What happened
On November 13, 2018, an Aerolíneas Argentinas flight, operating a Boeing 737-800 MAX, registration LV-HKW, was en route from Buenos Aires to Punta Cana when it encountered severe weather conditions. While cruising near a convective storm area, the crew detected significant vibrations in the left engine. The vibration levels reached a reading of 5.0, which represents the maximum allowable limit.
Following the procedures outlined in the aircraft's Quick Reference Handbook (QRH) for high engine vibration, the crew diverted the aircraft to the Resistencia International Airport in Chaco, Argentina. During the final approach at approximately 9,000 feet, the vibrations ceased, allowing for a normal landing. There were no injuries to the 173 passengers or the crew on board.
The investigation
Technical inspections of the left CFM-56 Leap-1B engine revealed physical damage to the engine components. Investigators identified abrasion marks on seven fan blades, as well as wear on the engine's internal noise suppressor (the abradable).
To assess the severity of the damage, technical personnel conducted engine ground runs at various power settings. These tests confirmed that the vibration levels had returned to normal parameters. Based on the findings, the engine manufacturer authorized a single engine cycle for a ferry flight to transport the aircraft to a maintenance facility. Meteorological data from the time of the incident indicated that the aircraft was flying through an area of severe icing potential, with temperatures at flight level 330 reaching -37 degrees Celsius.
Findings
- The aircraft experienced engine vibrations exceeding standard operational limits during the cruise phase.
- The crew correctly implemented the QRH procedures to manage the engine anomaly.
- The vibrations were likely caused by crystal icing, where ice accumulates behind the engine spinner, creating an imbalance in the fan assembly that leads to blade tip contact with the engine casing.