG locations such as the wings and underside of the horizontal stabilizer, but to the cowling and on the fuselage between the engine’s pylons struts. The net effect of all these changes is to make this Volmer a winner, and in fact Randy has a number of “1st Places” to prove it. At the Annual Oswego Seaplane Fly-In in Michigan held every June, Randy has been the guy to beat the last few years in the takeoff contest for his horsepower class, which includes Super Cubs on floats! At this competition (lightly loaded) Randy has been timed off the water in 8 seconds. One other aerodynamic modification that may go unnoticed by folks not familiar with the Volmer is an extended rudder. Randy performed this modification, obviously, for greater rudder authority.
Randy and his Volmer are shining examples of the EAA and American “can do” spirit, and once again shows that with hard work and ingenuity you can improve the breed. On top of his volunteering as a Technical Counselor for his EAA chapter “The Backyard Eagles” (Chapter 113 www.eaa113.org) in Canton, MI, Randy has graciously shared his Volmer with many others by giving them rides in the right seat. Especially when their ride originated on the water, the passengers have all shared one thing in common post their flight— a grin from ear to ear. Myself included.
GETTING A SET OF PLANS The Volmer Club, Inc. is a non-profit, 501 (c)3 corporation that is run by a few volunteers. There are no paid employees or officers and we derive our operating expenses from the sale of information packs and VJ-22 plans sets. (See the facing page.) We are simply trying to preserve this great old amphibian design and see that Volmer Jensen receives his due recognition for the 24 or so experimental aircraft he designed during his career, the VJ-22 being by far the most popular.
Even those not intimately familiar with the VJ-22 might comment that the rudder is a bit large. Note the line drawing in the accompanying side piece for an example of a “stock” rudder.
FLYING QUALITIES The author has been fortunate not only to be an observer of N6857 but has had the pleasure to be a passenger as well. Although they are not scientific, here are some of my observations. From the shoreline, the engine/ www.ContactMagazine.com
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A BRIEF HISTORY OF THE SPORTSMAN. Construction of the original Chubasco (later renamed Sportsman) was started in September of 1957 and was completed December, 1958. The construction of the rigid and corrosion-proof hull is of 1/16 inch and 3/32 inch aircraft mahogany plywood with 1/4 inch plywood at the step for maximum strength. The hull is further covered with fiberglass for added protection. Rigorous and numerous tests, from calm water to five foot swells in the open sea, have proven the design to be both extremely airworthy and seaworthy. Take off from water at sea level consumes about 20 seconds. The VJ-22 Sportsman has useful features not usually found on other aircraft. Two such notable features include the distinct advantage that a pusher-type of pylon engine mounting allows for excellent visibility, while keeping the propeller up and away from human contact.
www.VolmerAircraft.com
TECHNICAL FACTS Volmer VJ-22 "Sportsman", amphibious flying boat. Two-place, side-by-side, closed cabin, high-wing monoplane.
Plans and Information Packets The information packet contains a detailed description of the aircraft, components and systems. There are construction photos, details of the materials used and construction techniques. Also included is a description of the plans package with a copy of the plans purchase agreement.
DIMENSIONS Length 24' Height 8' Span 36'-6�
WEIGHT Empty 1,000 lbs Useful load 500 lbs Gross weight 1,500 lbs
POWER PLANT Continental C-85, starter and gen. Fuel consumption 5.0 gals per hour (Engines up to 125 HP can be and have been installed)
PERFORMANCE Vne 95 mph Cruising speed 85 MPH Stalling speed 45 MPH Climb 600 FPM Ceiling 13,000'. Maximum range w/20 gals of gas 300 miles
Info Packet prices, including shipping: $15.00 for U.S. customers. $20.00 for Canada and Mexico. $25.00 for all other countries Plans for the VJ-22 sell for $250.00 US Includes 23 sheets of blueline drawings. In addition, there are several pages of building notes, comments by the original designer and approximately 80 construction photos. Plans’ shipping charges: US $19.50 UP'S Ground Canada $20.00 UPS Ground All other foreign customers $25.00 Surface $50.00 Air Mail. All payments must be made in U.S. Funds. All plans purchases must include a signed copy of the Purchase Agreement that is included in the information package.
CONSTRUCTION
If you want to purchase the plans without first obtaining an information package, then contact us so we can mail you a copy of the Purchase Agreement.
Wood hull aircraft mahogany plywood and spruce, fiber-glass covered. Wings-Aeronca Chief or Champion, wood spar, ribs, fabric covered. Conventional, manually repositionable landing gear, swiveling tail wheel and water rudder retractable.
