flew its S-97 Raider rigid coaxial-rotor, high-speed helicopter for the first time May 22, completing a hover and low-speed flight at the company’s development flight center in West Palm Beach, Florida.
The aircraft is the first of two prototypes of the Raider light tactical helicopter being built under a $200 million industry effort funded by Sikorsky and its supplier partners. This follows the $50 million company-funded X2 Technology Demonstrator, which flew 23 times from 2008-11.
The Raider flew for 1 hr. instead of the 30 min. planned, says Mark Miller, vice president of research and engineering. It completed three takeoffs and landings: forward, rearward and sideward. The aircraft was flown by Raider chief pilot Bill Fell, with X2 test pilot Kevin Bredenbeck as co-pilot.
Rolled out Oct. 2, the first Raider had completed 36 hr. of shakedown ground runs since February. This culminated in an untethered ground run on May 20, clearing the aircraft for flight.
All 97 points on the “aggressive” first-flight test card were completed, including piloted frequency sweeps in all axes, something normally considered too risky for a first flight, Fell says.
The X2 demonstrator last flew in July 2011, having exceeded 250 kt., and Bredenbeck says the flight of the production-representative Raider “picked up … like the X2 program never ended.”
For this initial flight, the Raider was flown with its triplex fly-by-wire flight control system in backup degraded mode so as to focus on basic airworthiness in the low-speed regime, Fell says.
Over about 100 hr. of flight testing, aircraft 1 will expand the Raider’s flight envelope with the goal of achieving the program’s key performance parameters (KPP) by mid-2016, Miller says. These include demonstrating hover out of ground effect at mission weight at 6,000 ft. altitude on a 95F day (6k/95); 220 kt. cruise speed with external weapons; and 3G maneuverability at speed.
Flight testing will be conducted in three phases involving two blocks of flight-control software, Program Manager Mark Hammond says. For initial flights with Block 1 software, the Raider will fly in traditional helicopter mode without the propulsor engaged.
The Raider will be flown to 140-150 kt. in pure helicopter mode, Miller says. Toward the end of Phase 1, software will be upgraded to Block 2, bringing in the propulsor and articulating tail to increase speed and enable the full flight envelope.
Phases 1 and 2 will demo the hover KPP carrying the equivalent of six troops and two crewmembers as well as an endurance objective. Phase 2 will focus on demonstrating – and likely exceeding – the speed objective. “Raider is a balanced design optimized for more than 220 kt. fully weaponized, but the inherent speed of the configuration is more than 250 kt.,” Miller says. “That’s 100 kt. faster than anything else.”
Phase 3 will demo the maneuverability potential of the rigid coaxial rotor and propulsor. In addition to enabling level-attitude acceleration and deceleration and pushing the helicopter to higher forward speeds, the variable-pitch propeller can be used to produce reverse thrust, enabling the Raider to “hang on the prop” to point sensors and weapons toward the ground.
The second Raider is being assembled and is expected to fly late this year or in early 2016. Where aircraft 1 is heavily instrumented for envelope expansion and will remain at West Palm Beach, aircraft 2 is intended for customer demonstrations and, after an initial 50 hr. of flight testing, will be released to conduct demo tours to other locations. Aircraft 1 will be a backup.
The formal program will end once the KPPs have been accomplished, but the customer demonstrations will be open ended, Miller says. Sikorsky is in discussions with industry partners and potential customers about fitting specific sensors and weapons to aircraft 2 for demos in operational scenarios.
When Sikorsky launched the Raider program, it was aiming at the U.S. Army’s Armed Aerial Scout (AAS) requirement. This has since been shelved, withAH-64 Apache attack helicopters being used as armed scouts to replace the Army’s Bell OH-58D Kiowa Warriors, which are being retired.
Current Army plans call for a new Future Vertical Lift (FVL) Light armed scout sometime after 2030. But Sikorsky’s goal in demonstrating the operational effectiveness of the Raider using production-representative prototypes is to persuade the Army to revisit AAS or pull FVL Light forward.
While the X2 had a gross weight of 6,000 lb., the Raider weighs around 11,000 lb. and, Miller says, is also serving as a risk reducer for the 30,000-lb.-class SB-1 Defiant being built by Sikorsky and Boeing for the Army’s Joint Multi Role technology demonstation, a precursor to the FVL Medium program.