[Federal Register Volume 65, Number 124 (Tuesday, June 27, 2000)]
[Proposed Rules]
[Pages 39578-39580]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-16235]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-132-AD]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 45 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Learjet Model 45 series 
airplanes. This proposal would require repetitive application of grease 
to the rotating disk assembly of the nose landing gear squat switch 
mechanism. Application of grease to the squat switch assembly is 
necessary to prevent moisture contamination and subsequent formation of 
ice. Such ice formation could result in bending or damaging of the nose 
landing gear squat switch assembly, which could drive the nose wheel to 
an uncommanded angle against the force of the steering system. This 
condition, if not corrected, could result in the airplane departing 
from the runway at high speeds during landing.

DATES: Comments must be received by August 11, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-132-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: 
<a href="/cdn-cgi/l/email-protection#40796d212e2d6d2e30322d232f2d2d252e34002621216e272f36"><span class="__cf_email__" data-cfemail="3b02165a555616554b4956585456565e554f7b5d5a5a155c544d">[email protected]</span></a>. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-132-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 for Windows or 
ASCII text.
    The service information referenced in the proposed rule 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, 
Small Airplane Directorate,

[[Page 39579]]

Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, 
Mid-Continent Airport, Wichita, Kansas.

FOR FURTHER INFORMATION CONTACT: Shane Bertish, Aerospace Engineer, 
Systems and Equipment Branch, ACE-116W, FAA, Small Airplane 
Directorate, 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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Submit comments using the following format:
    <bullet> 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.
    <bullet> For each issue, state what specific change to the proposed 
AD is being requested.
    <bullet> 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 proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-132-AD.'' The postcard will be date stamped 
and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2000-NM-132-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The manufacturer of Learjet Model 45 series airplanes has conducted 
tests in a laboratory that indicate a potential unsafe condition exists 
involving damage or bending of the squat switch assembly of the nose 
landing gear. Freezing of moisture in the squat switch assembly may 
cause restriction of movement of the subcomponents of the assembly and 
result in bending or damage of the squat switch assembly. (If certain 
movement is restricted, the loads imposed from the nose landing gear 
exceed the structural capability of the squat switch assembly and 
bending and damage occur.) The laboratory tests indicate that 
appropriate application of grease to the squat switch assembly will 
prevent moisture contamination of the assembly. Bending and damage of 
the squat switch assembly could result in driving the nose wheel to an 
uncommanded angle against the force of the steering system. This 
condition, if not corrected, could result in the airplane departing 
from the runway at high speeds during landing.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Bombardier Aerospace Service 
Information Letter SIL 32-016, dated March 30, 2000, which describes 
procedures for lubricating the rotating-disc assembly of the nose 
landing gear squat switch mechanism.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the service information described previously.

Interim Action

    This is considered to be interim action. The manufacturer has 
advised that it currently is developing a modification that will 
positively address the unsafe condition addressed by this AD. Once this 
modification is developed, approved, and parts are available, the FAA 
may consider additional rulemaking.

Cost Impact

    There are approximately 69 Learjet Model 45 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 45 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 1 work hour per airplane to accomplish the 
proposed actions, and that the average labor rate is $60 per work hour. 
Based on these figures, the cost impact of the proposed AD on U.S. 
operators is estimated to be $2,700, or $60 per airplane, per 
application.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein 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. Therefore, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

[[Page 39580]]

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. Section 39.13 is amended by adding the following new 
airworthiness directive:

Learjet: Docket 2000-NM-132-AD.
    Applicability: Model 45 series airplanes, serial numbers 45-001 
through 45-114 inclusive, certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (b) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent the airplane from departing the runway at high speeds 
during landing due to bending and damage to the squat switch 
assembly of the nose landing gear; accomplish the following:

Application of Grease

    (a) Within 30 days after the effective date of this AD, apply 
grease to the rotating disk assembly of the squat switch mechanism 
of the nose wheel in accordance with Bombardier Aerospace Service 
Information Letter SIL 32-016, dated March 30, 2000. Thereafter, 
repeat this application at intervals not to exceed 30 days.

Alternative Methods of Compliance

    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Wichita Aircraft Certification 
Office (ACO), FAA, Small Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Wichita ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Wichita ACO.

Special Flight Permit

    (c) Special flight permits may be issued in accordance with 
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.

    Issued in Renton, Washington, on June 21, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-16235 Filed 6-26-00; 8:45 am]
BILLING CODE 4910-13-P


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