The 2012 EAA AirVenture airshow in Oshkosh, WI showcased a range of innovations within the aviation industry. One in particular, came from Auckland, New Zealand-based Composite Helicopters International, who introduced the world’s first all-composite Carbon/Kevlar, frameless helicopter fuselage, the KC518 Adventourer.
With 18 years of CAA- (Civil Aviation Authority) approved manufacturing of composite parts and materials, Peter Maloney, president of Composite Helicopters, started to design the KC518 eight-and-a-half years ago to provide the lowest cost of ownership of any turbine engine helicopter.
“KC518 has been designed and manufactured with full FAA certification in mind, so by offering her as a kit helicopter to the public pre-certification, [customers] are effectively getting a world-class helicopter at kit prices,” says Maloney.
Great White Inspiration
Composite Helicopters drew inspiration from the great white shark when considering the design of the KC518, because aerodynamics is very similar to fluid dynamics. “The great white shark has a perfect profile and the most efficient fluid-dynamic shape that has been unchanged for millions of years,” says Maloney. Utilizing state of the art CAD systems and modern hybrid compound materials, Composite Helicopters achieved a smooth aerodynamic fuselage shape.
The cabin was designed around Maloney’s height and weight (6’, 240 lbs.) creating a spacious cabin with excellent visibility through a sleek center section. Large storage areas are incorporated into a streamlined empennage (tail), terminating in a powerful ducted fan tail rotor.
“The shape of the shark’s dorsal fins dictated the shape of the undercarriage of the KC518,” explains Maloney. “The position of the main rotor gearbox and main rotor mast represents the ventral fin of the shark, and the position of the KC518’s tail rotor is set at the same scaling of the great white’s tail fin.”
The snout of the shark was tucked in to provide a smooth transition around a generous instrument panel, providing ample leg room for the pilot and front passengers.
Future Proof Design Philosophy
The design philosophy of the KC518 is one of safety, reliability, strength, and rigidity. Constructed primarily out of carbon fiber and Kevlar, Composite Helicopters were able to achieve a strong, lightweight, and corrosion-proof frameless design that can be assembled from the outside in with pre-determined order. All bulk heads, keel beams, floor panels, and the sub-assembly parts are inserted into the fuselage shell through the cabin doors.
“The shell of the KC518 is ‘monocoque’.” says Maloney. “There is no frame around which the helicopter is built, creating a simple and easy way to build a helicopter.” Maloney also explains how the primary parts of the kit are manufactured using intrusion, prepreg, and RTM processes.
Fuel & Engine
Composite Helicopters separated the fuel load into three tanks, allowing for customer options and a future proof design. With standard tanks the KC518 has a maximum of three-and-a-half hours of endurance, which can be extended to 6.2 hours with the installation of an auxiliary tank in the additional storage space between the bottom of the main rotor gearbox and the top of the fuel tanks.
The KC518 can be fitted with the RR250T63-700 and 720 series engine, which is available to the amateur build market at an affordable price. It is the most prolific with both ex-military and civilian engines available, and helps the KC518 reach a cruise speed of 135 kts. “We used a Zero Hr TSO T63-700 (320 shp) engine in our prototype, which has demonstrated lift of 16.2 lbs/shp,” says Maloney. “The drive train and airframe is designed for 450 shp so the engine can be replaced with a more powerful engine of the RR250 series at any time.”
Ducted Fan for Quiet Operation
Aside from its sleek and aerodynamic design, Composite Helicopters wanted to make the KC518 neighborhood friendly, so they looked into ways on how to make it quiet. They decided to include a four blade ducted fan tail rotor, which can be 30 percent more efficient than conventional tail rotors of a similar size. The ducted fan is constructed of carbon fiber using a 63-615 1.2-inch cord airfoils, with a tip speed of 501 fps. “Our ducted fan four blade rotor runs at 3,008 rpm, and has produced 96 kts of thrust at 17 degrees of pitch,” says Maloney.
“The four blade main rotor at 380 rpm has demonstrated lifting of 16.2 lbs/shp (3,000 lbs at 185 shp with prototype airfoil 8H12 8 inch cord).” To optimize performance now rather than in the future, Composite Helicopters’ new carbon fiber main rotor blades are a VR-7b airfoil with a 9½-inch cord and swept tips. Tip speed is 564 fps making it a quiet helicopter.
Future of Helicopter Design
Traditional ways of manufacturing helicopters requires hundreds of man hours and a large team of engineers. Composite Helicopters’ KC518 fuselage can be built in five days with two engineers, which creates huge economic benefits for the manufacturer. The estimated kit-build costs for the KC518 is around $395,000 with factory training courses available to the owners.
“I believe, as more and more people start to understand composite technology, carbon fiber, and the benefits and strengths they have to offer, then the interest in this type of helicopter will continue to grow,” says Maloney. “I also think that we will see a completely different approach in how helicopters are manufactured in the future, because of this aircraft.”