the propulsar. Tat can push the aircraft through the air at well over 200 knots. Tat’s impressive, but still slower than the speed rival
Bell can achieve with its tilt-rotor aircraft like the V-22 Osprey and the V-280 that it plans to field in competition with the SB>1 Defiant in the long-range attack vertical-lift aircraft competition. Malia concedes that tilt-rotor technology has a top-end
speed advantage over X2-style compound helicopters and may be slightly more fuel efficient as well. But he discounts that speed and fuel disadvantage because X2 technology will make the Sikorsky entrant plenty fast enough and with sufficient fuel efficiency to meet the army’s speed and operating costs requirements for a new scout/attack ver- tical-lift aircraft. Tose disadvantages, he says, will be minimal because they only show up when the vehicles are flown at high speeds over long distances, something scout/ attack helicopters won’t be asked to do very much.
Sikorsky engineers
expect the Raider to eventually reach
speeds of more than 220 knots, or about 255 mph.
initially proved to be a high-workload aircraft for its pilots. But over the next two years Sikorsky engineers worked on solving those and other technical issues and made it possible for the Raider to return to its flight-testing program early in 2018. Since then, the aircraft has pushed through the 200-knot (230 mph) barrier in route to its eventual goal of more than 220 knots, or about 255 mph “One of the neat things about the Raider or X2 is that when you walk around it, you realize that’s really a set of recognizable technologies, just combined in a new way,” Van Buiten says. Clearly the army took notice of the X2’s speed achieve-
ments, along with the successes that the US Marines were having with the large, fast, and long-range Bell Boeing V-22 Osprey tilt-rotor troop transport. Sensing that the tech- nology had advanced far enough to consider using in army aircraft and recognizing that its fleet of more than 4,000 conventional helicopters will need to be replaced over the next two decades, the army launched its FVL technology development and procurement program. Malia’s emphasis on the need for speed in the army’s
FVL aircraft is understandable. Speed long has been the biggest limiting factor on rotary flight, especially in a military context. Te retreating blade issue limits conventional military helicopters to flight speeds of around only 130 knots, or about 150 mph. Vertical-lift aircraft built in a X2 compound helicopter configuration with a pusher prop like the Raider can exceed that barrier with ease because once they are airborne and out of ground effect, they can redirect as much as 90 percent of their engines’ power to
34 ROTOR WINTER 2019
Changing the Game And there’s more to the FVL program than the Army’s need for more speed. Tough it’s not ready yet, S-97 project leaders are hyping
the ease with which they think the Raider’s eventual scout/ attack derivative will be able to shift from being flown by two pilots in a complex battlefield environment where human redundancy is critical to mission success, to being flown by just one pilot or autonomously, based on mission requirements. “We call it ‘optimally piloted, not ‘optionally piloted.’
Tat’s the army’s term,” Malia explains. “Te idea is to use the most appropriate piloting approach for each mission.” Te concept involves using highly trained human pilots
to fly missions that require not only their piloting expertise but also their observation and critical mission decision-mak- ing experience and skills. More mundane, less risky missions then could be handled by a single pilot supported by onboard automation or eventually flown fully autonomously. Te “optimally piloted” capability also would give commanders the option of using autonomous flight technology to perform a scout/attack mission that otherwise would not be under- taken because it would be, in effect, assigning human pilots to a suicide mission. Meanwhile, Sikorsky leaders insist that its X2-style entry
in the FARA fly-off will be much quieter, have a much smaller “physical footprint,” be more easily and cheaply maintained, and be more maneuverable than tilt-rotors, which sport two huge, side-by-side prop/blade arrangements at the end of their short, conventional fixed wings. Sikorsky leaders believe that only the slightly larger derivative of the
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