KAI Proposes Smaller KF-X Design
By Minseok Kim, Bradley Perrett
Source: Aviation Week & Space Technology
October 28, 2013
Credit: Korean Aerospace Industries
Korea Aerospace Industries (KAI) is pushing for South Korea to cut the technical challenges of its proposed KF-X fighter program, offering a single-engine concept that probably has a distant connection with the Lockheed Martin F-16. KAI's KFX-E design should be cheaper to develop and build than the larger proposals put forward by the Agency for Defense Development (ADD), the chief proponent of the KF-X.
Also much smaller than and more differentiated from the Lockheed Martin F-35, the KFX-E may offer the further advantage of minimizing competition from that U.S. stealth fighter. But it may have Lockheed Martin or other U.S. intellectual property in its design, exposing it to a foreign veto over sales or even development.
Seoul will probably have a foreign alternative to consider, too. Western proposals for KF-X include twin-tail developments of the F-16 and Eurofighter Typhoon, and an advanced version of the Boeing F/A-18E/F Super Hornet. Those offerings were included as technology transfer in bids for the separate F-X Phase 3 program for 60 fighters. F-X Phase 3 has been abandoned, but a successor competition will be needed, probably reviving foreign KF-X proposals.
KAI has moved from cooperation to competition with ADD. For a decade, the manufacturer was a design contractor in support of the agency. But industry officials say that at least some KAI executives have long regarded ADD's plan to develop a twin-engine Typhoon-size KF-X as too ambitious. Meanwhile, the South Korean government has repeatedly deferred launching the KF-X. If it goes ahead, it cannot enter service before the mid-2020s. Cutting costs by accepting a smaller size would probably improve the program's chances.
In July, KAI coyly published a picture of a stealthy KF-X concept related to its T-50 supersonic trainer and called KFX-E (or KF-X-E). It gave no details then and did not respond to Aviation Week's request for comment (AW&ST July 22, p. 33). But now the company has stepped up to make its case for the aircraft, arguing at an official seminar that the KFX-E would meet all air force requirements, except for being powered by just one engine.
The KFX-E turns out to be much larger than the T-50, with an empty weight of 9.3 metric tons. It is larger even than the 8.9-ton F-16, from which the T-50 is derived, but remains much smaller than ADD's two proposals, the C103 and C203, each about 11 tons empty (AW&ST April 29, p. 46).
KAI has worked out two versions of the KFX-E, one with a single fin and one with two, the latter presumably demanding more development work but reducing radar reflections. KAI has not provided for a weapons bay in the KFX-E; ADD has reserved space for a bay in its designs, though neither the C103 nor C203 would initially have one. Following a 2009 decision to downgrade the stealthiness of the KF-X, the ADD proposed first to field an aircraft whose shape would give it the makings of a low-observable fighter. Later versions would introduce features to realize that potential.
Especially in the twin-fin version, the KFX-E has many external similarities with the C103, ADD's tail-aft design. (The C203 has horizontal stabilizers forward.) This is because KAI has used the same technical studies. The leading- and trailing-edge sweep angles of the main and tail planes are the same in the KAI and ADD designs, and various edges are similarly aligned. The same inlet duct design, with a boundary layer diverter, appears to have been used. However, fuselage width and volume are noticeably smaller for the KFX-E, reflecting the lower weight of the aircraft and perhaps F-16 design roots—though it takes a keen eye, and maybe some imagination, to see much of the F-16 in KAI's drawings. At 3.63 tons, the KFX-E's internal fuel capacity is only 14% more than that of the U.S. Air Force's current F-16C Block 40.
If the KFX-E carries an external tank on its center under-fuselage hard-point, it cannot use two stations on the corners of the fuselage. Altogether, it has nine hard-points; the C103 has 10. Depending on whether the chosen engine—either the Pratt & Whitney F100 or General Electric F110—can deliver more thrust than it does in the F-16, the KFX-E will accelerate more slowly than the U.S. fighter. The bigger wing will surely generate more drag, too.
The KFX-E borrows from the light-attack version of the T-50, the FA-50 of 8 tons empty. KAI Vice President Seongseop Jang told the Sept. 26 seminar at the Jungwon air force base that the designers proposed “using existing FA-50 parts with minimum modifications for the KFX-E development.” So the KFX-E would use or adapt the FA-50's flight control, auxiliary power, electrical, environmental control and oxygen systems, as well as the landing gear.
KAI stresses that the KFX-E is not an adapted FA-50 (or T-50). This is important because South Korea cannot modify the T-50 design without U.S. authorization. At the seminar, KAI did not address legal restrictions on its proposal. But the KFX-E has probably been designed with at least close reference to the T-50 family: A telling point is that a single fin is offered as standard, while the desirable twin-fin configuration is an option. The structure for the single fin could be derived from the T-50's.
Jinsoo Cho, president of the Korean Society for Aeronautical & Space Sciences, criticizes KAI's proposal, arguing that South Korea needs an indigenously designed aircraft to avoid foreign interference in international sales and upgrades. Cho, an influential figure in South Korean aerospace policy, seems to take for granted that the KFX-E is not entirely South Korean.
The role of foreign partners in the KF-X development is still in question. Indonesia has been working with ADD on the design. Its attitude to KFX-E is unclear. Also uncertain is how South Korea can acquire technology needed for a mainly indigenous KF-X. The F-X Phase 3 bidders instead offered updates of their own aircraft.
Whichever airframe and engine are chosen for KF-X, only one set of South Korean avionics is available. Following initial production with foreign avionics, the KF-X would switch to systems developed mainly by LIG Nex1. That would include an active, electronically scanned (AESA) radar that, according to the company and ADD, will perform about as well as the Northrop Grumman APG-80. The South Korean radar has around 1,000 transmitting-and-receiving modules. Software for functions including ground-moving-target indication is already developed, while 95% of technologies related to the antenna and 75% of test-related technologies have been acquired. Foreign help will be needed in testing.
LIG Nex1 has revealed plans to develop an electro-optical targeting system similar to Northrop Grumman's Litening II targeting pod. Signal-processing techniques and a high-resolution infrared camera are ready, but the company says it lacks the capability to develop an internally mounted targeting system, such as the F-35's.
The radar warning receiver for the KF-X will be similar to those in established fighters, such as the F-16. Technologies needed for that system are ready. It will be able to detect low-probability-of-intercept radars, says LIG Nex1. But antennas will not be conformal. The electronic warfare system of the indigenously developed ALQ-200K pod will be adapted for internal installation. A digital radio-frequency memory was developed in 2012. The KF-X will have no towed decoy.
KAI's fighter design has probably not been worked to nearly the level of detail as the C103 and C203, which ADD has produced after more than a decade of study, which ramped up in the past two years. The manufacturer still has plenty of time to refine the KFX-E, however, because the government is clearly in no hurry to launch full-scale development of an indigenous fighter. Parliament is unlikely to allocate more than 10 billion won ($9.4 million) for work on the KF-X next year.
On the other hand, KAI will surely want government funding for any intensive work on its design. Not much is available, and ADD will presumably want it all. In the end, the finance ministry may not dispense all of the money.
Political opposition to the KF-X remains as strong as ever, always focused on the alternative of importing fighters. Meanwhile, President Park Geun-hye's plans for social welfare spending can only put pressure on the defense budget. In January, ADD said the life-cycle cost of the KF-X would be 23 trillion won. Exports are assumed.
KF-X Alternatives
KAI KFX-E ADD C103
Weight, empty 9.3 metric tons (20,500 lb.) 10.9 metric tons (24,000 lb.)
Weight, max. 20.9 metric tons (46,000 lb.) 24 metric tons (53,000 lb.)
Internal fuel 3.6 metric tons (8,000 lb.) 5.4 metric tons (12,000 lb.)
Span 9.8 meters (32 ft.) 10.7 meters (35.2 ft.)
Length 15.2 meters (50 ft.) 15.7 meters (51.3 ft.)
Wing area 37.1 sq. meters (400 sq. ft.) 42.7 sq. meters (460 sq. ft.)
Engine 1 X P&W F100 or GE F110 2 X EJ200 or GE F414
Hardpoints 9 10
Weapons bay None Space provided
Sources: Korea Aerospace Industries and Agency for Defense Development
Copyright © 2013, Penton
