[Federal Register Volume 68, Number 80 (Friday, April 25, 2003)]
[Rules and Regulations]
[Pages 20341-20344]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-10115]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2002-NM-329-AD; Amendment 39-13128; AD 2003-08-15]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200, -200C, -300, -
400, and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 737-200, -200C, -300, -400, and -
500 series airplanes. This action requires a one-time mid-frequency 
eddy current (MFEC), a low-frequency eddy current (LFEC), and a 
detailed inspection for damage or cracking of stringer S-4L and S-4R 
lap joints and stringer clips between body station (BS) 540 and BS 727, 
and follow-on inspections and repair if necessary. This action is 
necessary to find and fix cracking of the fuselage lap joints, which 
could result in sudden decompression of the airplane.

DATES: Effective May 12, 2003.
    The incorporation by reference of Boeing Alert Service Bulletin 
737-53A1255, dated October 17, 2002, as listed in the regulations, is 
approved by the Director of the Federal Register as of May 12, 2003.
    The incorporation by reference of Boeing Service Bulletin 737-
53A1177, Revision 6, dated May 31, 2001, as listed in the regulations, 
was approved previously by the Director of the Federal Register as of 
May 17, 2002 (67 FR 17917, April 12, 2002).
    Comments for inclusion in the Rules Docket must be received on or 
before June 24, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2002-NM-329-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2002-NM-329-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 this AD 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; or at 
the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Duong Tran, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6452; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Related AD

    On April 2, 2002, the FAA issued AD 2002-07-08, amendment 39-12702 
(67 FR 17917, April 12, 2002), applicable to certain Boeing Model 737 
series airplanes. That AD specifies Boeing Service Bulletin (SB) 737-
53A1177, Revision 6, dated May 31, 2001, as an appropriate source of 
service information for that AD. That AD requires repetitive 
inspections to find cracking of the lower skin at the lower row of 
fasteners in the lap joints of the fuselage, and repair of any cracking 
found. That AD also requires modification of the fuselage lap joints at 
certain locations, which constitutes terminating action for certain 
repetitive inspections of the modified areas. Additionally, that AD 
requires repetitive inspections and requires replacement of a certain 
preventive modification with an improved modification. That AD was 
prompted by our determination that, in light of crack findings, certain 
modifications of the fuselage lap joints do not provide an adequate 
level of safety. The actions specified by that AD are intended to find 
and fix cracking of the fuselage lap joints, which could result in 
sudden decompression of the airplane.

Since the Issuance of That AD

    We have received a report indicating that, during a walk-around 
inspection on a Model 737-200 series airplane with 60,333 total flight 
cycles, a 23-inch-long crack was found in the lower row of the stringer 
S-4L lap joint between body station (BS) 616 and BS 639. The crack was 
noticed above the over-wing exit because the lower skin was pushed 
outward approximately 1 inch with the crack ends turning downward at 
the tear straps. The flight crew did not report any pressurization 
problems, and the passengers and cabin crew did not report any abnormal 
noise in that area. Further external and internal non-destructive 
testing methods for cracking of the lap joint revealed additional 
cracking. The possible extent of cracking both forward and aft of the 
23-inch-long cracked section is a concern. Cracks were found in between 
the tear straps and in the skin locations common to the tear straps. 
The intact tear straps were able to turn the cracks as they were 
designed to do; however, due to the condition of the skin at the tear 
straps forward and aft of the 23-inch crack area, it is likely that 
similar crack link-up just forward in an area that had a higher 
percentage of cracked fastener holes could have resulted in an 
uncontained decompression. Of particular concern is the total number 
and length of cracks found at that particular lap joint. The damage 
found apparently exceeds all prior in-service crack findings and also 
exceeds the

[[Page 20342]]

manufacturer's crack growth predictions based on test and analysis for 
an airplane with 60,000 total flight cycles.
    Additionally, we received a report of significant cracking on 
stringer S-4R of the lap joint between BS 600 and BS 727 on a Model 
737-300 series airplane having 52,400 total flight cycles. Although the 
individual cracks had not linked up, it was clear that, within a 
limited number of flights, the cracking could have linked up with a 
length of over 10 inches. Those cracks were detected by performing a 
low-frequency eddy current (LFEC) and a medium-frequency eddy current 
(MFEC) inspection. Such cracking, if not corrected, could result in 
sudden decompression of the airplane.

Explanation of Relevant Service Information

    We have reviewed and approved Boeing Alert Service Bulletin (ASB) 
737-53A1255, dated October 17, 2002. The ASB describes procedures for 
performing an internal detailed inspection, and MFEC and LFEC 
inspections for damage and cracking of the stringer S-4L and S-4R lap 
joints and stringer clips between BS 540 and BS 727. If no damage or 
cracking is found, the ASB advises operators to continue the lap joint 
repetitive inspections as specified in Boeing SB 737-53A1177, Revision 
6, dated May 31, 2001 (referenced in AD 2002-07-08 as an appropriate 
source of service information for that AD). Boeing ASB 737-53A1255 also 
describes procedures for performing an external sliding probe 
inspection or internal MFEC and LFEC inspections for cracking that is 
defined as ``significant'' in the ASB. Boeing ASB 737-53A1255 also 
describes an optional open hole non-destructive testing inspection that 
may be used in addition to the MFEC, LFEC, and detailed inspections to 
confirm crack indications. Additionally, Boeing ASB 737-53A1255 
specifies that the repair of any cracked lap joints be done per Boeing 
SB 737-53A1177, Revision 6, dated May 31, 2001. Also, Boeing ASB 737-
53A1255 describes procedures for replacing any broken or damaged 
stringer clips. Boeing ASB 737-53A1255 also requests that operators 
report certain information resulting from the inspection findings, such 
as the type of inspection method used and the inspection results, a 
description of any damage or cracking found, the airplane serial 
number, and the number of current flight cycles and flight hours on the 
airplane.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to find and fix cracking of the fuselage lap joints, which 
could result in sudden decompression of the airplane. This AD requires 
accomplishment of the actions specified in the service bulletins 
described previously, except as discussed below.

Differences Between ASB and This AD

    If cracking or damage is found per Boeing ASB 737-53A1255, dated 
October 17, 2002, that ASB references Boeing SB 737-53A1177, Revision 
6, dated May 31, 2001, for procedures to repair any cracking or damage 
that may be found. Operators should note that this AD also will require 
repair of cracking or damage that is within the limits specified in 
Boeing SB 737-53A1177, Revision 6, dated May 31, 2001, per that service 
bulletin. However, this AD requires that, for any damage or cracking 
that is found to be outside the limits specified in Boeing SB 737-
53A1177, Revision 6, dated May 31, 2001, repair must be accomplished 
per a method approved by the FAA, or per data meeting the type 
certification basis of the airplane approved by a Boeing Company 
Designated Engineering Representative who has been authorized by the 
FAA to make such findings.
    In addition, Boeing ASB 737-53A1255, dated October 17, 2002, 
specifies that, if no cracking or damage is found, operators should 
repeat the lap joint inspections specified in Boeing ASB 737-53A1177. 
This AD, however, requires only the one-time inspections and, if no 
damage or cracking is found, operators need only to accomplish the 
reporting requirements of this AD. (Detailed inspections required by 
this AD do not replace, but are in addition to the repetitive 
inspections required by AD 2002-07-08, amendment 39-12702.)
    Operators also should note that Boeing ASB 737-53A1255 does not 
recommend the internal mid-frequency MFEC, LFEC, or detailed 
inspections described in the ASB for airplanes with less than 45,000 
total flight cycles. However, this AD requires those inspections (and 
repair if necessary) on airplanes prior to the accumulation of 45,000 
total flight cycles or within 90 days after the effective date of this 
AD, whichever occurs later. We consider that the identified unsafe 
condition must be addressed for all airplanes when 45,000 total flight 
cycles have been accumulated. Requiring a specific compliance time for 
those airplanes addresses that issue.

Interim Action

    This is considered to be interim action. The inspection reports 
that are required by this AD will enable the manufacturer to obtain 
better insight into the nature, cause, and extent of the cracking, and 
eventually to develop final action to address the unsafe condition. 
Once final action has been identified, we may consider further 
rulemaking.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Submit comments using the following format:
    [sbull] Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    [sbull] For each issue, state what specific change to the AD is 
being requested.
    [sbull] Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that

[[Page 20343]]

summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2002-NM-329-AD.'' The postcard will be date stamped 
and returned to the commenter.

Regulatory Impact

    The regulations adopted herein will 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 final rule does not have federalism 
implications under Executive Order 13132.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from the Rules Docket at the 
location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. Section 39.13 is amended by adding the following new airworthiness 
directive:

2003-08-15 Boeing: Amendment 39-13128. Docket 2002-NM-329-AD.

    Applicability: Model 737-200, -200C, -300, -400, and -500 series 
airplanes, having line numbers 292 through 2552 inclusive, and on 
which the modification specified in Boeing Service Bulletin (SB) 
737-53A1177, Revision 6, dated May 31, 2001, has not been 
accomplished; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (h) 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 find and fix cracking of the fuselage lap joints, which could 
result in sudden decompression of the airplane, accomplish the 
following:

    Note 2: Detailed inspections required by this AD do not replace, 
but are in addition to the repetitive inspections required by AD 
2002-07-08, amendment 39-12702.

One-Time Inspections

    (a) With the exception of any area of any lap joints that are 
specified in this paragraph that have previously been repaired or 
modified per Boeing SB 737-53A1177, Revision 4, dated September 2, 
1999; Revision 5, dated February 15, 2001; and Revision 6, dated May 
31, 2001: Perform an internal mid-frequency eddy current (MFEC), a 
low-frequency eddy current (LFEC), and a detailed inspection for 
damage or cracking on stringers S-4L and S-4R lap joints between 
body station (BS) 540 and BS 727; and perform a detailed inspection 
for damage of the stringer clips at all frame locations at stringers 
S-4L and S-4R between BS 540 and BS 727 at the applicable time 
specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD; per the 
Accomplishment Instructions of Boeing Alert Service Bulletin (ASB) 
737-53A1255, dated October 17, 2002. If no damage or cracking is 
found, no further action is required by this paragraph.

    Note 3: For the purposes of this AD, a detailed 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.''

    (1) For airplanes that have accumulated less than 45,000 total 
flight cycles as of the effective date of this AD: Perform the 
inspections prior to the accumulation of 45,000 total flight cycles 
or within 90 days after the effective date of this AD, whichever 
occurs later.
    (2) For airplanes that have accumulated 45,000 total flight 
cycles but not more than 49,999 total flight cycles as of the 
effective date of this AD: Perform the inspections within 90 days 
after the effective date of this AD.
    (3) For airplanes that have accumulated 50,000 total flight 
cycles or more as of the effective date of this AD: Perform the 
inspections within 45 days after the effective date of this AD.
    (b) The optional accomplishment of an open-hole non-destructive 
testing (NDT) inspection per Boeing ASB 737-53A1255, dated October 
17, 2002, is acceptable as a method of verification of any cracking 
of the fastener holes found during the inspections required by 
paragraph (a) of this AD.
    (c) If any damage or cracking is found during the inspections 
required by paragraph (a), (b), (d), or (e) of this AD that is not 
``significant,'' as defined in Boeing ASB 737-53A1255, dated October 
17, 2002, repair per paragraph (c)(1) or (c)(2) of this AD, as 
applicable.
    (1) For cracking that is within the limits specified by Boeing 
SB 737-53A1177, Revision 6, dated May 31, 2001: Before further 
flight, repair per the Accomplishment Instructions of Boeing SB 737-
53A1177, Revision 6, dated May 31, 2001; and before further flight, 
replace any damaged stringer clips with a new part, per Boeing ASB 
737-53A1255, dated October 17, 2002.
    (2) For any cracking that exceeds the limits specified in Boeing 
SB 737-53A1177, Revision 6, dated May 31, 2001: Before further 
flight, repair per a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA; or per data meeting the 
type certification basis of the airplane approved by a Boeing 
Company Designated Engineering Representative (DER) who has been 
authorized by the Manager, Seattle ACO, to make such findings. For a 
repair method to be approved, the approval must specifically 
reference this AD.
    (d) If any damage or cracking is found during the inspections 
required by paragraphs (a), (b), (d), or (e) of this AD that is 
``significant,'' as defined in Boeing ASB 737-53A1255, dated October 
17, 2002: Before further flight, accomplish the actions specified by 
paragraph (d)(1) or (d)(2) of this AD, per the Accomplishment 
Instructions of the ASB.
    (1) With the exception of BS 540 through 727 inclusive: Perform 
an external sliding probe inspection for damage or cracking, per 
Figure 2 of Boeing ASB 737-53A1255, dated October 17, 2002, for each 
model (Model 737-200, -200C, -300, -400, and -500 series airplanes) 
at the applicable locations specified in the Compliance Section of 
Boeing SB 737-53A1177, Revision 6, dated May 31, 2001.
    (2) With the exception of BS 540 through 727 inclusive: Perform 
internal MFEC, LFEC, and detailed inspections for damage or 
cracking, per Figure 1 of Boeing ASB 737-53A1255, dated October 17, 
2002, for each model (Model 737-200, -200C, -300, -400,

[[Page 20344]]

and -500 series airplanes) at the applicable locations specified in 
the Compliance Section of Boeing SB 737-53A1177, Revision 6, dated 
May 31, 2001.
    (e) If any ``significant'' cracking, as defined in Boeing ASB 
737-53A1255, dated October 17, 2002, is found in any lap joint 
during the external inspection required by paragraph (d) of this AD: 
Before further flight, accomplish the actions required by paragraphs 
(e)(1) and (e)(2) of this AD.
    (1) Perform internal MFEC, LFEC, and detailed inspections for 
cracking of the entire affected section of the lap joint, specified 
in the Compliance Section and Inspection Zone Figures of Boeing SB 
737-53A1177, Revision 6, dated May 31, 2001; per Boeing ASB 737-
53A1255, dated October 17, 2002.
    (2) Perform a detailed inspection for damage of the stringer 
clips and replace any damaged stringer clip with a new part, per 
Boeing ASB 737-53A1255, dated October 17, 2002.
    (f) If any cracking, ``significant'' (as defined in Boeing ASB 
737-53A1255, dated October 17, 2002) or otherwise, is found during 
the inspections required by paragraphs (a), (b), (d), or (e) of this 
AD: Before further flight, accomplish the actions specified by 
paragraph (f)(1) or (f)(2) of this AD, as applicable.
    (1) For cracking that is within the limits specified in Boeing 
SB 737-53A1177, Revision 6, dated May 31, 2001: Repair per the 
Accomplishment Instructions of that ASB; and replace any damaged 
stringer clips with a new part per Boeing ASB 737-53A1255, dated 
October 17, 2002.
    (2) For any cracking that exceeds the limits specified in Boeing 
SB 737-53A1177, Revision 6, dated May 31, 2001, repair per a method 
approved by the Manager, Seattle ACO; or per data meeting the type 
certification basis of the airplane approved by a Boeing Company DER 
who has been authorized by the Manager, Seattle ACO, to make such 
findings. For a repair method to be approved, the approval must 
specifically reference this AD.

Reporting Requirements

    (g) Submit a report of inspection findings (both positive and 
negative) to the Boeing Commercial Airplane Group, P.O. Box 3707, 
Seattle, Washington 98124-2207, as specified in paragraph B.10 of 
the Accomplishment Instructions of Boeing ASB 737-53A1255, dated 
October 17, 2002, at the applicable time specified by paragraph 
(g)(1) or (g)(2) of this AD. Information collection requirements 
contained in this AD have been approved by the Office of Management 
and Budget (OMB) under the provisions of the Paperwork Reduction Act 
of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control 
Number 2120-0056.
    (1) For airplanes on which the inspection required by paragraph 
(a) of this AD is accomplished after the effective date of this AD: 
Submit the report within 10 days after performing the inspection 
required by paragraph (a) of this AD.
    (2) For airplanes on which the inspection required by paragraph 
(a) of this AD has been accomplished prior to the effective date of 
this AD: Submit the report within 10 days after the effective date 
of this AD.

Alternative Methods of Compliance

    (h) 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, ACO, FAA. 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 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (i) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

Incorporation by Reference

    (j) Unless otherwise specified by this AD, the actions shall be 
done in accordance with Boeing Alert Service Bulletin 737-53A1255, 
dated October 17, 2002; and Boeing Service Bulletin 737-53A1177, 
Revision 6, dated May 31, 2001; as applicable.
    (1) This incorporation by reference of Boeing Alert Service 
Bulletin 737-53A1255, dated October 17, 2002, is approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51.
    (2) The incorporation by reference of Boeing Service Bulletin 
737-53A1177, Revision 6, dated May 31, 2001, was approved previously 
by the Director of the Federal Register as of May 17, 2002 (67 FR 
17917, April 12, 2002).
    (3) Copies may be obtained from Boeing Commercial Airplane 
Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Effective Date

    (k) This amendment becomes effective on May 12, 2003.

    Issued in Renton, Washington, on April 18, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-10115 Filed 4-24-03; 8:45 am]
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