DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0634; Product Identifier 2018-NM-050-AD; Amendment
39-19594; AD 2019-05-12]
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 adopting a new airworthiness directive (AD) for certain
Bombardier, Inc., Model CL-600-2C10 (Regional Jet Series 700, 701 &
702) airplanes, Model CL-600-2D15 (Regional Jet Series 705) airplanes,
Model CL-600-2D24 (Regional Jet Series 900) airplanes, and Model CL-
600-2E25 (Regional Jet Series 1000) airplanes. This AD was prompted by
reports of a fractured main landing gear (MLG) orifice support tube
(OST). This AD requires replacing the MLG OST, and revising the
existing maintenance or inspection program, as applicable, to
incorporate new or more restrictive maintenance requirements and
airworthiness limitations. We are issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective May 3, 2019.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of May 3, 2019.

ADDRESSES: For service information identified in this final rule,
contact Bombardier, Inc., 400 Cote Vertu Road West, Dorval,
Quebec H4S 1Y9, Canada; Widebody Customer Response Center North
America toll-free telephone 866-538-1247 or direct-dial telephone 514-
855-2999; fax 514-855-7401; email ac.yul@aero.bombardier.com; internet
http://www.bombardier.com. You may view this 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. It is also available on the internet at http://www.regulations.
gov by searching for and locating Docket No. FAA-2018-0634.

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-2018-
0634; 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, the regulatory evaluation, any comments received, and
other information. The address for Docket Operations (phone: 800-647-
5527) 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: Aziz Ahmed, Aerospace Engineer,
Airframe and Mechanical Systems Section, FAA, New York ACO Branch, 1600
Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7329;
fax 516-794-5531; email 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We 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 CL-600-2C10 (Regional Jet Series 700, 701 & 702) airplanes, Model
CL-600-2D15 (Regional Jet Series 705) airplanes, Model CL-600-2D24
(Regional Jet Series 900) airplanes, and Model CL-600-2E25 (Regional
Jet Series 1000) airplanes. The NPRM published in the Federal Register
on July 12, 2018 (83 FR 32215). The NPRM was prompted by reports of a
fractured MLG OST. The NPRM proposed to require replacing the MLG OST,
and revising the existing maintenance or inspection program, as
applicable, to incorporate new or more restrictive maintenance
requirements and airworthiness limitations.
We are issuing this AD to address a fractured MLG OST, which can
lead to structural damage to the airplane and collapse of the MLG.
Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian AD CF-2018-02, dated January
16, 2018 (referred to after this as the Mandatory Continuing
Airworthiness Information, or ``the MCAI''), to correct an unsafe
condition for certain Bombardier, Inc., Model CL-600-2C10 (Regional Jet
Series 700, 701 & 702) airplanes, Model CL-600-2D15 (Regional Jet
Series 705) airplanes, Model CL-600-2D24 (Regional Jet Series 900)
airplanes, and Model CL-600-2E25 (Regional Jet Series 1000) airplanes.
The MCAI states:

Five cases of fractured Main Landing Gear (MLG) Orifice Support
Tube (OST) have been reported. Subsequent analysis determined that
the MLG OST is unable to withstand the loads generated during a hard
landing event. A MLG OST fracture cannot be detected during routine
maintenance and if not corrected, a fractured MLG OST can lead to
aeroplane structural damage and/or collapse of the MLG.
This [Canadian] AD mandates the replacement of the existing MLG
OSTs with a re-designed part, and the implementation of a new
airworthiness limitation task.

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-2018-
0634.

Comments

We gave the public the opportunity to participate in developing
this final rule. 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 (ALPA), and Endeavor
Air stated their support for the NPRM.

Request To Refer to Revised Service Information

Bombardier stated that Bombardier Service Bulletin 670BA-32-058,
dated September 26, 2016, was being revised to include procedures for
on-wing replacement of the MLG OSTs. This service bulletin was referred
to as the required source of service information for accomplishing the
replacement of the MLG OSTs in the proposed AD. The commenter stated
that it estimated that Bombardier Service Bulletin 670BA-32-058,
Revision A, would be released in October of 2018.
We infer that the commenter is requesting that this AD refer to
Bombardier Service Bulletin 670BA-32-058, Revision A, as the required
source of service information for replacing the MLG OSTs. We agree with
the commenter's request. We have included Bombardier Service Bulletin
670BA-32-058, Revision A, dated November 7, 2018, in this AD.
Bombardier Service Bulletin 670BA-32-058, Revision A, dated November 7,
2018, adds an optional procedure for OST installation. We have
determined that no additional work is required for airplanes that have
accomplished the actions specified in Bombardier Service Bulletin
670BA-32-058, dated September 26, 2016. We have added paragraph (j) to
this AD to provide credit for actions done before the effective date of
this AD using Bombardier Service Bulletin 670BA-32-058, dated September
26, 2016. We have also redesignated the subsequent paragraphs
accordingly.

Request To Clarify Applicability

Envoy Air requested that the applicability of the proposed AD be
clarified by including the MLG shock strut assemblies part numbers (P/
Ns) 49200-9 through 49200-32 with orifice OSTs installed having P/N
49212-3 or 49212-5. The commenter stated that it perceived the intent
of the proposed AD was to address the unsafe condition by replacing in-
service OSTs with re-designed OSTs having P/N 49212-7 or 49212-9. The
commenter observed that OSTs with P/Ns 49212-3 and 49212-5 are not
tracked, however, the MLG shock strut assemblies on which the OSTs are
installed, are tracked.
The commenter explained that the MLG shock strut assemblies on
which OSTs are installed can be replaced in the field and can be moved
among airplanes and operators. The commenter suggested that changing
the applicability to include the part numbers of the MLG shock strut
assemblies and OSTs would allow operators to track the affected OSTs
regardless of where they are installed.
We acknowledge the commenter's request and agree to clarify.
Section 1.A., ``Effectivity,'' of Bombardier Service Bulletin 670BA-32-
058, Revision A, dated November 7, 2018, provides the part numbers and
serial numbers of the affected MLG shock strut assemblies on which the
affected OSTs were installed, and the serial numbers of the airplanes
on which the MLG shock strut assemblies were installed when the
airplane was delivered. We recognize that the affected OSTs are not
easily tracked. Therefore, we have revised figure 1 to paragraph (g) of
this AD to clarify the compliance times by referring to the MLG shock
strut assembly instead of the OST. However, we do not agree to revise
the applicability of this AD, which corresponds with the applicability
of the corresponding Canadian AD. We have coordinated this issue with
Bombardier and determined that the applicability is acceptable. There
is minimal risk for rotation of affected OSTs and expanding the
applicability would require a Supplemental NPRM for additional public
comments, which would further delay issuance of this AD. Therefore, we
have not changed this AD in regard to this issue.

Request To Revise Proposed Compliance Time

Bombardier and Endeavor Air requested that the compliance times in
paragraph (g) of the proposed AD be changed to the number of total
flight cycles accumulated on the MLG shock strut assembly since it was
new instead of the number of total flight cycles accumulated on the MLG
OSTs. Both of the commenters noted that OSTs having P/Ns 49212-3 and
49212-5 are not tracked, however, flight cycles are tracked for the MLG
shock strut assemblies on which the OSTs are installed. Endeavor Air
stated that operators cannot comply with the proposed compliance times
because the OSTs are not tracked and operators would not know when the
OSTs have reached the flight cycle limits specified in paragraph (g) of
the proposed AD. Endeavor Air noted that, because the OST is internal
to the MLG shock strut assembly, MLG shock strut assemblies that have
not been overhauled will have OSTs with the same flight cycle
accumulation as the MLG shock strut assembly, and if an OST had been
replaced it would have been replaced with a new OST having fewer flight
cycles than the MLG shock strut assembly it is installed on. Therefore,
it is unlikely the OST would have accumulated more flight cycles than
the MLG shock strut assembly on which it is installed. Bombardier noted
that, when an OST is removed during repair or overhaul of the MLG shock
strut assembly, it will remain with the MLG shock strut assembly when
it is returned to service.
We agree with the commenters' requests. Operators can use the total
flight cycles on the MLG shock strut assembly since new, but not since
overhaul, to determine the applicable compliance time. If an MLG shock
strut assembly is overhauled and the OST is removed, if it is a
serviceable OST, it will typically be re-installed on the overhauled
MLG shock strut assembly. We have revised figure 1 to paragraph (g) of
this AD to clarify the compliance times.

Request To Allow Replacement of OSTs Using Alternative Methods

Endeavor Air requested that the proposed AD allow approval and
credit for replacement of OSTs using methods other than following the
procedures in Bombardier Service Bulletin 670BA-32-058, dated September
26, 2016. The commenter stated that operators might have replaced
affected OSTs after a non-routine event or after sending an MLG shock
strut assembly out for repair or overhaul. The commenter noted that
Bombardier has issued Reference Instruction Letter (RIL) 5096, Revision
C, dated June 20, 2017, for replacement of OSTs after a suspected hard
landing. The commenter noted that the Bombardier RIL refers to the same
vendor service information that is specified in Bombardier Service
Bulletin 670BA-32-058, dated September 26, 2016, for accomplishing
replacement of the OSTs. The commenter specifically requested that
paragraph (g) of the proposed AD be revised, or a new paragraph
created, to provide credit for MLG shock strut assemblies that have new
OSTs installed using the Bombardier RIL, the applicable vendor service
information, or the applicable vendor component maintenance manual. The
commenter noted that maintenance repair organizations will replace OSTs
using the applicable vendor service bulletin and not Bombardier Service
Bulletin 670BA-32-058, dated September 26, 2016.
We do not agree with the commenter's request. We contacted
Bombardier and Bombardier stated that the Bombardier RIL provides
procedures for replacing an OST following a high-load landing, and does
not specify that the replacement OSTs must have P/N 49212-7 or 49212-9.
In addition, Bombardier Service Bulletin 670BA-32-058, dated September
26, 2016, includes certain leak checks that must be done; those leak
checks are not specified in the Bombardier RIL. We have not changed
this AD in regard to this issue.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this final rule with the changes 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 addressing 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 final
rule.

Related Service Information Under 1 CFR Part 51

Bombardier has issued Service Bulletin 670BA-32-058, Revision A,
dated November 7, 2018. The service information describes procedures
for replacing each MLG OST.
Bombardier has also issued CRJ700/900/1000 Airworthiness
Limitations Temporary Revision ALI-0593, dated December 18, 2017. The
service information describes new life limits for the MLG OSTs.
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 542 airplanes of U.S. registry. We
estimate the following costs to comply with this AD:

Estimated Costs

* We have received no definitive data that would enable us to provide cost
estimates for the parts cost in this AD.

We have determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although we recognize that this number may vary from operator to
operator. In the past, we have estimated that this action takes 1 work-
hour per airplane. Since operators incorporate maintenance or
inspection program changes for their affected fleet(s), we have
determined that a per-operator estimate is more accurate than a per-
airplane estimate. Therefore, we estimate the total cost per operator
to be $7,650 (90 work-hours x $85 per work-hour).

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 and
associated appliances to the Director of the System Oversight Division.

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) 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 adding the following new airworthiness
directive (AD):