Document ID: FAA-2021-0157-0001
Agency: faa
Document Type: Proposed Rule
Title: Airworthiness Directives: Learjet Inc.
Posted Date: 2021-07-28T04:00Z

[Federal Register Volume 86, Number 142 (Wednesday, July 28, 2021)]
[Proposed Rules]
[Pages 40379-40381]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15953]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0157; Project Identifier AD-2020-00483-T]
RIN 2120-AA64

Airworthiness Directives; Learjet Inc.

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Learjet Inc. (Learjet) Model 45 airplanes. This proposed AD 
was prompted by reports of corrosion found on the upper surface of the 
lower center wing mid spar splice plate. This proposed AD would require 
repetitively inspecting the center wing area for corrosion and 
deterioration of protective treatments, removing any corrosion, and 
treating any deteriorated areas. The FAA is proposing this AD to 
address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by September 
13, 2021.

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 https://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; phone: (316) 946-2000; email: 
ac.ict@aero.bombardier.com; website: https://
businessaircraft.bombardier.com/en/aircraft/Learjet.html. You may view 
this referenced 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.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0157; 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, any comments 
received, and other information. The street address for Docket 
Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Tara Shawn, Aviation Safety Engineer, 
Wichita ACO Branch, FAA, 1801 Airport Road, Wichita, KS 67209; phone: 
(316) 946-4141; fax: (316) 946-4107; email: tara.shawn@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2021-0157; Project Identifier 
AD-2020-00483-T'' at the beginning of your comments. The most helpful 
comments reference a specific portion of the proposal, explain the 
reason for any recommended change, and include supporting data. The FAA 
will consider all comments received by the closing date and may amend 
this proposal because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
https://www.regulations.gov, including any personal information you 
provide. The agency will also post a report summarizing each 
substantive verbal contact received about this NPRM.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this NPRM contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this NPRM, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this NPRM. Submissions containing CBI should be sent to Tara 
Shawn, Aviation Safety Engineer, Wichita ACO Branch, FAA, 1801 Airport 
Road, Wichita, KS 67209. Any commentary that the FAA receives which is 
not specifically designated as CBI will be placed in the public docket 
for this rulemaking.

Background

    In December 2018, the FAA received a report from Learjet of 
corrosion found in the center wing area of a Model 45 (Learjet 45) 
airplane. Exfoliating corrosion was found on the upper surface of the 
lower center wing mid spar splice plate during unrelated maintenance. 
The corrosion appeared to extend half way through the thickness of the 
splice plate. Since the initial report, the FAA has received 23 
additional reports of corrosion from Learjet. The FAA determined areas 
of the wing center section are not sealed against the elements; in 
addition, the fuselage has drain holes that allow condensation to drain 
into the center wing. The accumulation and retention of moisture in the 
center wing section may lead to corrosion. This condition, if not 
addressed, could result in failure of the wing centerline joint and 
lead to partial wing separation with consequent loss of control of the 
airplane.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or

[[Page 40380]]

develop on other products of the same type design.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed the following service documents proposed for 
compliance with this NPRM:
     Bombardier Learjet 40 Service Bulletin 40-57-06, Revision 
1, dated October, 26, 2020;
     Bombardier Learjet 45 Service Bulletin 45-57-13, Revision 
1, dated October, 26, 2020;
     Bombardier Learjet 70 Service Bulletin 70-57-02, Revision 
1, dated October, 26, 2020; and
     Bombardier Learjet 75 Service Bulletin 75-57-01, Revision 
2, dated April 19, 2021.
    As applicable to the model configuration specified, each service 
bulletin contains procedures for inspecting for corrosion and 
deterioration of protective treatments of the center wing area from the 
front spar to the rear spar between wing stations 33.00L to 33.00R, 
treating deteriorated areas, and removing any corrosion. Bombardier 
Learjet 75 Service Bulletin 75-57-01, Revision 2, dated April 19, 2021, 
does not apply to newly- manufactured airplanes, since Learjet added 
this inspection to the Airworthiness Limitation Section, which will be 
delivered with new airplanes starting at S/N 45-597.
    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.

Proposed AD Requirements in This NPRM

    This proposed AD would require accomplishing the actions specified 
in the service information already described. This proposed AD would 
also require reporting the inspection results to the FAA by email at 
Wichita-COS@faa.gov.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 450 airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this proposed 
AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
              Action                      Labor cost              Parts cost          product        operators
----------------------------------------------------------------------------------------------------------------
Inspection.......................  7.50 work-hours x $85     Not applicable.....         $637.50        $286,875
                                    per hour = $637.50.
Reporting to FAA.................  1 work-hour x $85 per     Not applicable.....              85          38,250
                                    hour = $85.
----------------------------------------------------------------------------------------------------------------

    The extent of corrosion and deterioration of protective treatments 
may vary significantly from airplane to airplane. The FAA has no way of 
determining how much damage may be found on each airplane, the cost to 
remove the corrosion or treat deteriorated areas (or replacing the 
part, if needed), or the number of airplanes that may require repair.
    If corrosion is found and removed, the FAA estimates that it would 
take 2 work-hours per airplane to provide data to Learjet. With an 
average labor rate of $85 per work-hour, the FAA estimates a cost of 
$170 per airplane.

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 current 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 up to 
3 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

    The FAA 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 this proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and
    (3) Would 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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

[[Page 40381]]

Learjet Inc.: Docket No. FAA-2021-0157; Project Identifier AD-2020-
00483-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by September 13, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Learjet Inc. Model 45 (Learjet 40), Model 45 
(Learjet 45), Model 45 (Learjet 70), and Model 45 (Learjet 75) 
airplanes, serial numbers 45-002 through 45-596 and 45-2001 through 
45-2146, certificated in any category.

(d) Subject

    Joint Aircraft System Component (JASC) Code 5714, Wing, Center 
Box.

(e) Unsafe Condition

    This AD was prompted by reports of corrosion found on the upper 
surface of the lower center wing mid spar splice plate. The FAA is 
issuing this AD to detect and correct corrosion or deterioration of 
protective treatments on the center wing area. The unsafe condition, 
if not addressed, could result in failure of the wing centerline 
joint and lead to partial wing separation with consequent loss of 
control of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Applicable Service Bulletins

    Use the following service bulletins, as applicable to your 
airplane model configuration, to perform the actions required by 
paragraph (h) of this AD:
    (1) Bombardier Learjet 40 Service Bulletin 40-57-06, Revision 1, 
dated October 26, 2020;
    (2) Bombardier Learjet 45 Service Bulletin 45-57-13, Revision 1, 
dated October 26, 2020;
    (3) Bombardier Learjet 70 Service Bulletin 70-57-02, Revision 1, 
dated October 26, 2020; and
    (4) Bombardier Learjet 75 Service Bulletin 75-57-01, Revision 2, 
dated April 19, 2021.

(h) Wing Center Spar Inspection, Related Investigative Inspections, and 
Corrective Actions

    At the applicable initial compliance time specified in paragraph 
(h)(1) or (2) of this AD and thereafter at intervals not to exceed 8 
years, inspect the center wing area for corrosion and deterioration 
of protective treatments and perform all related corrective actions 
by following the Accomplishment Instructions, steps 3.A. and 3.B., 
of the applicable service bulletin listed in paragraph (g) of this 
AD.
    (1) For airplanes with 8 or fewer years since the date of 
issuance of the original airworthiness certificate or the date of 
issuance of the original export certificate of airworthiness, 
whichever date is earlier: Before or upon accumulating 8 years or 
within 12 months after the effective date of this AD, whichever 
occurs later; or
    (2) For airplanes that have accumulated more than 8 years since 
the date of issuance of the original airworthiness certificate or 
the date of issuance of the original export certificate of 
airworthiness, whichever date is earlier: Within 12 months after the 
effective date of this AD.

(i) Service Information Exception

    Where Bombardier Learjet 40 Service Bulletin 40-57-06, Revision 
1, dated October 26, 2020, Bombardier Learjet 45 Service Bulletin 
45-57-13, Revision 1, dated October 26, 2020, Bombardier Learjet 70 
Service Bulletin 70-57-02, Revision 1, dated October 26, 2020, and 
Bombardier Learjet 75 Service Bulletin 75-57-01, Revision 2, dated 
April 19, 2021, specify contacting Learjet Inc. for appropriate 
action: Before further flight, repair using a method approved in 
accordance with the procedures specified in paragraph (l) of this 
AD.

(j) Reporting Requirement

    Within 30 days after completing the initial inspection required 
by paragraph (h) of this AD or within 30 days after the effective 
date of this AD, whichever occurs later, submit a report of the 
findings (both positive and negative) of the inspection to: Wichita-COS@faa.gov; or Ann Johnson, Wichita ACO Branch, 1801 Airport Road, 
Wichita, KS 67209. This reporting requirement is limited to the 
initial inspection results only. The report must include: The name 
of the owner; the address of the owner; the name of the organization 
doing the actions required by this AD; the date the inspection was 
completed; the name of the person submitting the report; the 
address, telephone number, and email of the person submitting the 
report; the airplane serial number; the date of issuance of the 
original airworthiness certificate, or the date of issuance of the 
original export certificate of airworthiness (whichever date is 
earlier); whether protective treatments are deteriorated, and if so, 
the location of deteriorated areas; whether corrosion was detected, 
and if so, the location of corrosion; and a list of parts replaced 
if the level of corrosion required replacement of parts.

(k) Credit for Previous Actions

    You may take credit for the initial wing spar inspection 
required by the introductory text to paragraph (h) of this AD if you 
performed the visual inspection before the effective date of this AD 
using Bombardier Learjet 40 Service Bulletin 40-57-06, Basic Issue, 
dated February 25, 2019; Bombardier Learjet 45 Service Bulletin 45-
57-13, Basic Issue, dated February 25, 2019; Bombardier Learjet 70 
Service Bulletin 70-57-02, Basic Issue, dated February 25, 2019; 
Bombardier Learjet 75 Service Bulletin 75-57-01, Basic Issue, dated 
February 25, 2019; or Bombardier Learjet 75 Service Bulletin 75-57-
01, Revision 1, dated October 26, 2020.
    (1) To take credit for the initial inspection, you must comply 
with paragraph (j) of this AD within 30 days after the effective 
date of this AD.
    (2) You cannot take credit for the recurring inspections, only 
the initial inspection.

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Wichita ACO Branch, FAA, has the authority to 
approve AMOCs for this AD, if requested using the procedures found 
in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request 
to your principal inspector or local Flight Standards District 
Office, as appropriate. If sending information directly to the 
manager of the certification office, send it to the attention of the 
person identified in Related Information.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration required by this AD 
if it is approved by a Learjet Inc. Designated Engineering 
Representative, or a Unit Member of the Learjet Organization 
Designation Authorization, that has been authorized by the Manager, 
Wichita ACO Branch, to make those findings. To be approved, the 
repair, modification, or alteration method must meet the 
certification basis of the airplane, and the approval must 
specifically refer to this AD.

(m) Related Information

    (1) For more information about this AD, contact Tara Shawn, 
Aviation Safety Engineer, Wichita ACO Branch, FAA, 1801 Airport 
Road, Wichita, KS 67209; phone: (316) 946-4141; fax: (316) 946-4107; 
email: tara.shawn@faa.gov.
    (2) For service information identified in this AD, contact 
Learjet Inc., One Learjet Way, Wichita, KS 67209; phone: (316) 946-
2000; email: ac.ict@aero.bombardier.com; website: 
businessaircraft.bombardier.com/en/aircraft/Learjet.html. You may 
view this referenced 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.

    Issued on July 21, 2021.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-15953 Filed 7-27-21; 8:45 am]
BILLING CODE 4910-13-P