AD 2016-25-10

This AD becomes effective January 20, 2017.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of January 20, 2017.

For service information identified in this final rule, contact Rolls-Royce plc, Corporate Communications, P.O. Box 31, Derby, England, DE24 8BJ; phone: 011-44-1332-242424; fax: 011-44-1332-249936; email: http://www.rolls-royce.com/contact/civil_team.jsp; Internet: https://customers.rolls-royce.com/public/rollsroycecare. You may view this service information at the FAA, Engine & Propeller Directorate, 1200 District Avenue, Burlington, MA. For information on the availability of this material at the FAA, call 781-238-7125. It is also available on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-6744.

Robert Green, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 1200 District Avenue, Burlington, MA 01803; phone: 781-238-7754; fax: 781-238-7199; email: robert.green@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to the specified products. The NPRM was published in the Federal Register on July 26, 2016 (81 FR 48724). The NPRM proposed to correct an unsafe condition for the specified products. The MCAI states:

Inspection of Trent 800 engines returned from service revealed flame eroded areas and axial cracking on the rear Stage 3 disc of the High Pressure Compressor (HPC) Stage 1-4 drum. This is considered to be the result of a localised fire originating from an excessive rub at the stage 3-4 forward seal fin.

This condition, if not detected and corrected, could lead to an uncontained engine failure and release of high energy debris, possibly resulting in damage to the aeroplane and injury to occupants.

You may obtain further information by examining the MCAI in the AD docket on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-6744.

We gave the public the opportunity to participate in developing this AD. We considered the comments received.

American Airlines, Inc., (AAL) requested that the requirement in paragraph (e)(1)(i) of this AD be revised to allow the standards in the RR Trent 800 Engine Manual (EM) to be used in the assessment for wear and cracks. AAL indicated that RR Trent 800 EM task 72-41-31-200-801 addresses the conditions of wear and cracking and provides limits and rejection criteria. AAL commented that RR has noted that the types of damage described in RR Standard Practices Manual 70-01-02-200-000 including the terms “burned/charred” and “eroded” provide an adequate description of flame erosion.

AAL further indicated that if, based on the proposed requirement in paragraph (e)(1)(ii) of this AD, any wear is found on the forward stage 3-4 seal fin, then the HPC 1-4 rotor would have to be replaced. AAL noted, however, that EM task 72-41-31-200-801 allows the seal fin to exhibit wear within the diametral limits of 23.665 to 23.722 inches.

RR indicated that the requirement in this AD to reject the part for evidence of wear should be eliminated. RR noted that the EM for the affected engines already includes inspections for wear and other damage.

We partially agree. We agree with AAL's assessment that the EM task would allow wear as defined above while paragraph (e)(1)(i) in this AD, as proposed, would not have allowed any wear. We also agree with RR that it is not necessary to specify an inspection for wear.

We disagree that it is necessary to refer to the EM task in the requirements of this AD. We have revised the requirements of this AD to remove the requirement to inspect for “wear.” We are removing this requirement because seal tooth wear serviceability limits are already defined in the RR Trent 800 EM.

RR and AAL requested that the requirement in paragraph (e)(1)(ii) of this AD to machine the HPC stage 3 inner shroud be revised. AAL noted that the HPC 1-4 disks shaft is a life-limited part; therefore, AAL tracks its cycle use, both total part cycles and cycles since last piece-part inspection. There is, however, no mandatory tracking requirement for the HPC stage 3 inner shroud. AAL, therefore, cannot ensure that it can comply with RR Service Bulletin (SB) RB211.72-J195, dated February 26, 2016, before exceeding 5,000 duty cycles since new or since last piece-part inspection of the HPC stage 1-4 rotor disks shaft, as proposed in this AD. AAL and RR suggested that the requirement in paragraph (e)(1)(ii) of this AD become an optional terminating action.

We partially agree. We disagree with revising the requirement in paragraph (e)(1)(ii) in this AD to machine the HPC stage 1-3 shroud because that addresses the unsafe seal clearance condition. We agree, however, that the proposed language in paragraph (e)(1) may be misinterpreted to refer to tracking the cycles on the HPC stage 3 inner shroud. Therefore, we clarified paragraph (e)(1) of this AD to read: “(1) Before the HPC stage 1-4 rotor disks shaft cyclic life exceeds 5,000 duty cycles since new, or 5,000 duty cycles since last HPC stage 1-4 rotor disks shaft piece-part inspection, whichever occurs later, do the following:....” This change clarifies that the 5,000 duty cycles since new criterion in this AD applies only to the HPC stage 1-4 rotor disks and not the HPC stage 3 inner shroud.

The Boeing Company, Inc., commented that it supported the proposed rule as written.

We reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously. We determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.

RR has issued SB RB.211-72-J195, dated February 26, 2016. The SB describes procedures to machine the HPC stage 3 inner shroud and to inspect the HPC stage 1-4 rotor disks shaft. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

We estimate that this AD affects 125 engines installed on airplanes of U.S. registry. We did not estimate any time to machine the HPC stage 3 inner shroud because this is accomplished during routine overhaul. We estimate the following costs to comply with this AD:

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. “Subtitle VII: Aviation Programs,” describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in “Subtitle VII, Part A, Subpart III, Section 44701: General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

We determined that this AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),

(3) Will not affect intrastate aviation in Alaska to the extent that it justifies making a regulatory distinction, and

(4) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):