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Proposed Rule

Airworthiness Directives; Learjet Model 60 Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

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Start Preamble

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 60 airplanes, that currently requires inspection to detect bends in or damage to the fuel crossflow tube; inspection to determine clearance between the fuel crossflow tube and the flight control cables; and replacement or repair of the tube, if necessary. This action would require a review of airplane maintenance records or an inspection to determine if a fuel crossflow tube having a certain part number is installed; and follow-on/corrective actions, as applicable. This action also would expand the applicability of the existing AD to include additional airplanes. The actions specified by the proposed AD are intended to prevent chafing and consequent failure of the fuel crossflow tube due to inadequate clearance between the tube and the flight control cables, which could result in loss of fuel from one fuel tank during normal operating conditions or loss of fuel from both main fuel tanks during fuel cross-feeding operations. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by August 4, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-408-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: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-408-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 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.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Jeffrey Janusz, Aerospace Engineer, Systems and Propulsion Branch, ACE-116W, FAA, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316) 946-4148; fax (316) 946-4407.

End Further Info End Preamble Start Supplemental Information

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.

Commenters 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 2000-NM-408-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-408-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On June 28, 1995, the FAA issued airworthiness directive (AD) 95-14-09, amendment 39-9303 (60 FR 36984, July 19, 1995), applicable to certain Learjet 60 airplanes, to require inspection to detect bends in or damage to the fuel crossflow tube; inspection to determine clearance between the fuel crossflow tube and the flight control cables; and replacement or repair of the tube, if necessary. That action was prompted by reports of chafing of the fuel crossflow tube by flight control cables. The requirements of that AD are intended to prevent chafing and consequent failure of the fuel crossflow tube due to inadequate clearance between the tube and the flight control cables, which could result in loss of fuel from one fuel tank during normal operating conditions or loss of fuel from both main fuel tanks during fuel cross-feeding operations.

Actions Since Issuance of Previous Rule

Since the issuance of that AD, the manufacturer has implemented a design change to adequately preclude chafing or bending of the fuel crossflow tube. Although the minimum clearance required by AD 95-14-09 was adequate, there was a possibility that the fuel crossflow tube could be installed incorrectly due to installation variables, including rotation of the fuel crossflow tube. The design change calls for an increased minimum clearance and the installation of a specific part number for the fuel crossflow tube, which can be installed in only one way.

Explanation of New Service Information

The FAA has reviewed and approved Bombardier Learjet 60 Alert Service Bulletin SB A60-28-3, Revision 2, dated October 26, 1998. This service bulletin describes procedures for inspecting the fuel crossflow tube for damage (e.g., chafing and/or bends), measuring the clearance between the Start Printed Page 36503crossflow tube and flight control cables, and correcting incorrect clearance. For certain airplanes, this service bulletin also describes procedures for replacing existing fuel crossflow tubes with new fuel crossflow tubes. This service bulletin also adds certain airplanes to the effectivity listing.

We also have reviewed and approved Bombardier Learjet 60 Service Bulletin SB 60-28-4, Revision 2, dated August 22, 2001. For certain airplanes, this service bulletin describes procedures for replacing existing fuel crossflow tubes with new fuel crossflow tubes, and measuring the clearance between the crossflow tube and flight control cables.

Accomplishment of the actions specified in these service bulletins 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 95-14-09 to require a review of maintenance records or an inspection to determine if a fuel crossflow tube having a certain part number is installed; and follow-on/corrective actions, as applicable. Certain actions would be required to be accomplished in accordance with the service bulletins described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletins

Operators should note the following differences between the proposed AD and the service bulletins:

  • Bombardier Learjet 60 Alert Service Bulletin SB A60-28-3, Revision 2, recommends that the fuel crossflow tube be inspected for bends and evidence of damage (e.g., contact with the flight control cables). It also recommends that the clearance between the fuel crossflow tube and flight control cables be measured to ensure that it is at least 0.150 inch. This proposed AD would not require those inspections because they pertain to the previous airplane design. In lieu of the previously described inspections for bends and evidence of damage, this proposed AD would require a review of the airplane maintenance records or an inspection to determine if a certain part number for the fuel crossflow tube is installed. In addition, the proposed AD would require measurement of the clearance between the fuel crossflow tube and flight control cables to ensure that it is at least 0.35 inch. We have determined that an interval of 25 flight hours (after the effective date of this proposed AD) for accomplishment of the review of the airplane maintenance records/inspection would address the identified unsafe condition in a timely manner.
  • Alert Service Bulletin A60-28-3, Revision 2, also recommends a compliance time of 600 flight hours to replace the fuel crossflow tube, if necessary. This proposed AD would extend the compliance time to require replacement of any fuel crossflow tube not having the correct part number, with a new tube having the correct part number, within 90 days after the proposed inspection. In developing an appropriate compliance time for this proposed AD, we considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the inspection. In light of all of these factors, the FAA finds a longer compliance time for completing the proposed actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.
  • Bombardier Learjet 60 Service Bulletins SB A60-28-3, Revision 2, and SB 60-28-4, Revision 2, specify that if the correct fuel crossflow tube part number is installed and if the specified minimum clearance does not exist between the fuel crossflow tube and the flight control cables, the manufacturer may be contacted for disposition. This proposed AD would require that correction of any incorrect clearances be accomplished per a method approved by the FAA.

