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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.

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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 Boeing Model 737 series airplanes, that currently requires repetitive inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found. That amendment also requires modification of the fuselage lap joints at certain locations, which constitutes terminating action for repetitive inspections of the modified areas. This proposed action would add repetitive inspections and would require replacement of the current preventive modification with an improved modification. This proposal is prompted by the FAA's determination that, in light of additional crack findings, certain modifications of the fuselage lap joints do not provide an adequate level of safety. The actions specified by the proposed AD are intended to find and fix cracking of the fuselage lap joints, which could result in sudden decompression of the airplane.

DATES:

Comments must be received by August 27, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-196-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 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. 98-NM-196-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, P.O. 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:

Scott Fung, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office (ACO), 1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-1221; fax (425) 227-1181.

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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 98-NM-196-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. 98-NM-196-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On October 21, 1997, the FAA issued AD 97-22-07, amendment 39-10179 (62 FR 55732, October 28, 1997), applicable to certain Boeing Model 737 series airplanes, to require repetitive inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found. That action also adds a requirement for modification of the fuselage lap joints at certain locations, which constitutes terminating action for repetitive inspections of the modified areas. That action was prompted by reports of numerous fatigue cracks in the lower skin of the fuselage lap joints at the lower row of fasteners. The requirements of that AD are intended to prevent such fatigue cracking, which could result in sudden decompression of the airplane.

Actions Since Issuance of Previous Rule

Since the issuance of AD 97-22-07, the FAA has received additional reports of fatigue cracking in the lower skin of the lap joints of the fuselage on Model 737 series airplanes that had accumulated between 57,000 and 84,400 flight cycles, and were previously inspected per that AD. Further investigation revealed additional cracking in various areas of the skin lap joints at the fastener locations that initiated away from the edge of the fastener hole in multiple locations. The majority of these cracks occurred at left and right stringers 4, 10, and 14. The Start Printed Page 36510FAA finds that this damage can occur at those stringer locations between 40,000 and 50,000 flight cycles. These cracks are not always detectable using the open hole eddy current inspection procedures and can link up with adjacent cracks causing multiple site damage. In addition, cracking has been found in the window corners adjacent to the lap joints on certain airplanes.

Based on these findings, the FAA has determined that the current inspection procedures specified in AD 97-22-07 are not adequate for detection of cracks in these locations, and that the preventive change that was required by that AD does not guarantee crack removal. Therefore, the FAA finds that additional rulemaking is necessary to require additional inspections for cracking, removal of the preventive change, and accomplishment of a lap joint modification.

Public Meeting

A joint Federal Aviation Administration (FAA) and Boeing meeting was held on July 25-27, 2000, to inform industry of the activity on Boeing Model 727 and 737 fuselage lap joints. Others in attendance were representatives from air carriers and repair stations, as well as Principal Maintenance Inspectors (PMI) from FAA's Flight Standards Service. The objective of the meeting was to provide an overview of the FAA rulemaking process; discuss the recommendations of Boeing Service Bulletins 727-53A0222 and 737-53A1177, including background information; standardize the 727 and 737 service bulletins, where possible; and discuss the impact that the recommended service bulletin modifications would have on industry.

During the meetings, holders of certain supplemental type certificates presented information pertaining to service bulletin activity for those airplanes that have been modified from a passenger to an all-cargo configuration. The meeting accomplished the objective of exchanging information between the FAA, Boeing, and industry on various aspects of Boeing Models 727 and 737 fuselage lap joints, including compliance planning. As a result of the meeting, attendees recognized the importance of modifying certain lap joints before reaching the point of widespread fatigue damage. Suggestions to improve the service bulletins and clarify AD compliance issues were made by operators and PMIs, and have been incorporated into the service bulletins and the proposed ADs discussed below. In addition, minutes of the public meeting are retained in the docket.

Other Relevant Proposed Rulemaking

At this time, the FAA is considering two other separate rulemaking actions to address the remaining potential unsafe conditions relating to the cracking of the lap joints of the fuselage. Those two other actions would address:

  • Replacement of certain repairs with improved repairs in certain fuselage lap joints done per the procedures described in the structural repair manual (SRM); and a high frequency eddy current inspection to find cracking of the SRM repairs of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found on Model 737 series airplanes, line numbers 292 through 2595 inclusive. And
  • Repetitive inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and a lap joint modification of Model 737-200 and -200C series airplanes, line numbers 1 through 291 inclusive.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001, which describes, among other things, procedures for the following:

  • Removal of the existing preventive modification and the installation of an improved lap joint cutout repair, which eliminates the need for certain repetitive inspections;
  • Repetitive low frequency eddy current (LFEC) inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking;
  • Post-mod inspections, installation of a lap joint repair, and follow-on LFEC inspections;
  • Modification of the tearstrap splice straps; and
  • Repetitive high frequency eddy current inspections of the fastener holes of the window corner of the lap joint area, and repair of any cracking.

