What happened
During the take-off roll, the left landing gear of the aircraft collapsed, causing the wing to strike the ground. The failure originated in the lower tube of the left shock strut assembly.
The investigation
Investigators examined the wreckage and identified a fatigue crack within the lower steel tube of the left shock strut. This crack began at the hole where the lower tube meets the slider plate and spread around the entire circumference of the tube. The investigation determined that the final fracture of the tube likely occurred early in the take-off roll, triggering the gear collapse.
Analysis of the component revealed that the dimensions and markings of the reinforcing tube were consistent with an original part. The investigation noted that this specific part was subject to a requirement for replacement or modification under service bulletin SB-AG-36. While the exact age of the lower tube could not be determined, its characteristics suggested it was manufactured before 1994 and had not been updated to meet the SB-AG-36 standard. The upper tube construction was found to be consistent with the earlier SB-AG-31 bulletin.
Findings
- A fatigue crack developed in the lower steel tube of the left shock assembly at the connection point between the tube and the slider plate.
- The crack propagated until it reached a point of final overstress failure during the take-off roll.
- It is highly probable that the lower tube was not replaced or modified in accordance with the instructions provided in SB-AG-36, which was designed to prevent such failures.