According to the National Transportation Safety Board (NTSB), the left landing gear of an Alaska Airlines Boeing 737-800 collapsed during landing two years ago in Southern California due to “excessive grinding” that occurred during repair.
In its final report, the NTSB said that “maintenance personnel’s excessive grinding of the left main landing gear’s aft trunnion pin during machining, which imparted heat damage to the base metal, led to the fatigue cracking that caused the pin to fracture during landing.”
The plane’s left landing gear collapsed on Aug. 20, 2023, as the Alaska Airlines flight from Seattle touched down at John Wayne-Orange County Airport. According to the pilot, it felt like a “firm jolt” and that the left side of the plane “slammed into the runway.”
None of the 106 passengers and six crew on board were injured. The 737 suffered significant damage to its left wing, which was repaired. The aircraft returned to service four months later.
The NTSB report says the fatigue crack “was located along an area with a darker visual contrast following temper etch and metallographic inspections.”
“Elevated readings and an area of visual contrast were consistent with the area being exposed to higher temperatures becoming softer than the surrounding material,” the NTSB said, while adding that the heat exposure “most likely” came from the grinding.
The landing gear on the Boeing 737-800 was overhauled in July 2018 and investigators said the crack was not present at that time. MRO specialist Sunvair, in Valencia, Calif., performed the work. Sunvair has since added an additional inspection to its trunnion pin overhaul process.
On Tuesday, the NTSB also issued its final report on a Delta Boeing 717, which safely skidded to an emergency landing after its nose landing gear failed to drop on descent into Charlotte, N.C.,
In June 2023, the NTSB pinned that landing gear failure on a broken support piece, caused by metal fatigue.
