How S. Korean fighter jets are assembled by hand

KAI opened up the KF-21 assembly line to the Hankyoreh

The assembly line for prototypes of the KF-21 Boramae, a South Korea jet fighter (Kim Jae-seob/The Hankyoreh)

I stood on the assembly line for prototypes of the KF-21 Boramae, a South Korea jet fighter, on Friday at a factory operated by Korea Aerospace Industries (KAI) in Sacheon, South Gyeongsang Province.

The first prototype was unveiled in a roll-out ceremony — sso-calledbecause the assembled plane “rolls out” on its own wheels — that was attended by South Korean President Moon Jae-in on April 9. The next five prototypes are being assembled on the line, with their guts on full display. The second prototype is currently being tested to check whether missiles can be loaded properly.

The first prototype of the KF-21 Boramae that was unveiled in a roll-out ceremony

KF-21 assembly line made public for the first time

Airplane prototypes are made to run various tests, including test flights, before the planes go into mass production. The planes are opened up and taken apart to fix or replace flawed parts and then reassembled for more tests — a process that’s repeated over and over again.

Before the prototype plane can receive the OK for a test flight, it has to go through a year or so of ground testing.

KAI opened up the KF-21 assembly line to the Hankyoreh, the first South Korean newspaper to gain access to the site. The wings and fuselages of the fighters on the assembly line were all painted light green, reminding me of the tender leaves on a mulberry tree in the early spring.

Almost the entire assembly process is done by hand. Twenty engineers were working together to load missiles on the second prototype plane.

The TA-50 advanced training aircraft

“You may have imagined the kind of conveyer belt you might see on an automobile assembly line, but this is completely different,” said Kim Jun-myeong, head of KAI’s operations department, with a smile.

“Airplanes can’t be welded because they’re made of aluminum and other special materials. We assemble the fuselage and attach wings to the fuselage by drilling lots of holes on both sides for inserting rivets. A single wing needs more than 10,000 rivets,” said Lee Il-woo, a senior engineer on the KF-21 project.

Running my hand along the joint, I find the rivets as dense and neat as if they’d been sewn by machine. The rivets themselves are so smooth I can’t even feel them with my hand. If a rivet protruded even a single millimeter from the surface, it would create air resistance.

“The interior of the fighter has a complicated latticework designed to continue functioning even if some parts are damaged by gunfire during a dogfight. Electronic equipment runs from the cockpit to the ends of the wings,” Lee said.

There are nine fuel tanks attached to the plane, all of which are designed to be controlled electronically from the cockpit.

The KT-1 basic training aircraft

The electronic devices on the half-finished prototype I was shown on Friday were connected by cables of various lengths and thicknesses, which ran through conduits in the latticework, sometimes bunched up and sometimes spreading apart. Some of the cables were tied together at intervals of one to two centimeters and attached tightly to the latticework frame of the fuselage.

“Because the fighter is so fast and has to make sharp climbs repeatedly and steep dives, any slack in the wiring would make noise and cause damage,” Lee said.

The prototype roll-out marks the midway point in development

Once the fighter prototypes are equipped with various weapons, they’re moved to the location for ground testing. It took the first prototype around six years to reach this stage.

The first prototype is currently in the building opposite the assembly line, where its insides are exposed for ground testing. That alone will take another year or so.

The KUH Surion

“We keep running ground tests and making improvements until we decide that the fighter is ready to be fueled up and sent on a test flight. If we confirm that there are no problems after 2,341 hours of test flights, we begin mass production. In terms of the total development schedule, we’ve reached the midway point,” said Ryu Gwang-su, head of KAI’s fixed-wing project division.

Helicopters ordered by the police and the South Gyeongsang Province Fire Department are being assembled on the rotary-wing line. Just as with jet fighters, a considerable amount of this work is done by hand.

“These helicopters are civilian versions of the KUH Surion, a military transport helicopter that was developed to improve our defense capabilities. Before delivery, we add specific functions needed by our clients, which include fire departments, the police, and corporations,” said Kim, head of operations.

The KUH Surion is being assembled.

KAI divides its projects into “fixed-wing” and “rotary-wing” divisions, depending on the type of aircraft. The fixed-wing division mass produces the KT-1 basic training aircraft and the TA-50 advanced training aircraft both for the Republic of Korea Air Force and for export to countries such as Thailand and Malaysia. That led to the development of the KF-21 in partnership with Indonesia.

A total of 170 KF-21 fighters have been ordered. KAI plans to enter mass production in the middle of 2024, following ground testing and the first flight.

The prototype of the light-armed helicopter being developed by Korea Aerospace Industries

KAI’s rotary-wing division supplies the Surion transport helicopter to the South Korean military and foreign governments, including Cambodia and Indonesia. Division engineers are currently developing a small attack helicopter.

“When the advanced training aircraft finished its first flight and came down the runway, staff were crying and hugging each other on the factory roof,” Kim said.

By Kim Jae-seob, senior staff writer

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