Airworthiness Directives; Boeing Model 747-100, -200, -300, 747SP, and 747SR Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747-100, -200, -300, 747SP, and 747SR series airplanes, that currently requires repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. This action would add new repetitive inspections for cracking of certain areas of the upper chord of the upper deck floor beams, and repair, if necessary. This proposal is prompted by the results of fatigue testing that revealed severed upper chords of the upper deck floor beams due to fatigue cracking. The actions specified by the proposed AD are intended to prevent loss of the structural integrity of the fuselage, which could result in rapid depressurization of the airplane.

DATES:

Comments must be received by January 11, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-355-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 (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-355-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 for Windows or ASCII text.

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, 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 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 2000-NM-355-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. 2000-NM-355-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On April 22, 1993, the FAA issued AD 93-08-12, amendment 39-8559 (58 FR 27927, May 12, 1993), applicable to certain Boeing Model 747 series airplanes, to require repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. That action was prompted by results of fatigue tests that identified areas of the fuselage internal structure where fatigue cracks occurred. The requirements of that AD are intended to prevent loss of the structural integrity of the fuselage.

Actions Since Issuance of Previous Rule

Since the issuance of AD 93-08-12, the FAA received a report that, during fatigue testing, severed upper chords were found on the upper deck floor beams on a Boeing Model 747 series airplane. The chords severed as a result of fatigue cracking. Additional reports were received that indicated the detailed internal visual inspections of the upper deck floor beams, mandated by AD 93-08-12 may not detect cracks before they become critical. Such conditions, if not corrected, could result in loss of the structural integrity of the fuselage, and rapid depressurization of the airplane.

Related AD

On February 22, 2000, the FAA issued AD 2000-04-17, amendment 39-11600 (65 FR 10695, February 29, 2000), applicable to certain Boeing Model 747-100, -200, and -300 series airplanes. That AD requires repetitive inspections to detect fatigue cracking in the chords and webs of certain upper deck floor beams, and repair of any cracking found. This proposed AD would require similar inspections of upper deck floor beams that were not addressed in that AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000, which describes procedures for detailed visual inspections for cracking in the following areas of the fuselage internal structure:

• Sections 41 and 42 upper deck floor beams
• Section 42 frames
• Section 46 frames
• Certain Section 41 bulkhead areas

The service bulletin also describes procedures for repetitive detailed internal and external visual inspections of the main entry doors and door cutouts for cracking, and repetitive open hole high frequency eddy current inspections for cracking in the horizontal flanges of the upper chord of the Sections 41 and 42 upper deck floor beams. The new detailed visual inspection of Area 1 of Sections 41 and 42 would eliminate the need for the existing inspection of those sections. If cracking is found, the service bulletin references the 747 Structural Repair Manual (SRM) for repair instructions, or if the damage is beyond the limits specified in the service bulletin, the service bulletin specifies contacting Boeing for repair data.

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 supersede AD 93-08-12 to continue to require repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. The proposed AD would add new repetitive inspections for cracking of certain areas of the upper chord of the upper deck floor beams, and repair, if necessary. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below.

Differences Between Proposed AD and Revision 1 of the Alert Service Bulletin

This proposed AD differs from the service bulletin as follows:

• The service bulletin specifies that the manufacturer should be contacted for disposition of certain repair conditions, but this proposed AD would require the repair of those conditions to be accomplished 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 (DER) who has been authorized by the Manager, Seattle Aircraft Certification Office, to make such findings.
• The service bulletin specifies doing a high frequency eddy current inspection of the left and right sides of the upper deck floor beam at body station 380 between buttock lines 40 and 76, but this proposed AD would not require that inspection because it was mandated in AD 2000-04-17, amendment 39-11600 (65 FR 10695, February 29, 2000).
• The service bulletin specifies doing detailed visual and high frequency eddy current inspections of body station (BS) 380 through BS 1000 inclusive, on each upper deck floor beam on Group 3 airplanes. This proposed AD would extend the inspection area from BS 380 through BS 1100 inclusive. The manufacturer has informed the FAA that the upper deck floor beams extend to BS 1100 for Group 3 airplanes, and the service bulletin will be revised to reflect this change.
• The service bulletin also specifies that flight cycles with a cabin pressure differential of less than 2.0 pounds per square inch (psi) are not to be counted, but this proposed AD allows this stipulation only for Area 1 (Sections 41 and 42 upper deck floor beams) inspections. The FAA has determined that flight loads can significantly contribute to fatigue loads in other areas. Flights with less than 2.0 psi cabin differential pressure can still have significant flight loads; therefore, the FAA cannot allow an adjustment to flight cycles for areas other than Area 1.
• Additionally, this proposed AD adds a grace period of 3,000 flight cycles after doing the most recent inspection required by AD 93-08-12 for airplanes that have exceeded the compliance threshold specified in the service bulletin.

Explanation of Additional Changes to Requirements of Existing AD

We have changed the requirements of the existing AD, as restated in this proposed AD, to remove all references to the use of “FAA-approved procedures.” This change is consistent with FAA policy in that regard. In place of this language, we have specified accomplishing repairs per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company DER. We have determined that this change will not increase the economic burden on any operator, nor will it increase the scope of the proposed AD. A new paragraph (c) has been added to accommodate this change.

Interim Action

This is considered to be interim action until similar action for Boeing Model 747-400 series airplanes and 747 freighter airplanes is identified, at which time the FAA may consider further rulemaking.

Cost Impact

There are approximately 489 airplanes of the affected design in the worldwide fleet.

The FAA estimates that 181 airplanes of U.S. registry are subject to the existing AD. The actions that are currently required by AD 93-08-12 take approximately 1,746 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions is estimated to be $104,760 per airplane.

We estimate that 155 airplanes of U.S. registry are subject to the new actions in this proposed AD. The new inspections that are proposed in this AD action would take approximately 255 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $2,371,500, or $15,300 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this 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.