The service bulletin also specifies contacting the manufacturer for accomplishment of certain repairs. 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 97-22-07 to continue to require repetitive inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found. This proposed AD would add repetitive inspections, adjust inspection thresholds, and require an improved modification. Accomplishing the improved modification would terminate the inspections required by the existing AD. In addition, this proposed AD would require inspections of some airplanes on which the “Preventive Change” (NACA modification) specified in AD 97-22-07 already had been accomplished. This proposed AD also would require inspections following accomplishment of the improved modifications, and would require tear strap splice conditions for airplanes on which lap joints previously had been repaired per AD 97-22-07. This proposed AD also would require inspections on some airplanes in window corners in areas already being inspected per AD 91-07-04, amendment 39-6933 (56 FR 11355, March 18, 1991), on other airplanes. The actions would be required to be accomplished per the service bulletin described previously, except as discussed below.

Differences Between Service Bulletin and Proposed Rule

The FAA recognizes that the lap joint modification specified in this proposed AD would require jacking, shoring, removing interior components, and modifying certain lap joints, which would require taking the airplane out of service for as much as 22 days. This lengthy shop visit, as well as the relatively short compliance time required to accomplish this proposed AD, make it necessary for operators to engage in compliance planning to ensure that, when the deadline for compliance arrives, all of the required actions have been completed on all affected airplanes. Therefore, paragraph (f) of this proposed AD would require that operators submit to the FAA a compliance plan within 3 months after the effective date of this AD. This will enable the FAA to verify that all operators will be able to meet the deadlines imposed by this proposed AD.

Operators also should note that, in light of the complexity of the service bulletin, three separate rulemaking actions are being issued to address the potential unsafe conditions relating to the cracking of the lap joints of the fuselage. This proposed rule will address only Model 737 series airplanes having line numbers (L/N) 292 through 2565 inclusive. Start Printed Page 36511

Paragraph (m) of this AD addresses only Model 737 series airplanes having L/N 520 through 2565 inclusive for accomplishment of the HFEC inspection to find cracking of the window corner fastener holes. Model 737 series airplanes having L/N 1 through 519 inclusive were addressed in AD 91-07-04, amendment 39-6933. That AD requires ultrasonic and high frequency eddy current inspections for delamination of window belt skin doubler from fuselage skin.

In addition, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair/modification conditions, this proposed AD requires the repair/modification of those conditions to be done per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Cost Impact

There are approximately 2,203 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 905 airplanes of U.S. registry would be affected by this proposed AD.

Cost estimates for the actions required by this proposed AD for U.S. operators over the life of the AD are included in the following table:

Paragraph/AD actionNumber affectedWork HoursParts ($)Cost/airplane ($)Total cost ($)
(a) Lap joint inspection90510006,0005,430,000
(f) Compliance planning9052401,4401,303,200
(g) Lap joint modification9054,20012,000264,000238,920,000
(h) Lap joint inspection90510006,0005,430,000
(i) Post-NACA inspection2510006,000150,000
(j) Post-NACA inspection1010006,00060,000
(m) Window corner inspection807140840677,880

The cost estimates are based on the following criteria:

  • Lap joint inspection cost estimates reflect costs for a single inspection cycle, and the work hours vary between groups of airplanes. Refer to paragraph 1.G. of Boeing Service Bulletin 737-53A1177 for more detailed information. An average of 100 work hours was used in determining the cost estimates.
  • An average of 24 work hours was used in estimating the costs for compliance planning.
  • Lap joint modification work hours vary between groups of airplanes. Refer to paragraph 1.G of Boeing Service Bulletin 737-53A1177 for more detailed information. An average of 4,200 work hours and $12,000 for parts were used in estimating these costs. Modification costs are spread over the estimated life of the AD, which is approximately 20 to 25 years.
  • Window corner inspection work hours vary between groups of airplanes. Refer to paragraph 1.G of Boeing Service Bulletin 737-53A1177 for more detailed information. An average of 14 work hours was used in estimating the costs of the inspections only.

