DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1404; Project Identifier MCAI-2023-00451-T;
Amendment 39-22584; AD 2023-21-12]
RIN 2120-AA64

Airworthiness Directives; MHI RJ Aviation ULC (Type Certificate
Previously Held by Bombardier, Inc.) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all
MHI RJ Aviation ULC Model CL-600-2B19 (Regional Jet Series 100 & 440)
airplanes. This AD was prompted by a report of missing insulation in
the engine pylon area. This AD requires, for certain airplanes,
inspecting the engine pylon structure for discrepancies and repair if
necessary. This AD also requires revising the existing maintenance or
inspection program, as applicable, to incorporate a new certification
maintenance requirement (CMR) task. The FAA is issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective December 26, 2023.

The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of December 26, 2023.

ADDRESSES:

AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2023-1404; 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 mandatory continuing airworthiness
information (MCAI), 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.

Material Incorporated by Reference:

For service information identified in this final rule,
contact MHI RJ Aviation Group, Customer Response Center, 3655 Ave. des
Grandes-Tourelles, Suite 110, Boisbriand, Qu[eacute]bec J7H 0E2 Canada;
North America toll-free telephone 833-990-7272 or direct-dial telephone
450-990-7272; email: mhirj.com">thd.crj@mhirj.com; website: mhirj.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 at
regulations.gov under Docket No. FAA-2023-1404.

FOR FURTHER INFORMATION CONTACT: Fatin Saumik, Aviation Safety
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
telephone 516-228-7300; email 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to all MHI RJ Aviation ULC
Model CL-600-2B19 (Regional Jet Series 100 & 440) airplanes. The NPRM
published in the Federal Register on July 12, 2023 (88 FR 44226). The
NPRM was prompted by AD CF-2023-19, dated March 13, 2023 (Transport
Canada AD CF-2023-19) (also referred to after this as the MCAI), issued
by Transport Canada, which is the aviation authority for Canada. The
MCAI states there was a report of a missing 12-inch piece of insulation
in the 14th stage bleed ducts installed in both left hand (LH) and
right hand (RH) engine pylon areas.

In the NPRM, the FAA proposed to require, for certain airplanes,
inspecting the engine pylon structure for discrepancies and repair if
necessary. The NPRM also proposed to require revising the existing
maintenance or inspection program, as applicable, to incorporate a new
CMR task.

The FAA is issuing this AD to address missing or damaged insulation
in the engine pylon area. The unsafe condition, if not addressed, could
result in the bleed duct to radiate heat to the surrounding structure
and, if not corrected, could lead to the loss of the structural
integrity of the engine pylon and possible loss of the engine.

You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2023-1404.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from Air Line Pilots Association,
International (ALPA) who supported the NPRM without change.

The FAA received additional comments from Air Wisconsin Airlines
and MHI RJ Aviation ULC (MHI RJ). The following presents the comments
received on the NPRM and the FAA's response to each comment.

Request To Refer New Temporary Revision

MHI RJ requested that the FAA revise the proposed AD to refer to
MHI RJ Temporary Revision 2A-77, dated May 8, 2023, which was issued to
revise the phase-in (initial) compliance time in MHI RJ Temporary
Revision 2A-76, dated September 29, 2022, from 40 months to 48 months.

The FAA concurs with the request and has revised paragraph (h) of
this AD to refer to MHI RJ Temporary Revision 2A-77, dated May 8, 2023,
for the new CMR task. The FAA has also provided credit for using MHI RJ
Temporary Revision 2A-76, dated September 29, 2022, in paragraph (j)(2)
of this AD. The CMR task and interval is the same in both temporary
revisions. In addition, there is no change to initial compliance time
because paragraph (j) of the proposed AD did not refer to MHI RJ
Temporary Revision 2A-76, dated September 29, 2022, for the initial
compliance time and instead specified "The initial compliance time for
doing the task is within 48 months or 6,600 flight hours, whichever
occurs first after the effective date of this AD." The compliance time
change in MHI RJ Temporary Revision 2A-77, dated May 8, 2023, is within
the initial compliance time specified in this AD.

