What happened
On January 7, 2020, a scheduled Go Air flight from Delhi to Varanasi experienced a significant powerplant malfunction during the climb phase. While the Airbus A320(NEO), registration VT-WGC, was passing flight level 340, the crew received an "Engine Stall" warning followed by a "High Engine Vibration" alert on the ECAM.
Upon reviewing the engine parameters, the crew noted high vibration levels on the number 2 engine. Following established checklists, the crew gradually reduced power on the affected engine to idle. Due to persistent high vibration, the crew declared a "PAN PAN" urgency signal to Delhi Air Traffic Control and initiated an air turn back. As a precautionary measure, the crew performed an in-1flight shutdown of the number 2 engine. The aircraft subsequently completed a single-engine landing at Delhi airport without further incident. There were no injuries to the 48 passengers or the 6 crew members on board.
The investigation
An investigation by the AAIB examined the aircraft's maintenance history and the physical condition of the engines. Post-flight inspections of the engine exhaust area revealed that the 3rd stage Low-Pressure Turbine (LPT) blades were severely damaged.
Laboratory analysis conducted by the National Aerospace Laboratories (NAL) confirmed that all 78 LPT 3rd stage blades had fractured. The study determined that the blades, constructed from a Gamma-phase Titanium Aluminide (Ti-Al) intermetallic material, failed in a brittle manner. The investigation found that the material lacked sufficient crack growth resistance and damage tolerance to withstand impacts from upstream debris.
Findings
- The primary cause of the incident was the failure of the LPT 3rd stage blades due to the material's inherent lack of impact tolerance and crack growth resistance.
- The engine was equipped with pre-modified LPT 3rd stage blades that were sensitive to impact damage.
- This incident was part of a known series of similar events involving the same engine type, which led the manufacturer to issue Service Bulletin 72-00-0111 to introduce more resistant blades.
- All required airworthiness documentation and pilot qualifications were valid at the time of the event.