6th Generation Combat Aircraft

6th Gen Boeing F/A-XX

When the U.S. Air Force’s F-22 Raptor entered service in December 2005, it was hailed as the world’s first fifth-generation military aircraft. Production of the F-22 was terminated in 2011 with only 187 of the originally planned 750 operational aircraft built.
Just as the F-22 line was being shut down, deliveries of the first production models of the F-35 Lightning II Joint Strike Fighter (JSF) began. Also classified as a Gen-5 aircraft, the F-35 is planned to replace multiple aircraft in three U.S. services – the F-35A conventional takeoff/landing variant for the Air Force, the F-35B STOVL (short takeoff/vertical landing) aircraft for the Marine Corps, and the F-35C carrier-capable version for the Navy.
The F-35 also is unique in advanced military aircraft history due to eight international partners who are providing funding, technology, and production assistance. And, unlike the F-22, the F-35 will be the first stealth aircraft offered for international sale – first to the program partners, then to select U.S. allies, including Israel and Japan.
F-22 Raptor
An F-22 Raptor from the 525th Fighter Squadron takes off from Joint Base Elmendorf-Richardson, Alaska, Sept. 21, 2011. Even as the United States works to solve problems with its Gen-5 aircraft, efforts are underway to develop a Gen-6 fighter. U.S. Air Force photo by Senior Airman Christopher Gross
While both Russia and China have claimed to be building Gen-5 fighters, no other nation has one in service, and the validity of the Russian and Chinese claims remains in question.
At the same time, the two U.S. aircraft have had major problems.
The entire F-22 fleet was grounded for nearly five months in 2011 due to perceived problems with the cockpit life-support system. The Raptor began returning to duty in late September.
The F-35, meanwhile, has been plagued with program delays, cost overruns, and questions about its operational capabilities. The Marine Corps F-35B, in particular, has come under considerable fire and been threatened with cancellation if major program fixes are not implemented. By the end of 2011, both the JSF Program Office and the Marine Corps were assuring Congress and the Department of Defense (DoD) that those problems had been addressed and the STOVL variant was back on schedule.
At the same time, some of the international partners, faced with growing economic problems and forced budget cuts, were raising questions about the number of international sales the F-35 might achieve. The United Kingdom, in particular, created major concerns when the Ministry of Defense canceled the bulk of its planned buy of 150 F-35Bs, replacing them with a smaller number of F-35Cs. [Editor's note: The UK has apparently reversed its decision recently, and reaffirmed a buy of F-35Bs.]
Even as the United States continues to work out problems with its two “world’s only” Gen-5 aircraft and Russia and China continue to talk about – but have yet to truly demonstrate – their own efforts, two questions remain: What truly defines an aircraft as Gen-5 and what, then, would define future military aircraft – whether fighters, bombers, or unmanned aerial vehicles (UAVs) – as Gen-6?
The answer to the first varies somewhat, in part because a primary element when the F-22 was introduced was stealth, which the United States had successfully demonstrated in two previous aircraft – the F-117 Nighthawk “fighter” (more realistically, a ground attack aircraft) and the B-2 Spirit bomber, both classified as Gen-4. The importance of stealth became a question because the F-35 was said to lack all-aspect stealth.
By most definitions, a Gen-5 aircraft has all the capabilities of a Gen-4/4.5, plus all-aspect stealth (even when armed), Low Probability of Intercept Radar (LPIR), a high-performance airframe, advanced avionics, and highly integrated computer systems able to network with all other U.S. (and, where possible, allied) aircraft, satellites, and ground systems within the battlespace to provide the pilot with a significant advantage in situational awareness.
Added to that, with the F-22, was supercruise – the ability to maintain supersonic flight for long distances and without afterburners. The F-22 was far from the first to have supercruise, however. That honor goes to the British-built English Electric (now BAE Systems) Lightning – in 1954. The British Aircraft Corporation (BAC) Tactical Strike/Reconnaissance 2 (TSR-2 – first flight September 1964) and the Soviet Tupolev Tu-144 Charger transport aircraft (1969) were among the first specifically designed to cruise supersonically.
But the all-time record-holder for supercruise – with more supersonic flight hours than all others combined – was the Aérospatiale-BAC Concorde, a commercial jetliner that flew mostly transatlantic routes for 27 years before being retired in 2003.