Request To Revise Compliance Time

MHI RJ stated it noticed that the FAA is re-starting the clock in
paragraph (h) of the proposed AD from the effective date of the AD
rather than the issue date of the temporary revision: MHI RJ states
that the task interval should start from September 29, 2022, which is
the issue date of MHI RJ Temporary Revision 2A-76. MHI RJ stated that,
in this particular case, the start of the compliance from September 29,
2022, is critical for safety. The FAA infers that MHI RJ is requesting
that the agency reduce the initial compliance time specified in
paragraph (h) of this AD by referring to the September 29, 2022, date
instead of the effective date of this AD.

The FAA acknowledges MHI RJ's concern. However, reducing the
compliance time in paragraph (h) of this AD would result in a more
restrictive compliance time that would necessitate issuing a
supplemental NPRM, delaying the issuance of the final rule. Since the
detailed visual inspection of spar FS654.50, spar FS672.20, and the
firewall for discrepancies specified in paragraph (g) of this AD would
be delayed if a supplemental NPRM is issued, any increase in the level
of safety by reducing the compliance time in paragraph of (h) of this
AD may be offset by delaying the inspections in paragraph (g) of this
AD. The FAA has determined to delay this action is not appropriate in
this case as the compliance times in this AD will ensure an acceptable
level of safety.

Request To Clarify Compliance Time

Air Wisconsin Airlines asked if the "40 months" specified in MHI
RJ Temporary Revision 2A-76, dated September 29, 2022, is in error. Air
Wisconsin Airlines noted that both paragraphs (g) and (h) of the
proposed AD mention "within 48 months."

The FAA agrees to clarify. As stated previously, MHI RJ Temporary
Revision 2A-76, dated September 29, 2022, was revised by MHI RJ
Temporary Revision 2A-77, dated May 8, 2023, to correct the "40
months" and change it to "48 months." The FAA has not changed this
AD in this regard.

Request To Revise Language in Paragraph (e) of the Proposed AD

MHI RJ requested that the proposed AD should not only mention
missing insulation but damaged insulation as well and stated the
sentence in paragraph (e) of the proposed AD should read: "The FAA is
issuing this AD to address missing or damaged insulation in the engine
pylon area."

The FAA concurs and has revised paragraph (e) of this AD
accordingly. The tasks associated with the new CMR task specifies
inspecting for damaged insulation as well as missing insulation.
Therefore, it is accurate to state that the FAA is issuing this AD to
address both conditions.

Conclusion

This product has been approved by the aviation authority of another
country and is approved for operation in the United States. Pursuant to
the FAA's bilateral agreement with this State of Design Authority, it
has notified the FAA of the unsafe condition described in the MCAI
referenced above. The FAA reviewed the relevant data, considered the
comments received, and determined that air safety requires adopting
this AD as proposed. Accordingly, the FAA is issuing this AD to address
the unsafe condition on this product. Except for minor editorial
changes, and any other changes described previously, this AD is adopted
as proposed in the NPRM. None of the changes will increase the economic
burden on any operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed MHI RJ Service Bulletin 601R-54-006, Revision A,
dated May 24, 2023. This service information specifies procedures for
doing a detailed visual inspection of spar FS654.50, spar FS672.20, and
the firewall for discrepancies, including corrosion, cracks, web
waviness or flatness and damaged fasteners.

The FAA reviewed MHI RJ Temporary Revision 2A-77, dated May 8,
2023. This service information specifies a new CMR task, number C36-12-
133-01, "Detailed Visual Inspection for missing insulation/heat shield
on the 14th stage bleed duct, running through the pylon area between
FS654 and FS672."

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

Estimated Costs for Required Actions *

* This table does not include the cost of revising the existing maintenance or inspection program.

The FAA has determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although the agency recognizes that this number may vary from operator
to operator. Since operators incorporate maintenance or inspection
program changes for their affected fleet(s), the FAA has determined
that a per-operator estimate is more accurate than a per-airplane
estimate. Therefore, the agency estimates the average total cost per
operator to be $7,650 (90 work-hours x $85 per work-hour).

The FAA has received no definitive data on which to base the cost
estimates for the on-condition repairs specified in this 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.

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.

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: