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Proposed Rule

Airworthiness Directives; Boeing Model 737-200, -200C, -300, -400, and -500 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing airplane models, that would have superseded an existing AD currently requiring either inspections for discrepancies of the fueling float switch wiring in the center fuel tank and follow-on actions, or deactivation of the float switch. The proposed AD would have removed the option to deactivate the float switch and would have required repetitive inspections for discrepancies of the float switch wiring and various other actions. This new action would require replacing the float switches in the center and wing fuel tanks with new, improved parts, installing a conduit liner system in the center fuel tank, and replacing conduit assemblies in the wing fuel tanks with new parts, which would terminate the existing requirements. For certain airplanes, this new action also would require replacing certain existing sections of the electrical conduit in the center fuel tank with new conduit. This new action also would add one additional airplane model to the applicability and remove another. These actions are necessary to prevent contamination of the fueling float switch by moisture or fuel, and chafing of the float switch wiring against the fuel tank conduit, which could present an ignition source inside the fuel tank that could cause a fire or explosion. These actions are intended to address the identified unsafe condition.

DATES:

Comments must be received by July 7, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-78-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. 99-NM-78-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 Boeing Commercial Airplane Group, PO Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Sherry Vevea, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6514; fax (425) 917-6590.

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 99-NM-78-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. 99-NM-78-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on April 28, 2000 (65 FR 24889). That NPRM proposed to supersede AD 99-05-12, amendment 39-11060 (64 FR 10213, March 3, 1999). (A correction of that AD was published in the Federal Register on March 9, 1999 (64 FR 11533).) That proposal would have continued to require inspection of the fueling float switch wiring in the center fuel tank to detect discrepancies, accomplishment of corrective actions, and installation of double Teflon sleeving over the wiring of the float switch. That NPRM would Start Printed Page 34844have eliminated deactivation of the float switch as an option for complying with the existing AD, and would have required, for all affected airplanes, repetitive inspections of the float switch wiring to detect discrepancies, replacement of the float switch and wiring if necessary, and replacement of the double Teflon sleeving. For certain airplanes, that NPRM also would have added a new requirement for inspection and installation of partial double Teflon sleeving in a certain area. That NPRM was prompted by a report indicating that chafing of the direct current (DC) powered float switch wiring insulation in the center fuel tank occurred on several airplanes. That condition, if not corrected, could result in arcing from the wiring to the in-tank conduit, which could present an ignition source inside the fuel tank and result in consequent fire/explosion.

In the preamble to AD 99-05-12, we stated that the actions required by that AD were considered “interim action” and that we were considering further rulemaking action. We have now determined that further rulemaking action is indeed necessary, and this supplemental NPRM follows from that determination.

Actions Since Issuance of Previous Proposal

Since the issuance of that NPRM, the FAA has reviewed and approved Boeing Alert Service Bulletin 737-28A1141, Revision 1, dated December 19, 2002. That service bulletin describes procedures for replacing the existing float switches with new, improved float switches and installing a conduit liner system in the center fuel tanks, and replacing the float switches and conduit assemblies with new, improved float switches and conduit assemblies in the wing fuel tanks. The new, improved float switches are more resistant to contamination by fuel or moisture, and the new conduit assemblies for the float switch eliminate sharp bends within the conduit and include a conduit liner system that provides added protection against chafing of the float switch wiring. For airplanes on which the float switch for the center fuel tank was deactivated previously, the service bulletin also contains procedures for removal of placards and stencils associated with that deactivation. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Other Relevant Rulemaking

We have previously issued AD 2002-26-18, amendment 39-13006 (68 FR 481, January 6, 2003), which applies to Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD requires replacement of the existing fueling float switch and conduit assemblies in the main and center fuel tanks with new, improved assemblies. This supplemental NPRM would require similar actions for Model 737-200, -200C, -300, -400, and -500 series airplanes.

Comments

Due consideration has been given to the comments received in response to the original NPRM. Certain comments are no longer relevant because of the issuance of the service bulletin described previously. Certain other comments have revealed a need for clarification, as explained below.

