Karem AR40 rendering (Picture source: Karem Aircraft)The AR40 aircraft has a 12.2m (40ft) wingspan – wider than the helicopter’s 11m main rotor diameter. The wing can provide the majority of the aircraft’s lift and tilts upwards during the helicopter’s descent or ascent in order to make its vertical flight more aerodynamic.
The AR40 also has a swiveling tail rotor, which in forward flight is angled backwards to be used as a pusher propeller. The company says in forward flight the aircraft’s vertical stabiliser compensates for torque from the main rotor blades. The swiveling tail rotor should allow for the aircraft “to manoeuvre aggressively at low speeds,” says Karem.
The design also has a three-blade main rotor that uses Karem’s Optimum Speed Rotor technology, which was initially developed using US Army research funds to create optimal efficiency for tiltrotors in vertical or horizontal flight.
On the AR40 helicopter, the system would be used to control each individual blade as it rotates, instead of forcing the blades to move in unison as is the case with a traditional swashplate system, says Thomas Berger, director of the FARA program at Karem.
“You're able to shape the trajectory of the blade path around the azimuth,” he says. “Being able to shape the trajectory gives you the possibility to get better performance, better acoustics, better reliability, automatic tracking.”
Karem believes the AR40 should be able to exceed the US Army’s 180kt (333km/h) maximum speed requirement by 40kt.
Northrop Grumman and Raytheon partnered with Karem Aircraft on the AR40. Karem is contributing its rotor and drive technologies, and is leading the design and prototyping process. Northrop is providing production and product support, as well as avionics expertise. Raytheon is the mission systems integrator and modular open systems architect.
The Future Attack Reconnaissance Aircraft (FARA) program was initiated by the United States Army in 2018 to develop a successor to the Bell OH-58 Kiowa scout helicopter as part of the Future Vertical Lift program.
Design contracts for FARA candidates were awarded in April 2019 to five manufacturers: AVX Aircraft (in partnership with L3Harris Technologies), Bell Helicopter, Boeing (not unveiled yet) , Karem Aircraft, and Sikorsky Aircraft (owned by Lockheed Martin). Two of the manufacturers will be selected to proceed with their designs in 2020, and prototypes are scheduled to first fly in 2023.