DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0453; Product Identifier 2018-NM-028-AD]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (SNPRM); reopening
of comment period.

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SUMMARY: We are revising an earlier proposal for certain Bombardier,
Inc., Model DHC-8-400 series airplanes. This action revises the notice
of proposed rulemaking (NPRM) by adding a requirement to replace the
lower lock link of the nose landing gear (NLG), which would terminate
the repetitive inspections proposed in the NPRM. This action also
reduces the applicability in the NPRM. We are proposing this
airworthiness directive (AD) to address the unsafe condition on these
products. Since these actions would impose an additional burden over
those in the NPRM, we are reopening the comment period to allow the
public the chance to comment on these changes.

DATES: The comment period for the NPRM published in the Federal
Register on May 30, 2018 (83 FR 24694), is reopened.

We must receive comments on this SNPRM by July 22, 2019.

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 http://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 NPRM, contact
Bombardier, Inc., Q-Series Technical Help Desk, 123 Garratt Boulevard,
Toronto, Ontario M3K 1Y5, Canada; telephone: 416-375-4000; fax: 416-
375-4539; email: thd.qseries@aero.bombardier.com; internet:
http://www.bombardier.com. You may view this referenced 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 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 SNPRM, the regulatory evaluation, any comments received, and other
information. The street address for Docket Operations (phone: 800-647-
5527) is listed above. Comments will be available in the AD docket
shortly after receipt.

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:

Comments Invited

We invite 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-2018-0453;
Product Identifier 2018-NM-028-AD" at the beginning of your comments.
We specifically invite comments on the overall regulatory, economic,
environmental, and energy aspects of this SNPRM. We will consider all
comments received by the closing date and may amend this
SNPRM based on those comments.

We will post all comments we receive, without change, to
http://www.regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this SNPRM.

Discussion

We issued an 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 a lock link of the
NLG locking mechanism. The NPRM proposed to require repetitive
inspections of the bushings and the lower lock link of the NLG for
discrepancies, and corrective actions if necessary. We are 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.

Actions Since the NPRM Was Issued

Since we issued the NPRM, we have determined that to adequately
address the unsafe condition, it is necessary to require replacement of
the NLG lower lock link with a new lower lock link having a new
configuration.

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian AD CF-2018-01R1, dated
February 4, 2018 (referred to after this as the Mandatory Continuing
Airworthiness Information, or "the MCAI"), to correct an unsafe
condition for certain 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.

Discrepancies include any signs of migration of the bushings,
broken or missing edge sealant, diagonal paint cracks on the sealant,
and paint stripe misalignment. 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

We gave the public the opportunity to participate in developing
this proposed AD. We considered the comments received.

Request To Include Revised Service Information

Horizon Air asked that Bombardier Service Bulletin 84-32-153,
Revision A, dated February 27, 2018, be incorporated into the proposed
AD (in the NPRM). Horizon Air added that a credit paragraph should also
be included for the original issue of the referenced service
information.

We partially agree with the commenter's request. We have revised
this proposed AD to identify Bombardier Service Bulletin 84-32-153,
Revision A, dated February 27, 2018, as the appropriate source of
service information for the inspection specified in paragraph (g) of
this proposed AD. Revision A merely clarifies certain actions and
corrects a certain task number, and adds no new work. We have added
paragraph (j) to this proposed AD to provide credit for actions done
before the effective date of this AD using the original issue of the
referenced service information. However, for clarification, we have
included the correct task number for greasing all drag strut joints,
which is AMM Task 12-20-01-640-802. Bombardier Service Bulletin 84-32-
153, dated September 22, 2017, specifies AMM Task 12-20-01-640-803,
which is incorrect. We have redesignated subsequent paragraphs
accordingly.

Request To Add Terminating Action for Repetitive Inspections

Horizon Air asked that we include an option for terminating action
for the repetitive inspections required by paragraph (g) of the
proposed AD (in the NPRM). Horizon Air stated that Bombardier Service
Bulletin 84-32-154, Revision A, dated November 21, 2018, includes a
modification that involves reconfiguration of the lower lock link of
the NLG by adding new bushings with improved retention and greasing
provisions.

We partially agree with the commenter's request. We agree to
include terminating action for the repetitive inspections, but to
adequately address the unsafe condition, we have determined that it is
necessary to mandate this action instead of providing it as an option.
We have added paragraph (k) of this proposed AD to require the
modification, which would terminate the repetitive inspections
specified by paragraph (g) of this proposed AD. We have redesignated
subsequent paragraphs accordingly.

Request To Include Global Alternative Method of Compliance (AMOC)

Horizon Air asked that we incorporate Global AMOC AARDG-2018/A02 to
Canadian AD CF-2018-01 into the FAA proposed AD (in the NPRM). Horizon
Air stated that this global AMOC provides the initial compliance time
for lower lock links of the NLG that have been repaired based on flight
cycles accumulated since repair, instead of total flight cycles
accumulated. Horizon Air added that justification for this AMOC was
that repair of the lower lock link in accordance with the applicable
component maintenance manual yields the same bushing retention
properties as a new part.

We agree with the commenter's request. Canadian AD CF-2018-01R1
added compliance times for a repaired or replaced NLG lower lock link.
Therefore, we have included paragraph (h) in this proposed AD to allow
the compliance times to be measured from the time of repair or
replacement of the existing lower lock link for a repair or replacement
that was done using a specified method.

Request To Exclude Setup and Closeout Actions

Horizon Air asked that the job setup and closeout actions specified
in Bombardier Service Bulletin 84-32-153, Revision A, dated February
27, 2018, be excluded from the requirements of paragraph (g) of the
proposed AD (in the NPRM). Horizon Air stated that these
actions do not directly correct the unsafe condition. Horizon Air added
that incorporating these actions restricts an operator's ability to
perform other maintenance in conjunction with incorporation of the
referenced service information.

We partially agree with the commenter's request. We agree to remove
the closeout actions, but to adequately perform the corrective actions
the job setup actions specified in Bombardier Service Bulletin 84-32-
153, Revision A, dated February 27, 2018, must be included. Paragraph
3.A., "Job Set-Up," of Bombardier Service Bulletin 84-32-153,
Revision A, dated February 27, 2018, includes specific airplane
maintenance manual tasks and instructions that properly establish a
baseline needed to evaluate excessive play at the lower lock link of
the NLG locking mechanism, and correctly address the unsafe condition.
In addition, the operator is directed to paragraph 3.A.(5) of the Job
Setup section in the Accomplishment Instructions of Bombardier Service
Bulletin 84-32-153, Revision A, dated February 27, 2018, for the
applicable corrective action. Therefore, we have revised the
requirements of paragraph (g) accordingly.

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 an inspection of the bushings and
the lower lock link of the NLG for discrepancies. The service
information also describes procedures for repair or replacement of a
discrepant lock link.
Service Bulletin 84-32-154, Revision A, dated November 21,
2018, which describes procedures for replacement of the existing lower
lock link with a new configuration 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.

FAA's Determination and Requirements of This SNPRM

This product has been approved by the aviation authority of another
country, and is approved for operation in the United States. Pursuant
to our bilateral agreement with the State of Design Authority, we have
been notified of the unsafe condition described in the MCAI and service
information referenced above. We are proposing this AD because we
evaluated all pertinent information and determined an unsafe condition
exists and is likely to exist or develop on other products of the same
type design.
Certain changes described above expand the scope of the NPRM. As a
result, we have determined that it is necessary to reopen the comment
period to provide additional opportunity for the public to comment on
this SNPRM.

Costs of Compliance

We estimate that this proposed AD affects 64 airplanes of U.S. registry.
We estimate the following costs to comply with this proposed AD:

Estimated Costs

We have received no definitive data that enables us to provide cost
estimates for the on-condition actions specified in 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.

We are 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 proposed 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

We 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.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive (AD):