UCLASS

Further, recent reports have suggested that air-to-air refuelling of manned combat aircraft may also become a requirement for UCLASS.

Thus the variety of missions and the fuel capacity required for them suggests UCLASS will be a large aircraft, certainly much larger than the Northrop Grumman X-47B UCAS-D demonstrator that has successfully demonstrated unmanned carrier operations in the past two years.

UCAS

The X-47B evolved from the original joint USAF/USN Joint Unmanned Combat Air System (J-UCAS) program to develop a common unmanned air combat demonstrator. Initially managed by the US Defense Advanced Research Projects Agency (DARPA) butlater handed over to a joint service project office, two companies built and submitted single jet-engined demonstrators for J-UCAS after receiving grants in mid-2000, with Boeing developing the X-45A, and Northrop Grumman the X-47A Pegasus.

The X-45A was developed from Boeing’s ‘Bird of Prey’ concept aircraft which flew at the Groom Lake test site in the 1990s, and featured a centre body fuselage, triangular upper forward fuselage intake, flattened engine exhaust, and highly-swept lambda wings. The X-47A was designed by Burt Rutan’s Scaled Composites (which is now owned by Northrop Grumman), and featured a more radical arrowhead-shaped blended wing-body in plan, a narrow slit intake and a more conventional round engine exhaust.

Both aircraft flew in 2003, and both flew successful flight test campaigns. In 2005 J-UCAS was terminated after the USAF’s new long-range bomber program was initiated, but the Navy re-structured its program to form the Navy Unmanned Combat Air System (N-UCAS) program.

For N-UCAS, Boeing offered its X-45N concept and Northrop Grumman its X-47B, both of which were essentially larger and more advanced versions of their J-UCAS demonstrators. The contract for N-UCAS was awarded to Northrop Grumman, and while Boeing didn’t proceed with the X-45N it instead developed it further into the company-funded Phantom Ray UCAS demonstrator.

X-47B

The X-47B is shorter than an F/A-18E but has a wider wingspan, and weighs about half that of a Super Hornet. Resembling a mini B-2 – which is hardly surprising considering its lineage – the X-47B has an arrowhead-shaped fuselage tapering to foldable stub wings, an upper forward fuselage intake, a flattened engine exhaust, and no vertical control surfaces. The subsonic X-47B is powered by a single P&W F100 turbofan without an afterburner, and has an unrefuelled range of nearly 3,900km and a demonstrated endurance of more than six hours.

The N-UCAS program was renamed as Unmanned Combat Air System – Demonstrator (UCAS-D) shortly before the first of two X-47Bs first flew in February 2011. These two aircraft were scheduled to conduct a three-year flight test campaign at Edwards AFB and NAS Patuxent River which would culminate in a series of aircraft carrier trials, but the planned50-flight preliminary test campaign at Edwards was cut short after just 16 flights because the aircraft proved to be far more stable and consistent and was able to demonstrate the required flight envelope much earlier than expected.

Flight testing at Patuxent River included land-based catapult and arrested landing trials, electromagnetic interference testing, and electronic warfare compatibility testing. The first aircraft carrier compatibility testing was conducted onboard the USS Harry Truman in November 2012, during which an X-47B was hoisted by crane onto the vessel for deck, aircraft lift, hangar bay, jet wash, and basic maintenance operations testing.

The first carrier catapult launch was conducted from the USS George H W Bush in May 2013, and after a series of precision touch and go ‘bolters’ in May and June, the first successful carrier ‘trap’ was conducted on the Bush in July. Anecdotal reports say the X-47B’sbolters and traps were so precise that it was actually wearing a spot on the carrier’s deck coating, so it became necessary to add a small variance into the landing system.

After the initial sea trials during which the Navy had only initially planned to demonstrate one successful carrier trap, the two demonstrators were due to be retired. But a late reprieve in 2013 saw an extra two years added to the program during which three more carrier deployments are planned in addition to air-to-air refuelling trials, and possibly weapons testing.

UCLASS

While the X-47B program was underway, the US Navy has been refining its UCLASS requirement. Unlike the familiar General Atomics MQ-1 Predator and MQ-9 Reaper UAVs which can carry laser and GPS-guided bombs and Hellfire missiles, future UCAVs may be required to operate in contested airspace such as the multi-layered anti-access/area denial (A2/AD) defence environments being built up by nations such as China and Russia.

As such, a future UCAV will need to have built-in low-observable characteristics such as shaping, coatings, suppression of its engine exhaust, internal weapons bays, and low probability of intercept sensors and datalinks in order to minimise its signature in the electronic and visual spectrums.

While the X-47B demonstrates some of these characteristics, particularly in its blended wing-body shaping, the two demonstrators are rudimentary aircraft only and do not have coatings or any combat-relevant sensors on board.

The UCLASS program is tasked with adopting many of the concepts so ably demonstrated by the UCAS-D X-47B, in particular the precision landing system, redundancy of automated systems,

As we go downrange, we don’t even know how we’re going to use UCLASS. RADM WINTER

and aircraft carrier compatibility, and evolving these into an operational air combat capability.

