Document headings vary by document type but may contain
                    the following: the agency or agencies that issued and signed a document
the number of the CFR title and the number of each part
                      the document amends, proposes to amend, or is directly
                      related to
the agency docket number / agency internal file number
the RIN which identifies each regulatory action listed in
                      the Unified Agenda of Federal Regulatory and Deregulatory
                      Actions See the
                    Document Drafting Handbook
                    for more details.
 Department of Transportation Federal Aviation Administration 14 CFR Part 39
[Docket No. FAA-2004-19533; Directorate Identifier 2004-NM-31-AD]
RIN 2120-AA64
 AGENCY: Federal Aviation Administration (FAA), DOT.
 ACTION: Notice of proposed rulemaking (NPRM).
 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, 
                        *marcia.walters@faa.gov.*


SUPPLEMENTARY INFORMATION: ( print 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 
                    ( print 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
Action
Work hours
Average labor rate per hour
Cost per 
                             airplane, per  
                             inspection cycle
Number of U.S.-registered airplanes
Fleet cost, per inspection cycleInspections
94
$65
$6,110
175
$1,069,250
 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. § 39.13
  2. The FAA amends § 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.
                                ( print 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 appropriate action: 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