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2022-23-01 DE HAVILLAND AIRCRAFT OF CANADA LIMITED (TYPE CERTIFICATE PREVIOUSLY HELD BY BOMBARDIER, INC.): Amendment 39-22228; Docket No. FAA-2022-0672; Project Identifier MCAI-2020-01606-T.
(a) EFFECTIVE DATE

    This airworthiness directive (AD) is effective December 13, 2022.

(b) AFFECTED ADS

    This AD replaces AD 2020-04-20, Amendment 39-19857 (85 FR 17473, March
    30, 2020) (AD 2020-04-20).

(c) APPLICABILITY

    This AD applies to De Havilland Aircraft of Canada Limited Model DHC-8
    -400, -401, and -402 airplanes, certificated in any category, manufac-
    turer serial numbers 4001 and 4003 and subsequent.

(d) SUBJECT

    Air Transport Association (ATA) of America Code 28, Fuel.

(e) REASON

    This AD  was prompted  by reports  of wear  on fuel couplings, bonding
    springs,  and sleeves  as well  as fuel  tube end  ferrules  and  fuel
    component end  ferrules, and  by a  determination that  a more  robust
    lightning ignition protection design is necessary. The FAA is  issuing
    this AD to address such wear, which could reduce the integrity of  the
    electrical bonding  paths through  the fuel  line and  components, and
    ultimately lead  to fuel  tank ignition  in the  event of  a lightning
    strike.

(f) COMPLIANCE

    Comply with this AD within the compliance times specified,  unless al-
    ready done.

(g) RETAINED INITIAL INSPECTION  COMPLIANCE TIMES,  WITH  NEW  TERMINATING
    ACTION

    This paragraph restates the requirements of paragraph (g)  of AD 2020-
    04-20,  with  new  terminating  action.  For  airplanes  having serial
    numbers 4001 and 4003 through 4575  inclusive that, as of May 4,  2020
    (the  effective date  of AD  2020-04-20),  have  not done  the actions
    specified in Bombardier Service  Bulletin 84-28-21: At the  applicable
    times specified in paragraph (g)(1) or (2) of this AD, do the  actions
    specified in paragraphs (h)(1) and  (2) of this AD. Accomplishing  the
    terminating action required by paragraph (p) of this AD terminates the
    initial inspection required by this paragraph.

(1) For all airplanes  except those identified in paragraph (g)(2) of this
    AD:  Within 6,000 flight hours  or  36 months,  whichever occurs first
    after May 4, 2020 (the effective date of AD 2020-04-20).

(2) For airplanes  with an original airworthiness certificate  or original
    export certificate  of airworthiness  issued on  or after  May 4, 2020
    (the effective date of AD 2020-04-20): Within 6,000 flight hours or 36
    months,  whichever occurs  first  after  the date  of issuance  of the
    original  airworthiness certificate  or the  date of  issuance of  the
    original export certificate of airworthiness.

(h) RETAINED REPETITIVE INSPECTIONS AND CORRECTIVE ACTIONS, WITH NEW TERM-
    INATING ACTION

    This paragraph  restates the requirements of paragraph (h) of AD 2020-
    04-20,  with  new  terminating  action.  For  airplanes  having serial
    numbers 4001 and 4003 through 4575  inclusive that,  as of May 4, 2020
    (the  effective date  of AD  2020-04-20),  have  not done  the actions
    specified in Bombardier Service  Bulletin 84-28-21: At the  applicable
    times specified in paragraph (g)(1) or (2) of this AD, do the  actions
    specified in paragraphs (h)(1) and (2) of this AD. Repeat the  actions
    thereafter at intervals not to exceed 6,000 flight hours or 36 months,
    whichever occurs first. Accomplishing the terminating action  required
    by  paragraph (p)  of this  AD terminates  the repetitive  inspections
    required by this paragraph.

(1) Do a detailed inspection of the clamshell coupling bonding wires, fuel
    couplings and associated sleeves for discrepancies that meet specified
    criteria,  as identified in,  and in accordance with,  paragraph 3.B.,
    "Procedure,"  of the Accomplishment Instructions of Bombardier Service
    Bulletin 84-28-20,  Revision D,  dated November 23, 2018.  If any con-
    ditions are found meeting the criteria specified in Bombardier Service
    Bulletin 84-28-20, Revision D, dated November 23, 2018, before further
    flight,  replace affected parts  with new couplings and sleeves of the
    same part number,  in accordance with paragraph 3.B.,  "Procedure," of
    the  Accomplishment  Instructions  of  Bombardier  Bulletin  84-28-20,
    Revision D, dated November 23, 2018.

(2) Do a detailed inspection of the fuel tube end ferrules, fuel component
    end ferrules, and ferrule O-ring flanges  for damage and wear, and re-
    work (repair, replace, or blend, as applicable) the parts,  in accord-
    ance with paragraph 3.B.,  "Procedure," of the Accomplishment Instruc-
    tions of Bombardier Service Bulletin 84-28-20 Revision D, dated Novem-
    ber 23, 2018.

(i) RETAINED OPTIONAL TERMINATING ACTION  FOR REPETITIVE INSPECTIONS  WITH
    NO CHANGES

    This paragraph  restates the requirements of paragraph (i) of AD 2020-
    04-20, with no changes.  For airplanes  having serial numbers 4001 and
    4003 through 4575 inclusive:  Doing a detailed inspection  of the fuel
    tube end ferrules,  fuel component end ferrules,  and  ferrule  O-ring
    flanges for damage and wear, and reworking (repair, replace, or blend,
    as applicable) the parts;  and doing a retrofit (structural rework) of
    the fuel couplings, isolators and structural provisions, in accordance
    with paragraph 3.B.,  "Procedure,"  of the Accomplishment Instructions
    of Bombardier Service Bulletin 84-28-21,  Revision C,  dated  July 13,
    2018, terminates the inspections  specified  in  paragraphs (h)(1) and
    (2) of this AD.

(j) RETAINED ELECTRICAL BONDING CHECKS/DETAILED INSPECTION WITH NO CHANGES

    This paragraph restates the requirements of paragraph (j)  of AD 2020-
    04-20, with no changes. For airplanes having serial numbers 4001, 4003
    through 4489 inclusive and 4491 through 4575 inclusive that, as of May
    4, 2020 (the effective date of AD 2020-04-20),  have done  the actions
    specified in Bombardier Service Bulletin 84-28-21,  Revision A,  dated
    September 29, 2017;  and  airplanes having serial numbers 4576 through
    4581 inclusive:  Within 6,000 flight hours  or  36 months after May 4,
    2020,  whichever occurs first,  do the actions specified  in paragraph
    (j)(1) or (2) of this AD.

(1) Accomplish electrical bonding checks of all threaded couplings  on the
    inboard vent lines  in the left and right wings,  in  accordance  with
    paragraph 3.B.,  "Procedure,"  of  the  Accomplishment Instructions of
    Bombardier Service Bulletin 84-28-26,  Revision A,  dated November 29,
    2018.

(2) Do a detailed inspection of the fuel tube end ferrules, fuel component
    end ferrules,  and ferrule O-ring flanges for damage and wear, and re-
    work (repair, replace or blend, as applicable) the parts; and a retro-
    fit (structural rework) of the fuel couplings,  isolators,  and struc-
    tural provisions;  in accordance with paragraph 3.B.,  "Procedure," of
    the Accomplishment Instructions  of Bombardier Service Bulletin 84-28-
    21, Revision C, dated July 13, 2018.

(k) RETAINED REVISION OF THE EXISTING MAINTENANCE  OR  INSPECTION PROGRAM,
    WITH NO CHANGES

    This paragraph  restates the requirements of paragraph (k) of AD 2020-
    04-20, with no changes.  Within 30 days  after May 4, 2020 (the effec-
    tive date of AD 2020-04-20),  revise the existing maintenance  or  in-
    spection program, as applicable, to incorporate the information speci-
    fied in Q400 Dash 8 (Bombardier)  Temporary Revision  ALI-0192,  dated
    April 24, 2018;  and  Q400 Dash 8 (Bombardier) Temporary Revision ALI-
    0193,  dated April 24, 2018.  Except as specified  in paragraph (l) of
    this AD,  the initial compliance time for doing the tasks in Q400 Dash
    8 (Bombardier) Temporary Revision ALI-0192,  dated  April 24, 2018, is
    at the time specified in Q400 Dash 8  (Bombardier)  Temporary Revision
    ALI-0192, dated April 24, 2018,  or  within 30 days after May 4, 2020,
    whichever occurs later.

