Перспективный разведывательно-ударный вертолет Армии США FARA

Facing competitors who are pushing the envelope in terms of complexity and novelty, Bell has revealed that it is taking a more conventional route to its proposal for the US Army’s Future Armed Reconnaissance Aircraft (FARA) competition: a winged helicopter called the 360 Invictus.

Currently in the preliminary design phase, the 360 Invictus is scheduled to fly by the autumn of 2022, if the US Army gives Bell a green light and funding to build the first prototype, company executives told FlightGlobal on 30 September.

Bell is competing against four other companies: AVX Aircraft, Boeing, Karem Aircraft, and Sikorsky.

The US Army is working to a rapid timeline, with a plan to develop, flight test and field its next-generation reconnaissance aircraft by 2028. It anticipates awarding two teams contracts in 2020 to build prototypes, with a fly-off competition in 2023. FARA would be a replacement for the service’s retired fleet of Bell OH-58D Kiowa Warriors.

Bell’s 360 Invictus borrows the rotor system of the 525 Relentless, a super-medium-lift commercial helicopter designed to transport up to 19 passengers and aimed at serving the oil and gas industry. The twin-engined 525, which has a fully articulated rotor with five composite blades, is still undergoing Federal Aviation Administration (FAA) certification testing.

The 360 Invictus rotor system and airframe would be significantly smaller than the 525, however. With seating for only a pilot and gunner sitting in tandem, the single-engined aircraft would have only four blades, although Bell declines to say what they will be be made from.

Its smaller size is in part meant to meet the US Army’s requirement for an aircraft with a maximum diameter of 12.2m (40ft) – a specification meant to allow the FARA to manouevre between buildings in urban battlefields.

Bell notes that the 525’s rotor system has been tested at speeds above 200kt (371km/h), though it advertises the Invitus’s speed as more than 185kt. The US Army wants FARA to have a cruise speed of at least 180kt.

“Certainly with our configuration there's opportunities to continue to mature or block upgrade the aircraft [speed], if they want more capability,” says Frank Lazzara, director of advanced vertical lift systems sales and strategy at Bell. “But, we're trying to ensure that the focus stays on the affordability and sustainability.”

The helicopter’s wing would provide up to 50% of lift when the aircraft flies at 180kt, allowing the articulating rotor to translate more power into forward movement, he adds.

“The high flapping capability is a very efficient propulsor that it is not bearing the lift load,” says Lazzara.

Designed with a combat radius of 135nm (250km) with more than 90min of time on station, the aircraft should be able to hover out of ground effect at 4,000ft at 35°C (95°F), says Bell. To reach high speeds, Bell has streamlined the 360 Invictus’s profile with internal weapons carriage, main rotor shroud, retractable landing gear and a ducted tail rotor, which is also canted. “The canted tail rotor allows for additional capability in a hover,” says Lazzara. He adds that the ducted tail rotor is also more efficient, thus saving power for the main rotor, and is safer for ground operation.

The helicopter also has a patent pending “supplemental power unit,” which the company declines to discuss in detail.

“Advanced aircraft need auxiliary power capability,” Lazzara says. “So, the team found a way to get auxiliary power on the aircraft that literally bought its way onto the aircraft by being able to contribute to the main horsepower solution in forward flight.”

The helicopter would also have a horizontal stabilizer that is controlled by a fly-by-wire flight-control system.

“In forward flight, the flight-control computers would be constantly adjusting the horizontal stabilizer, keeping the aircraft in an attitude that provides the best drag configuration,” says Lazzara.

The company says the fly-by-wire flight control system ought to reduce pilot workload and provide a path to adding autonomous flight capabilities later. Bell says the helicopter would have modular and open systems, with Collins Aerospace supplying avionics hardware and software.

Bell describes the 360 Invictus’s reliance on the 525’s rotor system as a low-risk route for the US Army, claiming that it has high technology and manufacturing readiness levels. However, the commercial 525, which was due to enter service several years ago, has been delayed a number of times and is still finishing the final stages of the FAA certification process.

Bell is also critical of more complex designs, which it says come with inherent cost. This is a veiled swipe at leading competitor Sikorsky, whose S-97 Raider co-axial compound helicopter is widely viewed as the favorite in the FARA competition. The Raider first flew in 2015 and has achieved speeds above 200kt in test flights.

“The cost of operation for VTOL aircraft typically comes down to gearboxes and blades,” says Keith Flail, vice-president of advanced vertical lift systems at Bell. “Typically, the dynamic components are the primary cost drivers on aircraft.”

Of course, Bell is also pitching the V-280 Valor tiltrotor for the US Army’s other Future Vertical Lift competition: the Future Long-Range Assault Aircraft (FLRAA) programme, which is intended to replace the UH-60 Black Hawk. The V-280 relies upon a drive shaft that rotates with its two rotor blades to transition from vertical to horizontal flight

Moreover, the V-280 has been flying since 2017 and Bell has often noted its flight time is an indication of the programme’s maturity, accumulated testing experience which inherently reduces risk to the US Army should the service contract the company to manufacturer the tiltrotor en masse at the conclusion of the FLRAA competition.