Clarification of Part Number for Installation

Operators should note that, in Bombardier Learjet 60 Alert Service Bulletin SB A60-28-3, Revision 2, the fuel crossflow tube to be installed in the airplane is incorrectly identified as part number (P/N) 6026020-001 in Figure 1, detail D; the correct P/N is 6026020-005. The FAA has been advised that the manufacturer will issue a revision to this alert service bulletin to correct the error.

Changes to the Applicability of the Existing AD

This proposed AD would expand the applicability to include affected airplanes having serial numbers 60-056 through 60-145 inclusive, in addition to serial numbers 60-001 through 60-055 inclusive identified in the existing AD. All of these airplanes are subject to the identified unsafe condition of this AD.

Changes to 14 CFR Part 39/Effect on the Proposed 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 directive system. The regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance (AMOC). Because we have now included this material in part 39, only the office authorized to approve AMOCs is identified in each individual AD. Therefore paragraph (d) and Note 1 of AD 95-14-09 have not been included in this proposed AD. Paragraph (c) of AD 95-14-09 has been revised to only identify the office authorized to approve AMOCs, and is identified as paragraph (f) in this proposed AD.

Cost Impact

There are approximately 145 Model 60 airplanes of the affected design in the worldwide fleet. The FAA estimates that 109 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 2 work hours per airplane to accomplish the review of airplane maintenance records/inspection proposed in this AD action, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $13,080, or $120 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 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 Start Printed Page 36504a “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.

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List of Subjects in 14 CFR Part 39

End List of Subjects

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:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

End Authority
[Amended]

2. Section 39.13 is amended by removing amendment 39-9303 (60 FR 36984, July 19, 1995), and by adding a new airworthiness directive (AD), to read as follows:

Learjet: Docket 2000-NM-408-AD. Supersedes AD 95-14-09, Amendment 39-9303.

Applicability: Model 60 airplanes, serial numbers 60-001 through 60-145 inclusive, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent chafing and consequent failure of the fuel crossflow tube due to inadequate clearance between the tube and the flight control cables, which could result in loss of fuel from one fuel tank during normal operating conditions or loss of fuel from both main fuel tanks during fuel cross-feeding operations, accomplish the following:

Part Identification

(a) Within 25 flight hours after the effective date of this AD, inspect the fuel crossflow tube to determine whether part number (P/N) 5026020-005 is installed. Instead of inspecting the tube, a review of airplane maintenance records is acceptable if the P/N of the tube can be positively determined from that review.

Clearance Measurement and Corrective Action

(b) For all airplanes: If P/N 6026020-005 is found installed during the review or inspection required by paragraph (a) of this AD, before further flight, measure the clearance between the fuel crossflow tube and the flight control cables to determine if it is at least 0.35 inch, per paragraph 2.B.(8) of the Accomplishment Instructions of Bombardier Learjet 60 Alert Service Bulletin SB A60-28-3, Revision 2, dated October 26, 1998.

(1) If the clearance is 0.35 inch or more, no further action is required by this paragraph.

(2) If the clearance is less than 0.35 inch, before further flight, repair per a method approved by the Manager, Wichita Aircraft Certification Office (ACO), FAA.

Part Replacement, Measurement, and Repair

(c) For airplanes having serial numbers 60-001 through 60-055: If P/N 6026020-005 is not found installed during the review or inspection required by paragraph (a) of this AD, within 90 days after accomplishing the review or inspection, replace the existing fuel crossflow tube with a new fuel crossflow tube having P/N 6026020-005, and measure the clearance between the newly installed fuel crossflow tube and the flight control cables, per paragraph 2.A. of the Accomplishment Instructions of Bombardier Learjet 60 Service Bulletin SB 60-28-4, Revision 2, dated August 22, 2001.

(1) If the clearance is 0.35 inch or more, no further action is required by this paragraph.

(2) If the clearance is less than 0.35 inch, before further flight, repair per a method approved by the Manager, Wichita ACO, FAA.

(d) For airplanes having serial numbers 60-056 through 60-145: If P/N 6026020-005 is not found installed during the review or inspection required by paragraph (a) of this AD, within 90 days after accomplishing the review or inspection, replace the existing fuel crossflow tube with a new fuel crossflow tube having P/N 6026020-005, and measure the clearance between the newly installed fuel crossflow tube and the flight control cables to determine if the clearance is at least 0.35 inch, per paragraph 2.B. of the Accomplishment Instructions of Bombardier Learjet 60 Alert Service Bulletin SB 60-28-3, Revision 2, dated October 26, 1998.

(1) If the clearance is 0.35 inch or more, no further action is required by this paragraph.

(2) If the clearance is less than 0.35 inch, before further flight, repair per a method approved by the Manager, Wichita ACO, FAA.

Note 1:

Alert Service Bulletin SB A60-28-3, Revision 2, Figure 1, detail D., incorrectly identifies the fuel crossflow tube to be installed as P/N 6026020-001. The manufacturer is aware of this error and plans to correct the part number in the next revision of the alert service bulletin.

Part Installation

(e) As of the effective date of this AD, only fuel crossflow tubes having P/N 6026020-005 shall be installed on any airplane.

Alternative Methods of Compliance

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

Start Signature

Issued in Renton, Washington, on June 12, 2003.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 03-15339 Filed 6-17-03; 8:45 am]

BILLING CODE 4910-13-P