94-2410. Airworthiness Directives; Boeing Model 747 Series Airplanes  

  • [Federal Register Volume 59, Number 23 (Thursday, February 3, 1994)]
    [Unknown Section]
    [Page 0]
    From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
    [FR Doc No: 94-2410]
    
    
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    [Federal Register: February 3, 1994]
    
    
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    DEPARTMENT OF TRANSPORTATION
    
    Federal Aviation Administration
    
    14 CFR Part 39
    
    [Docket No. 93-NM-183-AD]
    
     
    
    Airworthiness Directives; Boeing Model 747 Series Airplanes
    
    AGENCY: Federal Aviation Administration, DOT.
    
    ACTION: Notice of proposed rulemaking (NPRM).
    
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    SUMMARY: This document proposes the supersedure of an existing 
    airworthiness directive (AD), applicable to certain Boeing Model 747 
    series airplanes, that currently requires inspecting to detect cracking 
    in certain lower lobe lap joints, and repair, if necessary; reporting 
    any findings of discrepancies; replacing certain countersunk fasteners 
    with protruding head fasteners; and verifying that the airplanes do not 
    have certain countersunk fasteners. This action would increase the area 
    to be inspected, delete the reporting requirement, and expand the 
    applicability. This proposal is prompted by reports of fuselage skin 
    cracking in certain areas and findings of additional countersunk 
    fasteners. The actions specified by the proposed AD are intended to 
    prevent reduced structural integrity of the fuselage.
    
    DATES: Comments must be received by March 30, 1994.
    
    ADDRESSES: Submit comments in triplicate to the Federal Aviation 
    Administration (FAA), Transport Airplane Directorate, ANM-103, 
    Attention: Rules Docket No. 93-NM-183-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.
        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.
    
    FOR FURTHER INFORMATION CONTACT: Steven C. Fox, Aerospace Engineer, 
    Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
    Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
    Washington 98055-4056; telephone (206) 227-2777; fax (206) 227-1181.
    
    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 93-NM-183-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-103, Attention: Rules 
    Docket No. 93-NM-183-AD, 1601 Lind Avenue, SW., Renton, Washington 
    98055-4056.
    