How to order your Volmer VJ-22 Plans E-Mail Volmer Club of America RJAFLYS@aol.com or Volmer Club of America, Inc. 536 Oak Ave., Bridge City, LA 70094
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application of Sonex’s technology in the field is a number of 2-Stroke 100cc powered UAV’s converted to run on JP-5 for the U.S. Marines. (see photo below) Sonex has two variations of there technology still in the R & D mode. With these variations, one is touted to make diesels run cleaner and the second could allow the elimination of a spark source when direct fuel injection is used while at the same time allow heavy fuel use. Note this is a small and relatively new firm and many of these projects still may need some maturation. By Anthony J. Liberatore Images courtesy www.sonexresearch.com Imagine with today’s fuel prices, you are able to pull your aircraft up to the Jet A pump to save a little on your fuel bills. The concept is tantalizing, although I have been told it is nothing new. In order to help the war effort during WWII, some farmers would switch over to kerosene after getting the engine on their tractor warmed up. With a new war effort underway, a new military requirement has emerged that is a technology driver. This requirement is that all GPU’s, UAV’s, etc, with small engines, must run on JP-5 by 2010, in order to eliminate the logistics of carrying different fuel types into a theatre. This requirement is driving a number of manufacturers and entrepreneurs to use their creativity and come up solutions to fill this need. Some of the current entries with some unique solutions are Evan Guy Enterprises, Dan Gurney (of racing fame), Sonex Research Inc. (not to be confused with Sonex Ltd, the kitplane manufacturer), and Mercury Marine. While there are some true diesels such as the Deltahawk that are trying to fit in and fill a given role as an UAV engine, the thrust of many of these innovators is to modify existing engines to run on “heavy fuels”. With that said we might never see general aviation applications for a long time if at all. In fact with today’ s emission regulations, any application outside the military may never come to fruition. Nevertheless, the concept is so tantalizing we cannot help but dream of what an engine this would make for our aircraft. What they have created with these “spark ignited heavy fuel engines” is an engine that can burn a diesel type fuel without the high diesel compression ratios normally needed for the combustion process, and without the associated high engine weight required for strength. It gets even more enticing; many of the engines they are converting are two strokes, which are even lighter than the small certified engines we are accustomed too. With that said, I would like to discuss two of the entrants and their interesting technological solutions. One of the entrants is a company out of Annapolis, Maryland: Sonex Research Inc. Sonex’s unique and patented approach uses a design that can be applied to the cylinder head or the piston. This design utilizes a center chamber that has a series of smaller chambers surrounding it (see image to the right). The outer chambers are connected to the center chamber via individual passageways. A current www.ContactMagazine.com
Two Stroke 100cc powered UAV converted to run on JP-5 for the U.S. Marines. Another interesting entry in this arena is the “Optimax JP” outboard engine by Mercury Marine. Mercury Marine is developing an outboard and a “jet” (both in the 200+hp class) for Navy “Seal” use. This Optimax JP is a derivative of their successful Optimax Series of outboard motors, which range from 75 hp up to 250 hp, and are direct injected two strokes. Direct injection applied to a two stroke gives the engine its inherent light weight, with 4stroke fuel consumption and emissions, as well as a more robust lower end, since the crank and rods bearings are not exposed to fuel diluted oil. These direct injected two stokes utilize Orbital Engine’s air assisted direct injection technology which atomizes the fuel droplets down to 8 microns, which is the industry benchmark. The flexibility of this system allows Mercury Marine to convert the engine to heavy fuel while maintaining 95% part compatibility with their gas burning brethren. As you might garner, what is going on in this arena is definitely on the cutting edge. However, we as aviators and experimentors have always been on that edge when it comes to applying technologies. Perhaps a two stroke direct injected, spark ignited heavy fuel engine, with an excellent power to weight ratio and great fuel consumption specifics would drive a new generation of airframe designs. Not to mention it would be neat to taxi to the jet A fuel pump and filler up! Anthony J. Liberatore aliberatore@comcast.net
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which in aircraft form, acts as a fulcrum. This new support is commonly referred to as the “fifth bearing”. I had the pleasure of visiting one such experimenter, Mr. Roy Szarafinski at his shop in Osseo, Michigan.
ROY’S GARAGE
Story and photos by Anthony J. Liberatore aliberatore@comcast.net What Roy Szarafinski (EAA 665642) may lack in social skills and graces he more than makes up for in technical skill, critical thought and having a keen grasp of the obvious. He is largely self-taught but has been fortunate to have been mentored by some extremely talented machinists, welders, mechanics and other fine people. During his automotive repair career Roy has literally worked on technology spanning a century, from designing and installing “juice brakes” on a 1904 Buick to solving drivability issues with late model vehicles. His machining and in-depth engine experience ranges from pouring and machining babbitt bearings for antique engines including Rolls Royce and Packard to complete engine rebuilds on vehicles the likes of Porsche, Austin Healy, Maserati, Ferrari, Mercedes and BMW just to name a few. Roy’s practical experience to date culminates in his 5th bearing design and ignition solutions. Roy is scratch-building a Zenith CH-701 and will be installing a full FADEC (full authority digital engine control) Corvair engine. As many of readers of CONTACT! Magazine may be aware, the popularity of the Corvair engine for experimental aircraft has increased dramatically in the last few years. Many owe a debt of gratitude to the efforts of William Wynne and other Corvair enthusiasts such as Mark Langford. As many of you may also be aware, Mark has experienced two in-flight crankshaft failures and reported his first such failure as recently as issue #85. Concluding (or deducing) that the fracture is from bending and not torsional vibration, the situation has many in the Corvair community investigating (designing, building and testing) some form of additional support between the prop flange and the last (4th) crankshaft main bearing, www.ContactMagazine.com
Upon approaching Roy’s facility, one couldn’t guess that in this building some serious machining and aircraft tinkering were afoot. We were warmly greeted by Roy when CONTACT! visited in June of 2008 and we couldn’t help but notice a Zodiac 701 in progress, a motorcycle being worked on, a wide array of serious machines, blues music playing through the stereo and a guitar in the corner. Not only is Roy an experimenter, but he may also have the ultimate “man cave”!
The man cave is a menagerie of equipment parts, projects, everything a serious tinkerer or serious craftsman needs to have fun. Before we get into the details of Roy’s efforts, please note that Roy’s current fifth bearing arrangement has not yet been test flown. However, 8/23/08 was a milestone day for Roy as on that day not only did Roy’s fifth bearing come to life mounted to the his 701’s firewall for a ground run, but his experimental fuel and ignition systems ran in unison with it as well.
WHY THE CORVAIR? Roy’s involvement with Corvair engines started when a friend offered him a core (at a reasonable price) for use in his 701 project. Upon teardown and inspection, Roy had some ideas of his own on how he wanted to approach his conversion including supporting the business
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end of the crankshaft. Roy’s methodical approach to his fifth bearing support could be described as a desire for additional bearing support to absorb propeller loads, born out of common sense and practicality.
DETAILS While Roy was very open in explaining his fifth bearing with CONTACT! Magazine, some of the details discussed (such as materials and methods) are considered proprietary and will remain as “background” information and won’t be disclosed in this article. Roy is pursuing his fifth bearing with a single goal in mind: reducing the cyclic bending stress imparted to the 4th main journal and 6th rod journal throw. The stock Corvair bellhousing that is normally trimmed and recycled as the “front cover” when converted for experimental aircraft use is replaced with a more robust split-case bearing support that is located with a high degree of precision. This new two-piece unit, which is machined from aluminum billet, is split vertically to match the existing engine case halves and in essence becomes an extension of the case. An interesting note: although Roy utilized a 2D CAD package in laying out the overall design of the bearing support, the machining is done by hand, not via the 3D solid model “art-to-part” methodology. Having seen these parts in person, not only are they visually impressive but they are a testimony to Roy’s machining skills.
BEARING The new, non-standard bearings which will support the new journal and reside within the new front case are of automotive origin, i.e. big-block Detroit iron off the shelf items. To seal these plain bearings, a main seal of unique properties and an exact fit to the journal diameter is affixed to a machined circular plate and is fastened to the new front cases with six Allen screws.
JOURNAL The new fifth bearing crankshaft journal is a familiar sight to Corvair enthusiasts but with a new twist. The stock crank gear with its integral rear seal mating surface is utilized with an extension of the sealing surface welded on for added length and then is precision-ground and nitrided. This then forms the new crank bearing journal for the fifth bearing. While discussing this added bearing length with Roy, he explained that while there is an interrupted surface between the new support outer face and the inner face of the first main crankshaft journal, the effective bearing length is just shy of 3.00”.
Shoulder bolts are used most commonly for accurate locating or pivot/slide mounting points. Also known as “shoulder screws” or “stripper bolts”.
Part of the process that ensures the precision of the new bearing support is that the final procedure calls for it to be machined as an assembly with the original Corvair engine case halves. The two halves are attached via eight fasteners, four of which are of the shoulder bolt variety and have almost an interference fit. Once bolted in place, the stock engine cases with the new front extensions are secured to a jig as a single assembly and are align-bored to ensure the concentricity of the bearing surfaces to the crankshaft centerline. The fixtures and tools that accomplish this task are an amazing utilization of standard automotive machine shop tooling that gets the job done. www.ContactMagazine.com
In this application, the non-threaded portion of the shoulder bolt becomes an alignment dowel.
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The new journal extension is welded to the crank rear seal mating surface and is then precisionground as shown in the photo to the right. As a reflection of Roy’s practical approach to his fifth bearing please note that this welded-on crankshaft extension is still compatible with William Wynne’s front mounted starter and prop hub. With the added length to the crankshaft, one might gather that Roy’s entire assembly would increase the overall engine installation length and complicate the fit under a given design’s cowling. However, Roy notes it is possible to remove some material from the backside of William Wynne’s prop hub (1/2”) to reduce the entire assembled length to only 7/16” longer than a typical (William Wynne) front mounted starter conversion.
The cam gear separating the 4th main journal from the new 5th is illustrative of all of the applications discussed in this issue. The final goal of supplying lubrication to the fifth bearing is accomplished via an external stainless steel braided line, ported into the left front case-half oil gallery. The return is accomplished by draining back into the oil pan via machined passages. Overall, the net effect in terms of weight of Roy’s fifth bearing setup is about a 3.5 pound increase to the engine’s all-up weight.
DUAL PLUGS While Roy continues to develop his fifth bearing support, it’s not the only inspiration from his fertile mind. As mentioned previously, Roy has also modified his cylinder heads to incorporate dual spark plugs. This is accom-
This image shows the overall design, but what may appear to be asymmetry is that there is a plain bearing half in the left half of the front cover. What’s not shown is the oil seal cover and the oil supply line. www.ContactMagazine.com
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Hours before going to press, Roy sent me the following note. ~Pat
plished by welding closed the existing spark plug hole and machining away cooling fins to create a surface sufficient to accommodate two 10mm NGK “peanut” plugs tapped into the head on either side of the original sparkplug location.
The coil-on-plug ignition is working flawlessly. I had hoped for a noticeable difference between running each system separately (six spark plugs firing) versus together (12 spark plugs firing). There was about a 20 rpm difference while the EFI was in warmup mode and under moderate load. However, once warmed up, switching between one or both systems produced no noticeable difference under full load. I was hoping for some icing on top of the redundant ignition cake. Oh well, I am happy with the cake.
IGNITION SYSTEM The coils that fire these plugs are off-the-shelf Dodge “Hemi” coil-on-plug units, which have an additional lead which allow six coils to fire all 12 plugs. The coils are fired via two General Motors DIS (Distributorless Ignition System) ignition modules, each with its own crank trigger thus employed to fire all twelve plugs and being truly redundant. These crank triggers are located at the accessory end on a pulley that replaces the harmonic balancer. Roy is aware of the potential ramifications of the removal of the harmonic balancer from the system and will be following the potential vibration issues closely. Attached find a pic of the O-ring mod for the intake log. Because this engine is the beta version of the EFI and dual plug conversions, I wanted flexibility in the runner mounting, besides it offers accessibility for cleaning if required. In the top view of my engine, note that the cooling plenums, which act as the coil mounting, are tapered toward the back. This is to maintain even static pressure across the top of the cylinder heads. It works as designed; temp readings measured with an infrared temp gun show consistent readings after shutdown from a sustained high load runup. EFI is controlled with a Megasquirt 1 and my harness is wired for redundant controllers.
INDUCTION SYSTEM Roy’s creativity does not end there; his top-mounted induction system is a highly modified dual-point throttle body injector unit that is off a 1989 Honda Civic. This system incorporates a throttle position sensor (TPS) so as not to require a change to the ECU (engine control unit) source code, but the controller is a do-it-yourself unit that has allowed Roy to fine tune the mixture via his laptop with the engine running under all load conditions. Roy’s efforts to develop not only a fifth bearing support but ignition system and fuel system innovations are no small feat. We look forward to hearing about his progress as he pursues his evolving vision of the Corvair engine for experimental aircraft engine applications. To follow Roy’s progress, check out his website at: www.roysgarage.com www.ContactMagazine.com
I have updated my shop to include a 3-axis NC mill and I am currently building five fifth bearings, four of which will have the CNC housings. Of course each housing will still need to be matched with the case by line boring to achieve proper shaft alignment and clearances. I am glad to hear the two Marks’ vibration reduction reports, as this attests to the suitability of the concept. Roy Szarafinski 3564 Hudson Rd Osseo MI 49266 517 610 2307 rvickski@yahoo.com
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By Anthony J. Liberatore Photos and images courtesy of Hirth & Orbital, Bob Skingley, and Anthony J. Liberatore aliberatore@comcast.net In issue 78 of CONTACT! Magazine, Anthony authored the article, “Is there a Spark Ignited Heavy Fuel Engine in your Future?” Never in his wildest dreams did he anticipate that in less than a year later, an engine of this type would emerge for Unmanned Ariel Vehicle (UAV) applications, manufactured by a name known to experimental aviation enthusiast, Hirth Engines. With that in mind, what is the possibility we will see some advanced technologies like this become available for the homebuilt aircraft enthusiast? Before that question is answered, Anthony gives us some background on Hirth’s current efforts and their journey into this arena. In a press release dated 02/15/2005, Hirth Engines announced that they were launching a 45kw twin cylinder, two-stroke engine, capable of burning heavy fuels (JP5 JP8) to meet the 2010 NATO and US Military requirements to eliminate gasoline from the battlefield for safety and logistical reasons. A key enabler that Hirth chose to meet this requirement was to become a licensee of Orbital’s Air Assisted Direct Fuel Injection and incorporate this technology into these new engines.
Orbital Australia Pty. Ltd., based out of Perth Australia, developed their Orbital Combustion Process that is based around their highly patented Air Assisted Direct Injection, also referred to as AADI. These injectors are similar to current fuel injectors in terms of operating pressure, but also utilize compressed air (supplied by an air compressor) to further atomize the fuel, preparing it for the combustion process. This air-assist atomizes the fuel droplets down to 6-10 micron SMD, which is the industry benchmark. (SMD = Sauter Mean Diameter: a way of comparDiesel Fuel Gasoline Fuel 10 mg/shot 10 mg/shot ing the atomization 6.8 micron SMD 5.7 micron SMD performance of different injectors). Typical Orbital spray pattern.
A cross section of a Orbital/Synerject Air Assisted Direct Fuel Injector (AADI) This technology is utilized by a host of Orbital licensee’s such as: Aprilia Scooters DITECH® engines, Mercury Marine’s Optimax® outboards, Bombardier’s 3D® PWC, and Tohatsu’s TLDI® outboards, which are all gasoline two-stroke applications. The application of this AADI to two-stroke engines changes the emissions and fuel consumption of these engines dramatically, in a positive way. In fact, fuel consumption drops some 40% (giving parity with 4 strokes) and emissions drop in the order of 80% over a carbureted 2 stroke. This is not only due in part to the direct injection, but the fact that the injection only occurs after both intake and exhaust ports are covered by the piston, therefore, not allowing any raw air/ fuel mixture to escape out of the exhaust port as you would have in a carbureted 2 stroke.
Air-Assisted Direct Injection Combustion System www.ContactMagazine.com
While the origins of Orbital experimenting with fuels other than gasoline may have their roots in their R & D, it is not commonly known that their engines could also burn heavy fuels. In a conversation I had with an Orbital team member at an SAE convention in Cobo Hall, Detroit, in the mid 90’s, he noted that with Orbital’s AADI they could
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run heavy fuels but it needed a sparkplug to make it work. Some 10 years later, this ability allows them to create this unique engine; a spark ignited engine which runs on heavy fuel. However, there is a penalty for burning heavy fuel in these engines verses their gasoline brethren, that being a power reduction in the arena of 10% to 20%, depending on engine size.
So why did Hirth team up with Orbital? Orbital’s AADI system allows an engine to be calibrated to compensate for the poor burn qualities of heavy fuel. The fine atomization and full mapping of the engine calibration improves transient operation, fuel consumption and allows the engine to start at cold temperatures without additional heaters or additives. This provides a solution that is more fuel efficient than a turbine engine and lighter than a compression ignition diesel. Orbital’s AADI heavy fuel solution can be applied to two-stroke or four-stroke engines. Another key technology that the Hirth heavy fuel engines employs in these innovative engines is the use of carbon (graphite) pistons. These pistons have thermal expansion that is virtually nil, and allow piston-to-cylinder wall clearances of .0005 compared with a typical .005 for aluminum pistons. The composite unit utilizes two piston rings, with the design intent of being utilized for centering purposes only. While being shown this remarkable piece of engineering, Jason Wright of Recreational Power Engineering www.recpower.com, US distributor of Hirth engines as well as Powerfin props, demonstrated that by dragging the skirt of the piston across a piece of paper, it left a mark just like a pencil!
Carbon Piston as used in the Hirth 3053 HF, heavy fuel engine.
As previously mentioned, this is not Orbital’s first foray into the heavy fuel arena with one of its licensee’s. Mercury Marine has created a 185 h.p. heavy fuel variant of their Optimax® outboards for the U.S. Navy. The United Kingdoms E.P. Barrus Corp. has developed under license from the UK MoD a prototype 40 h.p. “Orbital Equipped” outboard. What is unique about the E.P. Barrus entry is that it can burn multiple fuels (gasoline, kerosene and diesel). This is currently handled via a selector switch, but, Orbital is looking at the feasibility of adding knock sensing and automated fuel sensing capability to be able to adjust the calibration for various blends of gasoline, kerosene, and diesel. Primary interest for this technology is on outboards and land-based vehicles, as well as APU applications. While the current 3053 HF and S1200 engines presently have representation in the form of brochures on the Hirth heavy fuel website, it may not be a true representation of the inroads Hirth has made in this arena in terms of the number of engines that have been or will be developed. In fact, do to the sensitive nature of the mission of these engines and, at the request of some of the customers, additional development programs may or may not be underway. At this point Hirth’s product array in this arena is fairly customized with each engine designed for a specific application. www.ContactMagazine.com
So, with all these advances Hirth has made with their heavy fuel engines for the UAV arena, when will these advances ever trickle down to the average homebuilder? Before we answer that question, here’s some background on Hirth’s current line of engines available to homebuilders. For years at air shows, aviation enthusiasts have approached Matt Dandar, also of Recreational Power Engineering, and have asked him when Hirth was going to introduce the four-stroke engine. Hirth took a different approach to this request, in many ways they have felt the two-stroke was superior and even though for years in terms of R & D, four- strokes have garnered the lions share of attention and dollars. Hirth decided to take a completely different approach, with their twostrokes inherent weight advantage; they asked themselves, why not strive to make our two-strokes with the fuel consumption and reliability of a four-stroke? It was with this mindset that Hirth embarked on their journey to do just that. As Hirth continues this journey here is a glimpse of how it may unfold in the near future. First, the carbon pistons are now a reality and in production, their cost will come down as production rates increase. As Matt noted, the price point will be in the arena of $400 per piston when offered as an option to the current line of Hirth engines available to homebuilders. To compliment the carbon pistons you could add as an option the currently available electronic fuel injection (EFI), which would bring a two-stroke offering to the table that would have an air/ fuel mixture continuously optimized, via the “black box”. With the EFI working in concert with the anti-seizure properties of the carbon pistons, for example, on Hirth’s current 3202 engine, you may have an engine with fuel consumption and reliability stat’s that may win over even
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the most fervent four-stroke enthusiast. With the combination of EFI and carbon pistons potentially being offered in concert to current line of Hirth experimental engines in the near future, Rec Power’s Matt Dandar notes there has been discussion of a new warranty policy to accompany these teamed options. Without stealing Matt’s thunder, keep an eye out for one-year full warranty with no hour limit and a three-year prorated warranty, with a TBO in the arena of 1,000 hrs when these features are purchased in concert. Due to the contractual nature of the development and specificity of each engine to its application, the marketing and reselling of existing Hirth heavy fuel AADI engines for homebuilders is not allowed. There are currently no plans to develop an Orbital AADI gasoline or heavy fuel engine for the manned aircraft market due to the high insurance cost and liability concerns with supplying fuel system hardware into this market. Orbital is focusing efforts with Hirth on unmanned applications only. But the story does not end here; in fact, other possibilities exist on the horizon for Hirth engines. For instance, charging in the form of turbocharging post the tuned exhaust is a possibility up to .7 bar, via research conducted at Wright Patterson AFB. When asked if a six cylinder could be developed from the existing flat four architecture, Matt noted current bearing journal diameters might not be suitable for that configuration. If a six cylinder were to be developed, the configuration of interest would be that of a V-6. Much like WWII accelerated the development of the piston engine, so today the war on terror and its utilization of UAV’s may be advancing the piston engine once again. In fact, one could argue as compared to other arena’s were engines are pushed to their limits, UAV’s may actually be the cutting edge. To many experimental, amateur-built aircraft enthusiast, to have one of our own in this arena, and making great strides, is a source of pride. Perhaps soon the advances being made in this realm will start filtering their way back to the civilian side of the ledger so that experimenters can take advantage of these technological advances as well. The author would like to thank Matt Dandar and Jason Wright of Recreational Power Engineering for their time and hospitality extended during our visit to Rec Power at their facility in Tiffin, Ohio. I would also like to thank Orbital’s U.S. Representative Bob Schmidt and Hirth of Germany’s Siegfried Gobler for their technical review of this article, and many thanks to Bob Skingley for his assistance during the photo session of the engines. All pictures, unless otherwise noted, are by Anthony Liberatore and Bob Skingley. For further information, consider the following: Factory Authorized U.S. Distributor for Hirth Aircraft Engines: http://www.recpower.com . Hirth UAV Engines: http://www.hirth-uavengines.de . More info on Orbital: http://www.orbitalcorp.com.au . www.ContactMagazine.com
The Hirth 3503 HF (Heavy Fuel) AADI 62 HP engine with attached 2 KW generator on the left side of the engine in this photo. Also, note some perspective of the engines size relative to the tape measure. From the brochure: The 3503 heavy fuel is an water cooled, reed valve controlled two cylinder, inline, two-stroke engine with electronic direct injection fuel system and Nikasil coated cylinders. It has one of the highest power to weight ratio available on the 60 HP engine market. Ideally all types of propeller applications with direct drive or gear reduction and all applications here the power to weight ratio is an issue. Factory recommended TBO is rated at 1000 hours at 75 % power. The warranty of the crankshaft is 3 years.
Technical data: Type Displacement Stroke Bore
Two cylinder, two-stroke 625 cm3 (38,1 cu in) 69 mm (2,72 in) 76 mm (2.99 in)
Maximum Performance
45 kW (62 HP) at 6500 rpm Specification with 194°F coolant
Max. Torque
67,5 Nm (50,0 ft-lb) at 6000 rpm
Mixture Formation Ignition Generator Cooling Lubrication Weight Start device Direction Fuel
Air-Assisted Direct Injection (Orbital) CDI programmable 250W, 20 amp, 12 Volts Liquid cooling . Oil injection 30 kg (66,0 lb) with exhaust and coolant Recoil starter Counter-clockwise, view to output shaft 5 (F 44) / JP 8 (Jet A / F 30)
Orbital’s United States Representative Bob Schmidt: bschmidt@orbitalcorp.com.au .
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By Anthony J. Liberatore aliberatore@comcast.net I cannot help but wonder if it is déjà vu all over again. It wasn’t that long ago many of us were stunned to see on the cover of “Air Progress” a small bird known as the VariEze. Its construction technique, use of the latest aerodynamics such as the GAW airfoil, winglets and the canard configuration, stunned us all and made many dreamers want one badly. And get one they did. Many were built as well as its follow-on sister, the Long-EZ. However, in a hangar in balmy Melbourne, Florida there is an aircraft that I cannot help wondering, may end up repeating the same phenomenon. This aircraft’s name is Atlantica. For those of you not familiar with the project Atlantica, it’s a four-place blended-wingbody aircraft, of all-composite construction, the brainchild of Alan Shaw. Alan’s background may not be familiar to many of you, but he is one of the original team members with the Velocity Aircraft. Since leaving the Velocity program, Alan has developed a proprietary composite technique that Atlantica utilizes in its construction. At an air show, Alan was discussing the technique with an individual who mentioned that the technique might lend itself well to some advanced work being done, which could not be discussed; however, he did mention the Blended Wing Body (BWB) configuration. While testing iterations of design concepts within aero software programs, Alan tested the BWB configuration and was stunned by the efficiency gains over all other configurations. It was then that he decided to proceed with his own BWB design. The blended wing body is the brainchild of McDonnellDouglas (before it was bought by Boeing), but its origins can be traced back many years to the work done by the Horten Brothers in Germany. It should be noted that almost all major airframe manufacturers, and universities are currently investigating, or have investigated, the configuration at one time or another. It is an attempt to eliminate fuselage drag, increase L/D, create a large capacity airliner that would take the footprint off the current “Heavies”, and distribute the load of the passengers www.ContactMagazine.com
more evenly along the span to make it a more efficient “Span-Loader”. The selling point of this configuration that has everyone’s attention is that the drag is projected to be in the area of 32% less. With that in mind the fuel savings could be dramatic. Although no full-scale blended wing body airliner currently exists, universities such as Stanford have flown some large-scale models. Atlantica is the only general aviation aircraft of this configuration at this time. The current prototype is a four-seater powered by a 235 hp LOM inverted inline 6. In the design process Alan utilized a great deal of aerosoftware to help develop the Atlantica. For instance, not satisfied with available airfoils, Alan designed a series of laminar flow, low pitching moment airfoils for this application, with sections along the span tailored to the given Reynolds numbers at a given station. While Atlantica utilizes a “bell-curve” span loading as found in the Horten brothers’ designs, one of Alan’s team members came up with the concept of using a less cambered, almost inverted airfoil out near the tip to take the place of the large washout typically utilized in tailless, swept-wing designs. It is surmised that this will also reduce wingtip vortices for even greater efficiency. Another unique feature is that the center section has some reflex to help maintain a positive angle of attack at cruise. Alan attributes this to a successful vehicle, utilizing a form of trim or “toe-in” to help the vehicle track in a straight fashion. To truly understand some of the features of the configuration, read what Alan has to say: “The swept back wing tips always pull down. This is the key to the “bell curve” span loading and how Blended Wing and Body (BWB’s) aircraft work. The “see saw” is balanced the same as conventional aircraft which require the addition of an aft wing (and drag) to pull the tail down. Understanding what happens when the pressures
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are reversed at the wing tip is the heart of this debate. As the elevons are deflected upward the angle of attack increases across the whole span, reducing the downward force at the aft wing tips, causing the nose to return to alpha zero when the stick is released. This is proof of pitch stability. Those who persist in rigging swept winged and all winged aircraft with “Elliptical Span” loading, which produces lift all the way to the wing tip, will realize instability in all three axes. The dihedral effect of a swept wing produces excessive roll stability at high alpha. Roll stability produces yaw stability. Good swept wing designs have anhedral to destabilize somewhat such that ample roll and yaw agility is regained for cross wind landings. Anhedral also has the benefit of more efficiency at cruise speed. The “Bell Curve” does several things for swept, all-winged aircraft. By reversing the pressure differential at the wingtips, vortex drag and spanwise flow are minimized. The lift and drag coefficients are much higher in the center of the aircraft than an elliptically loaded planform so a fuselage with wing intersections (a tube with wings) would result in little lift and high drag in this area. BWB’s take advantage of the bell curve, high mid-wing loading, with an airfoil center section and a blended, no-intersection transition to the outer wing panels.” After the prototype was finished, one unique step in the testing program was to mount Atlantica on a trailer and tow the entire assembly behind a pickup truck on aircraft runways and taxiways. On the Atlantica website, www.wingco.com, you can view movies of the tests (in Atlantica’s original configuration), including the high alpha test. In January, 2003, during the flight test program with Alan as PIC of Atlantica, an incident occurred that has delayed the program’s progress. During a highspeed taxi test, an inadvertent take-off occurred. Over controlling by Alan created a pitch up / pitch down scenario that resulted in a very hard landing that damaged
The air-cooled, supercharged, 235 HP Walter-LOM inverted inline 6 cylinder engine. the Atlantica prototype. Nevertheless, even with this setbacks, all is not lost. In fact, while “flying” Atlantica within aero-simulation software, Alan has been able to replicate his incident many times and he is thoroughly convinced it was his piloting technique that led to the eventual outcome - not the stability or control of Atlantica. From this incident, a problem of trailing edge boundary layer flow separation came to light. The solution chosen is unique and involves moving the long-span narrow chord elevons off the wing and mounting a shorter narrow chord elevon aft and slightly above the wing, à la Junkers. Alan surmises that this elevon location may also act as “feathers” to dissipate the vortices much like an eagle or pelican will splay their feathers at the tips to reduce vortices. Another contributor to the overall configuration efficiency is the “C-Wings”. If you look at the latest configuration photo, the C-Wings are the horizontal aft sweeping surfaces atop the winglets.
Atlantica prototype undergoing trailer preparation (original configuration). www.ContactMagazine.com
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The C-Wing is the brainchild of Dr. Ilan Kroo and his students at Stanford University. Some of you may not recognize the name, but Dr. Kroo is the father of the Swift the high performance, foot-launched glider. The C-wings came about as Dr. Kroo challenged his aero students to design a wing with greater efficiency than a given start point, which was a Long-Eze wing. Through computer design iterations, the C-Wing was born, and what they do is quite amazing; your current wing with slight dihedral has a span efficiency of 1.03. C-Wings increases the span efficiency to 1.45. One of the original concept applications of the C-Wing was to apply them to an existing airliner configuration on top of large winglets to eliminate the entire tailplane. While this configuration has not gone any farther than artist’s conception, C-Wings have been applied to a few R/C aircraft and to Team Atlantica’s 1/7th electric model of the Atlantica, and the static model pictured above. Alan notes in the Atlantica e-mail list that the addition of the C-Wing to 1/7th scale model had a dramatically positive effect on the landing characteristics and that it will now spoil you in how well it lands. When Altantica’s C-Wing configuration is added to the Atlantica prototype, not only will it be the first mancarrying craft with C-Wings, but its C-Wings will also utilize trim tabs to assist in the landing configuration (another first). So where is the program at this time and where is it heading? After the taxi (inadvertent flight), the program has come under some financial strain. Current goals are to proceed with a 1/6th scale model, a 1/3rd scale model, as well as to resume work on the full sized prototype as soon as feasible. A few Atlantica enthusiasts have pledged funds to assist Team Atlantica to get the plane flying. While much headway has been made in reaching the funding goal, it has not yet been achieved. The prototype will be repaired and the new wings, with the new elevon and CWings configurations, installed. The landing gear will be relocated forward since its original aft mounted location was a contributing factor to the original incident. A flight test program and a test pilot will be utilized to keep a fresh perspective on flying the aircraft vs. having the designer fly it (which makes a lot of sense).
configuration, and less cambered inverted airfoil section(s) at the tip. The combination of all these aerodynamic features may well in fact lower the drag and increase the fuel economy of Atlantica to springboard it light years ahead of even the slickest homebuilt. In light of current and potential future fuel prices and the cost associated with burning these fuels, it has definitely shown up on many a pilot’s radar screen. At some point we may all be looking for alternatives to high GPH fuel consumption figures. This configuration may be a “disruptive technology” to general aviation since it will be hard to say no to the potential fuel savings this configuration may offer. If this is not enough of a change, consider a slightly larger wing span cousin powered by a small turbofan such as the Williams FJ-33. The calculated performance of such an aircraft, as noted on Wingco’s website, is eye catching to say the least. With the “very light jet market” just on the horizon, perhaps a turbofan Atlantica will be a player in this arena. America has always been a country of visionaries that have been willing to take risks, dream big, and reach for their goals. Success or failure, men like Burt Rutan and Sam Williams have followed their passions and have laid it on the line. In the process they have not only changed the way we fly, but in many cases the way we live. In many ways the contributions of such innovators are inspirations for others to dream and reach for the stars. It is truly a testament to these individuals as well as to the American entrepreneurial spirit. In an Oshkosh forum, I once heard one of the Rutan brothers say that if we were not willing to take risks we still would be looking at the backside of an ox. With a little luck and help from visionaries such as Alan Shaw and Company, we will be looking at oxen from “Flight Levels” as small dots as we pass them at an amazing speed. Anthony J. Liberatore aliberatore@comcast.net
The Atlantica prototype will fly at some point, and its performance may well surprise the critics. What is being attempted here are a number of firsts, including: proprietary construction technique, the first general aviation BWB, custom airfoils, C-Wing utilization, unique elevon Alan Shaw, ready for taxi testing before the unfortunate incident. www.ContactMagazine.com
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