DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0334; Directorate Identifier 2017-NM-008-AD]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede Airworthiness Directive (AD) 2014-25-
01, for certain Bombardier, Inc., Model DHC-8-400 series airplanes. AD
2014-25-01 currently requires modifying the nose landing gear (NLG)
trailing arm and installing a new pivot pin retention mechanism. Since
we issued AD 2014-25-01, we have received reports of discrepancies of a
certain bolt at the pivot pin link, resulting in corrosion of the bolt.
This proposed AD would instead require modifying the NLG shock strut
assembly. We are proposing this AD to address the unsafe condition on
these products.

DATES: We must receive comments on this proposed AD by June 23, 2017.

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: Deliver to Mail address above 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 Airplane Directorate, 1601 Lind Avenue SW., Renton,
WA. For information on the availability of this material at the FAA,
call 425-227-1221.

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 proposed AD, the regulatory evaluation, any comments
received, and other information. The street address for the Docket
Operations office (telephone 800-647-5527) is in the ADDRESSES section.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Fabio Buttitta, Aerospace Engineer,
Airframe and Mechanical Systems Branch, ANE-171, FAA, New York Aircraft
Certification Office, 1600 Stewart Avenue, Suite 410, Westbury, NY
11590; telephone 516-228-7303; fax 516-794-5531.

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or
arguments about this proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include "Docket No. FAA-2017-0334;
Directorate Identifier 2017-NM-008-AD" at the beginning of your
comments. We specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of this proposed AD. We
will consider all comments received by the closing date and may amend
this proposed AD 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 proposed AD.

Discussion

On November 28, 2014, we issued AD 2014-25-01, Amendment 39-18042
(79 FR 73808, December 12, 2014) ("AD 2014-25-01"), for certain
Bombardier, Inc., Model DHC-8-400 series airplanes. AD 2014-25-01 was
prompted by a report of several missing or damaged pivot pin retention
bolts. AD 2014-25-01 requires modifying the NLG trailing arm and
installing a new pivot pin retention mechanism. We issued AD 2014-25-01
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 take-off
or landing.

Since we issued AD 2014-25-01, we have received reports of missing
or damaged pivot pin retention bolts and chrome peeling on special bolt
part number 47205-1 at the pivot pin link, resulting in corrosion of
the bolt substrate layer. Therefore, we have determined that the
actions required by AD 2014-25-01 do not address the identified unsafe
condition.

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.

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.

FAA's Determination and Requirements of This Proposed AD

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.

Costs of Compliance

We estimate that this proposed AD affects 52 airplanes of U.S.
registry.

We also estimate that it would take about 2 work-hours per product
to comply with the basic requirements of this proposed AD. The average
labor rate is $85 per work-hour. Required parts would cost about $0 per
product. Based on these figures, we estimate the cost of this proposed
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.

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. 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.

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 removing Airworthiness Directive (AD)
2014-25-01, Amendment 39-18042 (79 FR 73808, December 12, 2014), and
adding the following new AD: