Document headings vary by document type but may contain
                    the following: the agency or agencies that issued and signed a document
the number of the CFR title and the number of each part
                      the document amends, proposes to amend, or is directly
                      related to
the agency docket number / agency internal file number
the RIN which identifies each regulatory action listed in
                      the Unified Agenda of Federal Regulatory and Deregulatory
                      Actions See the
                    Document Drafting Handbook
                    for more details.
 Department of Transportation Federal Aviation Administration 14 CFR Part 39
[Docket No. FAA-2022-0600; Project Identifier AD-2021-01160-R; Amendment 39-22827; AD 2024-17-02]
RIN 2120-AA64
 AGENCY: Federal Aviation Administration (FAA), DOT.
 ACTION: Final rule.
 SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all Bell Textron Inc. (Bell) Model 204B, 205A, 205A-1, 205B, and 210 helicopters. This AD was prompted by an accident and incidents involving failure of the tail boom attachment structure. This AD requires inspecting the tail boom assembly hardware, replacing tail boom attachment hardware, greasing the bolt shanks, and inspecting torque. This AD also prohibits installing steel alloy nuts on any helicopter. The FAA is issuing this AD to address the unsafe condition on these products.
 DATES: This AD is effective November 8, 2024. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of November 8, 2024.
 ADDRESSES:  *AD Docket:*
                         You may examine the AD docket at 
                        *regulations.gov*
                         under Docket No. FAA-2022-0600; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. *Material Incorporated by Reference:* For Bell material identified in this AD, contact Bell Textron Inc., P.O. Box 482, Fort Worth, TX 76101; phone: (450) 437-2862 or (800) 363-8023; fax: (450) 433-0272; email:*productsupport@bellflight.com;*
                         website: 
                        *bellflight.com/support/contact-support.*
                    You may view this material at the FAA, Office of the Regional Counsel, Southwest Region, 10101 Hillwood Pkwy., Room 6N-321, Fort Worth, TX 76177. For information on the availability of this material at the FAA, call (817) 222-5110. *Other Related Material:*
                         For other material identified in this final rule, contact Bell Textron Inc., P.O. Box 482, Fort Worth, TX 76101; phone: (450) 437-2862 or (800) 363-8023; fax: (450) 433-0272; email: 
                        *productsupport@bellflight.com;*
                         website: 
                        *bellflight.com/support/contact-support.*
 FOR FURTHER INFORMATION CONTACT: Michael Perrin, Aviation Safety Engineer, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (562) 627-5362; email: 
                        *Michael.j.perrin@faa.gov*.


SUPPLEMENTARY INFORMATION: Background The FAA issued AD 2021-15-14, Amendment 39-21661 (86 FR 39942, July 26, 2021) (AD 2021-15-14) for various restricted category helicopters. AD 2021-15-14 was prompted by an accident involving a Model UH-1B helicopter and two forced landings involving Model UH-1H and UH-1F helicopters, due to tail boom attachment structure failures. Each of the three events involved a failure of the upper left-hand (LH) tail boom attachment fitting, which is the most heavily loaded of the four tail boom attach points. The FAA issued AD 2021-15-14 to address fatigue cracking of tail boom attachment fittings, cap angles, longerons, and bolts. Due to their similarity to Model UH-1B, UH-1H, and UH-1F helicopters, the FAA determined that Bell Model 204B, 205A, 205A-1, 205B, and 210 helicopters are also affected by the same unsafe condition and issued a notice of proposed rulemaking (NPRM) to propose the same actions as those required in AD 2021-15-14. The NPRM published in the 
                    **Federal Register**
                     on June 7, 2022 (87 FR 34587) to amend 14 CFR part 39 and would have applied to Bell Model 204B, 205A, 205A-1, 205B, and 210 helicopters. In the NPRM, the FAA proposed to require revising the helicopter's existing rotorcraft flight manual to incorporate pre-flight checks; removing excess paint and sealant and cleaning certain parts; and repetitively inspecting structural components that attach the tail boom to the fuselage. Depending on the inspection results, the FAA proposed to require repairing or replacing components or re-bonding the structure. Based on comments received on the NPRM, the FAA determined changes to the proposed required actions were necessary. Accordingly, the FAA issued a supplemental notice of proposed rulemaking (SNPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Bell Model 204B, 205A, 205A-1, 205B, and 210 helicopters. The SNPRM published in the 
                    **Federal Register**
                     on May 8, 2024 (89 FR 38846). In the SNPRM, for Bell Model 204B helicopters, the FAA proposed to require, with the tail boom assembly removed, removing the upper LH bolt from service and inspecting the bolt's associated attachment hardware and, depending on the inspection results, removing the associated nut from service. The FAA also proposed to require visually inspecting each bulkhead, bolt hole, attachment fitting, the three other nuts, the upper right-hand (RH) bolt, and two lower bolts, including the bolt shank and head radii. Depending on inspection results, the FAA proposed to require repairing or replacing an affected bulkhead or affected fitting, removing certain part-numbered nuts, removing any affected nut and its associated bolt from service, and removing any affected bolt from service. For Bell Model 205A, 205A-1, and 205B helicopters, the FAA proposed to require, with the tail boom assembly removed, removing the upper LH bolt from service and inspecting its associated barrel nut and retainer and, depending on the inspection results, removing barrel nut and retainer from service. The FAA also proposed to require visually inspecting each bulkhead, bolt hole, attachment fitting, the three other barrel nuts, associated retainers, the upper RH bolt, and two lower bolts, including the bolt shank and head radii. Depending on inspection results, the FAA proposed to require repairing or replacing an affected bulkhead or affected fitting, removing certain part-numbered barrel nuts and retainers, removing any affected barrel nuts and its associated bolt from service, and removing any affected bolt from service. For Bell Model 210 helicopters, the FAA proposed to require, with the tail boom supported, removing the upper LH steel alloy barrel nut, retainer, and bolt from service and removing the countersunk washer and plain washers and replacing them with a new certain part-numbered nickel alloy barrel nut, new retainer, new bolt, an airworthy countersunk washer, and airworthy plain washers. The FAA also proposed to require visually inspecting the upper RH bolt and its associated hardware and, depending on the inspection results, removing the upper RH bolt and barrel nut from service. Additionally, the FAA proposed to require visually inspecting the two lower bolts and the associated barrel nuts and, depending on the inspection results, removing any affected barrel nut and its associated 
                    ( print page 80735)
                    bolt from service and removing any affected bolt from service. For all applicable helicopters, the FAA proposed to require, after the initial inspections have been completed, applying a coating of grease to each bolt shank only, installing the applicable hardware, and torquing each bolt. Thereafter, the FAA proposed to require inspecting the torque applied on each bolt to determine if the torque has stabilized and, depending on the results, replacing and inspecting certain tail boom attachment point hardware and repeating the torque inspections or applying torque stripes. Lastly, the FAA proposed to prohibit installing certain part-numbered steel alloy nuts on Model 204B helicopters and certain part-numbered steel alloy barrel nuts on Model 205A, 205A-1, 205B, and 210 helicopters. Discussion of Final Airworthiness Directive Comments The FAA received comments on the SNPRM from Helicopter Maintenance Corporation. The commenter requested that the FAA revise the proposed AD to allow credit for previous compliance with the visual inspection of the tail boom attach points and bulkhead, replacement of affected hardware, and the recurring inspections involving removal of the tail boom. Helicopter Maintenance Corporation stated that aircraft that are in compliance with ASB 205-21-118 should only be obligated to comply with any differences between the AD and the alert service bulletin. Paragraph (f) of this AD requires compliance unless the actions have already been done. Therefore, where this AD requires actions without incorporating Bell Alert Service Bulletin (ASB) 210-21-15, Revision A, dated February 23, 2022 (ASB 210-21-15, Rev A), by reference, operators may take credit for those actions they if were done before the effective date of this AD. Also, where this AD requires actions in accordance with ASB 210-21-15, Rev A, operators may take credit for those actions only if they were done before the effective date of this AD using ASB 210-21-15, Rev A; this AD does not allow credit for those actions if previously done using the original release of ASB 