Korea Aerospace Industries (KAI) has published a drawing of a moderately stealthy fighter concept based on its T-50 series of supersonic trainers and light-attack aircraft. The concept aircraft is far smaller and less ambitious than the all-new, twin-engine KF-X designs promoted by the Agency for Defense Development, the leading proponent of building an indigenous South Korea fighter.

Some South Korean industry officials doubt that the country has the technical resources to build the KF-X, especially if major civil aerospace programs go ahead at the same time; a 90-seat turboprop airliner is also proposed. But a KF-X derived from a current type would demand less engineering and may benefit from stronger pricing by avoiding competition with the Lockheed Martin F-35, although Saab is already in the market for advanced but moderately sized fighters with its Gripen E/F.

The T-50 and its FA-50 light fighter derivative are themselves based on the F-16 and were developed with help from Lockheed Martin, but the stealthy concept, called KF-X-E, departs from the F-16 planform used for the earlier aircraft. Some wing and fuselage edges are parallel, and the trailing edges of the main and tail planes are swept forward. The fuselage sides have chines. Nose volume of the KF-X-E appears to be small, limiting the size of the radar antenna, but the airframe seems to have more volume overall than the T-50, offering more space for internal fuel and thereby minimizing the need for external tanks and their radar reflections.

Retention of the single tail on the KF-X-E is emblematic of the limited ambition of the designers, who appear to have aimed at achieving a level of stealth above that of the Eurofighter Typhoon and Boeing F/A-18E/F Super Hornet but well below that of the Lockheed Martin F-22 and F-35. The latter two, like other stealth aircraft, have canted twin tail fins.

Similarly, the air inlets of the KF-X-E have boundary-layer diverters; recent stealth aircraft handle the boundary layer with aerodynamic shaping and no diverters. The KF-X-E may be too small for internal weapons stowage. No engine details are known, but South Korea may want to replace the T-50's General Electric F404, whose future application appears limited to the T-50 series, with another probably more powerful type. Candidates would include the GE F414 and Eurojet EJ200.

The winner of the separate F-X Phase 3 competition for 60 fighters—Lockheed Martin, Boeing or Eurofighter—is expected to support KF-X development. Each manufacturer has proposed a design. Lockheed Martin's could conceivably be similar to but a little larger than the KF-X-E by introducing stealth features into the design of the F-16. The result would still be a fighter well-differentiated from the F-35.

A key issue in developing the KF-X-E might be obtaining permission from Lockheed Martin, which presumably has intellectual property in the T-50 design or at least contractual rights to ensure that it does not become an F-16 competitor. Another obstacle is that the South Korean air force prefers twin-engine aircraft for the medium-fighter category that the KF-X would fill.

KAI did not respond to a request for further information about the KF-X-E.