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2021-19-11 DE HAVILLAND AIRCRAFT OF CANADA LIMITED (TYPE CERTIFICATE PREVIOUSLY HELD BY BOMBARDIER, INC.):
Amendment 39-21729; Docket No. FAA-2021-0312; Project Identifier MCAI-2020-01376-T.

(a) EFFECTIVE DATE

    This airworthiness directive (AD) is effective November 18, 2021.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    This AD applies to De Havilland Aircraft of Canada Limited  (type cer-
    tificate previously held by Bombardier, Inc.) airplanes,  certificated
    in any category, and  identified  in  paragraphs (c)(1) through (4) of
    this AD.

(1) Model DHC-8-102, -103 and -106 airplanes as identified in De Havilland
    Service Bulletin 8-27-123, Revision A, dated September 8, 2020.

(2) Model DHC-8-201 and -202 airplanes as identified in De Havilland Serv-
    ice Bulletin 8-27-123, Revision A, dated September 8, 2020.

(3) Model DHC-8-301, -311 and -315 airplanes as identified in De Havilland
    Service Bulletin 8-27-123, Revision A, dated September 8, 2020.

(4) Model DHC-8-400, -401 and -402 airplanes as identified in De Havilland
    Service Bulletin 84-27-74, Revision B, dated September 8, 2020.

(d) SUBJECT

    Air Transport Association (ATA) of America Code 27, Flight controls.

(e) UNSAFE CONDITION

    This  AD  was  prompted by  reports that  mounting nuts  attaching the
    rudder actuator  bracket to  the vertical  stabilizer have  been found
    cracked or missing due to  hydrogen embrittlement. The FAA is  issuing
    this AD to address the  possible loss of the rudder  actuator bracket,
    which  could  result in  a  dormant disconnection  between  the rudder
    actuator  and  the  vertical   stabilizer.  This  condition,  if   not
    addressed,  could  result in  a  loss of  directional  control of  the
    aircraft.

(f) COMPLIANCE

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

(g) REQUIRED ACTIONS

    Within 8,000 flight hours or 4 years,  whichever is earlier, after the
    effective date  of this  AD: Do  a detailed  visual inspection  of the
    rudder actuator bracket mounting  nuts for missing nuts  or corrosion,
    cracking, or other  damage, in accordance  with paragraph 3.B.  of the
    Accomplishment Instructions of De Havilland Service Bulletin 8-27-123,
    Revision A, dated September 8, 2020; or De Havilland Service  Bulletin
    84-27-74, Revision B, dated September 8, 2020; as applicable.  If  any
    missing nuts or corrosion, cracking, or other damage is found, replace
    the nuts before further flight,  in accordance with paragraph 3.B.  of
    the Accomplishment Instructions of De Havilland Service Bulletin  8-27
    -123,  Revision A,  dated  September 8, 2020; or  De Havilland Service
    Bulletin 84-27-74, Revision B, dated September 8, 2020; as applicable.

(h) CREDIT FOR PREVIOUS ACTIONS

    This paragraph provides credit  for actions required  by paragraph (g)
    of this AD,  if those actions were performed before the effective date
    of this AD using De Havilland Service Bulletin 8-27-123 dated December
    20, 2019;  De Havilland Service Bulletin 84-27-74,  dated December 20,
    2019;  or  De Havilland Service Bulletin 84-27-74,  Revision A,  dated
    January 20, 2020; as applicable.

(i) NO REPORTING REQUIREMENT

    Although  De Havilland  Service Bulletin 8-27-123,  Revision A,  dated
    September 8, 2020 and De Havilland Service Bulletin 84-27-74, Revision
    B, dated September 8, 2020,  specify to submit  certain information to
    the manufacturer, this AD does not include that requirement.

(j) OTHER FAA 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 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.  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.

(k) RELATED INFORMATION

(1) Refer to Mandatory Continuing Airworthiness Information (MCAI) TCCA AD
    CF-2020-34, dated October 6, 2020, 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-2021-
    0312.

(2) For more information about this AD, contact Aziz Ahmed, Aerospace Eng-
    ineer, 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 (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 Service Bulletin 8-27-123, Revision A, dated September 8,
    2020.

(ii) De Havilland Service Bulletin 84-27-74,  Revision B,  dated September
     8, 2020.

(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.

(4) 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.

(5) 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 https://www.archives.gov/federal-register
    /cfr/ibr-locations.html.

Issued on September 7, 2021.  Lance T. Gant,  Director,  Compliance & Air-
worthiness Division, Aircraft Certification Service.

FOR FURTHER INFORMATION 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.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0312; Project Identifier MCAI-2020-01376-T;
Amendment 39-21729; AD 2021-19-11]
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 adopting a new airworthiness directive (AD) for
certain De Havilland Aircraft of Canada Limited Model DHC-8-102, -103,
and -106 airplanes; Model DHC-8-201 and -202 airplanes; Model DHC-8-
301, -311, and -315 airplanes; and Model DHC-8-400, -401, and -402
airplanes. This AD was prompted by reports that mounting nuts attaching
the rudder actuator bracket to the vertical stabilizer have been found
cracked or missing due to hydrogen embrittlement. This AD requires a
one-time inspection of the rudder actuator bracket mounting nuts, and
corrective actions if necessary. The FAA is issuing this AD to address
the unsafe condition on these products.

DATES: This AD is effective November 18, 2021.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of November 18,
2021.

ADDRESSES: For service information identified in this final rule,
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, 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 on the internet at https://www.regulations.gov by searching
for and locating Docket No. FAA-2021-0312.

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-2021-
0312; 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, 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.

FOR FURTHER INFORMATION 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.

SUPPLEMENTARY INFORMATION:

Background

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued TCCA AD CF-2020-34, dated October 6,
2020 (TCCA AD CF-2020-34) (also referred to after this as the Mandatory
Continuing Airworthiness Information, or the MCAI), to correct an
unsafe condition for certain De Havilland Aircraft of Canada Limited
Model DHC-8-102, -103, and -106 airplanes; Model DHC-8-201 and -202
airplanes; Model DHC-8-301, -311, -314, and -315 airplanes; and Model
DHC-8-400, -401, and -402 airplanes. Model DHC-8-314 airplanes are not
certificated by the FAA and are not included on the U.S. type
certificate data sheet; this AD therefore does not include those
airplanes in the applicability. You may examine the MCAI in the AD
docket at https://www.regulations.gov by searching for and locating
Docket No. FAA-2021-0312.
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-8-102, -103, and -106 airplanes;
Model DHC-8-201 and -202 airplanes; Model DHC-8-301, -311, and -315
airplanes; and Model DHC-8-400, -401, and -402 airplanes. The NPRM
published in the Federal Register on April 20, 2021 (86 FR 20459). The
NPRM was prompted by reports that mounting nuts attaching the rudder
actuator bracket to the vertical stabilizer have been found cracked or
missing due to hydrogen embrittlement. The NPRM proposed to require a
one-time inspection of the rudder actuator bracket mounting nuts, and
corrective actions if necessary. The FAA is issuing this AD to address
the possible loss of the rudder actuator bracket, which could result in
a dormant disconnection between the rudder actuator and the vertical
stabilizer. This condition, if not addressed, could result in a loss of
directional control of the aircraft. See the MCAI for additional
background information.

Comments

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

Support for the NPRM

The Air Line Pilots Association, International (ALPA), indicated
its support for the NPRM.

Request To Require Procedure Only

Horizon Air requested that paragraph (g) of the proposed AD be
changed to require only paragraph 3.B. (Procedure) of the
Accomplishment Instructions of the applicable service information.
Horizon stated that requiring paragraph 3.A. (Job Set-up) and paragraph
3.C. (Close-Out) restricts an operator's ability to perform other
maintenance in conjunction with the required actions.
The FAA agrees with the request. Paragraph (g) of this AD has been
changed to require only paragraph 3.B. (Procedure) of the
Accomplishment Instructions of De Havilland Service Bulletin 8-27-123,
Revision A, dated September 8, 2020; or Service Bulletin 84-27-74,
Revision B, dated September 8, 2020; as applicable.

Request To Remove and Replace All Suspect Hardware

A commenter suggested removal and replacement of ``all suspect
hardware.'' The commenter asserted that hydrogen embrittlement would
not be evident by way of visual inspection. The FAA infers a request to
change the requirements of the proposed AD to replace all affected
rudder actuator bracket mounting nuts instead of relying on an
inspection to determine which mounting nuts need replacement.
The FAA disagrees with the request. The FAA notes that the rudder
actuator bracket mounting nuts were installed as required by AD 2012-
04-08, Amendment 39-16964 (77 FR 13193, March 6, 2012), which has a
compliance time of within 6,000 flight hours or 3 years after April 10,
2012, whichever occurs first. Viking confirmed that mounting nuts with
hydrogen embrittlement can show cracking as soon as one week after
being torqued. However, these airplanes have been flying for several
years with the mounting nuts installed and without reports of loss of
directional control of the airplane caused by the mounting nuts. TCCA
and Viking therefore determined, and the FAA agrees, that a one-time
visual inspection and replacement if necessary is sufficient to address
the unsafe condition. This AD has not been changed with regard to this
request.

Conclusion

The FAA reviewed the relevant data, considered the comments
received, and determined that air safety and the public interest
require adopting this final rule with the change described previously
and minor editorial changes. The FAA has 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.
The FAA 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 51

De Havilland has issued Service Bulletin 8-27-123, Revision A,
dated September 8, 2020; and Service Bulletin 84-27-74, Revision B,
dated September 8, 2020. This service information specifies procedures
for doing a detailed visual inspection of the nuts attaching the rudder
actuator brackets to the rear spar. If the nuts are corroded, cracked,
or otherwise damaged, or if they are missing, they are replaced. These
documents are distinct since they apply to different airplane models.
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 would affect 69 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
3 work-hours x $85 per hour = $255
$0
$255
$17,595

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

On-Condition Costs

Action
Labor cost
Parts cost
Cost per product
Nut replacement 2 work-hours x $85 per hour = $170
Minimal
$170

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.

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

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 adding the following new airworthiness
directive: