Airworthiness Directives; Bell Textron Inc. Helicopters

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 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 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.

The Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

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)