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Federal Register / Vol. 86, No. 231 / Monday, December 6, 2021 / Rules and Regulations 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters, with torque tube part number 369H75319/
11/13, installed. The NPRM published in the Federal Register on August 13, 2021 86 FR 44652. In the NPRM, the FAA proposed to initially require visually inspecting the torque tube exterior using a flashlight and mirror and borescope inspecting the interface of the torque tube and bushing segments for a crack, elongation, and other damage, which may be indicated by any corrosion, pitting, crazing, dents, dings, displacement of material at the bolt hole edge, or fretting of the hole. Thereafter, the NPRM proposed to require repeating the borescope inspection. If there is a crack, elongation, or other damage, the NPRM proposed to require removing the torque tube from service. The NPRM
was prompted by a report of a spiral crack in the torque tube that appears to have originated from a hole where the tail rotor torque tube control fitting attaches to the torque tube on a Model 369FF helicopter. This crack resulted in increased left pedal movement and subsequent reduced directional control pedal authority. Other model helicopters are affected due to design similarity. This condition, if not addressed, could result in failure of the torque tube, loss of tail rotor control, and subsequent loss of control of the helicopter.
Discussion of Final Airworthiness Directive
khammond on DSKJM1Z7X2PROD with RULES

Comments The FAA received no comments on the NPRM or on the determination of the costs.
Conclusion The FAA reviewed the relevant data and determined that air safety requires adopting this AD as proposed.
Accordingly, the FAA is issuing this AD
to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the NPRM. The minor editorial changes include updating the cross reference in Note 2 from paragraph g1ii to paragraph g1ii of this AD, and deleting paragraph i No Reporting Requirement of the published NPRM because it is unnecessary. As a result of deleting that paragraph, some paragraph identifiers have changed.
Related Service Information Under 1
CFR Part 51
The FAA reviewed MD Helicopters Service Bulletin SB369D229R2 for Model 369D helicopters, SB369E129R2
for Model 369E helicopters, SB369F

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119R2 for Model 369F and 369FF
helicopters, SB369H263R2 for Model 369H, 369HE, 369HM, and 369HS
helicopters, SB500N066R2 for Model 500N helicopters, and SB600N080R2
for Model 600N helicopters, each dated March 24, 2021 co-published as one document and collectively referred to as Revision 2. This service information specifies procedures for a one-time visual inspection and recurring borescope inspections, completing a Service Operation Report, and returning a removed torque tube to an authorized service center or MDHI.
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 ADDRESSES.
Other Related Service Information The FAA also reviewed MD
Helicopters Service Bulletin SB369H
263, SB369D229, SB369E129, SB369F119, SB500N066, and SB600N080, each dated January 30, 2020 co-published as one document and collectively referred to as initial issuance, and MD Helicopters Service Bulletin SB369H263R1, SB369D
229R1, SB369E129R1, SB369F119R1, SB500N066R1, and SB600N080R1, each dated May, 15 2020 co-published as one document and collectively referred to as Revision 1. The initial issuance and Revision 1 of this service information specify the same procedures as Revision 2 of this service information, except Revision 1 clarified the torque value to apply to the nut and Revision 2 deletes Method 2 of the Accomplishment Instructions and adds a recurring 300-hour borescope inspection of the torque tube.
Differences Between This AD and the Service Information For helicopters that have accumulated 600 or less total hours time-in-service TIS, Revision 2 of the service information specifies an initial compliance time of during the next 100hour inspection, whereas this AD
requires initial actions within 100 hours TIS after the effective date of this AD
instead. For helicopters that have accumulated more than 600 total hours TIS, Revision 2 of the service information specifies an initial compliance time of within 5 hours of flight time, whereas this AD requires initial actions within 5 hours TIS or 30
days after the effective date of this AD, whichever occurs later, instead.
Revision 2 of the service information specifies returning a removed torque tube, whereas this AD requires removing the torque tube from service
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instead. Revision 2 of the service information specifies completing a Service Operation Report, whereas this AD does not include that requirement.
Costs of Compliance The FAA estimates that this AD
affects 58 helicopters of U.S. Registry.
Labor rates are estimated at $85 per work-hour. Based on these numbers, the FAA estimates the following costs to comply with this AD.
Visually inspecting the torque tube takes a minimal amount of time.
Borescope inspecting the torque tube takes about 1 work-hour for an estimated cost of $85 per helicopter and $4,930 for the U.S. fleet, per inspection cycle.
If required, replacing the torque tube takes about 5 work-hours and parts cost about $983 for an estimated cost of $1,408 per helicopter.
The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected operators.
Authority for This Rulemaking Title 49 of the United States Code specifies the FAAs 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 Agencys authority.
The FAA is 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 helicopters 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,
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