For once, it's not the 737 Max that causes Boeing trouble, but its predecessor, the 737 NG. On some models, premature material fatigue had been discovered on key components.
They are installed vertically and are an integral part of the attachment of the wings to the fuselage. They also help to absorb the extreme forces acting on the wings in flight. They are known as pickle forks in the jargon as they resemble a cucumber fork (see graphic below).
The pickle forks are designed to last an entire aircraft lifetime. The components should hold 90,000 flights, which means 90,000 take-offs and landings. But now technicians of an airline in the United States have found significant cracks in a Boeing 737 NG after only 35,000 flight cycles. The Seattle TV station Komo has reported on this. «It’s not designed to crack that way at all. Period.», a former Boeing engineer explained in the report. Each Boeing 737 NG has four pickle forks.
«Small number of planes»
After an inspection of further 737 NG aircraft – i.e. 737-600,-700,-800 and -900 – further cracks were detected. Boeing confirmed the discovery to Komo. «Safety and quality are our top priorities. Boeing has notified the FAA and been in contact with 737NG operators about a cracking issue discovered on a small number of airplanes undergoing modifications.» a spokesman stated. They are working with operators to set up an inspection plan for affected jets.
The US aviation authority also confirms the cracks. «The FAA will require operators of certain Boeing 737NG jetliners to conduct inspections for structural cracks.» There have not been any in-flight problems so far due to the premature material fatigue. Nevertheless, all affected aircraft must be inspected, as such cracks can grow over time and develop into a serious risk.
737 Max not affected
For the operators, this is a tedious task. Replacing the components is time-consuming and expensive. At the same time, they currently depend a lot on NG aircraft due to the worldwide 737 Max grounding. The new model is not affected by the problem as they have by far not reached enough flight cycles.