Test pilots pushed Sikorsky’s S-97 Raider to the limits as it performed moves no ordinary helicopter could. The S-97 Raider flew sideways, nose-down, backwards, and even in stealth mode. The flight test proves that a software problem blamed for a setback in 2017 has been fixed. Eric Adams of Vertical details how the S-97 handled like a sports car (abridged):
During a 20-minute test flight of the prototype S-97 Raider at Sikorsky’s West Palm Beach, Florida, facility — conducted in front of four journalists in the first such public demonstration — the unconventional coaxial-rotor aircraft performed routines that would make any helicopter pilot jealous.
For instance, the single-engine Raider, which Sikorsky is using as a test bed as it develops its entry for the U.S. Army’s Future Attack Reconnaissance Aircraft (FARA) competition, used reverse pitch on its rear propeller to maintain a nose-down attitude in a steady hover — as if targeting weapons or sensors to the ground, searching for injured hikers, or inspecting a landing zone. It’s a move no other helicopter can execute without drifting. Then it maneuvered briskly and perfectly above the runway, performing multiple tight patterns with an agility made possible by its rigid, stacked rotors, which rotate in opposition to each other, counteracting torque and negating the need for a tail rotor. Most other helicopters, with their hinged, flexing blades, can’t come close to that sort of precision.
Test pilot Christiaan Corry described the S-97 Raider’s performance characteristics in a way that seemed to suggest that he and his program colleague, Bill Fell, who commanded the flight, might actually have the best job in the world. “It really handles like a sportscar,” Corry said. “We don’t have an inverted oil or fuel system in this aircraft, but aerodynamically, it could fly inverted all day long. We demonstrated that in the simulator, and are proving every day that Raider can do so much in the air. The rotor system acts like a wing, and we can do these aerobatic maneuvers that just aren’t things helicopters could ever do before.”
The test seemed to validate that point. As the crew cycled through its test card on that characteristically sweltering Florida morning, we also saw Raider perform turns in half the distance of other helicopters and accelerate and brake with the fuselage completely level, thanks to the rear propeller that sits in place of the tail rotor. Whereas conventional helicopters must tilt their main rotor discs forward in order to accelerate — and backward to slow down — in the Raider, the rear propeller can be used to push the helicopter to faster speeds and also, with the blade’s pitch reversed, practically stop it on a dime. Engaging reverse pitch while simultaneously tilting the main rotors forward enables the nose-down hover. The Raider can also hover with its nose pointed skyward, by tilting the main rotors aft while generating forward thrust with the prop.
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