Carbon prepreg and carbon sandwich structures (carbon fiber reinforced polymer with foam core) are used in all the weight-bearing primary structures, including the fuselage, wings and horizontal stabilizer, as well as other parts. To ensure all the composite parts perform well in water environments, LISA uses a special pre-impregnated resin made by Umeco’s Advance Composites Group (ACG), a layer of Kevlar to protect the area under the fuselage during water impact and external fiberglass layers to set the seal for optimal waterproofing. A glass composite material, produced with high glass transition temperature (Tg) and epoxy resin, is used to finish parts inside the cockpit.
“We chose these materials because they are lightweight — a constraint we have in light aviation — but mainly because we needed to design and produce extremely high-performance aeronautical shapes,”prepreg said Erick Herzberger, founder and CEO of LISA Airplanes. What’s more, thanks to LISA’s patented multi-access technology, the uniquely designed AKOYA can just as easily take off and land on water or snow as on a strip of land less than 220 yards long with no prior modification required. “The AKOYA is the first seaplane equipped with Seafoils that maintain good aeronautics in flight,” he says. The plane also has skis on the retractable landing gear.
The biggest problem the high-tech company based in LeBourget du Lac, France, had to overcome in designing the first airplane with hydrofoils was not to make the aircraft lighter, stronger or more stable, as one might expect. Herzberger said, “Our main challenge in designing the AKOYA was to place the engine at the back of the airplane on top of the vertical stabilizer.” The solution, once again, arose from using composite materials. “We had to place the engine where it would not interfere with water operations,carbon sheets” Herzberger says. “After several round of calculations, simulations, characterization of the materials and tests on samples and representative parts, the conclusion was that carbon composite (CFRP) was the best material to solve this structural design issue because it ensures the engine mount is strong enough to hold the weight. CFRP offers the best compromise between resistance and weight. This was the material to use to support the weight and stresses of the engine, the wings and the hydrofoils.”
The folding wing system with one rotation axis was another critical point where optimized composite materials and finishes made the final design possible. “The part that enables the rotation is fixed on composite structures that are glued on the fuselage,” the engineer says. “A specific distribution of the fibers of the fuselage enabled us to better distribute the stresses of the rotating part.”
All major components of the AKOYA are produced by aeronautical manufacturers in France, Italy, Germany and Austria. All the finishing for coverings is done by hand, making each AKOYA a customized aircraft.
In Herzberger’s opinion, there’s still work to be done by the composites industry to improve materials and prepreg resins. For future aircraft designs he dreams of,carbon cloth he says he’d like to see more solutions for the interfaces between composite and metallic parts. Innovations that would enable future generations of lightweight, high-performance planes could come from either side of the Atlantic, as he believes that the composite market in the U.S. and in Europe are comparable.
“Our customers are private individuals who wish to make inconceivable trips to places that are hard to reach,” said Herzberger, a top level gliding competitor who has flown since he was 16 years old and logged more than 1,500 hours of flight time. “They enjoy the performance, the style and the design of the AKOYA.” Thanks to its folding wings, owners can park the skiplane inside their garage. cc compositeBut that is not what this amphibious aircraft is designed for. ”With such a versatile aircraft, you can go fishing in Alaska’s most remote places. People can take off from the airfield close to their home in, let’s say, Georgia and land on the private beach of their waterfront villa in the Bahamas, and then travel back to Georgia in about 3–4 hours versus 13 hours with a commercial airline and multimodal transportation means,” he says.
Produced in a limited series, the AKOYA will be available in the U.S. next year. The AKOYA reaches speeds of 155 mph and can travel a minimum of 1,000 miles before refueling. The amphibious aircraft fulfills the S-LSA regulation (CS-LSA in Europe). At a price of $400,000, the AKOYA multi-access plane comes fully equipped, including maintenance and customized training in Chambery-Savoie, France, to obtain the license and to pilot AKOYA on water and snow.
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