Sikorsky [UTX] has paused flight testing on its experimental coaxial-rotor S-97 Raider to focus on operation of its ground-test station.
The first S-97, which incorporates dual rotors and an aft pusher prop to achieve helicopter hover capabilities and fast flight like an airplane, has flown just 2.2 hours during two flights since its first flight in May.
The same aircraft has undergone 47 hours of tethered ground testing while the ground test station, which is a skeletonized terrestrial test bed for the aircraft’s main operational components, has undergone only about 40 hours of testing, said Bill Fell, Sikorsky’s chief test pilot on the program.
“Normally, you qualify all the systems on the aircraft with the ground test stand,” Fell said during a walk-around of the aircraft at the Association of the U.S. Army’s annual exposition in Washington, D.C. “Now we have our ground test stand up and running and we have about 40 hours on it. Right now the aircraft is leading the ground test stand a little bit. So we’re going to take a small step back now to put a lot of hours on the ground test stand and make sure that we have the flight safety to continue to expand the envelope on the aircraft.”
Delaying aggressive flight test tracks with the program thusfar. Sikorsky several times delayed first flight of the aircraft because it chose to proceed deliberately with maturing a technology that could revolutionize rotorcraft but for which there is no existing military requirement.
The 11,500-pound S-97 is based on Sikorsky’s X-2 technology demonstrator. Both platforms were funded internally by the company based on anticipated requirements for improved rotorcraft performance.
The S-97 is designed as an armed scout helicopter, though the Army has scrapped plans to replace its aging OH-58D Kiowa Warrior fleet in favor of handing the scout mission to AH-64 Apache gunships teamed with unmanned aircraft.
Raider is the basis for Sikorsky and Boeing’s [BA] SB-1 Defiant, which is the team’s offering for the Army’s Joint Multi-Role technology demonstration (JMR) program. JRM-TD will inform the eventual Future Vertical Lift (FVL) family of rotorcraft that will replace the Army’s current fleet beginning with a medium-weight aircraft to fill the role currently performed by the UH-60 Black Hawk. It simultaneously is being offered for the light variant of FVL.
Bell Helicopter [TXT] and Lockheed Martin [LMT] are offering the V-280 Valor next-generation tiltrotor for JMR. The competition became somewhat muddied with the recent acquisition of Sikorsky by Lockheed Martin, effectively giving Lockheed Martin a hand in both of the two JMR offerings.
Mark Miller, Sikorsky’s Vice President of Research and Engineering, said the acquisition would cause “zero complications.” Lockheed Martin is providing avionics and other flight control systems for the aircraft.
“Lockheed is a large supplier to many programs,” he said. “That effort [JMR] will be firewalled from this program [Raider].”
The entire planned flight test program for Raider is between 110 and 120 hours, Fell said. After running the ground test stand for 200 hours, pilots will get “the green light to expand the aircraft’s envelope” and flight testing will resume, he said. Fell and other test pilots then will gradually widen the envelope and increase the speed of flight up to the expected 200-plus knots the aircraft is designed to fly.
“The plan is to have aircraft one up to its full speed envelope by next summer, but during flight testing you never know what kind of problems are going to come up,” Fell said.