AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede Airworthiness Directive (AD) 2010-23-04, which applies to all De Havilland Aircraft of Canada Limited Model DHC-8-400 series airplanes. AD 2010-23-04 requires repetitive detailed inspections of the nacelle attachment fittings for cracks, a conductivity inspection of the nacelle attachment fittings, and replacement if necessary. Since AD 2010-23-04 was issued, the FAA has determined that it is necessary to do a replacement with new nacelle attachment fittings. This proposed AD would retain the requirements of AD 2010-23-04, remove a certain inspection requirement for certain airplanes, and add a new requirement to replace the rear spar fitting and nacelle attaching structure with a new nacelle attachment fitting. The FAA is proposing this AD to address the unsafe condition on these products.

DATES:

The FAA must receive comments on this proposed AD by April 27, 2020.

ADDRESSES:

You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:

• Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: 202-493-2251.
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
• Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, contact De Havilland Aircraft of Canada Limited, Q-Series Technical Help Desk, 123 Garratt Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416-375-4000; fax 416-375-4539; email thd@dehavilland.com; internet https://dehavilland.com. 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.

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-0099; 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 NPRM, the regulatory evaluation, any comments received, and other information. The street address for Docket Operations is listed above. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Andrea Jimenez, Aerospace Engineer, Airframe and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7330; fax 516-794-5531; email 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2020-0099; Product Identifier 2019-NM-169-AD” at the beginning of your comments. The FAA specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. The FAA will consider all comments received by the closing date and may amend this proposed AD based on those comments.

The FAA will post all comments received, without change, to https://www.regulations.gov, including any personal information you provide. The FAA will also post a report summarizing each substantive verbal contact received about this proposed AD.

Discussion

The FAA issued AD 2010-23-04, Amendment 39-16493 (75 FR 68174, November 5, 2010) (“AD 2010-23-04”), for all De Havilland Aircraft of Canada Limited Model DHC-8-400 series airplanes. AD 2010-23-04 requires repetitive detailed inspections of the nacelle attachment fittings for cracks, a conductivity inspection of the nacelle attachment fittings, and replacement if necessary. AD 2010-23-04 resulted from reports of cracked nacelle attachment fittings, which a preliminary investigation determined to be caused by stress corrosion. The FAA issued AD 2010-23-04 to address this condition, which, if not detected and corrected, could compromise the structural integrity of the nacelle attachment fitting and possibly result in collapse of the landing gear.

Actions Since AD 2010-23-04 Was Issued

Since AD 2010-23-04 was issued, the FAA has determined that it is necessary to require a replacement with new nacelle attachment fittings, which would be terminating action for the inspections specified in AD 2010-23-04. Additionally, paragraph (i) of AD 2010-23-04 requires repetitive detailed inspections for cracking on each of the four nacelle attachment fittings for airplanes having serial numbers 4305 through 4313 inclusive, and 4316 and subsequent. The FAA has retained this inspection in paragraph (h) of this proposed AD, but serial numbers 4381 and subsequent were modified in production and cannot have the affected part installed, so those airplanes were removed from the retained actions in paragraph (h) of this proposed AD.

Transport Canada Civil Aviation (TCCA), which is the aviation authority for Canada, has issued Canadian AD CF-2010-30R2, dated July 30, 2019 (referred to after this as the Mandatory Continuing Airworthiness Information, or “the MCAI”), to correct an unsafe condition for all De Havilland Aircraft of Canada Limited Model DHC-8-400 series airplanes. You may examine the MCAI in the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-0099.

This proposed AD was prompted by a determination that it is necessary to install new nacelle attachment fitting in order to address the unsafe condition. The FAA is proposing this AD to address cracked nacelle attachment fittings, which a preliminary investigation determined to be caused by stress corrosion. This condition, if not detected and corrected, could compromise the structural integrity of the nacelle attachment fitting and possibly result in collapse of the landing gear. See the MCAI for additional background information.

Related Service Information Under 1 CFR Part 51

Bombardier has issued Service Bulletin 84-54-14, Revision K, dated August 7, 2018. This service bulletin describes procedures for a conductivity inspection of the nacelle attachment fittings, repetitive detailed inspections of the nacelle attachment fittings for cracks, and replacement of the fitting.

Bombardier has also issued Service Bulletin 84-54-16, Revision D, dated August 7, 2018. This service information describes procedures for replacing the rear spar nacelle attachment fitting and associated structure with a new nacelle attachment fitting, part number (P/N) 8Z9305. The replacement includes applicable related investigative and corrective actions. The related investigative actions include an inspection of the internal bore and external surface of the main landing gear yoke pins, the drag strut pins, and the stabilizer brace pins for signs of corrosion and damage; an inspection of the inner bore and outer surface of the coat hangar pins for signs of corrosion and damage. The corrective actions include repair, rework, or replacement.

Bombardier has also issued Modification Summary Package IS4Q5400012, Revision B, dated July 11, 2012. This service information describes procedures for applying a fay sealant gasket to the rear spar access fitting access panel.

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.

FAA's Determination

This product has been approved by the aviation authority of another country, and is approved for operation in the United States. Pursuant to a bilateral agreement with the State of Design Authority, the FAA has been notified of the unsafe condition described in the MCAI and service information referenced above. The FAA is proposing this AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop on other products of the same type design.

Proposed Requirements of This NPRM

This proposed AD would retain all of the requirements of AD 2010-23-04. This proposed AD would also require accomplishing the actions specified in the service information described previously.

Costs of Compliance

The FAA estimates that this proposed AD affects 54 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed 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.

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

The FAA has determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 this proposed regulation:

(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 Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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.

2. The FAA amends § 39.13 by removing Airworthiness Directive (AD) 2010-23-04, Amendment 39-16493 ( 75 FR 68174, November 5, 2010), and adding the following new AD:

De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.): Docket No. FAA-2020-0099; Product Identifier 2019-NM-169-AD.

(a) Comments Due Date

The FAA must receive comments by April 27, 2020.

(b) Affected ADs

This AD replaces AD 2010-23-04, Amendment 39-16493 (75 FR 68174, November 5, 2010) (“AD 2010-23-04”).

(c) Applicability

This AD applies to De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by 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 54, Nacelles/pylons.

(e) Reason

This AD was prompted by reports of cracked nacelle attachment fittings, which a preliminary investigation determined to be caused by stress corrosion. The FAA is issuing this AD to address this condition, which, if not detected and corrected, could compromise the structural integrity of the nacelle attachment fitting and possibly result in collapse of the landing gear.

(f) Compliance

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

(g) Retained Detailed and Conductivity Inspections and Replacement, With Revised Service Information and Revised Replacement Instructions

This paragraph restates the requirements of paragraph (g) of AD 2010-23-04, with revised service information and revised replacement instructions. For airplanes having serial numbers 4001 through 4304 inclusive, 4314, and 4315: Within 100 flight hours after November 22, 2010 (the effective date of AD 2010-23-04), do a detailed inspection for cracking, and a conductivity inspection on each of the 4 nacelle attachment fittings, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018. Repeat the detailed inspection at intervals not to exceed 300 flight hours, except as provided by paragraph (i) of this AD. Accomplishing the replacement specified in paragraph (g)(1)(ii) or (g)(2)(ii)(B) of this AD terminates the inspections required by this paragraph.

(1) If any nacelle attachment fitting is found cracked, before further flight, do the action specified in paragraph (g)(1)(i) or (ii) of this AD. As of the effective date of this AD, only the action specified in paragraph (g)(1)(ii) of this AD may be done.

(i) Replace the fitting with a new fitting in accordance with paragraph (2) of Part A of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018.

(ii) Replace the rear spar nacelle attachment fitting and associated structure with a new nacelle attachment fitting, part number (P/N) 8Z9305, and do all applicable related investigative and corrective actions, in accordance with Part B of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-16 Revision D, dated August 7, 2018. Do all applicable related investigative and corrective actions before further flight.

(2) If the conductivity of any test points on any fitting is found to be greater than 45.0 percent International Annealed Copper Standard (IACS) or if the conductivity of any test points on any fitting is found to be less than 38.0 percent IACS, do the actions required by paragraphs (g)(2)(i) and (ii) of this AD.

(i) Within 24 hours after accomplishing the conductivity inspection specified in paragraph (g) of this AD, do a detailed inspection of the nacelle attachment fitting for cracking, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018, and repeat thereafter at intervals not to exceed 24 hours. If cracking is found, before further flight, replace the fitting with a new fitting in accordance with the requirements of paragraph (g)(2)(ii) of this AD. Replacement of the fitting terminates the daily detailed inspection requirements of this paragraph.

(ii) Except as required by paragraph (g)(2)(i) of this AD: Within 300 flight hours after accomplishing the conductivity inspection specified in paragraph (g) of this AD, do the action specified in paragraph (g)(2)(ii)(A) or (B) of this AD. As of the effective date of this AD, only the action specified in paragraph (g)(2)(ii)(B) of this AD may be done.

(A) Replace the fitting with a new fitting in accordance with paragraph (2) of Part A of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018.

(B) Replace the rear spar nacelle attachment fitting and associated structure with a new nacelle attachment fitting, P/N 8Z9305, and do all applicable related investigative and corrective actions, in accordance with Part B of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-16 Revision D, dated August 7, 2018. Do all applicable related investigative and corrective actions before further flight.

(h) Retained Inspections and Replacement, With Revised Service Information, Revised Affected Airplanes, and Revised Replacement Instructions

This paragraph restates the requirements of paragraph (i) of AD 2010-23-04, with revised service information, revised affected airplanes, and revised replacement instructions. For airplanes having serial numbers 4305 through 4313 inclusive, and 4316 through 4380 inclusive, and airplanes that have replaced nacelle attachment fitting(s) with P/N 854146663: Within 1,200 flight hours after November 22, 2010 (the effective date of AD 2010-23-04), do a detailed inspection for cracking on each of the 4 nacelle attachment fittings, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018. If any nacelle attachment fitting is found cracked, before further flight, do the action specified in paragraph (h)(1) or (2) of this AD. As of the effective date of this AD, only the action specified in paragraph (h)(2) of this AD may be done. Thereafter, repeat the detailed inspection at intervals not to exceed 300 flight hours, except as provided by paragraph (i) of this AD. Accomplishing the replacement specified in paragraph (h)(2) of this AD terminates the inspections required by this paragraph.

(1) Replace the fitting with a new fitting in accordance with paragraph (2) of Part A of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018.

(2) Replace the rear spar nacelle attachment fitting and associated structure with a new nacelle attachment fitting, P/N 8Z9305, and do all applicable related investigative and corrective actions, in accordance with Part B of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-16 Revision D, dated August 7, 2018. Do all applicable related investigative and corrective actions before further flight.

(i) Retained Inspection Compliance Time, With Revised Service Information

This paragraph restates the requirements of paragraph (j) of AD 2010-23-04, with revised service information. For any fitting that is replaced in accordance with paragraph (3) of Part A of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision J, dated September 17, 2010; or paragraph (2) of Part A of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018, as specified in paragraph (g) or (h) of this AD: Within 1,200 flight hours after replacing the fitting, do a detailed inspection of that replaced fitting as specified in paragraph (g) or (h) of this AD, and repeat the detailed inspection thereafter at intervals not to exceed 300 flight hours. Accomplishing the replacement specified in paragraph (g)(1)(ii), (g)(2)(ii)(B), or (h)(2) of this AD terminates the inspections required by this paragraph.

(j) Retained Credit for Previous Actions (Replacing the Fitting), With Revised Paragraph References

This paragraph restates the credit provided in paragraph (k) of AD 2010-23-04, with revised paragraph references. Accomplishing the replacement of the nacelle fittings in accordance with any Bombardier service bulletin identified in figure 1 to paragraphs (j) and (k) of this AD before November 22, 2010 (the effective date of AD 2010-23-04) is also acceptable for compliance with the fitting replacements specified in paragraphs (g)(1)(i), (g)(2)(ii)(A), and (h)(1) of this AD.

(k) Retained Credit for Previous Actions (Inspections), With No Changes

This paragraph restates the credit provided in paragraph (l) of AD 2010-23-04, with no changes. Accomplishment of the inspections required by paragraphs (g) and (h) of this AD before November 22, 2010 (the effective date of AD 2010-23-04) in accordance with any Bombardier service bulletin identified in figure 1 to paragraphs (j) and (k) of this AD is acceptable for compliance with the corresponding actions required by paragraphs (g) and (h) of this AD.

(l) New Requirements of This AD: Modification of the Rear Spar Fitting and Nacelle Attaching Structure

For airplanes with nacelle attachment fitting P/N 85414663: Unless already done as specified in paragraph (g)(1)(ii), (g)(2)(ii)(B), or (h)(2) of this AD: Within 8,000 flight hours or 48 months, whichever occurs first, from the effective date of this AD, replace the rear spar nacelle attachment fitting and associated structure with a new nacelle attachment fitting, P/N 8Z9305, and do all applicable related investigative and corrective actions, in accordance with Part B of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-16, Revision D, dated August 7, 2018. Do all applicable related investigative and corrective actions before further flight.

