DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0046; Product Identifier 2018-CE-040-AD]
RIN 2120-AA64

Airworthiness Directives; Learjet, Inc. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede Airworthiness Directive (AD) 2017-11-
09, which applies to certain Learjet, Inc. (Learjet), Model 60
airplanes. AD 2017-11-09 requires a one-time inspection of the fuselage
skin for corrosion and, as necessary, additional related inspections
and corrective actions. Since we issued AD 2017-11-09, we identified an
error in the fluorescent dye penetrant inspection of the fuselage skin
and an ambiguity in the compliance time for the fluorescent dye
penetrant inspection. We are proposing this AD to clarify the
compliance time and correct an error for the fluorescent dye penetrant
inspection of the fuselage skin.

DATES: We must receive comments on this proposed AD by March 25, 2019.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:

Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the
instructions for submitting comments.

Fax: 202-493-2251.

Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.

Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, 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 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.

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-2019-
0046; 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 NPRM, the regulatory evaluation, any comments received, and other
information. The street address for Docket Operations (phone: 800-647-
5527) is listed above. Comments will be available in the AD docket
shortly after receipt.

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:

Comments Invited

We invite you to send any written relevant data, views, or
arguments about this proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include "Docket No. FAA-2019-0046;
Product Identifier 2018-CE-040-AD" at the beginning of your comments.
We specifically invite comments on the overall regulatory, economic,
environmental, and energy aspects of this NPRM. We will consider all
comments received by the closing date and may amend this NPRM because
of those comments.

We will post all comments we receive, without change, to http://www.
regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this proposed AD.

Discussion

We issued AD 2017-08-07, Amendment 39-18856 (82 FR 18084, April 17,
2017) ("2017-08-07") for certain serial-numbered Learjet Model 60
airplanes. AD 2017-08-07 required a one-time inspection of the fuselage
skin for corrosion and, as necessary, additional related inspections
and corrective actions. AD 2017-08-07 resulted from an evaluation by
the design approval holder that indicated the upper fuselage skin under
the aft oxygen line fairing is subject to multi-site damage. We issued
AD 2017-08-07 to detect and correct corrosion of the fuselage skin,
which could result in reduced structural integrity of the airplane.

After we issued AD 2017-08-07, we determined that only certain
airplanes listed in the applicability of AD 2017-08-07 are affected by
the unsafe condition. Therefore, we issued AD 2017-11-09, Amendment 39-
18908 (82 FR 24462, May 30, 2017) ("AD 2017-11-09") to supersede AD
2017-08-07. AD 2017-11-09 retained all of the actions of AD 2017-08-07
but revised the applicability to identify only airplanes with a dorsal-
mounted oxygen bottle and airplanes that have had the dorsal-mounted
oxygen bottle removed but have retained the oxygen line fairing
installed on top of the fuselage.

Actions Since AD 2017-11-09 Was Issued

Since we issued AD 2017-11-09, we identified an error in the area
of the fluorescent dye penetrant inspection requirement. AD 2017-11-09
requires the fluorescent penetrant inspection of the fuselage skin
between stringers (S)-2L and S-2R. Bombardier Learjet 60 Service
Bulletin (SB) 60-53-19, Recommended, Revision 3, dated August 29, 2016,
specifies inspecting a smaller area, only out to the fairing end caps.

We also identified an ambiguity in the compliance time for the
inspection of the fuselage skin. Paragraphs (g)(1) through (3) of AD
2017-11-09 do not specify that the date of issuance of the original
airworthiness certificate or the date of issuance of the original
export certificate of airworthiness should be whichever date is
earlier.

We are proposing this AD to correct the error of the inspection
area and clarify the compliance times for the fluorescent dye penetrant
inspection of the fuselage skin. This proposed AD will detect and
correct corrosion of the fuselage skin, which could result in reduced
structural integrity of the airplane.

Related Service Information Under 1 CFR Part 51

We reviewed Bombardier Learjet 60 Service Bulletin (SB) 60-53-19,
Revision 3, dated August 29, 2016. This service information was
previously approved for incorporation by reference in AD 2017-08-07 and
AD 2017-11-09 retained the incorporation by reference of this SB. The
service information describes procedures for inspections of the
fuselage crown skin for corrosion and, as necessary, related
investigative inspections and corrective actions. 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.

FAA's Determination

We are proposing this AD because we evaluated all the relevant
information and determined the unsafe condition described previously is
likely to exist or develop in other products of the same type design.

Proposed AD Requirements

This proposed AD would retain all requirements of AD 2017-11-09.
However, we removed the language in paragraph (g) that identified the
area of the fuselage skin to be inspected as "between stringers (S)-2L
and S-2R." Both this proposed AD and AD 2017-11-09 require following
the instructions in Bombardier Learjet 60, Service Bulletin SB 60-53-
19, Revision 3, dated August 29, 2016, which requires inspection of a
smaller area (only out to the fairing end caps).

Costs of Compliance

We estimate that this proposed AD affects 284 airplanes of U.S.
registry.

We estimate the following costs to comply with this proposed AD:

Estimated Costs

This AD adds no additional economic burden. 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 known 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 a 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 currently valid OMB Control Number. The OMB
Control Number for this information collection is 2120-0056. Public
reporting for this collection of information is estimated to be
approximately 1 hour per response, including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, completing and reviewing the collection of
information. All responses to this collection of information are
mandatory. Send comments regarding this burden estimate or any other
aspect of this collection of information, including suggestions for
reducing this burden to: Information Collection Clearance Officer,
Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX
76177-1524.

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

We have determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 the proposed
regulation:
(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.

The Proposed Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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 removing Airworthiness Directive (AD)
2017-11-09, Amendment 39-18908 (82 FR 24462, May 30, 2017) and adding
the following new AD: