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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. FAA-2010-0481; Directorate Identifier 2009-NM-192-AD]
          - RIN 2120-AA64

# AGENCY:

Federal Aviation Administration (FAA), DOT.

# ACTION:

Notice of proposed rulemaking (NPRM).

# SUMMARY:

We propose to adopt a new airworthiness directive (AD) for certain Model 737-100 and -200 series airplanes. This proposed AD would require repetitive inspections for cracking and damaged fasteners of certain fuselage frames and stub beams, and corrective actions if necessary. For certain airplanes, this proposed AD would also require repetitive inspections for cracking of the inboard chord fastener hole of the frame at body station 639, stringer S-16, and corrective actions if necessary. For certain airplanes, this proposed AD would also require an inspection to determine the edge margin of the lower chord. For airplanes with a certain short edge margin, this proposed AD requires repetitive inspections for cracking, and corrective actions if necessary; replacing the lower chord terminates the repetitive inspections. This proposed AD requires an eventual preventive modification. For certain airplanes, doing the modification or a repair would terminate the repetitive inspections for the repaired or modified frame only. For airplanes on which the modification or repair is done at certain body stations, this proposed AD would require repetitive inspections for cracking of certain frame webs and inner and outer chords, and corrective actions if necessary. For certain other airplanes, this proposed AD requires a modification which includes reinforcing the body frame inner chords, replacing the stub beam upper chords and attach angles, and reinforcing the stub beam web. This proposed AD results from reports of fatigue cracks at certain frame sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver load. We are proposing this AD to detect and correct fatigue cracking of certain fuselage frames and stub beams, and possible severed frames, which could result in reduced structural integrity of the frames. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in rapid decompression of the fuselage.

# DATES:

We must receive comments on this proposed AD by July 6, 2010.

# ADDRESSES:

You may send comments by any of the following methods:
      -  Federal eRulemaking Portal:                          Go to                          http://www.regulations.gov . Follow the instructions for submitting comments.                    
      -  Fax:                          202-493-2251.                    
      -  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.                    
      -  Hand Delivery:                          U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, 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, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 206-544-5000, extension 1, fax 206-766-5680; e-mail                         *me.boecom@boeing.com*; Internet                         *https://www.myboeingfleet.com*. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221.                    

## Examining the AD Docket

                    You may examine the AD docket on the Internet at                     *http://www.regulations.gov;*                     or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone 800-647-5527) is in the                     **ADDRESSES**                     section. Comments will be available in the AD docket shortly after receipt.                

# 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 send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the                     **ADDRESSES**                     section. Include “Docket No. FAA-2010-0481; Directorate Identifier 2009-NM-192-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.                

                    We will post all comments we receive, without change, to                     *http://www.regulations.gov*, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.                

## Discussion

We have received reports of fatigue cracks found at certain frame sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver load. Numerous cracks were found in the shear ties, webs, and inboard and outboard chords of the overwing body frames and stub beams between body stations 559 and 639. Cracks were also found in the webs, attach angles, and the upper and lower chords of the stub beams. There were reports of sheared fasteners in the overwing body frames and stub beams in the same location.

Fatigue cracking of certain fuselage frames and stub beams, if not detected and corrected, and possible severed frames, could result in reduced structural integrity of the frames. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in rapid decompression of the fuselage.

## Relevant Service Information

                    We have reviewed Boeing Service Bulletin 737-53-1061, Revision 4, including Addendum, dated July 16, 1992. For airplanes on which a repair (Part III) or preventive modification (Part II) has not been done, the service bulletin describes procedures for                           ( print page 27970)                        repetitive detailed inspections for cracks and damaged fasteners in the circumferential frame and the stub beam at body stations 559, 578, 597, 616, and 639, and corrective actions if necessary. For Group 1-3 airplanes, the service bulletin describes procedures for repetitive eddy current inspections for cracking of the inboard chord fastener hole of the frame at body station 639, stringer S-16, and corrective actions if necessary. For airplanes on which certain stub beam lower chords were installed, the service bulletin describes procedures for an inspection to determine if a short edge margin exists in the lower chord and, for airplanes with a certain short edge margin, repetitive inspections for cracking and corrective actions if necessary. For airplanes on which either circumferential frame at body station 597 was changed as given in Boeing Service Bulletin 737-53-1061, Revision 1, dated December 16, 1983; Revision 2, dated April 18, 1986; or Revision 3, dated June 15, 1989; the service bulletin describes procedures for repetitive detailed inspections for cracking of the frame.                

This service bulletin also describes a preventive modification, which would eliminate the need for the repetitive inspections. For airplanes on which the modification or repair is done at body stations 616 and 639, the service bulletin describes procedures for repetitive detailed inspections for cracking of the body station 616 and 639 frame webs and inner and outer chords, near stringer S-16, and corrective actions if necessary.

The corrective actions include doing a repair for any cracking and damaged fasteners that are within the limits specified, replacing a cracked component by installation of a preventive modification if the cracks are outside the limits, and contacting Boeing for instructions if cracks or damaged fasteners cannot be repaired in accordance with the specified procedures or if the upper chord was replaced at a certain location.

For Group 1-3 airplanes, the service bulletin describes procedures for a modification, which includes reinforcing the body frame inner chords, replacing the stub beam upper chords and attach angles, and reinforcing the stub beam web at body stations 597, 616, and 639.

## Related Rulemaking

We are in the process of issuing an AD that refers to Boeing Alert Service Bulletin 737-53A1254, Revision 1, dated July 9, 2009, and is related to this proposed AD. That service information applies to Model 737-200, -300, -400, and -500 series airplanes. During review of that service information it was determined that the same unsafe condition exists on earlier Boeing Model 737-100 and -200 series airplanes identified in Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, referred to in this proposed AD as the appropriate source of service information for accomplishing the actions.

## FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. This proposed AD would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and the Service Information.”

## Differences Between the Proposed AD and the Service Information

Although the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, include a modification for Group 4 airplanes (Model 737-200C airplanes), the applicability of this proposed AD does not include those airplanes. This proposed AD is applicable to passenger airplanes only.

The service bulletin also specifies to contact the manufacturer for instructions on repairing cracks, but this proposed AD would require repairing cracks 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 the Boeing Commercial Airplanes Organization Delegation Authorization (ODA) that we have authorized to make those findings.

## Costs of Compliance

We estimate that this proposed AD would affect 45 airplanes of U.S. registry.

We estimate that it would take about 4 work-hours per product to comply with the proposed inspections. The average labor rate is $85 per work-hour. Based on these figures, we estimate the cost of this proposed inspection to the U.S. operators to be $15,300, or $340 per product, per inspection cycle.

We estimate that it would take about 288 work-hours per product to comply with the proposed modification (for Group 1-3 airplanes). The average labor rate is $85 per work-hour. Required parts would cost about $58,742 per product. Based on these figures, we estimate the cost of this proposed modification to the U.S. operators to be $83,222 per product.

## 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.

## Regulatory Findings

We 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 this 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Incorporation by reference
      - 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:

      ( print page 27971)    

# 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 AD:

**The Boeing Company:**                                 Docket No. FAA-2010-0481; Directorate Identifier 2009-NM-192-AD.                            

## Comments Due Date

(a) We must receive comments by July 6, 2010.

## Affected ADs

(b) None.

## Applicability

(c) This AD applies to The Boeing Company Model 737-100 and -200 series airplanes, certificated in any category; line numbers 1 through 848 inclusive.

## Subject

(d) Air Transport Association (ATA) of America Code 53: Fuselage.

## Unsafe Condition

(e) This AD results from reports of fatigue cracks at certain frame sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver load. The Federal Aviation Administration is issuing this AD to detect and correct fatigue cracking of certain fuselage frames and stub beams, and possible severed frames, which could result in reduced structural integrity of the frames. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in rapid decompression of the fuselage.

## Compliance

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

## Inspections

(g) For airplanes on which a repair (Part III of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061) or preventive modification (Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061) has not been done in accordance with Boeing Service Bulletin 737-53-1061 as of the effective date of this AD: Before the accumulation of 15,000 total flight cycles or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, do the inspections required by paragraphs (g)(1) and (g)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. Repeat the inspection at the time specified, until the terminating action required by paragraph (l) of this AD is done.

(1) Do a detailed inspection (Part I of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061) for cracks and damaged fasteners of the fuselage frames and stub beams. If no crack or damaged fastener is found, repeat the inspection thereafter at intervals not to exceed 4,500 flight cycles.

(2) Do an eddy current inspection (Part IV of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061) for cracking of the inboard chord fastener hole of the frame at body station 639, stringer S-16. If no crack is found, repeat the inspection thereafter at intervals not to exceed 15,000 flight cycles.

# Note 1:

 Access and restoration instructions, as detailed in the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, are not required by this AD. Operators may do those actions in accordance with their maintenance practices.

(h) For airplanes on which the body station 597 frame was changed as of the effective date of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, dated May 28, 1982; Revision 1, dated December 16, 1983; Revision 2, dated April 18, 1986; or Revision 3, dated June 15, 1989: Within 3,000 flight cycles after the effective date of this AD, do a detailed inspection for cracking of the frame, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. Repeat the detailed inspection thereafter at intervals not to exceed 4,500 flight cycles. Installation of new radius fillers in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, terminates the inspections required by this paragraph.

                                (i) For airplanes on which a stub beam lower chord with                                 1/4                                -inch diameter fasteners at body station 597 is installed as of the effective date of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 1, dated December 16, 1983; Revision 2, dated April 18, 1986; or Revision 3, dated June 15, 1989: Within 3,000 flight cycles after the effective date of this AD, do a detailed inspection for short edge margins. If the short edge margin is determined to be less than 1.5D (diameter), before further flight, do a detailed inspection for cracking of the stub beam lower chords, in accordance with Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. Repeat the detailed inspection thereafter at intervals not to exceed 4,500 flight cycles, if the edge margin is less than 1.5D. If the edge margin is greater than or equal to 1.5D, no further action is required by this paragraph. Replacing the lower chord in accordance with Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, terminates the repetitive inspections specified in this paragraph.                            

## Corrective Actions

(j) Except as required by paragraph (k) of this AD, if any crack or damaged fastener is found during any inspection required by this AD, before further flight, repair if cracking and damaged fasteners are within the specified limits, or do a preventive modification if cracking or damaged fasteners are outside the specified limits, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992.

## Exception to Service Information

(k) Where Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992, specifies to contact Boeing for repair instructions: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (n) of this AD.

## Terminating Action (Preventive Modification) for Certain Inspections

(l) Before the accumulation of 75,000 total flight cycles: Do the preventive modification in accordance with Part II, or repair in accordance with Part III, of the Accomplishment Instructions of Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992. The modification or repair terminates the repetitive inspection requirements of this AD for the repaired or modified frame only, except as required by paragraph (m) of this AD.

## Post-Modification or Repair Inspections

(m) For airplanes on which a repair or modification at body station 616 or 639 is done: Within 24,000 flight cycles after doing the repair or modification, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, do a detailed inspection for cracking of the BS 616 and 639 frame webs, inner chord, and outer chord near stringer S-16, in accordance with Boeing Service Bulletin 737-53-1061, Revision 4, dated July 16, 1992.

(1) If no cracking is found, repeat the inspection thereafter at intervals not to exceed 4,500 flight cycles.

(2) If any cracking is found, before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (n) of this AD.

## Alternative Methods of Compliance (AMOCs)

                                (n)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: 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. Or, e-mail information to                                 *9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.*

(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 principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

                                (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 the                                       ( print page 27972)                                    Boeing Commercial Airplanes Organization Delegation Authorization (ODA) that 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.                            

Issued in Renton, Washington, on May 5, 2010.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 2010-11905 Filed 5-18-10; 8:45 am]

BILLING CODE 4910-13-P