[Federal Register Volume 68, Number 103 (Thursday, May 29, 2003)]
[Proposed Rules]
[Pages 31999-32001]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-13386]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2002-NM-13-AD]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 45 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Learjet Model 45 
airplanes, that currently requires repetitive application of grease to 
the rotating disk assembly of the nose landing gear (NLG) squat switch 
mechanism. This action would require replacement of the squat switch 
camrod of the NLG, which would terminate the repetitive application; 
and would also reduce the applicability of the exiting AD. This 
proposed AD is prompted by results of tests conducted by the airplane 
manufacturer. The actions specified by this proposed AD are intended to 
prevent moisture contamination and subsequent formation of ice which 
could cause bending and damage of the squat switch assembly, 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 the runway at high speeds during landing.

DATES: Comments must be received by July 14, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FDAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2002-NM-13-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. 2002-NM-13-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.

FOR FURTHER INFORMATION CONTACT: Robert Busto, 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) 946-4157; fax (316) 
946-4107

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 action may be changed in 
light of the comments received.
    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 proposed 
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 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.
    Comments wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2002-NM-13-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,

[[Page 32000]]

ANM-114, Attention: Rules Docket No. 2002-NM-13-AD, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056.

Discussion

    On October 23, 2000, the FAA issued AD 2000-22-04, amendment 39-
11950 (65 FR 65257, November 1, 2000), applicable to certain Learjet 
Model 45 series airplanes, to require repetitive application of grease 
to the rotating disk assembly of the nose landing gear (NLG) squat 
switch mechanism. That action was prompted by tests conducted by the 
manufacturer that indicated a potential unsafe condition exists 
involving damage or bending of the squat switch assembly of the NLG due 
to moisture contamination and subsequent formation of ice. The 
requirements of that AD are intended to prevent bending and damage of 
the squat switch assembly, which could result in driving the nose wheel 
to an uncommanded angle against the force of the steering system, and 
consequently result in the airplane departing the runway at high speeds 
during landing.

FAA's Determination

    In the preamble to AD 2000-22-04, the FAA specified that the 
actions required by that AD were considered ``interim action,'' and 
that the manufacturer was developing a modification to positively 
address the unsafe condition. We indicated that we may consider further 
rulemaking action once the modification was developed, approved, and 
available. The manufacturer now has developed such a modification, and 
we have determined that further rulemaking action is indeed necessary; 
this proposed AD follows from the determination.

Explanation of Relevant Service Information

    Since the issuance of AD 2000-22-04, the FAA has reviewed and 
approved Bombardier Service Bulletin SB 45-32-8, Revision 2, dated 
March 14, 2001, including Compliance Response Form. This service 
bulletin describes procedures for replacement of the camrod in the 
squat switch assembly of the NLG with a camrod made of stronger 
material. The replacement constitutes terminating action for the 
repetitive grease applications required by AD 2000-22-04. This service 
bulletin also recommends that operators complete the Compliance 
Response Form. Accomplishment of the actions specified in the service 
bulletin is intended to adequately address the identified unsafe 
condition.

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 supersede AD 2000-22-04 to continue to require 
repetitive application of grease to the rotating disk assembly of the 
NLG squat switch mechanism. The proposed AD would require replacement 
of the camrod in the squat switch assembly of the NLG, and would also 
reduce the applicability of that AD. The actions would be required to 
be accomplished in accordance with the service bulletin described 
previously, except as discussed below.

Difference Between Proposed AD and Service Bulletin

    Although the Accomplishment Instructions of Bombardier Service 
Bulletin SB 45-32-8, Revision 2, dated March 14, 2001, recommend that 
operators complete the attached Compliance Response Form, this proposed 
AD would not include such a requirement.

Explanation of Change to Applicability

    Operators should note that the applicability of this proposed AD 
differs from the applicability of AD 2000-22-04. This proposed AD has 
reduced the applicability to be consistent with the effectivity 
specified in Bombardier Service Bulletin SB 45-32-8, Revision 2, dated 
March 14, 2001 (which is referenced as the appropriate source of 
service information for this proposed AD). Airplanes having serial 
numbers (S/N) 45-001 through 45-004 inclusive are test airplanes that 
have either been modified for use as prototypes or destroyed; and 
airplanes not modified per Bombardier Service Bulletin SB 45-32-3 do 
not have an NLG squat switch, so they do not have the subject camrod. 
Therefore, those airplanes are not subject to the unsafe condition 
addressed in this proposed AD.
    Additionally, we have re-identified the airplane model designation 
as published in the most recent type certificate data sheet for the 
affected model.

Cost Impact

    There are approximately 110 Model 45 airplanes of U.S. registry 
that would be affected by this proposed AD.
    The actions that are currently required by AD 2000-22-04 take 
approximately 1 work hour per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the currently required actions on U.S. operators is estimated 
to be $6,600, or $60 per airplane.
    The new actions that are proposed in this AD action would take 
approximately 3 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts would cost 
approximately $205 per airplane. Based on these figures, the cost 
impact of the proposed requirements of this AD on U.S. operators is 
estimated to be $42,350, or $385 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this 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 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

[[Page 32001]]

39 of the Federal Aviation Regulations (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.

    2. Section 39.13 is amended by removing amendment 39-11950 (65 FR 
65257, November 1, 2000), and by adding a new airworthiness directive 
(AD), to read as follows:

Learjet: Docket 2002-NM-13-AD. Supersedes AD 2000-22-4, Amendment 
39-11950.

    Applicability: Model 45 airplanes, certificated in any category; 
serial numbers (S/N) 45-005 through 45-071 inclusive, that have been 
modified per Bombardier Service Bulletin 45-32-3; and S/Ns 45-072 
through 45-114 inclusive.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (c)(1) 
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 moisture contamination and subsequent formation of 
ice which could cause bending and damage of the squat switch 
assembly of the nose landing gear (NLG), driving the nose wheel to 
an uncommanded angle against the force of the steering system, and 
consequently resulting in the airplane departing the runway at high 
speeds during landing, accomplish the following:

Restatement of Requirements of AD 2000-22-04, Amendment 39-11950

Application of Grease

    (a) Within 30 days after December 6, 2000 (the effective date of 
AD 2000-22-04, amendment 39-11950): Apply grease to the rotating 
disk assembly of the squat switch assembly of the NLG in accordance 
with Bombardier Service Information Letter SIL 32-016, dated March 
30, 2000. Thereafter, repeat this application at intervals not to 
exceed 30 days until the replacement required by paragraph (b) of 
this AD is accomplished.

New Requirements of this AD

Terminating Action

    (b) Within 300 flight hours or 12 months after the effective 
date of this AD, whichever occurs first: Replace the camrod of the 
squat switch assembly of the NLG with a new assembly in accordance 
with the Accomplishment Instructions of Bombardier Service Bulletin 
SB 45-32-8, Revision 2, dated March 14, 2001, excluding Compliance 
Response Form. Accomplishment of the camrod replacement terminates 
the requirements of this AD.

Alternative Methods of Compliance

    (c)(1) 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 
Officer (ACO), FAA. 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.
    (2) Alternative methods of compliance, approved previously in 
accordance with AD 2000-22-04, amendment 39-11950, are approved as 
alternative methods of compliance with this AD.

    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 Permits

    (d) 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 May 22, 2003.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-13386 Filed 5-28-03; 8:45 am]
BILLING CODE 4910-13-M