Airworthiness Directives; Boeing Model 727 Series Airplanes

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 notice may be changed in light of the comments received. 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 97-NM-323-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. 97-NM-323-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On December 21, 1989, the FAA issued AD 90-02-16, amendment 39-6452 (55 FR 602, January 8, 1980), applicable to certain Boeing Model 727 series airplanes, to require inspection of the front spar web of the center section of the wings, and repair, if necessary. That action was prompted by reports of cracks in the front spar web. The requirements of that AD are intended to detect and correct such cracking, which could lead to fuel leakage and/or depressurization of the cabin.

Actions Since Issuance of Previous Rule

Since issuance of AD 90-02-16, the FAA has received a report indicating that modification procedures specified in Boeing Service Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated November 21, 1991; and Revision 2, dated September 16, 1993; do not adequately address airplanes equipped with internal fuel tanks in the center section of the wings. Specifically, the service bulletin does not include procedures for application of the secondary fuel seal on the forward side of the front spar and on the fillet seals on the aft side of the front spar. The service bulletin also describes procedures for the application of sealant Boeing material specification (BMS) 5-95 inside the fuel tank instead of the fuel-proof sealant BMS 5-26, and the installation of non-fluid tight fasteners instead of fluid tight fasteners. Boeing Service Bulletin 727-57-0177, dated December 22, 1988, was referenced in AD 90-02-16 as the appropriate source of service information for accomplishment of the required modification and close visual and high frequency eddy current (HFEC) inspections. Revisions 1 and 2 of that service bulletin were approved by the FAA as alternative methods of compliance for accomplishment of those actions.

In light of this information, the FAA has determined that the optional modification specified in AD 90-02-16 does not adequately preclude fuel leakage into the air-conditioning distribution bay, which could result in fuel fumes in the cabin of the airplane. In addition, the FAA finds that the subject service bulletin does not contain procedures for accomplishing an HFEC inspection as an option to the close visual inspection, as required by paragraph A. of AD 90-02-16. The actual procedures used to accomplish that HFEC inspection and the effectiveness of those procedures are unknown to the FAA. The FAA has determined that performing an HFEC inspection in accordance with an unknown procedure does not ensure that cracks will be detected in a timely manner. Therefore, the FAA has determined that all affected airplanes must accomplish repetitive detailed visual inspections to ensure that cracks are detected in a timely manner.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 727-57- 0177, Revision 3, dated February 15, 1996, which describes procedures for repetitive detailed visual inspections to detect cracks of the front spar web between the upper and lower seals of the center section of the wings, and repair, if necessary. The service bulletin also describes procedures for modification of the front spar web between the upper and lower seals of the center section of the wings, which would eliminate the need for the repetitive inspections. For certain airplanes, the service bulletin describes procedures for repetitive visual inspections of the front spar web to detect fuel leakage and penetrations in the secondary fuel barrier, and to verify the installation of the secondary fuel barrier. Accomplishment of the actions specified in the service bulletin are 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 90-02-16, amendment 39-6452 (55 FR 602, January 8, 1980), to continue to require repetitive detailed visual inspections of the front spar web between the upper and lower seals of the center section of the wings, and repair, if necessary. The proposed AD also would require modification of the subject front spar web, which would constitute terminating action for the repetitive inspections. For certain airplanes, the proposed AD would require repetitive visual inspections of the front spar web to detect fuel leakage and penetrations in the secondary fuel barrier, and to verify the installation of the secondary fuel barrier. The actions would be required to be accomplished in accordance with the service bulletin described previously; except as discussed below. The FAA has determined that, for airplanes equipped with integral fuel tanks in the center section of the wings, the repairs and modifications specified in Figure 2 and Figure 3 of Boeing Service Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated November 21, 1991; and Revision 2, dated September 16, 1993; do not describe procedures for installation of a fuel proof sealant in these tanks, which could lead to identified unsafe condition of this AD. The procedures specified in the original version, Revision 1, and Revision 2 of the service bulletin are acceptable for airplanes without integral fuel tanks in the center section of the wings. However, the FAA finds that Revision 3 of the subject service bulletin does provide procedures for installation of a fuel proof sealant for integral fuel tanks.

Other Relevant Rulemaking

The FAA has previously issued AD 94-05-04, amendment 39-8842 (59 FR 13442, March 22, 1994), which requires incorporation of certain structural modification on certain Boeing Model 747 series airplanes. Accomplishment of certain actions required by this proposed AD would constitute terminating action for the requirements specified in paragraph (a) of AD 94-05-04 with respect to the modification specified in Boeing Service Bulletin 727-57-0177, dated December 22, 1998. This service bulletin is one of many service bulletins referenced in Boeing Document D6-54860, Revision G, Appendix A.3, dated March 5, 1993. All other service bulletins referenced in that document still apply.

Cost Impact

There are approximately 1,524 Model 727 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,098 airplanes of U.S. registry would be affected by this proposed AD. The detailed visual inspection that is currently required by AD 90- 02-16, and retained in this AD, 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 currently required detailed visual inspection on U.S. operators is estimated to be $197,640, or $180 per airplane, per inspection cycle. The modification that is proposed in this new AD action would take approximately 360 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $1,430 per airplane. Based on these figures, the cost impact of the proposed modification required by this AD on U.S. operators is estimated to be $25,286,940, or $23,030 per airplane. For certain airplanes, the visual inspection that is proposed in this new AD action would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed modification required by this AD on U.S. operators is estimated to be $60 per airplane, per inspection cycle. 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.

Regulatory Impact

The regulations proposed herein would not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. 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.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

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:

PART 39--AIRWORTHINESS DIRECTIVES

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

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

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing amendment 39-6452 (55 FR 602, January 8, 1990), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 97-NM-323-AD. Supersedes AD 90-02-16, Amendment 39- 6452.

Applicability: Model 727 series airplanes, as listed in Boeing Service Bulletin 727-57-0177, dated December 22, 1988; 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 (g)(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 fatigue cracks of the front spar web of the center section of the wings, which could lead to fuel leakage and/or depressurization of the cabin, or to prevent fuel fumes in the cabin of the airplane, accomplish the following:

Repetitive Detailed Visual Inspections

(a) For areas on which the front spar web between the upper and lower seals of the center section of the wings has not been repaired or modified in accordance with Figure 2 or 3 of Boeing Service Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated November 21, 1991; or Revision 2, dated September 16, 1993: Prior to the accumulation of 40,000 total flight cycles, or with the next 2,300 flight cycles after February 12, 1990 (effective date of AD 90-02-16, amendment 39-6452), whichever occurs later, unless accomplished with the last 700 flight cycles, perform a detailed visual inspection to detect cracks in the front spar web, in accordance with Figure 1 of Boeing Service Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated November 21, 1991; Revision 2, dated September 16, 1993; or Revision 3, dated February 15, 1996. Repeat the detailed visual inspection thereafter at intervals not to exceed 3,000 flight cycles, until accomplishment of the requirements specified in either paragraph (b) or (c) of this AD.

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.'' Note 3: Accomplishment of the high frequency eddy current (HFEC) inspection required by AD 90-02-16, is considered acceptable for compliance with the initial detailed visual inspection required by paragraph (a) of this AD.

Repair of Cracks

(b) If any crack is detected during any inspection required by paragraph (a) of this AD, prior to further flight, accomplish the actions specified in either paragraph (b)(1) or (b)(2) of this AD, as applicable. Accomplishment of the repair action constitutes terminating action for the repetitive inspection requirements of paragraph (a) of this AD for that repaired area. (1) For airplanes equipped with integral fuel tanks in the center section of the wings: Repair in accordance with Figure 2 of Boeing Service Bulletin 727-57-0177, Revision 3, dated February 15, 1996. (2) For airplanes not equipped with integral fuel tanks in the center section of the wings: Repair in accordance with Figure 2 of Boeing Service Bulletin 727-57-0177, dated December 22, 1988, Revision 1, dated November 21, 1991; Revision 2, dated September 16, 1993; or Revision 3, dated February 15, 1996.

Note 4: Where there are differences between the referenced service bulletins and this AD, the AD prevails.

Modification

(c) Except as provided by paragraph (d) of this AD, prior to the accumulation of 60,000 total flight cycles, or within 48 months after the effective date of this AD, whichever occurs later, accomplish the actions specified in either paragraph (c)(1) or (c)(2) of this AD, as applicable. Accomplishment of this action constitutes terminating action for the repetitive inspection requirements of paragraph (a) of this AD. (1) For airplanes equipped with integral fuel tanks in the center section of the wings: Modify the front spar web, between the upper and lower seals, of the center section of the wings, in accordance with Part I of the Accomplishment Instructions of Boeing Service Bulletin 727-57-0177, Revision 3, dated February 15, 1996. (2) For airplanes not equipped with integral fuel tanks in the center section of the wings: Modify the front spar web, between the upper and lower seals, of the center section of the wings, in accordance with Boeing Service Bulletin 727-57-0177, dated December 22, 1988, Revision 1, dated November 21, 1991; Revision 2, dated September 16, 1993; or Revision 3, dated February 15, 1996.

Repetitive Visual Inspections and Repair/Modification of the Front Spar Web

(d) For areas on which the front spar web between the upper and lower seals of the center section of the wings has been repaired or modified in accordance with Figure 2 or 3 of Boeing Service Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated November 21, 1991; or Revision 2, dated September 16, 1993: Accomplish the actions required by either paragraph (d)(1) or (d)(2) of this AD, as applicable. (1) For airplanes not equipped with integral fuel tanks in the center section of the wings: No further action is required by this AD for those areas repaired or modified. (2) For airplanes equipped with integral fuel tanks in the center section of the wings: Accomplish the actions required by both paragraphs (d)(2)(i) and (d)(2)(ii) of this AD. (i) Within 500 flight cycles after the effective date of this AD, perform a detailed visual inspection of the front spar web to detect fuel leakage and penetrations in the secondary fuel barrier, and to verify the installation of the secondary fuel barrier; in accordance with Boeing Service Bulletin 727-57-0177, Revision 3, dated February 15, 1996. Repeat the visual inspection thereafter at intervals not to exceed 1,500 flight cycles, until accomplishment of the actions required by paragraph (d)(2)(ii) of this AD. (ii) Prior to the accumulation of 14,000 flight cycles, or within 96 months after the effective date of this AD, whichever occurs later, repair/modify the front spar web in accordance with Part II of the Accomplishment Instructions of Boeing Service Bulletin 727-57-0177, Revision 3, dated February 15, 1996. Accomplishment of this action constitutes terminating action for the repetitive inspection requirements of paragraph (d)(2)(i) of this AD for that repaired/modified area.

Follow-On Corrective Action

(e) During any inspection required by paragraph (d)(2)(i) of this AD, if any fuel leakage or penetration in the secondary fuel barrier is detected, or if any secondary fuel barrier is verified as not being installed, prior to further flight, repair in accordance with Part II of the Accomplishment Instructions of Boeing Service Bulletin 727-57-0177, Revision 3, dated February 15, 1996. Accomplishment of this action constitutes terminating action for the repetitive inspection requirements of paragraph (d)(2)(i) of this AD for that repaired area.

Terminating Action for AD 94-05-04

(f) Accomplishment of the actions required by paragraph (b), (c), (d)(2)(ii), or (e) of this AD constitutes terminating action for the requirements specified in paragraph (a) of AD 94-05-04, amendment 39-8842 (59 FR 13442

dated March 22, 1994), with respect to the modification specified in Boeing Service Bulletin 727-57-0177, dated December 22, 1988. This service bulletin is one of many service bulletins referenced in Boeing Document D6-54860, Revision G, Appendix A.3, dated March 5, 1993. All other service bulletins referenced in that document still apply.

Alternative Method of Compliance

(g)(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 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 5: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(g)(2) For airplanes not equipped with integral fuel tanks in the center section of the wings: Alternative methods of compliance, approved previously in accordance with AD 90-02-16, amendment 39- 6452, are approved as alternative methods of compliance with this AD. For airplanes equipped with integral fuel tank in the center section of the wings: Alternative methods of compliance, approved previously in accordance with AD 90-02-15, are NOT approved as alternative methods of compliance with this AD.

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.

Issued in Renton, Washington, on August 4, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-20504 Filed 8-9-99; 8:45 am] BILLING CODE 4910-13-P