DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0458; Product Identifier 2020-NM-029-AD; Amendment
39-21348; AD 2020-25-06]
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: The FAA is adopting a new airworthiness directive (AD) for
certain Bombardier, Inc., Model BD-100-1A10 airplanes. This AD was
prompted by a report that corrosion was found on the shock strut
cylinders during unscheduled maintenance of the nose landing gear
(NLG). This AD requires a modification of the NLG shock strut cylinder.
The FAA is issuing this AD to address the unsafe condition on these
products.

DATES: This AD is effective January 27, 2021.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of January 27,
2021.

ADDRESSES: For service information identified in this final rule,
contact Bombardier, Inc., 200 Cote-Vertu Road West, Dorval,
Quebec H4S 2A3, Canada; North America toll-free telephone 1-866-
538-1247 or direct-dial telephone 1-514-855-2999; email
ac.yul@aero.bombardier.com; internet http://www.bombardier.com. You may
view this service information at the FAA, Airworthiness Products
Section, Operational Safety Branch, 2200 South 216th St., Des Moines,
WA. For information on the availability of this material at the FAA,
call 206-231-3195. It is also available on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2020-0458.

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-2020-
0458; 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 final rule, any comments received, and other information. The
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: Darren Gassetto, Aerospace Engineer,
Mechanical Systems and Administrative Services Section, FAA, New York
ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
telephone 516-228-7323; fax 516-794-5531; email 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian AD CF-2019-43, dated November
8, 2019 (``AD CF-2019-43'') (also referred to as the Mandatory
Continuing Airworthiness Information, or ``the MCAI''), to correct an
unsafe condition for certain Bombardier, Inc., Model BD-100-1A10
airplanes. You may examine the MCAI in the AD docket on the internet at
https://www.regulations.gov by searching for and locating Docket No.
FAA-2020-0458.
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain Bombardier,
Inc., Model BD-100-1A10 airplanes. The NPRM published in the Federal
Register on June 3, 2020 (85 FR 34141). The NPRM was prompted by a
report that corrosion was found on the shock strut cylinders during
unscheduled maintenance of the NLG. The NPRM proposed to require a
modification of the NLG shock strut cylinder. The FAA is issuing this
AD to address corrosion of the NLG, which could result in structural
failure of the NLG. See the MCAI for additional background information.

Comments

The FAA gave the public the opportunity to participate in
developing this final rule. The following presents the comment received
on the NPRM and the FAA's response to that comment.

Request To Revise Certain Compliance Language in the Proposed AD

Flexjet stated that where the compliance section of Bombardier
Service Bulletin 100-32-33, Revision 02, dated September 30, 2019, and
Figure 1 to paragraph (g) of the proposed AD, specify the compliance
time for NLG assemblies with more than 96 months time since new (TSN),
the compliance time does not take into account that the NLG cylinders
with part number (P/N) 40640-3 and P/N 40640-5 serialized (next higher
assembly P/N 40640-105 and subcomponents) are life-limited items with a
7,500 flight cycle discard interval. Flexjet commented that during the
first 96 month inspection, if the operator has high flight cycles, it
may elect to replace the cylinder at that time. Flexjet also commented
that the compliance section of Bombardier Service Bulletin 100-32-33,
Revision 02, dated September 30, 2019, does not take into account that
a new cylinder could be installed at the 96-month inspection and it
also does not address if the cylinder was replaced for another reason
after the 96-month inspection.
Flexjet stated that the proposed AD needs to be specific on
applying to the nose gear cylinder and sleeve part numbers and not the
nose gear or nose gear strut assembly part numbers. Flexjet also stated
that the nose gear cylinder and sleeve are the parts with corrosion and
the primary reason for the service information. Flexjet pointed out
that the sleeve is cut off for inspection of the cylinder and the same
part number sleeve goes back on following the inspection. The FAA
infers that Flexjet was requesting that the language in paragraphs
(g)(1) and (2) of this AD specify that the actions apply to airplanes
with NLG assemblies having NLG cylinder assemblies and sleeves with
certain part numbers.
The FAA disagrees with the comment. While NLG cylinder assemblies
and their subcomponents can be replaced before or after the 96-month
interval inspection, paragraphs 2.B. and 2.C. of the Accomplishment
Instructions of Bombardier Service Bulletin 100-32-33, Revision 02,
dated September 30, 2019, ensure the proper corrective actions are
taken to prevent corrosion with those replaced components when
reassembled on the NLG assembly. This is why the identification on the
NLG assembly modplate is required. In addition, paragraph (f) of this
AD specifies to, ``Comply with this AD within the compliance times
specified, unless already done.'' Therefore, if some of the specified
corrective actions are already complied with, only the remaining corrective
actions in the AD need to be completed to comply with this AD. The FAA has
not changed this AD in this regard.

Conclusion

The FAA reviewed the relevant data, considered the comment
received, and determined that air safety and the public interest
require adopting this final rule as proposed, except for minor
editorial changes. The FAA has determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for addressing the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.

Related Service Information Under 1 CFR Part 51

Bombardier has issued Service Bulletin 100-32-33, Revision 02,
dated September 30, 2019; and Service Bulletin 350-32-009, Revision 02,
dated September 30, 2019. This service information describes procedures
for modification of the NLG shock strut cylinder. These documents are
distinct since they apply to different airplane serial numbers. 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

The FAA estimates that this AD affects 560 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs for Required Actions

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.

Regulatory Findings

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) 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.

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 adding the following new airworthiness
directive (AD):