AD 2018-22-03

We are superseding Airworthiness Directive (AD) 2016-24-03, which applied to certain Bombardier, Inc., Model DHC-8-400 series airplanes. AD 2016-24-03 required repetitive detailed inspections of barrel nuts and cradles, a check of the bolt torque of the preload indicating (PLI) washers, and corrective actions if necessary. This AD retains the requirements of AD 2016-24-03 and requires modifying the airplane by installing a sealing disk to a certain location and replacing certain barrel nuts. This AD was prompted by reports of cracked and corroded barrel nuts found at the mid-spar location of the horizontal-stabilizer-to-vertical-stabilizer attachment joint, and the issuance of new service information that includes a terminal modification. We are issuing this AD to address the unsafe condition on these products.

Final rule.

Adoption of 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

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

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

Sec. 39.13 [Amended]

0 2. The FAA amends Sec. 39.13 by removing Airworthiness Directive (AD) 2016-24-03, Amendment 39-18720 (81 FR 88623, December 8, 2016), and adding the following new AD:

2018-22-03 Bombardier, Inc.: Amendment 39-19476; Docket No. FAA- 2018-0160; Product Identifier 2017-NM-139-AD.

(a) Effective Date

This AD is effective November 28, 2018.

(b) Affected ADs

This AD replaces AD 2016-24-03, Amendment 39-18720 (81 FR 88623, December 8, 2016) (``AD 2016-24-03'').

(c) Applicability

This AD applies to Bombardier, Inc., Model DHC-8-400, -401 and - 402 airplanes, certificated in any category, serial numbers 4001 and subsequent.

(d) Subject

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

(e) Reason

This AD was prompted by reports of cracked and corroded barrel nuts found at the mid-spar location of the horizontal-stabilizer-to- vertical-stabilizer attachment joint, and the issuance of new service information that includes a terminal modification. We are issuing this AD to address cracked and corroded barrel nuts, which could compromise the structural integrity of the vertical-stabilizer attachment joints and lead to loss of control of the airplane.

(f) Compliance

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

(g) Retained Detailed Inspection of Barrel Nuts for Cracks and Corrosion, With No Changes

This paragraph restates the requirements of paragraphs (g)(1) and (g)(2) of AD 2016-24-03, with no changes.
(1) For airplanes that have accumulated 5,400 flight hours or more, or have been in service 32 months or more since the date of issuance of the original certificate of airworthiness or the date of issuance of the original export certificate of airworthiness, as of January 12, 2017 (the effective date of AD 2016-24-03): Within 600 flight hours or 4 months, whichever occurs first after January 12, 2017, do a detailed visual inspection for signs of cracks and corrosion of the barrel nut and cradle, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016.
(2) For airplanes that have less than 5,400 flight hours, and have been in-service for less than 32 months since the date of issuance of the original certificate of airworthiness or the date of issuance of the original export certificate of airworthiness, as of January 12, 2017: Before the accumulation of 6,000 total flight hours or 36 months since the date of issuance of the original certificate of airworthiness or the date of issuanceof the original export certificate of airworthiness, whichever occurs first, do a detailed visual inspection of the barrel nut for signs of cracks and corrosion of the barrel nut and cradle, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016.

(h) Retained Corrective Actions, Detailed Inspection, and Repetitive Inspections, With New Service Information, Reference to Terminating Action, and Reference to Corrective Actions

This paragraph restates the requirements of paragraph (h) of AD 2016-24-03, with new service information and terminating action. Depending on the findings of any inspection required by paragraphs (g) and (j) of this AD, do the applicable actions in paragraphs (h)(1), (h)(2), (h)(3), and (h)(4) of this AD. Accomplishment of the actions required by paragraphs (l) and (m) of this AD, as applicable, terminates the requirements of this paragraph.
(1)If any barrel nut or cradle is found cracked or broken, before further flight, replace the barrel nut and associated hardware, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017.
(i) Concurrently with the replacement of any barrel nut, do a detailed inspection for corrosion and damage of the bore of the fitting, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017, and, before further flight, repair all corrosion and damage, in accordance with Bombardier Repair Drawing (RD) 8/4-55-1143, Issue 1, dated May 21, 2015; or Bombardier RD 8/4-55-1143, Issue 2, dated May 25, 2015. If the bore of the fitting cannot be repaired in accordance with Bombardier RD 8/4-55- 1143, Issue 1, dated May 21, 2015; or Bombardier RD 8/4-55-1143, Issue 2, dated May 25, 2015; accomplish correctiveactions in accordance with the procedures specified in paragraph (q)(2) of this AD. As of the effective date of this AD, use Bombardier RD 8/4-55- 1143, Issue 2, dated May 25, 2015, for the repair required by this paragraph.
(ii) Within 600 flight hours or 4 months, whichever occurs first, after the replacement of a cracked barrel nut, replace the remaining barrel nuts and their associated hardware at the horizontal-stabilizer-to-vertical-stabilizer attachment joints, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017.
(2) If any corrosion is found on any barrel nut on the front or rear-spar joints, before further flight, replace the barrel nut in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017, or accomplish corrective actions in accordance with the procedures specified in paragraph (q)(2) of this AD.
(3) If any corrosion above level 1, as defined in Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016, is found on a barrel nut at the mid-spar joint, before further flight, replace the barrel nut and accomplish corrective actions in accordance with the procedures specified in paragraph (q)(2) of this AD.
(4) If all corrosion found is at level 1 or below, as defined in Bombardier Alert Service Bulletin A84-55-04, Revision C,

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dated May 3, 2016, on a barrel nut at the mid-spar joint, repeat the inspection specified in paragraph (g) of this AD at intervals not to exceed 600 flight hours or 4 months, whichever occurs first, until completion of the actions required by paragraph (k) of this AD.

(i) Retained Preload Indicating (PLI) Washer Check, With New Terminating Action

This paragraph restates the requirements of paragraph (i) of AD 2016-24-03, with new terminating action. For airplanes with PLI washers installed at the front and rear-spar joints, before further flight after accomplishing any inspection required by paragraph (g) of this AD and all applicable corrective actions required by paragraph (h) of this AD, check the bolt preload, and do all applicable corrective actions, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016. Do all applicable corrective actions before further flight. Accomplishment of the actions required by paragraphs (l) and (m) of this AD, as applicable, terminates the requirements of this paragraph.

(j) Retained Repetitive Inspection Interval, With New Terminating Action

This paragraph restates the requirements of paragraph (j) of AD 2016-24-03, with new terminating action. Repeat the inspection and preload check required by paragraphs (g) and (i) of this AD at intervals not to exceed 3,600 flight hours or 18 months, whichever occurs first, except as provided by paragraph (k) of this AD. Accomplishment of the actions required by paragraphs (l) and (m) of this AD, as applicable, terminates the requirements of this paragraph.

(k) Retained Optional Barrel Nut Replacement, With New Service Information

This paragraph restates the provisions of paragraph (k) of AD 2016-24-03, with new service information. Inspection and replacement of all barrel nuts at the horizontal-stabilizer-to-vertical- stabilizer attachment joints, in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017, extends the next inspection required by paragraph (j) of this AD to within 6,000 flight hours or 36 months, whichever occurs first, after accomplishing the replacement.

(l) New Requirement of This AD: Sealing Disk Installation

Within 8,000 flight hours or 48 months, whichever occurs first, after the effective date of this AD, install a sealing disk at the mid-spar location of the vertical stabilizer in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-06, dated January 31, 2017. Accomplishment of the actions required by paragraphs (l) and (m) of this AD, as applicable, terminates the requirements of paragraphs (h), (i), and (j) of this AD.

(m) New Requirement of This AD: Replacement of DSC228 Series Barrel Nuts

For Bombardier, Inc., Model DHC-8-400, -401 and -402 airplanes, serial numbers 4001 through 4524 inclusive: Within 8,000 flight hours or 48 months, whichever occurs first, after the effective date of this AD, replace all DSC228 series barrel nuts at the horizontal- stabilizer-to-vertical-stabilizer attachment joints with B0203073 series barrel nuts in accordance with paragraph 3.B., ``Procedure,'' of the Accomplishment Instructions of Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017. Accomplishment of the actions required by paragraphs (l) and (m) of this AD, as applicable, terminates the requirements of paragraphs (h), (i), and (j) of this AD.

(n) Parts Installation Prohibition

After modification of an airplane as required by paragraphs (l) and (m) of this AD, no person may install a DSC228 series barrel nut at the horizontal-stabilizer-to-vertical-stabilizer attachment joint on the modified airplane.

(o) Terminating Actions for Paragraphs (h), (i), and (j) of This AD

Accomplishment of the actions required by paragraphs (l) and (m) of this AD, as applicable, terminates the requirements of paragraphs (h), (i), and (j) of this AD.

