Investigations into the crash of an F-16 fighter jet in South Korea revealed that a missing nut on an engine component led to the aircraft crashing. The part, however, had been missing for 12 years due to a maintenance failure. 

O accident happened on November 20 last year. The aircraft, a KF-16C Fighting Falcon fighter, belonged to the 19th Wing of the South Korean Air Force (ROKAF), and was on a training flight when it suffered an engine failure, forcing the pilot to eject. 

The ROKAF formed a committee to ascertain the causes of the accident, revealed in a report obtained by KBS News at the end of December. After extensive analysis of the wreckage of the aircraft, which crashed in a mountainous region 20 km west of Wonju Air Base, investigators concluded that the damaged fuel pump was the main cause of the accident.

The damage, however, occurred due to a maintenance failure of more than 10 years: the lack of a nut. The nut in question was attached to the aircraft's fuel pump drive shaft. Without the part installed, the shaft vibrated excessively, causing a gear to wear at an abnormal rate, eventually cutting off fuel supply to the engine, a Pratt & Whitney F100-PW-229.

The pilot still tried to restart the engine twice, before being forced to eject. He was rescued and taken to a hospital, where he was later released. The accident also caused a stoppage in operations with the KF-16, as well as the cancellation of a military exercise. 

According to the ROKAF, the axle had been without the nut for over 12 years. The part in question undergoes periodic maintenance every 4000 hours of flight and the last time this happened was in 2010. At the time of the accident, the component had only registered 900 hours of use, much less than scheduled. 

To eliminate similar problems, the ROKAF inspected over 200 engines, including on the F-15K Slam Eagle fighters. Still according to the South Korean portal, 40 engines were found without any problem. In this way, the ROKAF should resume operations with the models on February 02nd. 

At the same time, the Air Force is considering whether to discipline and punish service members responsible for faulty maintenance in 2010. 

South Korean F-16 

The KF-16 forms the backbone of the South Korean Air Force, which has around 167 aircraft. The fighters are being upgraded to the Block 70 standard under a $1,2 billion contract signed in 2016 with Lockheed Martin, the plane's manufacturer.

The model was developed in the 1990s as a version of the F-16C/D adapted to the needs of the country and manufactured locally by Samsung Aerospace, later absorbed by KAI (Korea Aerospace Industries). 

In addition to the F-16s, the ROKAF has F-35 Lightning II, F-15K Slam Eagle, F-5E Tiger II and F-4E Phantom II fighters; the country is investing billions in development of the KAI KF-21 Boramae, which should replace the last two models from 2026.