We are now in the earliest stages of building a "proof-of-concept" airplane known, if you can believe it, as the RV-12. It bears a strong resemblance to Van’s model. It’s an all metal side-by-side airplane with a low wing. Cabin room will be comparable to the RV-7/9. It uses a tricycle landing gear and has a 100 hp Rotax 912S for power. Fuel is stored in a fuselage tank aft of the occupants. Our construction thoughts at the moment center around pulled rivets rather than driven rivets.

We are trying to achieve a 550 lb payload – this equates to two 190 lb people, 120 lbs of fuel and 50 lbs of baggage. If you subtract this payload from the maximum 1320 lb gross weight dictated by Light Sport regulations, you can see that the empty weight of the airplane must be around 750 lbs to allow for the inevitable creep or miscalculation.

Naturally, we want an airplane that continues our tradition of "Total Performance" by possessing good handling qualities and good value. Actual performance is more or less defined by the rules of the Light Sport Category:

• Maximum takeoff weight: 1,320 lbs (599 kg.)
• Maximum stall speed (clean, unflapped): 51 mph (45 knots)
• Maximum speed in level flight with maximum continuous power:
  138 mph (120 knots)
• Two-place maximum (pilot and one passenger)
• Single, non-turbine engine
• Fixed or ground adjustable propeller
• Fixed landing gear

As this is written, a basic design study is under way and a wooden cabin mockup is under construction. We will proceed with the usual back-and-forth between the design staff and the prototype shop and eventually (no, we don’t know when) build a flying "proof-of-concept" airplane. Which will be exactly that – an airplane to test our ideas and see if they do what we hope and expect. It is a working tool, not a finished product.

Depending on what we learn from this airplane, we may decide to proceed with a kit airplane. The most probable first step would be a kit similar to our current "49%" kits. Finished airplanes would be registered in the current Experimental category. (If the airplane meets the performance standards for an LSA airplane, it can be flown by anyone holding a Light Sport pilot’s license, no matter what category it is registered in.)

After that, we may consider a Special LSA kit. This category allows kits to be completed to far more than 49%, which sounds attractive. But the flip side is that no modifications or variations from the plans are permitted. Every example must be built to the manufacturer’s compliance standard.

The possibility of a fly-away airplane (permitted by the standards of the category) is so remote that we can’t even discuss it at this time.

We live in an internet age, which means we have almost instant access to information. Some of it is even true. We’ve already seen some wildly inaccurate speculation about our next project and we’d like to head it off before it takes permanent root somewhere out there in cyberspace. We will keep you informed through the RVator and our website about the progress of the RV-12, and we’d welcome your written or emailed thoughts on the concept. We can’t answer questions about the RV-12, either on the phone or in any written format. Not only would that take time (something we barely have enough of in a normal workday) but, at this point, we don’t have the solid answers customers have a right to expect.

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Our first choice for a propeller is a hollow-blade composite unit from Sensenich.

By August, we’d built the wings and are working on the tail and fuselage. We’ve acquired a Rotax engine and have experimented with several different firewall and engine mount ideas. We’ve built a wood cabin mock-up and changed it quite a few times as shortcomings revealed themselves. The basic design for this one-off airplane is wending it’s way through the computer. We have no fixed schedule for completion or flight.

WHAT WE’RE AFTER

In the second issue of 05 we stated our design goals. On the flying side we wanted:

• Flying qualities equal or better than the RV-9A (not easy!)
• A 550 lb. payload – this equates to two 190 lb. people, 120 lbs. of fuel and 50 lbs. of baggage.
• 750 empty weight

From the construction point of view, we are aiming for:

• A low parts count, to reduce kit costs and assembly time
• Systems installation at the lowest possible level of structural subassembly
• Minimal use of composites
• Maximum use of simple hand tools, possibly eliminating the need for pneumatic tools (maybe not the desire for, but the need!)

Actual performance is more or less defined by the rules of the Light Sport Category:

• Maximum gross takeoff weight: 1,320 lbs (599 kg.)
• Maximum stall speed (clean, unflapped): 51 mph (45 knots)
• Maximum speed in level flight with maximum continuous power: 138 mph (120 knots)
• Two-place maximum (pilot and one passenger)
• Single, non-turbine engine
• Fixed or ground adjustable propeller
• Fixed landing gear

You can easily see that we are trying several new – or at least, new to us – ideas. Chief Engineer Ken Krueger freely admits that these are experiments. If we don’t try new things, we’ll never get any better.