(p) Credit for Previous Actions

(1) This paragraph provides credit for actions required by paragraphs (g)(1), (g)(2), (h)(1), (h)(1)(i), (h)(1)(ii), (h)(2), (h)(3), (h)(4), (i), and (k) of this AD, if those actions were performed before the effective date of this AD using the service information identified in paragraphs (p)(1)(i) through (p)(1)(iii) of this AD.
(i) Bombardier Alert Service Bulletin A84-55-04, dated May 21, 2015, which is not incorporated by reference in this AD.
(ii) Bombardier Alert Service Bulletin A84-55-04, Revision A, dated June 2, 2015, which is not incorporated by reference in this AD.
(iii) Bombardier Alert Service Bulletin A84-55-04, Revision B, dated July 30, 2015, which is not incorporated by reference in this AD.
(2) This paragraph provides credit for actions required by paragraphs (h)(1), (h)(1)(i), (h)(1)(ii), (h)(2), and (k) of this AD, if those actions were performed before the effective date of this AD using the service information identified in paragraphs (p)(2)(i) and (p)(2)(ii) of this AD.
(i) Bombardier Service Bulletin 84-55-08, dated January 27, 2017, which is not incorporated by reference in this AD.
(ii) Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016, which was incorporated by reference in AD 2016- 24-03.(q) Other FAA AD Provisions

(1) Alternative Methods of Compliance (AMOCs): The Manager, New York ACO 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 ATTN: Program Manager, Continuing Operational Safety, FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; fax 516-794-5531.
(i) 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.
(ii) AMOCs approved previously for AD 2016-24-03 are approved as AMOCs for the corresponding provisions of this AD.
(2) Contacting the Manufacturer: Forany requirement in this AD to obtain corrective actions from a manufacturer, the action must be accomplished using a method approved by the Manager, New York ACO Branch, FAA; or Transport Canada Civil Aviation (TCCA); or Bombardier, Inc.'s TCCA Design Approval Organization (DAO). If approved by the DAO, the approval must include the DAO-authorized signature.

(r) Related Information

(1) Refer to Mandatory Continuing Airworthiness Information (MCAI) Canadian AD CF-2015-13R1, dated June 26, 2017, for related information. This MCAI may be found in the AD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018-0160.
(2) For more information about this AD, contact Aziz Ahmed, Aerospace Engineer, Airframe and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7329; fax 516-794-5531; email 9-avs-nyaco-cos@faa.gov.
(3) Service information identified in this AD that is not incorporated by reference is available at the addresses specified in paragraphs (s)(5) and (s)(6) of this AD.

(s) 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.
(3) The following service information was approved for IBR on November 28, 2018.
(i) Bombardier Repair Drawing (RD) 8/4-55-1143, Issue 2, dated May 25, 2015.
(ii) Bombardier Service Bulletin 84-55-06, dated January 31, 2017.
(iii) Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017.
(4) The following service information was approved for IBR on January 12, 2017 (81 FR 88623, December 8, 2016).
(i) Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016.
(ii)Reserved.
(5) For service information identified in this AD, contact Bombardier, Inc., Q-Series Technical Help Desk, 123 Garratt Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416-375-4000; fax 416-375-4539; email thd.qseries@aero.bombardier.com; internet http://www.bombardier.com.

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(6) You may view this service information at the FAA, Transport Standards Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195.
(7) You may view this service information that is incorporated by reference at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2016-24-03, Amendment 39-18720 (81 FR 88623, December 8, 2016) (``AD 2016-24-03''). AD 2016-24-03 applied to certain Bombardier, Inc., Model DHC-8-400 series airplanes. The NPRM published in the Federal Register on March 9, 2018 (83 FR 10408). The NPRM was prompted by reports of cracked and corroded barrel nuts found at the mid-spar location of the horizontal-stabilizer-to-vertical-stabilizer attachment joint, and the issuance of new service information that includes a terminal modification. The NPRM proposed to continue to require repetitive detailed inspections of each barrel nut and cradle, a check of the bolt torque of the PLI washers, and corrective action if necessary. The NPRM also proposed to require modifying the airplane by installing a sealing disk to a certain location and replacing certain barrel nuts. We are issuing this AD to address cracked and corroded barrel nuts, which could compromise the structural integrity of the vertical-stabilizer attachment joints and lead to loss of control of the airplane.
Transport Canada Civil Aviation (TCCA), which is the aviation authority for Canada, has issued Canadian AD CF-2015-13R1, dated June 26, 2017 (referred to after this as the Mandatory Continuing Airworthiness Information, or ``the MCAI''), to correct an unsafe condition for certain Bombardier, Inc., Model DHC-8-400 series airplanes. The MCAI states:

There has been one in-service report of a cracked and corroded barrel nut, part number (P/N) DSC228-12, found at the mid-spar location of the horizontal stabilizer to vertical stabilizer attachment joint. There have also been two other reports of corroded barrel nuts found at mid-spar locations.
Preliminary investigation determined that the cracking is initiated by corrosion. Further investigation confirmed that the corrosion was caused by inadequate cadmium plating on the barrel nuts. Failure of the barrel nuts could compromise the structural integrity of the joint and could lead to loss of control of the aeroplane.
The original version of this [Canadian] AD was issued to mandate the initial and repetitive inspections of the barrel nuts [and cradles for cracks and corrosion] at each of the horizontal stabilizer to vertical stabilizer attachment joints.
Revision 1 of this [Canadian] AD is issued to terminate the repetitive inspection requirement by requiring the incorporation of a modification to install a sealing disc at the middle spar location of the horizontal stabilizer to vertical stabilizer attachment joint, and the replacement of the DSC228 series barrel nuts with B0203073 series barrel nuts that are more resistant to corrosion. The applicability has been changed to account for the introduction of the modifications in production.

You may examine the MCAI in the AD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018- 0160.

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Comments

We gave the public the opportunity to participate in developing this final rule. The following presents the comment received on the NPRM and the FAA's response.

Request To Refer to New Repair Drawing (RD)

Horizon Air requested that we revise paragraph (h)(1)(i) of the proposed AD to refer to Bombardier RD 8/4-55-1143, Issue 2, dated May 25, 2015 (we referred to Bombardier RD 8/4-55-1143, Issue 1, dated May 21, 2015, as the appropriate source of service information for the repair specified in paragraph (h)(1)(i) of the proposed AD). Horizon Air noted that Bombardier RD 8/4-55-1143, Issue 2, dated May 25, 2015, adds nominal bore diameters to sheets 1-4.
We agree with the commenter's request. Bombardier RD 8/4-55-1143, Issue 2, dated May 25, 2015, clarifies the bore hole diameters for repair but does not otherwise change the substantive requirements of this AD. No additional work is necessary for airplanes on which Bombardier RD 8/4-55-1143, Issue 1, dated May 21, 2015, has already been done. We have revised paragraph (h)(1)(i) of this AD to include Bombardier RD 8/4-55-1143, Issue 2, dated May 25, 2015, as the appropriate service information for repairing corrosion and damage of the bore of the fitting.

Conclusion

We reviewed the relevant data, considered the comment received, and determined that air safety and the public interest require adopting this final rule with the change described previously and minor editorial changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the NPRM for addressing 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 51Bombardier has issued the following service information.
Bombardier Alert Service Bulletin A84-55-04, Revision C, dated May 3, 2016. This service information describes procedures for a detailed inspection and repair for cracks and corrosion of the barrel nuts and cradles; a bolt preload check of the PLI washers and applicable corrective actions; a detailed inspection and repair for corrosion and damage of the bore of the fitting; and replacement of the barrel nuts.
Bombardier Service Bulletin 84-55-06, dated January 31, 2017. This service information describes procedures for installing an aluminum sealing disk at the mid-spar location of the vertical stabilizer.
Bombardier Service Bulletin 84-55-08, Revision A, dated August 2, 2017. This service information describes procedures for an inspection for part number and damage of the barrel nuts at the horizontal-stabilizer-to-vertical-stabilizer attachment joints, and replacement of discrepant parts.
Bombardier Repair Drawing (RD) 8/4-55-1143, Issue 2, dated May 25, 2015. This service information describes procedures for repairing corrosion and damage of the fitting bore.
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

We estimate that this AD affects 54 airplanes of U.S. registry. We estimate the following costs to comply with this AD:

Estimated Costs ----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Inspections (retained actions from AD 8 work-hours x $85 per $0 $680 $36,720
2016-24-03). hour = $680. Sealing disk installation (new action) 4 work-hours x $85 per 781 1,121 60,534
hour = $340. Replacement of DSC228 series barrel 2 work-hours x $85 per 2,236 2,406 129,924
nuts (new action). hour = $170. ----------------------------------------------------------------------------------------------------------------

We estimate the following costs to do any necessary replacements that would be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these replacements:

On-Condition Costs ----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replacement (retained action from AD 2016-24- 2 work-hours x $85 per hour = $8,881 $9,051
03). $170. ----------------------------------------------------------------------------------------------------------------

We have received no definitive data that would enable us to provide cost estimates for the other on-condition actions specified in this AD.

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.

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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 transport category airplanes and associated appliances to the Director of the System Oversight Division.

Regulatory Findings

We determined that 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 the 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 of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.