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Proposed Rule

Airworthiness Directives; Boeing Model 737-100 and -200 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.

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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airworthiness directive (AD), applicable to certain Boeing Model 737-100 and -200 series airplanes, that would have superseded an existing AD that currently requires various inspections for cracks in the outboard chord of the frame at body station (BS) 727 and in the outboard chord of stringer 18A; and repair or replacement of cracked parts. The proposed AD also would have required additional inspections for certain airplanes, and would have revised certain compliance times for all airplanes. That proposed AD was prompted by reports of fatigue cracks in those outboard chords. This new action revises the proposed AD by reducing the proposed initial inspection compliance times; simplifying and clarifying the repetitive inspection compliance times; and adding airplanes to the applicability. The actions specified by this new proposed AD are intended to detect and correct fatigue cracking, which could result in reduced structural integrity of the outboard chords, and consequent rapid decompression of the airplane.

DATES:

Comments must be received by August 24, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 95-NM-215-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. 95-NM-215-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, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-1221; fax (206) 227-1181.

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 95-NM-215-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. 95-NM-215-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 and -200 series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on January 7, 1997 (62 FR 945). That NPRM proposed to supersede AD 95-12-17, amendment 39-9268 (60 FR 36981, July 19, 1995), which is applicable to certain Boeing Model 737-100 and -200 series airplanes. That NPRM would have continued to require various inspections for cracks in the outboard chord of the frame at body station (BS) 727 and in the outboard chord of stringer 18A; and repair or replacement of cracked parts. That NPRM would have required additional inspections for certain airplanes, and would have revised certain compliance times for all airplanes. That NPRM was prompted by reports of fatigue cracks in the outboard chords. That condition, if not corrected, could result in reduced structural integrity of the outboard chords, and consequent rapid decompression of the airplane.Start Printed Page 35913

Comments

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

No Objection to the Proposed Rule

Two commenters, both airline operators, advised that they did not have any objections to the proposed rule.

Request To Reduce the Threshold

One commenter, the manufacturer, requests that the initial threshold compliance time for the proposed rule be changed from “prior to 50,000 total flight cycles” to “prior to 35,000 total flight cycles.” The commenter states that fleet data reviewed since the release of Boeing 737 Service Bulletin 737-53A1166 (the applicable service information specified in the proposed rule) shows that small cracks have been detected as early as 28,000 flight cycles. The commenter suggests that if there are no cracks found, the next inspection should be accomplished at 50,000 total flight cycles. The commenter states that the repetitive intervals of 4,500 flight cycles as specified in the proposed rule should be retained.

The FAA partially agrees. For the reason the commenter stated, we concur that the threshold compliance time of paragraph (a) of the proposed rule should be reduced. However, based on the new reports of cracks, we have determined that the compliance time should be reduced to “prior to the accumulation of 30,000 total flight cycles,” and have revised this supplemental NPRM accordingly. This has the effect of retaining the initial compliance time specified in AD 95-12-17. We do not concur that, if no cracks are found, the next inspection should be accomplished only prior to 50,000 total flight cycles. Based on the new crack data that Boeing has provided, we find that, if there are no cracks found during an initial inspection that is performed prior to 30,000 total flight cycles, waiting to perform the next inspection until 50,000 total flight cycles are accumulated could allow sufficient and ample time for cracking to develop. Therefore, we have determined that the previously proposed repetitive inspection interval of 4,500 flight cycles should remain the same throughout this supplemental NPRM.

Additional Changes to the NPRM

Since the issuance of the original NPRM, the FAA has determined that a new group of airplanes (i.e., for airplanes that have accumulated less than 27,000 total flight cycles) were inadvertently excluded in the original NPRM. Therefore, that group of airplanes has been included and addressed in paragraph (c) of this supplemental NPRM.

Also, we have determined that the various repetitive inspection times specified in the original NPRM should be combined into a single repetitive interval not to exceed 4,500 flight cycles. That single repetitive compliance time will continue to provide an adequate level of safety and should make it simpler and easier for operators to schedule their fleets for required maintenance.

Conclusion

Since these changes expand the scope of the originally proposed rule, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Cost Impact

There are approximately 999 Model 737-100 and -200 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 296 airplanes of U.S. registry would be affected by this proposed AD.

The actions that are currently required by AD 95-12-17 take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the actions currently required is estimated to be $71,040, or $240 per airplane, per inspection cycle.

This proposed AD specifies inspection requirements for airplanes that were omitted inadvertently from the existing AD. However, the costs associated with the inspections for those airplanes were included previously in the cost impact on U.S. operators for accomplishment of AD 95-12-17. Therefore, the FAA estimates that no additional costs would be required for accomplishment of the proposed requirements of this AD for those airplanes.

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.

Should an operator elect to accomplish the optional terminating action that would be provided by this proposed AD, it would take approximately 50 work hours to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $3,680 per airplane. Based on these figures, the cost impact of this optional terminating action is estimated to be $6,680 per airplane.

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

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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:

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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 39-9268 (60 FR 36981, July 19, 1995), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 95-NM-215-AD. Supersedes AD 95-12-17, Amendment 39-9268.

Applicability: Model 737-100 and -200 series airplanes, line numbers 1 through 999 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 Start Printed Page 35914airplanes 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 (g) 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 detect and correct fatigue cracking, which could result in reduced structural integrity of the outboard chords, and consequent rapid decompression of the airplane., accomplish the following:

Restatement of AD 95-12-17

Inspections of the Outboard Chord

(a) For airplanes on which the body station (BS) 727 frame upper outboard chord has been replaced in accordance with Boeing Service Bulletin 737-53-1088: Prior to the accumulation of 30,000 total flight cycles since replacement of the upper outboard chord, or within 4,500 flight cycles after August 18, 1995, the effective date of AD 95-12-17 (60 FR 36981, July 19, 1995), whichever occurs later, perform close visual, pulse echo shear wave (PESW), and high frequency eddy current (HFEC) inspections to detect cracks in the outboard chord of the frame at BS 727 and in the outboard chord of stringer 18A; in accordance with Part I of the Accomplishment Instructions of either Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994; or Boeing Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995.

Certain Other Inspections

(b) For airplanes on which the BS 727 frame outboard chord has not been replaced or on which only the lower outboard chord has been replaced in accordance with Boeing Service Bulletin 737-53-1088: Perform close visual, PESW, and HFEC inspections to detect cracks in the outboard chord of the frame at BS 727 and in the outboard chord of stringer 18A; in accordance with Part I of the Accomplishment Instructions of either Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994; or Boeing Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995; at the times specified in paragraph (b)(1), (b)(2), (b)(3), (b)(4), or (b)(5) of this AD. Thereafter, repeat the inspections at intervals not to exceed 4,500 flight cycles.

(1) For airplanes that have accumulated 27,000 or more total flight cycles, but fewer than 50,000 total flight cycles, as of August 18, 1995: Perform the inspections within 4,500 flight cycles after August 18, 1995.

(2) For airplanes that have accumulated 50,000 or more total flight cycles, but fewer than 60,000 total flight cycles, as of August 18, 1995: Perform the inspections within 2,500 flight cycles after August 18, 1995.

(3) For airplanes that have accumulated 60,000 or more total flight cycles, as of August 18, 1995: Perform the inspections within 1,500 flight cycles after August 18, 1995.

(4) For airplanes that have accumulated 70,000 or more total flight cycles as of August 18, 1995: Perform the inspections within 500 flight cycles or within 90 days after August 18, 1995.

New Requirements of This AD

(c) For any airplane that had accumulated less than 27,000 total flight cycles as of August 18, 1995 (the effective dated of AD-95-12-17): Within 4,500 flight cycles after the effective date of this AD, perform close visual, pulse echo shear wave (PESW), and high frequency eddy current (HFEC) inspections to detect cracks in the outboard chord of the frame at BS 727 and in the outboard chord of stringer 18A; in accordance with Part I of the Accomplishment Instructions of either Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994; or Boeing Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995. Thereafter, repeat the inspections at intervals not to exceed 4,500 flight cycles.

(d) If any crack is found in the outboard chord of stringer 18A during any inspection required by this AD, prior to further flight, repair in accordance with either paragraph (d)(1) or (d)(2) of this AD.

(1) Repair in accordance with Boeing Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995; or

(2) Repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative 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 Manager's approval letter must specifically reference this AD.

(e) If any crack is found in the outboard chord of the frame at BS 727 during any inspection required by this AD: Accomplish paragraph (e)(1) or (e)(2) of this AD, as applicable, in accordance with either Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994; or Boeing Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995. Thereafter, repeat the inspections required by either paragraph (a) or (b) of this AD, as applicable, at intervals not to exceed 4,500 flight cycles.

(1) If any crack extends from the forward edge of the chord or from the forward fastener hole, but does not extend past the second fastener hole, accomplish either paragraph (e)(1)(i) or (e)(1)(ii) of this AD.

(i) Prior to further flight, install the time-limited repair. Prior to the accumulation of 4,500 flight cycles or within 18 months after accomplishment of the repair, whichever occurs first, replace the outboard chord. Or

(ii) Prior to further flight, replace the outboard chord.

Note 2:

Boeing Alert Service Bulletin 737-53A1166 references Boeing Service Bulletin 737-53-1088 as an additional source of service information for procedures to replace the chord.

(2) If any crack extends from the forward edge of the chord, or from the forward fastener hole, and extends past the second fastener hole, prior to further flight, replace the outboard chord in accordance with either the original issue or Revision 1 of the service bulletin.

(f) Accomplishment of the actions specified in paragraph (f)(1) or (f)(2) of this AD in accordance with either Boeing Alert Service Bulletin 737-53A1166, dated June 30, 1994, or Boeing Service Bulletin 737-53A1166, Revision 1, dated May 25, 1995, constitutes terminating action for the requirements of this AD.

(1) For airplanes on which no crack is found: Install the preventative modification.

(2) For airplanes on which any crack is found: Prior to further flight, replace the cracked chord and install the preventative modification.

Alternative Methods of Compliance

(g) 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 Principal Maintenance Inspector, 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

(h) 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 July 2, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 01-17122 Filed 7-9-01; 8:45 am]

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