Sikorsky unveiled the first S-97 Raider prototype on Thursday at an event in West Palm Beach, Fla. Sikorsky Photo
Four years ago, Sikorsky Aircraft announced plans for the S-97 Raider — a high-speed, coaxial-rotor compound helicopter based on the company’s X2 technology demonstrator. Sikorsky promised that the Raider, developed for the U.S. Army’s Armed Aerial Scout (AAS) program, would revolutionize the AAS mission, offering cruise speeds in excess of 200 knots without sacrificing the low-speed maneuverability of a traditional helicopter.
Last year, the Army put the AAS program on hold, determining that no existing aircraft met its requirements. Sikorsky and its more than 50 principal suppliers forged ahead, continuing their self-funded development of two Raider prototypes. Now, they have something to show for it. Sikorsky unveiled the first of the prototypes at an event in West Palm Beach, Fla., on Thursday, and the company remains optimistic that the aircraft will make its first flight by the end of the year.
“While the Armed Aerial Scout program is on hold for now, our commitment to the U.S. Army is not,” said Sikorsky president Mick Maurer at Thursday’s unveiling. “We said we would do it in four years, and we said we would do it without any government funding. We did it.”
With a maximum gross weight of 11,400 pounds (5,170 kilograms), the Raider will cruise at around 220 knots in an armed configuration, with an endurance of around 2.7 hours and a range of 370 miles (600 kilometers) with standard fuel. The Raider’s cockpit seats two pilots side-by-side, while its cabin will have space for up to six combat-equipped troops, or for internal auxiliary fuel tanks and extra ammunition.
Official literature for the Raider describes it as meeting the Army’s AAS hover-out-of-ground effect (HOGE) performance requirements of “6K/95” — hover capability at 6,000 feet mean sea level and 95 degrees F. In fact, it should significantly exceed these requirements, with Sikorsky’s director for Advanced Military Programs, Steve Engebretson, predicting HOGE capability at 10,000 feet at the same temperature.
Sikorsky said the Raider’s performance should allow it to refuel in flight at speeds and altitudes much higher than those typically used for helicopter aerial refueling. Sikorsky Image
The statistics only tell part of the story, however. The Raider’s revolutionary design offers more than speed — it promises capabilities not found in any conventional helicopter.
For example, because the aircraft’s clutched rear pusher propeller is operated independently of its main rotors, the Raider can hover with its nose pointed up or down, and accelerate rapidly in a level attitude. According to Andreas Bernhard, the program’s chief engineer, the propeller can be engaged in any flight regime, and can remain disengaged to lower the noise signature for stealth missions (in which configuration the Raider should have a top speed slightly higher than that of most conventional helicopters).
Moreover, there are software commonalities between the fly-by-wire Raider and Sikorsky’s Matrix autonomy research program — opening the door to optionally piloted and unmanned applications in the future.
“Raider marks the first unveiling of a new relevant rotorcraft configuration in 30 years,” stated Sikorsky vice president of Research and Engineering Mark Miller. “We are looking forward to getting air under its tires and expanding the envelope in flight test in the coming months.”
Despite the cancellation of the U.S. Army’s AAS program, Sikorsky is betting that the Raider will have eager customers. Sikorsky is funding 75 percent of the program; its 53 industry partners are funding the remaining 25 percent. Sikorsky Image
With the Raider’s software configuration locked down and substantial systems testing already complete, Sikorsky still expects the aircraft to fly by the end of the year, as originally planned. As there are no customer orders for the aircraft at present, the initial flight-test program is expected to encompass less than 100 flight hours.
However, Sikorsky has made it clear that the Raider represents a “practical air vehicle” — unlike the X2 technology demonstrator, which was permanently retired after just 23 flights. Beyond performance, the Raider’s design process has focused on aspects that are critical in production aircraft, such as cockpit ergonomics and crashworthiness.
“We’ve kept a close eye on lowering development, production and support costs while increasing productivity and quality,” stated Miller, calling the Raider “the solution for the future warfighter.” Whatever the future may hold in store for the Raider, “We’re confident it was a risk worth taking,” he said.