DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0453; Product Identifier 2018-NM-028-AD; Amendment
39-19732; AD 2019-18-05]
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.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain De Havilland Aircraft of Canada Limited (Type Certificate
Previously Held by Bombardier, Inc.) Model DHC-8-400 series airplanes.
This AD was prompted by reports of the nose landing gear (NLG) locking
in a partially extended position due to loose bushings on the lock link
of the NLG locking mechanism. This AD requires repetitive inspections
of the bushings and the lower lock link of the NLG for discrepancies,
and corrective actions if necessary. This AD also requires replacement
of the lower lock link of the NLG, which terminates the repetitive
inspections. The FAA is issuing this AD to address the unsafe condition
on these products.

DATES: This AD is effective October 31, 2019.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of October 31,
2019.

ADDRESSES: For service information identified in this final rule,
contact De Havilland Aircraft of Canada Ltd., 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. It is also available on the
internet at http://www.regulations.gov by searching for and locating
Docket No. FAA-2018-0453.

Examining the AD Docket

You may examine the AD docket on the internet at http://www.regulations.
gov by searching for and locating Docket No. FAA-2018-
0453; 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 regulatory evaluation, 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: Darren Gassetto, Aerospace Engineer,
Mechanical Systems and Administrative Services Section, New York ACO
Branch, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
telephone 516-228-7323; fax 516-794-5531.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain Bombardier,
Inc., Model DHC-8-400 series airplanes. The NPRM published in the
Federal Register on May 30, 2018 (83 FR 24694). The NPRM was prompted
by reports of the NLG locking in a partially extended position due to
loose bushings on the lock link of the NLG locking mechanism. The NPRM
proposed to require inspecting the bushings and the lower lock link of
the NLG for discrepancies, and corrective actions if necessary.
The FAA issued a supplemental notice of proposed rulemaking (SNPRM)
to amend 14 CFR part 39 by adding an AD that would apply to certain
Bombardier, Inc., Model DHC-8-400 series airplanes. The SNPRM published
in the Federal Register on June 7, 2019 (84 FR 26601). The FAA issued
the SNPRM to add a requirement to replace the lower lock link of the
NLG, which would terminate the repetitive inspections proposed in the
NPRM. The SNPRM also proposed to reduce the applicability in the NPRM.
The FAA is issuing this AD to address excessive free play at the
lock link of the NLG locking mechanism, and consequent inability to
fully retract or deploy the NLG, which could result in collapse of the
NLG and affect the safe landing of the airplane.
Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian AD CF-2018-01R1, dated
January 21, 2019 (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 (Type
Certificate Previously Held by Bombardier, Inc.) Model DHC-8-400 series
airplanes. The MCAI states:

A landing incident took place whereby the aeroplane's nose
landing gear (NLG) was locked in a partially-extended position,
leading to gear collapse upon NLG touch down. The investigation
revealed that the NLG was locked in this position due to the
bushings on the lock link of the NLG locking mechanism becoming
loose. This condition was present due to insufficient interference
fit which resulted in some bushing outer diameter wear and fretting.
A dislodged bushing will also cause the bushing sealant to break.
Broken sealant allows moisture ingress and corrosion that can
accelerate free play buildup. Excessive free play at the lock link
can result in the inability to fully retract or deploy the NLG,
resulting in a risk of NLG collapse on landing.
Bombardier Inc. has developed an inspection to identify and
correct this condition. The original version of this [Canadian] AD
required a repetitive inspection [to detect discrepancies] and
corrective actions based on the inspection findings.
Revision 1 of this [Canadian] AD is issued to modify the NLG
with a lower lock with improved bushing retention and greasing
provisions. Implementing this modification is a terminating action
to this [Canadian] AD. The modification has been introduced in
production, therefore the applicability of this [Canadian] AD has
been reduced. Clarifications have also been made to the retained
text of the original version.

You may examine the MCAI in the AD docket on the internet at http://
www.regulations.gov by searching for and locating Docket No. FAA-2018-
0453.

Comments

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

Request To Revise Certain Requirements

Horizon Air asked that the requirement to do the actions specified
in paragraph (k) of the proposed AD in accordance with paragraph 3.A.
of the Accomplishment Instructions of Bombardier Service Bulletin 84-
32-154, Revision A, dated November 21, 2018, be removed. Horizon Air
stated that the job setup specified in paragraph 3.A. of the referenced
service information does not directly correct the unsafe condition.
Horizon Air would like only the actions specified in paragraph 3.B. of
the referenced service information mandated.
The FAA does not agree with the commenter's request. For some ADs,
the job setup actions in the associated service information do not
affect the actions to correct the unsafe condition. However, for this
AD, the FAA has determined that to adequately perform the corrective
actions the job setup actions specified in Bombardier Service Bulletin
84-32-154, Revision A, dated November 21, 2018, must be accomplished.
Paragraph 3.A., ``Job Set-Up,'' of Bombardier Service Bulletin 84-32-
154, Revision A, dated November 21, 2018, includes specific procedures
for the NLG to be in the correct configuration for the corrective
actions to be done and prevent damage to the equipment. Therefore, the
FAA has not changed this AD in this regard.

Request To Install Post-UTC Aerospace Systems Spare Parts

Horizon Air asked that installation of NLG drag strut assemblies
having part number 47300-7A, 47300-9A, or 47300-11A, serviced in
accordance with UTC Aerospace Systems Vendor Service Bulletin (VSB)
47300-32-138 R3, be allowed as terminating action for the repetitive
inspections. Horizon Air stated that UTC Aerospace Systems VSB 47300-
32-138 R3 can be done on units not installed on the airplane.
The FAA agrees to clarify. NLG drag strut assemblies can be
serviced (lower lock links replaced and affected parts re-identified)
by accomplishing UTC Aerospace Systems VSB 47300-32-138 R3, as
specified in Bombardier Service Bulletin 84-32-154, Revision A, dated
November 21, 2018. However, operators must still show compliance with
paragraph 3.A. and Steps 3.B.(1), 3.B.(4) and 3.B.(5) of the
Accomplishment Instructions of Bombardier Service Bulletin 84-32-154,
Revision A, dated November 21, 2018, for the removal of a unit which
has not been serviced, and installation of a serviced spare unit, in
order to correct the unsafe condition. In addition, paragraph (f) of
this AD specifies ``Comply with this AD within the compliance times
specified, unless already done.'' Therefore, if some of the corrective
actions have been done, only the remaining corrective actions must be
completed to comply with this AD. The FAA has not changed this AD in
this regard.

Explanation of Change Made to This Final Rule

The FAA has revised this final rule to identify the legal name of
the manufacturer as published in the most recent type certificate data
sheet for the affected airplane models.

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 as proposed, except for minor
editorial changes. The FAA has determined that these minor changes:
Are consistent with the intent that was proposed in the
SNPRM for addressing the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the SNPRM.

Related Service Information Under 1 CFR Part 51

Bombardier has issued the following service information:
Service Bulletin 84-32-153, Revision A, dated February 27,
2018, which describes procedures for general visual inspections of the
bushings and the lower lock link of the NLG for discrepancies. The
service information also describes procedures for repair or replacement
of the lock link if any discrepancy is found.
Service Bulletin 84-32-154, Revision A, dated November 21,
2018, which describes procedures for replacement of the existing lock
link with a new lock link.
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 64 airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this AD:

Estimated Costs for Required Actions

The FAA has received no definitive data that enables the agency to
provide cost estimates for the on-condition actions specified in this
AD.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
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.
This AD is issued in accordance with authority delegated by the
Executive Director, Aircraft Certification Service, as authorized by
FAA Order 8000.51C. In accordance with that order, issuance of ADs is
normally a function of the Compliance and Airworthiness Division, but
during this transition period, the Executive Director has delegated the
authority to issue ADs applicable to transport category airplanes and
associated appliances to the Director of the System Oversight Division.

Regulatory Findings

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 (AD):