04-7289. Airworthiness Directives; Boeing Model 747-400 and -400D Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-400 and -400D series airplanes. This proposal would require an inspection to detect missing fasteners in the section 42 skin and internal doubler at the cutout for the ground exhaust valve of the electrical equipment; modification and rework of the doubler; repetitive inspections of the skin for cracks; and corrective actions if necessary; as applicable. This action is necessary to detect and correct fatigue cracks in the section 42 skin at the cutout for the ground exhaust valve of the electrical equipment, which could result in rapid decompression of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by May 17, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-126-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2003-NM-126-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Candice Gerretsen, 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:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2003-NM-126-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-126-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report that, during full-scale fatigue testing on a Boeing Model 747-400 fatigue test article, skin cracks were found at a skin cutout for the ground exhaust valve of the electrical equipment. One of the cracks was 18 inches long and was found at 33,000 total pressurization cycles. The configuration of the internal doubler installed around the cutout creates stress concentrations in the skin, which causes fatigue cracking of the skin. Also, Boeing records show that some fasteners may not have been installed on the skin doubler on certain Boeing Model 747-400 and -400D series airplanes during production. Fatigue cracks in the section 42 skin at the cutout for the ground exhaust valve of the electrical equipment, if not detected and corrected, could result in rapid decompression of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2340, Revision 2, dated April 24, 2003, which describes the following procedures:

• For Group 1 airplanes: A general visual inspection to detect missing fasteners in the section 42 skin and internal doubler at the cutout for the ground exhaust valve of the electrical equipment, and applicable corrective actions, which include performing an open hole high frequency eddy current (HFEC) inspection for cracks and any applicable repair, oversizing and drilling of holes, and installing fasteners.
• For Group 1 and Group 2 airplanes: Modification and rework of the internal doubler, which includes performing an open hole HFEC inspection for cracks and any applicable repair, oversizing and drilling of holes, and installing fasteners.
• For Group 1 through Group 4 airplanes: Repetitive external HFEC inspections of the skin for cracks, and repair if necessary.

Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

Although the service bulletin specifies that operators may contact the manufacturer for disposition of certain repair conditions, this proposed AD would require operators to repair those conditions per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Operators should note that, although the service bulletin does not list a grace period in certain compliance times, this proposal adds a grace period to the compliance times. The FAA finds that such a grace period will keep airplanes from being grounded unnecessarily.

Clarification of Procedures in Service Bulletin

Part 3 of the Accomplishment Instructions of the service bulletins specifies to “Do a HFEC inspection of the skin and doubler as shown in FIGURE 8 for Group 1, 2 and 3 Airplanes and as show[n] in FIGURE 9 for Group 4 Airplanes.” The correct area to accomplish this HFEC inspection is on the skin around the edge of the doubler, as specified in Figures 8 and 9.

Cost Impact

There are approximately 142 airplanes of the affected design in the worldwide fleet. The FAA estimates that 22 airplanes of U.S. registry would be affected by this proposed AD.

For Group 1 airplanes listed in Boeing Alert Service Bulletin 747-53A2340, it would take approximately 1 work hour per airplane to accomplish the proposed inspection (Part 1), at an average labor rate of $65 per work hour. Based on these figures, the cost impact of this inspection proposed by this AD on U.S. operators is estimated to be $65 per airplane.

For Groups 1 and 2 airplanes listed in Boeing Alert Service Bulletin 747-53A2340, it would take approximately 40 work hours per airplane to accomplish the proposed modification and rework (Part 2), at an average labor rate of $65 per work hour. Based on these figures, the cost impact of this modification and rework proposed by this AD on U.S. operators is estimated to be $2,600 per airplane.

For Groups 1 through 4 airplanes listed in Boeing Alert Service Bulletin 747-53A2340, it would take approximately 1 work hour per airplane to accomplish the proposed inspection (Part 3), at an average labor rate of $65 per work hour. Based on these figures, the cost impact of this inspection proposed by this AD on U.S. operators is estimated to be $65 per airplane, per inspection cycle.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2003-NM-126-AD.

Applicability: Model 747-400 and −400D series airplanes, as listed in paragraph 1.A., “Effectivity,” of Boeing Alert Service Bulletin 747-53A2340, Revision 2, dated April 24, 2003; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To detect and correct fatigue cracks in the section 42 skin at the cutout for the ground exhaust valve of the electrical equipment, which could result in rapid decompression of the airplane, accomplish the following:

Part 1—Fastener Inspection and Corrective Actions If Necessary

(a) For Group 1 airplanes listed in Boeing Alert Service Bulletin 747-53A2340, Revision 2, dated April 24, 2003: Within 250 flight cycles or 4 months after the effective date of this AD, whichever occurs later, do a general visual inspection to detect missing fasteners in the section 42 skin and internal doubler at the cutout for the ground exhaust valve of the electrical equipment, per Part 1 of the Accomplishment Instructions of the service bulletin.

(1) If all fasteners are installed, do the actions specified in paragraph (b) of this AD at the indicated time.

(2) If any fastener is missing, before further flight, accomplish all applicable corrective actions (i.e., performing an open hole high frequency (HFEC) inspection for cracks and any applicable repair, oversizing and drilling of holes, and installation of fasteners), in accordance with Part 1 of the Accomplishment Instructions of the service bulletin, except as required by paragraph (f) of this AD.

Part 2—Modification and Rework

(b) For Group 1 and Group 2 airplanes listed in Boeing Alert Service Bulletin 747-53A2340, Revision 2, dated April 24, 2003: Before the accumulation of 6,000 total flight cycles, or within 1,500 flight cycles or 24 months after the effective date of this AD, whichever occurs later: Modify and rework the internal doubler (i.e., performing an open hole HFEC inspection for cracks and any applicable repair, oversizing and drilling of holes, and installation of fasteners) by accomplishing all actions specified in Part 2 of the Accomplishment Instructions of the service bulletin. Do the actions per the service bulletin, except as required by paragraph (f) of this AD. Any applicable repair must be accomplished before further flight.

Part 3—Repetitive Inspections and Repair If Necessary

(c) At the applicable time specified in paragraph (c)(1) or (c)(2) of this AD, do an external HFEC inspection of the skin for cracks per Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2340, Revision 2, dated April 24, 2003.

(1) For Group 1 and Group 2 airplanes listed in the service bulletin: Within 10,000 flight cycles after accomplishing the actions required by paragraph (b) of this AD, or within 1,500 flight cycles or 24 months after the effective date of this AD, whichever occurs later.

(2) For Group 3 and Group 4 airplanes listed in the service bulletin: Before the accumulation of 15,000 total flight cycles, or within 1,500 flight cycles or 24 months after the effective date of this AD, whichever occurs later.

(d) If no crack is detected during the external HFEC inspection required by paragraph (c) of this AD, repeat the external HFEC inspection thereafter at intervals not to exceed 5,000 flight cycles.

(e) If any crack is detected during the external HFEC inspection required by paragraph (c) of this AD, before further flight, repair per Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2340, Revision 2, dated April 24, 2003, except as required by paragraph (f) of this AD. Repeat the external HFEC inspection in the unrepaired areas thereafter at intervals not to exceed 5,000 flight cycles.

Exception to Service Bulletin Actions

(f) If any discrepancy is found during any inspection required by this AD, and the bulletin specifies to contact Boeing for an alternate repair: Before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved, the approval must specifically reference this AD.

Credit for Previous Revisions of Service Bulletins

(g) Actions accomplished before the effective date of this AD per Boeing Alert Service Bulletin 747-53A2340, original issue, dated August 1, 1991; or Revision 1, dated October 31, 1991, is acceptable for compliance with the requirements of this AD.

Alternative Methods of Compliance

(h)(1) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, FAA, is authorized to approve alternative methods of compliance (AMOCs) for this AD.

(2) An AMOC that provides an acceptable level of safety may be used for any inspection or repair required by this AD, if it is approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For an inspection or repair method to be approved, the approval must specifically reference this AD.

Issued in Renton, Washington, on March 26, 2004.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.