Support for the Original NPRM

Two commenters support the original NPRM.

Request To Provide Credit for Actions Accomplished Previously

One commenter requests that a statement be added to the proposed AD to clarify that credit is given for accomplishment of the proposed initial inspection and replacement prior to the effective date of this AD.

Though the FAA concurs with the commenter's intent, the FAA does not concur that any change to the supplemental NPRM is necessary. Credit for actions accomplished previously is given by means of the phrase in the “Compliance” section of the AD, “Required as indicated, unless accomplished previously.”

Request To Provide for Airplanes Grounded for Extended Period

One commenter requests that the original NPRM be revised “to be written in such a manner [that] would not require inspecting airplanes [that] have been grounded for an extended period, until they are prepared for return to service.”

The FAA points out that no change to the supplemental NPRM is necessary to meet the intent of the commenter's request. Part 39.3 of the Federal Aviation Regulations (14 CFR 39.3) states that, “No person may operate a product to which an airworthiness directive applies except in accordance with the requirements of that airworthiness directive.” This regulation provides relief for airplanes that are not being operated because affected airplanes need only be in compliance prior to their return to service.

Explanation of Change Made to Restatement of AD 99-05-12

As explained in the original NPRM, paragraph (a) of this supplemental NPRM, which is restated from AD 99-05-12, states that the paragraph applies to Model 737-200, -300, -400, and -500 series airplanes having line numbers 1 through 3108 inclusive. Paragraph (a) of AD 99-05-12 did not specify the line numbers affected by that paragraph. The FAA has determined that airplanes having line numbers 3109 and subsequent had double Teflon sleeving installed over the wiring of the float switch during production. Therefore, it is not necessary for operators of these airplanes to accomplish paragraph (a) of this supplemental NPRM.

Explanation of Applicability of Supplemental NPRM

Boeing Model 737-200C series airplanes are not specifically identified in the applicability of the existing AD or the original NPRM. However, certain Model 737-200C series airplanes are included in the effectivity listings of Boeing Alert Service Bulletins 737-28A1132 and 737-28A1141, and those airplanes are subject to the actions specified in those service bulletins. Therefore, for Model 737-200C series airplanes, we have added a new paragraph (f) to this supplemental NPRM to require accomplishment of the actions required by paragraph (b) or (c) of this AD prior to the accumulation of 30,000 flight hours, or within 30 days after the effective date of this AD, whichever is later. If the actions specified in paragraph (b) or (c) of this AD have already been accomplished before the effective date of the AD, no further action would be required by paragraph (f) of this AD.

Also, Model 737-100 series airplanes have been removed from the applicability statement of this supplemental NPRM. These airplanes are not affected by the proposed actions and were inadvertently included in the original NPRM.

Explanation of Additional Changes to Original NPRM

We have changed all references to “detailed visual inspection” in the original NPRM to “detailed inspection” in this supplemental NPRM.

Conclusion

Since certain changes described previously expand the scope of the originally proposed rule, we have determined that it is necessary to reopen the comment period to provide additional opportunity for public comment. Start Printed Page 34845

Explanation of Proposed Requirements of Supplemental NPRM

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, this supplemental NPRM proposes to supersede AD 99-05-12 to continue to require inspection of the fueling float switch wiring in the center fuel tank to detect discrepancies, accomplishment of corrective actions, and installation of double Teflon sleeving over the wiring of the float switch. The supplemental NPRM would require replacement of the float switches with new, improved float switches and installation of a conduit liner system in the center fuel tank, and replacement of the float switches and conduit assemblies with new, improved float switches and conduit assemblies in the wing fuel tanks. This replacement would terminate the requirements of the existing AD. The float switch replacements would be required to be done in accordance with Boeing Alert Service Bulletin 737-28A1141, Revision 1. For certain airplanes, the supplemental NPRM would require replacement of certain sections of conduit in the center fuel tank with new conduit, in accordance with Boeing Alert Service Bulletin 737-28A1132, Revision 2, dated June 17, 1999.

Cost Impact

There are approximately 2,886 Model 737-200, -200C, -300, -400, and -500 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,111 airplanes of U.S. registry would be affected by this supplemental NPRM.

The removal and inspection of the fueling float switch in the center fuel tank and installation of double Teflon sleeving, which is provided as one alternative for compliance with AD 99-05-12, takes approximately 18 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts cost approximately $30 per airplane. Based on these figures, the cost impact of the removal and inspection of the float switch and installation of double Teflon sleeving, if accomplished, is estimated to be $1,110 per airplane.

The deactivation of the float switch and installation of “Caution” signs that are provided as the other alternative for compliance with AD 99-05-12, takes approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the deactivation and installation, if accomplished, is estimated to be $180 per airplane.

The new replacement of float switches and installation of a conduit liner in the center fuel tank, and the replacement of float switches and conduit assemblies in the wing fuel tanks, that are proposed in this supplemental NPRM would take approximately 62 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost between $3,633 and $5,061 per airplane. Based on these figures, the cost impact of the proposed replacement is estimated to be between $7,353 and $8,781 per airplane.

The cost impact figures discussed above are 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 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.

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List of Subjects in 14 CFR Part 39

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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:

Start Authority

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

End Authority
[Amended]

2. Section 39.13 is amended by removing amendment 39-11060 (64 FR 10213, March 3, 1999), corrected at 64 FR 11533, March 9, 1999, and by adding a new airworthiness directive (AD), to read as follows:

BOEING: Docket 99-NM-78-AD. Supersedes AD 99-05-12, Amendment 39-11060.

Applicability: Model 737-200, -200C, -300, -400, and -500 series airplanes; on which the center wing tanks are activated; excluding those airplanes equipped with center wing tank volumetric topoff systems, or alternating current (AC) powered center tank float switches; 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 (k)(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 contamination of the fueling float switch by moisture or fuel, and chafing of the float switch wiring against the fuel tank conduit, which could present an ignition source inside the fuel tank that could cause a fire or explosion, accomplish the following:

Requirements of AD 99-05-12:

Compliance Time for Initial Action

(a) For Model 737-200, -300, -400, and —500 series airplanes having line numbers (L/N) 1 through 3108 inclusive: Prior to the accumulation of 30,000 total flight hours, or within 30 days after March 18, 1999 (the effective date of AD 99-05-12, amendment 39-11060), whichever occurs later, accomplish the requirements of paragraph (b) or (c) of this AD. Start Printed Page 34846

Initial Inspection: Procedures

(b) Remove the fueling float switch and wiring from the center fuel tank and perform a detailed inspection of the float switch wiring to detect discrepancies (i.e., evidence of electrical arcing, exposure of the copper conductor, presence or scent of fuel on the electrical wires, or worn insulation), in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999. After the effective date of this AD, only Revision 2 may be used. Pay particular attention to the wire bundle where it passes through the wing pylon vapor seals and under the wire bundle clamps.

Note 2:

For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

Initial Inspection: Follow-On Actions

(1) If no discrepancy is detected, prior to further flight, accomplish either paragraph (b)(1)(i) or (b)(1)(ii) of this AD.

(i) Measure the resistance between the wires and the float switch housing, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999.

(A) If the resistance is less than 200 megohms, prior to further flight, replace the float switch and wiring with a new float switch and wiring, and install double Teflon sleeving over the wiring of the float switch, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999; or replace the float switch and wiring with a new, improved float switch and wiring in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1141, Revision 1, dated December 19, 2002. After the effective date of this AD, only a new, improved float switch and wiring may be installed. If a replacement float switch and wiring are not available, prior to further flight, accomplish the requirements specified in paragraphs (c) and (d) of this AD.

(B) If the resistance is greater than or equal to 200 megohms, prior to further flight, blow dirt out of the conduit, install double Teflon sleeving over the wiring of the float switch, and reinstall the existing float switch, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999.

(ii) Replace the float switch and wiring with a new float switch and wiring, and install double Teflon sleeving over the wiring of the float switch, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999; or replace the float switch and wiring with a new, improved float switch and wiring in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1141, Revision 1, dated December 19, 2002. After the effective date of this AD, only a new, improved float switch and wiring may be installed. If a replacement float switch and wiring are not available, prior to further flight, accomplish the requirements specified in paragraphs (c) and (d) of this AD.

(2) If any worn insulation is detected, and if no copper conductor is exposed, and if no evidence of arcing is detected; accomplish the requirements specified in either paragraph (b)(1)(i) or (b)(1)(ii) of this AD.

(3) If any electrical arcing or exposed copper conductor is detected, prior to further flight, accomplish either paragraph (b)(3)(i) or (b)(3)(ii) of this AD.

(i) Replace any section of the electrical conduit where the arcing occurred with a new section, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999; and accomplish the requirements specified in paragraph (b)(1)(ii) of this AD.

(ii) Perform a detailed inspection to detect fuel leaks of the electrical conduit, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999.

(A) If no fuel leak is detected, prior to further flight, accomplish the requirements specified in paragraph (b)(1)(ii) of this AD. Repeat the inspection required by paragraph (b)(3)(ii) of this AD thereafter at intervals not to exceed 1,500 flight hours, until the replacement required by paragraph (b)(3)(ii)(B) of this AD is accomplished.

(B) If any fuel leak is detected, prior to further flight, replace, with new conduit, any section of the electrical conduit where a leak is found, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999. Prior to further flight after accomplishment of the replacement, accomplish the requirements specified in paragraph (b)(1)(ii) of this AD. Accomplishment of electrical conduit replacement constitutes terminating action for the repetitive inspection requirements of paragraph (b)(3)(ii)(A) of this AD.

(4) If any presence or scent of fuel on the electrical wires is detected, prior to further flight, locate the source of the leak and replace the damaged conduit with a new conduit, in accordance with the alert service bulletin; and accomplish the requirements specified in either paragraph (b)(1)(i) or (b)(1)(ii) of this AD, unless accomplished previously in accordance with paragraph (b)(1), (b)(2), or (b)(3) of this AD.

Deactivation of Float Switch

(c) Accomplish the requirements specified in either paragraph (c)(1) or (c)(2) of this AD, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999.

(1) Deactivate the center tank float switch (i.e., cut the two wires for the float switch at the splices on the front spar and cap and stow the four wire ends), paint a “Caution” sign that shows a conservative maximum fuel capacity for the center tank on the underside of the right-hand wing near the fueling station door, and install an INOP placard on the fueling panel.

(2) Deactivate the center tank float switch (i.e., cut, stow, and splice the two wires for the float switch at the splices on the front spar), and paint a “Caution” sign that shows a conservative maximum fuel capacity for the center tank on the underside of the right-hand wing near the fueling station door.

Deactivation of Float Switch: Additional Requirements

(d) For airplanes on which the requirements specified in paragraph (c) of this AD have been accomplished: Accomplish the requirements specified in paragraphs (d)(1), (d)(2), and (d)(3) of this AD.

(1) Operators must ensure that airplane fueling crews are properly trained in accordance with the procedures specified in Boeing Telex M-7200-98-04486, dated December 1, 1998, or procedures approved by the FAA. This one-time training must be accomplished prior to utilizing the procedures specified in paragraph (d)(3) of this AD.

(2) Prior to fueling the airplane, perform a check to verify that the fueling panel center tank quantity indicator is operative. Repeat this check thereafter prior to fueling the airplane. If the fueling panel center tank quantity indicator is not operative, prior to further flight, replace the fueling panel center tank quantity indicator with a serviceable part.

(3) One of the two manual fueling procedures for the center fuel tank must be used for each fueling occurrence, in accordance with Boeing Telex M-7200-98-04486, dated December 1, 1998, or a method approved by the FAA.

Note 3:

For the purposes of this AD, the term “the FAA,” is defined in paragraph (d) of this AD as “the cognizant Principal Maintenance Inspector (PMI).”

Note 4:

Where there are differences between Boeing Alert Service Bulletin 737-28A1132 and this AD, the AD prevails.

Deactivation of Float Switch: Dispatch

(e) Dispatch with the center fuel tank float switch deactivated, in accordance with Boeing Alert Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, dated June 17, 1999; is allowed until replacement float switches and wiring are available for installation or until the compliance time for the replacement required by paragraph (h) of this AD. Where there are differences between the Master Minimum Equipment List (MMEL) and the AD, the AD prevails. Start Printed Page 34847

New Requirements of this AD

Compliance Time for Initial Action for Model 737-200C Series Airplanes

(f) For Model 737-200C series airplanes having L/Ns 1 through 3108 inclusive: Prior to the accumulation of 30,000 total flight hours, or within 30 days after the effective date of this AD, whichever occurs later, accomplish the requirements of paragraph (b) or (c) of this AD. (If the actions specified in paragraph (b) or (c) of this AD have been accomplished before the effective date of this AD, no further action is required by this paragraph.) If the actions required by paragraph (h) of this AD are accomplished within the compliance time specified in this paragraph, operators are not required to do paragraph (b) or (c) of this AD.

Replacement of Conduit

(g) For airplanes having L/Ns 1 through 3108 inclusive, on which the inspection required by paragraph (b)(3)(ii) of this AD has been accomplished prior to the effective date of this AD, and on which replacement of conduit specified in paragraph (b)(3)(ii)(B) has NOT been accomplished: Within 1,500 flight hours or 6 months after the effective date of this AD, whichever occurs first, replace, with new conduit, any section of the electrical conduit where arcing or a leak occurred, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1132, Revision 2, dated June 17, 1999. Such replacement of the conduit constitutes terminating action for the repetitive inspection requirements of paragraph (b)(3)(ii)(A) of this AD.

Replacement of Center and Wing Tank Float Switches

(h) Within 2 years after the effective date of this AD, accomplish paragraphs (h)(1) and (h)(2) of this AD, as applicable. Except as provided by paragraph (j) of this AD, accomplishment of the actions in paragraphs (h)(1) and (h)(2) of this AD, as applicable, terminates the requirements of this AD.

(1) For all airplanes: In the center fuel tank, replace the existing float switches with new, improved float switches, and install a conduit liner system; and in the wing fuel tanks, replace the existing float switches and conduit assemblies with new, improved float switches and conduit assemblies that include a liner system inside the conduit. Do these replacements in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1141, Revision 1, dated December 19, 2002.

(2) For airplanes subject to the repetitive inspections required by paragraph (b)(3)(ii)(A) of this AD, on which the electrical conduit in the center fuel tank has not been replaced as specified in paragraph (b)(3)(ii)(B) or (g) of this AD: Prior to or concurrently with the replacement of the float switch in the center fuel tank required by paragraph (h)(1) of this AD, replace, with new conduit, any section of the center fuel tank electrical conduit where arcing or a leak occurred, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1132, Revision 2, dated June 17, 1999. Such replacement constitutes terminating action for the repetitive inspection requirements of paragraph (b)(3)(ii)(A) of this AD.

Credit for Previously Accomplished Actions

(i) Replacement of float switches and conduit assemblies, and installations of conduit liner systems, as applicable, accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 737-28A1141, dated September 5, 2002, are considered acceptable for compliance with the corresponding action specified in this AD.

Parts Installation

(j) As of the effective date of this AD, no person may install a float switch having part number F8300-146 on any airplane.

Alternative Method of Compliance

(k)(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, Seattle Aircraft Certification Office (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, Seattle ACO.

(2) Alternative methods of compliance, approved previously in accordance with AD 99-05-12, amendment 39-11060, are approved as alternative methods of compliance with the corresponding requirements of this AD.

Note 5:

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

Special Flight Permits

(l) 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.

Start Signature

Issued in Renton, Washington, on June 5, 2003.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 03-14666 Filed 6-10-03; 8:45 am]

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