The XH-59 ultimately achieved 263 kt., but required two pilots, four engines and was thirsty, noisy and shaky. Three decades later, the X2 Technology demonstrator exceeded 250 kt. in level flight, and 260 kt. in a shallow dive, with one pilot, one engine and vibration levels similar to a Black Hawk at 150 kt. Fly-by-wire flight control, integrated propulsion, active vibration control and composite materials were among the technology advances that overcame the shortcomings of the XH-59.
The X2 was Sikorsky's response to criticism that neither the U.S. military nor industry was investing in new rotorcraft technology, and instead still building and buying 1970s designs. “The industry was being slammed hard for not being innovative,” says Mark Miller, vice president of research and engineering. “[Former Sikorsky President] Steve Finger ordered an extensive study of technologies that had been tried in the past. As technology advances, things that were not possible back then become worth taking a look at. The X2 coaxial rigid rotor came out of that.”
After designing and flying the X2 demonstrator in 43 months for $50 million in company funds, Sikorsky launched the S-97 Raider program, investing $200 million of its own and suppliers' money in two prototypes to reduce risk in pursuit of the Army's Armed Aerial Scout (AAS) requirement. The Raider also takes the X2 configuration a step closer in scale to JMR/FVL. “The S-97 will provide another data point on the same slope as the X2, but at a different gross weight, and show it can be done quickly and affordably, to an advanced manufacturing readiness level,” says Chris Van Buiten, vice president of technology and innovation and head of R&D arm Sikorsky Innovations.
Launched in October 2010, the Raider program has entered the final-assembly phase. The first all-composite fuselage was delivered by Aurora Flight Sciences in September and has cleared its 115% proof-load test. The landing gear has passed drop and retract tests and is being attached to the airframe. The windshield has successfully completed a birdstrike test at 229 kt., says Van Buiten.
The Raider is scheduled to fly at the end of 2014 and, after a year of envelope-expansion flight tests, Sikorsky hopes to begin demonstrations to the Army at the end of 2015 and be ready for an AAS competition—if the program is delayed, but not terminated, because of budget cuts—in 2016.
In addition to a doubling of mission speed and endurance and 150% increase in high/hot hover performance over the Army's Bell OH-58D Kiowa Warrior, Sikorsky wants to demonstrate specific attributes of the X2 configuration. These include level-attitude acceleration and deceleration using the variable-pitch pusher propeller, 3g maneuver capability and the ability to “hang on the prop” to direct weapons against ground targets.
Along with proving the coaxial rigid-rotor dynamic system scales up, Sikorsky plans to use its JMR demonstrator to show the advantages of those same attributes in the utility role, and particularly the benefits of maneuverability and level-attitude acceleration/deceleration to inserting or extracting troops rapidly and survivably, says Doug Shidler, JMR program director.
Sikorsky's strategy to focus its internal R&D on the three pillars and seek contract R&D to fill any gaps is paying off, says Miller. “JMR is a contract and an investment, and we have been able to attract a partner in Boeing, which is a 'Good Housekeeping' stamp of approval [for the X2 technology],” he notes. “There was nothing new going on, no investment in R&D, and [then-Sikorsky President] Jeff Pino said we can change that,” says Van Buiten. “We moved out with small investments in the three pillars and now we are seeing substantive progress—the X2 has flown, the S-97 is coming and we have won a JMR contract.”
JMR will also be a test of Sikorsky's ability, now with Boeing, to scale up its capacity to design and build an aircraft quickly and affordably. Having invested $250 million of its own and supplier money in the X2 demonstrator and Raider prototypes—without having yet attracted a customer—it faces the prospect of spending more money on the JMR demonstration.