Emergency Airworthiness Directive issued for Trent 900

The European Aviation Safety Agency have released Emergency Airworthiness Directive (EAD) 2010-0236-E requiring operators of Trent 900 engines to perform inspections of their engines.

The Directive is applicable to the following engine variants: RB211 Trent 900 series engines, variants RB211 Trent 970-84, RB211Trent 970B-84, RB211 Trent 972-84, RB211 Trent 972B-84, RB211 Trent977-84, RB211 Trent 977B-84 and RB211 Trent 980-84, all serialnumbers.These engines are known to be installed on, but not limited to, AirbusA380 series aeroplanes.

Reason: An uncontained engine failure has recently occurred on a Rolls-RoyceTrent 900 involving release of high energy debris and leading to damage to the aeroplane.Analysis of the preliminary elements from the incident investigation showsthat an oil fire in the HP/IP structure cavity may have caused the failure ofthe Intermediate Pressure Turbine (IPT) Disc.This condition, if not detected, could ultimately result in uncontained engine failure potentially leading to damage to the aeroplane and hazardsto persons or property on the ground.For the reasons described above and pending conclusion of the incidentinvestigation, this AD requires repetitive inspections of the Low PressureTurbine (LPT) stage 1 blades and case drain, HP/IP structure air buffercavity 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.

Required as indicated, unless accomplished previously:

(1) Within the compliance times indicated in Table 1 of this AD, accomplish the following actions in accordance with Rolls-RoyceNon Modification Service Bulletin (NMSB) 72-AG590, Par 3. Accomplishment Instructions, 3.A or 3.B as applicable to the engine configuration:

(1.1) Carry out an extended ground idle run.

(1.2) Inspect the Low Pressure Turbine (LPT) stage 1 blades andcase drain.(1.3) Inspect the HP/IP structure air buffer cavity and oil service tubes.

(2) If any discrepancy is found during the inspections required by paragraph (1) of this AD, any further engine operation is prohibited. Within one day after the accomplishment of the inspection, report the findings to Rolls-Royce.

(3) Inspections accomplished in accordance with the content of NMSB72-AG590 before the effective date of this AD, are acceptable to comply with the initial inspections required by this AD.

(4) After the effective date of this AD, do not operate an engine on an aeroplane unless it has been inspected in accordance with the requirements of this AD.

The Aviation Herald points out that:

An oil fire possibly similiar to the Qantas Trent 972 led to an uncontained engine failure of a Trent 772 engine on Edelweiss’ Airbus A330-200 registration HB-IQZ near Miami, see Final Report: Edelweiss A330 at Miami on Oct 5th 2003, uncontained engine failure during departure. In their safety recommendations released in December 2006 following the conclusion of the investigation the NTSB wrote:

“Disassembly of the No. 1 engine revealed evidence of heat damage and distress in the HP/IP turbine bearing chamber consistent with the presence of an oil fire. Microstructure examination of the fracture surfaces on the IP turbine disk drive arm revealed damage consistent with a localized fire that caused the drive arm to eventually fail and separate, allowing the IP turbine disk to overspeed. The overspeed condition resulted in the liberation of all IP turbine disk blades through the IP turbine case, with some blades striking the airplane. Because thermal damage within the HP/IP turbine bearing chamber and associated hardware prevented identifying the exact cause of the fire based solely on the physical evidence from the No. 1 engine, the No. 2 engine was examined to help establish possible causes or contributors to the bearing chamber fire in the No. 1 engine.

A borescope inspection of the No. 2 engine revealed that the HP/IP turbine bearing chamber internal vent tube was obstructed with a black substance. An airflow check of the vent tube revealed that the air passage was not completely blocked. A nondestructive three-dimensional neutron tomography analysis revealed that the substance was not solid and was characterized by nodules of carbon deposits (also known as coke) with areas of voids. Although coke formations within oil tubes are not uncommon, the morphology, amount, and location of the carbon deposits found in the vent tube of the No. 2 engine were unusual and inconsistent with coke formation seen on other Trent engines or from other service experiences.”

The NTSB had concluded in April 2006 the probable cause of the Trent 772’s failure was:
“the coking (carbon build-up) in a vent tube which led to a fire and the subsequent liberation of the IP turbine blades. Contributing to the cause of the uncontained engine failure was the absence of measures to adequately monitor the in-service performance of a new engine/oil combination.”

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2 Responses to “Emergency Airworthiness Directive issued for Trent 900”

  1. Trent 900: EASA relaxed its inspection directive which reduced inspection frequency « The k2p blog Says:

    […] AD issued in August by the European Aviation Safety Agency (EASA). Since the incident EASA has now issued an Emergency AD regarding the inspection of wear within the Trent […]

  2. Trent 900: EASA relaxed its directive which reduced inspection frequency « The k2p blog Says:

    […] AD issued in August by the European Aviation Safety Agency (EASA). Since the incident EASA has now issued an Emergency AD regarding the inspection of wear within the Trent […]

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