Following a second round of inspections, pickle fork cracks were found on four Boeing 737 NG, bringing the total number of grounded aircraft in South Korea to 13. 

Four Boeing 737 NG aircraft with 20,000-30,000 flight cycles were grounded in South Korea after inspections revealed they had cracked pickle forks. In total, 37 aircraft were subject to inspections last concluded on November 10, 2019, South Korea’s Ministry of Land, Infrastructure and Transport (MOLIT) revealed on November 11, 2019. 

On October 30, 2019, South Korea’s Ministry of Land, Infrastructure and Transport confirmed that nine out of 42 inspected aircraft with over 30,000 flight cycles were withdrawn from active service in the country due to cracks in their pickle forks. These include Boeing 737 NG aircraft owned by Korean Air, Jin Air, and Jeju Air.

Information about the 13 aircraft affected by fuselage cracks were sent to Boeing. The maintenance works means replacing the affected parts and lasts approximately two weeks per aircraft. All 13 affected aircraft are expected to be repaired by January 2020, the ministry states. 

The pickle fork is a suspension system that connects the fuselage with wings and manages stress and torque loading that bends the structure during operation. It is designed to withstand 90,000 life cycles – the whole service life of a Boeing 737NG.

The problem in question was identified in late September 2019, after cracks were found on the pickle fork during the passenger-to-freighter conversion of a Boeing 737-800 NG that logged 35,000 flight cycles, about half of the service lifespan for this aircraft. Preliminary inspections found similar issues on at least other Boeing 737-800s having more than 36,000 flight cycles.

On October 3, 2019, the Federal Aviation Administration (FAA) issued an Airworthiness Directive (AD), urging  Boeing 737NG (models 737-600, -700, -700C, -800, -900, and -900ER) operators to have their aircraft checked for cracks on the suspension system. 

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The Federal Aviation Administration released a new directive for Boeing 737 NG planes after structural cracks had been discovered on several aircraft.
 

Aircraft that have accumulated over 30,000 take-off and landing procedures had to be inspected within seven days of the effective AD date, while airplanes that have accumulated less flight cycles were to be checked with lesser urgency. 

Boeing is expected to conduct additional assessments to determine why aircraft with less than 22,600 cycles could show pickle fork cracks, as well as potential implications of these findings. “Depending on the results of these assessments, additional inspections or repairs may be required”.

Among the latest news of Boeing 737 NG operators affected by the issue are Lion and Ryanair. Lion Air reportedly found cracks on two of its jets, both of which had fewer than 22,000 flights, while Ryanair reportedly grounded at least three aircraft, it became known earlier in November 2019. 

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Almost a month after the FAA issued the Airworthiness Directive, several more airlines, including Qantas, are conducting checks and grounding their Boeing 737 NG aircraft.
 

In total, over 7,000 Boeing 737 NGs have been ordered worldwide, and more than 6,000 of these aircraft are currently in service