ATA 72 – Engine – Removal / De-Pairing
Manufacturer(s):
Rolls-Royce plc (RR)
Applicability:
Trent 1000 engines (any configuration), serial numbers (ESN) 10196, 10253, 10290, 10292, 10294, 10295, 10340, 10347, 10380, 10381, 10408, 10409, 10427, 10434 and 10435, except those that embody RR Mod 72-H818 in production, or have been modified by RR Service Bulletin (SB) TRENT 1000 72-H818 in service.
These engines are known to be installed on, but not limited to, Boeing 787 aeroplanes.
Reason:
An occurrence was reported where, following N2 vibration and multiple messages, the flight crew performed an engine in-flight shut-down (IFSD) and returned to the departure airport, landing uneventfully. The post-flight borescope inspection of the engine revealed an intermediate pressure turbine blade (IPTB) missing at the shank. Analysis shows that this kind of failure is due to sulphidation corrosion cracking.
This condition, if not detected and corrected, could lead to IPTB shank release, possibly resulting in an IFSD and consequent reduced control of the aeroplane.
To address this potential unsafe condition, RR issued Alert NMSB Trent 1000 72-AJ575 to provide instructions for engine removal from service when any IPTB with a high level of sulphidation exposure is identified by corrosion fatigue life (CFL) model. Consequently, EASA issued AD 2017-0056 to require removal from service of certain engines, to be corrected in shop.
Since that AD was issued, prompted by further occurrences and analyses, it has been decided that, to reduce the risk of dual IFSD, a new cyclic life limit must be applied to certain engines, which determines when an engine can no longer be installed on an aeroplane in combination with certain other engines.
For the reason described above, this AD requires de-pairing of the affected engines. This AD is considered an interim action and further AD action may follow.
Required Action(s) and Compliance Time(s):
Required as indicated, unless accomplished previously:
Note 1: Where, in this AD, reference is made to an RR SB or NMSB with an ‘A’ (Alert) in the number, it should be recognised that an earlier or later revision may not have that ‘A’. This kind of change does not effectively alter the publication references for the purpose of this AD.
De-Pairing of Affected Engines:
(1) For an aeroplane that has two affected engines installed: Before both engines exceed their respective IPTB cyclic limit, as specified in Appendix 1 of the NMSB, or within 20 flight cycles after the effective date of this AD, whichever occurs later, remove one of the affected engines from the aeroplane.
Affected Engine Installation:
(2) After removal of an affected engine, as required by paragraph (1) of this AD, do not install that engine on an aeroplane, except within the limitations as specified in Section 3.A of the NMSB.
Terminating Action:
(3) Modification of an affected engine in accordance with the instructions of RR SB TRENT 1000 72-H818 constitutes terminating action for the requirements of paragraphs (1) and (2) of this AD for that engine.
