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Proposed Rule

Airworthiness Directives; Boeing Model 737-100, -200, and -200C Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

Start Preamble

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.

SUMMARY:

This document revises an earlier NPRM, applicable to all Boeing Model 737-100, -200, and -200C series airplanes. The original NPRM would have required repetitive inspections to detect discrepancies of certain fuselage skin panels located just aft of the wheel well, and repair if necessary. The original NPRM was prompted by reports of fatigue cracking of the skins and doublers located aft of the wing, between body station (BS) 727 and BS 1016, and between body stringers 14 and 25. This supplemental NPRM revises the original NPRM by adding requirements for certain airplanes, revising the compliance time for inspection of modified skin areas, and allowing alternative service information for certain actions. The actions specified by this new supplemental NPRM are intended to detect and correct fatigue cracking of the skin panels, which could cause rapid decompression of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by April 26, 2005.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-289-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. 2002-NM-289-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.

For the service information referenced in the proposed rule, contact 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:

Suzanne Lucier, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6438; 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 Start Printed Page 16762proposal 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 2002-NM-289-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-289-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 all Boeing Model 737-100, -200, and -200C series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on January 7, 2004 (69 FR 897). That NPRM would have required repetitive inspections to detect discrepancies of certain fuselage skin panels located just aft of the wheel well, and repair if necessary. That NPRM was prompted by reports of fatigue cracking of the skins and doublers located aft of the wing, between body station (BS) 727 and BS 1016, and between body stringers 14 and 25, on numerous Boeing Model 737-100, -200, and -200C series airplanes. The cracking has been attributed to fatigue from a combination of shear stresses due to repeated wrinkling of the skin, and the skin chem-milled pockets configuration. Such fatigue cracking, if not corrected, could cause rapid decompression of the airplane.

Actions Since Original NPRM Was Issued

Due consideration has been given to the comments received in response to the original NPRM.

Request To Revise Inspection References

Paragraph (b) of the original NPRM refers to Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001, for conditions associated with the inspection requirements. One commenter (the manufacturer) requests that we revise that service bulletin reference to include earlier revision levels. The manufacturer recommends that we require inspections of all previously modified airplanes having stiffening angles—regardless of the service bulletin revision used.

We agree that (stiffener) modifications for airplanes modified in accordance with the original issue and Revision 1 of the service bulletin should also be inspected. Excluding these earlier service bulletin versions was an oversight in the development of the original NPRM. We have revised paragraphs (b) and (c) of this supplemental NPRM accordingly.

Request To Revise Compliance Time

The manufacturer requests that we revise paragraph (b) of the original NPRM (inspection of modified skin areas) to also change the compliance time: from 16,000 flight cycles after the modification to 16,000 total accumulated flight cycles. Post-modification cracks have been found in service, which the manufacturer believes existed when the modification was installed but were visually undetectable at the time. The modification with the stiffening angles is designed to prevent shear wrinkling by breaking up the bay into smaller dimensions. These angles do not reduce the hoop stress in the areas where the cracks typically exist. As a result, cracks that exist when the modification is installed will continue to propagate under hoop loading and may grow to a significant length before the airplane accumulates an additional 16,000 flight cycles after the modification. The manufacturer concludes that the compliance time for the initial inspection of modified areas should be based on the total accumulated flight cycles, and not the flight cycles accumulated since the modification.

We agree. We have revised the compliance time in paragraph (b) of this supplemental NPRM accordingly.

Conclusion

Since these changes expand the scope of the original NPRM, we have determined that it is necessary to reopen the comment period to provide additional opportunity for public comment. Additional comments on the original NPRM are addressed below.

Request To Allow Additional Repair Information

Two commenters request that we revise the original NPRM to include the Boeing 737 Structural Repair Manual (SRM) as an acceptable source of service information for compliance with the repair requirements specified in paragraphs (d)(1)(iii) and (d)(2). The commenters state that, since Boeing issued Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001 (cited in the original NPRM), the SRM has been revised to include repair procedures for skin cracks. The repairs in Section 53-30-3, Figure 48, of the SRM apply to most of the areas covered by the original NPRM. The commenters note that Figure 48 of the SRM is an FAA-approved repair for this type of damage; allowing this optional repair in the original NPRM will reduce the number of repair inquiries from operators. Therefore, the commenters request that crack repairs in accordance with the SRM also be allowed in paragraphs (d)(1)(iii) and (d)(2) of the original NPRM.

We agree with the commenters' request and have changed paragraphs (d)(1)(iii) and (d)(2) accordingly in this supplemental NPRM.

Request To Clarify Requirement

One commenter, the manufacturer, states that cracks underneath external repair doublers (installed for repairs unrelated to the requirements specified in this proposed AD) have been found in service. The commenter requests that we revise paragraphs (a) and (c) of the original NPRM to also address inspections of chemical-milled steps underneath external repair doublers. Undetected cracks that are not sufficiently spanned by a repair doubler could propagate undetected. The commenter suggests that an FAA-approved repair with three rows of fasteners on each side of the chemical-milled step would be adequate to maintain ultimate load capability even if undetected cracks develop underneath the repair.

We agree with the request. External repair doublers impede the ability to inspect the exterior of fuselage side skins. The commenter's suggested change would provide adequate inspection procedures for the skin under the repair doublers. We find the commenter's suggestion satisfactory and have included new paragraph (g) of this supplemental NPRM to provide inspection procedures for those airplanes as one method of compliance with the requirements of paragraphs (a) and (c) of this supplemental NPRM.

Request To Limit Repetitive Inspections

This same commenter requests that we revise the repetitive inspection requirement specified in paragraph (d)(1)(ii) of the original NPRM to a one-time-only inspection after the time-limited repair has been done, as specified in the service bulletin.

We agree with the request. Eliminating the repetitive inspections will not compromise safety. We have changed paragraph (d)(1)(ii) in this Start Printed Page 16763supplemental NPRM to correspond to the compliance times of Service Bulletin 737-53-1065.

Changes to 14 CFR Part 39/Effect on Supplemental NPRM

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 directives system. The regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance (AMOCs). These changes are reflected in this supplemental NPRM.

Explanation of Additional Changes to Supplemental NPRM

Boeing has received a Delegation Option Authorization (DOA). We have revised paragraph (e) of this supplemental NPRM to allow any discrepancy, including cracking, to be repaired according to data that conform to the airplane's type certificate and that are approved by an Authorized Representative for the Boeing DOA Organization (rather than the Designated Engineering Representative (DER)) whom we have authorized to make such findings.

We have also revised paragraph (h)(2) of this supplemental NPRM to delegate the authority to approve an alternative method of compliance for any repair required by the AD to the Authorized Representative for the Boeing DOA Organization rather than the DER.

Interim Action

This is considered to be interim action. The manufacturer has advised that it is developing an improved preventive modification intended to address the identified unsafe condition for unmodified skin areas. After this modification is developed, approved, and available, we may consider additional rulemaking.

Cost Impact

There are about 1,000 airplanes of the affected design in the worldwide fleet. The FAA estimates that 390 airplanes of U.S. registry would be affected by this supplemental NPRM.

The inspection would take about 47 to 88 work hours per airplane (depending on configuration), at an average labor rate of $65 per work hour. Based on these figures, we estimate the cost of the inspection to be $3,055 to $5,720 per airplane, per inspection cycle.

The cost impact figure discussed above is 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.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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.

Start List of Subjects

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:

Start Authority

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

End Authority
[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2002-NM-289-AD.

Applicability: All Model 737-100, -200, and -200C series airplanes; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To detect and correct fatigue cracking of the skin panels, which could cause rapid decompression of the airplane, accomplish the following:

Repetitive Inspections: Unmodified Skin Areas

(a) For fuselage skin panel areas that have not been modified with stiffening angles: Before the airplane accumulates 16,000 total flight cycles, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later, inspect the unmodified fuselage side skins just aft of the main wheelwell, and perform all follow-on actions, in accordance with Part I of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001; except as provided by paragraph (g) of this AD. If no cracking, loose fasteners, disbonding, or damage is found: Repeat the inspection at the time specified in paragraph 1.E., Compliance, of the service bulletin, as applicable, except as provided by paragraph (d) of this AD.

Repetitive Inspections: Modified Skin Areas

(b) For fuselage skin panel areas that have been modified with stiffening angles in accordance with Boeing Service Bulletin 737-53-1065, dated January 4, 1985; Revision 1, dated October 12, 1989; or Revision 2, dated April 19, 2001: Before the airplane accumulates 16,000 total flight cycles, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later, inspect the modified areas as specified in accordance with Part I of Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001. Repeat the inspection at the time specified in paragraph 1.E., of the service bulletin, as applicable, except as provided by paragraph (d) of this AD. If any cracks, loose fasteners, disbonding, or Start Printed Page 16764damage is found: Repair before further flight in accordance with the requirements of paragraph (d) of this AD.

Terminating Action for Inspections of Modified Skin Areas

(c) For fuselage skin panel areas that have been modified with stiffening angles in accordance with Boeing Service Bulletin 737-53-1065, dated January 4, 1985; Revision 1, dated October 12, 1989; or Revision 2, dated April 19, 2001: At the later of the times specified by paragraphs (c)(1) and (c)(2) of this AD, perform a subsurface eddy current or magneto optical imaging inspection to detect subsurface skin cracks along the edge of the bonded doubler, in accordance with Figure 10 of Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001; except as provided by paragraph (g) of this AD. If any cracks are found, repair before further flight in accordance with paragraph (d) of this AD. Accomplishment of this inspection and all applicable corrective actions terminates the repetitive inspections required by paragraph (b) of this AD for the modified areas.

(1) Inspect within 24,500, but not fewer than 20,000, flight cycles after the modification of the skin.

(2) Inspect within 4,500 flight cycles after the effective date of this AD.

Repair: Modified and Unmodified Skin Areas

(d) If any cracking is detected during any inspection required by this AD: Do the actions specified by paragraph (d)(1) or (d)(2) of this AD before further flight. Do the actions in accordance with Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001, except as required by paragraph (e) of this AD.

(1) Do a time-limited repair (including a detailed inspection of the skin in the area of the repair to detect corrosion and doubler disbonding) in accordance with Part III of the Accomplishment Instructions of the service bulletin.

(i) After the time-limited repair has been accomplished: At intervals not to exceed 3,000 flight cycles, perform an external general visual inspection of the repair to detect loose or missing fasteners, in accordance with Part III of the Accomplishment Instructions of the service bulletin, until the actions specified in paragraph (d)(1)(v) of this AD have been accomplished.

(ii) Within 4,500 flight cycles after the time-limited repair has been accomplished: Perform an internal inspection of the repair to detect cracking or doubler disbonding using general visual and high-frequency eddy current methods, in accordance with Figure 11 of the service bulletin, unless the actions specified in paragraph (d)(1)(v) of this AD have been accomplished.

(iii) If any cracking is found during any inspection required by paragraph (d)(1) of this AD: Repair before further flight in accordance with paragraph (e) of this AD. Another approved repair method is in Section 53-30-3, Figure 48, of the Boeing 737 Structural Repair Manual (SRM).

(iv) If any disbonding is found during any inspection required by paragraph (d)(1) of this AD: Repair before further flight in accordance with Part II of the service bulletin.

(v) Within 10,000 flight cycles after accomplishment of the time-limited repair: Make the repair permanent in accordance with Part III of the Accomplishment Instructions of the service bulletin. Permanent repair of an area terminates the repetitive inspections specified in this AD for that repaired area only.

(2) Do a permanent repair (including an inspection using external subsurface eddy current or magneto optical imaging methods to detect cracks at the chem-milled step in each adjacent bay of the fuselage skin, a detailed inspection of the skin in the area of the repair for corrosion and doubler disbonding, and applicable corrective action) of the cracked area, in accordance with Part II of the Accomplishment Instructions of the service bulletin. Another approved repair method is in Section 53-30-3, Figure 48, of the Boeing 737 Structural Repair Manual (SRM). Permanent repair of an area terminates the repetitive inspections specified in this AD for that repaired area only.

Exceptions to Service Bulletin Procedures

(e) During any inspection required by this AD, if any discrepancy (including cracking) is detected for which the service bulletin specifies to contact Boeing for appropriation action: Before further flight, repair according to a method approved by the Manager, Seattle Aircraft Certification Office (ACO); or according to data meeting the certification basis of the airplane approved by an Authorized Representative for the Boeing Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the approval must specifically refer to this AD.

(f) Although Boeing Service Bulletin 737-53-1065, Revision 2, dated April 19, 2001, recommends that cracks found in Zone 2 be reported to Boeing, this AD does not require such a report.

(g) For airplanes subject to the requirements of paragraphs (a) and (c) of this AD: Inspections are not required in areas that are spanned by an FAA-approved repair that has a minimum of 3 rows of fasteners above and below the chemical-milled step. If an external doubler covers the chemical-milled step, but does not span it by a minimum of 3 rows of fasteners above and below, one method of compliance with the inspection requirement of paragraphs (a) and (c) of this AD is to inspect all chemical-milled steps covered by the repair using internal nondestructive test (NDT) methods in accordance with Part 6, Subject 53-30-20, of the Boeing 737 NDT Manual. Follow-on and corrective actions must be done as specified in this AD.

Alternative Methods of Compliance (AMOCs)

(h)(1) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, FAA, is authorized to approve AMOCs for this AD.

(2) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the approval must specifically refer to this AD.

Start Signature

Issued in Renton, Washington, on March 22, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 05-6451 Filed 3-31-05; 8:45 am]

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