[Federal Register Volume 69, Number 172 (Tuesday, September 7, 2004)]
[Proposed Rules]
[Pages 54058-54060]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-20209]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2004-19003; Directorate Identifier 2003-NM-245-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -200C, -
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 all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes. This proposed AD would require repetitive inspections for 
cracks in the fuselage skin, doubler, bearstrap, and frames surrounding 
the main, forward, and aft cargo doors; and repair of any cracking. 
This proposed AD also would require inspections of certain existing 
repairs for cracking, and related corrective action if cracking is 
found. This proposed AD is prompted by reports of multiple fatigue 
cracks in the fuselage skin and bonded skin doubler, bearstrap, and 
doorway frames surrounding the forward and aft cargo doors. We are 
proposing this AD to find and fix fatigue cracking in the fuselage 
skin, doubler, bearstrap, and frames, which could result in reduced 
structural integrity of the frames, possible loss of a cargo door, and 
consequent rapid decompression of the fuselage.

DATES: We must receive comments on this proposed AD by October 22, 
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.

FOR FURTHER INFORMATION CONTACT:
    Technical information: Howard Hall, Aerospace Engineer, Airframe 
Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind 
Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6430; 
fax (425) 917-6590.
    Plain language information: Marcia Walters, [email protected].

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 relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed under ADDRESSES. Include ``Docket No. FAA-2004-19003; 
Directorate Identifier 2003-NM-245-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 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.

Background

    The FAA previously issued related rulemaking applicable to certain 
Boeing Model 737 series airplanes, as follows:
    AD 88-11-12, amendment 39-5890 (53 FR 18077, May 20, 1988). That AD 
requires structural inspection of the forward lower cargo doorway 
frames, and repair if necessary. That AD also requires replacement of 
certain repaired parts previously installed.
    AD 93-14-10, amendment 39-8634 (58 FR 43547, August 17, 1993). That 
AD requires structural inspections to detect cracks of the forward and 
aft body frames adjacent to the aft lower cargo door and repair of 
cracked parts, and provides an optional modification. That AD also 
requires certain repetitive inspections to continue after installation 
of the optional modification.

FAA's Determination Since Issuance of AD 88-11-12 and AD 93-14-10

    Since we issued those ADs, we have received reports of multiple 
fatigue cracks in the fuselage skin and bonded skin doubler, bearstrap, 
and doorway frames surrounding the forward and aft cargo doors on 
certain Boeing Model

[[Page 54059]]

737 series airplanes. Several cracks have also been found in the 
fuselage skin/doubler and bearstrap of the upper corners of the main 
cargo door. Additionally, during structural inspections, cracks were 
found in the bearstrap under the fuselage frame flanges at the edges of 
the forward cargo door. In two cases, cracks were found in the fuselage 
frames of the aft cargo door where steel repair doublers had been 
installed using the requirements of AD 93-14-10. In another case, 
cracks were found in the unreinforced area above the aluminum repair 
doubler, which had also been installed using the requirements of AD 93-
14-10. A recent inspection done on an airplane having 73,080 total 
flight cycles revealed cracks in the forward fuselage frame and 
adjacent skin/doubler and bearstrap of the forward cargo door. Such 
fatigue cracking, if not found and fixed, could result in reduced 
structural integrity of the frames, possible loss of a cargo door, and 
consequent rapid decompression of the fuselage.

Explanation of Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1228, dated 
July 10, 2003, which describes procedures for repetitive detailed, 
general visual, and high and low frequency eddy current inspections for 
cracks in the fuselage skin, doubler, bearstrap, and frames surrounding 
the main, forward, and aft cargo doors, and repair of any crack found. 
The service bulletin also describes procedures for repetitive 
inspections for cracks in certain existing repairs in the subject 
areas, and related corrective action.
    The corrective action includes alternative inspections or 
replacement of the repaired component, depending on the cracking damage 
found. The service bulletin recommends that operators contact Boeing 
for certain repair instructions. Accomplishment of the actions 
specified in the service bulletin is intended to adequately address the 
identified unsafe condition.
    This service bulletin recommends compliance times at the following 
approximate intervals:
    1. For the detailed and general inspections of the forward and aft 
cargo door cutouts, the inspection threshold is before the accumulation 
of 50,000 total flight cycles or within 4,000 flight cycles after 
release of the service bulletin, whichever is later. The inspections 
are repeated at intervals ranging from 4,000 flight cycles to 12,000 
flight cycles.
    2. For the detailed and high frequency eddy current (HFEC) 
inspections of the main cargo door cutout, the inspection threshold is 
before the accumulation of 20,000 total flight cycles or within 4,000 
flight cycles after release of the service bulletin, whichever is 
later. The inspections are repeated at intervals not to exceed 12,000 
flight cycles.
    3. For the detailed and HFEC inspections of the forward cargo 
doorway frame, the inspection threshold is before the accumulation of 
20,000 total flight cycles or within 4,000 flight cycles after release 
of the service bulletin, whichever is later. The inspections are 
repeated at intervals not to exceed 4,000 flight cycles.
    4. For the general visual, HFEC and low frequency eddy current 
inspections of the aft cargo doorway frame, the inspection threshold 
ranges between 20,000 and 40,000 total flight cycles or within 4,000 
flight cycles after release of the service bulletin, whichever is 
later. The inspections are repeated at intervals not to exceed 4,000 
flight cycles.
    5. If the frame is replaced, the inspection threshold starts from 
the time the frame was replaced. If the frame is repaired, the 
inspection threshold starts from the time the repair was installed, or 
the total airplane cycles if it is unknown when the repair was 
installed.

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. The proposed AD would require you to use the 
service information described previously to perform the actions, except 
as discussed under ``Differences Between the Proposed AD and Service 
Bulletin.''

Differences Between Proposed AD and Service Bulletin

    The service bulletin specifies compliance times relative to the 
date of the service bulletin; however, this proposed AD would require 
compliance within the thresholds specified in paragraph 1.E., 
``Compliance'' of the service bulletin, after the effective date of the 
AD.
    The service bulletin recommends reporting any discrepancies to the 
manufacturer; however, this proposed AD does not include that 
requirement.
    Although the service bulletin specifies that operators may contact 
the manufacturer for disposition of certain repair conditions, this 
proposed AD would require operators to repair those conditions using a 
method approved by the Manager of the Seattle Aircraft Certification 
Office of the FAA, or using 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.

Costs of Compliance

    There are about 3,132 airplanes of the affected design in the 
worldwide fleet. We estimate that 870 airplanes of U.S. registry would 
be affected by this proposed AD. We provide the following cost 
estimates to comply with this proposed AD, per inspection cycle:

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                                                                              Hourly                   Cost per
                            Group                              Work hours   labor rate     Parts       airplane
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1...........................................................           24          $65           $0       $1,560
2 and 4.....................................................           28           65            0        1,820
3 and 5.....................................................           30           65            0        1,950
6 and 7.....................................................           28           65            0        1,820
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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.

[[Page 54060]]

    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-2004-19003; Directorate Identifier 2003-NM-
245-AD.

Comments Due Date

    (a) The Federal Aviation Administration (FAA) must receive 
comments on this AD action by October 22, 2004.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to all Model 737-100, -200, -200C, -300, -
400, and -500 series airplanes; certificated in any category.

Unsafe Condition

    (d) This AD was prompted by reports of multiple fatigue cracks 
in the fuselage skin and bonded skin doubler, bearstrap, and doorway 
frames surrounding the forward and aft cargo doors. We are issuing 
this AD to find and fix fatigue cracking in the fuselage skin, 
doubler, bearstrap, and frames, which could result in reduced 
structural integrity of the frames, possible loss of a cargo door, 
and consequent rapid decompression of the fuselage.

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 and Repetitive Inspections/Corrective Action

    (f) Do the applicable detailed, general visual, and low and high 
frequency eddy current inspections for cracks in the fuselage skin, 
doubler, bearstrap, and frames surrounding the main, forward, and 
aft cargo doors, and for cracks in existing repairs, as specified in 
Tables 1, 2, and 3, as applicable, of paragraph 1.E., 
``Compliance,'' of Boeing Alert Service Bulletin 737-53A1228, dated 
July 10, 2003. Do the inspections at the initial compliance times 
listed in Tables 1, 2, and 3, as applicable, of paragraph 1.E., 
``Compliance,'' of the service bulletin; except, where the service 
bulletin specifies a compliance time after the service bulletin 
date, this AD requires compliance within the specified compliance 
time after the effective date of this AD. Do the inspections in 
accordance with the Accomplishment Instructions of the service 
bulletin. Repeat the inspections within the repetitive inspection 
intervals listed in Tables 1, 2, and 3 of paragraph 1.E., 
``Compliance,'' of the service bulletin.
    (g) If any crack is found during any inspection: Repair before 
further flight in accordance with the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-53A1228, dated July 10, 2003. 
Where the service bulletin specifies contacting the manufacturer for 
disposition of certain repair conditions, repair before further 
flight in accordance with a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), 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 ACO, to make such findings. For a 
repair method to be approved, the approval must specifically refer 
to this AD.

No Reporting Required

    (h) Although the service bulletin referenced in this AD 
recommends reporting any discrepancies to the manufacturer, this AD 
does not include that requirement.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle ACO, 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 Designated Engineering Representative 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 26, 2004.
Kevin M. Mullin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-20209 Filed 9-3-04; 8:45 am]
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