[Federal Register Volume 69, Number 171 (Friday, September 3, 2004)]
[Proposed Rules]
[Pages 53855-53858]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-20124]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2004-18996; Directorate Identifier 2004-NM-40-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-700 and -800 Series 
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 737-700 and -800 series airplanes. This 
proposed AD would require doing an initial inspection for pitting and 
cracks of the lower skin panel at the lap joint; trimming the inner 
skin; installing exterior doublers; replacing the fuselage skin 
assembly; doing repetitive supplemental inspections; and repairing if 
necessary; as applicable. This proposed AD is prompted by a report 
indicating that localized pitting in the lower skin panels was found 
during production on a limited number of airplanes. We are proposing 
this AD to detect and correct premature fatigue cracking at certain lap 
splice locations and consequent rapid decompression of the airplane.

DATES: We must receive comments on this proposed AD by October 18, 
2004.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking web site: Go to http://www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, 
Washington, DC 20590.
     By fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    For service information identified in this proposed AD, contact 
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-
2207.
    You can examine the contents of this AD docket on the Internet at 
http://

[[Page 53856]]

dms.dot.gov, or at the Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street, SW., room PL-401, on the plaza 
level of the Nassif Building, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Sue Lucier, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6438; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

    The FAA has implemented new procedures for maintaining AD dockets 
electronically. As of May 17, 2004, new AD actions are posted on DMS 
and assigned a docket number. We track each action and assign a 
corresponding directorate identifier. The DMS AD docket number is in 
the form ``Docket No. FAA-2004-99999.'' The Transport Airplane 
Directorate identifier is in the form ``Directorate Identifier 2004-NM-
999-AD.'' Each DMS AD docket also lists the directorate identifier 
(``Old Docket Number'') as a cross-reference for searching purposes.

Comments Invited

    We invite you to submit any written relevant data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed under ADDRESSES. Include ``Docket No. FAA-2004-18996; 
Directorate Identifier 2004-NM-40-AD'' in the subject line of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments submitted by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that website, anyone can find and read the comments in any of our 
dockets, including the name of the individual who sent the comment (or 
signed the comment on behalf of an association, business, labor union, 
etc.). You can review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
can visit http://dms.dot.gov.
    We are reviewing the writing style we currently use in regulatory 
documents. We are interested in your comments on whether the style of 
this document is clear, and your suggestions to improve the clarity of 
our communications that affect you. You can get more information about 
plain language at http://www.faa.gov/language and http://www.plainlanguage.gov.

Examining the Docket

    You can examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office 
between 9:00 a.m. and 5:00 p.m., Monday through Friday, except Federal 
holidays. The Docket Management Facility office (telephone (800) 647-
5227) is located on the plaza level of the Nassif Building at the DOT 
street address stated in the ADDRESSES section. Comments will be 
available in the AD docket shortly after the DMS receives them.

Discussion

    We have received a report indicating that localized pitting in the 
lower skin panels was found during production on a limited number of 
Boeing Model 737-700 and -800 series airplanes. The pitting was caused 
by chemical milling solution leaking through sealer at a maskant line. 
The leakage caused local pits to form on the surface of the skin. 
Testing and analysis revealed that the chemical mill pitting does not 
reduce the ultimate strength of the effected skin panels, but chemical 
mill pitting greater than the allowable limit may reduce the fatigue 
performance and damage tolerance capability of the lower skin panels. 
This condition, if not corrected, could result in premature fatigue 
cracking at certain lap splice locations and consequent rapid 
decompression of the airplane.

Relevant Service Information

    We have reviewed Boeing Service Bulletin 737-53-1256, dated 
September 18, 2003, which describes the following procedures depending 
on the airplane configuration:
     Doing an initial external ultrasonic inspection for 
pitting and cracks of the lower skin panel at the lap joint;
     Trimming the inner skin and installing two exterior 
doublers (including an internal high frequency eddy current inspection 
of the edge of the trim for cracks) or installing three exterior 
doublers, as applicable;
     Replacing the fuselage skin assembly with a new assembly;
     Doing supplemental repetitive inspections; and
     Contacting Boeing for repair of discrepancies.
    The service bulletin recommends compliance times at the following 
approximate intervals, depending on the lap splice location:

                              Table--Service Bulletin Recommended Compliance Times
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               Action                                         Recommended compliance time
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Initial inspection..................  Ranging from 28,000 to 75,000 total flight cycles.
Initial supplemental inspection.....  56,000 flight cycles after repair incorporation.
Repetitive supplemental inspections.  Ranging from 5,000 to 7,500 flight cycles.
----------------------------------------------------------------------------------------------------------------

    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. Therefore, we are proposing this AD, which 
would require you to use the service information described previously 
to perform the required actions, except as discussed under ``Difference 
Between the Proposed AD and Service Bulletin.''