The FAA estimates that during the 10-year period after issuance of the proposed AD, worldwide operators would be required to modify 805 Model 737 series airplanes. The new modification required by the proposed AD would take an average of approximately 4,200 work hours to accomplish, at an average labor rate of $60 per work hour. The worldwide cost impact of the required modification is estimated to be $212,701,000 over 10 years, or an average of $21,270,000 per year. The highest impact year is the third year after issuance of the AD: an estimated 155 Model 737 series airplanes would require modification in that year. Therefore, the worldwide cost impact of the modification is estimated to be $40,955,000 in that year. The affected Model 737 airplanes operated by U.S. operators comprise approximately 41 percent of the total worldwide costs. Therefore, the highest cost impact in any given year for the modifications is estimated to be $16,791,000 for U.S. operators.

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 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 39-10179 (62 FR 55732, October 28, 1997), and by adding Start Printed Page 36512a new airworthiness directive (AD), to read as follows:

Boeing: Docket 98-NM-196-AD. Supersedes AD 97-22-07, amendment 39-10179.

Applicability: Model 737-200, -200C, -300, -400, and -500 series airplanes having line numbers 292 through 2565 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 per paragraph (n) 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 find and fix cracking of certain fuselage lapjoints, which could result in sudden decompression of the airplane, accomplish the following:

Repetitive Low Frequency Eddy Current (LFEC) Inspections—Crown Areas

(a) Do an LFEC inspection to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, per PART I (“Inspection”) of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001; at the time specified in paragraph (b) or (c) of this AD, as applicable.

(b) For airplanes that have accumulated more than 65,000 total flight cycles but not more than 70,000 total flight cycles as of the effective date of this AD: Do the inspection at the earlier of the times specified in paragraphs (b)(1) and (b)(2) of this AD. Repeat the inspection after that at intervals not to exceed 1,200 flight cycles until accomplishment of the lap joint repair required by paragraph (g) of this AD.

(1) Within 1,200 flight cycles after the effective date of this AD.

(2) Within 1,200 flight cycles after the last inspection, if any, accomplished in accordance with AD 97-22-07, amendment 39-10179.

(c) For airplanes that have accumulated at least 45,000 total flight cycles but not more than 65,000 total flight cycles as of the effective date of this AD: Do the inspection at the earlier of the times specified in paragraphs (c)(1) and (c)(2) of this AD. Repeat the inspection after that at intervals not to exceed 1,200 flight cycles until accomplishment of the lap joint repair required by paragraph (g) of this AD.

(1) At the later of the times specified in paragraphs (c)(1)(i) and (c)(1)(ii) of this AD.

(i) Before the accumulation of 50,000 total flight cycles.

(ii) Within 1,200 flight cycles after the effective date of this AD.

(2) Within 1,200 flight cycles after the last inspection, if any, accomplished in accordance with AD 97-22-07, amendment 39-10179.

Crack Repair

(d) Except as provided by paragraph (e) of this AD: If any cracking is found during any inspection required by this AD, before further flight, repair per PART II (“Crack Repair”) of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001.

(e) If any cracking is found during any inspection required by this AD, and Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001, specifies to contact Boeing for repair instructions: Repair any cracking, before further flight, per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

Compliance Plan

(f) Within 3 months after the effective date of this AD, submit a plan to the FAA identifying a schedule for compliance with paragraph (g) of this AD. This schedule must include, for each of the operator's affected airplanes, the dates and maintenance events (e.g., letter checks) when the required actions will be accomplished. For the purposes of this paragraph, “FAA” means the Principal Maintenance Inspector (PMI) for operators that are assigned a PMI, or the cognizant Flight Standards District Office for other operators. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.

Note 2:

Operators are not required to submit revisions to the compliance plan required by paragraph (f) of this AD to the FAA.

Lap Joint Modification (Repair)—Crown Areas

(g) Install the lap joint repair per PART III or IV (“Lap Joint Repair”) of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001, as applicable; at the time specified in paragraph (g)(1), (g)(2), (g)(3), (g)(4), or (g)(5) of this AD, as applicable. Accomplishment of this repair terminates the repetitive inspections required by paragraphs (b) and (c) of this AD.

(1) For airplanes that have accumulated 70,000 total flight cycles or more as of the effective date of this AD: Within 600 flight cycles after the effective date of this AD, do the lap joint repair.

(2) For airplanes that have accumulated 65,000 total flight cycles or more, but less than 70,000 total flight cycles as of the effective date of this AD: Do the repair at the later of the times specified in paragraphs (g)(2)(i) and (g)(2)(ii) of this AD.

(i) Before the accumulation of 70,000 total flight cycles.

(ii) Within 600 flight cycles after the effective date of this AD.

(3) For airplanes that have accumulated 45,000 total flight cycles or more, but less than 65,000 total flight cycles as of the effective date of this AD: Within 5,000 flight cycles after the effective date of this AD.

(4) For airplanes that have accumulated less than 45,000 total flight cycles as of the effective date of this AD: Before the accumulation of 50,000 total flight cycles.

(5) Notwithstanding the times specified in paragraphs (g)(1), (g)(2), (g)(3), and (g)(4) of this AD, for airplanes on which the “Preventive Change” has been accomplished per PART III of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1177, Revision 3, dated September 18, 1997; (NACA modification): Within 18,000 flight cycles after accomplishment of the NACA modification.

Repetitive LFEC Inspections—Outside Crown Areas

(h) Before the accumulation of 70,000 total flight cycles, or within 2,500 flight cycles after the effective date of this AD, whichever comes later: Perform an LFEC inspection to find cracking of the lap joints of the fuselage; as identified in Figures 2 through 7 of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001. Do the inspection per the service bulletin. Repeat the inspection after that at intervals not to exceed 5,000 flight cycles.

Post-NACA Modification Inspections—Crown Areas

(i) For airplanes that have the “Preventive Change” (NACA modification) of the crown lap joint stringers (“Crown Laps”): Within 12,000 flight cycles after accomplishment of the NACA modification, do either an external (Figure 8) or internal (Figure 9) LFEC inspection to find cracking and corrosion per PART I (“Inspection”) of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001.

(1) If the external inspection is done: Repeat the inspection after that at intervals not to exceed 1,500 flight cycles until accomplishment of the lap joint repair required by paragraph (g) of this AD.

(2) If the internal inspection is done: Repeat the inspection after that at intervals not to exceed 4,500 flight cycles until accomplishment of the lap joint repair required by paragraph (g) of this AD.

Post-NACA Modification Inspection—Outside Crown Areas

(j) For airplanes that have the “Preventive Change” (NACA modification) outside the crown areas: Before the accumulation of 20,000 flight cycles after accomplishment of the NACA modification, do either an external (Figure 8) or internal (Figure 9) LFEC inspection to find cracking and corrosion per PART I (“Inspection”) of the Accomplishment Instructions of Boeing Start Printed Page 36513Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001.

(1) If the external inspection is done: Repeat the external inspection after that at intervals not to exceed 1,500 flight cycles.

(2) If the internal inspection is done: Repeat the internal inspection after that at intervals not to exceed 4,500 flight cycles.

Modification of Tear Strap Splice Straps

(k) For airplanes that have the “lap joint repair,” as specified in Part IV of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 2, dated July 24, 1997, or Revision 3, dated September 18, 1997: Within 45,000 flight cycles after accomplishment of this lap joint repair, modify the splice straps per Figures 10, 11, and 12 of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001.

Follow-On LFEC Inspections

(l) Within 45,000 flight cycles after accomplishment of the lap joint repair required by paragraph (g) of this AD: Do either an external (Figure 8) or internal (Figure 9) LFEC inspection to find cracking of the lap joint repair, per PART I (“Inspection”) of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001. Repeat the inspection after that at intervals not to exceed 2,800 flight cycles.

Repetitive High Frequency Eddy Current (HFEC) Inspections—Window Corners

(m) For airplanes having line numbers 520 through 2565 inclusive: Before the accumulation of 50,000 total flight cycles or within 1,200 flight cycles after the effective date of this AD, whichever comes later, do a HFEC inspection to find cracking, per PART V (“Window Corner Fastener Hole Cracking, Inspection and Repair”) of the Accomplishment Instructions of Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001. Repeat the inspection after that at intervals not to exceed 4,500 flight cycles. Accomplishment of the modification per Part V of the Accomplishment Instructions of the service bulletin constitutes terminating action for the inspections required by this paragraph.

Alternative Methods of Compliance

(n) 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 ACO. Operators shall submit their requests through an appropriate FAA PMI, who may add comments and then send it to the Manager, Seattle ACO.

Note 3:

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

(o) Special flight permits may be issued per 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 July 6, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 01-17431 Filed 7-11-01; 8:45 am]

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