What happened
On March 7, 2019, a Go Air Airbus A320-271(NEO), registration VT-WGT, was performing a scheduled passenger service from Patna to Delhi. While the aircraft was cruising at 38,000 feet, the crew received an ECAM alert indicating a significant drop in engine oil pressure. The pressure plummeted from 100 to just 2 units within a five-second window.
In response to the deteriorating engine parameters, the flight crew reduced power on Engine #1 and subsequently performed a commanded in-flight shut down (IFSD). Following the engine failure, the crew requested a descent to 24,000 feet and diverted the flight to Lucknow. The aircraft landed safely at Lucknow airport using only a single engine, and all 134 occupants, including the crew, remained uninjured.
The investigation
AAIB India investigators examined the aircraft and its engines to determine the source of the oil loss. Post-flight inspections revealed significant oil traces on the exhaust nozzle, tail cone, and thrust reverser cowl. The engine oil quantity had depleted from 20 quarts at the start of the flight to only 2 quarts by the time of landing.
Detailed disassembly of the Engine #1 Main Gear Box (MGB) revealed extensive internal damage. Investigators found metal debris in the chip collector and identified that the Main Oil Pump/Integrated Drive Generator (IDG) gear was damaged. Further examination of the components showed a fractured gear shaft assembly, a fractured MGB housing with deep scoring, and various damaged parts including the PMA and starter drive components.
Findings
- The primary cause of the incident was a high cycle fatigue fracture of the IDG oil pump drive gear shaft assembly.
- This fracture was triggered by the resonance response of the shaft assembly to specific engine operating conditions.
- The failure of the gear shaft led to secondary damage across multiple MGB components, including the hydraulic pump and deoiler.
- This mechanical failure caused improper oil scavenging and insufficient air sealing, which directly resulted in the low oil pressure warnings and the subsequent engine shutdown.
- The aircraft had been maintained in accordance with all required Airworthiness Directives and Service Bulletins.