Difference Between the Proposed AD and Service Bulletin

    The service bulletin specifies that you may contact the 
manufacturer for instructions on how to repair certain conditions, but 
this proposed AD would require you to repair those conditions in one of 
the following ways:
     Using a method that we approve; or
     Using data that meet the type certification basis of the 
airplane, and

[[Page 53857]]

that have been approved by a Boeing Company Designated Engineering 
Representative who has been authorized by the FAA to make those 
findings.

Costs of Compliance

    This proposed AD would affect about 4 airplanes worldwide and 2 
airplanes of U.S. registry. The following table provides the estimated 
costs to comply with this proposed AD.

The average labor rate is $65 per work hour. The cost impact of the 
proposed AD on U.S. operators is estimated to be $83,855.

                                               Table--Cost Impact
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For airplanes listed in the referenced service                                                     Per airplane
              bulletin as group--                          Work hours               Parts cost         cost
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1.............................................  Inspection: 2...................            None            $130
                                                Modification: 38................            $105           2,575
2.............................................  Inspection: 2...................            None             130
                                                Modification: 30................             104           2,054
3.............................................  Inspection: 2...................            None             130
                                                Modification: 42................             106           2,836
4.............................................  Repair: 920.....................          16,200          76,000
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Regulatory Findings

    We have determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD 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.
    For the reasons discussed above, I certify that the 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. 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD. See the ADDRESSES section for a location 
to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The FAA amends Sec.  39.13 by adding the following new 
airworthiness directive (AD):

Boeing: Docket No. FAA-2004-18996; Directorate Identifier 2004-NM-
40-AD.

Comments Due Date

    (a) The Federal Aviation Administration (FAA) must receive 
comments on this AD action by October 18, 2004.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-700 and -800 series 
airplanes, certificated in any category; having variable and serial 
numbers listed in Table 1 of this AD.

            Table 1.--Applicable Variable and Serial Numbers
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             Variable No.--                Serial No.--       Group--
------------------------------------------------------------------------
YA004...................................           27837               1
YA005...................................           27836               2
YA201...................................           28004               4
YC003...................................           27977               3
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Unsafe Condition

    (d) This AD was prompted by a report indicating that localized 
pitting in the lower skin panels was found during production on a 
limited number of airplanes. We are issuing this AD to detect and 
correct premature fatigue cracking at certain lap splice locations 
and consequent rapid decompression of the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Initial Inspection and/or Repair

    (f) At the applicable times specified in Table 1 of paragraph 
1.E., ``Compliance'' of Boeing Service Bulletin 737-53-1256, dated 
September 18, 2003, do the applicable actions specified in Table 2 
of this AD in accordance with the Accomplishment Instructions of the 
service bulletin.

               Table 2.--Initial Inspection and/or Repair
------------------------------------------------------------------------
 For airplanes identified in
  the service bulletin as--                  Requirements--
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(1) Groups 1, 2, and 3.......  Do an external ultrasonic inspection for
                                pitting and cracks of the lower skin
                                panel at the lap joint.
(2) Groups 1 and 2...........  Trim the inner skin and install two
                                exterior doublers (including related
                                investigative actions).

[[Page 53858]]

 
(3) Group 3..................  Install three exterior doublers.
(4) Group 4..................  Replace the fuselage skin assembly with a
                                new assembly.
------------------------------------------------------------------------

Repetitive Inspections

    (g) For Groups 1, 2, and 3 airplanes identified in Boeing 
Service Bulletin 737-53-1256, dated September 18, 2003: At the 
applicable times specified in Table 2 of paragraph 1.E., 
``Compliance'' of the service bulletin, do the repetitive 
supplemental inspections of the lower skins and external doublers 
for discrepancies in accordance with the Accomplishment Instructions 
of the service bulletin.

Corrective Action

    (h) If any discrepancy is found during any action required by 
this AD, 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.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by a 
Boeing Company DER who has been authorized by the Manager, Seattle 
ACO, to make those findings. For a repair method to be approved, the 
approval must specifically refer to this AD.

    Issued in Renton, Washington, on August 20, 2004.
Kevin M. Mullin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-20124 Filed 9-2-04; 8:45 am]
BILLING CODE 4910-13-P