The Raider Rises

Is a bird in hand really worth two in the bush? Sikorsky Helicopters and its parent, Lockheed Martin, certainly are betting that way.

They’re wagering heavily that their 2010 Collier Trophy–winning X2 rigid coaxial compound helicopter design, flying since May 2015 aboard their S-97 Raider technology demonstrator, will be worth more to the US Army than two (actually up to five) other unconventional but not-yet-flying aircraft that competitors may offer the army.

The Future of Attack Reconnaissance Aircraft

The US Army, by far the world’s biggest operator of helicopters, has set up a preliminary competition aimed at deciding sometime next summer which technological paths it will compare between now and 2023. That is when it expects to decide what company will build the army’s next-generation future attack reconnaissance aircraft, and what technology that aircraft will feature.

The future attack reconnaissance aircraft, or FARA in US Army acquisition parlance, is one of two, and perhaps eventually three, classes of vertical-lift vehicles the army wants to buy over the next 20 years to replace potentially all 4,000 aircraft in its current vertical-lift fleet.

In one form or another, army planners and procurement leaders have been working on the replacement for its rotary fleet since at least 2004, and really since the early 1990s. It has been a frustrating process that has seen the cancellation of at least three different programs amid concerns about costs, funding sources, competition with other large procurement programs, and indecision among army leaders over what their future missions and tactics, and thus, what their future equipment requirements will be.

Over most of the last five years, the biggest—and some of the smaller—US helicopter manufacturers have been working under the assumption that the army most wanted a longer range, faster, more fuel-efficient troop transport and utility helicopter to replace its workhorse fleet of more than 2,000 Sikorsky UH-60 Black Hawks. But within the last year the army has made it clear that, while the Black Hawk replacement aircraft remains the biggest and most important item on its aviation wish list, the smaller FARA aircraft has been moved to the top of that list because it is most urgently needed.

The Army has been without a true armed scout aircraft since the last of the Bell OH-58 Kiowa Warriors was retired in mid-2017. Some aspects of the armed scout mission were assumed by Boeing AH-64 Apache attack helicopters, and some by drones. But that shift always was meant to be temporary, in large part because the Apache is too large, too expensive to acquire, and hugely expensive to operate in the scout role, for which it is not optimized. The shift to that aircraft also adds significantly to the already heavy maintenance demands on the Apache fleet and on Apache pilots.

So now the army is moving with the kind of development speed not seen since World War II to determine what kind of vertical-lift vehicle it will need to fill the FARA role. In a tentative timeline laid out last summer, the army hopes to begin fielding that aircraft by the early 2030s, perhaps even a bit earlier.

Initial award of preliminary design contracts to as many as six manufacturers is expected in June 2019. Approximately nine months later, the army plans to award two of those competitors contracts to build and test prototypes. A fly-off is planned to commence in the fall of 2022 (the first quarter of the government’s fiscal 2023).

But the selection of a winner to actually build the FARA is not guaranteed to follow immediately after the fly-off. The plan leaves room for the army to delay that decision, either to allow for more technology advancement or, more politically, to allow Congress and the administration more time to wedge the program into the defense budget.
However, neither the army’s short-term rush to get to a FARA fly-off in just four years, nor the political and funding uncertainty surrounding its fast-track FARA development plan, detracts from how impressive the S-97 and its underlying technology already are.

Sikorsky engineers expect the Raider to eventually reach speeds of more than 220 knots, or about 255 mph.

Sikorsky Pursues Two Big Wins

Make no mistake, the Raider and the derivative aircraft that’ll be built to win that fly-off will have to be pretty darn impressive for Sikorsky to reach its ultimate goal with its X2 compound helicopter technology, and for Lockheed to get the maximum reward for its decision to buy Sikorsky from United Technologies for nearly $9 billion in 2015. Clearly, Sikorsky and Lockheed leaders are focused on grabbing two big brass rings in the army’s Future Vertical Lift (FVL) aircraft procurement extravaganza, not just one.

