The U.S. Army is immersed in testing with two industry teams contracted to develop and build a fuel-efficient, high-speed, next-generation medium-lift helicopter to enter service by 2030.
The service’s Joint Multi-Role Technology Demonstrator, or JMR TD, program awarded development deals to Bell Helicopter-Textron and Sikorsky-Boeing teams to build demonstrator aircraft by 2017 to help inform the development of a new medium-class helicopter.
“These teams will build technology demonstration aircraft with flight tests starting in 2017,” an Army statement said.
Textron Inc.’s Bell Helicopter is building a tilt-rotor aircraft called the Bell V-280 Valor – and the Sikorsky-Boeing team is working on early testing of its SB> 1 Defiant coaxial rotor-blade design.
Planned mission sets for the JMR include cargo, utility, armed scout, attack, humanitarian assistance, medical evacuation, anti-submarine warfare, anti-surface warfare, land/sea search and rescue, special warfare support, vertical replenishment, airborne mine countermeasures, and others, Army officials said.
Although requirements for the aircraft are still being refined, the notional concept is to succeed in building a new aircraft which can reach speeds of 230 knots, carry up to 12 troops, operate in what’s called “high-hot” conditions and achieve a combat radius of 424 kilometers.
A key intent of the program is to develop a fuel-efficient aircraft which can reach high-speeds while retaining an ability to hover and maneuver as though it is a traditional helicopter.
A combat radius of 424 kilometers means the aircraft will be engineered with an ability to fly 848 kilometers on a round-trip mission without needing to refuel. Along with calling for increased fuel efficiency, the draft requirements also ask that the aircraft be able to operate at altitudes of 6,000-feet and temperatures of 95-degrees Fahrenheit.
Described as “high-hot” conditions, the decreased air pressure at higher altitudes and hotter atmospheric temperatures typically make it more difficult for helicopters to maneuver, maintain lift and operate effectively.
The JMR TD program, run by the Army Aviation and Missile Research Development and Engineering Center and Program Executive Office- Aviation, is also closely tracking offerings and developments from two other industry teams – Karen Aircraft Inc. and AVX Aircraft Company, an Army statement added.
"The intent of the JMR TD effort is to maximize the knowledge gain and risk reduction toward an anticipated Future Vertical Lift acquisition program," said Dan Bailey, JMR/FVL Program Director. "The baseline strategy based on the current funding allocation requires de-scope from the four initial designs to two for build and flight test."
The SB> 1 Defiant uses two, rigid counter-rotating coaxial rotor-blades along with a pusher-prop propeller at the back of the helicopter to provide additional thrust, said Doug Shidler, JMR program director, Sikorsky.
“Coax systems are not new they have been around for quite some time. The advantage that we are employing here is a rigid rotor with a left-offset that eliminates the need for lead-lag. We are able to bring the rotor heads closer together which, in forward speed, reduces aerodynamic drag that exists between the rotor heads,” Shidler told Military.com.
The pusher-prop on the back of the aircraft is a small propeller behind the counter-rotating rotor heads. It operates with what’s called positive and negative pitch, allowing the aircraft to lean up or down and move both forwards and backwards, he added.
“It enables you to hover with a nose up or nose down attitude so for mission execution you can engage an enemy on a ridge line or in a valley without losing sight. You can sit there in a hover,” Shidler added.
The pusher prop is part of the technological mechanism which enables the aircraft to reach much greater speeds that helicopters have historically flown.
“When it (pusher-prop) is disengaged, the aircraft can fly as a conventional helicopter and fly up to 150 or 160 knots. Once you engage the prop itself that gives you much greater speed. With the pusher prop as you engage it you can take off pretty much like a fixed-wing aircraft. Or you can choose not to utilize the prop and take off and land like a conventional helicopter,” Shidler said.
The Sikorsky-Boeing team has already conducted reduced-scale drag wind-testing and planned additional power-model wind tunnel testing in coming weeks.
“Scaled-model wind tunnel tests provide us with aerodynamic data to ensure that the models are tools that we’ve been employing on the design properly,” Shidler said.
While the Sikorsky-Boeing team hopes their design is ultimately the one chosen by the Army for the platform, they recognized they are in part helping to inform the maturation of performance-enhancing technologies for future use.
“Our goal is to influence the analysis of alternatives and help the government make the right decision. We want to be flying by the end of the fiscal year 2017,” said Pat Donnelly, JMR deputy program director, Boeing. “We’ve completed our preliminary design and we are now in our detailed design phase where we are working with suppliers to put together a plan.”
The Army plans to closely analyze the development of the JMR demonstrator helicopters with a mind to determining which design will ultimately become a program of record for the future.