[Federal Register Volume 64, Number 6 (Monday, January 11, 1999)]
[Proposed Rules]
[Pages 1549-1552]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-481]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-11-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 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 737 series 
airplanes. This proposal would require inspections of certain bonded 
skin panel assemblies to detect delamination of the skin doublers (tear 
straps) from the skin panels; and follow-on corrective actions, if 
necessary. This proposal is prompted by reports indicating that certain 
skin doublers were delaminated from their skin panels due to improper 
processing of certain skin panels. The actions specified by the 
proposed AD are intended to detect and correct such delamination, which 
could result in fatigue cracks in the skin doublers and skin panels, 
and consequent rapid decompression of the airplane.

DATES: Comments must be received by February 25, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-11-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 98-NM-11-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-11-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that skin doublers (tear 
straps) were found delaminated from their skin panels on certain Boeing 
Model 737 series airplanes. These airplanes had accumulated as few as 
10,200 total flight cycles. The subject skin doublers and skin panels 
are installed above stringer S-26 from body station (BS) 259 to BS 1016 
on both sides of the airplane. The cause of such delamination in all 
incidents has been attributed to improper processing during the 
phosphoric anodize application of the skin panels. This condition, if 
not detected and corrected, could result in fatigue cracks in the skin 
doublers and skin panels, and consequent rapid decompression of the 
airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-53-
1179, dated June 22, 1995, as revised by Notice of Status Change (NSC) 
737-53-1179 NSC 1, dated August 17, 1995, which describes procedures 
for performing a one-time internal inspection (terminating inspection) 
of the bonded skin panel assemblies to detect delamination of the skin 
doublers from the skin panels; and follow-on corrective actions, if 
necessary.
    The above inspection includes an internal close visual inspection 
(Figure 3 of the service bulletin), an internal close visual inspection 
while trying to separate the skin doublers from the skin panels (Figure 
3 of the service bulletin), and an ultrasonic inspection (Figure 4 of 
the service bulletin). The service bulletin recommends that operators 
perform these inspections on bonded skin panel assemblies, which are 
composed of skin doublers (tear straps) that are bonded to skin panels 
located above stringer S-26 from BS 259 to BS 1016 on both sides of the 
airplane. In lieu of accomplishing the internal close visual 
inspections of bonded skin panel assemblies (Figure 3 of the service 
bulletin), the service bulletin describes procedures for performing an 
internal or external ultrasonic inspection to detect delamination.
    The follow-on corrective actions include internal close visual, low 
frequency eddy current, and high frequency eddy current inspections; 
and repair, if necessary. The service bulletin recommends that 
operators perform such inspections to detect corrosion and cracks that 
may have resulted from any skin doubler delaminating from its skin 
panel.
    The service bulletin also describes procedures for performing 
repetitive external visual inspections (interim inspection) to detect 
cracks in skin panels; and repair, if necessary. This service bulletin 
recommends that operators perform the external visual inspections until 
accomplishment of the one-time internal inspection described 
previously.
    Boeing has also issued NSC 737-53-1179 NSC 1, dated August 17, 
1995. This NSC contains no new technical information but corrects two 
typographical errors and adds a general note.

[[Page 1550]]

    Accomplishment of the actions specified in the service bulletin and 
the NSC are intended to adequately address the identified unsafe 
condition.

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 service bulletin and the NSC described previously, except as 
discussed below.

