[Federal Register Volume 72, Number 188 (Friday, September 28, 2007)]
[Proposed Rules]
[Pages 55118-55120]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-19205]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29333; Directorate Identifier 2007-NM-141-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, -700C, -
800, and -900 Series Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (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 737-600, -700, -700C, -800, and -900 series 
airplanes. This proposed AD would require various repetitive 
inspections to detect cracks along the chemically milled steps of the 
fuselage skin or missing or loose fasteners in the area of the 
preventative modification or repairs, replacement of the time-limited 
repair with the permanent repair if applicable, and applicable 
corrective actions if necessary, which would end certain repetitive 
inspections. This proposed AD results from a fatigue test that revealed 
numerous cracks in the upper skin panel at the chemically milled step 
above the lap joint. We are proposing this AD to detect and correct 
such fatigue-related cracks, which could result in the crack tips 
continuing to turn and grow to the point where the skin bay flaps open, 
causing decompression of the airplane.

DATES: We must receive comments on this proposed AD by November 13, 
2007.

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.
     Governmentwide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room W12-140 on the ground floor of the 
West Building, 1200 New Jersey Avenue, SE., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for the service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Wayne Lockett, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6447; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2007-
29333; Directorate Identifier 2007-NM-141-AD'' at the beginning 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 received 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 Web site, 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 may review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov, or in

[[Page 55119]]

person at the Docket Operations office between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays. The Docket Operations 
office (telephone (800) 647-5527) is located on the ground level of the 
West Building at the DOT street address stated in the ADDRESSES 
section. Comments will be available in the AD docket shortly after the 
Docket Management System receives them.

Discussion

    We have received a report that, during a fatigue test of the 
fuselage of a Boeing Model 737-800 series airplane, numerous cracks 
were found in the upper skin panel at the chemically milled step above 
the lap joint at stringers 4 and 10 on both the left and right sides of 
the airplane. The cracks were caused by fatigue stresses generated by 
secondary bending in the lap splice. Such fatigue-related cracks, if 
not detected and corrected in a timely manner, could result in the 
crack tips continuing to turn and grow to the point where the skin bay 
flaps open, causing decompression of the airplane.

Relevant Service Information

    We have reviewed Boeing Special Attention Service Bulletin 737-53-
1232, dated April 2, 2007. The service information describes the 
following actions:

               Inspections and Replacement, as Applicable
------------------------------------------------------------------------
                               The service bulletin describes procedures
   For airplanes on which--                   for doing--
------------------------------------------------------------------------
The preventative modification  An external eddy current inspection to
 specified in the service       detect cracks of the chemically milled
 bulletin has not been          steps at the upper skin panels and
 installed.                     repetitive external detailed inspections
                                to detect cracks of the skin.
The preventative modification  Repetitive external detailed inspections
 specified in the service       and repetitive external high frequency
 bulletin has been installed.   eddy current (HFEC) inspections to
                                detect cracks or loose or missing
                                fasteners in the area of the
                                preventative modification.
The permanent repair           Repetitive external low frequency eddy
 specified in the service       current (LFEC) inspections to detect
 bulletin has been installed.   cracks in the skin.
                               Repetitive external LFEC inspections to
                                detect cracks of the doubler.
                               Repetitive external detailed inspections
                                to detect cracks or loose or missing
                                fasteners of the permanent repair.
                               Repetitive internal medium frequency eddy
                                current inspections to detect cracks of
                                the skin if doing ``Skin Inspection
                                Option 2'' specified in Table 2 of the
                                service bulletin
The time-limited repair        Repetitive internal and external detailed
 specified in the service       inspections to detect cracks or loose or
 bulletin has been installed.   missing fasteners of the repaired area
                                and replacement of the time-limited
                                repair with the permanent repair.
------------------------------------------------------------------------

    The service information also describes procedures for doing 
applicable corrective actions. The corrective actions include 
contacting Boeing for certain conditions, replacing any loose or 
missing fastener with a new fastener, and installing a permanent 
repair, time-limited repair, and preventative modification. For 
airplanes on which the preventative modification has not been 
installed, accomplishing the preventative modification, time-limited 
repair, or permanent repair ends the repetitive external detailed 
inspections only.
    The service information also specifies the following compliance 
times:
     For the initial inspections and replacement: Compliance 
times ranging between 1,500 flight cycles and 56,000 total flight 
cycles, depending on the airplane configuration and the inspection 
method.
     For the applicable corrective actions: A compliance time 
of before further flight.
     For repetitive inspections: Repeat intervals ranging 
between 1,100 and 8,000 flight cycles, depending on the airplane 
configuration.
    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. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously, except as discussed under 
``Difference Between the Proposed AD and Service Information.''

Difference Between the Proposed AD and Service Information

    The service information specifies to contact the manufacturer for 
instructions on how to repair certain conditions, but this proposed AD 
would require repairing those conditions in one of the following ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.

Costs of Compliance

    There are about 871 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 378 airplanes of 
U.S. registry. The proposed inspections would take between 11 and 25 
work hours per airplane depending on the airplane configuration, at an 
average labor rate of $80 per work hour. Based on these figures, the 
estimated cost of the proposed AD for U.S. operators is between 
$332,640 and $756,000, or between $880 and $2,000 per airplane, per 
inspection cycle.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

[[Page 55120]]

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 and placed it in the AD docket. 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 Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-29333; Directorate Identifier 2007-NM-
141-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by November 
13, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-600, -700, -700C, -800, 
and -900 series airplanes, certificated in any category; as 
identified in Boeing Special Attention Service Bulletin 737-53-1232, 
dated April 2, 2007.

Unsafe Condition

    (d) This AD results from a fatigue test that revealed numerous 
cracks in the upper skin panel at the chemically milled step above 
the lap joint. We are issuing this AD to detect and correct such 
fatigue-related cracks, which could result in the crack tips 
continuing to turn and grow to the point where the skin bay flaps 
open, causing 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.

Service Bulletin

    (f) The term ``service bulletin,'' as used in this AD, means 
Boeing Special Attention Service Bulletin 737-53-1232, dated April 
2, 2007.

Inspections and Replacement, as Applicable

    (g) At the applicable compliance times listed in Tables 1, 2, 
and 3 of paragraph 1.E., ``Compliance,'' of the service bulletin, or 
within the time specified in paragraph (g)(1) or (g)(2) of this AD, 
as applicable, whichever occurs later, and thereafter at the 
applicable repeat intervals listed in Tables 1, 2, and 3: Do the 
applicable inspections and replacement by accomplishing all the 
actions specified in the Accomplishment Instructions of the service 
bulletin.
    (1) For airplanes specified in Tables 1 and 2 of paragraph 1.E., 
``Compliance,'' of the service bulletin: Do the applicable initial 
inspection required by paragraph (g) of this AD within 36 months 
after the effective date of this AD.
    (2) For airplanes specified in Table 3 of paragraph 1.E., 
``Compliance,'' of the service bulletin: Do the applicable initial 
inspection and replacement required by paragraph (g) of this AD 
within 24 months after the effective date of this AD.

Corrective Actions

    (h) If any crack or loose or missing fastener is found during 
any applicable inspection required by paragraph (g) of this AD, 
before further flight, do the applicable corrective action in 
accordance with the service bulletin; except, where the service 
bulletin specifies to contact Boeing for appropriate action, before 
further flight, repair the crack using a method approved in 
accordance with the procedures specified in paragraph (j) of this 
AD.

Terminating Action for Certain Repetitive Inspections

    (i) For airplanes on which the preventative modification 
specified in the service bulletin has not been installed: 
Accomplishing the preventative modification, time-limited repair, or 
permanent repair in accordance with the service bulletin ends the 
applicable repetitive external detailed inspections required by 
paragraph (g) of this AD.

Alternative Methods of Compliance (AMOCs)

    (j)(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) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who has been authorized 
by the Manager, Seattle ACO, to make those findings. For a repair 
method to be approved, the repair must meet the certification basis 
of the airplane, and the approval must specifically refer to this 
AD.

    Issued in Renton, Washington, on September 21, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-19205 Filed 9-27-07; 8:45 am]
BILLING CODE 4910-13-P