05-20966. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Final rule.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for all Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD requires repetitive inspections of the aft pressure bulkhead web for fatigue cracks, crack indications, discrepant holes, and corrosion; and repair if necessary. This AD results from reports of fatigue cracks in the aft pressure bulkhead web. We are issuing this AD to detect and correct such fatigue cracks, which could result in a rapid decompression of the airplane.

DATES:

This AD becomes effective November 25, 2005.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of November 25, 2005.

ADDRESSES:

You may examine the 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., Nassif Building, room PL-401, Washington, DC.

Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for service information identified in this AD.

FOR FURTHER INFORMATION CONTACT:

Howard Hall, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Examining the Docket

You may examine the airworthiness directive (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 [phone]) is located on the plaza level of the Nassif Building at the street address stated in the ADDRESSES section.

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to all Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That NPRM was published in the Federal Register on May 2, 2005 (70 FR 22620). That NPRM proposed to require repetitive inspections of the aft pressure bulkhead web for fatigue cracks, crack indications, discrepant holes, and corrosion; and repair if necessary.

Comments

We provided the public the opportunity to participate in the development of this AD. We have considered the comments received.

Supportive Comments

Two commenters, including the manufacturer, support the proposed AD.

Request To Add Provision for Special Flight Permits

One commenter requests that the proposed AD be revised to include a phrase used in earlier ADs to permit the use of special flight permits. The commenter explains that, due to the number of work hours needed to gain access to the forward side of the aft pressure bulkhead, it needs to use the provisions for special flight permits. We infer that the commenter believes that because the proposed AD does not contain information on ferry flights, ferry flights are not allowed.

We do not agree with the commenter's request to add the special flight permit language, nor do we agree with the commenter's inference that special flight permits are not allowed by this AD. Special flight permits are allowed unless limitations or prohibitions are specifically identified in the AD. For this AD there are no limitations or prohibitions. On July 10, 2002, we issued a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's airworthiness directives system. The regulation now includes material that relates to altered products, special flight permits (i.e., ferry flights), and alternative methods of compliance (AMOCs). Since we have now included this information in 14 CFR part 39, information on special flight permits is not included in each individual AD unless there are limitations on special flight permits for an individual AD. We have not changed the AD in this regard.

Request To Add Language That Advises Operators How To Address Pre-existing Repairs

Another commenter requests that the proposed AD be revised to include language advising operators how to treat pre-existing repairs in the inspection area of the aft pressure bulkhead. The commenter justifies the request by noting that the “* * * bulkhead is the subject of numerous other service bulletins and other ADs, any or all of which may have resulted in the installation of repairs in the inspection area,” and that the absence of such advisory language would require AMOCs for each instance of pre-existing repairs. We infer that the commenter believes that the AD requires AMOCs for each pre-existing repair that prevents someone from complying with the requirements of the AD, and is requesting that the AD include specific language to provide relief for treating these pre-existing repairs.

We understand the commenter's concern about obtaining AMOCs for pre-existing repairs, especially since there are three ADs that cover the inspection area. We concur with the commenter in this regard. As noted in the reply to the previous comment on special flight permits, we issued a new version of 14 CFR part 39 on July 10, 2002. In section 39.17, it states, “If a change in a product affects your ability to accomplish the actions required by the airworthiness directive in any way, you must request FAA approval of an alternative method of compliance.” This statement means that pre-existing repairs do not require AMOC approval unless they affect the operator's ability to accomplish the actions of the AD. Since we cannot anticipate the wide variety of possible repair configurations, this is best handled by requesting an AMOC for each repair. We have not changed the AD in this regard.

Request To Query Boeing for Availability of Parts

One commenter notes that certain repairs would require replacement of sections of curved structural members that are difficult for operators to fabricate on short notice. The commenter suggests that Boeing should be queried for availability of replacement materials in the event that an inspection finds the need for corrective action.

We agree that certain parts may be difficult for operators to fabricate on short notice (i.e., before further flight). We contacted Boeing about parts availability in regard to this AD, and have confirmed that a sufficient quantity of parts is available. We encourage operators to contact Boeing for specific information on parts availability. We have not changed the AD in this regard.

Request to Operator for Additional Repair Guidance

One commenter requests that Boeing provide additional repair guidance other than “contact Boeing.” The commenter notes that the manufacturer has previous experience in addressing similar repairs in the area to be inspected in accordance with this AD. The commenter acknowledges that every repair is different, but believes that a repair drawing or structural-repair-manual-type of repair should be made available. The commenter also states that it is impractical to contact Boeing in an airline's operational environment.

We acknowledge the commenter's request. We understand that general repair information applicable to this AD would help operators plan for any potential corrective action. We have coordinated this issue with Boeing. However, in this particular area, it is difficult to develop specific guidelines for the various conditions that an operator may encounter. Although no general repair information exists now (at time of publication), we remind operators that we may approve (if submitted and approved) repair drawings as allowed for in paragraph (i) of this AD, which describes ways to get approval of an alternative method of compliance (AMOC). We remind operators that they may apply for an AMOC in accordance with the provisions in paragraphs (i) and (g) of this AD. We have not changed the AD in this regard.

Conclusion

We have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD as proposed.

Explanation of Change Made to This AD

We have simplified paragraph (g) of this AD by referring to the “Alternative Methods of Compliance (AMOCs)” paragraph of this AD for repair methods.

Clarification of Alternative Method of Compliance (AMOC) Paragraph

We have revised this AD to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.

Costs of Compliance

There are about 978 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this AD:

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
LFEC and detailed inspection, per inspection cycle	8	$65	None	$520 per inspection cycle	630	$327,600 per inspection cycle.
HFEC and detailed inspection (in lieu of LFEC and detailed inspection), per inspection cycle	2	65	None	$130 per inspection cycle	630	$81,900 per inspection cycle.

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 have determined that 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.

We prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket. 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
• 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

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

2005-21-06 Boeing: Amendment 39-14344. Docket No. FAA-2005-21086; Directorate Identifier 2004-NM-217-AD.

Effective Date

(a) This AD becomes effective November 25, 2005.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category.

Unsafe Condition

(d) This AD was prompted by reports of fatigue cracks in the aft pressure bulkhead web. We are issuing this AD to detect and correct such fatigue cracks, which 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.

Inspections

(f) At the applicable “Inspection Threshold” in the table in Part 1.E. “Compliance” of Boeing Alert Service Bulletin 737-53A1248, dated September 9, 2004, or within 18 months after the effective date of this AD, whichever occurs later, and thereafter at intervals not to exceed the applicable “Inspection Repeat Interval” in that table: Do the inspections (i.e., detailed inspection and either high- or low-frequency eddy current inspections) of the aft pressure bulkhead web for fatigue cracks, crack indications, discrepant holes, and corrosion, in accordance with the Accomplishment Instructions of the service bulletin.

Corrective Action Difference

(g) If any fatigue crack, crack indication, discrepant hole, or corrosion is found during any inspection required by this AD, before further flight, repair the fatigue crack, crack indication, discrepant hole, and corrosion according to a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or using a method approved in accordance with the procedures specified in paragraph (i) of this AD.

No Reporting

(h) Although the service bulletin references a reporting requirement in the Accomplishment Instructions, that reporting is not required by this AD.

Alternative Methods of Compliance (AMOCs)

(i)(1) The Manager, Seattle ACO, FAA, 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 corrective actions, 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.

(3) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Material Incorporated by Reference

(j) You must use Boeing Alert Service Bulletin 737-53A1248, dated September 9, 2004, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call [phone], or go to http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.

Issued in Renton, Washington, on October 13, 2005.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.