E7-20467. Airworthiness Directives; Boeing Model 747-200F, 747-300, 747-400, and 747-400D Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-200F, 747-300, 747-400, and 747-400D series airplanes. This proposed AD would require a detailed inspection to detect missing fasteners from the shear clip at a certain stub frame to auxiliary sill joint, and applicable related investigative and corrective actions. This proposed AD results from reports of missing fasteners from the shear clip of the stub frame to auxiliary sill joint and cracking of the adjacent exterior skin and internal doubler. We are proposing this AD to ensure that fasteners are installed in the shear clip of the stub frame to auxiliary sill joint. Missing fasteners could result in cracks in the adjacent exterior skin and internal doubler, which can propagate and result in loss of structural integrity and sudden in-flight decompression of the airplane.

DATES:

We must receive comments on this proposed AD by December 3, 2007.

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: [phone].
• 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.

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

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 [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

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-2007-0045; Directorate Identifier 2007-NM-169-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 two reports of cracks found in the exterior skin and internal doubler adjacent to the shear clip at the stub frame to auxiliary sill joint at stringer 30 (left and right sides), body station (BS) 488. In addition, on one of the airplanes, seven fasteners were missing from the shear clip on the left side of the airplane. The cause of the missing fasteners has been attributed to a manufacturing process error. If any fastener is missing from the shear clip at the stub frame to auxiliary sill joint, cracks could result in the exterior skin and internal doubler. Such cracks can propagate and result in loss of structural integrity and sudden in-flight decompression of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2685, dated May 31, 2007. The service bulletin describes procedures for doing a detailed inspection to detect missing fasteners from the shear clip at the stub frame to auxiliary sill joint at stringer 30 (left and right sides), BS 488, and applicable related investigative and corrective actions. The related investigative actions include doing an open hole high frequency eddy current inspection to detect cracks at certain fastener locations in the exterior skin and internal doubler, and repetitive low frequency eddy current inspections to detect cracks at the edge row fasteners of any skin repair doubler, as applicable. The corrective actions include trimming out cracks, installing missing fasteners, installing skin repair doublers, and contacting Boeing for certain repair conditions, as applicable.

The service bulletin also specifies the following compliance times:

• For the initial detailed inspection: Before 6,000 total flight cycles, or within 3,000 flight cycles, whichever occurs later.
• For the related investigative actions: Before further flight (for an open hole high frequency eddy current inspection), and within 15,000 flight cycles after installation of repair and thereafter at intervals not to exceed 1,500 flight cycles (for low frequency eddy current inspections).
• For the corrective actions: Before further flight.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

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. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and Service Information.”

Differences Between the Proposed AD and Service Information

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing those conditions 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 an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Costs of Compliance

There are about 98 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 8 airplanes of U.S. registry. The proposed actions would take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $640, or $80 per airplane.

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 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 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
• 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

[Amended]

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

Boeing: Docket No. FAA-2007-0045; Directorate Identifier 2007-NM-169-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by December 3, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 747-200F, 747-300, 747-400, and 747-400D series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 747-53A2685, dated May 31, 2007.

Unsafe Condition

(d) This AD results from two reports of cracks found in the exterior skin and internal doubler adjacent to the shear clip at the stub frame to auxiliary sill joint at stringer 30 (left and right sides), body station (BS) 488. In addition, on one of the airplanes, seven fasteners were missing from the shear clip on the left side of the airplane. The cause of the missing fasteners has been attributed to a manufacturing process error. We are issuing this AD to ensure fasteners in the shear clip of the stub frame to auxiliary sill joints (left and right sides) are installed. Missing fasteners could result in cracks in the exterior skin and internal doubler, which can propagate and result in loss of structural integrity and sudden in-flight 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.

Inspection and Applicable Related Investigative and Corrective Actions

(f) At the applicable compliance time and repeat intervals listed in Tables 1 and 2 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2685, dated May 31, 2007; except that where the service bulletin specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD: Do the inspection and applicable related investigative and corrective actions by accomplishing all the applicable actions specified in the Accomplishment Instructions of the service bulletin, except as provided by paragraph (g) of this AD.

Repair of Cracks

(g) If any crack is found during any inspection required by this AD, and Boeing Service Bulletin 747-53A2685, dated May 31, 2007, specifies to contact Boeing for appropriate action: Before further flight, repair the crack using a method approved in accordance with the procedures specified in paragraph (h) 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 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.

Issued in Renton, Washington, on October 9, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.