The US Army has selected Bell’s 360 Invictus and Sikorsky’s Raider X to progress through to the second phase of its Future Attack Reconnaissance Aircraft (FARA) programme.
Phase two of the programme will see Bell and Sikorsky further mature their concept designs and develop and test airworthy prototypes ahead of a fly-off competition, which is scheduled to begin in 2024. The results of this head-to-head contest will inform the service’s selection of its next-generation light attack/reconnaissance helicopter, which is set to be first fielded in 2028.
On March 25, the service announced it had selected the Invictus and the Raider X from a pool of five potential candidates, which also comprised AVX Aircraft’s Compound Coaxial Helicopter (CCH), Boeing’s recently announced FARA concept and Karem Aircraft’s AR40.
The FARA programme falls under the US Army’s Future Vertical Lift (FVL) portfolio, which is led by the service’s Futures Command. The competition seeks to design, produce and test a prototype that will fill the capability gap caused by the retirement of the army’s Bell OH-58D Kiowa Warrior light attack/reconnaissance helicopter fleet in 2017 – a gap which is currently being covered by army AH-64D/E attack helicopters.
Although the two platforms are vying for the same contract, they both follow very different designs, as detailed below.
Bell 360 Invictus
The Invictus follows a single-rotor, blended-fuselage design and was one of the few proposals to not opt for a coaxial rotor-driven configuration. At first glance, it bears a striking resemblance to the Boeing-Sikorsky RAH-66 Comanche prototype which flew in the late 1990s. Commonalities between the two include the sleek, compound fuselage and engine intakes blended into the top of each side of the aircraft, as well as a retractable undercarriage, shrouded main rotor, internal weapons bay, forward-facing rotary cannon under the nose and a tandem-seat configuration for a pilot and weapons systems operator (WSO)/co-pilot to further reduce drag at high speeds. Unlike the Comanche, the Invictus doesn’t have stealth capabilities, instead featuring “advanced sensors, human system interface and communications to increase operational effectiveness and interoperability”, according to Bell.
The helicopter features a ducted tail rotor that’s canted to save power. Its horizontal stabilisers will help reduce drag, while a lift-sharing wing is incorporated to off-load rotor lift demand in flight, providing 50% of the aircraft’s total lift at cruising speed. This allows for what Bell says is an “optimum propulsive capability without the need for complex drive solutions”. The platform’s rotor is articulated, enabling the aircraft to fly at increased speeds while mitigating retreating blade stall, improving agility when transitioning from hover to high-speed flight. Retreating blade stall is caused when a rotor blade moving in the opposite direction to the aircraft’s overall trajectory has a low relative speed but a high angle of attack, resulting in a stall and loss of lift.
Mitch Snyder, president and CEO of Bell, said: “The selection of the Bell 360 Invictus to continue in the FARA [programme] builds on our decades-long legacy as an innovator in reconnaissance rotorcraft supporting the [manoeuvre] force… Our team has applied innovative thinking with tested technology to give the army a low-risk option to fulfil its requirements on an aggressive schedule.”
Sikorsky Raider X
Lockheed Martin subsidiary Sikorsky unveiled its FARA-CP candidate at the AUSA Annual Conference in 2019. The company claims its Raider X platform will be “game-changing” in its warfighting capabilities through the integration of technology gained through the development, testing and evaluation of its X2 experimental high-speed compound helicopter.
The Raider X shares many similarities with the X2, including a coaxial rigid main rotor and smooth, blended fuselage with retractable undercarriage. According to Sikorsky, the X2 technology also enhances level acceleration, braking and off-axis hover capabilities, while reducing platform vibration and its overall weight. The employment of Sikorsky’s Advancing Blade Concept uses two rotors spinning in opposite directions to mitigate loss of lift as it speeds up, which is an issue with traditional helicopters.
For some time now, Sikorsky has been testing and developing its S-97 Raider demonstrator – a platform which has influenced the company’s FARA-CP offering greatly, with the Raider X sharing a similar shape and characteristics. However, the Raider X will be 20% larger to accommodate the US Army’s requirement for integration of the T901-900 turboshaft. Bill Fell, a senior experimental test pilot on Sikorsky’s S-97 programme and retired army pilot, said: “Every flight we take in our S-97 Raider today reduces risk and optimises our FARA prototype.”
Fell added: “The power of X2 is game changing. It combines the best elements of low-speed helicopter performance with the cruise performance of an airplane.”
To read more analysis about the US Army’s FARA campaign and all of the five original contenders for the contract, follow the link here: ANALYSIS: FARA in Focus.