We partially agree with Boeing. We agree to change the end level effect of the unsafe condition by removing the word ``rapid,'' since Boeing has provided data verifying that the decompression does not happen quickly. However, we do not agree that
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the decompression is ``controlled'' because of the safety implications and consequences associated with cracking on a web panel of the main wheel well pressure deck. We have changed the applicable sections in this AD accordingly.

Request To Clarify Certain Compliance Times

Boeing asks that we clarify the different compliance times for replacing discrepant web panels, depending on the thickness, as specified in Table 1 of Part 1.E., Compliance, of Boeing Special Attention Service Bulletin 737571289, dated June 13, 2007. (The service bulletin was referenced in the NPRM as the appropriate source of service information for accomplishing the specified actions.) Boeing states that, as written, paragraphs (g)(1) and (g)(2) of the NPRM would allow 30 months or 6,000 flight cycles, whichever is later, to replace discrepant web panels. Boeing notes that this is acceptable for discrepant web panels with a material thickness that is found to be greater than or equal to 0.037 inch, and less than 0.047 inch; however, for web panels with a material thickness of less than 0.037 inch the specified compliance time is before further flight. Boeing adds that web panels with a material thickness of less than 0.037 inch do not meet the ultimate regulatory load requirements. Boeing also asks that the related investigative and corrective actions be clarified.

We agree with Boeing that some clarification is necessary. Paragraph (g)(1) of the AD requires accomplishing all applicable related investigative and corrective actions before further flight (which includes replacing any discrepant web panels) by doing all the actions specified in the Accomplishment Instructions of the service bulletin. The Accomplishment Instructions do not clearly identify web panels with a material thickness of less than 0.037 inch; however, the web panels are clearly identified in paragraph 1.E. of the service bulletin. Paragraph 1.E. specifies replacing web panels with a material thickness of less than 0.037 inch, as specified in paragraph 3.B.7. of the Accomplishment Instructions of the service bulletin. Therefore, we have clarified paragraph (g)(1) of this AD to add that the corrective actions include replacing any web panel with a material thickness of less than 0.037 inch before further flight. We have also changed paragraph (g)(2) of this AD to clarify that the compliance time in that paragraph is separate from the compliance time specified in paragraph (g)(1). The related investigative and corrective actions are defined in the service information section of the NPRM; therefore, no change is necessary in this regard.

Request To Clarify That Additional Action Is Necessary

Boeing also asks that we change paragraph (e) of the NPRM to clarify that additional action is necessary for operators that inspected web panels using instructions that were contained in Boeing Communication messages that were sent out on January 17, 2006, prior to the release of the referenced service bulletin. Boeing states that the messages were sent to airlines that were operating airplanes that could have a discrepant web panel. Boeing adds that following release of those messages, as part of the information being developed for release in the referenced service bulletin, it was determined that additional details were necessary to accurately define the instructions to inspect for discrepant web panels. Boeing notes that the additional details, which affect both the chemical spot test and the ultrasonic thickness inspections, have been included in the service bulletin referenced in the NPRM as the source of service information for doing the specified actions; therefore, inspections accomplished without these additional steps could result in incorrect identification of discrepant web panels. Boeing also suggests that this language be added to paragraph (e) of the AD.

We acknowledge Boeing's concerns; however, paragraph 1.E, ``Compliance,'' of the referenced service bulletin specifies that the inspection instructions contained in the subject Boeing messages sent out on January 17, 2006, did not include certain steps. That section specifies that the chemical spot test and ultrasonic thickness inspections must be done again by following the procedures in the referenced service bulletin. In addition, paragraph (e) of this AD states that if the actions required by this AD have been done previously, they do not need to be done again. Therefore, we have made no change to the AD in this regard.

Conclusion

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD.

Costs of Compliance

There are about 31 airplanes of the affected design in the worldwide fleet. This AD affects 1 airplane of U.S. registry. The required tests and inspections take about 3 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 this U.S. operator is $240.

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 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.
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Adoption of the Amendment
Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:
PART 39AIRWORTHINESS 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 AD: 20081325 Boeing: Amendment 3915588. Docket No. FAA20070395; Directorate Identifier 2007NM157AD.
Effective Date
(a) This airworthiness directive (AD) is effective August 12, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Boeing Model 737300 and 400 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 737571289, dated June 13, 2007. Unsafe Condition
(d) This AD results from several reports indicating that cracks ranging from 0.8 to 8.0 inches long were found on a certain web panel of the main wheel well pressure deck. We are issuing this AD to prevent fatigue cracking in the web panel of the main wheel well pressure deck, which could result in venting and consequent 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.
Testing/Inspecting/Investigative and Corrective Actions
(f) Within 6 months after the effective date of this AD: Do a test of the web panel of the main wheel well pressure deck to determine the material type, and do an ultrasonic inspection to determine material thickness, by doing all the applicable actions specified in the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737571289, dated June 13, 2007.
(g) For airplanes on which the web thickness or material is found to be discrepant during the test and inspection required by paragraph (f) of this AD, accomplish the applicable actions specified in paragraphs (g)(1) and (g)(2) of this AD at the time specified, in accordance with Boeing Special Attention Service Bulletin 737571289, dated June 13, 2007.
(1) Except as provided by paragraph (h) of this AD: Do all applicable related investigative and corrective actions (including detailed and general visual inspections) before further flight, by doing all the actions specified in the Accomplishment Instructions of the service bulletin. Repeat the inspections thereafter at intervals not to exceed 1,000 flight cycles until the actions required by paragraph (g)(2) of this AD have been done. For any web panel with a material thickness of less than 0.037 inch, replace the web panel before further flight, in accordance with paragraph 3.B.7. of the Accomplishment Instructions of the service bulletin. Doing this replacement ends the repetitive inspections required by this paragraph.
(2) Except as required by paragraph (g)(1) of this AD: Within 30 months or 6,000 flight cycles after accomplishing the actions required by paragraph (g)(1) of this AD, whichever is later, replace the web panel in accordance with the Accomplishment Instructions of the service bulletin. Doing this replacement ends the repetitive inspections required by paragraph (g)(1) of this AD.
Corrective Actions
(h) If any crack or corrosion is found during any inspection required by paragraph (g)(1) of this AD, and Boeing Special Attention Service Bulletin 737571289, dated June 13, 2007, specifies to contact Boeing for repair instructions: Before further flight, repair according to a method approved in accordance with the procedures specified in paragraph (i) of this AD.
Alternative Methods of Compliance (AMOCs)
(i)(1) The Manager, Seattle Aircraft Certification Office (ACO), has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.
(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 appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.
(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, 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
(j) You must use Boeing Special Attention Service Bulletin 737 571289, dated June 13, 2007, to do the actions required by this AD, unless the AD specifies otherwise.
(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, P.O. Box 3707, Seattle, Washington 981242207.
(3) You may review copies of the service information
incorporated by reference at the FAA, Transport Airplane
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 2027416030, or go to: http://www.archives.gov/federal_register/code_of_federal_ regulations/ibr_locations.html.

Issued in Renton, Washington, on June 10, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. E814475 Filed 7708; 8:45 am]
BILLING CODE 491013P

FOR FURTHER INFORMATION CONTACT Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 980573356; telephone (425) 9176447; fax (425) 9176590.