Differences Between Proposed Rule and Service Bulletin

    Operators should note that, although the service bulletin 
recommends accomplishing a one-time internal inspection (terminating 
inspection), as described previously, prior to the accumulation of 
40,000 total flight cycles or within 20,000 flight cycles after the 
release of the service bulletin, whichever occurs later, the FAA has 
determined that such a compliance time would not address the identified 
unsafe condition in a timely manner. As described previously, operators 
have found doublers delaminated from skin panels on certain Boeing 
Model 737 series airplanes that had accumulated as few as 10,200 total 
flight cycles. The FAA has determined that to have a high probability 
of detecting cracking before it reaches a critical length, the 
inspections described previously must be accomplished prior to the 
accumulation of 20,000 total flight cycles. In developing an 
appropriate compliance time for this proposed AD, the FAA considered 
not only the manufacturer's recommendation, but the degree of urgency 
associated with addressing the subject unsafe condition, the average 
utilization of the affected fleet, and the time necessary to perform 
the one-time inspection (136 work hours). In light of all of these 
factors, the FAA finds that a proposed compliance time of 20,000 total 
flight cycles, or 4,500 flight cycles or 18 months after the effective 
date of this AD, whichever occurs later, for initiating the proposed 
actions to be warranted. The FAA has determined that the proposed 
compliance time represents an appropriate interval of time allowable 
for affected airplanes to continue to operate without compromising 
safety.
    For those operators that elect to perform repetitive external 
visual inspections (i.e., the interim inspection), the service bulletin 
recommends accomplishing the one-time inspections within 20,000 flight 
cycles (after the release of the service bulletin). For the same 
reasons stated above, the FAA has determined that such a compliance 
time would not address the identified unsafe condition in a timely 
manner. Therefore, the FAA finds that a proposed compliance time of 
15,000 flight cycles or 60 months after the effective date of this 
proposed AD, whichever occurs first, for initiating the proposed 
actions [i.e., the one-time (terminating) inspection] to be warranted. 
The FAA has determined that the proposed compliance time represents an 
appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.
    Operators also should note that the service bulletin does not 
specify that the one-time inspection be accomplished after airplanes 
accumulate 4,500 flight cycles on certain bonded skin panel assemblies. 
Service history indicates that the bonded skin panel assemblies on the 
affected airplanes need to be subjected to a minimal amount of loading 
and environment before disbonding becomes detectable. For this reason, 
the FAA finds a 4,500 flight cycle interval to be an appropriate 
interval of time for ensuring that the operators are able to detect 
delamination of the skin doublers from the skin panels. Therefore, the 
proposed AD requires that the one-time inspection be performed after 
the affected airplanes accumulate 4,500 total flight cycles or after 
the affected airplanes accumulate 4,500 flight cycles after the date of 
installation of any new or serviceable bonded skin panel assembly.
    Although the effectivity listing of the service bulletin includes 
airplanes having line numbers 611 through 2725 inclusive, the 
applicability of this proposed AD includes airplanes having line 
numbers 1 through 3072 inclusive. The service bulletin does not specify 
that operators perform an inspection of any new or serviceable bonded 
skin panel assembly that was installed prior to October 1, 1997, on any 
airplane having line numbers 1 through 3072 inclusive. The FAA has 
determined that the identified unsafe condition could exist or develop 
on those airplanes having such replacement bonded skin panel 
assemblies. In light of this, the FAA finds that it is necessary that 
the applicability of this proposed AD include Boeing Model 737 series 
airplanes on which the bonded skin panel assemblies were replaced with 
any new or serviceable bonded skin panel assemblies prior to October 1, 
1997. Therefore, the applicability of this proposed AD includes line 
numbers 1 through 3072 inclusive.
    Operators should note that, although the service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, this proposal 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 Manager, 
Seattle Aircraft Certification Office, to make such findings.
    Additionally, the service bulletin specifies that certain actions 
may be accomplished in accordance with ``an equivalent'' procedure. 
However, this proposed AD requires that those actions be accomplished 
in accordance with the procedures specified in Part 6, Subject 51-00-
00, Figure 4, of the 737 Nondestructive Test Manual. An ``equivalent'' 
procedure may be used only if approved as an alternative method of 
compliance in accordance with the provisions of paragraph (j) of the 
proposed AD.

Cost Impact

    There are approximately 2,083 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 863 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 136 work hours per airplane to 
accomplish the proposed terminating inspection, at an average labor 
rate of $60 per work hour. Based on these figures, the cost impact of 
the terminating inspection proposed by this AD on U.S. operators is 
estimated to be $7,042,080, or $8,160 per airplane.
    It would take approximately 32 work hours per airplane to 
accomplish the proposed interim inspection, at an average labor rate of 
$60 per work hour. Based on these figures, the cost impact of the 
interim inspection proposed by this AD on U.S. operators is estimated 
to be $1,656,960, or $1,920 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

[[Page 1551]]

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 98-NM-11-AD.

    Applicability: Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes, line numbers 1 through 3072 inclusive, certified 
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) 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.

    Note 2: Where there are differences between this AD and the 
referenced service bulletin, the AD prevails.

    Compliance: Required as indicated, unless accomplished 
previously.
    To detect and correct delamination of the skin doublers (tear 
straps) from the skin panels, which could result in fatigue cracks 
in the skin doublers and the skin panels, and consequent rapid 
decompression of the airplane, accomplish the following:
    (a) For airplanes having line numbers 611 through 2725 
inclusive, on which any bonded skin panel assembly has not been 
replaced with any new or serviceable bonded skin panel assembly: 
Accomplish the actions required either by paragraph (a)(1) of this 
AD, or by both paragraphs (a)(2) and (a)(3) of this AD, in 
accordance with Boeing Service Bulletin 737-53-1179, dated June 22, 
1995, as revised by Notice of Status Change 737-53-1179 NSC 1, dated 
August 17, 1995.

    Note 3: For the purposes of this AD, bonded skin panel 
assemblies consist of skin doublers (tear straps) that are bonded to 
skin panels located above stringer S-26 from body station (BS) 259 
to BS 1016 on both sides of the airplane.

    Note 4: If the skin panel is solid with no doublers (tear 
straps) bonded to it, the inspections required by this AD are not 
necessary for that skin panel.

    (1) Prior to the accumulation of 20,000 total flight cycles, but 
after the accumulation of 4,500 total flight cycles; or within 18 
months or 4,500 flight cycles after the effective date of this AD; 
whichever occurs latest; perform a one-time internal inspection 
(terminating inspection) of the bonded skin panel assemblies to 
detect delamination of the skin doublers from the skin panels, in 
accordance with Figures 3 and 4 of the service bulletin. In lieu of 
accomplishing the inspections specified in Figure 3 of the service 
bulletin, operators can perform an internal or external ultrasonic 
inspection in accordance with Note 1. of paragraph A. of the 
``Terminating Inspection'' Section of the Accomplishment 
Instructions of the service bulletin.

    Note 5: For the purposes of this AD, the one-time internal 
inspection includes an internal close visual inspection (Figure 3), 
an internal close visual inspection while trying to separate the 
skin doublers from the skin panels (Figure 3), and an ultrasonic 
inspection (Figure 4).

    (2) Within 4,500 flight cycles or 18 months after the effective 
date of this AD, whichever occurs later, perform an external visual 
inspection of the bonded skin panel assemblies to detect cracks in 
the skin panels, in accordance with paragraph A. of the ``Interim 
Inspection'' Section of the Accomplishment Instructions of the 
service bulletin. Repeat the external visual inspection thereafter 
at intervals not to exceed 4,500 flight cycles, until accomplishment 
of the requirements specified in paragraph (a)(3) of this AD.
    (3) Within 15,000 flight cycles or 60 months after the effective 
date of this AD, whichever occurs first, accomplish the one-time 
internal inspection required by paragraph (a)(1) of this AD. 
Accomplishment of this action constitutes terminating action for the 
repetitive inspections required by paragraph (a)(2) of this AD.
    (b) For airplanes having line numbers 611 through 2725 
inclusive, on which any bonded skin panel assembly was replaced with 
any new or serviceable bonded skin panel assembly prior to October 
1, 1997: Accomplish the actions required by both paragraphs (b)(1) 
and (b)(2) of this AD, or by both paragraphs (b)(3) and (b)(4) of 
this AD, in accordance with Boeing Service Bulletin 737-53-1179, 
dated June 22, 1995, as revised by Notice of Status Change 737-53-
1179 NSC 1, dated August 17, 1995.
    (1) Prior to the accumulation of 20,000 total flight cycles, but 
after the accumulation of 4,500 total flight cycles; or within 4,500 
flight cycles or 18 months after the effective date of this AD; 
whichever occurs latest; perform a one-time internal inspection 
(terminating inspection) of the bonded skin panel assemblies that 
have not been replaced to detect delamination of the skin doublers 
from the skin panels, in accordance with Figures 3 and 4 of the 
service bulletin. In lieu of accomplishing the inspections specified 
in Figure 3 of the service bulletin, operators can perform an 
internal or external ultrasonic inspection in accordance with Note 
1. of paragraph A. of the ``Terminating Inspection'' Section of the 
Accomplishment Instructions of the service bulletin.
    (2) Prior to the accumulation of 20,000 flight cycles after the 
date of replacement of the skin panel assembly, but not prior to the 
accumulation of 4,500 flight cycles after the date of such 
replacement; or within 4,500 flight cycles or 18 months after the 
effective date of this AD; whichever occurs latest; perform a one-
time internal inspection (terminating inspection) of the bonded skin 
panel assemblies that have been replaced to detect delamination of 
the skin doublers from the skin panels, in accordance with Figures 3 
and 4 of the service bulletin. In lieu of accomplishing the 
inspections identified in Figure 3 of the service bulletin, 
operators can perform an internal or external ultrasonic inspection 
in accordance with Note 1. of paragraph A. of the ``Terminating 
Inspection'' Section of the Accomplishment Instructions of the 
service bulletin.
    (3) Within 4,500 flight cycles or 18 months after the effective 
date of this AD, whichever occurs later, perform an external visual 
inspection of the skin panel assemblies that have and have not been 
replaced to detect cracks in the skin panels, in accordance with 
paragraph A. of the ``Interim Inspection'' Section of the 
Accomplishment Instructions of the service bulletin. Repeat the 
external visual inspection thereafter at intervals not to exceed 
4,500 flight cycles, until accomplishment of the requirements 
specified in paragraph (b)(4) of this AD.
    (4) Within 15,000 flight cycles or 60 months after the effective 
date of this AD, whichever occurs first, accomplish the one-time 
internal inspection required by both paragraphs (b)(1) and (b)(2) of 
this AD. Accomplishment of this action constitutes terminating 
action for the repetitive inspections required by paragraph (b)(3) 
of this AD.
    (c) For airplanes having line numbers 611 through 2725 
inclusive, on which any

[[Page 1552]]

bonded skin panel assembly was replaced with any new or serviceable 
bonded skin panel assembly after September 30, 1997: Accomplish the 
actions required either by paragraph (c)(1) or by both paragraphs 
(c)(2) and (c)(3) of this AD, in accordance with Boeing Service 
Bulletin 737-53-1179, dated June 22, 1995, as revised by Notice of 
Status Change 737-53-1179 NSC 1, dated August 17, 1995.
    (1) Prior to the accumulation of 20,000 total flight cycles, but 
not prior to the accumulation of 4,500 total flight cycles; or 
within 4,500 flight cycles or 18 months after the effective date of 
this AD; whichever occurs latest; perform a one-time internal 
inspection (terminating inspection) of the bonded skin panel 
assemblies that have not been replaced to detect delamination of the 
skin doublers from the skin panels, in accordance with Figures 3 and 
4 of the service bulletin. In lieu of accomplishing the inspections 
identified in Figure 3 of the service bulletin, operators can 
perform an internal or external ultrasonic inspection in accordance 
with NOTE 1. of paragraph A. of the ``Terminating Inspection'' 
Section of the Accomplishment Instructions of the service bulletin.
    (2) Within 4,500 flight cycles or 18 months after the effective 
date of this AD, whichever occurs later, perform an external visual 
inspection of the bonded skin panel assemblies that have not been 
replaced to detect cracks in the skin panels, in accordance with 
paragraph A. of the ``Interim Inspection'' Section of the 
Accomplishment Instructions of the service bulletin. Repeat the 
external visual inspection thereafter at intervals not to exceed 
4,500 flight cycles, until accomplishment of the requirements 
specified in paragraph (c)(3) of this AD.
    (3) Within 15,000 flight cycles or 60 months after the effective 
date of this AD, whichever occurs first, accomplish the one-time 
internal inspection required by paragraph (c)(1) of this AD. 
Accomplishment of this action constitutes terminating action for the 
repetitive inspections required by paragraph (c)(2) of this AD.
    (d) For airplanes having line numbers 1 through 610 inclusive, 
and 2726 through 3072 inclusive, on which any bonded skin panel 
assembly was replaced with any new or serviceable bonded skin panel 
assembly prior to October 1, 1997: Accomplish the actions required 
either by paragraph (d)(1) or by both paragraphs (d)(2) and (d)(3) 
of this AD, in accordance with Boeing Service Bulletin 737-53-1179, 
dated June 22, 1995, as revised by Notice of Status Change 737-53-
1179 NSC 1, dated August 17, 1995.
    (1) Prior to the accumulation of 20,000 flight cycles after the 
date of replacement of the skin panel assembly, but not prior to the 
accumulation of 4,500 flight cycles after the date of such 
replacement; or within 4,500 flight cycles or 18 months after the 
effective date of this AD; whichever occurs latest; perform a one-
time internal inspection (terminating inspection) of the bonded skin 
panel assemblies that have been replaced to detect delamination of 
the skin doublers from the skin panels, in accordance with Figures 3 
and 4 of the service bulletin. In lieu of accomplishing the 
inspections specified in Figure 3 of the service bulletin, operators 
can perform an internal or external ultrasonic inspection in 
accordance with NOTE 1. of paragraph A. of the ``Terminating 
Inspection'' Section of the Accomplishment Instructions of the 
service bulletin.
    (2) Within 4,500 flight cycles or 18 months after the effective 
date of this AD, whichever occurs later, perform an external visual 
inspection of the bonded skin panel assemblies that have been 
replaced to detect cracks in the skin panels, in accordance with 
paragraph A. of the Interim Inspection of the Accomplishment 
Instructions of the service bulletin. Repeat the external visual 
inspection thereafter at intervals not to exceed 4,500 flight 
cycles, until accomplishment of the requirements specified in 
paragraph (d)(3) of this AD.
    (3) Within 15,000 flight cycles or 60 months after the effective 
date of this AD, whichever occurs first, accomplish the one-time 
internal inspection required by paragraph (d)(1) of this AD. 
Accomplishment of this action constitutes terminating action for the 
repetitive inspections required by paragraph (d)(2) of this AD.
    (e) If any crack is detected during any inspection required by 
paragraph (a)(2), (b)(3), (c)(2), or (d)(2) of this AD, prior to 
further flight, accomplish the actions required by paragraph (b)(1) 
and (b)(2) of this AD, as applicable.
    (1) If any crack is detected in any skin panel that is above 
stringer S-10 or between stringers S-14 and S-26, repair in 
accordance with Boeing Service Bulletin 737-53-1179, dated June 22, 
1995, as revised by Notice of Status Change 737-53-1179 NSC 1, dated 
August 17, 1995.
    (2) If any crack is detected in any skin panel that is between 
stringers S-10 and S-14 (window belt), repair in accordance with a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate; or in accordance 
with data meeting the type certification basis of the airplane 
approved by a Boeing Company Designated Engineering Representative 
who has been authorized by the Manager, Seattle ACO, to make such 
findings.
    (f) If no delamination is detected during any inspection 
required by paragraph (a)(1), (a)(3), (b)(1), (b)(2), (b)(4), 
(c)(1), (c)(3), (d)(1), or (d)(3) of this AD, no further action is 
required by this AD.
    (g) If any delamination is detected during any inspection 
required by paragraph (a)(1), (a)(3), (b)(1), (b)(2), (b)(4), 
(c)(1), (c)(3), (d)(1), or (d)(3) of this AD, prior to further 
flight, accomplish the actions required by either paragraph (g)(1) 
or (g)(2) of this AD, as applicable.
    (1) If the delaminated area is less than 3 square inches and is 
not at the edge of a skin doubler or under a fastener head, no 
further action is required by this AD for that delaminated area.
    (2) If the delaminated area is equal to or greater than 3 square 
inches or is located at the edge of a skin doubler or under a 
fastener head, prior to further flight, accomplish the follow-on 
corrective actions in accordance with the ``Terminating Inspection'' 
Section of the Accomplishment Instructions of Boeing Service 
Bulletin 737-53-1179, dated June 22, 1995, as revised by Notice of 
Status Change 737-53-1179 NSC 1, dated August 17, 1995, except as 
provided by paragraphs (h) and (i) of this AD.
    (h) Where Boeing Service Bulletin 737-53-1179, dated June 22, 
1995, as revised by Notice of Status Change 737-53-1179 NSC 1, dated 
August 17, 1995, specifies that the actions required by this AD may 
be accomplished in accordance with an ``equivalent'' procedure, the 
actions must be accomplished in accordance with the chapter of the 
Boeing 737 Nondestructive Test Manual specified in the service 
bulletin.
    (i) Where Boeing Service Bulletin 737-53-1179, dated June 22, 
1995, as revised by Notice of Status Change 737-53-1179 NSC 1, dated 
August 17, 1995, specifies that the repair of a delaminated lap 
splice is to be accomplished in accordance with instructions 
received from Boeing, this AD requires that the repair be 
accomplished 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 
Designated Engineering Representative who has been authorized by the 
Manager, Seattle ACO, to make such findings.
    (j) 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 6: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (k) 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 December 31, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-481 Filed 1-8-99; 8:45 am]
BILLING CODE 4910-13-U