The first one, obviously, is defeating the FARA competition—probably Bell—in the relative short term and converting that technology into an enormous contract to build 400 to 500 units of this nation’s next light observation and attack aircraft. That aircraft can be expected to serve deep into the second half of the 21st century. The second brass ring for which Sikorsky is reaching would be to win the slower moving but already underway competition to build the long-range assault vertical-lift aircraft that eventually would replace the Black Hawk.

The S-97 Raider’s mere existence and the strong flight-test record it already is building clearly puts Sikorsky in the lead in the FARA competition. But the Raider’s big brother, the Sikorsky/Boeing SB>1 Defiant, is believed by analysts to be at least a year behind rival Bell’s V-280 Valor tilt-rotor entry in the Black Hawk replacement derby. Sikorsky leaders, however, obviously are hoping that an impressive showing in the FARA fly-off competition using the same X2 technology that will also be at the core of the SB>1 Defiant will go a long way toward Sikorsky closing the gap with Bell in the long-range assault aircraft competition.

To be sure, the Raider, as configured today, will not be Sikorsky’s entrant into the FARA sweepstakes. But that entrant won’t be much different: a little larger, perhaps a smidgen faster and, once armed with the weapons and all the high-tech electronic gear the Army wants its new scout attack helicopter to carry, a lot more effective in battle.

Those military upgrades from the current Raider demonstrator will be worth exploring in minute detail in the years ahead. But even now, as currently constituted without all the radars and communication equipment needed for the scout mission and without the guns and missiles it’ll also carry, the Raider is an impressive vehicle.

“The army has two capability gaps,” says Tim Malia, director of Future Vertical Lift Light at Sikorsky. “One is how will they do the attack/recon mission against future threats. The other is how will they do long-range assaults. They both come up in the Future Vertical Lift program, but I don’t see them competing against each other [for congressional funding]. They’re complementary.”

Accordingly, while Sikorsky officials downplay the connection or potential connection between the two FVL program competitions—the scout/attack (FARA) aircraft and the long-range assault/utility (Black Hawk replacement) aircraft—the company clearly views this as an opportunity to use one technology package, the X2 compound helicopter technology, to win two major procurement competitions.

The Raider is based on the award-winning Sikorsky X-2 platform, which used a rigid coaxial rotor design and a pusher propeller to achieve speeds of 250 knots in level flight.

Advancing Helicopter Technology

Sikorsky believes its experience, first with the X2 demonstrator and more recently with the Raider, gives it a huge head start. Each of the factors that the army has asked competitors in the FVL competitions to address with the aircraft they will enter already were being addressed by the S-97 Raider—before the army issued those requirements.

Speed, fuel efficiency, maneuverability, noise signature, and physical size are all key elements in the army’s decision criteria for its new scout/attack FARA vertical-lift aircraft, along with, of course, purchase price and operating costs. Commonality, or the lack thereof, with other army aircraft also eventually could factor into the FARA decision. Hence Sikorsky leaders’ quiet eagerness to win that fly-off as a means of boosting the SB>1 Defiant’s chances of winning the Black Hawk replacement aircraft competition later on.

“Speed is increasingly important in the modern battlefield,” Malia says. “The enemy’s ability to keep us based further away from the fight by their use of regular weapons—think mortars—means our warfighters have to transit farther distances to get to the fight. So the aircraft has to have the range to go that far. And its speed becomes more relevant in order to make up the time lost by having to cover more ground to reach the fight.
“The second element of speed is when your guys get into a rapid­response situation and ground troops are being threatened by the enemy. You’ve got that ‘golden hour’—or less, usually a lot less—to get there and protect those troops.

“And the third element of speed is survivability. It’s just harder to hit something that’s moving fast,” he says. “And our X2 technology meets the speed requirement very well, whether we’re talking about the scout/attack mission or the long-range assault mission.”

Chris Van Buiten, vice president of innovations at Sikorsky, says the company long has recognized that speed and range, the helicopter’s natural limiting factors, eventually would have to be addressed by manufacturers.

“Something like 10 years back, maybe more, Sikorsky realized that some of our customers’ requirements, both commercial and military, were going to start calling for greater range and speed. And we’ve always had an internal interest in improving the noise level issue and maneuverability,” Van Buiten says. In attempting to address these issues, he says, “We looked at a lot of concepts and just gravitated toward this concept.”

