Sikorsky Raider X FARA contender.
Lockheed Martin – Sikorsky
The US Army has decided.
Via a press release last night (25 March) the Project Executive Office – Aviation (PEO-Avn) announced that the field of 5 competing designs for the US Army’s Future Attack and Reconnaissance Aircraft (FARA) had been culled to just two. The Bell 360 Invictus will face off against the Sikorsky Raider X in a ‘winner takes all’ fly-off in The Fall of 2023. The winner from that fly-off can expect a lucrative contract to build hundreds of aircraft for the US Army, and quickly. Though slated for Initial Operating Capability (IOC) in 2028, the US Army has very publicly announced that they’re open to any and all suggestions of how this capability can be fielded more quickly. The ‘capability gap’ that FARA is designed to fill is extant now, and, in reality, has been ever since the Army finally retired the OH-58 Kiowa helicopter in 2017. Previous attempts to buy an ‘off the shelf’ replacement via a sole-source contract (such as the Bell ARH-70 Arapaho, based on the Bell 407 helicopter) have failed, and the palliative measure of pressing AH-64 Apache attack helicopters into the Scout role has only met with modest success, and a barrage of criticism from units forced to trade their -64s for UH-60 Black Hawks or the “Airbus EC-145 painted green” UH-72 Lakota.
Bell 360 Invictus
This ‘need for speed’ in terms of delivering aircraft may be a fundamental rationale behind the Army’s decision to down select the Bell and Sikorsky offerings. Both are far from ‘clean sheet’ designs.
Looking at the Bell Invictus first, despite its sleek and futuristic appearance, it arguably demonstrated the least technical risk of any of the 5 contenders. The Invictus looks like a ‘normal’ helicopter with the addition wings a little larger than traditionally employed for the carriage of weapons. Indeed, as many, including myself, have commented, the Bell design looks an awful lot like the abandoned Sikorsky RAH-66 Comanche; the ‘arrowhead’ fuselage shape, shrouded tail rotor and retractable undercarriage are all distinct similarities. Therefore, having flown the Comanche prototypes for hundreds of hours before final cancellation, on cost, not technical, grounds in early 2000s, the Army can be confident that the basic ‘aero’ is sound, and that some of the RAH-66 Low Observability traits may well endure. Bell have also eschewed anything complex in terms of engine/rotor/transmission systems. Instead, the Invictus will re-use a slightly modified transmission / rotor assembly from the new Bell 525 Relentless civil helicopter. The transmission and rotor are two of the highest-risk technologies in any new helicopter design and it is pragmatic of Bell to re-use known technology wherever possible – it also gives the Army confidence that many of the ‘hard yards’ have already been made in initial development.
Where Bell have diverged from the Comanche is in the large wing. Given that FARA has a fairly modest threshold speed requirement of 180kts, Bells have decided to opt for a ‘lift compounded’ design vice the more complex ‘thrust compounding’ adopted by the Raider X and other FARA contenders. Lift Compounding permits the main rotor to be off-loaded in high speed flight. This permits more power to be used to accelerate the aircraft and delays the onset of conditions such as Retreating Blade Stall as less rotor ‘pitch’ on the advancing blade is required for the same airspeed. The wing also provides a significant amount of ‘real estate’ to hang weapons, fuel and sensors off if so desired. Bell have traded the disadvantages of the wing in the hover (the rotor wash blows ‘down’ on it, reducing hover efficiency) and gambled that interference drag between the wing and fuselage at higher speeds will not be significant. The result is a technically simple design, that has significant potential for rapid certification and mass production.
The Army spoke and Bell listened.
The Sikorsky Raider X is a far more radical and high-risk design than its Bell competitor. The aircraft is a thrust-compounded coaxial design – using ‘stacked’ rotors turning in opposite directions to obviate the need for a conventional tail rotor to counteract torque and employing a thrusting ‘propulsor’ at the end of the fuselage to increase forward speed when required. At first glance this is very high risk for both Sikorsky and the US Army. No thrust-compounded helicopter has ever made it to full-rate production due to a combination of cost, complexity and vibration issues. Sikorsky has, in many ways, gone ‘all-in’ with this technology. Their co-operative venture with Boeing for the Future Long-Range Assault Aircraft project (FLRAA) designed to replace the UH-60 Black Hawk at the end of this decade, the SB>1 Defiant, uses an identical configuration to the Raider X, just scaled up. Whilst this does appear a huge gamble by both Sikorsky and the US Army, both will point to the fact that the Defiant, though late, is at last making great strides through its flight test programme, gathering vital data and that the Raider X design is an enlarged version of the S-97 Raider concept demonstrator that Sikorsky have been flying since 2015, itself developed from the Sikorsky X-2 experimental high-speed helicopter that showcased the basic technology and configuration between 2008-2011. Therefore, it can be argued that, like the Invictus, aspects of the Raider X have already flown and are therefore relatively low risk.
Sikorsky S-97 Raider Concept
The same cannot be said of the losing bids. Karem’s proposal, the AR-40, used a combination of technologies which, by themselves, were cutting edge, and together were likely too much risk for the Army. The AR40 featured a rigid main rotor and both lift and thrust compounding. A mid mounted wing was proposed to enable the rotor to be offloaded in high speed flight, a la Invictus, but in order to attempt to overcome the low speed issues, the wing was engineered to rotate through 90 degrees at low speed to minimise the downwash/wing interaction power loss. By only having a single main rotor, the AR40 required a tail rotor at low speed to counter-act the rotor’s torque. Unlike the Boeing entry, the AR40 used the same tail rotor as both anti-torque at low speed, then pivot towards the rear as speed increased to provide propulsive thrust. This high risk and complex approach, coupled with Karem’s lack of significant production experience (despite being backed by both Northrop-Grumman and Raytheon), was probably outside the Army’s comfort zone.
The same can likely be said of the L3/AVX proposal. A very ‘boxy’ design, the Compound Coaxial Helicopter (CCH) used a similar configuration to the Raider X in terms of having a coaxial main rotor design. Unlike the Raider X however, the CCH did not have a thrusting propulsor fitted on the tail. Instead, the CCH proposed a pair of mid-fuselage mounted ducted fans that could be used as both acceleration thrusting, but also reversed to provide a rapid deceleration. AVX, as a start-up, probably did not feel the US Army with confidence that they could accelerate both a trials programme nor production contract. Finally, speaking as an aviator, it was by far the least ‘sexy’ design on paper – and looks are an important part of the equation for pilots!
Which leaves the most intriguing losing bidder – Boeing.
Screenshot of the Boeing FARA proposal
Boeing’s un-named concept was ‘fashionably late’ into the competition. Where physical mock-ups and online renderings for the other contenders have been attending trade shows and appearing online for the past 6 months or so, Boeing’s entry had a ‘slow reveal’ to the public only over the past few weeks via a number of ‘teaser-trailer’ videos. Boeing’s approach was a sleek-looking thrust compounded design, using both a conventional tail rotor and a thrust propulsor. Weapons were carried on retractable stub wings, and the tandem cockpit endowed a narrow aerodynamic design. Whereas the Invictus had a distinctly ‘arrowhead’ platform, the Boeing design appears more like a high-speed fish or insect.
So why did Boeing not make the cut?
It’s not been a great few months for Boeing. The 737-Max flight control software problems has already cost the company $Bns, not helped by the subsequent revelation of software issues in their CST-100 Starliner spacecraft and unsuccessful, unmanned, orbital test. The multi-$Bn KC-46 Pegasus tanker aircraft for the USAF is experiencing a number of troubles, leading the USAF Chief of Staff, General Goldfein, to admit that he would withhold the KC-46 from front line service unless an all-out shooting war started. Even Boeing’s rotary cash-cow, the CH-47 Chinook, is sailing into choppy waters. To fund and accelerate FARA and FLRAA, the US Army is attempting to put a stop to the CH-47F ‘Block II’ programme. This controversial decision is being used as a political football, but the Army are adamant that they can cope with ‘Block I’ -47Fs for the time being as they are amongst the youngest rotorcraft in the inventory.
Boeing, however, have never successfully designed and delivered a small helicopter to the US military. They ‘inherited’ the MH-6 ‘Little Bird’ and AH-64 Apache from McDonnell Douglas Helicopters (formally Hughes) when they bought the majority of the company. Attempts to replace the UH-1 ‘Huey’ saw a loss to the Sikorsky UH-60, which effectively turned Boeing Helicopters into a Chinook business. The recent ‘win’ for the USAF ICBM force support helicopter with the MH-139 ‘Grey Wolf’ sees Boeing induct and ‘missionize’ locally produced Leonardo AW139 helicopters rather than design and field an organic platform.
With the potential slow-down in CH-47F production, and V-22 Osprey (a joint project between Bell and Boeing) also seemingly closer to the end than the beginning, there is no doubt that Boeing had industrial capacity to build the FARA in large numbers relatively quickly.
The answer, almost certainly, lies in politics and industrial strategy. Bell and Sikorsky are now the only two companies in both FLRAA and FARA (albeit Boeing do have a stake in the Defiant). It’s extremely unlikely, for both political and capacity reasons, that one company will win both competitions. However, by awarding one each, it guarantees the medium-term future of two major US helicopter manufacturers.
Cynically, Boeing is probably considered as having enough reserves and a broad enough portfolio to take the pain of not winning FARA. Bell likely needs a large government contract to make up for the denouement of V-22, UH-1 and AH-1 production, not to mention stiff competition from Leonardo and Airbus in the civil helicopter market. Sikorsky, though shielded by the Lockheed Martin Corporation, need a ‘win’ and a Return on Investment for the X2/Raider technology. The CH-53K programme is late and over budget. Ironically, their signature product, the UH-60 Black Hawk, has rebounded on them as a number of 3rd party companies are now offering overhauled and updated UH-60s at a significant discount. Whilst the S-92 continues to be a popular machine in the civil marketplace, a further, large volume military contract is essential to keeping the company going in its current form.
So, who wins what?
The simple answer is both Bell and Sikorsky win one each. My money is that the X2 technology looks very difficult to scale up for the SB>1, so I think the Bell V-280 will win the FLRAA contract having convinced the Army with mature tilt-rotor technology and a flight test programme which has met and exceeded every goal. It’s the low-risk option. For FARA, however, the manoeuvrability promised by the X2 technology, especially in an urban environment, and the relative success of the smaller scale prototypes such as the S-97, make me lean towards the Raider X – provided the US Army can swallow the increased risk.
It’ll be a couple of years before we know how cloudy my crystal ball is….