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Federal Register / Vol. 86, No. 231 / Monday, December 6, 2021 / Rules and Regulations
Federal Aviation Administration
30, West Building Ground Floor, Room W12140, 1200 New Jersey Avenue SE, Washington, DC 20590.

14 CFR Part 39

FOR FURTHER INFORMATION CONTACT:

DEPARTMENT OF TRANSPORTATION

Docket No. FAA20210660; Project Identifier AD202100398T; Amendment 3921809; AD 20212311
RIN 2120AA64

Airworthiness Directives; Learjet Inc.
Airplanes
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.

SUMMARY:

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 9462000;
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 3294148. It is also available at https www.regulations.gov by searching for and locating Docket No.
FAA20210660.
DATES:

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Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210660; 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

15:44 Dec 03, 2021

SUPPLEMENTARY INFORMATION:

Background
Federal Aviation Administration FAA, DOT.
ACTION: Final rule.
AGENCY:

VerDate Sep<11>2014

Thomas Teplik, Aviation Safety Engineer, Wichita ACO Branch, FAA, 1801 S. Airport Road, Wichita, KS
67209; phone: 316 9464196; email:
thomas.teplik@faa.gov or Wichita-COS@
faa.gov.

Jkt 256001

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.

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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 407301, Revision 1;
Bombardier Learjet 45 SB 45732, Revision 1;
Bombardier Learjet 70 SB 7073
01, Revision 1; and Bombardier Learjet 75 SB 7573
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 45732, Revision 1, dated January 9, 2017, begins with serial number 45005. This AD also applies to airplane serial numbers 45002 through 45004 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:

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