[Federal Register Volume 69, Number 214 (Friday, November 5, 2004)]
[Proposed Rules]
[Pages 64534-64537]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-24721]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2004-19533; Directorate Identifier 2004-NM-31-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
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 737-300, -400, and -500 series airplanes. This 
proposed AD would require repetitive inspections for cracking of the 
crown area of the fuselage skin, and corrective actions, if necessary. 
This proposed AD is prompted by a 737 fuselage structure test and 
fatigue analysis that indicate fuselage skin cracking could occur 
between 21,000 and 42,000 total flight cycles. We are proposing this AD 
to detect and correct fatigue cracking of the fuselage skin, which 
could cause the fuselage skin to fracture and fail, and could result in 
rapid decompression of the airplane.

DATES: We must receive comments on this proposed AD by December 20, 
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://dms.dot.gov, or in person 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. This docket 
number is FAA-2004-19533; the directorate identifier for this docket is 
2004-NM-31-AD.

FOR FURTHER INFORMATION CONTACT: 
    Technical Information: 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.
    Plain Language Information: Marcia Walters, [email protected].

SUPPLEMENTARY INFORMATION: 

[[Page 64535]]

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-2004-19533; 
Directorate Identifier 2004-NM-31-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 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.
    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 a.m. and 5 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 the results of a 737 fuselage structure test and 
fatigue analysis conducted by the airplane manufacturer. The results 
indicate that fatigue cracking is expected to occur between body 
station (BS) 360 and BS 1016 common to the chem-milled step of the 
upper skin above the S-4 and S-10 lap joints, when the airplane 
accumulates between 21,000 to 42,000 total flight cycles. This kind of 
cracking is caused by fatigue from high bending stresses at the edge of 
the chem-milled step. This condition, if not detected and corrected, 
could cause the fuselage skin to fracture and fail, and could result in 
rapid decompression of the airplane.

Other Related Rulemaking

    On August 26, 2004, we issued AD 2004-18-06, amendment 39-13784 (69 
FR 54206, September 8, 2004), applicable to certain Boeing Model 737-
200, -200C, -300, -400, and -500 series airplanes, which requires 
repetitive inspections to find fatigue cracking of certain upper and 
lower skin panels of the fuselage, and follow-on and corrective 
actions, if necessary. That AD was prompted by reports indicating that 
cracks were found along the edges of the chem-milled pockets in the 
upper skin at stringer S-12, and above the S-4, S-10, and S-14 lap 
joints, on several Boeing Model 737 series airplanes. The actions 
required by that AD are intended to find and fix fatigue cracking of 
the skin panels, which could result in sudden fracture and failure of 
the skin panels of the fuselage, and consequent rapid decompression of 
the airplane. AD 2004-18-06 does not affect the requirements of this 
AD.

Relevant Service Information

    We have reviewed Boeing Special Attention Service Bulletin 737-53-
1234, dated June 13, 2002, which describes doing repetitive external 
detailed and eddy current inspections for cracking of the crown area of 
the fuselage skin just above the S-4 and S-14 lap joints from station 
360 to station 1016, and doing either the permanent repair or a time-
limited repair. Doing either repair ends the repetitive inspections for 
the repaired area. The service bulletin specifies that the inspections 
are not necessary in certain areas and to contact Boeing if certain 
repairs are found.
    The permanent repair, which is subject to certain limitations, 
consists of the following related investigative and corrective actions:
    1. Doing eddy current inspections of the fuselage skin for 
cracking;
    2. Doing detailed inspections of the fastener holes common to the 
lower row/remaining rows of fasteners in the lap joint for cracking;
    3. Doing general visual, detailed, and eddy current inspections of 
the skin and lap joint for cracking, corrosion, or disbonding;
    4. Contacting Boeing for repair if any cracking, corrosion, or 
disbonding is found or if Hi-locks, lockbolts, or bolts are installed 
in the area of a crack; and
    5. Reporting any cracking to Boeing.
    The time-limited repair, which is subject to certain limitations, 
consists of the following related investigative and corrective actions:
    1. Doing external detailed inspections of the skin in each adjacent 
bay in the area of chem-milled step for cracks;
    2. Doing external detailed inspections of the skin and lap joint in 
the area of the repair for corrosion or disbonding; and
    3. Contacting Boeing for repair if any cracking, corrosion, or 
disbonding is found.
    If the time-limited repair is done, the service bulletin describes 
doing these related investigative and corrective actions at times 
varying from 3,000 flight cycles to 10,000 flight cycles after the 
time-limited repair is done:
    1. Doing repetitive general visual inspections for loose or missing 
fasteners;
    2. Replacing missing or loose fasteners with new fasteners;
    3. Doing one-time inspections of the skin and lap joint of the 
repaired area for cracking or corrosion (includes doing a general 
visual inspection of the lap joint for corrosion and eddy current 
inspections of the skin and the skin under the tear strap for 
cracking);
    4. Contacting Boeing for repair if any cracking or corrosion is 
found; and
    5. Doing a permanent modification of the time-limited repair 
(includes doing detailed inspections of the fastener holes for 
cracking, doing a detailed inspection of the skin for corrosion or 
disbonded doublers; and contacting Boeing for any applicable repair). 
Doing a permanent modification ends the need for the repetitive general 
visual inspections for the repaired area only.
    The service bulletin recommends the following approximate 
compliance times for the initial detailed and eddy

[[Page 64536]]

current inspections: Within 21,000 to 42,000 total flight cycles, 
depending on the applicable site of the fuselage skin; or within 4,500 
cycles after release of this service bulletin; whichever is later.

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 repetitive inspections for cracking of the crown area of 
the fuselage skin, and permanent or time-limited repair if necessary. 
The proposed AD would require you to use the service information 
described previously to perform these actions, except as discussed 
under ``Differences Between the Proposed AD and the Service Bulletin.''

Differences Between the Proposed AD and the 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 that have been approved by a Boeing Company Designated 
Engineering Representative who has been authorized by the FAA to make 
such findings.
    You should note that, although the service bulletin describes 
procedures for reporting information to the manufacturer, this proposed 
AD would not require those actions. We do not need this information.

Interim Action

    This is considered to be interim action until final action is 
identified, at which time we may consider further rulemaking.

Costs of Compliance

    There are about 579 airplanes of the affected design in the 
worldwide fleet. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD.

                                                                     Estimated Costs
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                                                                                                           Cost per
                                                                                       Average labor    airplane, per   Number of U.S.-  Fleet cost, per
                               Action                                   Work hours     rate per hour      inspection       registered       inspection
                                                                                                            cycle          airplanes          cycle
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Inspections........................................................              94              $65           $6,110              175       $1,069,250
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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-2004-19533; Directorate Identifier 2004-NM-
31-AD.

Comments Due Date

    (a) The Federal Aviation Administration (FAA) must receive 
comments on this AD action by December 20, 2004.

Affected ADs

    (b) None.
    Applicability: (c) This AD applies to Boeing Model 737-300, -
400, and -500 series airplanes, certificated in any category; as 
listed in Boeing Special Attention Service Bulletin 737-53-1234, 
dated June 13, 2002.

Unsafe Condition

    (d) This AD was prompted by a 737 fuselage structure test and 
fatigue analysis that indicate fuselage skin cracking could occur 
between 21,000 and 42,000 total flight cycles. We are issuing this 
AD to detect and correct fatigue cracking of the fuselage skin, 
which could cause the fuselage skin to fracture and fail, and could 
result in 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.

Service Bulletin References

    (f) The term ``service bulletin,'' as used in this AD, means 
Boeing Special Attention Service Bulletin 737-53-1234, dated June 
13, 2002.

Initial and Repetitive Inspections

    (g) At the later of the times specified in paragraphs (g)(1) and 
(g)(2) of this AD, perform detailed and eddy current inspections for 
cracking of the crown area of the fuselage skin in accordance with 
Part 1, including the ``Note,'' of the Work Instructions of the 
service bulletin, except as provided by paragraph (j) of this AD.
    (1) Before the accumulation of the applicable total flight 
cycles specified in the ``Threshold'' column of Table 1 of Figure 1 
of the service bulletin.
    (2) Within 4,500 flight cycles after the effective date of this 
AD.
    (h) Repeat either the detailed or eddy current inspections 
specified in paragraph (g) of this AD at the applicable intervals 
specified in paragraph (h)(1) or (h)(2) of this AD until paragraph 
(i)(1) or (i)(2) of this AD has been done, as applicable.
    (1) Repeat the detailed inspections thereafter at intervals not 
to exceed 1,200 flight cycles.
    (2) Repeat the eddy current inspections thereafter at intervals 
not to exceed 3,000 flight cycles.

Permanent or Time-Limited Repair

    (i) If any cracking is found during any inspection required by 
paragraph (g) or (h) of this AD, do the actions specified in 
paragraph (i)(1) or (i)(2) of this AD in accordance with the service 
bulletin, except as provided by paragraphs (j) and (k) of this AD.

[[Page 64537]]

    (1) Before further flight, do a permanent repair (including 
related investigative actions and applicable corrective actions) in 
accordance with Part 2, including the ``Note,'' of the Work 
Instructions of the service bulletin. Doing a permanent repair ends 
the repetitive inspections required by paragraph (h) of this AD for 
the repaired area only.
    (2) Do the actions specified in paragraphs (i)(2)(i) and 
(i)(2)(ii) of this AD at the time specified in the applicable 
paragraph. Doing a time-limited repair ends the repetitive 
inspections required by paragraph (h) of this AD for the repaired 
area only.
    (i) Before further flight, do a time-limited repair (including 
related investigative actions and applicable corrective actions) in 
accordance with Part 3, including the ``Note,'' of the Work 
Instructions of the service bulletin.
    (ii) At the times specified in Figure 8 of the service bulletin, 
do the related investigative and corrective actions in accordance 
with Part 3, including the ``Note,'' of the Work Instructions of the 
service bulletin.

Contact the FAA

    (j) Where the service bulletin specifies to contact Boeing for 
appropriateaction: 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 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.

No Reporting

    (k) Although the service bulletin specifies reporting certain 
information to Boeing, this AD does not require that action.

Alternative Methods of Compliance (AMOCs)

    (l) The Manager, Seattle ACO, FAA, has the authority to approve 
AMOCs for this AD, if requested using the procedures found in 14 CFR 
39.19.

    Issued in Renton, Washington, on October 26, 2004.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-24721 Filed 11-4-04; 8:45 am]
BILLING CODE 4910-13-P