The news that UAV maker AAI has exclusively licensed Carter Aviation Technologies' slowed rotor/compound (SR/C) design for unmanned aircraft applications came as a surprise to me. I've watched Carter over the years as it has struggled to perfect its high-speed autogyro concept and always thought it would go the way of other small aircraft firms with ideas that looked good on paper.


Concept: AAI

But the licensing deal with a household name in the UAV business comes as quite an endorsement. AAI says it has been working with Carter for over a year, providing it with analytical tools and engineering resources, and is confident the SR/C concept works. Now AAI plans to take the four-place personal air vehicle (PAV) prototype taking shape at Carter and turn it into an unmanned cargo aircraft.

The PAV prototype is expected to fly in the first quarter of 2010 and, while Carter plans to sell the aircraft as a kitplane on the civil market, AAI says it will take the design and turn it into a 7,250lb gross-weight turbine-powered UAV able to carry 3,000lb of cargo over 1,300nm at 250kt. That's more payload than Boeing's A160T and a lot faster than the Lockheed Martin/Kaman unmanned K-Max, both of which are to be demonstrated in the unmanned resupply role with an eye to early deployment with the US Marine Corps.

Carter's SR/C is basically an autogyro that slows its rotor significantly in flight to reduce drag and increase speed, transferring lift to the wing. The aircraft can do a vertical "jump" take-off by first spinning up the rotor, and can land vertically because the high inertia of the unpowered rotor keeps it spinning. Unlike the A160, which also slows its rotor, the SR/C needs no transmission or tailrotor. Carter's ultimate goal is a forward speed of 500mph with a rotor tip speed of just 100mph, which means the blades have to be extremely carefully designed to prevent divergence.

Carter has had its share of trials and tribulations in developing the SR/C, as seen in this video of the technology demonstrator, aka the CarterCopter, which crashed eight times in five years - without hurting anyone. But the company has persevered and AAI has confidence in the design - at least unmanned.


Video: Carter Aviation Technologies