DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-1064; Project Identifier MCAI-2021-01028-T;
Amendment 39-21856; AD 2021-25-12]
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; request for comments.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2017-19-
09, which applied to certain De Havilland Aircraft of Canada Limited
(Type Certificate Previously Held by Bombardier, Inc.) Model DHC-8-400
series airplanes. AD 2017-19-09 required modifying the nose landing
gear (NLG) shock strut assembly. This new AD requires repetitive
lubrications of the trailing arm of the NLG. This new AD also requires
revising the existing maintenance or inspection program to include new
and revised airworthiness limitations (life limits for certain bolts).
This AD was prompted by reports of a certain bolt being found missing
or having stress corrosion cracking. The FAA is issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective January 5, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of January 5,
2022.
The FAA must receive comments on this AD by February 4, 2022.

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: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday
through Friday, except Federal holidays.
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 referenced 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-2021-1064.

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-
1064; or in person at the Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this AD, any comments received, and other information. The
street address for the Docket Operations office is listed above.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Antariksh Shetty, Aerospace Engineer,
Airframe and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart
Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; fax 516-
794-5531; email 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued AD 2017-19-09, Amendment 39-19039 (82 FR 43829,
September 20, 2017) (AD 2017-19-09), which applied to certain De
Havilland Aircraft of Canada Limited (Type Certificate Previously Held
by Bombardier, Inc.) Model DHC-8-400, -401, and -402 airplanes. AD
2017-19-09 was prompted by reports of discrepancies of a certain bolt
at the pivot pin link, resulting in corrosion of the bolt. AD 2017-19-
09 required modifying the NLG shock strut assembly. The FAA issued AD
2017-19-09 to address failure of the pivot pin retention bolt, which
could result in a loss of directional control or loss of an NLG tire
during takeoff or landing.

Actions Since AD 2017-19-09 Was Issued

Since the FAA issued AD 2017-19-09, the FAA has determined new
actions are necessary to address the unsafe condition. New bolts that
have been installed must be repetitively lubricated and replaced before
reaching their life limit. Failure of the pivot pin retention bolt
could result in loss of directional control or loss of a NLG tire
during takeoff or landing, which could lead to runway excursions. The
actions required by AD 2017-19-09 are not retained in this AD.
Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued TCCA AD CF-2009-29R4, dated October 1,
2021 (TCCA AD CF-2009-29R4) (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-8-401 and -402 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-2021-1064.
This AD was prompted by reports of a certain bolt at the pivot pin
link being found missing or having stress corrosion cracking. The FAA
is issuing this AD to address failure of the pivot pin retention bolt,
which could result in a loss of directional control or loss of an NLG
tire during takeoff or landing. See the MCAI for additional background
information.

Related Service Information Under 1 CFR Part 51

De Havilland Aircraft of Canada Limited has issued Service Bulletin
84-32-167, dated August 12, 2021. This service information describes
procedures for repetitive lubrications of the trailing arm of the NLG,
which include a general visual inspection of the NLG pivot pin
mechanism for discrepancies (i.e., bolt part number (P/N) NAS602-14D is
missing or has damage (e.g., stress corrosion or stress corrosion
cracking)) and replacement of missing or damaged bolts.
De Havilland Aircraft of Canada Limited has also issued Temporary
Revision ALI-0223, dated October 15, 2020. This service information
describes new and revised airworthiness limitations, including life
limits for certain bolts as specified in Structures Safe Life Task 32-
21-01-701 and Task 32-21-01-702.
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 the FAA's 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 issuing this AD
because the FAA evaluated all pertinent information and determined the
unsafe condition exists and is likely to exist or develop on other
products of the same type design.

Requirements of This AD

This AD requires accomplishing the actions described previously for
De Havilland Aircraft of Canada Limited Service Bulletin 84-32-167,
dated August 12, 2021. This AD also requires revising the existing
maintenance or inspection program to include new and revised
airworthiness limitations (life limits for certain bolts).

Differences Between This AD and the MCAI or Service Information

Part I of TCCA AD CF-2009-29R4 requires a modification to the NLG
shock strut assembly within 1,600 flight cycles or 9 months for certain
airplanes. The FAA is currently considering requiring the modification
in order to address the identified unsafe condition. However, the
planned compliance time for the installation of the modification would
allow enough time to provide notice and opportunity for prior public
comment on the merits of the modification. Therefore, this AD does not
include the modification.
Part III of TCCA AD CF 2009-29R4 applies to all airplanes but
specifies to do the actions using De Havilland Aircraft of Canada
Service Bulletin 84-32-167, dated August 12, 2021. The service
information only has instructions for pivot pin retention bolt P/N
NAS6204-14D. Therefore, the repetitive lubrications specified in (i) of
this AD is for airplanes with pivot pin retention bolt P/N NAS6204-14D installed
on the NLG assembly.

Explanation of Change to the Applicability

AD 2017-19-09 did not include serial number (S/N) 4002 in its
applicability but it did identify Model DHC-8-400 airplanes in the
applicability. However, the only Model DHC-8-400 airplane is S/N 4002,
making the reference to Model DHC-8-400 unnecessary. In addition, the
Model DHC-8-400 airplane is not included in TCCA AD CF-2009-29R4.
Therefore, this AD does not apply to the Model DHC-8-400 airplane.
In addition, the FAA has revised the applicability of this AD to
identify model designations as published in the most recent type
certificate data sheet for the affected models.

FAA's Justification and Determination of the Effective Date

An unsafe condition exists that requires the immediate adoption of
this AD without providing an opportunity for public comments prior to
adoption. The FAA has found that the risk to the flying public
justifies waiving notice and comment prior to adoption of this rule
because failure of the pivot pin retention bolt could result in a loss
of directional control or loss of a NLG tire during takeoff or landing,
which could lead to runway excursions. In addition, the compliance time
for the required action is shorter than the time necessary for the
public to comment and for publication of the final rule. Therefore, the
FAA finds good cause that notice and opportunity for prior public
comment are impracticable. In addition, for the reasons stated above,
the FAA finds that good cause exists for making this amendment
effective in less than 30 days.

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this AD. Send your comments to an address listed under
ADDRESSES. Include ``Docket No. FAA-2021-1064; Project Identifier MCAI-
2021-01028-T'' at the beginning of your comments. The most helpful
comments reference a specific portion of the final rule, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend
this final rule because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this final rule.

Confidential Business Information

CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this AD contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this AD, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as ``PROPIN.'' The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this AD. Submissions containing CBI should be sent to
Antariksh Shetty, Aerospace Engineer, Airframe and Propulsion Section,
FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY
11590; telephone 516-228-7300; fax 516-794-5531; email 9-avs-nyaco-cos
@faa.gov. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.

Interim Action

The FAA considers this AD interim action. The FAA is currently
considering requiring the modification to the NLG shock strut assembly
specified in Part I of TCCA AD CF-2009-29R4.

Regulatory Flexibility Act (RFA)

The requirements of the RFA do not apply when an agency finds good
cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and
comment. Because the FAA has determined that it has good cause to adopt
this rule without notice and comment, RFA analysis is not required.

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

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

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

Estimated Costs of On-Condition Actions

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, and
(2) Will not affect intrastate aviation in Alaska.

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:

a. Removing Airworthiness Directive (AD) 2017-19-09, Amendment 39-19039
(82 FR 43829, September 20, 2017); and

b. Adding the following new AD: