The advanced compound helicopter has been developed on the experience of the SB>1 Defiant and will face Bell’s proposal based on the V-280 Valor.
Sikorsky/Lockheed Martin and Boeing unveiled on Jan. 25, 2021, the first details about the Defiant X, the new advanced compound helicopter proposed for U.S. Army’s Future Long-Range Assault Aircraft (FLRAA) competition that will replace the UH-60 Black Hawk, as part of the bigger Future Vertical Lift (FVL) program.
The Defiant X has been developed on the experience of the SB>1 Defiant technology demonstrator and, like the demonstrator, it continues to use two rigid coaxial rotors and a pusher propeller. This technology was initially developed with the Sikorsky X2 experimental helicopter and allows the Defiant X to operate at high speeds while still maintaining good low-speed handling qualities.
In October, by using this technology, the SB>1 demonstrator achieved a speed of 211 knots in straight-and-level flight and 232 knots during a descent, using two-thirds torque on the pusher prop and two-thirds engine power, and is expected to reach speeds up to and above 250 knots. The U.S. Army explicitly requested 250 knots as the minimum top cruise speed, with 280 knots being the desired speed.
The new helicopter will reportedly have twice the range and speed of the UH-60, making it “the fastest, most maneuverable and most survivable assault helicopter in history”, according to the two companies, and “it will revolutionize the way the Army meets threats in 2035 and beyond”. The Defiant X has been designed to penetrate high-threat air defense environments while reducing exposure to enemy fire, with the high speed being its trick up the sleeve.
“Defiant X is purpose-built for a modernized Army that requires expanded reach, survivability and lethality,” said Steve Parker, vice president and general manager of Boeing Vertical Lift. “This weapon system will give Soldiers unequaled technological advantage and connectivity over adversaries in a multi-domain battle space.”
Compared to the SB>1, the new airframe has enhancements to improve aerodynamics, with a refined shape and a new angled nose, and to reduce the thermal signature, mainly with a redesigned exhaust system. Another difference that immediately catches the eye is the presence of a new front landing gear, while the main landing gear has been moved further back, essentially transforming it in a tricycle landing gear with an added tailwheel.
“We are ready to deliver unparalleled capabilities backed by proven technologies that will truly transform the Army’s mission today, with room to grow and adapt to the missions of tomorrow,” said Andy Adams, Sikorsky vice president of Future Vertical Lift. “Defiant X not only includes the transformational aircraft – a maneuverable, survivable, lethal weapon system – it also leverages Sikorsky’s and Boeing’s advanced manufacturing capabilities.”
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Sikorsky and Boeing did not provide details about the dimensions, however they said that the Defiant X will maintain the same footprint of the Black Hawk and the subsequent tight formation capability, allowing to limit the required changes in tactics, techniques, procedures, training and infrastructure. Similarly to the current UH-60 air assault capability, the Defiant X has been depicted in some renderings while performing sling-load operations with cargo and M777 155mm towed howitzers.
The Army is expected to release a request for proposal on FLRAA later this year with a contract award expected in 2022, slightly later than the initially planned Q4FY21 (July–September 2021) as scheduled in 2019. The initial schedule also foresaw a first flight of the selected helicopter in 2024 and an entry into service in 2030.
The other contender for FLRAA is Bell’s proposal based on the V-280 Valor, which adopted a tilt-rotor solution to achieve the required high-speed. The demonstrator, which flew for the first time more than one year before the SB>1 Defiant, achieved a speed of 305 knots in December 2020. In the same month, the Defiant X and the V-280 Valor were announced as the only designs able to meet all the requirements for FLRAA, effectively becoming the only two contenders in the program.
The Defiant X has also a “little brother”, the Raider X, developed for the Future Attack Reconnaissance Aircraft (FARA) program, also part of the FVL, which faces again a Bell product, the 360 Invictus. The Raider X is highly similar to the Defiant, with the same coaxial rotors and a pusher propeller technology, a similar fuselage, but smaller dimensions. FARA is intended to fill the capability gap left by the retirement of the Bell OH-58D Kiowa Warrior with initial fielding of the new helicopter by 2028.
Interest for the Future Vertical Lift program has been reported also from the United Kingdom, which signed a memorandum of understanding with the U.S. Army to exchange information, Italy, which could involve the participation of Leonardo (reportedly in talks with Lockheed Martin, which is looking for a European partner to handle European sales and share risk costs), NATO, with its Vertical Lift Joint Capability Group working on new requirements and paying close attention to FVL, and other unnamed countries.