The most obvious is easily removable wings. This is achieved with a "glider-style" technique. The two spar stubs projecting from the inboard ends of the wings overlap inside the fuselage and are secured with two large pins, fitting into carefully machined bushings. Full span flaperons will hook up automatically as the wings are installed – again, using fittings similar to those proven over many years in sailplanes. The fuel will be contained in a fuselage tank aft of the spar carry-through. Removable wings pretty well rule out wing tanks. With the wings removed our design criteria specifies that the aircraft will not exceed 8’ in width, making it trailerable in every place we’ve checked. Driven by this, we’ve chosen an all-moving stabilator because it can be smaller than a conventional stablizer/elevator arrangement and still provide the requisite pitch authority.

The last RVator article and website update generated more discussion of the RV-12 on the web and sure enough, several people chimed in, wondering about alternative engines. Why not a BMW engine, a Suzuki engine, an older Subaru engine? Amusing. We finally choose an engine other than a Lycoming or a Continental and immediately people start speculating about using something else.

So why did we choose the Rotax? Because it is the best understood, most readily available and best-backed engine from an established manufacturer that fit our requirements of power, reliability and weight. As an added bonus Rotax has also qualified the 912 under the ASTM standards that apply to the LSA category. That’s pontentially important because although an RV-12 licensed in the current Experimental Amateur-Built Category, the builder can install any engine he chooses. But if the airplane is licensed as a Light-Sport Aircraft, then the rules are more similar to type-certificated aircraft. No variations are acceptable. 
Our point is this: there’s no point asking us why not this engine, how about that engine? We had to choose an engine. We chose the one we felt best suited our needs. Hey, it’s tough enough developing an all-new airplane when the engine is defined. We can’t even attempt to design one that will accept an infinite array of engines.

Left:The Rotex 912.
Shown here on a preliminary mockup of an RV-12 firewall.

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From the RVator.  Sixth Issue, 2005  

Why trailer-able homebuilt aircraft have not become more popular and widely used is debatable. Perhaps in some instances it is because of the mechanical difficulty of doing so. In some instances, where the trailerable homebuilt in question becomes an expensive, finely finished product, the owner may find that the relative burden of hangar rent is less objectionable than the disassembly effort, trailering effort, and damage risk.

In assessing the potential use of LSA class airplanes, we see a couple of the primary uses. These include the reduced cost training of new pilots, and as a "retirement" airplane for pilots entering the "casual flying" phase of their flying life, quite possibly driven by medical considerations. It is for the purpose of reducing overall ownership cost of the LSA aircraft, and to some recreational use considerations that we chose to experiment with the removable wing/ trailerable feature of the POC RV-12. The economic benefit vs. inconvenience question is one which will vary greatly with circumstance. If hangar rent is $75 per month, the extra cost of these design features, plus the effort of disassembling and trailering, is arguably not worth it. If hangar rent is over $200/mo, disassembling , trailering and home storage become a more appealing option. If the average monthly utilization is 4 flights, then the user saves $50 per flight. In some climatic areas, such as here in the Pacific Northwest, tying down outside is acceptable because the chance of damage from hail, wind, or blazing sun is minimal. In other areas, potential hail damage essentially precludes outside storage. The hangaring/trailering/tie down considerations are infinite and vary greatly with locale.

While it may not constitute a dominant usage, we see trailerability as a potential benefit to the recreational pilot. For instance, we imagine that many retired pilots might want to drag their Light Sport Airplane along behind the camper or motor home for the extended vacations and/or when relocating to the summer/winter home. An owner may choose to use an inexpensive tie-down for 7 months of the year, and then bring the plane home for the rainy season when he may only want to fly once per month anyway. The bottom line is that this feature would permit exercising many options, and may be worth the added cost and/or building effort.

CABIN FORWARD FEATURE

Traditional 2-seat lightplanes have always been plagued with the problems of co-locating the cabin and the wing. This is particularly true of lightplanes using cantilever wings where it is necessary to for the wing spar, or spar center section, to cross through the cabin area. The co-location need is driven by the relative weights of the engine, cabin occupants, and airframe components. For a higher performance 2-place, the relatively heavy engine is balanced by locating the cabin occupants somewhat aft of the wing spar that is commonly located in the 25-30% wing chord range. With a lighter engine, the occupants must be closer to the center of lift, essentially seating them atop the spar. This generally will result in a deeper fuselage, thinner seat cushions, and other packaging constraints.

As an aside, one appealing feature of pusher engine lightplanes is that the cabin can be located forward of the wing, where it is unencumbered by wing spar space considerations and offers a superb forward field of view. However, there are many serious structural and aerodynamic drawbacks to pusher prop designs, which effectively ruled out any further consideration for us.