(m) New Credit for Previous Actions

(1) This paragraph provides credit for actions required by paragraphs (g) and (h) of this AD that are identified in Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018, if those actions were performed before the effective date of this AD using Bombardier Service Bulletin 84-54-14, Revision J, dated September 17, 2010, which was incorporated by reference in AD 2010-23-04; except as provided by paragraph (p) of this AD.

(2) This paragraph provides credit for accomplishing the replacement of the rear spar fitting and nacelle attaching structure required by paragraph (l) of this AD, if those actions were performed before the effective date of this AD using the service information specified in paragraphs (m)(2)(i) through (iii) of this AD.

(i) Bombardier Service Bulletin 84-54-16, dated April 29, 2011.

(ii) Bombardier Service Bulletin 84-54-16, Revision A, dated August 1, 2011.

(iii) Bombardier Service Bulletin 84-54-16, Revision C, dated January 31, 2017.

(3) This paragraph provides credit for accomplishing the replacement of the rear spar fitting and nacelle attaching structure required by paragraph (l) of this AD, if those actions were performed before the effective date of this AD using Bombardier Service Bulletin 84-54-16, Revision B, dated October 6, 2016, Although Bombardier Service Bulletin 84-54-16, Revision B, dated October 6, 2016, incorrectly stated that airworthiness limitations (AWLs) or damage tolerance inspections (DTIs) are not affected, they are affected. Refer to the applicable AWLs for Post/Pre-Modification Summary (ModSum) 4-113697 and Bombardier Service Bulletin 84-54-16 in the existing maintenance requirements manual.

(4) This paragraph provides credit for accomplishing the action identified in Bombardier Service Bulletin 84-54-14, Revision K, dated August 7, 2018, that are required by paragraphs (g) and (h) of this AD, if those actions were performed before the effective date of this AD using the service information specified in paragraphs (m)(4)(i) through (iv) of this AD.

(i) Bombardier Service Bulletin 84-54-15, dated August 20, 2010.

(ii) Bombardier Service Bulletin 84-54-15, Revision A, dated October 25, 2010.

(iii) Bombardier Service Bulletin 84-54-15, Revision B, dated February 2, 2017.

(iv) Bombardier Service Bulletin 84-54-15, Revision C, dated August 7, 2018.

(n) Terminating Action for Certain Actions in Paragraphs (g), (h), and (i) of This AD

Accomplishing the modification of the rear spar fitting and nacelle attaching structure required by paragraph (l) of this AD terminates the repetitive inspection required by paragraphs (g), (h), and (i) of this AD for that airplane.

(o) Parts Installation Limitations

As of the effective date of this AD, no person may install a rear spar nacelle attachment fitting P/N 85414663 on any airplane.

(p) Credit for Alternative to Certain Credit Actions

For airplanes on which Bombardier Service Bulletin 84 54 14, Revision J, dated September 17, 2010, was done before the effective date of this AD: As an alternative to applying sealant to each fitting and access panel as specified in paragraph C.(1) of the Accomplishment Instructions of Bombardier Service Bulletin 84-54-14, Revision J, dated September 17, 2010, the use of the instructions of Bombardier Modification Summary Package IS4Q5400012, Revision B, dated July 11, 2012, to apply sealant is also acceptable if accomplished before the effective date of this AD.

(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 2010-23-04, are approved as AMOCs for the corresponding provisions of this AD.

(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, New York ACO Branch, FAA; or Transport Canada Civil Aviation (TCCA); or de Havilland'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 Airworthiness Directive CF-2010-30R2, dated July 30, 2019, for related information. This MCAI may be found in the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-0099.

(2) For more information about this AD, contact Andrea Jimenez, Aerospace Engineer, Airframe and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7330; fax 516-794-5531; email 9-avs-nyaco-cos@faa.gov.

(3) For service information identified in this AD, contact De Havilland Aircraft of Canada Limited, Q-Series Technical Help Desk, 123 Garratt Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416-375-4000; fax 416-375-4539; email thd@dehavilland.com; internet https://dehavilland.com. 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.