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Sat, Apr 17, 2004

Cessna 340 + 1 List of Extensive Mods = Innova 341… Homebuilt?

Result Is A Very Familiar-Looking Single-Engine Six Seat Cabin Class Turboprop

By ANN Correspondent Juan Jimenez

As you enter S-N-F 2004 through the main gate and walk past the forum tents in the direction of the flight line, you are comforted by the thought that everything seems to be where it belongs, in the same places as last year. And so it is, until you saunter over the little footbridge and into the first exhibits, turn right and run into… umm…

Well, the only way to describe it is that it looks extremely familiar, but you just can't place it… and even more so when you look at the sign and notice the words "…And it's a Homebuilt!" The reactions are strangely homogenous. First the eyes glaze over and a blank stare attaches itself to your face. The words "What the…" followed by an assortment of expletives, some printable, some not.

It looks like a Cessna light twin, but there's no getting away from the fact that it doesn't have two engines - it has only one, and it's clearly a Walter turboprop with a five-bladed Avia prop sticking out of what used to be the nose. And get this… the designer/manufacturer claims that it can handle six adults, 400 lbs. of baggage, full fuel and deliver all of it 1,200 nautical miles away… with IFR reserves and in pressurized comfort and heated de-iced safety! Talk about a true aviation SUV…

Top it off with the fact that the prototype flew into S-N-F and was granted an airworthiness certificate as an Experimental, Amateur-Built aircraft, and clearly this event is grounds for a good story, wouldn't you agree?

The one thing that gives away the true nature of the airplane is its tail number - N341TP. Subtract one from the number and you come up with the answer. The Innova 341 actually started life as a Cessna 340 airframe. The company behind the aircraft is the same company that bought the JetCruzer project assets from the folks who bought Mooney Aircraft Co., and turned it into a kit aircraft offering. We interviewed owner Michael Spearman to get you the details of this wild project.

Starting with a C340 airframe, the nose, cowlings, engines and engine mounts were removed, along with other associated hardware. The wing structure was modified in order to shore up and strengthen the area where the engine installation provided strength to the wings. The root airfoil was then extended to the leading edges to end up with a conventional single-engine style wing.

The complete nose assembly was removed and an engine mount had to be designed and installed to house the Walter turboprop engine. Because the remaining bulkhead was not designed to handle the stresses of an engine hanging in front of it, the structure there also had to be strengthened. This process also required the design and installation of a modified fuel system so that the engine could pull fuel simultaneously from either one or both tanks. Auxiliary fuel systems and tanks were also designed and installed. A custom nosegear was installed, as well as all the composite structures and inlet system.

The experience required to do all of this comes from the fact that the same company is designing and installing a Walter conversion for Piper Malibu aircraft, and much of what is learned from the Malibu project is being applied to this new proof of concept project that they call the Innova 341. The pressurization system comes from the Beech Duke but also uses parts from the Malibu project, such as the heat exchangers.

In the airframe department, the designers took a hint from the Piper Meridian and the horizontal stabilizers were widened an additional six inches on each side at the tips to give it more stability and control. It surprised us a bit to know that the rudder has not been modified - it appears that the stock C340 rudder has sufficient authority to counteract the torque of the big Walter engine.

Flight performance numbers as reported by the test pilot and estimated by the company are very promising. Of course, there is no longer a Vmc issue, since there are no longer two engines on each side of the fuselage. The stall speeds of the aircraft have been lowered due to the extra wing area, and have hovered at 58 or 59 knots, but testing at full gross of 6,300 lbs. has not yet been performed. In addition, vortex generators will be installed on the wings to further reduce the stall speed. Cruise speeds at altitude (23,000 feet) are estimated to register in the 230 to 235 knot range.

As far as kits are concerned, the project has not progressed to the point where decisions have been made as to how the materials will be sourced for the kit. Conceivably, the company could provide all the components for the aircraft in the same way as a traditional homebuilt aircraft company sells and delivers kits. Alternatively, the prospective owner may decide to source his own airframe, wings and other components and purchase only those additional parts needed to complete the project. A third option certainly comes to mind - that of producing molds from the C340 airframe and wing components and replacing them with custom-made composite parts and structures.

When the aircraft's airworthiness certificate was issued, the FAA calculated that the builder had done over 60% of the construction work to produce the aircraft and issued an Amateur-Built certificate. It will be interesting to see how this will translate into customer projects and how the kit provisioning will be structured to accomplish the same goal.

Interest in the prototype airframe from Sun-N-Fun patrons has been fairly high, and some have even asked if they could purchase the prototype on the spot! The company estimates that the finished price of the aircraft will be in the $400,000 range, including an all-glass cockpit.

This falls right in the middle of the sweet spot that the Lancair IVP has virtually owned for quite some time now. The performance of the Innova 341 may not be expected to compete with that of the Lancair IVP. However, the ability to deliver 2,800 lbs. of useful load a distance of 1,200 nautical miles at FL230 with the benefits of an amateur-built certificate should attract a lot of attention from customers.

In fact, the Innova 341 may take on some much higher priced competitors such as the TBM 700, the Piper Meridian and turbine Malibu conversions, and perhaps even slightly larger aircraft like the Pilatus PC-12. The company also expects that insurance will cost less than what it normally costs for an equivalent (or pre-Innova) twin engine piston aircraft, mostly because of the turbine engine but also because it is based on a proven airframe and wings. Transition from a 182 or 210 to the Innova 341 is expected to be fairly simple due to the lack of complexity in the aircraft's systems.

FMI: Stay tuned to Aero-News Network…


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