What happened
On 10 May 2001, a McDonnell-Douglas MD-83, registration EC-FXI, was operating a charter flight from Palma de Mallorca to Liverpool Airport. During the landing phase, the aircraft was performing an automatic landing with the first officer acting as the pilot flying.
Upon touchdown, the right main landing gear collapsed. Following the collapse, the commander took control of the aircraft as it continued along the runway. The aircraft maintained the centerline for a period but eventually came to a stop with the right wing making contact with the ground. Despite the incident, the passengers were successfully evacuated using the forward escape slides and the left overwing emergency exit.
The investigation
The AAIB investigation focused on the structural integrity of the landing gear and the circumstances leading to the failure. Investigators examined the aircraft's maintenance history, the metallurgical properties of the failed component, and the flight recorder data.
Technical analysis revealed that the right main landing gear oleo cylinder had failed immediately upon the application of spin-up drag loads during touchdown. Metallurgical examination of the cylinder identified a fatigue crack measuring 3.2 mm in length and 1.0 mm in depth, along with several smaller associated cracks. The investigation also looked into the effectiveness of previous mandatory inspections and the potential role of manufacturing defects, such as surface irregularities from the grit-blasting process, in the development of these cracks.
Findings
- The primary cause of the accident was the failure of the right main landing gear cylinder due to a pre-existing fatigue crack.
- The crack was located in a critical area of the cylinder, just below the attachment trunnions.
- The investigation could not definitively determine the origin of the cracks, but noted that surface irregularities from the manufacturing process were present.
- It is suspected that abnormal loading, such as 'gear walking' (a type of fore-and-aft vibration), may have caused the cracks to grow to a critical size.
- Previous mandatory non-destructive examinations (NDE) had failed to detect the crack, likely because the critical crack size was extremely small and difficult to identify using the procedures in place at the time.
- This incident marked the third known case of a similar main landing gear failure in the MD-80 series aircraft.