A version of this article appears in the July 28 edition of Aviation Week & Space Technology.

The South Korean armed forces have quashed an attempt by Korea Aerospace Industries (KAI) to reduce the cost and technical challenge of the proposed KF-X fighter, with the joint chiefs of staff determining that the indigenous aircraft must have two engines.

The decision raises the stakes for KF-X, the earliest prospective fighter program for Western engine and system suppliers. With a twin-engine design, the program will be ambitious and hard to launch rather than something modest with a more assured future.

South Korea’s air force is already hedging its bets by studying the possibility of importing its next batch of fighters, judging that the KF-X is not likely to go into full-scale development, according to an air force officer quoted by the Segye newspaper in May (AW&ST June 2, p. 29).

Following the chiefs’ decision, the KF-X will now need much more than the budget the finance ministry—but not the parliament—has approved. Moreover, the decision ensures that the aircraft, if built, will not be much smaller than the F-35 of intended program partner Lockheed Martin, which cannot be keen to support the creation of a competitor.

The joint chiefs of staff said on July 18 that the KF-X must have two engines, basing their decision on a study they conducted along with a think tank, the defense ministry and two of its agencies, the Defense Acquisition Program Administration (DAPA) and the Agency for Defense Development (ADD). The latter, South Korea’s military technology organization, is the leading proponent of the KF-X and especially the two-engine concepts that it has been working on for several years. KAI last year proposed a single-engine design.

The study found that the two-engine aircraft design better met the requirements of operational effectiveness, upgrade potential and industrial benefits. The single-engine design would have been cheaper and quicker to develop.

The think tank contributing to the study was the Korea Institute for Defense Analysis, which has repeatedly declared the KF-X program unviable. As part of the study, it estimated development of the twin-engine KF-X aircraft would cost 8.5 trillion won ($8.3 billion) and take 10.5 years, whereas the single-engine proposal would require 6.7 trillion won and 8.5 years. The budgetary figures were close to those that a government think tank, Kistep, estimated last year.

But the estimate for the twin-engine aircraft is higher than the 6.5 trillion won that the finance ministry has agreed to and lower than Lockheed Martin’s estimate of more than 10 trillion won. This means that the finance ministry, never a fan of the KF-X, may oppose development. It is reluctant to pay more, says the Naeil newspaper. Finance ministry opposition to the 8.5 trillion won program may persuade enough members of parliament not to fund a 2015 launch of full-scale development, which program managers are seeking.

On the other hand, parliament is strongly influenced by its committees. The defense committee under its former chairman opposed KF-X development; now that he has left, it may recommend going ahead with the aircraft. In September, the finance ministry will propose a national budget for the parliament to decide by December.

Meanwhile, the DAPA must conclude negotiations with Indonesia and Lockheed Martin and then choose the prime contractor, which will almost certainly be KAI, since it has experience in combat aircraft development.

Indonesia paid for 20% of pre-development costs and is expected to take the same share of full development. A further 20% is to be borne by industry, including Lockheed Martin, which agreed to support the KF-X in return for South Korea last year choosing the F-35A in the F-X Phase 3 fighter competition. Technology transfer will form part of, maybe most of, Lockheed Martin’s contribution.

South Korea should not have much to negotiate with Lockheed Martin, since the company’s KF-X offer was effectively accepted with the F-X Phase 3 selection. Lockheed Martin does not yet have a contract for the 40 F-35s that South Korea intends to order, but DAPA can hardly threaten to reopen the competition; the air force wants new fighters as soon as possible and the F-35, in particular.

The air force also wants a second batch of 20 F-35s but is not openly pushing for it, perhaps because doing so would put more budgetary pressure on the KF-X. Its strong preference for large aircraft helps explain the backing for ADD’s twin-engine KF-X design, which would be about the size of a Eurofighter Typhoon. KAI’s proposal was comparable with the current-production Lockheed Martin F-16. Apart from economy, it also could have eased the load on the country’s aerospace engineering resources, which industry officials say is a key concern.

If the KF-X is to have two engines, then the choice is between the Eurojet EJ200 and General Electric F414; no indigenous engine is possible, and the Klimov RD-33 and Snecma M88 seem not to have been considered. KAI’s KF-X would have needed either the GE F110 or Pratt & Whitney F100.

ADD proposes that the KF-X be developed initially with much foreign equipment, so the program offers a market for Western suppliers of such gear as radars, electronic-warfare systems, ejection seats and flight controls. South Korean equipment would progressively replace foreign systems in successive updates of the aircraft.