What happened
On October 28, 2016, a McDonnell Douglas MD-10-10F, registration N370FE, operated by FedEx Express, experienced a left main landing gear (MLG) collapse during its landing on runway 10L at Fort Lauderdale–Hollywood International Airport (KFLL). The aircraft was performing a cargo flight from Memphis International Airport (KMEM) under an instrument flight plan.
During the landing roll, the crew reported hearing a loud bang and multiple thuds, followed by the aircraft yawing to the left. The left main landing gear collapsed, causing the aircraft to move off the left side of the runway. Following the collapse, a fire ignited near the left wingtip. As the crew prepared to evacuate, an explosion occurred in the nearly empty left main fuel tank, caused by burning fuel from a broken supply tube in the engine pylon.
The two crewmembers evacuated the aircraft through the right cockpit window. The captain sustained minor injuries, while the first officer was not injured. The aircraft sustained substantial damage.
The investigation
Investigators examined the wreckage and recovered fragments of the left MLG cylinder. Metallurgical analysis of a 3-by-3-inch fragment revealed a small thumbnail crack located at the radius between the cylinder's inner diameter surface and the air filler valve bore. This crack exhibited features consistent with fatigue cracking that progressed to an overstress fracture of the cylinder.
At the site of the crack initiation, investigators identified a corrosion pit. Examination of the area showed no evidence of the required protective cadmium coating. While the gear had been overhauled in February 2008, it was not possible to determine if the coating had failed to bond, had been removed during subsequent maintenance, or had worn away over time.
Findings
- The left MLG outer cylinder fractured due to fatigue cracking that began at a corrosion pit.
- The corrosion pit formed because the required protective cadmium coating was absent from the air filler valve bore.
- The operator's overhaul limit for the landing gear was 9 years, which exceeded the manufacturer's recommended limit of 8 years or 7,500 flight cycles.
- The left MLG outer cylinder was approximately 152 days away from its next scheduled overhaul under the operator's 9-year policy.