Sikorsky S-97 Raider
|S-97 Raider mockup|
|Role||Scout and attack compound helicopter|
|National origin||United States|
|First flight||22 May 2015|
|Program cost||US$200 million|
US$15 million, projected
|Developed from||Sikorsky X2|
The Sikorsky S-97 Raider is a proposed high-speed scout and attack compound helicopter based on the Advancing Blade Concept (ABC), under development by Sikorsky Aircraft. Sikorsky planned to offer it for the United States Army's Armed Aerial Scout program, along with other possible uses. S-97 made its maiden flight on 22 May 2015.
First proposed in response to a Request for Information for the Armed Aerial Scout program in March 2010, the S-97 was formally launched on 20 October 2010. It is intended as a possible contender for the United States Army's requirement for an Armed Aerial Scout to replace the Bell OH-58D Kiowa Warrior. Other military roles are possible, with the U.S. Special Operations Command having expressed interest in the concept as a replacement for the MH-6 Little Bird, and the possibility of adapting it for civilian applications also exists.
The S-97 was projected to undergo a program review in 2011, and was expected to make its first flight at the end of 2014. Sikorsky plans to build two prototypes of the S-97 as demonstrators. One prototype will be used for flight testing, while the second is planned for use as a demonstrator. The first prototype was planned to fly in late 2013 or early 2014 near the release of the Armed Aerial Scout Request for Proposals. Sikorsky started construction of the two prototypes in October 2012. In September 2013, Sikorsky began final assembly of the first S-97 Raider following delivery of the single-piece, all-composite fuselage by Aurora Flight Sciences.
Sikorsky is also using the technology and design process, along with partner Boeing, as a basis from which to develop a high-speed rigid rotor co-axial design called SB-1 Defiant for the army's Joint Multi-Role Technology Demonstrator (JMR TD) programme. The JMR TD is the precursor to the army's estimated USD100 billion Future Vertical Lift (FVL) programme, which is meant to replace the army's UH-60 Black Hawk utility helicopters and AH-64 Apache attack helicopters. One prototype Raider will be used for testing; a second Raider will be used for demonstrations.
Sikorsky targeted the S-97 for the AAS program, aiming for the helicopter to fly before the Army downselected. Sikorsky invested $150 million and its 54 suppliers (who provide 90% of the parts) spent the remainder of a total of $200 million on two prototypes, with production models to meet the $15 million unit cost target for the program. However, the Army ended the AAS program in late 2013.
In February 2014, construction of the first S-97 prototype airframe was one-quarter complete. Simulated bird strikes testing had been conducted on the fuselage at speeds of up to 235 kn (435 km/h; 270 mph), the S-97's expected maximum flight speed. Drop tests were also performed to ensure the safety of the fuel tanks in the event of a crash. Sikorsky is exploring civil applications for the S-97, such as transporting personnel between offshore oil platforms.
Budget projections for FY 2015 include a measure to retire the U.S. Army's OH-58 Kiowa fleet and remove AH-64 Apache attack helicopters from U.S. Army Reserve and U.S. Army National Guard control and transfer them to the active Army to take the place of the aerial scout role. Sikorsky has suggested the possibility of buying the S-97 Raider as a replacement for the loss of Apaches to fulfill armed helicopter needs.
|S-97 first flight by pilots Bill Fell and Kevin Bredenbeck on YouTube|
On 5 May 2014, Sikorsky opened the production hangar to the S-97 during the rollout of the CH-53K King Stallion, with a target of flying the aircraft by 1 December 2014. The mostly composite airframe was almost fully assembled and included wiring and some avionics systems; still missing was the transmission, drive train, engine, coaxial rotor, and pusher propeller, with the wiring to be completed very shortly to power-on electrical systems. The S-97's first military customer is aimed to be the U.S. Special Operations Command to replace the MH-6M Little Bird. Unspecified foreign militaries have shown interest in the S-97 design. With the U.S. Army's AAS program on hold (but not cancelled outright), it may be difficult to get approval for export for a next-generation helicopter if the American military does not yet have it. The Raider is a prototype, so the first customer would need to fund and support a production development program. Its avionics were powered on in June 2014, and Sikorsky expected first flight the same year, with rollout on 2 October 2014.
The first flight of the S-97 occurred on 22 May 2015. The Raider flew for 1 hour instead of the 30 minutes scheduled, completing three takeoffs and landings; forward, rearward and sideward. 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. The flight begins a year-long test program of about 100 flight-hours to expand Raider’s flight envelope to meet Sikorsky’s key targets of 220-knot cruise speed carrying weapons, to hover at 6,000 feet on a 95F day and 3g maneuverability at speed. Toward the end of Phase 1 testing, software will be upgraded to Block 2, bringing in the propulsor and articulating tail to increase speed and enable the full flight envelope.
|View of machinery in starboard side|
The S-97 design includes variable speed coaxial main rotors and a variable-pitch pusher propeller, making the S-97 a compound helicopter. Like the X2, it has fly-by-wire control and dynamic anti-vibration actuators to cancel out shaking. The S-97 will be capable of carrying up to six passengers, in addition to a flight crew of two in a side-by-side cockpit. However, the production S-97 is projected to be capable of flying with either one or two pilots, or autonomously. Space for a targeting sensor has been reserved, however it will not be installed in the prototype aircraft.
Based on the technology from the Sikorsky X2 demonstrator, the prototype S-97s will be powered by a General Electric YT706 turboshaft (the same engine used on the UH-60M Black Hawk), however a more powerful engine, developed under the Improved Turbine Engine Program, is expected to become available. Compared to the OH-58D Kiowa, the S-97 has significantly increased performance goals, such as cruising speeds upwards of 200 knots while carrying weapons, turning at three times the force of gravity at 220kt, and a high hover efficiency (Figure of merit). Sikorsky also aims for an operating cost of $1,400 per flight hour.
- Crew: 0-2 pilots
- Capacity: 6 troops
- Length: 35 ft (11 m)
- Gross weight: 8,945 lb (4,057 kg)
- Max takeoff weight: 11,000 lb (4,990 kg) 
- Powerplant: 1 × General Electric YT706 , 2,600 shp (1,900 kW)
- Main rotor diameter: 1 (2 coaxial)× 34 ft (10 m)
- Propellers: 6-bladed variable-pitch, clutchable pusher propeller, 7 ft (2.1 m) diameter
- Cruising speed: 253 mph; 407 km/h (220 kn)  (with external weapons)
- Never exceed speed: 276 mph; 444 km/h (240 kn) 
- Range: 354 mi; 308 nmi (570 km)
- Endurance: 2hr40min
- Service ceiling: 10,000 ft (3,048 m) at 95 °F (35 °C)
- Guns: .50 cal gun w/500 rounds
- Rockets: 7 shot rockets pod
- Related development
- Aircraft of comparable role, configuration and era
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- S-97 Rollout Sikorsky
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