[Federal Register Volume 65, Number 22 (Wednesday, February 2, 2000)]
[Proposed Rules]
[Pages 4900-4902]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-2090]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-330-AD]
RIN 2120-AA64


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 adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes. This proposal would require repetitive inspections of the 
aft pressure bulkhead to detect cracking, and repair, if necessary. 
This proposal is prompted by a report of fatigue cracking found in the 
upper half of the aft pressure bulkhead. The actions specified by the 
proposed AD are intended to detect and correct cracking in the aft 
pressure bulkhead, which could result in rapid decompression of the 
fuselage or overpressurization of the tail section.

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. 99-NM-330-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.

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.

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 99-NM-330-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. 99-NM-330-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report indicating that a crack was found in 
the upper half of the aft pressure bulkhead on a Boeing Model 747 
series airplane. The crack was located at the aft/inner fastener row, 
which attaches the web to the ``Y'' ring, and was 7.5 inches long. 
Analysis indicates that the crack was initiated and propagated by 
fatigue. Such cracking, if not detected and corrected, could result in 
rapid decompression of the fuselage or overpressurization of the tail 
section.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-53A2425, dated October 29, 1998, which describes procedures for 
repetitive inspections of the aft pressure bulkhead at the ``Y''-ring-
to-web lap splice to detect cracking, and repair, if necessary. The 
inspections to detect cracking include a detailed visual inspection of 
the upper half of the bulkhead and a high frequency eddy current (HFEC) 
inspection of the upper and lower halves of the bulkhead. 
Accomplishment of the actions specified in the alert service bulletin 
is intended to adequately address the identified unsafe condition.

Other Relevant Rulemaking

    The FAA has previously issued AD 98-20-20, Amendment 39-10786 (63 
FR 50495, September 22, 1998). That AD requires repetitive inspections 
to detect damage and cracking of the aft pressure bulkhead on certain 
Boeing Model 747 series airplanes, line numbers 1 through 671 
inclusive. The inspections required by that AD are similar to the ones 
described in this proposed AD, but this proposed AD would apply to 
Boeing Model 747 series airplanes having line numbers 672 and 
subsequent, as listed in Boeing Alert Service Bulletin 747-53A2425.

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 require accomplishment of the actions specified in 
the alert service bulletin described previously, except as discussed 
below.

Differences Between Alert Service Bulletin and Proposed Rule

    Operators should note that, although the alert service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions,

[[Page 4901]]

this proposed AD requires the repair of those conditions to be 
accomplished in accordance with a method approved by the 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 FAA to make such 
findings.
    The alert service bulletin also specifies that certain inspections 
and repairs required by this proposed AD may be accomplished in 
accordance with ``an operator's equivalent procedure.'' However, this 
proposed AD requires that those actions be accomplished in accordance 
with the procedures specified in appropriate chapters of the Boeing 747 
Maintenance Manual or the Boeing 747 Structural Repair Manual. An 
``operator's equivalent procedure'' may be used only if approved as an 
alternative method of compliance in accordance with paragraph (g) of 
this AD.

Clarification of Proposed Requirement

    The FAA has been advised that the intent of the manufacturer in the 
service bulletin is that accomplishment of an HFEC inspection implies 
concurrent accomplishment of a detailed visual inspection. Therefore, 
this proposed rule clarifies the manufacturer's intent, in that it 
proposes to require accomplishment of repetitive detailed visual 
inspections at intervals not to exceed 1,500 flight cycles, and 
repetitive HFEC inspections at intervals not to exceed 3,000 flight 
cycles.

Cost Impact

    There are approximately 552 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 84 airplanes of U.S. registry 
would be affected by this proposed AD.
    It would take approximately 7 work hours per airplane to accomplish 
the proposed detailed visual inspection, at the average labor rate of 
$60 per work hour. Based on these figures, the cost impact of the 
proposed detailed visual inspection on U.S. operators is estimated to 
be $35,280, or $420 per airplane, per inspection cycle.
    It would take approximately 7 work hours per airplane to accomplish 
the proposed HFEC inspections, at the average labor rate of $60 per 
work hour. Based on these figures, the cost impact of the proposed HFEC 
inspections on U.S. operators is estimated to be $35,280, or $420 per 
airplane, per inspection cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the 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 adding the following new 
airworthiness directive:
Boeing: Docket 99-NM-330-AD.
    Applicability: Model 747 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-53A2425, dated October 29, 1998; 
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) 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 cracking in the aft pressure bulkhead, 
which could result in rapid decompression of the fuselage or 
overpressurization of the tail section, accomplish the following:

Initial and Repetitive Inspections

    (a) Except as provided by paragraph (f) of this AD, prior to the 
accumulation of 20,000 total flight cycles, or within 12 months 
after the effective date of this AD, whichever occurs later, perform 
a detailed visual inspection of the upper half of the aft pressure 
bulkhead to detect cracking, in accordance with Figure 6 or 7, as 
applicable, of Boeing Alert Service Bulletin 747-53A2425, dated 
October 29, 1998. Repeat the detailed visual inspection thereafter 
at intervals not to exceed 1,500 flight cycles. For areas of the 
upper half of the aft pressure bulkhead that have been repaired 
previously, this detailed visual inspection may be deferred for up 
to 15,000 flight cycles after accomplishment of the repair, as 
described in the NOTE in paragraph 3.D. of the Accomplishment 
Instructions of the alert service bulletin.


    Note 2:  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) Except as provided by paragraph (f) of this AD, if no 
cracking is detected during the initial detailed visual inspection 
required by paragraph (a) of this AD: Within 1,500 flight cycles 
after accomplishment of that inspection, perform a high frequency 
eddy current (HFEC) inspection of the upper and lower halves of the 
aft pressure bulkhead to detect cracking, in accordance with Figure 
8 of Boeing Alert Service Bulletin 747-53A2425, dated October 29, 
1998. Repeat the HFEC inspection thereafter at intervals not to 
exceed 3,000 flight cycles.
    (c) Except as provided by paragraph (f) of this AD, if any 
cracking is detected during any inspection required by paragraph (a) 
of this AD: Prior to further flight, perform an HFEC inspection of 
the upper and lower halves of the aft pressure bulkhead to detect 
cracking, in accordance with Figure 8 or 9, as applicable, of Boeing 
Alert Service Bulletin 747-53A2425, dated October 29, 1998. Repeat 
the HFEC inspection thereafter at intervals not to exceed 3,000 
flight cycles.

[[Page 4902]]

Repair

    (d) Except as provided by paragraphs (e) and (f) of this AD, if 
any cracking is detected during any inspection required by paragraph 
(a), (b), or (c) of this AD: Prior to further flight, repair in 
accordance with Boeing Alert Service Bulletin 747-53A2425, dated 
October 29, 1998.
    (e) If any cracking is detected during any inspection required 
by paragraph (a), (b), or (c) of this AD, and Boeing Alert Service 
Bulletin 747-53A2425, dated October 29, 1998, specifies to contact 
Boeing for repair instructions: 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 (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.

Operator's ``Equivalent Procedure''

    (f) Where Boeing Alert Service Bulletin 747-53A2425, dated 
October 29, 1998, specifies that an inspection or a repair, as 
applicable, may be accomplished in accordance with an operator's 
``equivalent procedure'': The inspection or repair, as applicable, 
must be accomplished in accordance with the applicable chapter of 
the Boeing 747 Maintenance Manual or the Boeing 747 Structural 
Repair Manual specified in the alert service bulletin.

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.

    Issued in Renton, Washington on January 24, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-2090 Filed 2-1-00; 8:45 am]
BILLING CODE 4910-13-U