[Federal Register Volume 68, Number 155 (Tuesday, August 12, 2003)]
[Rules and Regulations]
[Pages 47842-47844]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-20238]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2003-NM-141-AD; Amendment 39-13262; AD 2003-16-09]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 45 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Learjet Model 45 airplanes. This action 
incorporates a reduced life-limit replacement interval for certain 
shear pins in the trunnion assemblies of the main landing gears (MLG) 
into the airworthiness limitations section of the Instructions for 
Continued Airworthiness, and requires replacement of those certain 
shear pins with new, improved shear pins. This action is necessary to 
prevent failure of the shear pins in the trunnion assemblies of the 
MLGs, which could result in the collapse of a MLG, and consequent 
reduced controllability of the airplane during takeoff or landing. This 
action is intended to address the identified unsafe condition.

DATES: Effective August 27, 2003.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of August 27, 2003.
    Comments for inclusion in the Rules Docket must be received on or 
before October 14, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2003-NM-141-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via the Internet must contain 
``Docket No. 2003-NM-141-AD'' in the subject line and need not be 
submitted in triplicate. Comments sent via fax or the Internet as 
attached electronic files must be formatted in Microsoft Word 97 or 
2000 or ASCII text.
    The service information referenced in this AD may be obtained from 
Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942. This 
information may be examined at the FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington; at the FAA, Wichita Aircraft 
Certification Office, 1801 Airport Road, Room 100, Mid-Continent 
Airport, Wichita, Kansas; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Greg Davied, Aerospace Engineer, 
Airframe and Propulsion Branch, ACE-118W, FAA, Wichita Aircraft 
Certification Office, 1801 Airport Road, Room 100, Mid-Continent 
Airport, Wichita, Kansas 67209; telephone (316) 946-4128; fax (316) 
946-4107.

SUPPLEMENTARY INFORMATION: The airplane manufacturer notified the FAA 
that results of fatigue testing conducted on the main landing gears 
(MLG) of Learjet Model 45 airplanes indicate that certain shear pins in 
the trunnion assemblies of the MLGs do not meet their expected life 
limit of 20,000 total landings. The shear pins in the trunnion 
assemblies are made of a material that allows hydrogen to penetrate the 
surface of the material, causing the material to become brittle. Under 
impact or dynamic loading such as landing, the brittle material could 
fracture or shatter causing the shear pin(s) to fail before reaching 
the expected life limit. This type of hydrogen penetration usually 
occurs during the manufacturing process.
    The results of fatigue testing also indicate that the shear pin 
bushings in the trunnion fitting housings had migrated outward from the 
fitting, which further weakened the shear pins and contributed to their 
premature failure.
    This condition, if not corrected, could result in the collapse of a 
MLG, and consequent reduced controllability of the airplane during 
takeoff or landing.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Bombardier Service Bulletin 45-
57-6, dated June 9, 2003, which describes procedures for replacing 
certain shear pins in the trunnion assemblies of the MLGs with new, 
improved shear pins. This replacement also includes reidentifying the 
trunnion assemblies. The new, improved shear pins have a maximum life 
limit of 1,800 total landings.
    In addition, we have reviewed Revision 32 of Chapter 4-11-00, dated 
June 13, 2003, of the Learjet 45 Maintenance Manual. Page 2 of Chapter 
4-11-00 specifies a maximum life limit of 1,800 landings for the shear 
pins in the trunnion assemblies of the MLGs.
    Accomplishment of the actions specified in the service bulletin and 
Learjet 45 Maintenance Manual is intended to adequately address the 
identified unsafe condition.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design registered 
in the United States, this AD incorporates a reduced replacement 
interval for certain shear pins in the trunnion assemblies of the MLGs 
into the airworthiness limitations section of the Instructions for 
Continued Airworthiness, and requires replacement of those certain 
shear pins with new, improved shear pins. The actions are required to 
be accomplished in accordance with the service bulletin and Learjet 45 
Maintenance Manual described previously, except as discussed below.

[[Page 47843]]

Differences Between This AD and the Service Bulletin

    Operators should note that this AD is applicable to Learjet Model 
45 airplanes, serial numbers (S/N) 45-005 through 45-208 inclusive, 45-
210 through 45-222 inclusive, 45-224, 45-225, 45-227, and 45-229 
through 45-231 inclusive. The effectivity of Bombardier Service 
Bulletin 45-57-6 lists Model 45 airplanes, S/N 45-005 through 45-222 
inclusive, 45-224, 45-225, and 45-229 through 45-232 inclusive. Since 
that service bulletin was issued, the manufacturer has determined that 
the affected airplanes listed in that service bulletin are incorrect 
and has advised us that it will revise Service Bulletin 45-57-6 to 
apply to the correct airplanes subject to the unsafe condition 
described previously. We agree with the manufacturer's determination 
and have made this AD applicable to those correctly identified 
airplanes.
    Operators should also note that, although the Accomplishment 
Instructions of the service bulletin describe procedures for reporting 
compliance with the service bulletin to the airplane manufacturer, this 
AD does not include such a requirement.