However, because the 360 Invictus is still in the preliminary design phase and not scheduled to fly before the latter part of 2022 it would start out at least six years behind the flight testing programme of the Sikrosky S-97 Raider. Despite being behind Sikorsky’s effort, Bell believes it can rapidly catch up should it start flying three years from now.

“We have a very good process to get the first flight, and then get to second flight faster, and third flight and fourth flight,” says Flail, noting that he believes streamlined digital design and manufacturing processes within Bell can help the company achieve a rapid testing tempo. He cites the Bell V-280 as an example of that tightly integrated design and manufacturing system working well.

The Bell 360 Invictus is designed as an attack helicopter with a 20mm cannon and munitions launcher that can be integrated with air-launched effects and other future weapons.

Because the US Army does not explicitly require a utility variant for FARA, Bell is not presenting its helicopter in that configuration. However, the company says the way the helicopter is laid out means it could be reconfigured to a utility version, allowing for the two variants to share parts, similar to the UH-1Y and AH-1Z, which have 85% commonality.

https://www.flightglobal.com/news/articles/analysis-bell-reveals-360-invictus-proposal-for-us-461210/

Sikorsky is emphasizing growth capability to stay ahead of evolving threats as it unveils its offering in the U.S. Army’s Future Attack Reconnaissance Aircraft (FARA) competition, the Raider-X.

The coaxial rigid-rotor compound helicopter is a development of the S-97 Raider prototype now in flight testing.

The Raider-X is about 20% larger, with a 14,000-lb. gross weight compared with 11,000 lb. for the S-97, and a 39-ft. rotor diameter compared with 34 ft. for the Raider. The Army requires a rotor diameter of no more than 40 ft. so that FARA can fly between buildings in urban combat.

The Raider-X will exceed the FARA’s threshold maximum speed of 180 kt. Sikorsky is not saying how fast it will fly, but notes the S-97 has reached 215 kt., and 207 kt. in level flight—exceeding the 205 kt. target in the Army’s initial capability document, says Tim Malia, director of Future Vertical Lift - Light.

The Army subsequently reduced the threshold maximum speed to enable a wider competition for the FARA program. But Malia says the greater speed and payload capability of Sikorsky’s X2 coaxial rigid-rotor compound configuration compared with a conventional helicopter provides growth capacity.

“We looked at a single main rotor helicopter for FARA, but it would be minimally compliant in the early 2020s. We need to be able to stay ahead of the threat into the 2030s and 2040s,” he says.

Bell is proposing a winged, single-main-rotor helicopter for FARA, while AVX Aircraft is offering a coaxial-rotor, ducted-fan compound. Boeing and Karem Aircraft have yet to unveil their concepts.

“Single main rotor will not be able to keep up. It’s already tapped out meeting the minimal FARA requirements. It does not have the ability to grow capability over time,” Malia says. “We didn’t want to pull out all the stops to be minimally compliant when we had X2 able to carry more payload and go faster.”

The Raider-X has four-blade rotors and a pusher propulsor. The coaxial rotors generate lift only on the advancing sides, eliminating retreating-blade stall and enabling higher speed. At high speed, 90% of the engine power goes to the propulsor, says Bill Fell, senior experimental test pilot. The propulsor is declutched at low speed to reduce noise.

The Raider-X closely resembles the S-97 prototype, with side-by-side seating. Compared with tandem seating, this improves crew coordination and situational awareness, Malia says. “And we can do it aerodynamically because of the robust performance inherent in X2. We are not trying to get out every last ounce of drag.”

Behind the cockpit is a large internal weapons bay. Internal carriage of missiles and unmanned aircraft—which the Army calls air-launched effects (ALE)—is a FARA requirement, but Malia says the cabin-like volume of Raider-X’s bay provides growth space for future, larger systems. “The minimum threshold works now, but what if in 2030 there is a new ALE that can be decisive, but can’t be carried?” he asks.

The Raider-X is powered by a single 3,000-shp-class General Electric T901 turboshaft—government-furnished equipment to all FARA bidders. “We do not have an additional engine to increase speed,” Malia says, referring to the supplemental power unit in Bell’s 360 Invictus. This augments power from the single T901 to give the single-main-rotor, tandem-seat Invictus a 185-kt. maximum speed.

“We use the power available and have a solid design built around it,” he says. “The T901 provides speeds out of the chute in excess of requirements and, as it improves, we can take direct benefit. We have a growth path to additional speed and payload as the T901 power increases.”

Sikorsky is using the industry-funded S-97 prototype to reduce risk for its FARA bid, conducting flight testing to validate design models and optimize the Raider-X. This includes flying new rotor blades designed to reduce drag and vibration. “We are getting exactly the results the models said,” Malia says.

With two rotor systems and a propulsor, Sikorsky is paying close attention to the Raider-X’s cost. “We have done a complete affordability analysis and design to cost. We are extremely confident we will come in under the cost goal,” he says.

Several divisions of parent company Lockheed Martin are part of Sikorsky’s FARA team, Malia says, including Aeronautics, Missiles and Fire Control and Rotary and Mission Systems. Swift Engineering will build the airframe if Sikorsky wins one of two FARA competitive prototype contracts scheduled to be awarded in March 2020. The Army flyoff is planned for 2023, with the first unit to be equipped by 2028.

“There is a critical cap in vertical lift, in attack/reconnaissance, and that gap is really impactful to the Army in the 2020s, ‘30s, ‘40s, even ‘50s. So there is a need for a long-term solution,” Malia says. “The threat is projected to evolve rapidly, so we require significant capability growth on our side to stay ahead. Raider-X can provide an asymmetric advantage in the 2030s-50s.”

http://www.thefifthcolumn.xyz/Forum/viewthread.php?tid=257&goto=search&pid=22540

Karem Aircraft is offering a high-speed compound helicopter with an actively controlled main rotor for the U.S. Army’s Future Attack Reconnaissance Aircraft (FARA) program. The company has teamed with Northrop Grumman and Raytheon to propose its AR40 design.

The AR40 is an active-rotor, winged, compound helicopter. “The hallmark feature is it can fly fast,” says Thomas Berger, Karem’s FARA program manager. “We go past the threshold requirement by about 20% and do it without any additional auxiliary propulsion on a single [General Electric] T901 engine.”

The FARA requirements set a threshold maximum speed of 180 kt., so this implies the AR40 can reach about 215 kt. The reference to auxiliary propulsion points to Bell’s FARA contender, the single-main-rotor 360 Invictus, which uses a supplemental power unit to achieve its 185-kt. maximum speed.

Founded by Predator designer Abe Karem, the company is better known for development of the Optimum Speed Tilt Rotor (OSTR). But the Army’s requirement that FARA fit within a 40-ft. box so it can fly between buildings in urban conflicts rules out a tiltrotor design.

The AR40 has a single main rotor, a wing, and unique swiveling tail rotor. This provides anti-torque control at low speed, but swivels aft to provide propulsion for higher forward speed. “This is the best design we know to attack the requirement. It has low drag and low vibration at high speed,” Berger says.

The model designation AR40 stands for “40-ft. active rotor.” In a conventional rotor, a swashplate and pitch links mechanically transmit cyclic and collective blade-pitch commands to the rotor head. In Karem’s active rotor, the blades are individually controlled by electric actuators in the hub. This allows blade pitch to be precisely controlled to maximize performance and minimize drag and vibration at high speed, Berger says.

Additionally, power for the full-authority individual blade control actuators is generated within the hub, he says, eliminating the need for slip rings to transfer electrical power to the rotating rotor.

The main rotor has three stiff, lightweight blades and a rigid, hingeless hub. The lack of a swashplate and pitch links results in a slim pylon between fuselage and rotor, reducing drag. To achieve high speed, “we reduce drag significantly and unload the rotor to the wing,” Berger says. “The swiveling tail rotor means we do not have the edgewise drag of a tail rotor. We store all the ordnance inside, stow the gun and fair the targeting turret.”

Despite the emphasis on reducing drag, the AR40 has side-by-side seating. This improves crew coordination and provides additional room behind the cockpit for mission equipment or a cabin for personnel. “It’s space for free,” he says.

While no active rotor has yet progressed beyond the R&D stage, Karem is developing the component technology under the Army’s Joint Multi Role technology demonstration (JMR TD).

Under this program, the company will ground-test a 36-ft. variable-speed rotor for its OSTR design for the Army’s planned Future Long-Range Assault (FLRAA) replacement for the Sikorsky UH-60 Black Hawk.

The OSTR uses the same active control, lightweight blade and rigid hub technology as the AR40. The JMR TD rotor “is under component test, with the integrated test next year,” Berger says. “It will directly help reduce risk for [the AR40’s] individual blade control, rigid hub, blades, etc.”

Karem has worked with the Army’s science and technology community for many years, first on Joint Heavy Lift and later on JMR TD, but is still a relative unknown and so has teamed with heavyweight partners: Northrop Grumman for airframe production and support and Raytheon for the mission system.

“Karem is the driving pioneer of the rotor and drive system.

Northrop Grumman brings full OEM production and support capability,” he says. Northrop company Scaled Composites is also involved, and will likely build the prototype if the AR40 wins one of the two competitive prototype contracts to be awarded in March.

Northrop Grumman Mission Systems will provide the avionics and cockpit integration. Raytheon will perform mission-system integration using its experience with modular open-architecture systems. “We have teamed with big OEMs who have the ability to provide managed risk,” Berger says.

In addition to competing for FARA, Karem plans to respond to the Army’s request for proposals for the two-year competitive demonstration and risk-reduction phase of the FLRAA program, proposing its TR36 OSTR. “We are participating in FLRAA,” says Bruce Tenney, director of military VTOL business development. Karem is working under a one-year extension to its JMR TD contract, which includes refining its FLRAA concept.