    Discussion
    
        On December 19, 1989, the FAA issued AD 90-01-07, Amendment 39-6440 
    (55 FR 255, January 4, 1990), applicable to Boeing Model 747 series 
    airplanes, having line numbers 201 through 765, inclusive, to require:
        1. Repetitively inspecting to detect cracking in certain lower lobe 
    lap joints, and repair, if necessary;
        2. Reporting any findings of discrepancies;
        3. Replacing certain countersunk fasteners with protruding head 
    fasteners; and
        4. Verifying that airplanes do not have certain countersunk 
    fasteners.
        That action was prompted by reports of cracking in the lap joint of 
    stringer 34 near the interface with the wing-to-body fairing. The 
    requirements of that AD are intended to prevent in-flight 
    depressurization due to undetected cracks in the skin of the airplane.
        Since the issuance of that AD, the FAA has received additional 
    reports of cracking in the upper row of countersunk fasteners in the 
    lap splice in the area adjacent to the wing-to-body fairing 
    intersection on Model 747 series airplanes. Additionally, several 
    airplanes were found to have more than the necessary number of 
    countersunk fasteners, which were installed during production at the 
    upper row of the lap splice at stringer 34. These countersunk fasteners 
    were found in the upper row of fasteners in the lap splice near the 
    wing-to-body fairing and skin intersection between body station (BS) 
    768 and the circumferential skin joint at BS 741.
        Cracking in locations where countersunk fasteners were installed, 
    if not corrected, could result in reduced structural integrity of the 
    fuselage.
        The FAA has reviewed and approved Boeing Service Bulletin 747-
    53A2312, Revision 2, dated October 8, 1992, that describes procedures 
    for visually inspecting to determine the number of countersunk 
    fasteners in the upper row of the lap splice.
        If more than the necessary number of countersunk fasteners were 
    installed during production, this service bulletin specifies conducting 
    an external high frequency eddy current (HFEC) inspection to detect 
    cracking in the skin lap splices at the wing-to-body fairing 
    intersection where countersunk fasteners were found in the upper row of 
    fasteners. If cracking is found, the service bulletin describes 
    procedures for modifying the locations where countersunk fasteners were 
    found by replacing the countersunk fasteners with oversized protruding 
    head fasteners and repairing the skin. These actions were accomplished, 
    prior to delivery, on airplanes having line numbers 815 through 919, 
    inclusive.
        If the proper number of countersunk fasteners were installed during 
    production, repetitive inspections are specified in the service 
    bulletin until the locations where countersunk fasteners were installed 
    have been modified.
        The service bulletin describes procedures for eventual modification 
    of all airplanes at the location where countersunk fasteners were 
    installed, and repetitive inspections following modification.
        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 90-01-07 to:
        1. Continue to require inspections to detect cracking in certain 
    lower lobe lap joints, and repair, if necessary;
        2. Require visual inspections to determine if countersunk fasteners 
    had been installed between body stations (BS) 741 and 1000 at Stringers 
    (S-)34L, S-34R, S-39L, S-39R, and S-44L, S-44R, and between BS 1480 and 
    1741 at S-34L, S-34R, S-40L, and S-40R on airplanes having line numbers 
    201 through 814, inclusive;
        3. Require HFEC inspections to detect cracking at all locations 
    where countersunk fasteners were found in the upper row of the lap 
    splice, and repair, if necessary; and
        4. Require modification of all locations where countersunk 
    fasteners were found.
        Although the actions and compliance times of this proposed AD would 
    differ from the manufacturer's recommendations specified in the service 
    bulletin, the actions themselves would be required to be accomplished 
    in accordance with the procedures of the service bulletin described 
    previously.
        There are approximately 723 Boeing Model 747 series airplanes of 
    the affected design in the worldwide fleet. The FAA estimates that 183 
    airplanes of U.S. registry would be affected by this AD.
        The inspections that were previously required by AD 90-01-07, and 
    retained in this AD, take approximately 14 workhours per airplane to 
    accomplish, at an average labor rate of $55 per work hour. Based on 
    these figures, the total cost impact of these inspection requirements 
    of this AD on U.S. operators is estimated to be $140,910 or $770 per 
    airplane, per inspection cycle.
        The additional new inspections that would be required by this AD 
    would take approximately 82 work hours per airplane to accomplish, at 
    an average labor rate of $55 per work hour. Based on these figures, the 
    total cost impact of these inspection requirements of this AD on U.S. 
    operators is estimated to be $825,330, or $4,510 per airplane
        The modification required by this AD would take approximately 124 
    work hours per airplane to accomplish, at an average labor rate of $55 
    per work hour. Required parts would be nominal in cost. Based on these 
    figures, the total cost impact of the modification requirements of this 
    AD on U.S. operators is estimated to be $1,248,060, or $6,820 per 
    airplane.
        Based on the above figures, the total cost impact of the inspection 
    and modification requirements of this AD on U.S. operators is estimated 
    to be $2,214,300, or $11,407 per airplane. This total cost figure 
    assumes that no operator has yet accomplished the proposed requirements 
    of this AD action.
        The FAA recognizes that the proposed modification would require a 
    large number of work hours to accomplish. However, the 20,000-flight 
    cycle compliance time specified in paragraph (j) of this proposed AD 
    should allow ample time for the modification of all locations where 
    countersunk fasteners were found to be accomplished coincidentally with 
    scheduled major airplane inspection and maintenance activities, thereby 
    minimizing the costs associated with special airplane scheduling.
        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 14 
    CFR part 39 of the Federal Aviation Regulations as follows:
    
    PART 39--AIRWORTHINESS DIRECTIVES
    
        1. The authority citation for part 39 continues to read as follows:
    
        Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
    106(g); and 14 CFR 11.89.
    
