Airworthiness Directives; Learjet Model 45 Airplanes

[Federal Register Volume 68, Number 76 (Monday, April 21, 2003)]
[Rules and Regulations]
[Pages 19328-19330]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-9430]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2003-NM-88-AD; Amendment 39-13121; AD 2003-06-51]
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 document publishes in the Federal Register an amendment 
adopting airworthiness directive (AD) 2003-06-51 that was sent 
previously to all known U.S. owners and operators of certain Learjet 
Model 45 airplanes by individual notices. This AD requires an 
inspection to determine the part number of the horizontal stabilizer 
actuator assembly (A66), and replacement of any suspect horizontal 
stabilizer actuator assembly (A66) with a new or serviceable actuator 
assembly (A66). This action is prompted by a report of severe vibration 
followed by a rapid nose down pitch change on a Learjet Model 45 
airplane. The actions specified by this AD are intended to prevent 
structural failure of the horizontal stabilizer actuator assembly, 
which could result in possible loss of control of the airplane.

DATES: Effective April 28, 2003, to all persons except those persons to 
whom it was made immediately effective by emergency AD 2003-06-51, 
issued on March 20, 2003, which contained the requirements of this 
amendment.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 28, 2003.
    Comments for inclusion in the Rules Docket must be received on or 
before June 20, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2003-NM-88-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 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 fax or the Internet must 
contain ``Docket No. 2003-NM-88-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 or 2000 for 
Windows or ASCII text.
    The applicable service information 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; or 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: David Hirt, Aerospace Engineer, 
Systems and Equipment Branch, ACE-116W, FAA, Wichita Aircraft 
Certification Office, 1801 Airport Road, Room 100, Mid-Continent 
Airport, Wichita, Kansas 67209; telephone (316) 946-4156; fax (316) 
946-4407.

SUPPLEMENTARY INFORMATION: On March 20, 2003, the FAA issued emergency 
airworthiness directive (AD) 2003-06-51, which is applicable to certain 
Learjet Model 45 airplanes.

Background

    The FAA has received a report of severe vibration followed by a 
rapid nose down pitch change on a Learjet Model 45 airplane. 
Investigation revealed that the acme screw of the horizontal stabilizer 
actuator assembly was fractured. The actuator features a dual load 
path. The actuator assembly's primary load path, the acme screw, 
failed. Loads should have been retained by the secondary internal 
retaining rod. However, the threaded nut on the secondary internal 
retaining rod had worked completely off, either latently before the 
fracture or from the effects of the fractured screw. The cause of such 
failure has not been determined.
    There have been no previous reports of fractured acme screws of the 
horizontal stabilizer actuator assembly. However, there have been 
reports of cracks in the acme screw. As a result of these reports, the 
acme screw design was changed in February 2000 to reduce the 
probability of crack initiation. The fractured acme screw was an early 
design that did not have the design improvements incorporated to reduce 
the probability of crack initiation.
    Structural failure of the horizontal stabilizer actuator assembly 
could result in possible loss of control of the airplane.

[[Page 19329]]

Explanation of Relevant Service Information

    The FAA has reviewed and approved Bombardier Learjet Alert Service 
Bulletin SB A45-27-15, dated March 20, 2003, including Service Bulletin 
Compliance Response, which describes procedures for performing an 
inspection to determine the part number (P/N) of the horizontal 
stabilizer actuator assembly (A66), and replacing any horizontal 
stabilizer actuator assembly (A66) having P/N 6627401000-001 or P/N 
2A9200F with a new or serviceable actuator assembly (A66) having P/N 
6627401000-005. Accomplishment of the actions specified in the alert 
service bulletin is intended to adequately address the identified 
unsafe condition.

Explanation of Requirements of the Rule

    Since the unsafe condition described is likely to exist or develop 
on other airplanes of the same type design, the FAA issued emergency AD 
2003-06-51 to prevent structural failure of the horizontal stabilizer 
actuator assembly, which could result in possible loss of control of 
the airplane. The AD requires an inspection to determine the P/N of the 
horizontal stabilizer actuator assembly (A66), and replacement of any 
horizontal stabilizer actuator assembly (A66) having P/N 6627401000-001 
or P/N 2A9200F with a new or serviceable actuator assembly (A66) having 
P/N 6627401000-005. The actions are required to be accomplished in 
accordance with the alert service bulletin described previously.

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 AD system. The 
regulation now includes material that relates to altered products, 
special flight permits, and alternative methods of compliance. This 
material is included in part 39. However, as amended, part 39 provides 
for the FAA to add special requirements for operating an airplane to a 
repair facility to do the work required by an AD. For purposes of this 
emergency AD, we have determined that such a special flight permit is 
permitted, but with certain limitations.

Determination of Rule's Effective Date

    Since it was found that immediate corrective action was required, 
notice and opportunity for prior public comment thereon were 
impracticable and contrary to the public interest, and good cause 
existed to make the AD effective immediately by individual notices 
issued on March 20, 2003, to all known U.S. owners and operators of 
certain Learjet Model 45 airplanes. These conditions still exist, and 
the AD is hereby published in the Federal Register as an amendment to 
section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to 
make it effective to all persons.

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.
    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-88-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:

2003-06-51 Learjet: Amendment 39-13121. Docket 2003-NM-88-AD.

    Applicability: Model 45 airplanes, serial numbers 45-001 through 
45-232 inclusive; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent structural failure of the horizontal stabilizer 
actuator assembly, which could result in possible loss of control of 
the airplane, accomplish the following:

Inspection

    (a) Before further flight, do an inspection to determine the 
part number (P/N) of the horizontal stabilizer actuator assembly 
(A66), per paragraph 2., ``Accomplishment Instructions,'' of 
Bombardier Learjet Alert Service Bulletin SB A45-27-15, dated March 
20, 2003, excluding Service Bulletin Compliance Response.

Corrective Action

    (b) If a horizontal stabilizer actuator assembly (A66) having P/
N 6627401000-001 or P/N 2A9200F is found installed during the 
inspection required by paragraph (a) of this

[[Page 19330]]

AD, before further flight, replace the horizontal stabilizer 
actuator assembly (A66) with a new or serviceable actuator assembly 
(A66) having P/N 6627401000-005, per paragraph 2., ``Accomplishment 
Instructions,'' of Bombardier Learjet Alert Service Bulletin SB A45-
27-15, dated March 20, 2003, excluding Service Bulletin Compliance 
Response.

Parts Installation

    (c) As of the effective date of this AD, no person shall install 
any horizontal stabilizer actuator assembly (A66) having P/N 
6627401000-001 or P/N 2A9200F, on any airplane.

Special Flight Permit

    (d) Special flights may be issued for flights limited to 
required flight crew only, per sections 21.197 and 21.199 of the 
Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate 
the airplane to a location where the requirements of this AD can be 
accomplished.

Alternative Methods of Compliance

    (e) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Alternative methods of compliance for this emergency AD will be 
approved by the Manager, Wichita Aircraft Certification Office 
(ACO), FAA. Contact David Hirt, Wichita ACO, FAA, for information 
about previously approved alternative methods of compliance.

Incorporation by Reference

    (f) The actions shall be done in accordance with Bombardier 
Learjet Alert Service Bulletin SB A45-27-15, dated March 20, 2003, 
excluding Service Bulletin Compliance Response. 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; or 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 April 28, 2003, to all 
persons except those persons to whom it was made immediately 
effective by emergency AD 2003-06-51, issued on March 20, 2003, 
which contained the requirements of this amendment.

    Issued in Renton, Washington, on April 11, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-9430 Filed 4-18-03; 8:45 am]
BILLING CODE 4910-13-P

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