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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. FAA-2008-1275; Directorate Identifier 2007-NM-167-AD; Amendment 39-15892; AD 2009-09-06]
          - RIN 2120-AA64

# AGENCY:

Federal Aviation Administration (FAA), DOT.

# ACTION:

Final rule.

# SUMMARY:

We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive detailed and high frequency eddy current inspections to detect cracks of the backup intercostals and the upper sill of the forward airstair doorway, and applicable corrective actions. This AD also provides for an optional terminating action, which would eliminate the need for repetitive inspections. This AD results from a report indicating that cracks were found in the backup intercostals and upper sill web of the forward airstair doorway. We are issuing this AD to detect and correct fatigue cracking of the backup intercostals and upper sill web of the forward airstair doorway, which could result in a rapid loss of cabin pressure.

# DATES:

This AD is effective June 11, 2009.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of June 11, 2009.

# ADDRESSES:

                        For service information identified in this 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&fnl;                         *https://www.myboeingfleet.com.*

## 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 AD, the regulatory evaluation, any comments received, and other information. The address for the Docket Office (telephone 800-647-5527) is the Document Management Facility, U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.                

# FOR FURTHER INFORMATION CONTACT:

Alan Pohl, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6450; fax (425) 917-6590.

# SUPPLEMENTARY INFORMATION:

## Discussion

                    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model  737-100, -200, -200C, -300, -400, and -500 series airplanes. That NPRM was published in the                     **Federal Register**                     on December 5, 2008 (73 FR 74080). That NPRM proposed to require repetitive detailed and high frequency eddy current inspections to detect cracks of the backup intercostals and the upper sill of the forward airstair doorway, and applicable corrective actions. That NPRM also provided an optional terminating action, which would eliminate the need for repetitive inspections.                

## Comments

We gave the public the opportunity to participate in developing this AD. We considered the comments received from the two commenters.

## Support for the NPRM

Boeing concurs with the contents of the NPRM.

## Request for Clarification

Southwest Airlines requests more information regarding alternative procedures for airplanes that have had the airstair door deactivated per Boeing Service Bulletin 737-52-1092. Southwest Airlines asks whether instructions developed by operators, for open and close of an airstair door after deactivation per Boeing Service Bulletin 737-52-1092, will be considered approved equivalent procedures.

No alternative procedures have been established that have general FAA approval; however, according to the provisions of paragraph (h) of the final rule we may approve requests for different compliance methods if the requests include data that prove that the new methods would provide an acceptable level of safety.

## Conclusion

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD as proposed.

## Costs of Compliance

There are 1,712 airplanes of the affected design in the worldwide fleet. This AD affects 509 airplanes of U.S. registry. The inspections take 2 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the AD for U.S. operators is $81,440, or $160 per airplane, per inspection cycle.

The optional terminating action, if done, would take 9 work hours, at an average labor rate of $80 per work hour. Required parts cost between $533 and $566 per airplane, depending on the airplane configuration. Based on these figures, the estimated cost of the optional terminating action would range between $1,253 and $1,286 per airplane, depending on the airplane configuration.

## 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

                    This AD will not have federalism implications under Executive Order 13132. This AD will 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                           ( print page 21255)                        responsibilities among the various levels of government.                

For the reasons discussed above, I certify that this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under 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

## Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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 AD: 

**2009-09-06 Boeing:**                             Amendment 39-15892. Docket No. FAA-2008-1275; Directorate Identifier 2007-NM-167-AD.                        

## Effective Date

(a) This airworthiness directive (AD) is effective June 11, 2009.

## Affected ADs

(b) None.

## Applicability

(c) This AD applies to Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 737-53A1269, dated May 17, 2007.

## Unsafe Condition

(d) This AD results from a report indicating that cracks were found in the backup intercostals and upper sill web of the forward airstair doorway. We are issuing this AD to detect and correct fatigue cracking of the backup intercostals and upper sill web of the forward airstair doorway, which could result in a rapid loss of cabin pressure.

## 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.

## Inspections

(f) At the applicable compliance times and repeat intervals listed in the tables of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1269, dated May 17, 2007 (hereafter “the service bulletin”), except as provided by paragraphs (f)(1), (f)(2), and (f)(3) of this AD: Do repetitive detailed and high frequency eddy current inspections to detect cracks of the backup intercostals and the upper sill of the forward airstair doorway, and applicable corrective actions by accomplishing all the applicable actions specified in the Accomplishment Instructions of the service bulletin. Do the applicable corrective actions before further flight.

(1) Where the service bulletin specifies a compliance time from the release date of the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.

(2) Where the columns identified as “Airplane Flight Cycles” in the tables of the service bulletin specify less than 45,000 total flight cycles for certain actions, this AD affects airplanes having less than or equal to 45,000 total flight cycles.

(3) Where the columns identified as “Repeat Interval” in the tables of the service bulletin specify an interval of 4,500 flight cycles for all conditions, this AD requires repetitive inspections only if no crack is found during any inspection required by paragraph (f) of this AD.

## Optional Terminating Action

(g) Accomplishing the backup intercostal repair/preventative modification and/or the upper door sill web repair, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1269, dated May 17, 2007, terminates all the corresponding repetitive inspection requirements of paragraph (f) of this AD.

## Alternative Methods of Compliance (AMOCs)

(h)(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: Alan Pohl, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (917) 917-6450; fax (425) 917-6590.

(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 an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, FAA, 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.

## Material Incorporated by Reference

(i) You must use Boeing Alert Service Bulletin 737-53A1269, dated  May 17, 2007, to do the actions required by this AD, unless the AD specifies otherwise. The optional actions specified by this AD, if accomplished, must also be done in accordance with Boeing Alert Service Bulletin 737-53A1269, dated May 17, 2007.

(1) The Director of the Federal Register approved the incorporation by reference of this service information under 5 U.S.C. 552(a) and 1 CFR part 51.

                            (2) For service information identified in this 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.*

(3) You may review copies of the 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 or 425-227-1152.

                            (4) You may also review copies of the service information that is incorporated by reference at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to:                             *http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.*

Issued in Renton, Washington, on April 22, 2009.

Stephen P. Boyd,

Assistant Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. E9-9947 Filed 5-6-09; 8:45 am]

BILLING CODE 4910-13-P