An oil fire in the HP/IP structure may have caused the uncontained failure of a Qantas Airways Rolls-Royce Trent 900 engine on an Airbus A380 last week, says the EASA, which ordered airlines operating the engines to carry out checks.
"Analysis of the preliminary elements from the incident investigation shows that an oil fire in the HP/IP structure cavity may have caused the failure of the intermediate pressure turbine disc," it says in an emergency airworthiness directive.
"This condition, if not detected, could ultimately result in uncontained engine failure potentially leading to damage to the aeroplane and hazards to persons or property on the ground."
The Qantas A380 involved in the 4 November incident had to turn back to Singapore's Changi Airport for an emergency landing after its number two engine suffered an uncontained failure shortly after take-off for a flight to Sydney.
Debris was shed over Indonesia during the failure, and authorities are trying to recover a missing half of the number two engine's disc.
In the airworthiness directive, the EASA calls for "repetitive inspections of the low pressure turbine stage one blades and case drain, HP/IP structure air buffer cavity and oil service tubes in order to detect any abnormal oil leakage".
Engines should not be operated if such abnormalities are found, it adds.
Inspections on on-wing engines must be conducted within 10 flight cycles from 10 November, the date that the directive takes effect, says the EASA.
Qantas is continuing inspections of its Rolls-Royce engines on its A380 fleet, which remains grounded since the uncontained failure. The Oneworld carrier's engineers have removed three engines for further examinations.
"Qantas' ongoing inspection program is fully compliant with this [EASA] directive. The specific checks mandated by the directive were already being carried out by Qantas in conjunction with Rolls-Royce," says the airline.
Singapore Airlines, which also operates Trent 900 engines on its A380s, said yesterday it is changing three engines after inspections.
Lufthansa, the third remaining carrier that operates Trent 900s on A380 aircraft, also said yesterday it would change one engine as a "precautionary" measure.