“All of that is getting wrapped up into a draft RFP that we will be submitting to industry before the end of April,” RADM Mat Winter, Naval Air Systems Command’s program executive officer for unmanned aviation and strike weapons told media at the Navy League’s Sea, Air and Space 2014 exposition on April 8. “We have one more senior leadership review that’s scheduled to be (conducted) very shortly. ” Four companies were contracted to a preliminary design review process that has informed the draft RFT, these being Northrop Grumman, General Atomics, Boeing and Lockheed Martin. “The draft RFP will be classified,” RADM Winter said, adding that the RFP “will be targeted to the industry partners that are on the PDR contracts. ” Winter added that a final RFP is likely to be issued in the northern summer, and that the winning tender will be announced in early 2015. “2020 is the expected, what we call, early operational capability of the UCLASS system,” Winter added.

While this operational timetable may appear somewhat ambitious when compared to current combat aircraft programs which are taking a decade or more to field, it should be noted that much of the development risk associated with UCLASS such as carrier trials, systems redundancy and some weapons testing has already been proven through the three previous and ongoing iterations of the UCAS program. It is also generally considered to be easier to maintain cost and schedule targets when a program is conducted in a classified and compartmentalised environment such as that planned for UCLASS.

It is likely Northrop Grumman will offer a development of its X-47B, while General Atomics has long touted the potential of its jet-powered Avenger or Predator C UCAV, development examples of which were reportedly ordered in May 2011 and have been trialled in Afghanistan under a USAF contract. Boeing will likely offer a development of its X-45B/Phantom Ray concept which made its first flight at Edwards AFB in April 2011, while Lockheed Martin has published images of a swept wing blended wing-body design which it says utilises many of the technologies developed for the F-35C and its RQ-170 Sentinel UAS.

All four contractors have a strong heritage in this field. Northrop Grumman has successfully demonstrated the capabilities of its X-47B and also has other successful unmanned systems such as the Global Hawk, Fire Scout and the rumoured RQ-180 in its stable; General Atomics has delivered hundreds of the proven Predator/Reaper/Grey Eagle series of UASs and has fielded limited numbers of Avengers; Boeing successfully demonstrated its X-45A during J-UCAS and developed and flew the Phantom Ray to further develop the technology and reduce risk; and Lockheed Martin through its famed Skunk Works division has developed and/or fielded the Darkstar, Polecat, Sentinel and reportedly ‘other’ unmanned systems in the past two decades, and can further reduce risk by using F-35-common sensors and components.

There has been a drawn out debate within the US Navy community about how stealthy the UCLASS will need to be, with the inevitable cost versus capability trade-offs being made as the draft RFP developed. Some missions such as persistent ISR and deep strike require a much more robust level of low observability than those of ‘light strike’, stand-off weapons shooter, or tanker. Itgoes without saying that stealth and cost go hand-in-hand, both in development and ongoing support. Other considerations will be the use of readily available components and systems from other aircraft programs, such as landing gear, engines and sensors, while the aircraft’s weapons and sensor payload requirements will also dictate aircraft size and affect cost.

Therefore, Navy sources indicate the initial main emphasis for UCLASS will be for it to be able to provide two ISR ‘orbits’ from a carrier on a 24/7 basis, with secondary light strike and tanking missions to also be available. Then, as the platform and the Navy’s concept of operations for UCLASS matures, a follow-on requirement may be issued for a deeper strike and persistent ISR capability at a later date.

The tanker requirement has only emerged recently, with concerns being raised that up to a quarter of a carrier air wing’s Super Hornets are regularly being dedicated torefuelling tasks in support of long-range strike or onboard recovery operations. While a vital one, this task not only takes away a large percentage of aircraft available for air combat operations, but is also eating away at the Super Hornet fleet’s fatigue life faster than expected due to the strain of the airframes launching and recovering with up to ‘five wet’ auxiliary tanks and a refuelling pod.

Other requirements expected to feature heavily in the UCLASS RFP include an open architecture and a flexible growth path in order to enable new missions to be added as the platform matures. “As we go downrange, we don’t even know how we’re going to use UCLASS,” RADM Winter said. “We don’t know exactly how we’re going to operate it because we’ve never had such a capability in our carrier environment. ” Just how UCLASS will complement manned aircraft such as the Super Hornet and the F-35C remains to be seen, and one suspects this will be another of thoseoperational concepts that will evolve over a long period.

One other consideration is that the Navy and Marine Corps currently has a requirement for up to 500 F-35Cs to replace classic Hornets and early Block I Super Hornets, and to complement Block II Super Hornets and EA-18G Growlers. But with a planned service entry for the F-35C recently slipping to 2020 and as many as 33 aircraft pushed back a few years in the FY15 budget proposal, the Navy will be inducting the F-35C and the UCLASS concurrently. Therefore, it can be reasonably assumed that if UCLASS is able to meet its ambitious capability and cost targets, that it puts at risk the planned buy numbers of the F-35C due to ongoing funding pressures and likely mission overlap in the penetration and ISR roles.

Many thanks to Dave Majumdar from the US Naval Institute for his contribution to this article.