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Proposed Rule

Airworthiness Directives; Boeing Model 747-100, -200, -300, 747SP, and 747SR Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

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Start Preamble

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 747-100, -200, -300, 747SP, and 747SR series airplanes, that currently requires repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. This action would add new repetitive inspections for cracking of certain areas of the upper chord of the upper deck floor beams, and repair, if necessary. This proposal is prompted by the results of fatigue testing that revealed severed upper chords of the upper deck floor beams due to fatigue cracking. The actions specified by the proposed AD are intended to prevent loss of the structural integrity of the fuselage, which could result in rapid depressurization of the airplane.

DATES:

Comments must be received by January 11, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-355-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. 2000-NM-355-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:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, 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 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 Start Printed Page 59181must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-355-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. 2000-NM-355-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On April 22, 1993, the FAA issued AD 93-08-12, amendment 39-8559 (58 FR 27927, May 12, 1993), applicable to certain Boeing Model 747 series airplanes, to require repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. That action was prompted by results of fatigue tests that identified areas of the fuselage internal structure where fatigue cracks occurred. The requirements of that AD are intended to prevent loss of the structural integrity of the fuselage.

Actions Since Issuance of Previous Rule

Since the issuance of AD 93-08-12, the FAA received a report that, during fatigue testing, severed upper chords were found on the upper deck floor beams on a Boeing Model 747 series airplane. The chords severed as a result of fatigue cracking. Additional reports were received that indicated the detailed internal visual inspections of the upper deck floor beams, mandated by AD 93-08-12 may not detect cracks before they become critical. Such conditions, if not corrected, could result in loss of the structural integrity of the fuselage, and rapid depressurization of the airplane.

Related AD

On February 22, 2000, the FAA issued AD 2000-04-17, amendment 39-11600 (65 FR 10695, February 29, 2000), applicable to certain Boeing Model 747-100, -200, and -300 series airplanes. That AD requires repetitive inspections to detect fatigue cracking in the chords and webs of certain upper deck floor beams, and repair of any cracking found. This proposed AD would require similar inspections of upper deck floor beams that were not addressed in that AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000, which describes procedures for detailed visual inspections for cracking in the following areas of the fuselage internal structure:

  • Sections 41 and 42 upper deck floor beams
  • Section 42 frames
  • Section 46 frames
  • Certain Section 41 bulkhead areas

The service bulletin also describes procedures for repetitive detailed internal and external visual inspections of the main entry doors and door cutouts for cracking, and repetitive open hole high frequency eddy current inspections for cracking in the horizontal flanges of the upper chord of the Sections 41 and 42 upper deck floor beams. The new detailed visual inspection of Area 1 of Sections 41 and 42 would eliminate the need for the existing inspection of those sections. If cracking is found, the service bulletin references the 747 Structural Repair Manual (SRM) for repair instructions, or if the damage is beyond the limits specified in the service bulletin, the service bulletin specifies contacting Boeing for repair data.

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 93-08-12 to continue to require repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. The proposed AD would add new repetitive inspections for cracking of certain areas of the upper chord of the upper deck floor beams, 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 Revision 1 of the Alert Service Bulletin

This proposed AD differs from the service bulletin as follows:

  • The service bulletin specifies that the manufacturer should be contacted for disposition of certain repair conditions, but this proposed AD would require the repair of those conditions to be accomplished 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 (DER) who has been authorized by the Manager, Seattle Aircraft Certification Office, to make such findings.
  • The service bulletin specifies doing a high frequency eddy current inspection of the left and right sides of the upper deck floor beam at body station 380 between buttock lines 40 and 76, but this proposed AD would not require that inspection because it was mandated in AD 2000-04-17, amendment 39-11600 (65 FR 10695, February 29, 2000).
  • The service bulletin specifies doing detailed visual and high frequency eddy current inspections of body station (BS) 380 through BS 1000 inclusive, on each upper deck floor beam on Group 3 airplanes. This proposed AD would extend the inspection area from BS 380 through BS 1100 inclusive. The manufacturer has informed the FAA that the upper deck floor beams extend to BS 1100 for Group 3 airplanes, and the service bulletin will be revised to reflect this change.
  • The service bulletin also specifies that flight cycles with a cabin pressure differential of less than 2.0 pounds per square inch (psi) are not to be counted, but this proposed AD allows this stipulation only for Area 1 (Sections 41 and 42 upper deck floor beams) inspections. The FAA has determined that flight loads can significantly contribute to fatigue loads in other areas. Flights with less than 2.0 psi cabin differential pressure can still have significant flight loads; therefore, the FAA cannot allow an adjustment to flight cycles for areas other than Area 1.
  • Additionally, this proposed AD adds a grace period of 3,000 flight cycles after doing the most recent inspection required by AD 93-08-12 for airplanes that have exceeded the compliance threshold specified in the service bulletin.

Explanation of Additional Changes to Requirements of Existing AD

We have changed the requirements of the existing AD, as restated in this proposed AD, to remove all references to the use of “FAA-approved procedures.” This change is consistent with FAA policy in that regard. In place of this language, we have specified accomplishing repairs per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company DER. We have determined that this change will not increase the economic burden on any operator, nor will it increase the scope of the proposed AD. A new paragraph (c) has been added to accommodate this change.

Interim Action

This is considered to be interim action until similar action for Boeing Model 747-400 series airplanes and 747 Start Printed Page 59182freighter airplanes is identified, at which time the FAA may consider further rulemaking.

Cost Impact

There are approximately 489 airplanes of the affected design in the worldwide fleet.

The FAA estimates that 181 airplanes of U.S. registry are subject to the existing AD. The actions that are currently required by AD 93-08-12 take approximately 1,746 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 is estimated to be $104,760 per airplane.

We estimate that 155 airplanes of U.S. registry are subject to the new actions in this proposed AD. The new inspections that are proposed in this AD action would take approximately 255 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 $2,371,500, or $15,300 per airplane.

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.

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:

Start Authority

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

End Authority
[Amended]

2. Section 39.13 is amended by removing amendment 39-8559 (58 FR 27927, May 12, 1993), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2000-NM-355-AD. Supersedes AD 93-08-12, Amendment 39-8559.

Applicability: Model 747 series airplanes, as listed in Boeing Service Bulletin 747-53-2349, dated June 27, 1991, or Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000; 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 (h)(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 loss of the structural integrity of the fuselage, which could result in rapid depressurization of the airplane; do the following:

Restatement of Requirements of AD 93-08-12

Repetitive Inspections

(a) Prior to the accumulation of 22,000 total flight cycles, or within 1,000 flight cycles after June 11, 1993 (the effective date of AD 93-08-12, amendment 39-8559), whichever occurs later, unless accomplished previously within the last 2,000 flight cycles; and thereafter at intervals not to exceed 3,000 flight cycles: Perform a detailed visual internal inspection to detect cracks in the areas of the fuselage internal structure specified in paragraphs (a)(1) through (a)(7) of this AD; in accordance with Boeing Service Bulletin 747-53-2349, dated June 27, 1991.

(1) Sections 41 and 42 upper deck floor beams.

(2) Section 42 upper lobe frames.

(3) Section 46 lower lobe frames.

(4) Section 42 lower lobe frames.

(5) Main entry door cutouts.

(6) Section 41 body station 260, 340, and 400 bulkheads.

(7) Main entry doors.

(b) Prior to the accumulation of 25,000 total flight cycles, or within 1,000 flight cycles after June 11, 1993, whichever occurs later, unless accomplished previously within the last 2,000 flight cycles; and thereafter at intervals not to exceed 3,000 flight cycles: Perform a detailed visual internal inspection to detect cracks in the Section 46 upper lobe frames, in accordance with Boeing Service Bulletin 747-53-2349, dated June 27, 1991.

Repair

(c) Prior to further flight, repair any cracks detected during the inspections done per paragraph (a) or (b) of this AD, per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; 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.

New Requirements of This AD

Repetitive Inspections

(d) Before the accumulation of 22,000 total flight cycles, or within 3,000 flight cycles after doing the most recent inspection required by paragraph (a) of this AD, whichever occurs later: Do a detailed visual inspection to find cracking in the areas specified in paragraph (d)(1) or (d)(2) of this AD, as applicable, per Figure 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000. Repeat the inspection after that every 3,000 flight cycles. Doing this inspection terminates the inspections required by paragraph (a) of this AD in the area specified in paragraph (a)(1) of this AD only.

(1) For Groups 1, 2, 4, and 5 airplanes: Do the inspections of Area 1 (sections 41 and 42 upper deck floor beams), including existing repairs and modifications.

(2) For Group 3 airplanes: Do the inspections of Area 1 (sections 41 and 42 upper deck floor beams from body stations 380 through 1100 inclusive), including existing repairs and modifications.

Note 2:

For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific Start Printed Page 59183structural 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.”

(e) Before the accumulation of 28,000 total flight cycles, or within 3,000 flight cycles after doing the most recent inspection required by paragraph (a) of this AD, whichever occurs later: Do a high frequency eddy current (HFEC) inspection to find cracking of the open holes in the horizontal flanges of the upper chord of each upper deck floor beam in the areas specified in paragraph (e)(1) or (e)(2) of this AD, as applicable, per the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000. Do the inspection per “Inspection Alternatives,” as specified in Sheet 7 of Figure 2 of the Accomplishment Instructions of the service bulletin. Repeat the applicable inspection according to the “Repeat Inspection Intervals,” specified in Sheet 7 of Figure 2 of the Accomplishment Instructions of the service bulletin.

(1) For Group 1, 2, 4, and 5 airplanes: Do the inspections at the applicable locations (BS 380 through BS 780 inclusive for Groups 1, 2, and 4, BS 380 through BS 860 inclusive for Group 5) as specified in Sheet 7 of Figure 2.

(2) For Group 3 airplanes: Do the inspections as specified in Sheet 7 of Figure 2, at the upper deck floor beams from BS 380 through BS 1100 inclusive.

Note 3:

HFEC inspections of the left and right sides of the upper deck floor beam at body station 380, between buttock lines 40 and 76, done before the effective date of this AD per AD 2000-04-17, amendment 39-11600, are considered acceptable for compliance with the applicable inspections specified in paragraph (e) of this AD.

Adjustments to Compliance Time: Cabin Differential Pressure

(f) For the purposes of calculating the compliance threshold and repetitive interval for the actions required by paragraphs (d) and (e) of this AD: For Area 1 only, the number of flight cycles in which cabin differential pressure is at 2.0 pounds per square inch (psi) or less need not be counted when determining the number of flight cycles that have occurred on the airplane, provided that flight cycles with momentary spikes in cabin differential pressure above 2.0 psi are included as full pressure cycles. For this provision to apply, all cabin pressure records must be maintained for each airplane: NO fleet-averaging of cabin pressure is allowed.

Repair

(g) Before further flight, repair any cracking found during the inspections done per paragraphs (d) and (e) of this AD, according to Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000. Where the service bulletin specifies to contact Boeing for repair instructions, repair per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Company 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.

Alternative Methods of Compliance

(h)(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 93-08-12, amendment 39-8559, 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

(i) 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 November 20, 2001.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 01-29426 Filed 11-26-01; 8:45 am]

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