DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0334; Product Identifier 2017-NM-008-AD; Amendment
39-19039; AD 2017-19-09]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

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

ACTION: Final rule.

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SUMMARY: We are superseding Airworthiness Directive (AD) 2014-25-01,
which applied to certain Bombardier, Inc., Model DHC-8-400 series
airplanes. AD 2014-25-01 required modifying the nose landing gear (NLG)
trailing arm and installing a new pivot pin retention mechanism. This
AD instead requires modifying the NLG shock strut assembly. This AD was
prompted by reports of discrepancies of a certain bolt at the pivot pin
link, resulting in corrosion of the bolt. We are issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective October 24, 2017.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of October 24,
2017.

ADDRESSES: For service information identified in this final rule,
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, 1601 Lind Avenue
SW., Renton, WA. For information on the availability of this material
at the FAA, call 425-227-1221. It is also available on the Internet at
http://www.regulations.gov by searching for and locating Docket No.
FAA-2017-0334.

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-2017-
0334; 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, the regulatory evaluation, any comments received, and other
information. The address for the Docket Office (telephone 800-647-5527) is
Docket Management Facility, 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: Fabio Buttitta, Aerospace Engineer,
Airframe and Mechanical Systems Section, FAA, New York ACO Branch, 1600
Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7303;
fax 516-794-5531.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to supersede AD 2014-25-01, Amendment 39-18042 (79 FR 73808,
December 12, 2014) (``AD 2014-25-01''). AD 2014-25-01 applied to
certain Bombardier, Inc., Model DHC-8-400 series airplanes. The NPRM
published in the Federal Register on May 9, 2017 (82 FR 21484). The
NPRM was prompted by reports of discrepancies of a certain bolt at the
pivot pin link, resulting in corrosion of the bolt. The NPRM proposed
to require modifying the NLG shock strut assembly. We are issuing this
AD to prevent 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.
Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian Airworthiness Directive CF-
2009-29R2, dated December 21, 2016 (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:

Two in-service incidents have been reported on DHC-8 Series 400
aircraft in which the nose landing gear (NLG) trailing arm pivot pin
retention bolt (part number NAS6204-13D) was damaged. One incident
involved the left hand NLG tire which ruptured on take-off.
Investigation determined that the retention bolt failure was due to
repeated contact of the castellated nut with the towing device
including both the towbar and the towbarless rigs. The loss of the
retention bolt allowed the pivot pin to migrate from its normal
position and resulted in contact with and rupture of the tire. The
loss of the pivot pin could compromise retention of the trailing arm
and could result in a loss of directional control due to loss of
nose wheel steering. The loss of an NLG tire or the loss of
directional control could adversely affect the aircraft during take-
off or landing.
To prevent the potential failure of the pivot pin retention
bolt, Bombardier Aerospace has developed a modification which
includes a new retention bolt, a reverse orientation of the
retention bolt and a rework of the weight on wheel (WOW) proximity
sensor cover to provide clearance for the re-oriented retention
bolt.
Since the original issue of this [Canadian] AD [which
corresponds to AD 2010-13-04, Amendment 39-16335 (75 FR 35622, June
23, 2010)], there have been several reports of pivot pin retention
bolts found missing or damaged. Additional investigation determined
that the failures were caused by high contact stresses on the
retention bolt due to excessive frictional torque on the pivot pin
and an adverse tolerance condition at the retention bolt.
Revision 1 of this [Canadian] AD mandated the installation of a
new pivot pin retention mechanism.
Since the issuance of Revision 1 of this [Canadian] AD, there
have been reports of chrome peeling on special bolt part number
47205-1 at the pivot pin link resulting in corrosion of the bolt
substrate layer.
Revision 2 of this [Canadian] AD mandates the installation of
new special bolt part number 47205-3 with additional processing for
increased chrome plating adhesion on aeroplanes equipped with nose
landing gear shock strut assembly part number 47100-19 or any
assembly with Bombardier (BA) Service Bulletin (SB) 84-32-110
incorporated. In addition, Revision 2 of this [Canadian] AD mandates
the installation of a new pivot pin retention mechanism that
includes new special bolt part number 47205-3 on aeroplanes equipped
with nose landing gear shock strut assembly part number 47100-9,
47100-11, 47100-13, 47100-15, or 47100-17 without BA SB 84-32-110
incorporated. The corrective actions of Revision 2 of this
[Canadian] AD cancel and replace the corrective actions of Revision
1 of this [Canadian] AD.

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-2017-0334.

Comments

We gave the public the opportunity to participate in developing
this AD. 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 concurred with the
intent of the NPRM.

Request To Exclude Setup and Closeout Sections

Horizon Air asked that we revise paragraph (g) of the proposed AD
to exclude the ``Job Set-up'' and ``Close Out'' sections of Bombardier
Service Bulletin 84-32-145, Revision A, dated October 18, 2016. Horizon
Air stated that incorporating those sections as a requirement of the AD
restricts an operator's ability to perform other maintenance in
conjunction with incorporation of the referenced service information.
We agree with the commenter's request for the reason provided. We
have revised paragraph (g) of this AD to require accomplishment of only
paragraph 3.B., ``Procedure'' of the Accomplishment Instructions of
Bombardier Service Bulletin 84-32-145, Revision A, dated October 18,
2016.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this AD with the change described previously and minor editorial
changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of this AD.

Related Service Information Under 1 CFR Part 51

Bombardier, Inc., has issued Bombardier Service Bulletin 84-32-145,
Revision A, dated October 18, 2016. The service information describes
procedures for modifying the NLG shock strut assembly by installing a
new, improved pivot pin retention mechanism and a new retention bolt.
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

We estimate that this AD affects 52 airplanes of U.S. registry.
We also estimate that it takes about 2 work-hours per product to
comply with the basic requirements of this AD. The average labor rate
is $85 per work-hour. Required parts will cost about $0 per product.
Based on these figures, we estimate the cost of this AD on U.S.
operators to be $8,840, or $170 per product.

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 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 to
the Director of the System Oversight Division.

Regulatory Findings

We 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. Is not a ``significant rule'' under the DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979);
3. Will not affect intrastate aviation in Alaska; and
4. 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 removing Airworthiness Directive (AD)
2014-25-01, Amendment 39-18042 (79 FR 73808, December 12, 2014), and
adding the following new AD: