[Federal Register Volume 71, Number 122 (Monday, June 26, 2006)]
[Proposed Rules]
[Pages 36255-36257]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-10004]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-25174; Directorate Identifier 2005-NM-007-AD]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 45 Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (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 Model 45 airplanes. This proposed AD would require 
revising the Airworthiness Limitations section of the airplane 
maintenance manual to incorporate certain inspections and compliance 
times to detect fatigue cracking of certain principal structural 
elements (PSEs). This proposed AD results from new and more restrictive 
life limits and inspection intervals for certain PSEs. We are proposing 
this AD to ensure that fatigue cracking of various PSEs is detected and 
corrected; such fatigue cracking could adversely affect the structural 
integrity of these airplanes.

DATES: We must receive comments on this proposed AD by August 10, 2006.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, 
for the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT: Steve Litke, Aerospace Engineer, 
Airframe Branch, ACE-118W, FAA, Wichita Aircraft Certification Office, 
1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 
67209; telephone (316) 946-4127; fax (316) 946-4107.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2006-
25174; Directorate Identifier 2005-NM-007-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that Web site, anyone can find and read the comments in any of our 
dockets, including the name of the individual who sent the comment (or 
signed the comment on behalf of an association, business, labor union, 
etc.). You may review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management

[[Page 36256]]

Facility office between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The Docket Management Facility office 
(telephone (800) 647-5227) is located on the plaza level of the Nassif 
Building at the DOT street address stated in the ADDRESSES section. 
Comments will be available in the AD docket shortly after the Docket 
Management System receives them.

Discussion

    As service experience is accumulated on airplanes or as the result 
of post-certification testing and evaluation, it may become necessary 
to revise removal limits for removal of certain life-limited components 
of the airplane or revise the interval for certain structural 
inspections in order to ensure the continued structural integrity of 
the airplane. The manufacturer may revise the Airworthiness Limitations 
document to include more restrictive life limits or revise repetitive 
intervals for certain non-destructive inspection (NDI) techniques and 
procedures for each principal structural element (PSE). For the 
purposes of this airworthiness directive, a PSE is defined as an 
element of structure that contributes significantly to carrying flight, 
ground, and pressurization loads. If a failure occurs on any of those 
PSEs, it could adversely affect the structural integrity of the 
airplane.
    The actions specified by the proposed AD are intended to ensure 
that fatigue cracking of various PSEs is detected and corrected; such 
fatigue cracking could adversely affect the structural integrity of 
these airplanes.

New Revisions of Airworthiness Limitations Sections (ALS)

    We have reviewed Chapter 4, ``Airworthiness Limitations,'' of the 
Learjet 40 Maintenance Manual (MM), Revision 6, dated April 24, 2006; 
and Chapter 4, ``Airworthiness Limitations,'' of the Learjet 45 MM, 
Revision 38, dated April 24, 2006. These MM chapters add new and more 
restrictive life limits and inspection intervals for certain PSEs. PSEs 
include, but are not limited to, door cutouts, windshields, skin 
sections, bolts, and attachment hardware. The MM chapters explicitly 
identify all of the PSEs that are to be inspected in accordance with 
the requirements of the Airworthiness Limitations section (ALS). 
Accomplishing the actions specified in these chapters is intended to 
adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require revising the ALS of the MM to incorporate certain 
inspections and compliance times to detect fatigue cracking of certain 
PSEs.

Clarification of Model Designations

    Certain Learjet Model 45 airplanes are also referred to as Model 45 
(Learjet 40) airplanes. Model 45 (Learjet 40) airplanes have serial 
numbers (S/Ns) 45-2001 through 45-4000 inclusive. The remainder of the 
Learjet Model 45 airplanes are referred to as Model 45 (Learjet 45) 
airplanes, and have S/Ns 45-002 through 45-2000 inclusive.

Costs of Compliance

    There are about 230 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 171 airplanes of 
U.S. registry. The proposed actions would take about 1 work hour per 
airplane, at an average labor rate of $80 per work hour. Based on these 
figures, the estimated cost of the proposed AD for U.S. operators is 
$13,680, or $80 per airplane.

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

    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); 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket. See the 
ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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 Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

Learjet: Docket No. FAA-2006-25174; Directorate Identifier 2005-NM-
007-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by August 
10, 2006.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Learjet Model 45 airplanes, certificated 
in any category; serial numbers (S/Ns) 45-002 through 45-233 
inclusive, and S/Ns 45-2001 through 45-2031 inclusive.

Unsafe Condition

    (d) This AD results from new and more restrictive life limits 
and inspection intervals for certain principal structural elements 
(PSEs). We are issuing this AD to ensure that fatigue cracking of 
various PSEs is detected and corrected; such fatigue cracking could 
adversely affect the structural integrity of these airplanes.

[[Page 36257]]

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

    Note 1: This AD requires revisions to certain operator 
maintenance documents to include new inspections. Compliance with 
these inspections is required by 14 CFR 91.403(c). For airplanes 
that have been previously modified, altered, or repaired in the 
areas addressed by these inspections, the operator may not be able 
to accomplish the inspections described in the revisions. In this 
situation, to comply with 14 CFR 91.403(c), the operator must 
request approval for an alternative method of compliance (AMOC) 
according to paragraph (g) of this AD. The request should include a 
description of changes to the required inspections that will ensure 
the continued damage tolerance of the affected structure. The FAA 
has provided guidance for this determination in Advisory Circular 
(AC) 25-1529.

Revise the Airworthiness Limitations Section (ALS)

    (f) Within 30 days after the effective date of this AD, revise 
the ALS of the airplane maintenance manual (AMM) to include new life 
limits and inspection intervals according to a method approved by 
the Manager, Wichita Aircraft Certification Office (ACO), FAA. 
Incorporating the applicable chapters in paragraph (f)(1) or (f)(2) 
of this AD in the AMM is one approved method for doing the revision. 
Thereafter, except as provided in paragraph (g) of this AD, no 
alternative life limits or inspection intervals may be approved for 
the affected PSEs.
    (1) For Learjet Model 45 airplanes, S/Ns 45-002 through 45-233 
inclusive: Chapter 4 of the Learjet 45 Maintenance Manual, Revision 
38, dated April 24, 2006.
    (2) For Learjet Model 45 airplanes, S/Ns 45-2001 through 45-2031 
inclusive: Chapter 4 of the Learjet 40 Maintenance Manual, Revision 
6, dated April 24, 2006.

AMOCs

    (g)(1) The Manager, Wichita ACO, FAA, has the authority to 
approve AMOCs for this AD, if requested in accordance with the 
procedures found in 14 CFR 39.19.
    (2) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.

    Issued in Renton, Washington, on June 14, 2006.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E6-10004 Filed 6-23-06; 8:45 am]
BILLING CODE 4910-13-P