210-21-15, (dated January 27, 2022). The FAA did not change this AD as a result of this comment. Conclusion The FAA reviewed the relevant data, considered any comments received, 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 SNPRM. Material Incorporated by Reference Under 1 CFR Part 51 The FAA reviewed Bell ASB 210-21-15, Rev A. This material specifies procedures for replacing the steel alloy barrel nuts with nickel alloy barrel nuts, inspecting and replacing the tail boom attachment hardware, stabilizing the tail boom attachment hardware torque, applying torque seals, and subsequently checking the torque. This material 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 Material The FAA also reviewed Bell ASB 205-21-118, Bell ASB 204B-21-75, and Bell ASB 205B-21-72, each Revision A and dated February 23, 2022. This material specifies the same procedures as ASB 210-21-15, Rev A. Differences Between This AD and the Related Material The related material specifies checking torque, whereas this AD requires inspecting torque because that action is a maintenance action that must be performed by persons authorized under 14 CFR 43.3. When stabilizing the tail boom attachment hardware torque, the related material does not clearly specify actions for each time the torque is below the minimum limit during any torque stabilization inspection, whereas this AD requires replacing and inspecting certain tail boom attachment point hardware, stabilizing the torque of the replaced hardware set, and applying torque stripes. Costs of Compliance The FAA estimates that this AD affects 62 (five Model 204B helicopters, fifty-three Model 205A, 205A-1, and 205B helicopters, and four Model 210 helicopters) of U.S. registry. Labor costs are estimated at $85 per work-hour. Based on these numbers, the FAA estimates the following costs to comply with this AD. For the initial requirements for Model 204B helicopters, inspecting or replacing up to four bolts (which includes applying a coating of grease), inspecting each bulkhead, inspecting each fitting and bolt hole, inspecting and stabilizing the torque, and applying torque stripes will take up to approximately 8.5 work-hours for an estimated labor cost of up to $723. The parts cost for an upper LH bolt will be approximately $196 and the parts cost for the other bolts will be approximately $89 per bolt. The parts cost for four new nuts will be approximately $680. The parts cost to apply torque stripes will be a nominal amount. The estimated cost for these actions will be up to approximately $1,866 per helicopter and $9,330 for the U.S. fleet. For the initial requirements for Model 205A, 205A-1, and 205B helicopters, replacing the four steel alloy barrel nuts with new nickel alloy barrel nuts, inspecting or replacing up to four bolts (which includes applying a coating of grease), inspecting each bulkhead, inspecting and stabilizing the torque, and applying torque stripes will take up to approximately 8.5 work-hours for an estimated labor cost of up to $723. The parts cost for the four new nickel alloy barrel nuts (including retainers) will be approximately $680. The parts cost for an upper LH bolt will be approximately $196 and the parts cost for the other bolts will be approximately $89 per bolt. The parts cost to apply torque stripes will be a nominal amount. The estimated cost for these actions will be up to approximately $1,866 per helicopter and $98,898 for the U.S. fleet. For the initial requirements for Model 210 helicopters, replacing the four steel alloy barrel nuts with new nickel alloy barrel nuts, inspecting or replacing up to four bolts (which includes applying a coating of grease), inspecting and stabilizing the torque, and applying torque stripes will take up to approximately 8.5 work-hours for an estimated labor cost of up to $723. The parts cost for the four new nickel alloy barrel nuts (including retainers) will be approximately $680. The parts cost for an upper LH bolt will be approximately $196 and the parts cost for the other bolts will be approximately $89 per bolt. The parts cost to apply torque stripes will be a nominal amount. The estimated cost for these actions will be up to approximately $1,866 per helicopter and $7,464 for the U.S. fleet. For all applicable helicopters, inspecting the torque applied on each bolt will take approximately 1 work-hour for an estimated cost of $85 per helicopter and $5,270 for the U.S. fleet, per inspection cycle. For all applicable helicopters, replacing an upper LH bolt, stabilizing the torque, and applying a torque stripe will take up to approximately 5 work-hours. The parts cost for an upper LH bolt will be approximately $196 and the parts cost to apply a torque stripe will 
                    ( print page 80736)
                    be a nominal amount. The estimated cost for these actions will be up to approximately $621 per helicopter and $38,502 for the U.S. fleet, per replacement cycle. Inspecting one of the other bolts, stabilizing the torque, and applying a torque stripe will take up to approximately 3.5 work-hours for an estimated cost of $298 per other bolt and $18,476 for the U.S. fleet per other bolt per inspection cycle. If required, replacing a bolt following that inspection will take a minimal amount of additional time and the parts cost will be approximately $89. If required as a result of failing any torque inspection required by this AD, visually inspecting a nut or a barrel nut, replacing a bolt, stabilizing the torque, and applying a torque stripe will take up to approximately 5.5 work-hours per failed hardware set. The parts cost for an upper LH bolt will be approximately $196 and the parts cost for the other bolts will be approximately $89 per bolt. The parts cost to apply a torque stripe will be a nominal amount. The estimated cost for these actions will be $664 (upper LH bolt) or $557 (other bolts), per failed hardware set. If required, replacing a nut following that inspection will take a minimal amount of additional time and the parts cost for a nut will be approximately $89 per nut. If required, replacing a barrel nut following that inspection will take a minimal amount of additional time and a parts cost of approximately $173 per barrel nut. The corrective action that may be needed as a result of the bulkhead inspection could vary significantly from helicopter to helicopter. The FAA has no data to determine the costs to accomplish the corrective action or the number of helicopters that may require corrective action. 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. 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 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) Will not affect intrastate aviation in Alaska, and (3) 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
 The Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: PART 39—AIRWORTHINESS DIRECTIVES
 1.The authority citation for part 39 continues to read as follows: Authority:
                        49 U.S.C. 106(g), 40113, 44701. § 39.13
 2.The FAA amends § 39.13 by adding the following new airworthiness directive: **2024-17-02 Bell Textron Inc.:**
                             Amendment 39-22827; Docket No. FAA-2022-0600; Project Identifier AD-2021-01160-R. (a) Effective Date This airworthiness directive (AD) is effective November 8, 2024. (b) Affected ADs None. (c) Applicability This AD applies to Bell Textron Inc. Model 204B, 205A, 205A-1, 205B, and 210 helicopters, certificated in any category. (d) Subject Joint Aircraft System Component (JASC) 5302, Rotorcraft Tail Boom. (e) Unsafe Condition This AD was prompted by an accident and incidents involving failure of the tail boom attachment structure. The FAA is issuing this AD to address fatigue cracking of tail boom attachment fittings, cap angles, longerons, and bolts. The unsafe condition, if not addressed, could result in separation of the tail boom from the helicopter and subsequent loss of control of the helicopter. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Allowable Torque Values (in-lbs) Tail boom attachment point
Model 204B
Model 205A/205A-1
Model 205B
Model 210Upper left-hand bolt
570-610
1000-1200
1000-1200
1300-1600Upper right-hand bolt
360-380
1000-1200
1000-1200
1000-1200Lower left-hand bolt
360-380
400-430
400-430
400-430Lower right-hand bolt
360-380
400-430
400-430
400-430
 (h) Required Actions (1) Within 300 hours time-in-service (TIS) or 90 days after the effective date of this AD, whichever occurs first, accomplish the actions required by paragraphs (h)(1)(i), (ii), or (iii) of this AD as applicable to your model helicopter. For purposes of this AD, the word “new” is defined as having zero total hours TIS. (i) For Model 204B helicopters, accomplish the actions required by paragraphs (h)(1)(i)(A) through (C) of this AD. (A) With the tail boom assembly removed, remove the upper left-hand (LH) tail boom attachment bolt (bolt) from service and inspect its associated tail boom attachment nut (nut) for mechanical damage, corrosion, a crack, damaged threads, and wear, and to determine whether it is a steel alloy part number (P/N) NAS679A, NAS1291, or MS21042. If there is any mechanical damage, corrosion, a crack, a damaged thread, or wear, or if nut P/N NAS679A, NAS1291, or MS21042 is installed, before further flight, remove the nut from service. (B) Visually inspect each bulkhead (FS 195.00 and FS 195.03) and the bolt holes for mechanical damage, corrosion, and cracks; visually inspect each attachment fitting for 
                            ( print page 80737)
                            mechanical damage, corrosion, cracks, and loose fasteners; determine if any of the three other nuts are a steel alloy P/N NAS679A, NAS1291, or MS21042; and visually inspect the other three nuts, the upper right-hand (RH) bolt, and two lower bolts for mechanical damage, corrosion, cracks, damaged threads, and wear, including the bolt shank and head radii of the bolts for a damaged thread, wear, and mechanical damage. (
                            *1*) If there is any mechanical damage, corrosion, or cracks on any bulkhead (FS 195.00 or FS 195.03), or any mechanical damage, corrosion, or cracks on any bolt holes, or if there is any mechanical damage, corrosion, cracks, or loose fasteners on any attachment fitting, before further flight, repair or replace the affected bulkhead or the affected attachment fitting, as appropriate, in accordance with FAA-approved procedures. (
                            *2*) If there is any mechanical damage, corrosion, a crack, a damaged thread, or wear on any nut, or if nut P/N NAS679A, NAS1291, or MS21042 is installed, before further flight, remove the affected nut from service. If there is a crack on any nut, before further flight, also remove its associated bolt from service. (
                            *3*) If there is any mechanical damage, corrosion, a crack, a damaged thread, or wear on the on the upper RH bolt or two lower bolts, which includes the bolt shank or head radii, before further flight, remove the affected bolt from service. (C) Apply a coating of Aeriol ThixO #2 (3810-0) or Aeriol ThixO SYN (3820-0) aviation grease to each bolt shank only. Install the hardware set of each tail boom attachment point (nickel alloy nut P/N 90-132L7 or 90-132L6, as applicable to the affected tail boom attachment point, new upper LH bolt P/N NAS627-21, upper RH and two lower bolts P/N NAS626-20, countersunk washer, and plain washers). Torque each bolt by using the torque value information identified in paragraph (g) of this AD. (ii) For Model 205A, 205A-1, and 205B helicopters, accomplish the actions required by paragraphs (h)(1)(ii)(A) through (C) of this AD. (A) With the tail boom assembly removed, remove the upper LH bolt from service and inspect its associated tail boom attachment barrel nut (barrel nut) and retainer for mechanical damage, corrosion, a crack, damaged threads, and wear, and to determine whether it is a steel alloy barrel nut P/N NAS577B8A. If there is any mechanical damage, corrosion, a crack, a damaged thread, or wear, or if barrel nut P/N NAS577B8A is installed, before further flight, remove the barrel nut and its associated retainer from service. (B) Visually inspect each bulkhead (BS 17.31 and FS 243.89) and the bolt holes for mechanical damage, corrosion, and cracks; visually inspect each attachment fitting for mechanical damage, corrosion, cracks, and loose fasteners; determine if any of the three other barrel nuts are steel alloy P/N NAS577B8A or P/N NAS577B6A; and visually inspect the other three barrel nuts and the associated retainers, the upper RH bolt, and two lower bolts for mechanical damage, corrosion, cracks, damaged threads, and wear, including the bolt shank and head radii of the bolts for a damaged thread, wear, and mechanical damage. (
                            *1*) If there is any mechanical damage, corrosion, or cracks on any bulkhead (BS 17.31 or FS 243.89), or any mechanical damage, corrosion, or cracks on any bolt holes, or if there is any mechanical damage, corrosion, cracks, or loose fasteners on any attachment fitting, before further flight, repair or replace the affected bulkhead or the affected attachment fitting, as appropriate, in accordance with FAA-approved procedures. (
                            *2*) If there is any mechanical damage, corrosion, a crack, a damaged thread, or wear on any barrel nut or retainer, or if barrel nut P/N NAS577B8A or NAS577B6A is installed, before further flight, remove the affected barrel nut and retainer (as a pair) from service. If there is a crack on any nut, before further flight, also remove its associated bolt from service. (
                            *3*) If there is any mechanical damage, corrosion, a crack, a damaged thread, or wear on the upper RH bolt or two lower bolts, which includes the bolt shank or head radii, before further flight, remove the affected bolt from service. (C) Apply a coating of Aeriol ThixO #2 (3810-0) or Aeriol ThixO SYN (3820-0) aviation grease to each bolt shank only. Install the hardware set of each tail boom attachment point (nickel alloy barrel nut P/N NAS577C6A or P/N NAS577C8A and retainer P/N NAS578C6A or P/N NAS578C8A, as applicable to the affected tail boom attachment point, new upper LH bolt P/N NAS628-22, upper RH and two lower bolts P/N NAS628-22 or NAS626-18, as applicable to the affected tail boom attachment point, countersunk washer, and plain washers). Torque each bolt by using the torque value information identified in paragraph (g) of this AD. (iii) For Model 210 helicopters, accomplish the actions required by paragraphs (h)(1)(iii)(A) through (C) of this AD. (A) With the tail boom supported, remove the upper LH bolt, and the steel alloy barrel nut P/N NAS577B9A, including the retainer, from service. Remove the countersunk washer, and plain washers, and install new nickel alloy barrel nut P/N NAS577C9A, new retainer P/N NAS578C9A, airworthy countersunk washer, airworthy plain washers, and a new bolt in accordance with the Accomplishment Instructions, Part I, paragraphs 5 through 7 of Bell Alert Service Bulletin (ASB) 210-21-15, Revision A, dated February 23, 2022 (ASB 210-21-15, Rev A). (B) Remove the upper RH bolt, steel alloy barrel nut P/N NAS577B8A, countersunk washer, and plain washers. Visually inspect the upper RH bolt for any corrosion, damaged threads, wear, and fatigue cracking. If the upper RH bolt has any corrosion, damaged threads, wear, or fatigue cracking, before further flight, remove the upper RH bolt from service. Visually inspect the removed barrel nut for cracking. If there is any cracking in the barrel nut, before further flight, remove the upper RH bolt from service. Regardless of the result of the upper RH steel alloy barrel nut inspection, replace the barrel nut with a new nickel alloy barrel nut P/N NAS577C8A and new retainer P/N NAS578C8A. Install a new upper RH bolt or reinstall the existing upper RH bolt (if no cracks in the barrel nut, and no corrosion, damaged threads, wear, or fatigue cracking in the bolt were identified), by following the Accomplishment Instructions, part I, paragraphs 11 and 12, including the caution above paragraph 11, of ASB 210-21-15, Rev A. (C) Remove one of the lower bolts, its lower steel alloy barrel nut P/N NAS577B6A, countersunk washer, and plain washers. Visually inspect that lower bolt for any corrosion, damaged threads, wear, and fatigue cracking. If the lower bolt has any corrosion, damaged threads, wear, or fatigue cracking, before further flight, remove the lower bolt from service. Visually inspect the removed lower barrel nut for cracking. If there is any cracking in the lower barrel nut, before further flight, remove the lower bolt from service. Regardless of the result of that lower steel alloy barrel nut inspection, replace the barrel nut with a new nickel alloy barrel nut P/N NAS577C6A and new retainer P/N NAS578C6A. Install a new lower bolt or reinstall the existing lower bolt (if no cracks in the barrel nut, and no corrosion, damaged threads, wear, or fatigue cracking in the bolt were identified), by following the Accomplishment Instructions, part I, paragraphs 16 through 17, including the caution above paragraph 16, of ASB 210-21-15, Rev A. Repeat the actions required by this paragraph for the other lower attachment point. (2) After accumulating 1 hour TIS, but not to exceed 5 hours TIS, after accomplishing the actions required by paragraph (h)(1) of this AD, using the torque value information identified in paragraph (g) of this AD applicable to your model helicopter, inspect the torque applied on each bolt. Thereafter, repeat the torque inspection of each bolt after accumulating 1 hour TIS, but not to exceed 5 hours TIS, to determine if the torque has stabilized. Do not exceed three torque inspections total for each bolt and accomplish the actions required by paragraphs (h)(2)(i) and (ii) of this AD. (i) If the torque on a bolt is below the minimum allowable torque limit as a result of any instance of the torque inspection or if after three torque inspection attempts, the torque on any bolt has not stabilized, before further flight, accomplish the actions required by paragraphs (h)(2)(i)(A) and (B) of this AD. (A) Remove the hardware set of one failed tail boom attachment point (nut, bolt, countersunk washer, and plain washers for Model 204B helicopters, and barrel nut, bolt, retainer, countersunk washer, and plain washers for Model 205A, 205A-1, 205B, and 210 helicopters). For Model 204B helicopters, remove the nut from service and for Model 205A, 205A-1, 205B, and 210 helicopters, remove the barrel nut and retainer from service as applicable to the affected tail boom attachment point. Visually inspect the removed bolt for any corrosion, damaged threads, wear, and fatigue cracking. If the bolt has any corrosion, a damaged thread, wear, or fatigue cracking, before further flight, remove the bolt from service. (B) Apply a coating of Aeriol ThixO #2 (3810-0) or Aeriol ThixO SYN (3820-0) 
                            ( print page 80738)
                            aviation grease to the bolt shank only. Install a new bolt or reinstall the existing bolt (if no corrosion, damaged threads, wear, or fatigue cracking in the bolt were identified) and the hardware set of the affected tail boom attachment point (new nut P/N 90-132L6 or 90-132L7, countersunk washer, and plain washers for Model 204B helicopters, and new nickel alloy barrel nut P/N NAS577C6A, NAS577C8A or P/N NAS577C9A and new retainer P/N NAS578C6A, NAS578C8A, or P/N NAS577C9A, countersunk washer, and plain washers for Model 205A, 205A-1, 205B, and 210 helicopters), as applicable to the affected tail boom attachment point. Torque the bolt by using the torque value information identified in paragraph (g) of this AD. Repeat the actions required by paragraphs (h)(2)(i)(A) and (B) of this AD for each failed tail boom attachment point, one hardware set at a time. Then repeat the actions required by paragraph (h)(2) of this AD just for each newly installed or reinstalled bolt until the torque for all four tail boom attachment points stabilize. (ii) If the torque for all four tail boom attachment points has stabilized, before further flight, apply a torque stripe to all four bolts. (3) Within 600 hours TIS or 12 months, whichever occurs first after applying torque stripes to all four bolts as required by paragraph (h)(2)(ii) of this AD, and thereafter within intervals not to exceed 600 hours TIS or 12 months, whichever occurs first, inspect the torque applied on each bolt using the torque value information identified in paragraph (g) of this AD, as applicable to your model helicopter. If the torque on any bolt is below the minimum allowable torque limit, accomplish the actions required by paragraphs (h)(3)(i) and (ii) of this AD. (i) Before further flight, remove the hardware set of one failed tail boom attachment point (nut, bolt, countersunk washer, and plain washers for Model 204B helicopters, and barrel nut, retainer, bolt, countersunk washer, and plain washers for Model 205A, 205A-1, 205B, and 210 helicopters) and then accomplish the actions required by paragraphs (h)(3)(i)(A), (B), or (C) of this AD as applicable to your model helicopter. (A) For Model 204B helicopters, visually inspect the removed nut for cracking, corrosion, and loss of tare torque. If the nut has any cracking, corrosion, or loss of tare toque, before further flight, remove the nut from service and replace with a new nut P/N 90-132L7 or 90-132L6 as applicable to the tail boom attachment point. Regardless of the result of the nut inspection, remove the bolt from service and replace it with a new bolt by applying a coating of Aeriol ThixO #2 (3810-0) or Aeriol ThixO SYN (3820-0) aviation grease to the bolt shank only, and install the hardware set of the tail boom attachment point (nut, bolt, and countersunk washer, and plain washers). Torque each bolt by using the torque value information identified in paragraph (g) of this AD. Repeat the actions required by this paragraph for each failed tail boom attachment point, one hardware set at a time. (B) For Model 205A, 205A-1, and 205B helicopters, visually inspect the removed barrel nut for cracking, corrosion, and loss of tare torque. If the barrel nut has any cracking, corrosion, or loss of tare toque, before further flight, remove the barrel nut and retainer from service and replace them with a new nickel alloy barrel nut P/N NAS577C6A, or NAS577C8A, and new retainer P/N NAS578C6A, or NAS578C8A, with the P/N of the new nickel alloy barrel nut and the P/N of the new retainer being as applicable to the affected tail boom attachment point. Regardless of the result of the barrel nut inspection, remove the bolt from service and replace it with a new bolt. Apply a coating of Aeriol ThixO #2 (3810-0) or Aeriol ThixO SYN (3820-0) aviation grease to each bolt shank only. Install the hardware set of each tail boom attachment point (nickel alloy barrel nut, retainer, bolt, countersunk washer, and plain washers). Torque each bolt by using the torque value information identified in paragraph (g) of this AD. Repeat the actions required by this paragraph for each failed tail boom attachment point, one hardware set at a time. (C) For Model 210 helicopters, visually inspect the removed barrel nut for cracking, corrosion, and loss of tare torque. If the barrel nut has any cracking, corrosion, or loss of tare toque, before further flight, remove the barrel nut and retainer from service and replace them with a new nickel alloy barrel nut P/N NAS577C6A, NAS577C8A, or NAS577C9A, and new retainer P/N NAS578C6A, NAS578C8A, or NAS578C9A, with the P/N of the new nickel alloy barrel nut and the P/N of the new retainer being as applicable to the affected tail boom attachment point. Regardless of the result of the barrel nut inspection, remove the bolt from service and replace it with a new bolt, apply a coating of Aeriol ThixO #2 (3810-0) or Aeriol ThixO SYN (3820-0) aviation grease to each bolt shank only, and torque each bolt by using the torque value information identified in paragraph (g) of this AD. Repeat the actions required by this paragraph for each failed tail boom attachment point, one hardware set at a time. (ii) After accumulating 1 hour TIS, but not to exceed 5 hours TIS after accomplishing the actions required by paragraph (h)(3)(i) of this AD, using the torque value information identified in paragraph (g) of this AD as applicable to your model helicopter, inspect the torque applied on each newly installed bolt. Thereafter, repeat the torque inspection of those bolts after accumulating 1 hour TIS, but not to exceed 5 hours TIS, to determine if the torque has stabilized. Do not exceed three torque inspections total for those bolts and accomplish the actions required by paragraphs (h)(2)(i) and (ii) of this AD. (4) Within 5,000 hours TIS or 5 years after accomplishing the actions required by paragraph (h)(1) of this AD, whichever occurs first, and thereafter within intervals not to exceed 5,000 hours TIS or 5 years, whichever occurs first, accomplish the actions required by paragraphs (h)(4)(i) and (ii) of this AD. (i) Accomplish the actions required by paragraphs (h)(1)(i), (ii), or (iii) of this AD, as applicable to your model helicopter. (ii) After accumulating 1 hour TIS, but not to exceed 5 hours TIS after accomplishing the actions required by paragraph (h)(4)(i) of this AD, using the torque value information identified in paragraph (g) of this AD as applicable to your model helicopter, inspect the torque applied on each bolt. Thereafter, repeat the torque inspection of those bolts after accumulating 1 hour TIS, but not to exceed 5 hours TIS, to determine if the torque has stabilized. Do not exceed three torque inspections total for those bolts and accomplish the actions required by paragraphs (h)(2)(i) and (ii) of this AD. (5) As of the effective date of this AD, do not install the following parts identified in paragraphs (h)(5)(i) and (ii) of this AD on any helicopter. (i) For Model 204B helicopters: steel alloy nut P/N NAS679A, NAS1291, or MS21042. (ii) For Model 205A, 205A-1, 205B, and 210 helicopters: steel alloy barrel nut P/N NAS577B9A, P/N NAS577B8A, or P/N NAS577B6A. (i) Special Flight Permit A one-time special flight permit may be issued in accordance with 14 CFR 21.197 and 21.199 in order to fly to a maintenance area to perform the required actions in this AD. (j) Alternative Methods of Compliance (AMOCs) (1) The Manager, Central Certification Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the certification office, send it to the attention of the person identified in paragraph (k) of this AD. Information may be emailed to 
                            *AMOC@faa.gov.* (2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office. (k) Related Information For more information about this AD, contact Michael Perrin, Aviation Safety Engineer, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (562) 627-5362; email: 
                            *Michael.j.perrin@faa.gov.* (l) Material Incorporated by Reference (1) The Director of the Federal Register approved the incorporation by reference of the material listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51. (2) You must use this material as applicable to do the actions required by this AD, unless the AD specifies otherwise. (i) Bell Alert Service Bulletin 210-21-15, Revision A, dated February 23, 2022. (ii) [Reserved] (3) For Bell material identified in this AD, contact Bell Textron Inc., P.O. Box 482, Fort Worth, TX 76101; phone: (450) 437-2862 or (800) 363-8023; fax: (450) 433-0272; email: 
                            *productsupport@bellflight.com;*
                             website: 
                            *bellflight.com/support/contact-support.* (4) You may view this material at the FAA, Office of Regional Counsel, Southwest Region, 10101 Hillwood Pkwy., Fort Worth, TX 76177. For information on the availability 
                            ( print page 80739)
                            of this material at the FAA, call: (817) 222-5110. (5) You may view this material at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, visit 
                            *www.archives.gov/​federal-register/​cfr/​ibr-locations*
                             or email 
                            *fr.inspection@nara.gov*. Issued on September 27, 2024. Victor Wicklund, Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.


[FR Doc. 2024-22908 Filed 10-3-24; 8:45 am] BILLING CODE 4910-13-P