Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2017-20-06, Amendment 39-19063 (82 FR 46379, October 5, 2017), (``AD 2017-20-06''). AD 2017-20-06 applied to certain Honeywell International Inc. (Honeywell) AS907-1-1A turbofan engines. The NPRM published in the Federal Register on January 30, 2018 (83 FR 4167). The NPRM was prompted by the need to clarify the Applicability and Compliance sections of AD 2017-20-06. The NPRM proposed to continue to require one-time inspection of the LPT2 blades and, if the blades fail the inspection, the replacement of the blades with a part eligible for installation. We are issuing this AD to address the unsafe condition on these products.
Comments
We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM and the FAA's response to each comment.
Request To Align the Compliance Requirements With the Service Bulletin (SB)
Bombardier Aerospace (Bombardier) requested that the compliance
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requirements of the AD be aligned with Honeywell SB AS907-72-9067, Revision 1, dated March 20, 2017. Bombardier asked that we remove the requirements for measured wear requirements for recording of wear. Bombardier noted that Honeywell SB AS907-72-9067 requires contact between the LPT2 rotor blade Z-gap.
We disagree. Honeywell SB AS907-72-9067, Revision 1, dated March 20, 2017 and the compliance section of this AD provide the same guidance for measuring and recording wear with a borescope at the LPT2 blade shroud Z-gap. Reported borescope inspections of high-time engines show that blade-to-blade contact at the Z-gap is difficult to measure with a borescope. The FAA and Honeywell agree that the measured wear limit of 0.005'', as defined by the Honeywell Light Maintenance Manual (LMM) AS907-1-1A, 72-00-00, is acceptable for this AD.
Additionally, theFAA disagrees with the request to remove the requirement for recordings of the borescope inspection. We find that making these recordings with a clean digital image helps us to identify wear characteristics, severity, and cumulative damage of LPT2 blade assembly and to provide future borescope requirements for LPT blade maintenance. We did not change this AD.
Request To Revise Costs of Compliance
Bombardier Aerospace requested that we align the cost estimates in this AD with the cost estimates in Honeywell's SB.
We disagree. The slight differences in costs between the NPRM and Honeywell's SB reflect the additional recording requirements in this AD. We did not change this AD.
Revision to Applicability
The intent of the NPRM was to limit the applicability of this AD to affected blades that have more than 8,000 hours since new on November 9, 2017 (the effective date of AD 2017-20-06). We therefore revised the applicability to refer to ``November 9, 2017,'' instead of ``the effective date of 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 as proposed.
Related Service Information Under 1 CFR Part 51
We reviewed Honeywell SB AS907-72-9067, Revision 1, dated March 20, 2017. This SB describes procedures for inspecting the LPT2 blades. 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.
Other Related Service Information
We reviewed Honeywell SB AS907-72-9067, Revision 0, dated December 12, 2016, which also describes procedures for inspecting the LPT2 blades. We also reviewed the Honeywell LMM AS907-1-1A, 72-00-00, Section 72-05-12, dated May 25, 2016, and Section 72-55-03, dated September 27, 2011, which provide additional guidance for performing borescope inspections.
Costs of Compliance
We estimate that this AD affects 40 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............... 10 work-hours x $85 per $0 $850 $34,000
hour = $850. Report results of inspection....... 1 work-hour x $85 per hour 0 85 3,400
= $85. ----------------------------------------------------------------------------------------------------------------
We estimate the following costs to do any necessary replacements thatwould be required based on the results of the inspection. We estimate that 40 engines will need this replacement.
On-Condition Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement of the LPT2 blade set.......... 50 work-hours x $85 per hour = $50,000 $54,250
$4,250. ----------------------------------------------------------------------------------------------------------------
Paperwork Reduction Act
A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120-0056. Public reporting for this collection of information is estimated to be approximately 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, completing and reviewing the collection of information. All responses to this collection of information are mandatory. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to: Information Collection Clearance Officer, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177-1524.
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
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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
We have 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 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.