03-13386. Airworthiness Directives; Learjet Model 45 Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

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 [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. 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 [phone]; fax [phone]

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:

• 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.
• For each issue, state what specific change to the proposed AD is being requested.
• 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, 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 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.