DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-9505; Directorate Identifier 2016-NM-155-AD;
Amendment 39-18856; AD 2017-08-07]
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., Model 60 airplanes. This AD was prompted by an
evaluation by the design approval holder (DAH) indicating that the
upper fuselage skin under the aft oxygen line fairing is subject to
multi-site damage (MSD). This AD requires a one-time inspection of the
fuselage skin for corrosion, and related investigative and corrective
actions if necessary. We are issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective May 22, 2017.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of May 22,
2017.

ADDRESSES: For service information identified in this final rule,
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. For information
on the availability of this material at the FAA, call 425-227-1221. It
is also available on the Internet at http://www.regulations.gov by
searching for and locating Docket No. FAA-2016-9505.

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-2016-
9505; 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 Branch, ACE-118W, FAA, Wichita Aircraft Certification Office
(ACO), 1801 Airport Road, Room 100, Dwight D. Eisenhower Airport,
Wichita, KS 67209; phone: 316-946-4152; fax: 316-946-4107; email:
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.,
Model 60 airplanes. The NPRM published in the Federal Register on
December 20, 2016 (81 FR 92745) (``the NPRM''). The NPRM was prompted
by an evaluation by the DAH indicating that the upper fuselage skin
under the aft oxygen line fairing is subject to MSD. The NPRM proposed
to require a one-time inspection of the fuselage skin for corrosion,
and related investigative and corrective actions if necessary. We are
issuing this AD to detect and correct corrosion of the fuselage skin,
which could result in reduced structural integrity of the airplane.

Comments

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

Request To Require Repetitive Inspections

An anonymous commenter stated that given the cause is unknown, a
one-time inspection is insufficient to protect against corrosion. The
commenter stated that we should require more frequent inspections.
We partially agree with the commenter. We understand the concern
that repetitive inspections might be necessary to reduce the damage
caused by corrosion. However, the required inspection is considered to
be interim action, and in order to establish meaningful inspection
intervals without causing excessive expense to operators, this AD
requires owners/operators to report the extent of corrosion on their
airplanes along with the total time (i.e., flight hours) and total
number of landings on the airplanes. Using this information, the FAA
will be able to gain a better understanding of the damage to the fleet.
This will allow us to determine if additional corrective action is
needed and what the appropriate action should be. It also will provide
justification as to whether or not further rulemaking is needed. We
have not changed this AD in this regard.

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 for correcting 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 Learjet 60 Service Bulletin 60-53-19, Revision 3, dated
August 29, 2016. The service information describes procedures for
inspections of the fuselage crown skin for corrosion, and related
investigative and corrective actions if necessary. 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.

Interim Action

We consider this AD interim action. Because the cause of the
corrosion is not known, the inspection reports will help determine the
extent of the corrosion in the affected fleet. Based on the results of
these reports, we might determine that further corrective action is
warranted. Once further corrective action has been identified, we might
consider further rulemaking.

Costs of Compliance

We estimate that this AD affects 284 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 on-condition actions specified in this AD.
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.

Paperwork Reduction Act

A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a current valid OMB control number. The control
number for the collection of information required by this AD is 2120-
0056. The paperwork cost associated with this AD has been detailed in
the Costs of Compliance section of this document and includes time for
reviewing instructions, as well as completing and reviewing the
collection of information. Therefore, all reporting associated with
this AD is mandatory. Comments concerning the accuracy of this burden
and suggestions for reducing the burden should be directed to the FAA
at 800 Independence Ave. SW., Washington, DC 20591, ATTN: Information
Collection Clearance Officer, AES-200.

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):