    
    Sec. 39.13  [Amended]
    
        2. Section 39.13 is amended by removing amendment 39-6440 (55 FR 
    255, January 4, 1990), and by adding a new airworthiness directive 
    (AD), to read as follows:
    
    Boeing: Docket 93-NM-183-AD. Supersedes AD 90-01-07, Amendment 39-
    6440.
    
        Applicability: Model 747 series airplanes, having line numbers 
    201 through 814 inclusive, certificated in any category.
        Compliance: Required as indicated, unless accomplished 
    previously.
        To prevent reduced structural integrity of the fuselage, 
    accomplish the following:
    
    Restatement of Requirements of AD 90-01-07, Amendment 39-6440
    
        (a) For airplanes having line numbers 201 through 765: Conduct a 
    high frequency eddy current (HFEC) inspection to detect cracking of 
    the lower lobe lap joints in the vicinity of the wing-to-body 
    fairing in accordance with Boeing Alert Service Bulletin 747-
    53A2312, dated June 12, 1989; or Revision 1, dated March 29, 1990; 
    or Revision 2, dated October 8, 1992; at the time specified in 
    paragraph (a)(1), (a)(2), (a)(3), or (a)(4) of this AD, as 
    applicable. Repeat this inspection thereafter at intervals not to 
    exceed 4,000 landings until the inspection required by paragraph (e) 
    of this AD is accomplished.
        (1) For airplanes that have accumulated less than 11,200 total 
    landings as of February 5, 1990 (the effective date of AD 90-01-07): 
    Prior to the accumulation of 11,000 landings or within the next 
    1,000 landings after February 5, 1990, whichever occurs later.
        (2) For airplanes that have accumulated 11,200 or more total 
    landings but less than 15,201 total landings as of February 5, 1990 
    (the effective date of AD 90-01-07): Within the next 1,000 landings 
    after February 5, 1990, or prior to the accumulation of 15,500 total 
    landings, whichever occurs earlier.
        (3) For airplanes that have accumulated 15,201 or more total 
    landings but less than 18,200 total landings as of February 5, 1990: 
    Within the next 300 landings after February 5, 1990, or prior to the 
    accumulation of 18,250 total landings, whichever occurs earlier.
        (4) For airplanes that have accumulated 18,200 or more landings 
    as of February 5, 1990: Within the next 50 landings after February 
    5, 1990.
        (b) For airplanes having line numbers 201 through 765: 
    Accomplish the requirements of paragraphs (b)(1) and (b)(2) of this 
    AD.
        (1) If any cracking is detected, prior to further flight, repair 
    in accordance with Boeing Alert Service Bulletin 747-53A2312, dated 
    June 12, 1989; or Revision 1, dated March 29, 1990; or Revision 2, 
    dated October 8, 1992.
        (2) Prior to the accumulation of 20,000 total landings or within 
    the next 3,000 landings after February 5, 1990 (the effective date 
    of AD 90-01-07), whichever occurs later, modify the airplane by 
    replacing countersunk fasteners in the upper row of the lower lobe 
    lap joints in the vicinity of the wing-to-body fairing with 
    protruding head fasteners, in accordance with the procedures 
    described in the Boeing Alert Service Bulletin 747-53A2312, dated 
    June 12, 1989; or Revision 1, dated March 29, 1990; or Revision 2, 
    dated October 8, 1992.
        (c) For purposes of complying with paragraphs (a) and (b) of 
    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 p.s.i.
        (d) For Model 747SR airplanes only: Based on continued mixed 
    operation of lower cabin differentials, the inspection and 
    modification compliance times specified paragraphs (a) and (b) of 
    this AD may be multiplied by a 1.2 adjustment factor.
    
