Future Long-Range Assault Aircraft (FLRAA)

Future Long-Range Assault Aircraft (FLRAA)

The Future Long-Range Assault Aircraft (FLRAA) program was initiated by the United States Army in 2019 to develop a successor to the Sikorsky UH-60 Black Hawk utility helicopter as part of the Future Vertical Lift program. The UH-60, developed in the early 1970s, has been in service since June 1979. Like the UH-60, FLRAA variants would also serve United States Special Operations Command and the United States Marine Corps. Under the existing Joint Multi-Role Technology Demonstrator (JMR-TD) program, the Army has been gathering data from flying prototype designs that could fill the FLRAA role.

The Army posted a request for information (RFI) in April 2019, which was intended to identify interested manufacturers. According to the RFI, the Army plans to bring the FLRAA into service in 2030, in anticipation of retiring the UH-60 after a 50-year life.

Design goals

According to the RFI, the Army has set a per-unit cost goal of $43 million (in 2018 dollars). The Army envisions combat scenarios where a future scout helicopter being developed under the Future Attack Reconnaissance Aircraft (FARA) program and unmanned drones would control an area or corridor, which would then allow FLRAA to insert troops. FLRAA is intended to be more agile and faster than the existing UH-60.

FLRAA Requirements (April 2019)
Attribute Minimum Desired
Army USMC Army USMC
Unrefueled Combat Radius 200 nmi (370 km; 230 mi) 365 nmi (676 km; 420 mi) 300 nmi (560 km; 350 mi) 450 nmi (830 km; 520 mi)
One-way Unrefueled Radius 1,725 nmi (3,195 km; 1,985 mi) 2,440 nmi (4,520 km; 2,810 mi)
Maximum Continuous Cruise Speed 250 kn (460 km/h; 290 mph) 275 to 305 kn (509 to 565 km/h; 316 to 351 mph) 280 kn (520 km/h; 320 mph) 295 to 330 kn (546 to 611 km/h; 339 to 380 mph)
Payload (internal) Cabin floor capable of 300 lb/sq ft (1,500 kg/m2) 4,400 lb (2,000 kg) Cabin floor capable of 300 lb/sq ft (1,500 kg/m2) 5,200 lb (2,400 kg)
Passengers 12 8 12 8

Competition history

FLRAA is part of the Future Vertical Lift (FVL) program; in 2016, Major General William Gayler declared the first FVL aircraft would fill the medium-lift role. The proposed FLRAA program schedule overlaps with the FARA procurement, which is also part of FVL. FARA would provide a light-lift helicopter for the armed reconnaissance/scout role that was previously filled by the Bell OH-58 Kiowa until its retirement in 2014.

On April 4, 2019, the Army released a formal request for information and outlined its proposed schedule for FLRAA:

  • Q4FY21 (Jul–Sep 2021): Award contract
  • Q2FY23 (Jan–Mar 2023): Preliminary design review
  • Q3FY24 (Apr–Jun 2024): First flight
  • Q4FY24 (Jul–Sep 2024): Critical design review
  • Q2FY30 (Jan–Mar 2030): First unit enters service

The FVL program is headed by Brigadier General Wally Rugen; according to Rugen, based on the data gathered during JMR-TD with the Bell V-280 Valor and the Sikorsky–Boeing SB-1 Defiant, the Army was ready to move on to open competition for the FLRAA contract. In March 2020, the Army awarded competitive demonstration contracts to Bell and Sikorsky/Boeing, who will proceed to complete conceptual designs and explain how the FLRAA requirements are met by the Valor and Defiant candidate designs, respectively.

Initial candidate designs

AVX

AVX Aircraft proposed an aircraft with their coaxial rotor and twin ducted fan design that provides better steering and some additional forward power. Their JMR-TD is to be built at 75% scale. It is capable of flying at 230 kn (260 mph; 430 km/h), with 40% lift from the small forward wings and 60% from the 56-foot (17 m) rotors. Half the drag of the design comes from the fuselage and half from the rotor system, so wind tunnel tests are aiming to reduce drag by a third. The rotor system has two composite-flexbeam hubs with drag-reducing aerodynamic fairings on the blade cuffs and the mast between the hubs.

Karem

Karem Aircraft proposed to design an optimum-speed tiltrotor (OSTR), designated the TR36TD demonstrator. It would have had twin 36-foot-diameter (11 m) variable-speed rotors powered by existing turboshaft engines. The production version of the TR36D would have had a level flight speed of 360 kn (410 mph; 670 km/h). Karem says its variable-speed OSTR configuration offers advantages in weight, drive train, and aerodynamic and propulsive efficiency. It has high speed, “robust” hover performance at altitude, higher climb rate and sustained maneuverability, and longer range than other vertical-takeoff-and-landing configurations. They also say it offers reduced complexity, inherent safety advantages, simplified maintenance, and low total ownership cost. As of 2016, Karem continues to work on versions of the TR36, intending to start testing rotors around 2018.

Bell

Bell Helicopter proposed a third-generation tiltrotor design for the FVL program. Bell sought partners for financial and technological support, although the company did not require assistance. In April 2013, Bell revealed its tiltrotor design, named the Bell V-280 Valor. It is designed to have a cruise speed of 280 knots (320 mph; 520 km/h), range of 2,100 nautical miles (2,400 mi; 3,900 km), and a combat range of 500 to 800 nmi (580–920 mi; 930–1,480 km).

Sikorsky/Boeing

The SB>1 Defiant (or “SB-1”) is the Sikorsky Aircraft and Boeing entry for the program. It is a compound helicopter with rigid coaxial rotors and two Honeywell T55 engines. Its first flight took place in March 2019.

Finalist

The FVL program is headed by Brigadier General Wally Rugen; according to Rugen, based on the data gathered during JMR-TD with the Bell V-280 Valor and the Sikorsky–Boeing SB-1 Defiant, the Army was ready to move on to open competition for the FLRAA contract. In March 2020, the Army awarded competitive demonstration contracts to Bell and Sikorsky/Boeing, who will proceed to complete conceptual designs and explain how the FLRAA requirements are met by the Valor and Defiant candidate designs, respectively.

Bell V-280 Valor

The Bell V-280 Valor is a tiltrotor aircraft being developed by Bell and Lockheed Martin for the United States Army’s Future Vertical Lift (FVL) program. The aircraft was officially unveiled at the 2013 Army Aviation Association of America’s (AAAA) Annual Professional Forum and Exposition in Fort Worth, Texas. The V-280 made its first flight on 18 December 2017 in Amarillo, Texas.

Development Bell V-280 Valor

On 5 June 2013, Bell Helicopter announced that the V-280 Valor design had been selected by the US Army for the Joint Multi-Role (JMR) Technology Demonstrator (TD) phase. The JMR-TD phase is the technology demonstration precursor to Future Vertical Lift (FVL). The Army classified the offering as a Category I proposal, meaning it is a well-conceived, scientifically or technically sound proposal pertinent to program goals and objectives with applicability to Army mission needs, offered by a responsible contractor with the competent scientific and technical staff supporting resources required to achieve results. JMR-TD contracts were expected to be awarded in September 2013, with flights scheduled for 2017.

Design Bell V-280 Valor

The V-280 is reported to be designed for a cruising speed of 280 knots (320 mph; 520 km/h) (hence the name V-280), a top speed of 300 knots (350 mph; 560 km/h), a range of 2,100 nautical miles (2,400 mi; 3,900 km), and an effective combat range of 500 to 800 nmi (580 to 920 mi; 930 to 1,480 km). Expected maximum takeoff weight is around 30,000 pounds (14,000 kg). In one major difference from the earlier V-22 Osprey tiltrotor, the engines remain in place while the rotors and drive shafts tilt. A driveshaft runs through the straight wing, allowing both prop rotors to be driven by a single engine in the event of engine loss. The V-280 will have retractable landing gear, a triple-redundant fly by wire control system, and a V-tail configuration. The wings are made of a single section of carbon fiber reinforced polymer composite, reducing weight and production costs. The V-280 will have a crew of four and be capable of transporting up to 14 troops. Dual cargo hooks will give it a lift capacity to carry a 10,000 lb (4,500 kg) M777A2 Howitzer while flying at a speed of 150 knots (170 mph; 280 km/h). The fuselage is visually similar to that of the UH-60 Black Hawk medium lift helicopter. When landed, the wing is in excess of 7 ft (2.1 m) from the ground, allowing soldiers to egress easily out of two 6-foot (1.8 m) wide side doors and door gunners to have wide fields of fire. Although the initial design is a utility configuration, Bell is also working on an attack configuration.

Whether different variants of the V-280 would fill utility and attack roles or a single airframe could interchange payloads for either mission, Bell is confident the Valor tiltrotor platform can fulfill both duties; the US Marine Corps is interested in having one aircraft to replace utility and attack helicopters, but the Army, which leads the program, is not committed to the idea and wants distinct platforms for each mission. Bell and Lockheed claim an AV-280 variant can launch rockets, missiles, and even small unmanned aerial vehicles forward or aft with no rotor interference, even in forward flight and cruise modes with the rotors forward.

GE Aviation will manufacture the engines for the V-280, with the prototype (air vehicle concept demonstrator, or AVCD) using the General Electric T64. The specific engine for the model performance specification (MPS) is unknown, but has funding from the Army’s future affordable turbine engine (FATE) program. The V-tail structure and ruddervators, made by GKN, will provide high levels of maneuverability and control to the airframe. It will be made of a combination of metals and composites. Features in the interior include seats that wirelessly charge troops’ radios, night-vision goggles, and other electronic gear and windows that display three-dimensional mission maps.

Special emphasis has been placed on reducing the weight of the V-280 in comparison to the V-22, which in turn would reduce cost. To do this, composites are used extensively in the wing, fuselage, and tail. Wing skins and ribs are made of a honeycomb-stiffened “sandwich” construction with large-cell carbon cores for fewer, larger, and lighter parts. Skins and ribs are paste-bonded together to eliminate fasteners. With these measures, costs are reduced by over 30 percent compared to a scaled V-22 wing. Bell expects the V-280 to cost around the same as an AH-64E or MH-60M. While the Osprey has a higher disk loading and lower hover efficiency than a helicopter, the V-280 will have a lower disk loading, and longer wing for greater hover and cruise efficiency. As the AW609 has already performed autorotation, it is expected that the V-280 (with similar disc loading) will demonstrate the same capability.

Sikorsky–Boeing SB-1 Defiant

The Sikorsky–Boeing SB-1 Defiant (stylized as “SB>1“; company designation S-100) is the Sikorsky Aircraft and Boeing entry for the United States Army‘s Future Vertical Lift program, succeeding the Joint Multi-Role initiative. It is a compound helicopter with rigid coaxial rotors, powered by two Honeywell T55s, and made its first flight on 21 March 2019.

Development Sikorsky–Boeing SB-1 Defiant

Sikorsky Aircraft and Boeing are jointly producing a medium-lift-sized demonstrator they named SB>1 Defiant (also widely known as “SB-1”) for phase one of the program. Originally planned to fly in late 2017, its first flight was delayed in April 2017 to early 2018. Once flight testing begins, the aircraft will be evaluated by the Army for further development. Sikorsky is leading the development of phase one with an aircraft based on their previous Sikorsky X2 design.

Boeing plans to lead phase two, which is the mission systems demonstrator phase. The Boeing-Sikorsky team is seen to have an advantage with their large industrial base that may result in wider support from Congress. Their transport helicopter designs are the most-used in the Army now, and the US Army has had little interest in the tiltrotor technology in Bell’s submission.

Up to 2013, Sikorsky and partners have spent $250 million on X2 and Raider. The team and aircraft will be separate from the S-97 Raider. The team feels confident in the SB-1 Defiant and is paying for more than half of its design costs. The last project the companies teamed up for was the RAH-66 Comanche, which started in the 1980s and cost $7 billion before being cancelled in 2004. They say that factors outside their control, like budget cuts, “requirement creep”, and a long development period caused problems with the Comanche and not team dysfunctionality. Under the Comanche program, each company built different parts of the aircraft. For JMR, employees from both companies will work together. The team named the suppliers in 2015. Swift Engineering Inc. supports the program with a major portion of the airframe structure designed and manufactured at the company’s facility in San Clemente, California by an integrated team of Swift and Boeing employees.

The timeline for the first flight has slipped several times. Originally scheduled for 2017, delays arose due to a requirement to implement automated fiber placement blade manufacture at the request of the US Army. Further delays resulted in the first flight slipping past summer 2018. Dynamic systems like turboshafts, transmission, and rotors were scheduled to be tested at West Palm Beach, Florida, by the end of October 2018, before ground runs in November, then first flight to reach 200 knots (230 mph; 370 km/h) within six months.

The first prototype was unveiled in December 2018, and the first flight was pushed to sometime in early 2019. Ground runs began in January 2019; 15 hours of ground tests were needed before the first flight.

The first flight took place on 21 March 2019 at Sikorsky West Palm Beach site in Florida. In the summer of 2019, flights were suspended to address a bearing issue with the main rotor. Flight testing resumed 24 September 2019. The aircraft reached a speed of 211 knots in October 2020.

Design Sikorsky–Boeing SB-1 Defiant

Sikorsky and Boeing state the design is to have a cruise speed of 250 kn (290 mph; 460 km/h), but less range due to using the “old” T55 engine. A new engine, the Future Affordable Turbine Engine (FATE), is to meet the radius requirement of 229 nmi (264 mi; 424 km). Compared to conventional helicopters, the counter-rotating coaxial main rotors and pusher propeller offer a 100-knot (115 mph; 185 km/h) speed increase, a 60% combat radius extension, and 50% better performance in high-hot hover performance.

Sikorsky has said that the X2 design is not suitable for heavy-lift size, and instead suggests the CH-53K for heavy-lift and tiltrotor for the ultra-class. However, Sikorsky plans to build the 30,000-pound-class (14,000 kg) JMR-TD (with a cabin 50% larger than the Black Hawk) at full scale to remove doubts about the scalability of the X-2 technology.

Sikorsky–Boeing states the SB-1 will be quick and nimble, with fast acceleration and deceleration, fast side-to-side movement, and the capability to hover with the tail up and nose down. The Defiant demonstrator will be powered by the Honeywell T55, which powers the CH-47 Chinook. It will be slightly modified to better operate at slower propeller speeds, down to 85% rpm.

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