[Federal Register Volume 65, Number 218 (Thursday, November 9, 2000)]
[Proposed Rules]
[Pages 67311-67315]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-28723]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 65, No. 218 / Thursday, November 9, 2000 / 
Proposed Rules  

[[Page 67311]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-283-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

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 series airplanes, that currently requires repetitive inspections to 
detect cracking of the outer chord of the body station (BS) 1480 upper 
and lower bulkhead and longeron splice fitting; repair, if necessary; 
and modification of the skin splice plate, the outer chord splice 
fitting, and the stringer interface of the lower bulkhead, if 
necessary. This action would revise the applicability of the existing 
AD to add additional airplanes, require accomplishment of previously 
optional inspections and clarify those inspections, extend certain 
compliance times, and require additional work in certain areas. This 
proposal is prompted by reports that fatigue cracking has been found in 
the outer chord of the BS 1480 bulkhead at the overwing longeron splice 
on airplanes not subject to the existing AD. The actions specified in 
this proposed AD are intended to detect and correct fatigue cracking of 
the outer chord of the BS 1480 upper and lower bulkhead and longeron 
splice fitting, which could result in reduced structural integrity of 
the fuselage and the inability to carry limit load.

DATES: Comments must be received by December 26, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-283-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. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 98-NM-283-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.

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.

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-283-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-283-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On September 15, 1998, the FAA issued AD 98-20-25, amendment 39-
10791 (63 FR 50508, September 22, 1998), applicable to certain Boeing 
Model 747-100 series airplanes, to require repetitive inspections to 
detect cracking of the outer chord of the body station (BS) 1480 upper 
and lower bulkhead and longeron splice fitting, and repair, if 
necessary. Alternatively, that action requires other repetitive 
inspections to detect cracking of the BS 1480 upper and lower bulkhead, 
bulkhead outer chord, web, skin, splice components, and lower bulkhead/
stringer interface; and modification of the skin splice plate, the 
outer chord splice fitting, and the stringer interface of the lower 
bulkhead, if necessary. That action was prompted by a report indicating 
that fatigue cracking was found in the outer chord of the BS 1480 
bulkhead at the overwing longeron splice, and that the longeron splice 
fitting was completely severed. The requirements of that AD are 
intended to detect and correct such fatigue cracking, which could 
result in reduced structural integrity of the fuselage and the 
inability to carry limit load.

Actions Since Issuance of Previous Rule

    Since the issuance of AD 98-20-25, the FAA has determined that the 
detailed visual inspections described in paragraph (a)(1) of that AD as 
one alternative for compliance with that AD may not be adequate to 
ensure that any fatigue cracking will be detected in a timely manner. 
Therefore, this action proposes to require detailed visual, ultrasonic, 
and open-hole high

[[Page 67312]]

frequency eddy current (HFEC) inspections which were referenced in 
paragraph (a)(2) of AD 98-20-25 as another alternative for compliance 
with that AD.
    Paragraph (a)(2) of AD 98-20-25 specifies repetitive inspections of 
both the upper and lower bulkhead, bulkhead outer chord, web, skin, 
splice components, and lower bulkhead/stringer interface. The initial 
inspection is required prior to the accumulation of 10,000 total flight 
cycles, or within 45 days after October 7, 1998 (the effective date of 
AD 98-20-25), whichever occurs later. Since the issuance of AD 98-20-
25, the FAA has determined that it is appropriate to extend the 
inspection threshold for the inspection of the bulkhead outer chord, 
skin, and lower bulkhead/stringer interface. The FAA finds that a 
repetitive inspection threshold of 20,000 total flight cycles for 
inspection of the lower bulkhead/stringer interface is adequate to 
ensure the continued safety of the affected airplanes.

Explanation of New Relevant Service Information

    Since the issuance of AD 98-20-25, the FAA has reviewed and 
approved Boeing Alert Service Bulletin 747-53A2390, Revision 1; 
including Appendices A, B, C, and D; dated July 6, 2000. (AD 98-20-25 
references the original issue of that service bulletin, dated July 31, 
1997, as an appropriate source of service information.) Like the 
original issue of the service bulletin, Revision 1 describes procedures 
for repetitive inspections to detect cracking of the BS 1480 upper and 
lower bulkhead, bulkhead outer chord, web, skin, splice components, and 
lower bulkhead/stringer interface; repair, if necessary; and, as part 
of a certain inspection plan, procedures for modification of the skin 
splice plate, outer chord splice fitting, and the stringer interface of 
the lower bulkhead. Revision 1 of the service bulletin expands the 
effectivity listing specified in the original issue of the service 
bulletin to include Model 747-400 series airplanes up to line number 
1254, includes new instructions for inspection and modification at 
stringer S-34 in the lower bulkhead/stringer interface area, revises 
inspection procedures for airplanes with a reinforcement strap 
installed on the bulkhead outer chord, and references new repair 
instructions.

Explanation of Applicability

    In the preamble to AD 98-20-25, the FAA specified that the actions 
required by that AD were considered ``interim action'' and that the FAA 
was considering further rulemaking action to supersede that AD to 
require inspections and modification of the upper and lower bulkhead 
and overwing longeron at BS 1480 for all Boeing Model 747-100, -200, 
and -300 series airplanes. The FAA has determined that further 
rulemaking is indeed necessary; this proposed AD follows from that 
determination.
    In addition, as specified previously, Revision 1 of the service 
bulletin adds Boeing Model 747-400 series airplanes up to line number 
1254 to the effectivity listing. The area of the outer chord of the BS 
1480 upper bulkhead on Model 747-400 series airplanes up to and 
including line number 1096 is essentially the same as that on other 
Boeing Model 747 series airplanes. Therefore, this proposed AD would 
require the same inspections of the upper bulkhead for Boeing Model 
747-400 series airplanes up to and including line number 1096 as it 
would require for other Boeing Model 747 series airplanes. Improvements 
were made during production on the upper bulkhead area on Model 747-400 
series airplanes having line numbers 1097 through 1254 inclusive; 
however, the lower bulkhead area on those airplanes is also essentially 
the same as on other Model 747 series airplanes. Therefore, this 
proposed AD also would require the same inspections of the lower 
bulkhead for Boeing Model 747-400 series airplanes up to and including 
line number 1254 as it would require for other Boeing Model 747 series 
airplanes. Improvements were made during production on the lower 
bulkhead area on Model 747-400 series airplanes having line number 1255 
and above, so those airplanes are not subject to this proposed AD.

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 98-20-25 to continue to require 
repetitive inspections to detect cracking of the outer chord of the BS 
1480 upper and lower bulkhead and longeron splice fitting; repair, if 
necessary; and modification of the skin splice plate, the outer chord 
splice fitting, and the stringer interface of the lower bulkhead, if 
necessary. This proposed AD would require accomplishment of the actions 
specified in Revision 1 of the service bulletin described previously, 
except as discussed below.

Differences Between Service Bulletin and Proposed AD

    Operators should note that, although the service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, this proposed AD would require 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.

Explanation of Changes Made to AD 98-20-25

    Paragraph (a)(2) of this AD is essentially a restatement of 
paragraph (a)(2) of AD 98-20-25; however, the FAA has revised paragraph 
(a)(2) of this proposed AD to more accurately state the inspections 
included in that paragraph. The inspections specified in paragraph 
(a)(2) of this proposed AD are the same as those specified in paragraph 
(d) of this proposed AD. Thus, an operator who has inspected an 
airplane in accordance with paragraph (a)(2) of this AD is not required 
to inspect in accordance with paragraphs (c) and (d) of this AD.
    In addition, the FAA has added a note to the proposed rule to 
clarify the definition of a detailed visual inspection.

Cost Impact

    There are approximately 1,128 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 259 airplanes of U.S. 
registry would be affected by this proposed AD.
    AD 98-20-25 applies to airplanes listed in Groups 1 through 3 of 
the service bulletin. The detailed visual inspection that is currently 
offered as one alternative for compliance with AD 98-20-25 takes 
approximately 16 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 $960 per airplane, per inspection cycle.
    For airplanes listed in Groups 1 through 3 in the service bulletin 
(34 U.S.-registered airplanes), the proposed detailed visual, 
ultrasonic, and open hole HFEC inspections of the upper bulkhead area 
(which AD 98-20-25 references as an alternative inspection program) 
would take approximately 32 work hours per airplane to accomplish, at 
an average labor rate of $60 per work hour. Based on these figures, the 
cost

[[Page 67313]]

impact of these proposed inspections on U.S. operators is estimated to 
be $65,280, or $1,920 per airplane, per inspection cycle.
    For airplanes listed in Groups 4 through 22 in the service bulletin 
(191 U.S.-registered airplanes), the proposed detailed visual, 
ultrasonic, and open hole HFEC inspections of the upper bulkhead area 
would take approximately 22 work hours per airplane to accomplish, at 
an average labor rate of $60 per work hour. Based on these figures, the 
cost impact of these inspections on U.S. operators is estimated to be 
$252,120, or $1,320 per airplane, per inspection cycle.
    For all airplanes listed in the applicability of this proposed AD 
(259 U.S.-registered airplanes), the proposed detailed visual, 
ultrasonic, and open hole HFEC inspections of the lower bulkhead/
stringer interface area would take approximately 30 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of these proposed inspections 
on U.S. operators is estimated to be $466,200, or $1,800 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. 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.

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 39-10791 (63 FR 
50508, September 22, 1998), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 98-NM-283-AD. Supersedes AD 98-20-25, Amendment 39-
10791.

    Applicability: Model 747 series airplanes, line numbers (L/N) 1 
through 1254 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 in the outer chord of the 
body station (BS) 1480 bulkhead at the overwing longeron splice, 
which could result in reduced structural integrity of the fuselage 
and the inability to carry limit load, accomplish the following:

Restatement of Requirements of AD 98-20-25:

Repetitive Inspections and Repair

    (a) For Model 747-100 series airplanes, L/N 1 through 87 
inclusive: Prior to the accumulation of 10,000 total flight cycles, 
or within 45 days after October 7, 1998 (the effective date of AD 
98-20-25, amendment 39-10791), whichever occurs later, accomplish 
either paragraph (a)(1) or (a)(2) of this AD.
    (1) Perform a detailed visual inspection to detect cracking of 
the longeron splice fitting at BS 1480, the forward side of the 
outer chord of the BS 1480 bulkhead at the longeron splice fitting 
attachment bolts, and the aft side of the outer chord of the BS 1480 
bulkhead within two inches above the outer chord splice fitting, on 
both the left and right sides of the airplane.

    Note 2: Figure 5 of Boeing Alert Service Bulletin 747-53A2390, 
dated July 31, 1997, provides an exploded view of the structural 
components of the splice area for the purpose of parts 
identification. (However, paragraph (a)(1) of this AD does not 
require the inspection described in Figure 5.)


    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.''

    (i) 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; 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.
    (ii) Repeat the detailed visual inspection thereafter at 
intervals not to exceed 250 flight cycles, until the initial 
inspection required by paragraph (a)(2) or (d) of this AD is 
accomplished.
    (2) Perform detailed visual, ultrasonic, and open hole high 
frequency eddy current (HFEC) inspections to detect cracking of the 
upper and lower bulkhead, bulkhead outer chord, web, skin, splice 
components, and lower bulkhead/stringer interface, in accordance 
with Figures 5 and 8 of Boeing Alert Service Bulletin 747-53A2390, 
dated July 31, 1997. Additionally, for airplanes on which the 
inspection in ``Plan B'' of the service bulletin is accomplished, 
modify the skin splice plate, the outer chord splice fitting, and 
the stringer interface of the lower bulkhead, in accordance with the 
Accomplishment Instructions of the service bulletin. Accomplishment 
of these actions constitutes terminating action for the repetitive 
inspection requirements of paragraph (a)(1) of this AD.
    (i) If any cracking is detected, prior to further flight, repair 
in accordance with the service bulletin, except as provided by 
paragraph (b) of this AD.
    (ii) Repeat the inspections thereafter in accordance with the 
flight safety inspection

[[Page 67314]]

program specified in Figures 1 and 3 of the service bulletin.
    (b) Where the service bulletin specifies that the manufacturer 
may be contacted for disposition of certain repair conditions, 
repair in accordance with a method approved by the Manager, Seattle 
ACO; or in accordance with 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.

New Requirements of This AD

Groups 1 Through 3: Splice Area Work (Compliance Times)

    Note 4: Airplanes inspected in accordance with paragraph (a)(2) 
of this AD are not required to be inspected in accordance with 
paragraphs (c) and (d) of this AD.

    (c) For airplanes listed in Groups 1 through 3 in Boeing Alert 
Service Bulletin 747-53A2390, Revision 1; including Appendices A, B, 
C, and D; dated July 6, 2000; on which the requirements of paragraph 
(a)(2) of this AD have NOT been accomplished prior to the effective 
date of this AD: Accomplish paragraph (d) of this AD at the 
applicable time specified in paragraph (c)(1), (c)(2), or (c)(3) of 
this AD.
    (1) For airplanes on which the inspection specified in Boeing 
Service Bulletin 747-53-2333 has not been accomplished: Inspect 
prior to the accumulation of 10,000 total flight cycles, or within 
1,000 flight cycles after the effective date of this AD, whichever 
occurs later.
    (2) For airplanes on which the inspection specified in Boeing 
Service Bulletin 747-53-2333 has been accomplished, but the full 
modification specified in that service bulletin has not been 
accomplished: Inspect at the later of the times specified in 
paragraphs (c)(2)(i) and (c)(2)(ii) of this AD.
    (i) Prior to the accumulation of 10,000 total flight cycles, or 
within 2,000 flight cycles after accomplishment of the last 
inspection in accordance with Boeing Service Bulletin 747-53-2333, 
whichever occurs first.
    (ii) Within 1,000 flight cycles after the effective date of this 
AD.
    (3) For airplanes on which the full modification specified in 
Boeing Service Bulletin 747-53-2333 has been accomplished: Inspect 
at the later of the times specified in paragraphs (c)(3)(i) and 
(c)(3)(ii) of this AD.
    (i) Prior to the accumulation of 16,000 total flight cycles, or 
within 6,000 flight cycles after accomplishment of the full 
modification in accordance with Boeing Service Bulletin 747-53-2333, 
whichever occurs first.
    (ii) Within 1,000 flight cycles after the effective date of this 
AD.

Groups 1 Through 3: Splice Area Work (Inspections)

    (d) For airplanes listed in Groups 1 through 3 in Boeing Alert 
Service Bulletin 747-53A2390, Revision 1; including Appendices A, B, 
C, and D; dated July 6, 2000; on which the requirements of paragraph 
(a)(2) of this AD have NOT been accomplished prior to the effective 
date of this AD: At the applicable time specified in paragraph (c) 
of this AD, accomplish paragraph (d)(1) or (d)(2) of this AD. 
Accomplishment of the requirements of this paragraph constitutes 
terminating action for the repetitive inspection requirements 
specified in paragraph (a)(1) of this AD, or, for the upper bulkhead 
splice area ONLY, for the inspection requirements specified in 
paragraph (a)(2) of this AD.
    (1) Plan ``A'': Perform detailed visual, ultrasonic, and HFEC 
inspections to detect cracking of the splice area, in accordance 
with Plan ``A'' and Figure 5, as defined in the Accomplishment 
Instructions of Boeing Alert Service Bulletin 747-53A2390, Revision 
1; including Appendices A, B, C, and D; dated July 6, 2000. Repeat 
the inspections thereafter in accordance with the flight safety 
inspection program as specified under Plan ``A'' and Figure 1 of the 
service bulletin.
    (2) Plan ``B'': Modify the skin splice plate and outer chord 
splice fitting in accordance with Plan ``B,'' as defined in the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
53A2390, Revision 1; including Appendices A, B, C, and D; dated July 
6, 2000. Perform HFEC inspections and modification, then accomplish 
repeat open hole HFEC inspections, in accordance with the flight 
safety inspection program, as specified under Plan ``B'' and Figure 
1 of the service bulletin. Accomplishment of the modification and 
inspections in accordance with this paragraph terminates the 
repetitive inspection requirements in paragraph (d)(1) of this AD.

Groups 4 Through 22: Splice Area Work (Compliance Time and Inspections)

    (e) For airplanes listed in Groups 4 though 22 in Boeing Alert 
Service Bulletin 747-53A2390, Revision 1; including Appendices A, B, 
C, and D; dated July 6, 2000: Prior to the accumulation of 16,000 
total flight cycles, or within 1,000 flight cycles after the 
effective date of this AD, whichever occurs later, perform detailed 
visual and ultrasonic inspections to detect cracking of the bulkhead 
forward flange in accordance with Figure 7 of the service bulletin, 
and accomplish the requirements of either paragraph (e)(1) or (e)(2) 
of this AD.
    (1) Plan ``A'': Perform open hole HFEC inspections to detect 
cracking of the splice area, in accordance with Plan ``A'' and 
Figures 6 and 7, as defined in the Accomplishment Instructions of 
the service bulletin. Repeat the inspections thereafter in 
accordance with the flight safety inspection program as specified 
under Plan ``A'' and in Figure 2 of the service bulletin.
    (2) Plan ``B'': Perform open hole HFEC inspections and 
modification of the upper bulkhead, bulkhead outer chord, web, skin, 
and splice components; in accordance with Plan ``B,'' as defined in 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
747-53A2390, Revision 1; including Appendices A, B, C, and D; dated 
July 6, 2000. Thereafter, repeat the open hole HFEC inspections in 
accordance with the flight safety inspection program as specified 
under Plan ``B'' and Figure 2 of the service bulletin. 
Accomplishment of the modification and inspections in accordance 
with this paragraph terminates the repetitive inspection 
requirements specified in paragraph (e)(1) of this AD.

All Airplanes: Lower Bulkhead/Stringer Interface Work (Compliance 
Times)

    (f) For all airplanes (L/N 1 through 1254 inclusive): At the 
applicable time specified in paragraph (f)(1) or (f)(2) of this AD, 
accomplish paragraph (g) of this AD.
    (1) For airplanes on which an inspection of the lower bulkhead 
has NOT been accomplished prior to the effective date of this AD in 
accordance with paragraph (a)(2) of this AD: Inspect prior to the 
accumulation of 20,000 total flight cycles, or within 1,000 flight 
cycles after the effective date of this AD, whichever occurs later.
    (2) For airplanes on which an inspection of the lower bulkhead 
HAS been accomplished prior to the effective date of this AD in 
accordance with paragraph (a)(2) of this AD: Inspect prior to the 
accumulation of 20,000 total flight cycles, or at the time of the 
next scheduled inspection of the lower bulkhead in accordance with 
paragraph (a)(2) of this AD, whichever occurs later.

All Airplanes: Lower Bulkhead/Stringer Interface Work (Inspections)

    (g) For all airplanes (L/N 1 through 1254 inclusive): At the 
applicable time specified in paragraph (f) of this AD, accomplish 
paragraph (g)(1) or (g)(2) of this AD. For airplanes having L/N 1 
through 87 inclusive, accomplishment of the requirements of this 
paragraph constitutes terminating action for the inspection 
requirements specified in paragraph (a)(2) of this AD for the lower 
bulkhead/stringer interface area ONLY.
    (1) Plan ``A'': Perform detailed visual and either ultrasonic or 
open hole HFEC inspections, as applicable, to detect cracking of the 
lower bulkhead/stringer interface area, in accordance with Plan 
``A'' and Figure 8, as defined in the Accomplishment Instructions of 
Boeing Alert Service Bulletin 747-53A2390, Revision 1; including 
Appendices A, B, C, and D; dated July 6, 2000. Repeat the 
inspections thereafter in accordance with the flight safety program 
as specified under Plan ``A'' and Figure 3 or Figure 8 of the 
service bulletin.
    (2) Plan ``B'': Except as provided by paragraph (h) of this AD, 
perform open hole HFEC inspections and modification of the lower 
bulkhead/stringer interface area, in accordance with Plan ``B'' and 
Figure 19, as defined in the Accomplishment Instructions of Boeing 
Alert Service Bulletin 747-53A2390, Revision 1; including Appendices 
A, B, C, and D; dated July 6, 2000. Thereafter, repeat the detailed 
visual and either ultrasonic or open hole HFEC inspections, as 
applicable, in accordance with the flight safety inspection program 
as specified under Plan ``B'' and Figures 3 and 8 of the service 
bulletin. Accomplishment of the modification and inspections in 
accordance with this paragraph terminates the repetitive inspection 
requirements specified in paragraph (g)(1) of this AD.

[[Page 67315]]

Airplanes Modified With Original Service Bulletin: Post-Modification 
Work

    (h) For any airplane (L/N 1 through 1254 inclusive) on which the 
modification specified in paragraph (g)(2) was accomplished prior to 
the effective date of this AD in accordance with the original issue 
of Boeing Alert Service Bulletin 747-53A2390, dated July 31, 1997: 
Prior to the accumulation of 20,000 total flight cycles, or within 
2,000 flight cycles after the effective date of this AD, whichever 
occurs later, accomplish post-modification work in accordance with 
Figure 26 of Boeing Alert Service Bulletin 747-53A2390, Revision 1; 
including Appendices A, B, C, and D; dated July 6, 2000.

Repair

    (i) Except as provided by paragraph (b) of this AD, if any 
cracking is detected during any inspection required by this AD, 
prior to further flight, repair in accordance with Boeing Alert 
Service Bulletin 747-53A2390, Revision 1; including Appendices A, B, 
C, and D; dated July 6, 2000.

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 98-20-25, amendment 39-10791, are approved as 
alternative methods of compliance with paragraph (a) of this AD.

    Note 5: 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 
Secs. 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 November 2, 2000,
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-28723 Filed 11-8-00; 8:45 am]
BILLING CODE 4910-13-P