What happened
On September 29, 2021, an Airbus A320-271N was operating a scheduled passenger service from Santiago, Chile, to Cali, Colombia. While cruising at 38,000 feet, approximately 100 nautical miles west of Iquique, the flight crew received an alert from the Electronic Centralized Aircraft Monitor (ECAM) indicating low oil quantity and pressure in the number two (right) engine.
In response to the warning, the crew diverted the aircraft toward Diego Aracena Airport (SCDA) in Iquique. During the diversion, the oil quantity indicator dropped to zero, and the oil pressure decreased rapidly. Following established emergency procedures, the crew performed an in-flight shutdown of the right engine and declared an emergency. The aircraft landed safely at SCDA with no injuries to the 55 passengers or 6 crew members, and no damage to the airframe.
The investigation
DGAC Chile investigators examined the aircraft and its engines following the incident. A physical inspection of the right engine revealed oil residue on the ground beneath the unit and oily deposits within the engine's inspection covers. The investigation confirmed that the oil tank for the number two engine was empty and identified a leak along the oil line leading to the Accessory Gearbox (AGB).
Technical analysis provided by the engine manufacturer, Pratt & Whitney, and the aircraft manufacturer, Airbus, determined that the leak originated from a loose connection at the LP35/AGB interface. This looseness caused asymmetric wear on the AGB housing and the adapter mounting surfaces, eventually leading to the separation of the seal and the subsequent oil loss.
Findings
- The primary cause of the engine shutdown was the total loss of oil due to a leak.
- The leak was caused by a loose connection at the Accessory Gearbox (AGB) interface.
- The affected engine was a relatively new unit that had only flown 237.71 hours since the issuance of a relevant Service Bulletin (SB).
- While Pratt & Whitney had issued Service Bulletins in May 2021 to inspect and retorque this specific connection, the engine in this incident had not yet been subject to these maintenance actions because the LP35 line had not been disturbed since the engine's production.