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Proposed Rule

Airworthiness Directives; Boeing Model 747 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 747 series airplanes, that currently requires repetitive inspections for damage or cracking of the aft pressure bulkhead, and repair, if necessary. That action also removes certain repetitive inspections for cracking of the bulkhead web to Y-ring lap joint area, but retains the initial inspection for cracking in that area. That action also adds a one-time detailed visual inspection from the forward side of the bulkhead to detect fatigue cracking of the upper segment of the bulkhead web, and follow-on corrective actions, if necessary. This action would require that the one-time inspection be accomplished repetitively, and would add additional repetitive inspections. The actions specified by the proposed AD are intended to detect and correct fatigue cracking of the bulkhead web, which could result in rapid depressurization of the airplane, and consequent reduced controllability of the airplane.

DATES:

Comments must be received by March 20, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-285-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.

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.

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FOR FURTHER INFORMATION CONTACT:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; 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 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 98-NM-285-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-285-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On September 14, 1998, the FAA issued AD 98-20-20, amendment 39-10786 (63 FR 50495, September 22, 1998), applicable to certain Boeing 747 series airplanes, to require certain repetitive inspections for damage or cracking of the aft pressure bulkhead, and repair, if necessary. In addition, that AD removes repetitive detailed visual inspections for cracking of the bulkhead web to Y-ring lap joint area, but retains the initial inspection for cracking in that area. That AD also adds a one-time detailed visual inspection from the forward side of the bulkhead to detect fatigue cracking of the upper segment of the bulkhead web, and follow-on corrective actions, if necessary. That action was prompted by reports indicating that the inspections required by AD 87-23-10, amendment 39-5758 (52 FR 41551, October 29, 1987), may not detect cracking of the bulkhead web in a timely manner. The requirements of AD 98-20-20 are intended to detect and correct fatigue cracking of the upper segment of the bulkhead web, which could result in rapid depressurization of the airplane, and consequent reduced controllability of the airplane.

Actions Since Issuance of Previous Rule

In the preamble of AD 98-20-20, the FAA specified that the actions required by that AD were considered to be interim action. The FAA indicated that it may consider further rulemaking action to require repetitive detailed visual inspections and surface probe high frequency eddy current (HFEC) inspections to detect cracking of the upper and lower segments of the aft pressure bulkhead web, and repair if necessary. The FAA has determined that further rulemaking is indeed necessary; this proposed AD follows from that determination.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998, which describes procedures for, among other things, repetitive inspections from the forward side of the bulkhead web at body station (BS) 2360 to detect cracking. The inspections to detect cracking include a detailed visual inspection of the upper half of the bulkhead and a surface probe HFEC inspection of the upper and lower segments of the bulkhead. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. Start Printed Page 4907

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 98-20-20 to continue to require the actions specified in that AD. This action also would require that the one-time detailed visual inspection required by AD 98-20-20 be accomplished repetitively, and would add repetitive surface probe HFEC inspections, and repair, if necessary. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below.

Differences Between Proposed AD and Service Bulletin

Operators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain cracking conditions, this proposal would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA.

Clarification of Proposed Requirement

The FAA has been advised that the manufacturer's intent of the surface probe HFEC inspection, as described in Figure 15 of the service bulletin, is that accomplishment of a surface probe HFEC inspection implies concurrent accomplishment of a detailed visual inspection, as described in Figure 14 of the service bulletin. This proposed rule clarifies the manufacturer's intent, in that it would explicitly require accomplishment of the repetitive detailed visual inspections at intervals not to exceed 1,500 flight cycles, and repetitive surface probe HFEC inspections at intervals not to exceed 3,000 flight cycles.

Cost Impact

There are approximately 671 airplanes of the affected design in the worldwide fleet. The FAA estimates that 149 airplanes of U.S. registry would be affected by this proposed AD.

The actions that are currently required by AD 98-20-20 and retained in this proposed AD, take approximately 360 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 actions on U.S. operators is estimated to be $3,218,400, or $21,600 per airplane, per inspection cycle.

The new repetitive detailed visual inspections that are proposed in this AD action would 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 of the proposed requirements of this AD on U.S. operators is estimated to be $35,760, or $240 per airplane, per inspection cycle.

The new repetitive HFEC inspections that are proposed in this AD action would take approximately 48 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 proposed requirements of this AD on U.S. operators is estimated to be $429,120, or $2,880 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.

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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:

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

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[Amended]

2. Section 39.13 is amended by removing amendment 39-10786 (63 FR 50495, September 22, 1998), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 98-NM-285-AD. Supersedes AD 98-20-20, Amendment 39-10786.

Applicability: Model 747 series airplanes, line positions 1 through 671 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 in accordance with paragraph (j)(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 detect and correct fatigue cracking of the bulkhead web, which could result in rapid depressurization of the airplane, and consequent reduced controllability of the airplane, accomplish the following:

Restatement of Actions Required by AD 98-20-20, Amendment 39-10786

(a) Within 750 landings after December 10, 1987 (the effective date for AD 87-23-10, amendment 39-5758), unless accomplished within the last 1,250 landings [for airplanes subject to a 2,000-landing repeat inspection interval in accordance with paragraph (b) of this AD], or unless accomplished within the last 250 landings [for airplanes subject to a 1,000-landing repeat inspection interval in accordance with paragraph (b) of this AD], perform a detailed visual inspection; in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998; of the aft side of the entire Body Station (BS) 2360 aft pressure bulkhead for damage such as dents, tears, nicks, gouges, or scratches; and cracks at splices and doublers, and around the Auxiliary Power Unit pressure pan cutout; and, for Group 4 airplanes only, inspect from the forward side, the area adjacent to the window cutout for damage or cracks.

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Note 2:

Notwithstanding provisions to the contrary in AD 87-23-10, and in Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, and Revision 5, dated January 16, 1997: For Model 747SR airplanes operating at a cabin pressure differential lower than 8.6 pounds-per-square-inch (psi), an adjustment factor of 1.2 shall not be used after October 7, 1998 (the effective date for AD 98-20-20), as a multiplier for inspection thresholds and intervals specified in this AD.

Note 3:

For the purposes of this AD, a detailed visual 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.”

(b) After initial compliance with paragraph (a) of this AD, continue to inspect as follows:

(1) For Group 1 airplanes, repeat the inspections required by paragraph (a) of this AD, at intervals not to exceed 2,000 landings.

(2) For Groups 2 and 3 airplanes, repeat the inspections required by paragraph (a) of this AD, at intervals not to exceed 1,000 landings; or optionally, at the applicable time specified in paragraph (b)(2)(i) or (b)(2)(ii) of this AD.

(i) For Group 2 airplanes that operate the entire interval with aft lavatory complexes or galleys adjacent to bulkheads, repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 2,000 landings.

(ii) For Groups 2 and 3 airplanes that operate the entire interval with an intact protective shield on the lower half of the forward side of the bulkhead, repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 2,000 landings; and perform a detailed visual inspection of the protective shield for damage in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998, at intervals not to exceed 1,000 landings. If damage is found to the protective shield that exceeds the limits indicated in the service bulletin, prior to further flight, repeat the inspection required by paragraph (a) of this AD.

(3) For Group 4 airplanes, repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 1,000 landings.

(c) Within 750 landings after December 10, 1987, or prior to the accumulation of 20,000 total landings, whichever occurs later, unless accomplished within the last 3,250 landings; and at intervals thereafter not to exceed 4,000 landings; perform eddy current, ultrasonic, and X-ray inspections of the aft side of the BS 2360 aft pressure bulkhead for cracks; in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998.

(d) Within 750 landings after December 10, 1987, or prior to the accumulation of 20,000 total landings, whichever occurs later, unless accomplished within the last 6,250 landings; and thereafter at intervals not to exceed 7,000 landings until the inspection required by paragraph (g) of this AD is accomplished: Perform a detailed visual inspection to detect cracking of the BS 2360 aft pressure bulkhead web to Y-ring lap joint area between radial stiffeners from the forward side of the bulkhead, in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998.

(e) If any cracking or damage is found during any inspection required by paragraph (a), (b), (c), or (d) of this AD, repair prior to further flight in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998.

(f) For the purpose of complying with this AD, the number of landings may be determined to equal the number of pressurization cycles where the cabin pressure differential was greater than 2.0 psi.

(g) Perform a detailed visual inspection from the forward side of the bulkhead of the upper segment of the bulkhead web at BS 2360 to detect cracking, in accordance with Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998, at the earlier of the times specified in paragraphs (g)(1) and (g)(2) of this AD. Accomplishment of this inspection terminates the repetitive inspection requirement of paragraph (d) of this AD.

(1) Within 7,000 landings after the most recent detailed visual inspection accomplished in accordance with paragraph (d) of this AD.

(2) At the latest of the times specified in paragraphs (g)(2)(i), (g)(2)(ii), and (g)(2)(iii) of this AD.

(i) Prior to the accumulation of 20,000 total landings.

(ii) Within 1,500 landings after the most recent detailed visual inspection accomplished in accordance with paragraph (d) of this AD.

(iii) Within 90 days after October 7, 1998 (the effective date of AD 98-20-20).

(h) If any cracking is detected during the detailed visual inspections required by paragraph (g) of this AD, prior to further flight, accomplish a surface probe high frequency eddy current (HFEC) inspection from the forward side of the bulkhead to detect cracking of the upper and lower segments of the bulkhead web around the fasteners that attach the web to the outer chord of the Y-ring, in accordance with Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. Repair any cracking, prior to further flight, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; 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.

New Requirements of This AD

(i) If no cracking is detected during the detailed visual inspection required by paragraph (g) of this AD, within 1,500 flight cycles after accomplishment of that inspection or within 250 flight cycles after the effective date of this AD, whichever occurs later: Repeat the detailed visual inspection, as specified in paragraph (g); and perform a surface probe HFEC inspection from the forward side of the bulkhead to detect cracking of the upper and lower segments of the bulkhead web, in accordance with Figure 15 of Boeing Start Printed Page 4909Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998.

(1) If no cracking is detected, repeat the detailed visual inspection thereafter at intervals not to exceed 1,500 flight cycles; and repeat the surface probe HFEC inspection thereafter at intervals not to exceed 3,000 flight cycles.

(2) If any cracking is detected, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate, or a Boeing Company Designated Engineering Representative who has been authorized by the FAA 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.

Alternative Methods of Compliance

(j)(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.

(2) Alternative methods of compliance, approved previously in accordance with AD 98-20-20, amendment 39-10786, are approved as alternative methods of compliance with this AD.

Note 4:

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

(k) Special flight permits may be issued in accordance with §§ 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.

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Issued in Renton, Washington, on January 27, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 00-2226 Filed 2-1-00; 8:45 am]

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