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Sikorsky "Raider X" (FARA)
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https://aviationweek.com/defense-space/sikorsky-evolves-raider-fara-armed-scout-contender

"Sikorsky Evolves Raider Into FARA Armed Scout Contender":

Graham Warwick July 04, 2019

On a hazy Florida morning, a sleek black helicopter makes a high-speed pass, close to 200 kt., the sound of its tail-mounted propeller unique for a rotorcraft. Seconds later, the noise changes as the prop bites into the humid air and the helicopter reverses down the runway and into a tail-high pirouette, circling with its nose laser-focused on a spot on the ground.

This is Sikorsky’s S-97 Raider, being put through its paces before a select group of suppliers the company wants on board to support its bid to build the U.S. Army’s next armed scout—the Future Attack Reconnaissance Aircraft (FARA).

Sikorsky is one of five companies chasing two contracts to build prototypes for a competitive flyoff in 2023. If successful, FARA would be the fourth instantiation of Sikorsky’s X2 high-speed helicopter configuration comprising the original 6,000-lb. technology demonstrator, the 11,500-lb. S-97 Raider and the 33,000-lb. Sikorsky-Boeing SB-1 Defiant demonstrator also now in testing.

FARA to be slightly bigger, slower than S-97

Raider addressing drag, vibration challenges

This line of aircraft has its origins in 2005 when, seeking to differentiate itself from other helicopter manufacturers and after analyzing a range of configurations, Sikorsky returned to the design of its XH-59 Advancing Blade Concept (ABC) coaxial compound helicopter demonstrator. First flown in 1973, this achieved 238 kt. in level flight.

To overcome the ABC’s drawbacks of complexity, vibration and high fuel consumption, Sikorsky applied technologies developed over the intervening years, including carbon-fiber blades and airframe, fly-by-wire flight controls, integrated propulsion system and active vibration control. The result was the X2 demonstrator, which in 2010 achieved 250 kt. in level flight with power still in hand.

The next step was to use the configuration “to make something useful,” says Steve Weiner, director of engineering sciences and “father of the X2.” The result was the S-97 light tactical helicopter, designed around the Army’s Armed Aerial Scout (AAS) requirements. Sikorsky and its supplier partners launched an industry-funded program to build two prototypes, the first of which flew in May 2015.

AAS was canceled in 2013, with the Army blaming budget sequestration. It then retired the Bell OH-58D Kiowa Warrior armed scout that AAS was to replace, and its role was transferred to the Boeing AH-64E Apache. But the Army acknowledges the attack helicopter is not best suited to armed reconnaissance, and in 2018 FARA emerged as an urgent requirement to field 200 new armed scouts beginning in 2028.

On paper, Sikorsky looks well placed to win FARA. The company, its parent Lockheed Martin and its industry partners have invested about $300 million in the Raider program, says Chris Van Buiten, vice president of Sikorsky Innovations. The second prototype has exceeded 200 kt. in flight testing, and FARA would be an evolution of the S-97 configuration, not an entirely new design.

But Sikorsky faces a challenge. To enable a competition, the Army has trimmed its requirements for FARA, setting a minimum speed of 180 kt.—fast for a conventional helicopter, but slow for the X2. That speed requirement pits Sikorsky’s coaxial-rotor compound design against single-main-rotor helicopters and brings the affordability of its more capable, but more complex configuration into sharp focus.

Tim Malia, Sikorsky’s director of future vertical lift–light, describes the company’s driving priorities for FARA as a triangle, with schedule, performance and affordability as the three sides. The Army has made clear that “schedule is king,” he says, but to win the company must also get the other two right.

Sikorsky should be in a good position on schedule. The Raider has already logged more than 55 hr. of flight testing, reaching 207 kt. in level flight and pulling 2g in maneuvers. The first prototype was damaged in a hard landing in August 2017, but the second aircraft has been transferred to the FARA team, and flight testing refocused on reducing the risk in Sikorsky’s proposal.

The Raider was showcased to industry partners (see video), and the press, on June 25 with a demonstration at Sikorsky’s development flight center in West Palm Beach. This highlighted unique capabilities enabled by the compound-helicopter’s combination of rigid coaxial rotors and tail-mounted propulsor.

There are two 34-ft.-dia. contrarotating four-blade rotors. The blades are stiff and the hubs hingeless so the rotors can be mounted close together, reducing drag. This configuration enables higher airspeed because the lift is generated by the advancing blades on each side, allowing the pitch of the retreating blades to be reduced and avoiding the blade stall that limits the speed of conventional helicopters.

Rotor speed is scheduled with tip Mach number, and reduces to a minimum of 85% rpm as airspeed increases to prevent the advancing blades from going supersonic. The distance between the tips of the upper and lower rotors is actively sensed. Two-thirds of the tip gap is to allow for blade flexing during maneuvers and one-third is the safety margin, says Bill Fell, senior experimental test pilot.

In the August 2017 accident, a flight-control software error led to a roll rate on liftoff three times greater than intended. Gyroscopic forces caused the rotor tips to collide. “We fixed the error in the code and we now completely understand the physics,” he says. “Our job is to make sure it never happens again.”

The Raider is powered by a single 2,600-shp General Electric YT706 turboshaft. In hover and at low speed, power goes to the rotors and the propulsor is declutched. As speed increases and the propulsor is engaged, power shifts to the six-blade, variable-pitch pusher propeller. At high speed, 90% of the power goes to the propulsor, says Fell.

Pilots increase or decrease propulsor thrust using a “beep” switch on the central collective lever. This moves propeller pitch through its range of +50 to –20 deg. The rotors can take up to 1,800 shp of power, the propeller 2,200 shp. The engine cannot provide full power to both simultaneously, so the integrated digital engine and flight controls automatically maintain the rotor power required for lift and limit the propulsor to the excess power available.

The Raider can fly at up to 150 kt. with the propeller disengaged. This allows the helicopter to dash at high speed then declutch the propulsor to reduce the noise on approach to the target. There is no anti-torque tail rotor. As the prototype demonstrated during two passes, there is a significant reduction in acoustic detectability when the propeller is disengaged.

The propulsor offers other unique capabilities. Conventional helicopters tilt nose-down to accelerate and nose-up to decelerate. Using forward or reverse thrust on the propeller allows the Raider to slow down or speed up with a level fuselage attitude. This is valuable when carrying casualties or passengers, says Van Buiten. Tactically, using the propeller can prevent the aircraft popping up into the sights of enemy defenses when flying over a ridge during high-speed nap-to-the-earth flight.

By using reverse thrust on the propeller, counteracted by forward thrust on the rotors, the S-97’s fuselage can be pointed downwards. Fell showed how this allows sensors or weapons to dwell on the target as the Raider circled, nose down. Forward thrust on the propeller, balanced by rearward thrust on the rotors, allows the fuselage to be pointed upward. These are capabilities conventional single-rotor helicopters do not have, but the value of which must still be demonstrated to the customer.

Although speed is no longer the focus of testing, Sikorsky still hopes to achieve the Raider’s 220-kt. design goal. “We underestimated the drag,” says Fell, “but there are dials we can tweak.” Sikorsky is preparing to install a new set of rotor blades, redesigned to reduce drag and vibration at high speed—another area of concern with the rigid-rotor helicopter. In addition to being stiff, the Raider’s blades are complex, with changing thickness and chord across five different airfoil sections from root to tip.

Fell says vibration in the Raider at more than 200 kt. is similar to that in the UH-60 Black Hawk at 150 kt. But the potential impact of vibration on crew fatigue, aircraft systems and component lives is a concern, although the S-97 is equipped with an active vibration control (AVC) system. The new blades have been redesigned to improve aerodynamic efficiency, but how they attach to the hingeless hubs also has been modified, says Fell, to reduce the transmission of vibratory forces from the blades into the airframe.

The importance of minimizing vibration was illustrated during the demonstration flight. Fell says the flight plan called for a 200-kt. high-speed pass, but maximum speed was held to 190 kt. “We planned 200 kt., but a new script file in the AVC did not work out and there was no reason to push it,” he says. AVC actively cancels vibration by introducing opposing forces into the airframe.

Mitigating vibration is one example of risk-reduction testing the Raider will perform for the FARA team, which is nearing its preliminary design review. Because the Army has reduced its speed requirement, Sikorsky’s FARA design will be “detuned” relative to the Raider, but will still have more growth potential than a single-rotor helicopter already at the limits of its capability at 180 kt, says Malia.

With a larger, 39-ft.-dia. rotor system, a higher, 14,000-lb. gross weight and a single, 3,000-shp General Electric T901 Improved Turbine Engine, the FARA will be slower than the Raider, he says. There will be other changes. The fuselage will be stretched to accommodate two 80-in. long internal bays for weapons, air-launched unmanned aircraft and other mission payloads. There will be no external stores on FARA, Malia says, and these bays will essentially replace the Raider’s passenger cabin.

The fuselage will be tuned to minimize vibration, he says. Sikorsky has already selected Swift Engineering to build the airframe for the FARA prototype. Aurora Flight Sciences built the Raider fuselage, but is now owned by Boeing, and Swift manufactured the airframe for the SB-1 Defiant. Suppliers of other long-lead components are also already on board, Malia says, to meet a schedule that calls for contract award in March 2020, flight in first-quarter fiscal 2023 and the Army flyoff in the fourth quarter of that year.

The landing-gear arrangement is different on the FARA design, and there are changes to the propulsor. On the Raider, when the propeller is disengaged a limited-slip clutch keeps it turning at 200 rpm. This is to avoid heat damage to a blade by the engine exhaust, which is located above the tail, just forward of the prop. On FARA, as on the Defiant, the exhaust design is different and the propulsor will stop completely. Sikorsky could also redesign the propeller blades to reduce noise in high-speed flight.

For Sikorsky, tailoring its X2 configuration to the less-demanding FARA requirements is crucial to making it affordable. But the company wants to preserve the design’s inherent growth capability—particularly in speed—because it sees this as a differentiator. After decades of false starts, the Army urgently needs an armed scout. A conventional helicopter could do the job, but Sikorsky needs the service to take the long-term view and pick a configuration still at the beginning of its evolution.



-- Edited by Stingray on Wednesday 10th of June 2020 02:11:08 AM

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Sikorsky "Raider X"
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https://www.verticalmag.com/news/sikorsky-reveals-raider-x-for-armys-fara-program/

"Sikorsky reveals Raider X for Army’s FARA program":

Posted on October 14, 2019 by Dan Parsons

Sikorsky has unveiled a sleek, beefed-up version of its S-97 Raider coaxial compound helicopter specifically designed for the U.S. Army’s Future Attack Reconnaissance Aircraft (FARA) competition.

Keeping with the company’s lineage of experimental rotorcraft, the new aircraft is called the Raider X and is a direct descendent of the S-97 Raider that has been in test for several years. The new concept retains the basic coaxial main rotor configuration with an aft pusher propulsor, but is 20 percent larger than the S-97.

Where the S-97 has a 34-foot (10.4-meter) main rotor diameter and is built around a GE YT706 engine, its evolutionary descendant will have a 39-foot (11.9-meter) main rotor diameter and be built to accept the GE T901 engine the Army has prescribed for FARA, according to Tim Malia, Sikorsky’s FARA program director.

Though it holds a $940 million initial design development contract to produce a FARA concept, Sikorsky is further along the development curve than any of its competitors. The S-97, which has been in flight test since 2015, is being employed as an 80-percent scale model of the new, larger Raider X.

Sikorsky unveiled the Raider X design Oct. 14 at the Association of the U.S. Army’s annual conference (AUSA) in Washington, D.C. Just a few hundred feet away are full-scale mockups of FARA aircraft pitches by Bell and AVX/L3, both of which are in initial design. A Karem/Northrop Grumman/Raytheon team has gone public with its pitch, but also is in the design development stage. Boeing has said next to nothing about its pitch, but insists it is heavily into design development and buying up long-lead time materials to build a prototype.

By contrast, Sikorsky has four years of what it says are highly representative flight test data from the S-97 Raider, which was initially designed to now defunct Army requirements for an Armed Aerial Scout Helicopter. No worry, says chief test pilot Bill Fell. The company can comfortably lean on its experience with the smaller S-97, to the point he and other Sikorsky officials are using that operational prototype almost as an interchangeable stand-in for its eventual FARA prototype.

“We’re not in Powerpoint,” Malia told reporters Oct. 14. “We’re not putting Bondo on plywood.”

Raider X increases the weight of the aircraft from about 12,000 pounds to 14,000 pounds (5,445 to 6,350 kilograms), Malia said. It features a side-by-side co.ckpit, which also widens the fuselage to increase its internal weapon storage.

Carrying weapons internally reduces drag and allows the aircraft to achieve speeds well above the Army’s 180-knot requirement. Raider has already flown 207 knots in level flight and 250 in a shallow dive. The larger, more powerful Raider X should be able to fly faster than that, Fell said.

“We’re going from a 12,000-pound Raider to a 14,000-pound Raider by upsizing everything just a little bit,” Fell said. “We’re flying and collecting detailed flight test data on a fully instrumented aircraft. We know what the loads are. We know what the vibration characteristics are. We know what the power required is. We know what the performance of this aircraft is, so the relative risk is really low as we go to a slightly upsized Raider X going into the FARA program.”

