Airworthiness Directives; Boeing Model 747 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 series airplanes. This proposal would require repetitive inspections of the aft pressure bulkhead to detect cracking, and repair, if necessary. This proposal is prompted by a report of fatigue cracking found in the upper half of the aft pressure bulkhead. The actions specified by the proposed AD are intended to detect and correct cracking in the aft pressure bulkhead, which could result in rapid decompression of the fuselage or overpressurization of the tail section.

DATES:

Comments must be received by March 20, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-330-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, 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:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.

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 notice may be changed in light of the comments received.

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 notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 99-NM-330-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. 99-NM-330-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report indicating that a crack was found in the upper half of the aft pressure bulkhead on a Boeing Model 747 series airplane. The crack was located at the aft/inner fastener row, which attaches the web to the “Y” ring, and was 7.5 inches long. Analysis indicates that the crack was initiated and propagated by fatigue. Such cracking, if not detected and corrected, could result in rapid decompression of the fuselage or overpressurization of the tail section.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998, which describes procedures for repetitive inspections of the aft pressure bulkhead at the “Y”-ring-to-web lap splice to detect cracking, and repair, if necessary. The inspections to detect cracking include a detailed visual inspection of the upper half of the bulkhead and a high frequency eddy current (HFEC) inspection of the upper and lower halves of the bulkhead. Accomplishment of the actions specified in the alert service bulletin is intended to adequately address the identified unsafe condition.

Other Relevant Rulemaking

The FAA has previously issued AD 98-20-20, Amendment 39-10786 (63 FR 50495, September 22, 1998). That AD requires repetitive inspections to detect damage and cracking of the aft pressure bulkhead on certain Boeing Model 747 series airplanes, line numbers 1 through 671 inclusive. The inspections required by that AD are similar to the ones described in this proposed AD, but this proposed AD would apply to Boeing Model 747 series airplanes having line numbers 672 and subsequent, as listed in Boeing Alert Service Bulletin 747-53A2425.

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 alert service bulletin described previously, except as discussed below.

Differences Between Alert Service Bulletin and Proposed Rule

Operators should note that, although the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposed AD requires the repair of those conditions to be accomplished in accordance with a method approved by the FAA, or in accordance with 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.

The alert service bulletin also specifies that certain inspections and repairs required by this proposed AD may be accomplished in accordance with “an operator's equivalent procedure.” However, this proposed AD requires that those actions be accomplished in accordance with the procedures specified in appropriate chapters of the Boeing 747 Maintenance Manual or the Boeing 747 Structural Repair Manual. An “operator's equivalent procedure” may be used only if approved as an alternative method of compliance in accordance with paragraph (g) of this AD.

Clarification of Proposed Requirement

The FAA has been advised that the intent of the manufacturer in the service bulletin is that accomplishment of an HFEC inspection implies concurrent accomplishment of a detailed visual inspection. Therefore, this proposed rule clarifies the manufacturer's intent, in that it proposes to require accomplishment of repetitive detailed visual inspections at intervals not to exceed 1,500 flight cycles, and repetitive HFEC inspections at intervals not to exceed 3,000 flight cycles.

Cost Impact

There are approximately 552 airplanes of the affected design in the worldwide fleet. The FAA estimates that 84 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 7 work hours per airplane to accomplish the proposed detailed visual inspection, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed detailed visual inspection on U.S. operators is estimated to be $35,280, or $420 per airplane, per inspection cycle.

It would take approximately 7 work hours per airplane to accomplish the proposed HFEC inspections, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed HFEC inspections on U.S. operators is estimated to be $35,280, or $420 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 AD were not adopted.

Regulatory Impact

The regulations proposed herein would not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

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.