What happened
On March 12, 2019, an ATR-72-212A, registration PR-AQV, operated by Azul Brazilian Airlines, was performing a scheduled passenger flight from Viracopos International Aerodrome (SBKP) to Leite Lopes Aerodrome (SBRP). The aircraft was carrying 60 passengers and 5 crewmembers.
During the initial stages of the takeoff run, once the aircraft reached approximately 30 knots, the crew experienced significant vibrations and observed abnormal parameters on engine number 2. The flight crew immediately executed the aborted takeoff procedures, successfully maintaining control of the aircraft and bringing it to a stop on the runway. Following the full stop, the control tower reported fire in engine number 2. The crew responded by shutting down the engine, activating the fire extinguisher, and subsequently shutting down engine number 1 as a precaution. The aircraft was later towed to the apron, and all occupants disembarked without injury.
The investigation
CENIPA's investigation focused on the failure of engine number 2, which involved the high and low pressure turbine modules. The investigation also examined a previous incident involving the same aircraft (PR-AQV) that had occurred only ten days earlier, involving a failure of engine number 1.
Investigators analyzed maintenance records, including the use of the WebECTM® monitoring software, which had not indicated any significant performance trends prior to the failure. Laboratory examinations of the engine components revealed that the high pressure (HP) blades had suffered a failure. While the metal alloy met design requirements, the investigation determined that the blades were subject to High Cycle Fatigue.
Findings
- The primary cause of the failure in the engine was High Cycle Fatigue in one of the HP blades.
- Continuous exposure to temperatures exceeding projected limits caused changes in the material's granular structure, leading to premature and catastrophic failure.
- The design characteristics of the High Pressure Turbine Blades (PN 3115601-01) were insufficient to prevent fatigue, even when the components were operated within their established lifetime limits and maintained according to manufacturer instructions.
- The aircraft sustained minor damage, primarily restricted to the internal sections of engine number 2.
Safety action
Following the investigation, several safety recommendations were issued to ANAC, BEA, and TSB, urging a reassessment of the service manuals, maintenance processes, and the operational life limits for HP blades in PW127M engines. Subsequent actions included updates to maintenance parameters and the implementation of improved design projects for the turbine blades to reduce susceptibility to fatigue.