Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Honeywell International Inc. TPE331 turboprop and TSE331 turboshaft engines. The NPRM published in the Federal Register on September 13, 2017 (82 FR 42957). The NPRM was prompted by recent reports of failures of the direct drive fuel control gears and bearings in the hydraulic torque sensor gear assembly, P/N 3101726-3. The NPRM proposed to require initial and repetitive engine oil filter sampling and analysis of the affected engines. The NPRM also proposed to require inspection of the hydraulic torque sensor gear assemblies that do not meet oil filter inspection requirements and improved component overhaul procedures that would remove from service, by attrition, certain P/N hydraulic torque sensor gear assemblies. 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 final rule. The following presents the comments received on the NPRM and the FAA's response to each comment.
Request To Revise Compliance Time for Resampling
The National Agricultural Aviation Association (NAAA) commented that additional compliance time may be required for oil filter analysis resampling beyond the 25 hours time-in-service proposed by the NPRM. The NAAA noted that the engine may re-enter service after oil sampling. Therefore, the 25 hours time-in-service may be exceeded prior to the operators receiving notification from the laboratory that performed the oil filter analysis.
We agree that the proposed compliance time may have resulted in operators exceeding the 25 hours time-in-service before receiving the results of the oil filter analysis. We, therefore, revised the requirement time for resampling in this AD to 25 hours time in service after receiving notification from the accredited laboratory performing the oil filter analysis. We determined that allowing this additional time in service will improve the quality of the sample. We also clarified that if an inspection or resample is required, then the inspection must occur within 5 days after receiving notification from the laboratory that performed the oil filter analysis.
Request To Revise Compliance Time for Initial Sample
Honeywell requested that we increase the compliance time for obtaining an oil filter sample from 150 to 200 hours. Honeywell commented that Honeywell Service Bulletin (SB) TPE331-72-0180 indicates a 200-hours compliance time for TPE331-10 operators with at least 800 operating hours per year. Honeywell noted that this compliance time coincides with scheduled maintenance intervals for operators.
We disagree. We are attempting to detect impending torque sensor failures using set response times and reduced oil filter sampling and analysis intervals. We find, therefore, that the 150-hour compliance timemeets the safety objectives of this AD. Further, we did not receive any comments from part 121
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or part 135 operators indicating a concern with the inspection interval of 150 hours. We did not change this AD.
Request To Revise Number of Resampling Tests
NAAA and Copperstate Turbine Engine Company commented that a single resampling allowance that may lead to a gearbox inspection is too stringent. They indicated that oil filter resampling experience has shown that multiple resampling tests may be necessary. NAAA commented that the source of the contamination may not always be the material caused by the torque sensor failure. In this situation, NAAA indicated that another resampling, without the inspection, may be warranted. NAAA commented that the sample analysis should guide maintenance personnel in the proper direction without having to tear down an engine unnecessarily.
We partially agree. We agree that some wear elements, such as silver and aluminum, found during the initial oil filter analysis could permit more than one resampling before a required gearbox inspection. We also agree because these elements or alloys may not cause accelerated wear and possible failure of the torque sensor assembly. We disagree with changing the AD because the commenters have not produced evidence that the presence of certain elements may not contribute to the failure of the torque sensor. We will consider AMOC requests to allow additional oil filter resamples before requiring a gearbox inspection provided we receive acceptable technical justification. We did not change this AD.
Request To Update Service Information
Honeywell requested that we revise our reference to the service bulletin to refer to the latest revision.
We agree. We updated the reference in the Other Related Service Information paragraph in this AD to Revision 38 of Honeywell SB TPE331- 72-0180.
Request To Clarify Differences Paragraph
Honeywell requestedthat we clarify the ``Differences Between This Proposed AD and the Service Information'' section in the NPRM.
We disagree. The referenced paragraph does not exist in the final rule and the compliance requirements were clearly defined in the NPRM. 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 final rule with the changes described previously and minor editorial changes. We have determined that these minor changes:
[Agr]re consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was already proposed in the NPRM.
We also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule.
Related Service Information Under 1 CFR Part 51
We reviewed Honeywell Service Information Letter (SIL) P331-97, Revision 11, dated July 23, 2008. The SIL describes procedures for conducting the spectrometric oil and filter analysis program to sample and analyze metal particles in the engine lubricating system. 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 the improved procedures and limitations in the Honeywell Torque Sensor Gear Assembly Overhaul Manual with Illustrated Parts List, 72-00-17, Revision 10, dated October 31, 2013, for the TPE331 and TSE331 torque sensor gear assemblies. We also reviewed Honeywell's TPE331 Line Maintenance Training Manual which provides guidance for obtaining oil filter samples. In addition, we reviewed Honeywell SBs TPE331-72-0402, Revision 6, dated November 26, 1997; TPE331-72-0403, Revision 5, dated January 20, 1989; TPE331-72-0404, Revision 8, dated September 13, 2016; TPE331-72-0823, Revision 3, dated September 13, 1996; TSE331-72-5003, Revision 3, dated January 20, 1989; and TPE331-72-0180, Revision 38, dated August 15, 2017. The SBs address the inspection intervals for the oil and filter analysis for the affected TPE331 and TSE331 engines.
Costs of Compliance
We estimate that this AD affects 3,831 engines installed on airplanes of U.S. registry. We estimate the following costs to comply with this AD:
We estimate that 3,831 engines will require a records review to determine if they have an affected hydraulic torque sensor gear assembly installed.
Estimated Costs ----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Records review........................ 1 work-hour x $85 per $0 $85 $325,635
hour = $85. ----------------------------------------------------------------------------------------------------------------
We estimate that 2,542 engines operating under Parts 121 or 135 and 544 engines operating under Part 91 will be required to perform oil filter sampling and analysis.
Estimated Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product Cost on U.S. operators ---------------------------------------------------------------------------------------------------------------- Oil filter sampling and 4 work-hours x $85 $844 $1,184 $644,096 per year.
analysis: Part 91 operators. per hour = $340. Oil filter sampling and 1 work-hour x $85211 296 $752,432 per year.
analysis: Part 121 and 135 per hour = $85.
operators. ----------------------------------------------------------------------------------------------------------------
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We estimate that 242 engines will require that the hydraulic torque sensor gear assembly be overhauled during the first year of inspection.
Estimated Overhaul Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replace or overhaul hydraulic torque sensor 10 work-hours x $85 per hour = $10,000 $10,850
gear assembly. $850. ----------------------------------------------------------------------------------------------------------------
We estimate that 217 engines will require hydraulic torque sensor gear assembly inspection after an unacceptable oil filter analysis during the first year of inspection.
On-Condition Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Inspect and reassemble hydraulic torque sensor 5 work-hours x $85 per hour = $3,000 $3,425
gear assembly. $425. ----------------------------------------------------------------------------------------------------------------
Paperwork Reduction Act
A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shalla person be subject to 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 current valid OMB control number. The control number for the collection of information required by this AD is 2120- 0056. The paperwork cost associated with this AD has been detailed in the Costs of Compliance section of this document and includes time for reviewing instructions, as well as completing and reviewing the collection of information. Therefore, all reporting associated with this AD is mandatory. Comments concerning the accuracy of this burden and suggestions for reducing the burden should be directed to the FAA at 800 Independence Ave. SW, Washington, DC 20591. ATTN: Information Collection Clearance Officer, AES-200.
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 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 ofthe Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.