F-35A AF-4 Lt. Col. Peter "Shay" Vitt Edwards AFB
F-35A AF-4, with Lt. Col Peter "Shay" Vitt at the controls during an evaluation at Edwards Air Force Base, Calif., on Sept. 29, 2011. Complete fusion of fully networked, revolutionary sensors will be necessary sixth-generation capability. Lockheed Martin photo
With only two Gen-5 aircraft in the world’s military air fleets – one now out of production, the other yet to begin full-scale production and with an initial operational capability (IOC) target ranging from 2014 to 2018 (depending on variant) – talk of a Gen-6 aircraft might seem somewhat premature. However, given that preliminary work on the F-22 began in the mid-1970s and on the F-35 in the mid-’90s, concept and initial design studies on a Gen-6 aircraft begun in early 2012 probably would not lead to a production aircraft until the mid- to late 2030s – providing it became an actual budget-item program with adequate funding for research, development, test, and evaluation.
While some question the need for even a Gen-5 fighter, if no potential adversary is likely to field one anytime soon, discussions of a Gen-6 are extremely preliminary. Nonetheless, the U.S. Air Force already has begun asking industry for ideas – largely because USAF air fleet projections show a shortfall of nearly 1,000 fighters by 2030, even if all F-35s are delivered on schedule and the F-22 continues to fly. The shortage will come from the retirement of most, if not all, legacy aircraft currently in the fleet – including those few still in limited production – most of which the F-22 and F-35 are intended to replace, but in far fewer numbers.
The problem could be far worse if Russia or China do succeed in building a Gen-5 fighter and produce them in large numbers, something both have claimed they will do, although economic problems in both nations may slow or seriously reduce those plans. While Europe, in a joint program, has or could develop the technologies required for a Gen-5 aircraft, current economic problems in the European Union – combined with significant planned defense budget cuts – make that unlikely.
In November 2010, the USAF issued a “capability request for information (CRFI)” to industry to assist an Aeronautical Systems Center look at “applicable materiel concepts and related technology for a Next Generation Tactical Aircraft (Next Gen TACAIR) capability with an initial operational capability (IOC) of approximately 2030. The envisioned system may possess enhanced capabilities in areas such as reach, persistence, survivability, net-centricity, situational awareness, human-system integration and weapons effects. It must be able to operate in the anti-access/area-denial environment that will exist in the 2030-2050 timeframe.”
A few months later, DoD issued a 30-year Aircraft Procurement Plan for the Navy and Air Force. That included a Gen-6 fighter – possibly unmanned – for the Navy, designated the Next Generation Air Dominance aircraft, as a possible Super Hornet replacement. However, it made no mention of such an aircraft for the Air Force to replace either the F-22 or the F-35A, although it did include a new long-range, nuclear-capable bomber for either manned or unmanned missions.
While then-Defense Secretary Robert M. Gates said the plan should not be seen as a blueprint for future DoD programs, it and the USAF CRFI were the most official statements to date on plans for Gen-6 aircraft. What remained unanswered was how Gen-6 would build upon – and differ from – Gen-5.
The F-35 was created as a U.S. tri-service and international aircraft in part to make it more affordable and to give all three aviation services and primary allies equivalent and fully interoperable combat and networking capabilities. One question regarding a Gen-6, then, would be whether it would follow the F-35 model or that of the F-22, which was built and is operated exclusively for and by the U.S. Air Force, with international sales forbidden by Congress.
One concept for Gen-6 is to take a page from the Army’s ground vehicles book – build a single, basic, but reconfigurable, airframe and use it for an entire family of aircraft, from fighters to bombers to UCAVs (unmanned combat air vehicles). That, presumably, also would make it easier to create multi-service or even multinational variants.
But no matter how the program may evolve in that regard, two major questions stand out: What constitutes Gen-6 – and how does it differ from Gen-5, in performance and missions?
“The real trend in combat aircraft design is that the aircraft matters less and less, so you could make an argument that a true Gen-6 platform would be one that merely is a host for far more important components and data feeds,” according to Richard Aboulafia, vice president and senior aerospace analyst at The Teal Group. “What truly makes a Gen-5 plane is smart and low-observable integration of the best sensors – on-board and off – best engines, electronic warfare, weapons, and diagnostic systems.
“So a Gen-6 would take that and run with it to the point where the aircraft itself was almost irrelevant. More of the same [as Gen-5], just superb on-board and off-board capabilities, fantastic engines that would allow it to operate efficiently at supercruise and, of course, instant awareness of every threat and friendly asset at a terrific range. And, of course, low observable. But basically, it would be an integration of components and capabilities developed by someone other than the aircraft manufacturer.”
