2024-03081. Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for certain De Havilland Aircraft of Canada Limited Model DHC–8–401 and –402 airplanes. This AD was prompted by reports that the saddle washer (radius filler) for the front and rear spar joints may have been incorrectly manufactured for several years. This AD requires inspecting the horizontal stabilizer to vertical joint for gaps and bending of the saddle washer and adjacent washers, and replacing parts if necessary. The FAA is issuing this AD to address the unsafe condition on these products.

DATES:

This AD is effective March 21, 2024.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of March 21, 2024.

ADDRESSES:

AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA–2023–0933; 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, the mandatory continuing airworthiness information (MCAI), 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 service information identified in this final rule, contact De Havilland Aircraft of Canada Limited, Dash 8 Series Customer Response Centre, 5800 Explorer Drive, Mississauga, Ontario, L4W 5K9, Canada; telephone [phone] or 647–277–5820; email [e-mail]; website dehavilland.com.

• You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th Street, Des Moines, WA. For information on the availability of this material at the FAA, call 206–231–3195. It is also available at regulations.gov under Docket No. FAA–2023–0933.

FOR FURTHER INFORMATION CONTACT:

Yaser Osman, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone [phone]; email [e-mail].

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain De Havilland Aircraft of Canada Limited Model DHC–8–401 and –402 airplanes. The NPRM published in the Federal Register on April 19, 2023 (88 FR 24144). The NPRM was prompted by AD CF–2022–21, dated April 21, 2022, issued by Transport Canada, which is the aviation authority for Canada (referred to after this as the MCAI). The MCAI states that certain saddle washers for the front and rear spar joint may have been incorrectly manufactured for several years. Non-conforming saddle washers could potentially become deformed when installed, and lead to gaps at the horizontal stabilizer to vertical stabilizer joint, that would result in reduction of the pre-load at the joint.

In the NPRM, the FAA proposed to require inspecting the horizontal stabilizer to vertical joint for gaps and bending of the saddle washer and adjacent washers, and replacing parts if necessary. The FAA is issuing this AD to address gapping and bending of the saddle washer that could have the potential to reduce the life of the bolt, which in turn could affect the structural integrity of the horizontal stabilizer to vertical stabilizer joint.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA–2023–0933.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from the Air Line Pilots Association, International (ALPA). ALPA supported the NPRM without change.

The FAA received additional comments from De Havilland Aircraft of Canada Limited. The following presents the comments received on the NPRM and the FAA's response to each comment.

Request To Refer to New Service Information

De Havilland Aircraft of Canada Limited requested that the FAA revise the proposed AD to refer to De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023. De Havilland Aircraft of Canada Limited noted that the service information had been updated since the NPRM was released.

The FAA agrees with the request. De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023, provides clarity on service information that may be used to do rework if there are gaps in the new radius fillers (saddle washers), and specifies an additional radius filler part number. The FAA has revised this AD to refer to De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023. The FAA has also revised paragraph (i) of this AD to provide credit for De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision A, dated February 16, 2022.

Request To Revise Corrective Actions

De Havilland Aircraft of Canada Limited requested that the FAA revise paragraph (h) of the proposed AD. The commenter stated that De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023, includes instructions for reworking the new radius fillers that exhibit fouling conditions (gapping), and that the proposed AD should be amended to explain this.

The FAA agrees to clarify. Paragraph (h) of this AD requires corrective actions (parts replacements) in accordance with Section 3.B., Part B, of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023. The rework the commenter mentioned is part of Section 3.B., Part B, and is specified as part of the corrective actions if gapping is found after replacement of the radius filler. Therefore, that step is included as part of the requirements of paragraph (h) of this AD.

Request To Correct the Number of U.S. Registered Airplanes

De Havilland Aircraft of Canada Limited requested that the FAA revise the cost of compliance section to correct the number of affected airplanes. The commenter stated that the number of aircraft on the U.S. registry is 49, not 400 as stated in the NPRM.

The FAA agrees that the number of U.S. registered airplanes is less than that specified in the NPRM. After reviewing the FAA registry, the FAA has determined the correct number of affected airplanes is 54. The FAA has revised the Costs of Compliance section accordingly.

Conclusion

This product has been approved by the aviation authority of another country and is approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA reviewed the relevant data, considered the 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 this product. Except for minor editorial changes, and any other changes described previously, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023. This service information specifies procedures for a detailed visual inspection of the front and rear spar joints for signs of gapping or bending of the radius filler and/or adjacent washers, and depending on the inspection results, replacement of the saddle washer, adjacent washers, bolt, and barrel nut.

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.

Costs of Compliance

The FAA estimates that this AD affects 54 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs for Required Actions

Labor cost	Parts cost	Cost per product	Cost on U.S. operators
5 work-hours × $85 per hour = $425	$0	$425	$22,950

The FAA estimates the following costs to do any necessary on-condition action that would be required based on the results of any required actions. The FAA has no way of determining the number of aircraft that might need this on-condition action:

Estimated Costs of On-Condition Actions

Labor cost	Parts cost	Cost per product
2 work-hours × $85 per hour = $170	$5,333	$5,503

The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some or all 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 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

[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive:

2024–02–02 De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.): Amendment 39–22666; Docket No. FAA–2023–0933; Project Identifier MCAI–2022–00554–T.

(a) Effective Date

This airworthiness directive (AD) is effective March 21, 2024.

(b) Affected ADs

None.

(c) Applicability

This AD applies to De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Model DHC–8–401 and –402 airplanes, certificated in any category, having serial numbers 4001 and 4003 through 4633 inclusive.

(d) Subject

Air Transport Association (ATA) of America Code: 55, Stabilizers.

(e) Unsafe Condition

This AD was prompted by reports that the saddle washer (radius filler) for the front and rear spar joints may have been incorrectly manufactured for several years. The FAA is issuing this AD to address gaps and bending of the saddle washer that could have the potential to reduce the life of the bolt, which in turn could affect the structural integrity of the horizontal stabilizer to vertical stabilizer joint.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Inspection

Within 8,000 flight hours after the effective date of this AD, perform a detailed inspection for signs of gapping or bending of the saddle washers and adjacent washers in the front spar and rear spar horizontal/vertical stabilizer joint fitting in accordance with Section 3.B., Part A, of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023.

(h) Corrective Actions

If any gaps or bending of the washers are found during the inspection required by paragraph (g) of this AD, before further flight, replace the saddle washer, washers, PLI washer, bolt, and barrel nut, as applicable, in accordance with Section 3.B., Part B, of the Accomplishment Instructions of De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023.

(i) Credit for Previous Actions

This paragraph provides credit for actions required by paragraphs (g) and (h) of this AD, if those actions were performed before the effective date of this AD using De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, dated September 7, 2021; or De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision A, dated February 16, 2022.

(j) Additional AD Provisions

The following provisions also apply to this AD:

(1) Alternative Methods of Compliance (AMOCs): The Manager, International Validation 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 responsible Flight Standards Office, as appropriate. If sending information directly to the manager of the International Validation Branch, send it to the attention of the person identified in paragraph (k)(2) of this AD. Information may be emailed to: [e-mail]. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.

(2) Contacting the Manufacturer: For any requirement in this AD to obtain instructions from a manufacturer, the instructions must be accomplished using a method approved by the Manager, International Validation Branch, FAA; or Transport Canada; or De Havilland Aircraft of Canada Limited's Transport Canada Design Approval Organization (DAO). If approved by the DAO, the approval must include the DAO-authorized signature.

(k) Additional Information

(1) Refer to Transport Canada AD CF–2022–21, dated April 21, 2022, for related information. This Transport Canada AD may be found in the AD docket at regulations.gov under Docket No. FAA–2023–0933.

(2) For more information about this AD, contact Yaser Osman, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone [phone]; email [e-mail].

(3) Service information identified in this AD that is not incorporated by reference is available at the addresses specified in paragraphs (l)(3) and (4) of this AD.

(l) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this service information as applicable to do the actions required by this AD, unless this AD specifies otherwise.

(i) De Havilland Aircraft of Canada Limited Service Bulletin 84–55–12, Revision B, dated April 20, 2023.

(ii) [Reserved]

(3) For service information identified in this AD, contact De Havilland Aircraft of Canada Limited, Dash 8 Series Customer Response Centre, 5800 Explorer Drive, Mississauga, Ontario, L4W 5K9, Canada; telephone [phone] or 647–277–5820; email [e-mail]; website dehavilland.com.

(4) You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th Street, Des Moines, WA. For information on the availability of this material at the FAA, call 206–231–3195.

(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 [e-mail].

Issued on January 24, 2024.

Victor Wicklund,

Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.