FARA: Sikorsky Touts Cutting-Edge Tech
WASHINGTON: How confident is Sikorsky in their offering for the Future Attack Reconnaissance Aircraft? The Army just picked Sikorsky and archrival Bell to build dueling FARA prototypes two weeks ago, but design work began in 2018, said Tim Malia, Sikorsky’s FARA director, and “we’ve had key suppliers under contract for a year or more,”
“We started building physical components last year,” Malia told me – not just for ground testing, he emphasized, but “many of the key components” that will go on the actual aircraft scheduled to start flight test in 2022. That work continues despite precautions to protect employees from the COVID-19 coronavirus.
(Bell told me they had physical components in ground testing, but they hadn’t yet built components to go on their actual flight-test aircraft).
“We didn’t have the funding from the government until after the downselect [in March], but we are confident in our solution,” Malia told me, “so we proceeded at [our own] risk in the design, build, and even in some cases test of those components.”
Why such haste? Why such confidence? After decades of failed programs, the Army urgently needs a new scout helicopter to fill the gap in its reconnaissance squadrons left by the retirement of the Vietnam-era OH-58 Kiowa.
Bell, which built and upgraded the Kiowa for decades, is offering a relatively traditional chopper called the Bell 360 Invictus, much of its technology borrowed from the civilian Bell 525. So the Bell 360 has a single main rotor for lift and thrust, a tail rotor for stability, and – its most visibly unusual feature – a pair of short wings for added lift at high speeds. It has a sleek, narrow airframe to minimize drag and an Auxiliary Power Unit to augment the horsepower of the Army-mandated GE ITEP engine, allowing it to meet the Army’s 180-knot (207 mph) minimum mandated speed.
Despite all these features, the Bell 360 will still be slower than its Sikorsky counterpart. But while Bell admits its technology is less radically innovative, they argue that’s a benefit, not a bug: What they call “elegance in simplicity” will make the Bell 360 cheaper to build and maintain, they say, especially in harsh frontline environments, like the old, rugged Kiowa.
Sikorsky, unsurprisingly, argues Bell’s approach is fundamentally flawed. Maybe the high-power, low-drag Bell 360 can meet the Army’s minimum requirements today, they argue, but to get there, it’s maxed out what’s aerodynamically possible for a single-main-rotor helicopter. What the Army really needs, Sikorsky says, is a new kind of aircraft that escapes the aerodynamic limits of conventional helicopters and has enough margin for growth that it can be upgraded over and over to meet new threats.
“The taxpayer isn’t going to want to spend money to solve yesterday’s problem or even today’s problem,” Malia argued. “We have to provide return on that dollar for the next three, four, five decades.”
So Sikorsky is offering a new technology called a compound helicopter, part chopper and part turboprop airplane. It combines a pair of coaxial rotors – mounted one above the other on the same mast, but spinning in opposite directions to balance torque – with a pusher propeller at the tail for high speed.
Ultra-rigid rotors and advanced vibration controls reduce wear and tear on the rotor head, eliminating a major maintenance headache on traditional choppers with wobblier rotors, Sikorsky says. And the elegant aerodynamics of the design allows for higher speed while using much lower power. The original X2 achieved 250 knots (287 mph), the heavier S-97 hit 207 knots (238 mph) before its test program refocused from raw speed to agility, and the Raider-X is projected to hit 220 knots (250 mph) – without augmenting the Army-provided ITEP engine.
“Yes, it’s newer technology, but it has that growth [potential] to be a good investment for the taxpayer for decades to come,” Malia told me.
But novelty is a double-edged sword. Precisely because it is so new, compound rotor technology has not yet been proven in frontline conditions. In fact, Sikorsky has only built four of these aircraft:
- the original, award-winning X2, now in the Smithsonian, a small 6,000-pound machine;
- a pair of S-97 Raiders, each under 12,000 lbs, one of which was totaled in flight test after a software glitch caused its rotors to collide;
- and, in cooperation with Boeing, the much bigger SB>1 Defiant, at over 30,000 lbs, now in flight test for the Army’s Future Long-Range Assault Aircraft (FLRAA) to replace the UH-60 Black Hawk.
Raider-X, as its name implies, is an upscaled version of the S-97 Raider, roughly 25 percent larger at about 14,000 lbs. The two aircraft are designed to be similar not only in their component technology but in their flight characteristics. So the surviving S-97’s flight tests are now providing extensive data to the Raider-X team as they refine their design and their computer models of how it will perform once built.
“We’ve been fortunate enough to be flying [S-97] Raider for four years,” Malia said, with another two years to come before the larger Raider-X has its first flight. True, none of the compound helicopter designs has entered mass production, he acknowledged, let alone operational service. But with three different designs having already flown in three very different size classes, combined with extensive computer modeling and ground testing, Sikorsky is confident that their FARA offering will fly right from day one.
In fact, by applying the ground test and simulation techniques refined over the years on the X2, S-97, and SB>1, Sikorsky hopes to eliminate any bugs in their design before it ever flies. The hope, Malia told me, is to move away from the traditional but laborious “fly, fix, fly” approach – where you fly the test aircraft a little, then ground it to crunch the data and fix problems, and only then fly again – to one where most flights simply prove the simulations’ predictions hold true in the real world.
With the big SB>1 and mid-size Raider-X now in competition for major Army contracts, Sikorsky has doubled down on their compound helicopter technology. In three years, when the Army picks its Future Attack Reconnaissance Aircraft, we’ll find out if their bet pays off.
Source : Link