DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0493; Product Identifier 2019-NM-043-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: The FAA proposes to supersede Airworthiness Directive (AD)
2011-18-15, which applies to certain Bombardier, Inc., Model DHC-8-400
series airplanes. AD 2011-18-15 requires initial and repetitive torque
checks of the bolt preload; detailed inspection of the barrel nuts and
cradle for cracking, pitting, and corrosion if the bolt preload is
correct; and replacement of hardware if necessary. Since the FAA issued
AD 2011-18-15, the agency has determined that incorporation of a new
design change is necessary to address the root cause of the failure of
the barrel nuts. This proposed AD would retain the existing
requirements and add new inspections and replacement of certain
hardware, which would terminate the repetitive torque checks and
inspections. This AD also removes airplanes from the applicability. The
FAA is proposing this AD to address the unsafe condition on these
products.

DATES: The FAA must receive comments on this proposed AD by August 23, 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: 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; phone: 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-2019-
0493; 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 NPRM, the regulatory evaluation, any comments received, and other
information. The street address for Docket Operations is listed above.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Andrea Jimenez, Aerospace Engineer,
Airframe and Propulsion Section, FAA, New York ACO Branch, 1600 Stewart
Avenue, Suite 410, Westbury, NY 11590; phone: 516-228-7330; fax: 516-
794-5531; email: 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites 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-2019-0493;
Product Identifier 2019-NM-043-AD" at the beginning of your comments.
The FAA specifically invites comments on the overall regulatory,
economic, environmental, and energy aspects of this proposed AD. The
FAA will consider all comments received by the closing date and may
amend this proposed AD based on those comments.

The FAA will post all comments received, without change, to
http://www.regulations.gov, including any personal information you provide.
The FAA will also post a report summarizing each substantive verbal
contact received about this proposed AD.

Discussion

The FAA issued AD 2011-18-15, Amendment 39-16797 (76 FR 54093,
August 31, 2011) ("AD 2011-18-15"), for certain Bombardier, Inc.,
Model DHC-8-400 series airplanes. AD 2011-18-15 requires initial and
repetitive torque checks of the bolt preload; detailed inspection of
the barrel nuts and cradle for cracking, pitting, and corrosion if the
bolt preload is correct; and replacement of hardware if necessary. AD
2011-18-15 resulted from in-service reports of cracked barrel nuts
found at the front spar locations of the wing-to-fuselage attachment
joints, and reports of a loose washer in the barrel nut assembly. The
FAA issued AD 2011-18-15 to address cracked barrel nuts and a loose
washer in the barrel nut assembly, which could result in failure of the
barrel nuts, compromising the structural integrity of the wing-to-
fuselage attachments, and possible separation of the wing from the
airplane during flight.

Actions Since AD 2011-18-15 Was Issued

Since the FAA issued AD 2011-18-15, the manufacturer has developed
a design change (replacement of the existing wing front spar barrel
nuts with new barrel nuts that are more resistant to hydrogen
embrittlement, and installation of new bolts and pre-load indicating
washers). The FAA has determined that the design change will address
the root cause of the failure of the barrel nuts.

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian AD
CF-2011-24R1, dated January 21, 2019 (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:

There have been several in-service reports of cracked barrel
nuts found at the front spar locations of the wing to fuselage
attachment joints. Additionally, three operators have reported
finding a loose washer in the barrel nut assembly. Failure of the
barrel nuts could compromise the structural integrity of the wing to
fuselage attachments.

The investigation determined that these cracks are due to
hydrogen embrittlement.

The original version of this [Canadian] AD mandated initial and
repetitive detailed inspections of the barrel nuts, part number (P/N)
DSC228-16.

Since the original version of this [Canadian] AD, Bombardier
Inc. has developed a design change to address the root cause of the
failure of the barrel nuts. This design change replaces the existing
wing front spar barrel nuts, P/N DSC228-16, with new Inconel 718
barrel nuts, P/N B0203072-16S, which are more resistant to hydrogen
embrittlement. The design change also includes new bolts and new
pre-load indicating washers.

Revision 1 of this [Canadian] AD mandates this design change as
a terminating action to the repetitive inspection requirements of
Part II of this [Canadian] AD. A torque verification has also been
introduced to address loose washers in the barrel nut assembly.

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-2019-0493.

Related Service Information Under 1 CFR Part 51

Bombardier has issued the following service information.

Bombardier Alert Service Bulletin A84-57-25, Revision A,
dated July 16, 2018. This service information describes procedures for
initial and repetitive torque checks of the bolt preload, detailed
inspection of the barrel nuts and cradle for cracking, pitting, and
corrosion if the bolt preload is correct, and replacement of hardware
if necessary.

Bombardier Service Bulletin 84-57-26, Revision C, dated
July 16, 2018. This service information describes procedures for a
visual inspection of the saddle washer and retainer for any damage
(cracks) and corrosion, and replacement of the existing wing front spar
barrel nuts, bolts, and pre-load indicating washers.

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 our 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 proposing this AD
because the agency evaluated all the relevant information and
determined the unsafe condition described previously is likely to exist
or develop on other products of the same type design.

Proposed Requirements of This NPRM

This proposed AD would retain all of the requirements of AD 2011-
18-15. This proposed AD would also require accomplishing the actions
specified in the service information described previously, which would
terminate the repetitive torque checks and inspections and the
corrective actions for incorrect bolt preload.

Revised Applicability

The FAA also revised the applicability of this AD from what was
specified in AD 2011-18-15 to remove airplane serial numbers 4438 and
subsequent. The terminating actions specified in this proposed AD are
accomplished on those airplanes during production.

Costs of Compliance

The FAA estimates that this proposed AD affects 54 airplanes of
U.S. registry.

The FAA estimates the following costs to comply with this proposed AD:

Estimated Costs for Required Actions

The FAA has received no definitive data that would enable us to
provide cost estimates for the on-condition repairs 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.

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 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

The FAA 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 removing Airworthiness Directive (AD)
2011-18-15, Amendment 39-16797 (76 FR 54093, August 31, 2011), and
adding the following new AD: