AN INVESTIGATION INTO a “serious incident” involving an Aer Lingus flight that suffered a suspected engine fire after take-off has concluded that “fatigue failure” of part of the engine was the probable cause.

High pressure gas that formed in the engine’s compressor bled through the ducting and sparked the fire alarm. 

The Air Accident Investigation Unit (AAIU) has issued a report into the incident which occurred on 28 December 2017 and involved an Aer Lingus Airbus A330-200 jet.

Flight EI-145 had just taken off from Dublin and was bound for Los Angeles. There were 267 passengers and 11 crew on board when the crew received an engine fire warning which required the engine to be shut down.

Following the shutdown, the fire warning ceased.

The flight crew declared a ‘mayday’ and discharged the built-in engine fire extinguisher. Controllers in Dublin advised the crew there was “smoke visible from the aircraft”.

Mobile phone video footage of the take-off, obtained later by the investigation team, showed what appeared to be smoke or vapour coming from the second engine during the initial climb from Dublin.

Following a review of the emergency situation, the flight crew elected to divert to Shannon Airport which had a longer runway than the one at Dublin. The flight entered a holding pattern near Shannon to consume fuel and lighten the aircraft for landing.

The aircraft landed safely about 20 minutes later and was inspected on the runway by the Airport Fire Service (AFS) who advised that there was no apparent damage. The aircraft then taxied to its parking stand, where all passengers disembarked normally.

After being alerted by the duty manager at Shannon Airport, the AAIU contacted the airline to obtain further details and to request that the aircraft’s Cockpit Voice Recorder (CVR) and Digital Flight Data Recorder (DFDR) be preserved once the aircraft had landed.

When the AAIU downloaded data from the CVR, investigators found it been had been overwritten during the removal procedure. The report states that the loss of the CVR data did not greatly impede the investigation although “its availability would have facilitated a better understanding of the occurrence and the subsequent diversion to Shannon”.

Fire warning 

The AAIU investigation determined the probable cause of the incident as “fatigue failure of the No. 2 engine’s 14th stage bleed air spacer, which allowed hot, high pressure bleed air to escape into the No. 2 engine compartment, resulting in a No.2 engine fire warning”.

One “contributory cause” was also identified. The report states: “Metallurgical examination and analysis identified that abnormal loading conditions were the most likely cause of the fatigue cracking.”

According to the engine manufacturer: “Metallurgical investigation was unable to determine root cause of the fracture.

Examination of the failed components suggests that the clamp was not seated properly during the last SV (shop visit) assembly, creating high alternating stresses which led to the eventual fracture of the spacer.

“However, it is also possible that even with a properly seated clamp (coupling), the clamping loads may have resulted in the development of stress concentration areas or damage to the duct”.

Following the incident, the airline initiated a visual examination of the spacers installed on aircraft within its fleet and those fitted to its spare engines. The operator reported that no defects were found during these visual inspections.

The AAIU report made no safety recommendation “as a result of the actions taken by the Engine Manufacturer, the engine overhaul facility, and the Operator, in addition to the action planned by the Aircraft Manufacturer”.