What happened
On September 27, 2022, an Avianca Boeing 787-8, registration N781AV, was performing a scheduled commercial flight from Bogotá El Dorado International (SKBO) to London Heathrow (EGLL). While cruising at FL410, approximately six hours and 18 minutes into the flight, the aircraft experienced an uncommanded in-flight shutdown of engine number one.
The flight crew immediately identified the engine failure following three Master Caution alerts on the EICAS display, specifically indicating ENG FAIL L, ENG CONTROL L, and ENG EEC C1 L. Following standard operating procedures for an inoperative engine, the crew initiated a descent to FL270. Two manual restart attempts were unsuccessful, and an additional fault regarding the left engine fuel valve was displayed.
The crew declared an emergency and coordinated a diversion to the nearest suitable airport, Lajes in the Azores. During the diversion, the crew was supported by the operator's dispatch and maintenance centers in Bogotá via ACARS and SATCOM. The relief First Officer was called to the cockpit to assist with the flight. The aircraft landed safely on runway 15 at Lajes at 12:40 UTC with no injuries to the 10 crew members or 244 passengers.
The investigation
The GPIAAF investigation focused on the mechanical cause of the engine shutdown and the maintenance history of the Rolls-Royce Trent 1000 engine. A preliminary inspection of engine number one revealed a significant crack in the external gear box (EGB) casing and a substantial amount of spilled oil in the area.
The investigation examined the maintenance records of the engine, noting that previous shop visits had identified wear on the ADS (Airshaft Drive Shaft) assembly. Specifically, the investigation looked into the transition of maintenance tasks from the engine maintenance manual to the aircraft maintenance manual (AMM) and the accuracy of on-wing inspection methods used to monitor spline wear on the ADS coupling and IP shaft.