KF-21's fourth prototype makes successful test flight

The two-seat fourth prototype of the Korea-developed KF-21 fighter jet makes a successful test flight Monday from the Air Force's 3rd Flying Training Wing in Sacheon, South Gyeongsang. [DAPA]

The fourth prototype of the Korean-made KF-21 fighter jet made a successful test flight Monday, signaling further progress in the country's advanced supersonic jet development project.

The Defense Acquisition Program Administration (DAPA) said that the prototype, the first two-seater model tested, took off from the Air Force's 3rd Flying Training Wing in Sacheon, South Gyeongsang, at 11:19 a.m. and landed at 11:53 a.m., successfully completing a 34-minute flight.

Unlike the previous three KF-21 prototypes which were single seated, the fourth is a two-seat aircraft with a cockpit divided into front and rear seats, allowing for two pilots, according to DAPA.

The KF-21, also known as Boramae, is a 4.5th-generation fighter developed by Korea Aerospace Industries (KAI), the country's sole aircraft maker, with funding from Korea and Indonesia. The 8.8 trillion-won project ($6.8 billion) to build Korea's first domestically developed advanced fighter jet began in 2015 to replace the country's aging F-4 and F-5 jets.

The first KF-21 prototype made its maiden test flight on July 19, 2022.

In January, a KF-21 prototype achieved supersonic speed in a test flight for the first time, reaching Mach 1, or 1,224 kilometers per hour.

Over the past seven months since the first test flight, the initial three prototypes have made more than 110 flights.

The fourth prototype will be used for missions to check differences from the single-seat models and test the performance of an advanced active electronically scanned array (AESA) radar system, according to DAPA.

Because Monday's flight was to check flight stability, it was flown with only one pilot on board.

As the cockpit was added near the front of the fuselage, the fuel tank space was partially modified, but the rest is the same as the single-seat prototypes.

The two-seat model is to be used largely to train pilots, according to DAPA. The sixth prototype is also double seated.

The DAPA will begin conducting test flights for the fifth and sixth prototypes in the first half of this year to evaluate their performance and plans to conduct some 2,000 sorties by February 2026, during the first phase of the project.

The KF-21 is a twin-engine multirole fighter equipped with stealth technology, according to the KAI, measuring 16.9 meters in fuselage length, with a width of 11.2 meters and height of 4.7 meters. It is larger than an F-16 fighter and similar in size to an F-18 aircraft. It is designed as a single-seat aircraft with two-seat variants.

The aircraft has an expected top speed of 2,200 kilometers per hour and range of 2,900 kilometers and can carry a payload of up to 7.7 tons.

Korea is growing closer to becoming the eighth country or group of nations to complete development of a domestic supersonic fighter after the United States, Russia, China, Japan, France, Sweden and a European consortium comprised of Britain, Germany, Italy and Spain.

BY SARAH KIM [kim.sarah@joongang.co.kr]