    New Requirements of This AD
    
        (e) Prior to the accumulation of 11,000 total landings, or 
    within 1,000 landings after the effective date of this AD, whichever 
    occurs later, unless previously accomplished within the last 3,000 
    landings prior to the effective date of this AD, conduct a visual 
    inspection to determine if countersunk fasteners have been installed 
    in the area defined in either paragraph (e)(1) or (e)(2), as 
    applicable, in accordance with the procedures described in Boeing 
    Service Bulletin 747-53A2312, Revision 2, dated October 8, 1992. 
    Accomplishment of this inspection terminates the inspection 
    requirements of paragraph (a) of this AD.
        (1) For Model 747-100, -200, -300, -400, and 747SR series 
    airplanes: From body stations (BS) 741 to 1000 at Stringers (S-)34L, 
    S-34R, S-39L, S-39R, S-44L, and S-44R, and from BS 1480 to 1741 at 
    S-34L, S-34R, S-40L, and S-40R.
        (2) For Model 747SP series airplanes: From BS 520 to 1000 at S-
    34L, S-34R, S-39L, S-39R, S-44L, and S-44R, and from BS 1480 to 1741 
    at S-34L, S-34R, S-40L, and S-40R.
        (f) If no countersunk fastener is found in the upper row of the 
    lap splice, no further action is required by this AD.
        (g) If any countersunk fastener is found in the upper row of the 
    lap splice, prior to further flight, perform an HFEC inspection to 
    detect cracking at all locations where countersunk fasteners were 
    found, in accordance with the procedures described in Boeing Service 
    Bulletin 747-53A2312, Revision 2, dated October 8, 1992.
        (h) If no cracking is detected during any inspection required by 
    paragraphs (g), (h), (i), and (k) of this AD, at any location where 
    a countersunk fastener was found, thereafter repeat the inspection 
    at intervals not to exceed 4,000 landings, in accordance with the 
    procedures described in the Boeing Service Bulletin 747-53A2312, 
    Revision 2, dated October 8, 1992.
        (i) If cracking is detected during any inspection required by 
    paragraphs (g), (h), (i), and (k) of this AD, at any location where 
    a countersunk fastener was found, prior to further flight, repair 
    and modify that lap joint in accordance with Boeing Service Bulletin 
    747-53A2312, Revision 2, dated October 8, 1992.
        (j) Prior to the accumulation of 20,000 total landings or within 
    1,000 landings after the effective date of this AD, whichever occurs 
    later, modify all locations where countersunk fasteners were found, 
    in accordance with the procedures described in Boeing Service 
    Bulletin 747-53A2312, Revision 2, dated October 8, 1992. For 
    purposes of complying with the requirements of this paragraph, 
    locations that were previously modified, in accordance with 
    paragraph (b) of this AD, do not need to be modified again.
        (k) Prior to the accumulation of 10,000 total landings following 
    modification of the locations where countersunk fasteners were 
    installed, perform an HFEC inspection at all locations where 
    countersunk fasteners were found, and thereafter, repeat this 
    inspection at intervals not to exceed 4,000 landings, in accordance 
    with the procedures described in Boeing Service Bulletin 747-
    53A2312, Revision 2, dated October 8, 1992.
        (l) 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 Aircraft Certification 
    Office (ACO), FAA, Transport Airplane Directorate. 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: Information concerning the existence of approved 
    alternative methods of compliance with this AD, if any, may be 
    obtained from the Seattle ACO.
    
        (m) Special flight permits may be issued in accordance with FAR 
    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 January 28, 1994.
    Darrell M. Pederson,
    Acting Manager, Transport Airplane Directorate, Aircraft Certification 
    Service.
    [FR Doc. 94-2410 Filed 2-2-94; 8:45 am]
    BILLING CODE 4910-13-P
    
    
    

Document Information

Published:
02/03/1994
Department:
Federal Aviation Administration
Entry Type:
Uncategorized Document
Action:
Notice of proposed rulemaking (NPRM).
Document Number:
94-2410
Dates:
Comments must be received by March 30, 1994.
Pages:
0-0 (1 pages)
Docket Numbers:
Federal Register: February 3, 1994, Docket No. 93-NM-183-AD
CFR: (1)
14 CFR 39.13