Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain EA GP7270 turbofan engines. The NPRM published in the Federal Register on October 1, 2015 (80 FR 59081). The NPRM was prompted by the manufacturer informing us that the inspection criteria and repair procedures in the maintenance manual for aft bolt holes of the HPC cone shaft, also referred to as the ``HPC forward stubshaft,'' for the affected engines is incorrect. The NPRM proposed to require inspection of the HPC cone shaft and repair of affected parts, if needed. We are issuing this AD to prevent failure of the HPC cone shaft, which could lead to uncontained engine failure and damage to the airplane.
Comments
We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM (80 FR 59081, October 1, 2015) and the FAA's response to each comment.Request To Add Engine Models
EA requested that we expand the applicability to include the GP7272 and GP7277 engine models.
We disagree. There are no GP7272 or GP7277 engines in service nor have any been delivered. New engines would be delivered with corrected service
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information and would not be impacted by this AD. We did not change this AD.
Request To Change the Unsafe Condition Statement
EA requested that the unsafe condition statement be changed from ``We are issuing this AD to prevent failure of the HPC cone shaft, which could lead to uncontained engine failure and damage to the airplane.'' to ``We are issuing this AD to prevent a hazardous engine condition.'' The reason for this request is that no HPC cone shaft failures have occurred in the field.
We disagree. The unsafe condition statement describes the condition we are trying to prevent and is the justification for this AD. It does not describe what has occurred in the past. Wedid not change this AD.
Request To Change Various Paragraphs
EA requested that we revise the part nomenclature in the Applicability, Compliance, and Installation Prohibition paragraphs and in the unsafe condition statement to include both ``cone shaft'' and ``forward stubshaft.'' The part is referenced as a ``cone shaft'' in this AD and engine and component manuals; however, it is referred to as a ``forward stubshaft'' in the service bulletins (SBs).
We disagree. The part nomenclature listed in the airworthiness limitations section and engine maintenance manual is ``cone shaft.'' The Discussion section of this AD explains that the terms ``cone shaft'' and ``forward stubshaft'' are synonymous. We consider including both terms throughout this AD unnecessary. We did not change this AD.
Request To Revise the Compliance
EA requested that the Compliance paragraph be revised to include the word ``pits'' when describing the inspection criteria.
We agree. We revisedparagraph (e)(1) and (f)(1) of this AD from ``. . . nicks, dents, and scratches . . .'' to ``. . . nicks, dents, pits, and scratches. . . .''
Request To Change the Compliance
EA requested that we replace ``Do not reinstall the HPC cone shaft if the aft bolt hole has a nick, dent, or scratch that is greater than 0.002 inch in depth'' in paragraph (e)(1) of this AD with ``Comply with the Accomplishment Instructions in EA SB No. EAGP7-72-330 if the aft bolt hole has a nick, dent, pit, or scratch that is greater than the serviceable limit.''
We disagree. The current engine manual has an approved repair procedure for damage that is more severe than the installation requirements of this AD. It is not necessary to restate what is already allowed by the engine manual. We did not change this AD.
Request To Change Service Information
EA requested that the phrase ``or later'' be used when referring to SBs.
We disagree. We are only authorized to mandate use of SBs thatwe have reviewed and which are published. Since future revisions of SBs are not yet published, we are not authorized to mandate their use. We did not change this AD.
Request To Change the Installation Prohibition
EA requested that we change the Installation Prohibition paragraph to read: ``After the effective date of this AD, do not install an HPC cone shaft onto an engine: (1) that has accumulated more than 9,000 cycles since new that has not complied with this AD on an applicable part, and (2) has a nick, dent, or scratch in an HPC cone shaft aft bolt hole that is greater than the serviceable limit.''
We disagree. The intent of the Installation Prohibition paragraph is to mandate the new serviceable limit of 0.002 inch for damage to the inner diameter of the bolt holes for the entire GP7270 fleet. Any parts with damage beyond this limit may be repaired using the approved procedures listed in the engine manual, provided that you include shot peening as required by paragraph (f)(2) of this AD. We did not change this AD.
Conclusion
We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously.
We also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.
Related Service Information Under 1 CFR Part 51
EA has issued SB No. EAGP7-72-329, dated July 21, 2015 and SB No. EAGP7-72-330, dated July 21, 2015. The service information describes procedures for shotpeening the HPC forward stubshaft and inspecting the HPC forward stubshaft bolt-hole inner diameter respectively. 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 of this final rule.
Costs of Compliance
We estimate that this AD affects zero engines installed on airplanes of U.S. registry. The average labor rate is $85 per hour. Based on these figures, we estimate the cost of this AD on U.S. operators to be $0.
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.
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 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 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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.