WASHINGTON -- Start-up company AVX Aircraft is proposing to upgrade the Bell OH-58D Kiowa Warrior with coaxial rotors and ducted fans to meet the U.S. Army's Armed Aerial Scout (AAS) requirement.

Hoping to persuade the Army to fund a demonstrator, the company is making its debut and unveiling its concept at this week's Army Aviation Association of America convention in its hometown of Fort Worth, Texas.

Founded in 2005, AVX is made up mainly of former Bell Helicopter engineers and managers. President and chief engineer Troy Gaffey was previously chief engineer and senior vice president research and engineering at Bell, owned by Textron. AVX's proposal is to remove the OH-58D's four-blade rotor, transmission, tailboom and tail rotor and install two three-blade coaxial main rotors, new transmission and a shorter tailboom mounting a pair of ducted fans.

Compared with a single main rotor, coaxial rotors require 5% less power for the same diameter and helicopter weight, says Gaffey. Additionally, there is no need to counter torque with a tailrotor, which consumes at least 10% of available power, he says.

"That means net savings in power required of 15-20% versus a single rotor," Gaffey says. This would increase hot-and-high performance with the OH-58D's existing engine, which would be retained under AVX's plans.

Mechanically driven from the main transmission, the variable-pitch ducted fans would provide directional control in hover and thrust in forward flight.

With the fans idling in a hover, moving the rudder pedal would change blade pitch to produce forward thrust on one side and reverse on the other. "In an OH-58D hovering at heavy weight, the main rotor would take 500 shp and the fans 20 shp," he says.

In forward flight, instead of tilting the rotor and fuselage nose-down to increase thrust, fan pitch would be increased using a twistgrip on the collective lever. The fuselage would remain level, or slightly nose up, for improved cruise efficiency, Gaffey says.

"Power to the main rotor would be reduced to around 200 shp., with 300 shp. going to the fans. The main rotor would be sort of idling in the cruise," he says.

Performance estimates for the modified OH-58D include the ability to hover out of ground effect at 5,500 lb. -- with full fuel and weapons - in 6,000 ft./95 F hot-and-high conditions; as well as a 120-kt. cruise, 240-nm. range and 3.1-hr. endurance.

Gaffey says the OH-58D AVX meets the requirements outlined in the Army's AAS request for information, to which the company submitted its response on March 18.

Supported by private investors, AVX has spent around $4 million on design work and is looking for funds to build and fly a proof-of-concept aircraft within 18 months. A "bare bones" demonstrator, possibly based on a commercial Bell 206, would cost around $30 million, he says.

"We are still working to raise money, but we would really like to get the Army involved," he says. AVX has no plans to be a manufacturer, Gaffey says, and instead intends to "find world-class low-cost producers" to make the OH-58D modification kits.

Click here to read an Ares blog post about the AVX proposal.

Click here to see three photos of the AVX proposal.

Photo: AVX Aircraft