Forty years ago, Sikorsky studied an advancing blade concept, which relies on two sets of rigid rotor blades mounted coaxially, one on top of the other, to counteract the inherent helicopter problem of the retreating blade, which moves in the opposite direction of the vehicle’s flight path, losing lift and speed. In flight tests in the late 1970s and early 1980s, Sikorsky’s XH-59A test vehicle—an advancing blade demonstrator augmented by two jet engines mounted on its sides—hit speeds of more than 300 mph in shallow dives. In straight and level flight, it topped out above 250 mph. Those are speeds no conventional helicopter can hope to achieve because of the retreating blade effect.

“Because it had a rotor, it could do everything a helicopter could do, but [the XH] doubled the speed,” Van Buiten explains.

However, the XH-59A was too heavy, too fuel inefficient, and too expensive to operate back in those days. It also was more than a handful for two pilots to fly, in part because of significant vibrations, an inherent characteristic of coaxial helicopter designs. Beyond that, no one in the military at that time seemed to have an appetite for taking on such a difficult and risky new technology.

In the mid-2000s, Sikorsky returned to the concept again with the development of the X2, this time pairing the advancing blade technology with an advanced pusher propeller called a propulsar. The X2 demonstrator also featured fly-by-wire flight control technology, lighter composite materials and a lot less steel and aluminum, and more advanced vibration control systems that took advantage of computer processors and software that had not been invented back in the XH-59A’s days. The propulsar installed in the tail—which also was not present in the XH-59A—proved capable of pushing the aircraft forward for prolonged periods at speeds approaching 300 mph, roughly twice the top speed of a conventional helicopter.

In 2013, two years after the X2’s retirement, the first S-97 Raider began its test-flight regime. While its speed performance and many other characteristics were excellent, it too 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 achievements, 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 technology 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. The 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 the propulsar. That can push the aircraft through the air at well over 200 knots.

That’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 vertical-lift aircraft. Those 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.

Changing the Game

And there’s more to the FVL program than the Army’s need for more speed.

Though 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.’ That’s the army’s term,” Malia explains. “The idea is to use the most appropriate piloting approach for each mission.”

The 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-making 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. The “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 undertaken 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 Raider that the company likely will enter into the scout/attack fly-off will be able to operate freely, or perhaps even at all within the battle environment in major cities that the army calls “urban canyons.” That’s where military planners expect future scout and attack helicopters will be obliged to operate more and more in future conflicts.

Van Buiten says combining new or recently advanced technologies to create a new, more capable war-fighting machine that represents a major leap forward in fighting capability simply was not possible until now. “It’s an opportunity to give the warfighter a new configuration and a new capability that probably only comes around every 40 or 50 years. That’s why we had to build the Raider,” he says.

To a degree, the noise reduction, physical footprint, maneuverability, maintainability, speed, and range performance improvements that are inherent in X2/Raider-type aircraft could make commercial versions of such aircraft big hits with some corporate and medical vertical-lift operators and, in some cases, with police and other safety agencies that currently operate conventional helicopters.

Malia jokes that during a few flight demonstrations the noise from the Raider’s swirling props and engines was drowned out by a neighbor mowing his lawn near the flight observation area.

“The X2’s acoustic benefits will allow it to easily achieve the most stringent regulatory requirements,” when they eventually make their way into commercial vertical-lift aircraft, says Bill Fell, Sikorsky’s chief Raider test pilot. “This is great news if you are flying into the Wall Street Heliport, any hospital roof, or anywhere you want to make the locals happy.

“The use of the prop on any approach will allow the pilot to decelerate nose down via negative thrust on the prop. This has huge safety benefits by providing the pilot to see out in front of them throughout the approach and landing compared to the typical nose-up helicopter deceleration,” says Fell. “Think of the EMS operator landing somewhere they have never landed that is surrounded by wires; that nose-down attitude is huge.”

The X2 could change how and when we use helicopters, says Fell. “The lift/drag benefit of X2 over standard rotorcraft combined with the speed capability significantly expands the range where it makes time and economic sense to take an X2.”