BAE Systems and its Global Combat Air Programme (GCAP) partners pulled off a coup of technology theatre at the Farnborough air show in July, unveiling a new design for their GCAP figher, in full-scale model form, that looked very different from any other existing or proposed aircraft. Surprises for the combat aircraft community included the aircraft’s size, much larger than the Typhoon or F-35 fighters, and a quite enormous, moderately swept delta wing.
GCAP is supposed to become the mainstay of Japan’s combat aircraft force after entering service in 2035, as well as the chief fighter of partners Britain and Italy. The stealthy aircraft is also a clear candidate as Australia’s next fighter.
What we see from the design is a long-range fighter that far better suits Pacific (and Australian) distances than aircraft now available, though it lacks extreme flight performance, which is looking ever less useful in air combat.
GCAP also has room for growth in capability.
The team at the air show did not disclose dimensions, and a journalist who produced a tape measure in the exhibit was, I am told, encouraged to leave at his earliest convenience. GCAP has been described as one-third bigger than Typhoon—roughly F-15 size, perhaps 20 metres long, but with a 50-degree swept classic delta wing spanning around 16.5 metres and having twice the area of the F-15’s.
GCAP leaders were firm that the model reflected the evolution of the design. The design has probably changed to meet changing requirements.
First macro-observation: the requirements are different from anything else. The last generation of European fighters were essentially F-16 or F/A-18-type fighters with added capabilities. South Korean and Turkish designs today, and the Shenyang FC-31, are US-inspired. Not so GCAP, formed to a Euro-Japanese requirement that edges towards the light-bomber end of the fighter spectrum, with an emphasis on payload and range, in a way we have not seen since the 1960s and the (much bigger) F-111.
The wing’s shape and size contribute to performance in two ways: massive fuel volume and low drag in cruising flight. Both promote range. It’s not a classic delta in the style of the Mirage III’s; it’s more like the capacious wing of the promising but never built F-16U, from 1995, or that of the Boeing X-32 contender for the Joint Strike Fighter program. The F-16U carried 80 percent more internal fuel than the standard aircraft; the X-32 wing, only half the area of the GCAP wing, could accommodate 9 tonnes of fuel, compared with 3.2 tonnes in the F-16C, for example.
The GCAP should have a usefully greater combat radius on internal fuel than most other current combat aircraft can manage with external tanks, while leaving space in the lower fuselage for weapons. That makes a lot of sense for a stealth aircraft, where fuel and bulky weapons must be carried internally.
Among the tactical opportunities of greater range is use of bases farther from the territory of the opponent–say, China. They would be more costly to attack with missiles and easier to defend.
The large span and area of the GCAP’s wing contribute to efficiency in cruising flight and good turn performance. The relative size of the engine inlets and exhausts and the smallness of the vertical stabilisers suggest that, to dominate the fight, the designers are not going for ultimate agility but are relying on sensors, long-range weapons and even teaming the fighter with uncrewed aircraft. (An aircraft this size could carry uncrewed vehicles into the fight under its wings, releasing them outside detection range.)
One wonders whether the European and Japanese planners have read the air combat study by researcher and former US Air Force pilot John Stillion, which pointed to a trend to longer-range engagements and declining instances of turning fights.
The wing sweep angle doesn’t seem to be optimised for supersonic cruise—supercruise. A fighter that can supercruise has much greater opportunity to make intercepts, but the feature has costs: it needs either an engine design that isn’t ideal for subsonic speed (one reason for the F-22’s non-stellar range) or one that has the complex and costly feature called ‘variable cycle’ (which has not been mentioned at all in the GCAP context).
Supercruise makes the airframe hot and therefore detectable, with a unique thermal signature that can be used to identify the aircraft. GCAP planners appreciate this: mindful of high-power radar-jamming from Soviet strike aircraft in the Cold War, the Royal Air Force was eager to get an infra-red search and track sensor (IRST) for the Typhoon. The one that’s on the Typhoon, the Leonardo Pirate, is as good as IRST gets, with a neural-net processor to filter false alarms.
Against such sensors, supercruising aircraft are not stealthy. That explains the apparent decision to forgo the capability.
Managing heat inside a fighter is a huge challenge. If it builds up faster than it can be dissipated through the skin, it can be stored for a while in the fuel. The Lockheed Martin F-35 program has struggled with this, but GCAP will try to get it right at the outset.
Engine company Rolls-Royce has demonstrated an embedded starter-generator and describes a system in which fuel and oil pumps are electrically driven and energy storage is provided for peak requirements. Meanwhile, the wing’s large surface area will help to offload heat without the skin getting too hot (and therefore too detectable).
Size and integrated energy and cooling will give GCAP room for growth. There is an interesting lesson here from the F-35. The JSF requirement was written when the Moore’s-law-driven development of electronics over two decades had vastly improved the F-16’s capabilities; it seemed clear that the development of electronic technology would continue, and it did. But what was not recognised was that, in a tightly packed and thermally sealed airframe, the limit on increased performance of electronics was not their volume and weight but getting rid of their heat. GCAP’s designers seem to have taken this to heart.
The power could be used in novel ways. There have been persistent reports of British work on high-power microwave (HPM) technology since the early 2000s. And Leonardo and the British Ministry of Defence expensively launched development of the latest radar for the Typhoon without foreign cooperation. A radar antenna could become an HPM weapon—and now Rolls-Royce says GCAP needs generators with the extraordinary output of around 2 megawatts. All that seems to add up to GCAP using HPM.
HPM attack can disrupt or damage radio-frequency systems—sensors and communications. HPM systems have challenges, including a risk of damaging friendly aircraft, but if they can be made to work they could be a powerful weapon for suppressing ground defences.
GCAP is different, better adapted to the Pacific than shorter-range jets, and has growth potential. As the largest Europe–Asia joint defense project and a major technological advance for all parties, the program faces challenges. But the design seen at Farnborough suggests that the requirement has been well thought through. It’s a promising start.