T-50 burners
The Sukhoi T-50 appears to be an attempt to blend superior performance a measure of stealth as well as other 5th-generation features. The T-50 and Chinese J-20, should they fulfill their promise and be produced in significant numbers, would be a serious threat to U.S. plans for its future fleet. Photo courtesy of Sukhoi
Lockheed Martin, producer of both the F-22 and F-35 – and the F-117 before them – doesn’t entirely disagree, but has a slightly different take on Gen-6. And, according to Keith Tucker, director of strategic planning at Lockheed Martin Aeronautics, to truly be Gen-6 would require a lot more than improved Gen-5 components and capabilities.
“It’s time to start looking at the technologies that will provide the next quantum leap in capabilities for sixth-generation fighters – IOC 2030+ – as Gen-5 did over Gen-4,” he said. “Simply removing the pilot from an aircraft or introducing incremental improvements in signature and range does not constitute a generational leap in capability. Those kinds of improvements are already being looked at for our fifth-generation fighters.
“Next-generation fighter capabilities will be driven by game-changing technological breakthroughs in the areas of propulsion, materials, power generation, sensors, and weapons that are yet to be fully imagined. This will require another significant investment in research and development from a standpoint of both time and money.”
Aboulafia adds one more significant change: mission. The F-22 generally is considered the world’s premier air superiority fighter; the F-35 is less capable in the air superiority mission, but has always been focused on ground attack, as indicated by its original name – Joint Strike Fighter – placing it more in the realm of the F/A-18 Hornet.
For Gen-6, Aboulafia contends, the capabilities of both current Gen-5 aircraft should be merged into something the U.S. fleet currently lacks and has, he believes, largely ignored.
“For the past three decades-plus, we’ve been reflecting and defining the concepts of the tactical fighter and strategic bomber. Why not use Gen-6 capability as an opportunity to do something new? Why not a theater aircraft – neither strategic nor tactical, but a combination of the best of both worlds?” he asked. “The argument against it is ‘we tried it before and it was awful’ – but that was in the 1950s and ’60s, so why not use 21st century advanced technology this time to give Gen-6 the air-to-air combat [capability] of Gen-5, plus strike and range that makes a difference?
“Everyone talks about this being the ‘Pacific Generation’ and Australia-based, but it hasn’t really hit the aircraft designers yet. We now have these fighters and a push for a next-generation long-range strike [NGLRS] bomber, but it’s been a long time since there was anything in the middle. There just hasn’t been a lot of thinking in that direction and maybe there should be, maybe that is where Gen-6 capability could make a real difference. Most of the artists’ concepts I’ve seen basically seem to be reinventing the F-15 or F-22 – and NGLRS is just another bomber. So why not think outside the box and create something that meets changing future needs?”
Lockheed Martin Skunk Works Next-Gen Tactical Fighter
Lockheed Martin's Skunk Works' concept for a next-generation tactical fighter. While incorporating stealth features, it also appears to make concessions to outright performance such as a butterfly tail.Lockheed Martin imagery
He said some past efforts in that direction, such as the U.S. F-111 in the 1960s and the Canadian Avro Arrow in the 1950s, failed to meet the grade for a variety of reasons, giving the overall concept a bad name.
“But if you could take sixth-generation capabilities and rejuvenate that concept, you might have something – a true theater asset,” Aboulafia said.
Tucker declined to get into such specifics (it should be noted the nation’s other major military aircraft manufacturers – Boeing and Northrop Grumman – declined to comment at all for this article). He did, however, provide a generic list of factors that could be seen as supporting Aboulafia’s “it’s not the aircraft, it’s the components” argument.
“Sixth-generation aircraft requirements are not set and will depend on assessments of future threats that may emerge in the 2030 time frame,” Tucker said. “Greatly increased speed [Mach 3 supercruise or even hypersonic, according to one company study], longer range; extended loiter times; multi-spectral stealth; ubiquitous situational awareness; and self-healing structures and systems are some of the possible technologies we envision for the next generation of aircraft.”
