AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Learjet Inc. Model 45 airplanes. This AD was prompted by a report of
two cases of premature corrosion found on the structural support flange
for the engine thrust reverser. This AD requires inspecting for any
corrosion, and damage to the sealant; installing sealants and gaskets;
and related investigative and corrective actions as necessary. We are
issuing this AD to prevent failure of the thrust reverser structural
support, which could result in departure of the thrust reverser from
the engine that could subsequently result in damage to the adjacent
support structure and engine controls, airframe structure, and control
surfaces. Departing thrust reversers could also result in injury to
persons on the ground.

DATES: This AD is effective August 19, 2014.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of August 19,
2014.

ADDRESSES: For service information identified in this AD, contact
Learjet, Inc., One Learjet Way, Wichita, KS 67209-2942; telephone 316-
946-2000; fax 316-946-2220; email ac.ict@aero.bombardier.com; Internet
http://www.bombardier.com. You may view this referenced service
information at the FAA, Transport Airplane Directorate; 1601 Lind
Avenue SW., Renton, WA 98057-3356. For information on the availability
of this material at the FAA, call 425-227-1221.

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-2014-
0010; or in person at the Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this AD, the regulatory evaluation, any comments received, and
other information. The address for the Docket Office (phone: 800-647-
5527) is Docket Management Facility, 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: Paul Chapman, Aerospace Engineer,
Airframe and Services Branch, ACE-118W, FAA, Wichita Aircraft
Certification Office, 1801 Airport Road, Room 100, Mid-Continent
Airport, Wichita, KS 67209; phone: 316-946-4152; fax: 316-946-4107;
email: paul.chapman@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 Learjet Inc. Model
45 airplanes. The NPRM published in the Federal Register on February
10, 2014 (79 FR 7601). The NPRM was prompted by a report of two cases
of premature corrosion found on the structural support flange for the
engine thrust reverser that attaches the thrust reverser to the engine.
The thrust reverser's attach flange is made of aluminum and the
corrosion of that flange can be caused by contact with exposed graphite
fibers from the engine's composite bypass duct. The NPRM proposed to
require doing a fluorescent penetrant inspection of the metallic
components of the thrust reverser's attach flange for any corrosion;
inspecting the thrust reverser flange for damage to the sealant, as
applicable; installing sealants and gaskets, as applicable, to the
thrust reverser flanges and service island flanges; and related
investigative and corrective actions as necessary. We are issuing this
AD to prevent failure of the thrust reverser structural support, which
could result in departure of the thrust reverser from the engine that
could subsequently result in damage to the adjacent support structure
and engine controls, airframe structure, and control surfaces.
Departing thrust reversers could also result in injury to persons on
the ground.

Comments

We gave the public the opportunity to participate in developing
this AD. The following presents the comments received on the proposal
and the FAA's response to each comment.

Request To Add Service Information to Paragraph (i) of This AD

Bombardier requested that paragraph (i) of the proposed AD (79 FR
1601, February 10, 2014) be revised to add Bombardier Service Bulletin
40-78-03, Revision 1, dated November 5, 2012; or Bombardier Service
Bulletin 45-78-9, Revision 1, dated November 5, 2012. Bombardier stated
that adding this service information to paragraph (i) of the proposed
AD would allow credit for accomplishing the requirements of paragraph
(g) of the proposed AD before the effective date of the AD.
We disagree with revising paragraph (i) of this AD. The purpose of
paragraph (i) of this AD is to allow credit for using an earlier
revision of the required service information before the effective date
of the AD if that earlier revision is considered acceptable for
addressing the unsafe condition. If actions required by paragraph (g)
of this AD were accomplished before the effective date of the AD, using
the service information required by paragraph (g) of this AD, those
actions are considered acceptable for compliance, since paragraph (f)
of this AD states ``Comply with this AD within the compliance times
specified, unless already done.'' We have not changed this AD in this
regard.

Clarification of Marketing Designation

We have revised Note 1 to paragraph (c) of this AD to clarify the
marketing designations that Model 45 airplanes might be known as.

Conclusion

We reviewed the relevant data, considered the comment received, and
determined that air safety and the public interest require adopting
this AD as proposed except for minor editorial changes. We have
determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM (79 FR 1601, February 10, 2014) for correcting the unsafe
condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM (79 FR 1601, February 10, 2014).

Costs of Compliance

We estimate that this AD affects 365 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated Costs

We estimate the following costs to do any necessary replacements
that would be required based on the results of the inspection. We have
no way of determining the number of aircraft that might need this
replacement.

On-Condition Costs

According to the manufacturer, some of the costs of this AD may be
covered under warranty, thereby reducing the cost impact on affected
individuals. We do not control warranty coverage for affected
individuals. As a result, we have included all costs in our cost
estimate.

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.

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 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):