Karem Aircraft will design a tiltrotor to meet U.S. Army future utility-rotorcraft requirements under one of four contracts awarded for Phase one of the Joint Multi Role technology demonstration.

JMR is a precursor to the Army’s planned Future Vertical Lift (FVL) Medium program to replace first the Sikorsky UH-60 Black Hawk utility helicopter and later the Boeing AH-64 Apache attack helicopter, beginning in the mid-2030s.

The Army’s Aviation and Missile Research, Development and Engineering Command has signed technology investment agreements (TIAs) with AVX Aircraft, Bell Helicopter, Karem and a Sikorsky/Boeing team.

A surprise entrant in the JMR program, Karem is designing the TR36TD demonstrator, an optimum-speed tiltrotor (OSTR) with twin 36-ft.-dia., variable-speed rotors powered by existing turboshaft engines.

Bell is designing a “third-generation tiltrotor, the V-280 Valor, while AVX is working on a coaxial-rotor, ducted-fan compound helicopter and Sikorsky a coaxial rigid-rotor, pusher-propeller design.

A JMR TD requirement is a cruise speed of at least 230 kt. — 50% faster that a conventional helicopter. Karem says a production version of the TR36D would have a level flight speed of 360 kt. Bell’s V-280 has a 280-kt. cruise, while the AVX and Sikorsky/Boeing designs are aiming for 230 kt.

The TIAs give all four teams nine months to complete preliminary design of their rotorcraft, after which the Army will review the competing designs and authorize the construction of two competing demonstrators to fly in 2017.

Karem says its variable-speed OSTR configuration offers advantages in weight, drive train and aerodynamic and propulsive efficiency. In addition to high speed, the TR36TD would have “robust” hover performance at altitude, higher climb rate and sustained maneuverability, and longer range than other vertical-takeoff-and-landing configurations, the company says.

The company also says the OSTR offers reduced complexity, inherent safety advantages, simplified maintenance and low total ownership cost.

Inventor Abe Karem designed the precursor to the Predator unmanned aircraft and the (now Boeing) A160 Hummingbird long-endurance unmanned helicopter with its optimum-speed rotor. He formed Karem Aircraft in 2004 to develop the OSTR concept.

From 2005-2010 Karem studied a version of the OSTR weighing more than 200,000 lb. under the Army-led Joint Heavy Lift (JHL) effort. The TR75 had two 75-ft.-dia., variable-speed rotors. Lockheed Martin teamed with Karem on JHL, which was eventually shelved for lack of funding.

The company is continuing private-venture development of two commercial OSTR aircraft, the 90-passenger AeroCommuter and 180-passenger AeroTrain.

[Editor’s Note: A160 typo corrected]