DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0660; Project Identifier AD-2021-00398-T;
Amendment 39-21809; AD 2021-23-11]
RIN 2120-AA64

Airworthiness Directives; Learjet 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
certain Learjet Inc. Model 45 airplanes. This AD was prompted by a
report of a fuel leak due to a cracked fuel line between the engine
fuel control and the engine fuel flow meter. This AD requires replacing
the existing fuel flow meter bracket assembly with a redesigned bracket
assembly and reporting information to the FAA. The FAA is issuing this
AD to address the unsafe condition on these products.

DATES: This AD is effective January 10, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of January 10,
2022.

ADDRESSES: For service information identified in this final rule,
contact Learjet Inc., One Learjet Way, Wichita, KS 67209; phone: (316)
946-2000; email: ac.ict@aero.bombardier.com; website: https://businessaircraft.bombardier.com/en/aircraft/Learjet.html. You may view
this service information at the FAA, Airworthiness Products Section,
Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For
information on the availability of this material at the FAA, call (816)
329-4148. It is also available at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0660.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0660; 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, 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.

FOR FURTHER INFORMATION CONTACT: Thomas Teplik, Aviation Safety
Engineer, Wichita ACO Branch, FAA, 1801 S. Airport Road, Wichita, KS
67209; phone: (316) 946-4196; email: thomas.teplik@faa.gov or Wichita-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 certain serial numbered
Learjet Inc. Model 45 (Learjet 40), Model 45 (Learjet 45), Model 45
(Learjet 70), and Model 45 (Learjet 75) airplanes. The NPRM published
in the Federal Register on August 13, 2021 (86 FR 44660). The NPRM was
prompted by a report of a fuel leak due to a cracked fuel line between
the engine fuel control and the engine fuel flow meter on a Model 45
(Learjet 45) airplane. Further analysis of the fleet of all the 45
models revealed similar failures in this area including the following:
16 fuel line failures, 2 instances of multiple inlet attaching bolts
breaking, 9 leaking fuel controls, a broken gearbox strut, 4 cracked
No. 6 bearing oil supply lines, and 7 cracked engine oil tanks. The FAA
evaluated the flammable fluid leaks and broken parts and determined
that they may have resulted from vibration. In the NPRM, the FAA
proposed to require replacing the existing fuel flow meter bracket
assembly with a redesigned bracket assembly and reporting information
to the FAA. The FAA is issuing this AD to address the unsafe condition
on these products.

Discussion of Final Airworthiness Directive

Comments

The FAA received no comments on the NPRM or on the determination of
the costs.

Conclusion

The FAA reviewed the relevant data and determined that air safety
requires adopting this AD as proposed. Accordingly, the FAA is issuing
this AD to address the unsafe condition on these products. This AD is
adopted as proposed in the NPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed the following service documents required for
compliance with this AD:
Bombardier Learjet 40 Service Bulletin (SB) SB 40-73-01,
Revision 1;
Bombardier Learjet 45 SB 45-73-2, Revision 1;
Bombardier Learjet 70 SB 70-73-01, Revision 1; and
Bombardier Learjet 75 SB 75-73-01, Revision 2; all
documents dated January 9, 2017.
As applicable to the model configuration specified, each service
bulletin contains procedures for replacing the existing fuel flow meter
bracket assembly with a redesigned fuel flow meter bracket assembly
that has an increased material thickness. 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
ADDRESSES.

Differences Between This AD and the Service Information

This AD requires reporting certain maintenance information to the
FAA, where the service information does not. The information provided
in the reports is related to contributing factors that the FAA found
showed a correlation between the reported engine fan vibration levels
and the cracking fuel line between engine fuel control and the engine
fuel flow meter and a correlation between the cracking fuel line and a
certain batch of fan disks. In addition, the FAA found that a
contributing factor could be the susceptibility of the fuel flow meter
bracket assembly to the engine installation vibration. The requested
reporting information allows the FAA to determine whether further
rulemaking action is necessary to mitigate the unsafe condition.
Also, the effectivity of Bombardier Learjet 45 SB 45-73-2, Revision
1, dated January 9, 2017, begins with serial number 45-005. This AD
also applies to airplane serial numbers 45-002 through 45-004 because,
although these three airplanes are not currently in service, they are
subject to the unsafe condition. Thus, it is necessary to include them
in the event they are returned to service.

Costs of Compliance

The FAA estimates that this AD affects 443 airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this AD:

Estimated Costs

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 take
approximately 9 hours per response, including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, and 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.
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: