Discussion
We were informed about the discovery of axial cracks in the interstage 5-6 seal teeth of the HPC stages 2-5 spool spacer arm, due to an incorrectly installed stage 6 seal ring, in a GP7270 model turbofan engine. The incorrect installation of the stage 6 seal ring created a leakage path from the aft cavity to the forward cavity of the HPC stage 6 disk. This leakage elevated the
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temperature in the cavity and adversely affected the material properties of the HPC stages 2-5 spool. This condition, if not addressed, could result in failure of the HPC stages 2-5 spool, an uncontained HPC stages 2-5 spool release, damage to the engine, and damage to the airplane. We are issuing this AD to address the unsafe condition on these products.
Related Service Information Under 1 CFR Part 51
We reviewed EA Alert Service Bulletin (ASB) EAGP7-A72-395, Revision No. 2, dated August 2, 2018. The SB describes procedures for performing a borescope inspection of the installed HPC stages 2-5 spool for cracks, visual inspection of the stage 6 seal ring for correct installation, visual inspection of the interstage 5-6 seal teeth for damage, and removal and replacement of parts if damage or defects are found that are outside serviceable limits, within the identified cycles. 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.
FAA's Determination
We are issuing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.
AD Requirements
This AD requires inspection of the stage 6 seal ring for correct installation and inspection of the HPC stages 2-5 spool for cracks. This AD also requires removal and replacement of the HPC stages 2-5 spool if the stage 6 seal ring is incorrectly installed or the interstage 5-6 seal teeth are found cracked.
FAA's Justification and Determination of the Effective Date
No domestic operators use this product. Therefore, we find good cause that notice and opportunity for prior public comment are unnecessary. In addition, for the reason stated above, we find that good cause exists for making this amendment effective in less than 30 days.
Comments Invited
This AD is a final rule that involves requirements affecting flight safety and was not preceded by notice and an opportunity for public comment. However, we invite you to send any written data, views, or arguments about this final rule. Send your comments to an address listed under the ADDRESSES section. Include the docket number FAA-2018- 0938 and Product Identifier 2018-NE-36-AD at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this final rule. We will consider all comments received by the closing date and may amend this final rule because of those comments.
We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this final rule.
Costs of Compliance
We estimate that this AD affects zero engines installed on airplanes of U.S. registry.
We estimate the following costs to comply with this AD:
Estimated Costs ----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Borescope inspection of stage 6 seal 4 work-hours x $85 per$0 $340 $0
ring and interstage 5-6 seal teeth hour = $340.
forward and aft faces only. ----------------------------------------------------------------------------------------------------------------
We estimate the following costs to do any necessary replacements that would be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these replacements:
On-Condition Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement of HPC stages 2 to 5 spool..... 8 work-hours x $85 per hour = $680. $346,540 $347,220 ----------------------------------------------------------------------------------------------------------------
Authority for This Rulemaking
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.
This AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to engines, propellers, and associated appliances to the Manager, Engine and Propeller Standards Branch, Policy and Innovation Division.
Regulatory Findings
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
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distribution of power and responsibilities among the various levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive Order 12866,
(2) Is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska, 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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.