What happened
On February 5, 2023, an IndiGo Airbus A320-271N, registration VT-ISE, was performing a scheduled flight from Amritsar to Kolkata. Shortly after takeoff from Amritsar Airport, while the aircraft was climbing through approximately 3,000 feet, the crew heard a loud bang. This was immediately followed by multiple engine failure messages on the ECAM, including engine stall, high vibration, and oil chip detection.
The flight crew promptly executed emergency procedures, securing the malfunctioning number one engine. To ensure safety, the pilots declared a PAN-PAN urgency signal and decided to return to Amristat. The aircraft performed a single-engine landing safely on runway 34. There were no injuries among the 125 passengers and 6 crew members on board.
The investigation
AAIB India examined the engine and the aircraft's maintenance history. Post-flight inspections revealed significant internal damage to the number one engine, including broken blades in the Low-Pressure Turbine (LPT) stages 1 through 3, and severe damage to the High-Pressure Compressor (HPC) and High-Pressure Turbine (HPT) stages.
Investigators traced the origin of the failure back to a previous maintenance event at an engine shop. The investigation focused on the installation of the HPT 2nd stage air seal wire seal. Analysis confirmed that this wire seal had dislodged from its groove, a condition likely caused by improper assembly during the engine's last shop visit.
Findings
- The primary cause of the incident was the fracture of the HPT 2nd stage air seal due to axial rubbing between the seal and the Turbine Intermediate Case (TIC) inner case.
- This rubbing was triggered by a misassembled wire seal, which created a local bulge and reduced the clearance between the air seal and the TIC.
- The hardware design process failed to accurately account for the maximum possible gap closure between these components.
- The resulting internal object damage caused a high rotor imbalance, leading to the engine stall and subsequent damage to the compressor and turbine stages.