AD 2020-14-04 Prompted By Occurrences Of In-Service Engine Surges

The FAA is adopting a new airworthiness directive (AD) for all Rolls-Royce Deutschland Ltd. & Co KG (RRD) Trent 1000-A, Trent 1000-AE, Trent 1000-C, Trent 1000-CE, Trent 1000-D, Trent 1000-E, Trent 1000-G, and Trent 1000-H model turbofan engines.

This AD requires removing and replacing one or both affected engines, depending on whether the engine pairing combinations are compliant or non-compliant, as described in the service information. This AD was prompted by occurrences of in-service engine surges on affected RRD Trent model turbofan engines with a high number of intermediate pressure compressor (IPC) module flight hours since new (HSN) or cycles since new (CSN). The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective July 23, 2020.

Supplementary Information: The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA AD 2020-0010R2, dated March 4, 2020 (referred to after this as “the MCAI”), to address an unsafe condition for the specified products.

The MCAI states:

• Occurrences have been reported of engine surges on certain Trent 1000 engines, particularly those that have accumulated a high number of flight hours (FH) and engine flight cycles (EFC). The investigation into the cause(s) of these events is ongoing. This condition, if not corrected, could lead to a dual engine surge, possibly resulting in a dual engine in-flight shut-down and consequent reduced control of the aeroplane.
• To address this potential unsafe condition, Rolls-Royce published the NMSB to provide de-pairing instructions, reducing the risk of a dual surge event. Instructions for in-shop performance recovery are being developed. Prompted by some errors detected in Table 1 of the NMSB, Appendix 1 of this [EASA] AD must be used instead. RollsRoyce will revise the NMSB to correct those errors.
• For the reasons described above, EASA issued AD 2020-0010 (later revised) to require de-pairing of the affected engines.
• Since EASA AD 2020-0010R1 was issued, Rolls-Royce issued NMSB TRENT 1000 72-K494, providing instructions for in-shop action to restore the surge margin.
• Embodiment of Part B of this NMSB allows relaxation of the de-pairing actions as required by this [EASA] AD. Rolls-Royce have revised NMSB TRENT 1000 72-AK468 accordingly, including a new Table 1, defining de-pairing upper and lower thresholds (pre- and post-NMSB 72-K494 embodied) and Table 2 (which was Table 1 in the NMSB 72-AK468 at original issue) for de-pairing when one engine has embodied Part B of NMSB TRENT 1000 72-K494, and when both engines have embodied Part B of NMSB TRENT 1000 72-K494.
• Consequently, this [EASA] AD is revised to include references to NMSB TRENT 1000 72-K494 and to NMSB TRENT 1000 72-AK468 Revision 1, and Table 2 thereof.

FMI: www.regulations.gov