A burgeoning market for unmanned cargo delivery systems and long endurance intelligence, surveillance and reconnaissance (ISR) platforms for the US military has spurred Textron Systems subsidiary AAI to take a major technology stake in compound helicopter start-up, Carter Aviation Technologies.
The 40yr agreement gives AAI exclusive rights to Carter’s slowed rotor / compound (SR/C) technology for unmanned aircraft systems (UAS), while Carter gets AAI and sister company Bell Helicopter expertise in bringing a four-place manned version of the unusual aircraft to the civil market. No financial terms were disclosed.
“We’ve been aware of Jay (Carter) and his technology for quite a number of years,” says AAI vice president of unmanned aircraft systems, Steven Reid, referring to Carter CEO Jay Carter. “We really got close about a year ago.” AAI had been investigating a variety of technologies, including tilt rotors, to move cargo from unimproved launch and recoveries, a quandary faced daily in Afghanistan.
Reid says Carter’s slowed rotor / compound technology, which allows the pusher-propeller compound to slow its main rotor to approximately 100 rpm in cruise from 300rpm for vertical liftoff and landing, has matured to the point where AAI decided to invest. The slowing reduces drag approximately 26X on the rotor, says Carter, allowing for speeds that AAI plans to push as high as 250kt. At higher speeds, the aircraft's lift comes primarily from its fixed wings.
Artist conception of the AAI SR/C ©AAI
A technology demonstrator has achieved 180kt to date, says Reid, and a prototype of the four-place personal air vehicle (PAV) should be in flight testing “the first part of next year”, he says. Once a series of flight demonstrations are complete, Reid says AAI will begin developing an unmanned version that will be powered by turbine engine allowing for a payload of 3,000lb and maximum gross weight of 7,250lb. Traded for fuel, Reid says the aircraft will have a range of more than 1,300nm and endurance of more than 24h.
Reid says AAI and Bell engineers are performing static and dynamic testing of the compound’s rotor hub, a key element in the success of the technology. Highest risk, he says, will be “getting the speed that would be above what a normal helicopter can do”.
“We’re quite confident we can do the takeoff and landing as Jay has flown many pre-prototypes,” says Reid. “The fact is that this technology can fly is well proven, but the question is can we get the higher speed that will mean more utility for certain missions.”