 



-- Edited by Stingray on Wednesday 10th of June 2020 02:01:10 AM

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https://www.lockheedmartin.com/en-us/products/fara-raider-x.html



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RE: Sikorsky "Raider X" (FARA)
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"Advancing the Next Generation of Army Aviation: FARA Enters Prototype Phase":

https://www.lockheedmartin.com/en-us/news/features/2020/raider-x-enters-fara-prototype-phase.html

Sikorsky will offer aviators battlefield advantage in its RAIDER X™ helicopter

The Army calls the Future Attack Reconnaissance Aircraft (FARA) a “knife fighter” for the future battlefield. This out-front platform will fly into the most demanding and contested environments and requires maximum performance in a small package. Sikorsky’s RAIDER X is ready to fill this requirement. 

RAIDER X is specifically designed for vertical lift dominance against evolving peer and near-peer threats in a joint all domain environment. The U.S. Army selected RAIDER X to move to the second phase of the FARA competitive prototype program as part of the future vertical lift pursuit. This means that Sikorsky will further mature the design, development and build of the RAIDER X prototype, leading up to a flight test program. RAIDER X offers:

  • Reach in the forms of speed, combat radius, endurance and payload
  • Survivability through a revolutionary, game-changing leap in holistic protection, maneuverability and agility including a Modular Open Systems Approach (MOSA) that quickly adapts to new technology and threat capabilities.
  • Lethality that includes a combination of speed, payload and maneuverability to employ an array of sensor and weapon systems coupled with MOSA to rapidly field and employ new capabilities.
  • Sustainment that is designed into the aircraft using a digital thread to decrease aircraft operating costs by utilizing new technologies to shift from routine maintenance and inspections to self-monitoring and condition-based maintenance, which will increase aircraft availability, reduce sustainment footprint forward and enable flexible maintenance operating periods thread
  • Growth and Mission Flexibility that is focused on the future and ever evolving threat capabilities, X2 compound coaxial technology provides unmatched potential and growth margin for increased speed, combat radius and payload. This potential and growth margin further enables operational mission flexibility which includes a broader range of aircraft configurations and loadouts to accommodate specific mission requirements.

X2 Technology is at the core of Sikorsky’s S-97 RAIDER program. This suite of technology combines rigid, counter-rotating blades, fly-by-wire flight controls, and an integrated auxiliary propulsion system.

The S-97 RAIDER’s flight test program has demonstrated the requirements of the FARA program. Sikorsky is so confident in its RAIDER X offering because of the experience being built up with the S-97 RAIDER in flight. The technology that will be incorporated into RAIDER X is already being proven not on paper or in simulation, but on the flight field. This significantly reduces risk for the RAIDER X concept, which is already being built.

Sikorsky will continue to mature X2 Technology through the S-97 RAIDER flight test program.

“The power of X2 is game changing. It combines the best elements of low-speed helicopter performance with the cruise performance of an airplane,” said Sikorsky experimental test pilot Bill Fell, a retired Army pilot who has flown nearly every RAIDER test flight. “Every flight we take in our S-97 RAIDER today reduces risk and optimizes our FARA prototype, RAIDER X.”

Sikorsky is no stranger to the Army mission, with over 40 years of partnership supporting the needs of Army aviators. RAIDER X will give warfighting commanders day one battlefield advantage. 



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https://breakingdefense.com/2020/06/speed-maneuverability-survivability-and-sustainability-are-the-hallmarks-of-sikorskys-x2-technology/amp/

Breaking Defense: Let’s move on to sustainment as it relates to Sikorsky’s FARA and FLRAA helicopters. What do they offer the Army in terms of maintainability and sustainment?

Macklin: FARA and FLRAA gave us the ability to build a new helicopter that from the outset is focused on reduced maintenance burdens. This has been exciting! We’ve challenged the team to ask the question “What would it take to make our new helicopters be more like our cars and in many cases even better, where the reliability is increased, maintenance is much easier, and the vehicle is much smarter… actually telling the crew and maintainers well in advance when it sees that something is degrading and pro-actively addressing concerns before they become issues. Switching away from time phased maintenance and into predictive and condition-based maintenance is a game changer. Our aircraft leverage sensor technology that is embedded all over the aircraft and systems to self-monitor and predict future maintenance requirements. The aircraft layout allows ready access to maintenance areas when the needs to arise.

We are fully leveraging the digital transformation and model-based design and maintenance which allows us to Maintain before we Build… using virtual reality to influence our design early in the design process, improving the product for the warfighters. These design enhancements will contribute to the reduction in O&S costs resulting in total cost of ownership savings. We know that we will have to operate in austere environments, with limited crews and limited sustainment for extended periods of time, and our engineering team has risen to this challenge and implemented these next generation technologies to reduce our operating and maintenance costs by over half.



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