01-27190. 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 for cracking of the skin, bear strap, and sill chord of the lower lobe cargo door cutout, and repair, if necessary. This proposal also provides, for certain airplanes, an optional modification of the lower lobe cargo door cutout, which ends the pre-modification repetitive inspections, but would necessitate new post-modification repetitive inspections after a certain time. This action is necessary to find and fix cracking of the skin, bear strap, and sill chord of the lower lobe cargo door cutout, which could lead to reduced structural integrity of the lower lobe cargo door cutout, and result in rapid depressurization of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by December 14, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-377-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. 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. 2000-NM-377-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 [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 2000-NM-377-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-377-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports indicating that cracking has been found in the upper corners of the lower lobe cargo door cutout on certain Boeing Model 747 series airplanes. Fatigue cracking of the skin, bear strap, and sill chord of the cargo door initiates at the fuselage skin fastener holes common to the hinge fairing strip. Such cracking, if not corrected, could lead to reduced structural integrity of the lower lobe cargo door cutout, and result in rapid depressurization of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2448, including Appendix A, dated September 28, 2000, which describes procedures for repetitive detailed visual and high frequency eddy current inspections for cracking of the skin, bear strap, and sill chord of the lower lobe cargo door cutout. If any cracking is found, the service bulletin specifies to contact the airplane manufacturer for repair instructions. For airplanes with no cracking and with adequate edge margins, the service bulletin also describes procedures for an optional modification of the lower lobe cargo door cutout. The optional modification involves removal of the hinge fairing and its fasteners, oversizing fastener holes, and replacing existing fasteners and the grounding strap with new fasteners and a new strap. Accomplishment of this optional modification eliminates the need to do the repetitive inspections described previously. However, Figure 5 of the service bulletin describes procedures for new post-modification repetitive detailed visual and high frequency eddy current inspections for cracking of the skin adjacent to the lower lobe cargo door cutout. If the optional modification is done, the post-modification inspections are eventually 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 AD and Service Bulletin

Operators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of repairs, this proposed AD would require all repairs 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 who has been authorized by the Manager, Seattle Aircraft Certification Office, to make such findings.

Operators should note that the requirements of this proposed AD would apply only to airplanes with line numbers 1 through 1255 inclusive, as listed in Group 1 in the service bulletin. Airplanes with line numbers 1256 through 1297 inclusive, which are identified as Group 2 in the service bulletin, have cold-worked fastener holes near the edge of the skin panel at the upper corners of the door cutout. Thus, they are not as susceptible to the fatigue cracking addressed by this proposed AD. (Airplanes with line numbers 1298 and subsequent have a redesigned skin panel and increased edge margin at fastener locations. These airplanes are also not subject to the unsafe condition addressed by this proposed AD.)

Cost Impact

There are approximately 1,129 airplanes of the affected design in the worldwide fleet. The FAA estimates that 275 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 3 work hours per airplane to accomplish the proposed inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of this proposed inspection on U.S. operators is estimated to be $49,500, or $180 per airplane, per inspection cycle.

The cost impact figure discussed above is 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 2000-NM-377-AD.

Applicability: Model 747 series airplanes, line numbers 1 through 1255 inclusive, certificated in any category.

Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To find and fix cracking of the skin, bear strap, and sill chord of the lower lobe cargo door cutout, which could lead to reduced structural integrity of the lower lobe cargo door cutout, and result in rapid depressurization of the airplane, accomplish the following:

Repetitive Inspections

(a) Perform detailed visual and high frequency eddy current inspections to find cracking of the skin, bear strap, and sill chord at the upper aft and forward corners of the lower lobe cargo door cutout, according to Boeing Alert Service Bulletin 747-53A2448, including Appendix A, dated September 28, 2000. Do the initial inspections at the time shown in paragraph (a)(1) or (a)(2) of this AD, as applicable, and repeat the inspections at least every 3,000 flight cycles until paragraph (c) of this AD is accomplished.

Note 2:

For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

(1) For airplanes with fewer than 13,000 total flight cycles as of the effective date of this AD: Do the inspection prior to the accumulation of 13,000 total flight cycles or within 1,000 flight cycles after the effective date of this AD, whichever is later.

(2) For airplanes with 13,000 or more total flight cycles as of the effective date of this AD: Do the inspection within 1,000 flight cycles or 1 year after the effective date of this AD, whichever is first.

Repair

(b) If any crack is found during any inspection required by paragraph (a) of this AD: 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 by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD.

Optional Modification

Note 3:

If edge margin distance is outside the limits specified in Figure 4 of Boeing Alert Service Bulletin 747-53A2448, including Appendix A, dated September 28, 2000, no modification is available.

(c) If no crack is found during any inspection required by paragraph (a) of this AD, AND edge margin distance is within the limits specified in Figure 4 of Boeing Alert Service Bulletin 747-53A2448, including Appendix A, dated September 28, 2000: Do paragraphs (c)(1) and (c)(2) of this AD.

(1) Do the optional modification of the lower lobe cargo door cutout (including removing the hinge fairing and its fasteners, oversizing fastener holes, and replacing existing fasteners with new fasteners and the grounding strap with a new strap) described in the service bulletin. Such modification ends the repetitive inspections required by paragraph (a) of this AD.

(2) Within 16,000 flight cycles after doing the modification in paragraph (c)(1) of this AD, perform detailed visual and high frequency eddy current inspections to find cracking of the skin at the upper aft and forward corners of the lower lobe cargo door cutout, according to Figure 5 of Boeing Alert Service Bulletin 747-53A2448, including Appendix A, dated September 28, 2000. Repeat these inspections at least every 3,000 flight cycles.

Alternative Methods of Compliance

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

Note 4:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Issued in Renton, Washington, on October 23, 2001.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.