The European Aviation Safety Agency (EASA) has revealed the first clues as to what may have caused the catastrophic failure of the Trent 900 engine powering a Qantas A380 on Nov 4. In an airworthiness directive (AD) issued today, the agency points to an oil fire in the high pressure/intermediate pressure (HP/IP) structure cavity as the suspected cause of an IP turbine disc failure.
The AD requires repetitive inspections of the Low Pressure Turbine (LPT) stage 1 blades and case drain, HP/IP structure air buffer cavity and oil service tubes in order to detect any abnormal oil leakage, and if any discrepancy is found, to prohibit further engine operation.
“The requirements of this AD are considered as interim action. If, as a result of the on-going incident investigation, a terminating action is later identified, further mandatory actions might be considered,” says EASA.
Although not stated, the evident link between the oil system fire and the IPT failure is uncannily similar to the circumstances behind the Trent 1000 failure on the test bed at Derby in August. Although Rolls has already clearly stated the two events are not connected, it seems more answers will be needed – and Boeing, no doubt, will be asking the questions.