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Bell’s advanced 360 Invictus helicopter is 75% complete and its new open tail rotor system has been installed at the company’s facility in Amarillo, Texas.
Originally designed with a canted and ducted tail rotor, Invictus’ entire tail boom structure has been reconfigured to simplify the design and rapid construction of the Bell’s pitch for the Future Attack reconnaissance aircraft. US Army.
A new photo shared by Bell shows the tandem-cockpit, single-main-rotor helicopter on its construction stand, fuselage nearly complete and tail boom attached. The company released artist renderings of the helicopter with a channeled tail and built the tail, but decided, when the plane was already half-built, to completely redesign the anti-torque system.
Keith Flail, Bell’s executive vice president for advanced vertical lift systems, said the redesign was the result of building a competitive prototype (CP) while refining the design of the ultimate FARA weapon system.
“One of the things we looked at is that we were doing a competitive prototype, and at the same time we’re iterating on a weapon system of what the [engineering and manufacturing development] the plane is going to be – the increment one plane – and the way we’re set up is to keep the connective tissue between those two so we can keep them as close as possible in terms of what we’re doing on the CP and what the weapon system will be,” Flail told reporters recently during a media trip to Texas.
When Bell rolled out the Invictus prototype helicopter concept in 2019, the focus was on the efficiency and additional lift that would be generated by its streamlined tail rotor, angled at 20 degrees to provide additional lift in the hover. . Halfway through building the prototype that will compete in a fly-off against Raider X, the company redesigned everything behind the bulkhead separating the aircraft’s body from the tail boom and replaced the shrouded rotor with a conventional open tail rotor.
“Given the pace of the program, the competitive prototype, there wasn’t the ability to optimize in certain areas in terms of weight and things like that, which you would expect because you’re trying to go so quickly,” Flail said. . “But one of the things was that as we explored the tail rotor further, we started with a ducted tail rotor and as we continued to iterate and look at holistic optimization of the aircraft, we saw from the standpoint of growth potential and maximizing our hover performance and performance increase, that moving to the open tail rotor was the right answer to give this capability to the army.
In August, Chris Gehler, Bell Vice President and 360 Invictus Program Director, explained that “the open tail provides more efficiency, and so it really came down to weight, efficiency and performance”, of the aircraft based on an Army requirement that a single General Electric T901 Improved FARA turbine engine power.
“We would get more performance and really, more future growth for the military by using the open tail,” Gehler said in an interview in August.
Alongside the construction of the actual aircraft, the Invictus main rotor gearbox, additional power unit gearbox, drive shafts and engine reduction gearbox couplings are tested at the laboratory of Training Systems Testing (DSTL) from Bell.
Designed to fly at at least 180 knots, in accordance with Army speed requirements, Invictus borrows its main rotor system from the 525 Relentless, which has flown at speeds in excess of 200 knots in test flights. The shrouded hub and rotor blades were “ported” from the 525 program, but will be scaled to fit the Invictus. Where the 525 has five blades, Invictus will have four and will not exceed the Army’s 40-foot rotor disc size limit.
Bell’s only competitor for FARA is the Sikorsky Raider X, a compound helicopter with counter-rotating coaxial main rotors and pusher propeller. That aircraft is also at least 70% complete, but Sikorsky has not released photos of its competitive prototype being built at the company’s flight test facility in West Palm Beach, Florida.