At the same time, a Lockheed Martin Strategic Studies Group report on “Aerospace & Defense Trends 2010-2040+” also forecasts a number of “quantum leaps in capability” for Gen-5 through 2040, including:
  • unmanned variants;
  • increased range/payload;
  • low observable enhancements;
  • net-enabled operations;
  • integrated sensor fusion;
  • fighter performance; and
  • VLO (very low observable) stealth.
Some of the possibilities mentioned by Tucker for Gen-6 don’t really meet any known threats or requirements, according to Aboulafia, “but if you’re going to wait 15 to 20 years to do Gen-6, why not? You’ll have the engines by then, it helps you get in and out and improves your kinetics – the ability to kill stuff – [and] it could be used to justify it as a new aircraft separate from everything else out there. Then add to that better avionics for battle management and control.”
At the same time, he added, what trade-offs would the operators be willing to accept to incorporate some of those elements?
“If you look at the history of tactical fighter aircraft, range really hasn’t varied all that much – mostly a combat radius of 500 to 800 miles – not 2,000. So it would be great to say a combat radius of 800 to 1,000 nautical miles [nm], but it really won’t make that much of a difference,” he said. “You have to question whether we have to go back to the days of the bigger planes – such as the F-111, which was hinted at about the new regional bomber – or an F-22B or something. And maybe that’s the answer – a Gen-6 is more an F-111 with 1,500- to 2,000-nm range, but you would lose on stealth and other capabilities. On the other hand, if you are dependent on sensors and long-range weapons and such, it makes some sense.
6th Gen Boeing F/A-XX
The Boeing F/A-XX shown in this rendering is a proposed Generation 6 air superiority fighter designed to replace the F/A-18 Super Hornet for the U.S. Navy The F/A-XX would incorporate stealth capability and other features that are considered vital in future Gen-6 aircraft. Image courtesy of Boeing Company
“Actually, a Gen-6 doesn’t require full stealth, just low observability and making your sensors as passive as possible, giving the pilot as many options as possible for target tracking without using active beams, whether that is offboard sensing or some form of distributed aperture, but being able to track and destroy a target without emitting.”
Another common thread running through discussions of Gen-6 is whether it should have an on-board pilot; indeed, some have predicted the F-35 will be the last manned fighter built by the United States. Aboulafia disagrees – on that, on it being carrier-capable, and whether it should be STOVL, another frequent prediction for all future military aircraft.
“I think a Gen-6 will still be designed around a pilot, perhaps with an optional capability. It doesn’t cost that much to put a pilot in the cockpit and it gives you tremendous advantages. It also certainly will be land-based, because of increased carrier vulnerability. And a 2,000-nm plane won’t be a carrier plane any more than the F-111 was – and God knows they tried. Of course, if it is the size of an F-35, you could do both land- and sea-based, but if it really is a theater asset, it will be land-based,” he predicted. As for STOVL …
“No. Please, no. There are three ways to make STOVL happen. Two have been tried – the independent turbine, which didn’t work out, and ducted air, which worked great on the [AV-8B] Harrier, but not if you want to go supersonic. Then there is the F-35B approach, which involves an awful lot of design compromise, including substantial range and payload trade-off, which most people won’t make. The Marines will because that is how they fight a war – but that’s just the Marines. And if it is a bigger plane, forget about it.”
While the actual missions – even the size, range, and speed – that would define a Gen-6 aircraft remain the subjects of considerable debate, a few things do seem to be commonly accepted: greatly enhanced radars and self-protection, fly-by-light avionics, directed-energy weapons, revolutionary sensors with full fusion to prioritize threats and give the pilot just the information needed – when and how needed – to concentrate on fighting and surviving, which also means a far greater level of autonomy than any current aircraft.
In the end, a true Gen-6 aircraft may be platform agnostic – not a new generation of airframe, but of the component technologies that aircraft carries.
“It won’t be about the aircraft, but about all the building blocks. Whether it’s displays, electronic warfare, propulsion, sensors, munitions, datalinks – that’s where you will see the evolution. It also goes back to range and whether Gen-6 is more of a theater-ranged asset than a traditional tactical platform. Looking at emerging requirements, it comes down to the Pacific, which draws you to a bigger and more capable aircraft,” Aboulafia concluded.
“The airframers are kicking in less and less of their own cash – except when it comes to export competition. The people doing the real heavy lifting are the subsystem companies – and that is where DoD money is going. So the key question is whether these components and capabilities can be inserted into current aircraft or if it will take a new plane to package and integrate them.”
This article was first published in Defense: Review Edition 2011/2012.


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