DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0548; Product Identifier 2017-NM-184-AD]
RIN 2120-AA64

Airworthiness Directives; De Havilland Aircraft of Canada Limited
(Type Certificate Previously Held by Bombardier, Inc.) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Proposed rule; withdrawal.

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SUMMARY: The FAA is withdrawing a notice of proposed rulemaking (NPRM)
that published in the Federal Register on June 22, 2018, regarding an
unsafe condition with certain Bombardier, Inc. Model DHC-8-400 series
airplanes. Since issuance of the NPRM, the FAA determined that
additional actions are necessary to address the unsafe condition and
that the applicability should be expanded to include additional
airplane serial numbers. Accordingly, the NPRM is withdrawn.

DATES: As of May 4, 2020, the proposed rule, which was published in the
Federal Register on June 22, 2018 (83 FR 29059), is withdrawn.

ADDRESSES:

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2018-0548;
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 AD action, the regulatory evaluation, any comments received, and
other information. The street 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: Joseph Catanzaro, Aerospace Engineer,
Propulsion Section, FAA, New York ACO Branch, 1600 Stewart Avenue,
Suite 410, Westbury, NY 11590; telephone 516-228-7366; fax 516-794-
5531.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued an NPRM that proposed to amend 14 CFR part 39 by
adding an AD that would have applied to the specified products. The
NPRM was published in the Federal Register on June 22, 2018 (83 FR
29059). The NPRM would have required, depending on airplane
configuration: Increasing the hole size in the collector tank partition
wall, inspecting the motive flow line for damage, and replacing the
associated grommet and motive flow line; replacing the affected single
nut plate brackets and standoffs at the affected stations on the motive
flow line and pressure relief line; and inspecting the motive flow line
and vent line at certain wing stations, and inspecting the fuel tubes,
to verify that an appropriate clearance has been maintained between the
fuel tubes and their support brackets, and applicable corrective
actions. The NPRM was prompted by a report of broken P-clamps on the
pressure relief line and the motive flow line in the left and right
fuel tanks, and fouling conditions between the motive flow line and the
collector tank partition wall in both fuel tanks. The NPRM proposed to
correct an unsafe condition for the specified products.

Actions Since the NPRM Was Issued

Since issuance of the NPRM, the FAA has determined that additional
information was needed in the service information regarding the
relocation of certain TeflonTM sleeves and that inaccurate
production and maintenance manual instructions could have caused
TeflonTM sleeves to be incorrectly installed on the vent
line. The incorrect installation of Teflon TM sleeves could
lead to arcing between the vent line and airplane structure, resulting
in possible fuel tank ignition, in the event of a lightning strike. In
light of this information, the FAA is considering further rulemaking.

In addition, Bombardier revised Service Bulletin 84-28-19 and
issued additional service information to provide instructions regarding
the proper installation of TeflonTM sleeves on the vent line
by providing electrical isolation to preclude the risk of lightning
strike-induced fuel tank ignition, and installation of
TeflonTM sleeves on the vent line at additional wing
stations. The FAA has also determined that the applicability should be
expanded to include additional airplane serial numbers. Furthermore,
the FAA has determined that to adequately address the unsafe condition,
the airworthiness limitations should be revised and that the use of
certain maintenance procedures should be prohibited.

Withdrawal of the NPRM constitutes only such action and does not
preclude the FAA from further rulemaking on this issue, nor does it
commit the FAA to any course of action in the future.

Explanation of Change to Manufacturer's Name Specified in the NPRM

The FAA has revised references to the manufacturer's name specified
in the NPRM to identify the manufacturer name as published in the most
recent type certificate data sheet for the affected models.

FAA's Conclusion

Upon further consideration, the FAA has determined that the NPRM
does not adequately address the identified unsafe condition.
Accordingly, the NPRM is withdrawn.

Regulatory Findings

Since this action only withdraws an NPRM, it is neither a proposed
nor a final rule. This action therefore is not covered under Executive
Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Withdrawal

Accordingly, the notice of proposed rulemaking, Docket No. FAA-2018-
0548, which was published in the Federal Register on June 22, 2018 (83
FR 29059), is withdrawn.

Issued on April 23, 2020. Lance T. Gant, Director, Compliance & Airworthi-
ness Division, Aircraft Certification Service.