What happened
On March 6, 2003, an ATR 42-300, registration I-ATRF, operated by Air Industria for Minerva Airlines, experienced a significant mechanical failure during takeoff at Rome Fiumicino Airport. The aircraft was performing flight N4 403 from Rome to Rimini with 42 passengers on board.
As the crew applied power to the engines while holding the brakes, the aircraft reached approximately 80% torque when a sudden jolt and a leftward yaw occurred. The flight crew immediately aborted the takeoff and applied the parking brake. The incident was caused by the failure of the left main landing gear's swinging lever, the component connecting the wheel axle to the gear strut. The failure caused the gear strut to strike the runway, damaging the gear housing and hydraulic lines, which resulted in a fluid leak on the pavement. There were no injuries to the passengers or crew.
The investigation
The ANSV investigation examined the aircraft's maintenance history, flight data recorder (FDR) information, and the physical wreckage. Analysis of the FDR confirmed that the preceding flight from Rimini to Rome had been completed normally, with no heavy landings or excessive vertical or longitudinal accelerations that could have caused structural damage. Maintenance records were also reviewed, showing that all required inspections for the landing gear had been performed regularly and that the aircraft's airworthiness certificates were valid.
Technical analysis of the failed component, a swinging lever (P/N D56771-6, S/N 122), revealed that the fracture was caused by a fatigue phenomenon. Chemical analysis of the metal at the crack initiation site showed an abnormal concentration of silicon compared to the average alloy composition.
Findings
- The primary cause of the incident was the failure of the left main landing gear swinging lever.
- The failure was driven by a fatigue process initiated by pre-existing surface defects.
- These defects were caused by metallurgical inhomogeneities, specifically an excessive concentration of silicon within the material.
- The investigation identified that these defects originated from a flaw in the casting process during the production of a specific batch of swinging levers (serial numbers 115 through 151 inclusive).
- The investigation ruled out heavy landings, improper maintenance, or corrosion as contributing factors.