Cathay Pacific grounded its A350s after a Zurich-bound jet was forced to turn back to Hong Kong earlier in September
Cathay Pacific grounded its A350s after a Zurich-bound jet was forced to turn back to Hong Kong earlier in September AFP

The engine defect in the Airbus A350 plane that led to the cancellation of dozens of Cathay Pacific flights in early September could have escalated into "extensive damage", according to a Hong Kong probe released Thursday.

Hong Kong-based Cathay Pacific briefly grounded its fleet of A350s for inspections and repairs after a Zurich-bound plane was forced to turn back to Hong Kong on September 2.

The inspection found that components on 15 of the 48-plane fleet of A350s, powered by engines from the British manufacturer Rolls-Royce, had to be replaced.

On Thursday, investigators in the city said a post-flight examination found a "discernible hole in the (fuel) hose", "black soot observed on the aft section of the core engine, indicating signs of a fire" as well as burn marks.

"If not promptly detected and addressed, this situation... could escalate into a more serious engine fire, potentially causing extensive damage to the aircraft," said the report released by the Air Accident Investigation Authority (AAIA).

The preliminary report "should be regarded as tentative", a spokesperson for the authority said Thursday.

The AAIA also made a recommendation to the European Union Aviation Safety Agency (EASA) to require Rolls-Royce to "develop continuing airworthiness information, including but not limited to, inspection requirements of the secondary fuel manifold hoses" of the engines in question.

Cathay's incident prompted other airlines in Asia to carry out similar checks on their A350-900 and A350-1000 models, which are powered by Rolls-Royce Trent XWB-84 and XWB-97 engines, respectively.

The European Union Aviation Safety Agency also mandated inspections on A350-1000s.

There are 86 such planes in service worldwide, according to the EASA.

Qatar Airways is the biggest operator of the 1000 version, with 24 in its fleet, followed by Cathay Pacific and British Airways, which both operate 18.

Airbus and Rolls-Royce earlier said they are cooperating with Cathay, but could not comment further pending the investigation.