Changes to 14 CFR Part 39/Effect on the AD

    On July 10, 2002, the FAA issued a new version of 14 CFR part 39 
(67 FR 47997, July 22, 2002), which governs the FAA's airworthiness 
directives system. The regulation now includes material that relates to 
altered products, special flight permits, and alternative methods of 
compliance (AMOCs). Because we have now included this material in part 
39, only the office authorized to approve AMOCs is identified in each 
individual AD. However, Note 1 of this AD has been included to address 
material that relates to altered products.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this rule by 
submitting such written data, views, or arguments as they may desire. 
Communications shall identify the Rules Docket number and be submitted 
in triplicate to the address specified under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Submit comments using the following format:
    [sbull] Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    [sbull] For each issue, state what specific change to the AD is 
being requested.
    [sbull] Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
Rules Docket for examination by interested persons. A report that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2003-NM-141-AD.'' The postcard will be date stamped 
and returned to the commenter.

Regulatory Impact

    The regulations adopted herein 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from the Rules Docket at the 
location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness 
directive:

2003-16-09 Learjet: Amendment 39-13262. Docket 2003-NM-141-AD.
    Applicability: Model 45 airplanes, serial numbers 45-005 through 
45-208 inclusive, 45-210 through 45-222 inclusive, 45-224, 45-225, 
45-227, and 45-229 through 45-231 inclusive; certificated in any 
category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the shear pins in the trunnion assemblies 
of the main landing gears (MLG), which could result in the collapse 
of a MLG, and consequent reduced controllability of the airplane 
during takeoff or landing; accomplish the following:

    Note 1: This AD requires revisions to certain operator 
maintenance documents to include new replacements. Compliance with 
these replacements is required by 14 CFR 91.403(c). For airplanes 
that have been previously modified, altered, or repaired in the 
areas addressed by these replacements, the operator may not be able 
to accomplish the replacements 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 in 
accordance with paragraph (e) of this AD. The request should include 
a description of changes to the required replacements 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.


[[Page 47844]]



Revision to the Airworthiness Limitations Section of the Instructions 
for Continuing Airworthiness

    (a) Within 14 days after the effective date of this AD, revise 
the airworthiness limitations (AWL) section of the Instructions for 
Continued Airworthiness by inserting the instructions for Inspection 
Reference Numbers (IRN) J3220041, J3220042, and J3220043 (shear 
pins); as specified on page 2 of Chapter 4-11-00, Revision 32, dated 
June 13, 2003, of the Learjet 45 Maintenance Manual; into the AWL 
section. Thereafter, except as provided in paragraph (e) of this AD, 
no alternative replacement interval may be approved for the shear 
pins in the trunnion assemblies of the MLGs.

Shear Pin Replacement

    (b) Prior to the accumulation of 1,800 total landings on the 
shear pins, or within 100 landings after the effective date of this 
AD, whichever occurs later: Replace the shear pins, having part 
number (P/N) 4532103015-001V1088, 4532103015-003, 4532103025-
001V1088, or 4532103026-001V1088 located in the trunnion assemblies 
of the MLGs with new, improved shear pins (including reidentifying 
the trunnion assemblies); per the Accomplishment Instructions of 
Bombardier Service Bulletin 45-57-6, dated June 9, 2003.

Parts Installation

    (c) As of the effective date of this AD, no person may install 
on any airplane, a shear pin having P/N 4532103015-001V1088, 
4532103015-003, 4532103025-001V1088, or 4532103026-001V1088 in the 
trunnion assemblies of the MLGs.

Information Submission

    (d) Although the service bulletin referenced in this AD 
specifies to submit information to the airplane manufacturer, this 
AD does not include such a requirement.

Alternative Methods of Compliance

    (e) In accordance with 14 CFR 39.19, the Manager, Wichita 
Aircraft Certification Office (ACO), FAA, is authorized to approve 
alternative methods of compliance for this AD.

Incorporation by Reference

    (f) Unless otherwise specified by this AD, the actions shall be 
done per Bombardier Service Bulletin 45-57-6, dated June 9, 2003. 
This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Learjet, Inc., One Learjet Way, 
Wichita, Kansas 67209-2942. Copies may be inspected at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; at the FAA, Wichita Aircraft Certification Office, 1801 
Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas; or 
at the Office of the Federal Register, 800 North Capitol Street, 
NW., suite 700, Washington, DC.

Effective Date

    (g) This amendment becomes effective on August 27, 2003.

    Issued in Renton, Washington, on August 4, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-20238 Filed 8-11-03; 8:45 am]
BILLING CODE 4910-13-P