DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0327; Product Identifier 2018-CE-001-AD; Amendment
39-19404; AD 2018-19-04]
RIN 2120-AA64

Airworthiness Directives; Learjet, Inc. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Learjet, Inc. Models 28, 29, 31, 31A, 35, 35A, 36, 36A, 55, 55B, 55C,
and 60 airplanes. This AD was prompted by fatigue cracks initiating in
the flap support structure due to repetitive flap loads, which has
caused flap nose roller support bracket failure. This AD requires
replacement of the flap nose roller fitting, nose roller support
bracket, and adjacent rib support structure with improved components.
We are issuing this AD to address the unsafe condition on these
products.

DATES: This AD is effective October 23, 2018.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of October 23,
2018.

ADDRESSES: For service information identified in this final rule,
contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209;
telephone: 316-946-2000; email: ac.ict@aero.bombardier.com; internet:
https://www.bombardier.com. You may view this service information at
the FAA, Policy and Innovation Division, 901 Locust, Kansas City,
Missouri 64106. For information on the availability of this material at
the FAA, call (816) 329-4148. It is also available on the internet at
http://www.regulations.gov by searching for and locating Docket No.
FAA-2018-0327.

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-
0327; 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 Docket Operations, 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: Tara Shawn, Aerospace Engineer,
Wichita ACO Branch, 1801 Airport Road, Room 100, Wichita, Kansas 67209;
telephone: (316) 946-4141; fax: (316) 946-4107; email:
tara.shawn@faa.gov or Wichita-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 Learjet, Inc.
Models 28, 29, 31, 31A, 35, 35A, 36, 36A, 55, 55B, 55C, and 60
airplanes. The NPRM published in the Federal Register on May 8, 2018
(83 FR 20740). The NPRM was prompted by a report that a skewed flap and
aileron became bound on a Model 31A airplane, which was later found to
have fatigue cracks in the flap support structure due to repetitive
flap loads. Fatigue cracks in the flap support structure caused by
repetitive flap loads can result in failure of the flap nose roller
support bracket. Repetitive flap loads occur on all models identified
by this AD. The NPRM proposed to require replacement of the flap nose
roller fitting, nose roller support bracket, and adjacent rib support
structure with improved components. This condition, if not addressed,
could result in loss of roll control on approach with consequent loss
of control of the airplane. We are issuing this AD to address the
unsafe condition on these products.

Comments

We gave the public the opportunity to participate in developing
this final rule. We received no comments on the NPRM or on the
determination of the cost to the public.

Clarification of Repair Method

We have revised this action to clarify that operators are not
required to obtain repair instructions from Learjet. Instead, operators
must use a repair method approved by the Manager, Wichita ACO Branch,
FAA.

Conclusion

We reviewed the relevant data and determined that air safety and
the public interest require adopting this final rule as proposed except
for the changes described previously and other minor editorial changes.
We have determined that these 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

We reviewed Bombardier Learjet 28/29 Service Bulletin SB 28/29-27-
31 Recommended, dated September 11, 2017; Bombardier Learjet 31 SB 31-
27-35 Recommended, dated September 11, 2017; Bombardier Learjet 35/36
SB 35/36-27-50 Recommended, dated September 11, 2017; Bombardier
Learjet 55 SB 55-27-41 Recommended, dated September 11, 2017; and
Bombardier Learjet 60 SB 60-27-39 Recommended, Revision 1, dated
January 15, 2018. For the applicable models, the service information
describes procedures for replacement of the flap nose roller fitting,
nose roller support bracket, and adjacent rib support structure with
improved components. The service information also contains instructions
to ensure correct flap alignment. 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 706 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated Costs

* Parts cost is an average of the combined costs for replacement of all
of the kits per airplane. Not all airplanes will need all kits, as credit is allowed
for some previous installations.

Individual Parts Cost *

* Parts required for replacement may vary for different models and
different airplanes.

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 small airplanes, gliders,
balloons, airships, domestic business jet transport airplanes, and
associated appliances to the Director of the Policy and Innovation 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 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):