(l) RETAINED INITIAL COMPLIANCE TIME FOR TASK 284000-419, WITH NO CHANGES

    This paragraph  restates the requirements of paragraph (l) of AD 2020-
    04-20, with no changes.  The initial compliance time  for task 284000-
    419 is at the time specified in paragraph (l)(1) or (2) of this AD, as
    applicable, or within 30 days after May 4, 2020 (the effective date of
    AD 2020-04-20), whichever occurs later.

(1) For airplanes having  serial numbers 4001 and 4003 through 4575 inclu-
    sive:  Within 18,000 flight hours  or  108  months,  whichever  occurs
    first, after  the earliest  date of  embodiment of  Bombardier Service
    Bulletin 84-28-21 on the airplane.

(2) For airplanes having serial numbers 4576 and subsequent: Within 18,000
    flight hours or 108 months,  whichever occurs first,  from the date of
    issuance of the original airworthiness certificate  or original export
    certificate of airworthiness.

(m) RETAINED NO ALTERNATIVE ACTIONS, INTERVALS, OR CRITICAL DESIGN CONFIG-
    URATION CONTROL LIMITATIONS (CDCCLS), WITH NO CHANGES

    This paragraph  restates the requirements of paragraph (m) of AD 2020-
    04-20, with no changes.  After the existing maintenance  or inspection
    program has been revised as required by paragraph (k)  of this AD,  no
    alternative actions (e.g., inspections),  intervals,  or CDCCLs may be
    used unless the actions,  intervals,  and  CDCCLs  are  approved as an
    alternative method of compliance (AMOC)  in  accordance  with the pro-
    cedures specified in paragraph (r)(1) of this AD.

(n) RETAINED NO REPORTING PROVISIONS, WITH NO CHANGES

    This paragraph restates the provisions of paragraph (n) of AD 2020-04-
    20,  with no changes.  Although  Bombardier Service Bulletin 84-28-20,
    Revision D,  dated November 23, 2018,  specifies to submit certain in-
    formation to the manufacturer,  this AD does not include that require-
    ment.

(o) RETAINED CREDIT FOR PREVIOUS ACTIONS, WITH NO CHANGES

(1) This paragraph restates the provisions of paragraph (o) of AD 2020-04-
    20, with no changes.  This paragraph provides credit  for  the actions
    required by paragraphs (h)(1) and (2)  of this AD,  if  those  actions
    were performed before May 4, 2020  (the effective date  of AD 2020-04-
    20), using the service information  specified  in  paragraph (o)(1)(i)
    through (iii) of this AD.

(i) Bombardier Service Bulletin 84-28-20,  Revision A,  dated December 14,
    2016.

(ii) Bombardier Service Bulletin 84-28-20, Revision B,  dated February 13,
     2017.

(iii) Bombardier Service Bulletin 84-28-20,  Revision C,  dated  April 28,
      2017.

(2) For the airplane having serial number 4164,  this  paragraph  provides
    credit for the initial inspections  required  by paragraphs (h)(1) and
    (2) of this AD,  if  those  actions  were performed before May 4, 2020
    (the effective date of AD 2020-04-20), using Bombardier Service Bulle-
    tin 84-28-20, dated September 30, 2016.

(3) This paragraph provides credit for the actions  specified in paragraph
    (i) of this AD if those actions were performed before May 4, 2020 (the
    effective date of AD 2020-04-20), using the service information speci-
    fied in paragraph (o)(3)(i) through (iii) of this AD.

(i) Bombardier Service Bulletin 84-28-21, dated August 31, 2017.

(ii) Bombardier Service Bulletin 84-28-21, Revision A, dated September 29,
     2017.

(iii) Bombardier Service Bulletin 84-28-21 Revision B, dated June 8, 2018.

(4) This paragraph provides credit  for the actions  required by paragraph
    (j)(1) of this AD  if those actions were performed  before May 4, 2020
    (the effective date of AD 2020-04-20), using Bombardier Service Bulle-
    tin 84-28-26, dated August 14, 2018.

(5) This paragraph  provides credit for the actions  required by paragraph
    (j)(2) of this AD  if those actions were performed  before May 4, 2020
    (the effective date of AD 2020-04-20), using Bombardier Service Bulle-
    tin 84-28-21, Revision B, dated June 8, 2018.

(6) For airplanes having serial numbers 4001, 4003 through 4489 inclusive,
    and 4491 through 4575 inclusive,  and that are post Bombardier Service
    Bulletin 84-28-21 Revision A, dated September 29, 2017: This paragraph
    provides credit for the actions  required by paragraph (j)  of this AD
    if those actions were performed before May 4, 2020 (the effective date
    of AD 2020-04-20),  using  the  service information specified in para-
    graph (o)(6)(i) or (ii) of this AD.

(i) Bombardier Modification Summary Package  (ModSum)  IS4Q2800032,  dated
    February 1, 2018.

(ii) Any airworthiness limitation change request (ACR) specified in figure
     1 to paragraph (o)(6)(ii) of this AD.

                   FIGURE 1 TO PARAGRAPH (O)(6)(II) – ACRS
                   _______________________________________
                   ACR NUMBER                 DATED
                   _______________________________________
                    400-072              January 24, 2018
                    400-073              January 23, 2018
                    400-074              January 24, 2018
                    400-077              February 27, 2018
                    400-078              March 21, 2018
                    400-079              April 18, 2018
                    400-080              April 30, 2018
                    400-081              May 4, 2018
                    400-082              May 4, 2018
                    400-083              June 4, 2018
                    400-084              May 18, 2018
                   _______________________________________

(p) NEW REWORK AND RETROFIT

    For airplanes  having serial numbers 4001 and 4003 through 4575 inclu-
    sive: At the applicable time  specified in paragraph (p)(1)  or (2) of
    this AD, rework  (repair, replace, or blend, as applicable)  the parts
    (fuel tube end ferrules,  fuel component end ferrules,  and ferrule O-
    ring flanges); and do a retrofit (structural rework) of the fuel coup-
    lings, isolators, and structural provisions; in accordance with Part B
    of paragraph 3.B., "Procedure,"  of the Accomplishment Instructions of
    Bombardier Service Bulletin 84-28-21, Revision C, dated July 13, 2018.
    Accomplishing these actions  terminates the initial and repetitive in-
    spections required by paragraphs (g) and (h) of this AD.

(1) For airplanes  with  greater  than 20,000 total flight hours as of the
    effective date of this AD: Do the actions within 6,000 flight hours or
    36 months after the effective date of this AD, whichever occurs first.

(2) For airplanes with less than  or equal to 20,000 total flight hours as
    of the effective date of this AD:  Do the actions  within 8,000 flight
    hours or  48 months  after the  effective date  of this  AD, whichever
    occurs first.

(q) NEW CREDIT FOR PREVIOUS ACTIONS

    This paragraph provides credit  for the actions required  by paragraph
    (p) of this AD, if  those actions were performed before  the effective
    date of this AD using  the service information specified in  paragraph
    (q)(1), (2), or (3) of this AD.

(1) Bombardier Service Bulletin 84-28-21, dated August 31, 2017.

(2) Bombardier Service Bulletin 84-28-21,  Revision A, dated September 29,
    2017.

(3) Bombardier Service Bulletin 84-28-21, Revision B, dated June 8, 2018.

(r) ADDITIONAL AD PROVISIONS

    The following provisions also apply to this AD:

(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
    responsible  Flight  Standards  Office,  as  appropriate.  If  sending
    information directly to the manager  of the New York ACO  Branch, mail
    it to  ATTN: Program  Manager, Continuing  Operational Safety,  at the
    address identified in paragraph (s)(2)  of this AD or email  to: 9-avs
    -nyaco-cos@faa.gov. If mailing information, also submit information by
    email.  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,  New York  ACO
    Branch,  FAA;  or  Transport  Canada  Civil  Aviation  (TCCA);  or  De
    Havilland   Aircraft  of   Canada  Limited's   TCCA  Design   Approval
    Organization (DAO). If approved by the DAO, the approval must  include
    the DAO-authorized signature.

(s) ADDITIONAL INFORMATION

(1) Refer to TCCA AD CF-2017-04R3, dated April 1, 2020, for related infor-
    mation.  This TCCA AD may be found in the AD docket at regulations.gov
    under Docket No. FAA-2022-0672.

(2) For more information about this AD contact Joseph Catanzaro, Aerospace
    Engineer, Airframe and Propulsion Section,  FAA,  New York ACO Branch,
    1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-
    7366; 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 (t)(4)
    and (5) of this AD.

(t) 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 May 4, 2020
    (85 FR 17473, March 30, 2020).

(i) Bombardier Service Bulletin 84-28-20,  Revision D,  dated November 23,
    2018.

(ii) Bombardier Service Bulletin 84-28-21 Revision C, dated July 13, 2018.

(iii) Bombardier Service Bulletin 84-28-26, Revision A, dated November 29,
      2018.

(iv) Bombardier Q400 Dash 8 (Bombardier) Temporary Revision ALI-0192 dated
     April 24, 2018.

(v) Q400 Dash 8 (Bombardier) Temporary Revision ALI-0193,  dated April 24,
    2018.

(4) 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
    North America (toll-free): 855-310-1013,  Direct: 647-277-5820;  email
    thd@dehavilland.com; website dehavilland.com.

(5) You may view this service information at the FAA,  Airworthiness Prod-
    ucts Section,  Operational  Safety  Branch,  2200 South 216th St., Des
    Moines, WA.  For information  on the availability  of this material at
    the FAA, call 206-231-3195.

(6) You may view  this service information  that is incorporated by refer-
    ence at the National Archives and Records Administration  (NARA).  For
    information on the availability of this material  at  NARA,  email fr.
    inspection@nara.gov,  or go to: www.archives.gov/federal-register/cfr/
    ibr-locations.html.

Issued on October 25, 2022.  Christina Underwood, Acting Director, Compli-
ance & Airworthiness Division, Aircraft Certification Service.

FOR FURTHER INFORMATION CONTACT: Joseph Catanzaro, Aerospace Engineer, Air
-frame and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart Ave,
Suite 410, Westbury, NY 11590;  telephone 516-228-7366; email 9-avs-nyaco-
cos@faa.gov.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0672; Project Identifier MCAI-2020-01606-T;
Amendment 39-22228; AD 2022-23-01]
RIN 2120-AA64

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

AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2020-04-
20, which applied to certain De Havilland Aircraft of Canada Limited
Model DHC-8-400 series airplanes. AD 2020-04-20 required repetitive
inspections of certain parts for discrepancies that meet specified
criteria, and replacement as necessary; repetitive inspections of
certain parts for damage and wear, and rework of parts; and electrical
bonding checks of certain couplings. AD 2020-04-20 also required
revising the existing maintenance or inspection program, as applicable,
to incorporate new or more restrictive airworthiness limitations. For
certain airplanes, AD 2020-04-20 allowed a modification that terminates
the repetitive inspections. This AD continues to require the actions in
AD 2020-04-20, revises the applicability by adding airplanes, and
requires, for certain airplanes, the previously optional rework and
retrofit of certain parts of the fuel system. Doing the rework and
retrofit terminates the retained initial and repetitive inspections in
this AD. This AD was prompted by reports of wear on fuel couplings,
bonding springs, and sleeves as well as fuel tube end ferrules and fuel
component end ferrules, and by a determination that a more robust
lightning ignition protection design is necessary. The FAA is issuing
this AD to address the unsafe condition on these products.

DATES: This AD is effective December 13, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of May 4, 2020
(85 FR 17473, March 30, 2020).

ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2022-0672; 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 North America (toll-free): 855-310-1013, Direct: 647-
277-5820; email thd@dehavilland.com; website dehavilland.com.
You may view this service information at the FAA,
Airworthiness Products Section, Operational Safety Branch, 2200 South
216th St., 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-2022-0672.

FOR FURTHER INFORMATION CONTACT: Joseph Catanzaro, Aerospace Engineer,
Airframe and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart
Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7366; email 9-avs-
nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2020-04-20, Amendment 39-19857 (85 FR
17473, March 30, 2020) (AD 2020-04-20). AD 2020-04-20 applied to
certain De Havilland Aircraft of Canada Limited Model DHC-8-400 series
airplanes. AD 2020-04-20 required repetitive inspections of certain
parts for discrepancies that meet specified criteria, and replacement
as necessary; repetitive inspections of certain parts for damage and
wear, and rework of parts; and electrical bonding checks of certain
couplings. AD 2020-04-20 also required revising the existing
maintenance or inspection program, as applicable, to incorporate new or
more restrictive airworthiness limitations. For certain airplanes, AD
2020-04-20 allowed a modification that terminated the repetitive
inspections. The FAA issued AD 2020-04-20 to address wear on fuel
couplings, bonding springs, and sleeves as well as fuel tube end
ferrules and fuel component end ferrules, which could reduce the
integrity of the electrical bonding paths through the fuel line and
components, and ultimately lead to fuel tank ignition in the event of a
lightning strike.
The NPRM published in the Federal Register on June 9, 2022 (87 FR
35128). The NPRM was prompted by AD CF-2017-04R3, dated April 1, 2020,
issued by Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada (referred to after this as the MCAI). The MCAI
states that wear has been detected on fuel couplings, bonding springs,
and sleeves as well as fuel tube end ferrules and fuel component end
ferrules. The MCAI also states that a more robust lightning ignition
protection design is necessary. The MCAI states that such wear could
reduce the integrity of the electrical bonding paths through the fuel
line and components, and ultimately lead to fuel tank ignition in the
event of a lightning strike.
You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2022-0672.
In the NPRM, the FAA proposed to continue to require the actions in
AD 2020-04-20, revise the applicability by adding airplanes, and
require, for certain airplanes, the previously optional rework and
retrofit of certain parts of the fuel system.
The FAA issued a supplemental notice of proposed rulemaking (SNPRM)
to amend 14 CFR part 39 to supersede AD 2020-04-20. The SNPRM published
in the Federal Register on August 31, 2022 (87 FR 53424) (the SNPRM).
The SNPRM was prompted by the FAA's determination that the NPRM
inadvertently limited the proposed new terminating rework and retrofit
to airplanes that had accomplished certain service information. In
addition, the FAA determined that the optional terminating action
specified in AD 2020-04-20, and corresponding credit, should be carried
over to this AD. In the SNPRM, the FAA proposed to continue to require
the actions in AD 2020-04-20, revise the applicability by adding
airplanes, and require, for certain airplanes, the previously optional
rework and retrofit of certain parts of the fuel system. The FAA is
issuing this AD to address the unsafe condition on these products.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from the Air Line Pilots Association,
International (ALPA) who supported the SNPRM without change.

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
comment 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, this AD is adopted as proposed in the SNPRM.
None of the changes will increase the economic burden on any operator.

Related Service Information Under 1 CFR Part 51

This AD requires the following service information, which the
Director of the Federal Register approved for incorporation by
reference as of May 4, 2020 (85 FR 17473, March 30, 2020).
Bombardier Service Bulletin 84-28-20, Revision D, dated
November 23, 2018.
Bombardier Service Bulletin 84-28-21, Revision C, dated
July 13, 2018.
Bombardier Service Bulletin 84-28-26, Revision A, dated
November 29, 2018.
Q400 Dash 8 (Bombardier) Temporary Revision ALI-0192,
dated April 24, 2018.
Q400 Dash 8 (Bombardier) Temporary Revision ALI-0193,
dated April 24, 2018.
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 *

Action Labor cost Parts cost Cost per product Cost on U.S. operators
Retained actions from AD 2020-04-20 268 work-hours x $85 per hour = $22,780 $0 $22,780 $1,230,120
New actions Up to 1,747 work-hours x $85 per hour = Up to $148,495 87,385 Up to $235,880 Up to $12,737,520

* Table does not include estimated costs for revising the existing maintenance
or inspection program.

The FAA has determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although the FAA recognizes that this number may vary from operator to
operator. In the past, the FAA has estimated that this action takes 1
work-hour per airplane. Since operators incorporate maintenance or
inspection program changes for their affected fleet(s), the FAA has
determined that a per-operator estimate is more accurate than a per-
airplane estimate. Therefore, the FAA estimates the total cost per
operator to be $7,650 (90 work-hours x $85 per work-hour).

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 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) 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.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by:

a. Removing Airworthiness Directive (AD) 2020-04-20, Amendment 39-19857
(85 FR 17473, March 30, 2020); and

b. Adding the following new AD: