01-32196. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-300, 747SP, and 747SR 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 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-300, 747SP, and 747SR series airplanes. This proposal would require one-time inspections for cracking in certain upper deck floor beams and follow-on actions. This action is necessary to find and fix cracking in certain upper deck floor beams. Such cracking could extend and sever floor beams adjacent to the body frame and result in rapid depressurization of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by February 19, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-34-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. 2001-NM-34-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 2001-NM-34-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. 2001-NM-34-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports of fatigue cracking on the left and right ends of the upper chord of the station (STA) 340 upper deck floor beam on several Boeing Model 747 series airplanes. Also, during fatigue tests on a Boeing 747SR test airplane, multiple cracks up to 0.3 inch long were found in both the left and right ends of the upper chord of the STA 340 floor beam. On certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-300, 747SP, and 747SR series airplanes, the STA 340 upper deck floor beam, as well as the floor beam at STA 360, are made from 7075 aluminum. Other upper deck floor beams on these models are made from 2024 aluminum, which is known to be more durable than 7075 aluminum against fatigue. Cracking of the upper deck floor beam at STA 340 or STA 360, if not corrected, could extend and sever floor beams adjacent to the body frame and result in rapid depressurization of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2459, dated January 11, 2001, which describes procedures for one-time detailed visual and open-hole high frequency eddy current (HFEC) inspections for cracking in the upper deck floor beams at STA 340 and STA 360, and follow-on actions. The follow-on actions consist of repair of any cracking found during the inspections or, if no cracking is found, modification of the upper deck floor beams. These follow-on actions are described below:

• The repair described in the service bulletin is identified as a “time-limited repair” and includes removing certain fasteners and the existing strap, performing open-hole HFEC inspections of the chord and web, stop-drilling web cracks, replacing the outboard section of the web, if necessary, and installing new straps. The service bulletin specifies that the time-limited repair must be replaced with a permanent repair after a certain amount of time and that operators are to contact Boeing for instructions for such permanent repair.
• The modification described in the service bulletin involves removing the existing straps, and installing new straps. Also, the service bulletin notes that, if this modification is not accomplished immediately following the inspections described previously, the inspections must be repeated one time, immediately before the modification is accomplished.

The service bulletin also specifies accomplishment of repetitive post-repair or post-modification open-hole HFEC inspections for cracking of fastener holes common to the upper chord, reinforcement straps, and the body frame; or, alternatively, surface HFEC inspections for cracking along the lower edge of the upper chord of the floor beam at the intersection with the body frame. However, the service bulletin does not provide detailed instructions for these inspections or for repairs of any cracking that is found.

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

Operators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, including instructions for a permanent repair, if necessary, this proposal would require such repairs to be accomplished according to a method approved by the FAA, or according to 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.

Also, while the service bulletin specifies that instructions for post-modification/repair inspections will be included in future revisions of the service bulletin, paragraph (d) of the proposed AD would require post-modification/repair inspections to be done according to a method approved by the FAA, or according to 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.

Cost Impact

There are approximately 539 airplanes of the affected design in the worldwide fleet. The FAA estimates that 168 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 8 work hours per airplane to accomplish the initial inspections, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of these proposed inspections on U.S. operators is estimated to be $80,640, or $480 per airplane.

It would take approximately 24 work hours per airplane to accomplish the modification or permanent repair, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed modification or repair on U.S. operators is estimated to be $241,920 or $1,440 per airplane.

It would take approximately 8 work hours per airplane to accomplish the post-modification/repair inspections, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed post-modification/repair inspections on U.S. operators is estimated to be $80,640 or $480 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 2001-NM-34-AD.

Applicability: Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-300, 747SP, and 747SR series airplanes; line numbers 1 through 810 inclusive; certificated in any category; and NOT equipped with a nose cargo door.

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 (e) 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 in certain upper deck floor beams, which could extend and sever floor beams adjacent to the body frame and result in rapid depressurization of the airplane, accomplish the following:

Inspections

(a) At the compliance time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable, perform one-time detailed visual and open-hole high frequency eddy current (HFEC) inspections for cracking in the upper deck floor beams at station (STA) 340 and STA 360, according to Boeing Alert Service Bulletin 747-53A2459, dated January 11, 2001.

(1) For airplanes with 22,000 or fewer total flight cycles as of the effective date of this AD: Do the inspections prior to the accumulation of 16,000 total flight cycles, or within 1,500 flight cycles after the effective date of this AD, whichever is later.

(2) For airplanes with more than 22,000 total flight cycles as of the effective date of this AD: Do the inspections within 500 flight cycles after the effective date of this AD.

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.”

Modification

(b) If no crack is found during the inspections per paragraph (a) of this AD: Within 5,000 flight cycles after the initial inspections, modify the upper deck floor beams at STA 340 and STA 360, according to Boeing Alert Service Bulletin 747-53A2459, dated January 11, 2001. If this modification is not accomplished before further flight after the inspections required by paragraph (a) of this AD, those inspections must be repeated one time, immediately before accomplishing the modification in this paragraph. If any crack is found during these repeat inspections, before further flight, accomplish paragraph (c)(2) of this AD.

Repair

(c) If any crack is found during the inspections per paragraph (a) of this AD: Before further flight, repair according to either paragraph (c)(1) or (c)(2) of this AD.

(1) Accomplish repairs according to paragraphs (c)(1)(i) and (c)(1)(ii) of this AD.

(i) Accomplish a temporary repair (including removing certain fasteners and the existing strap, performing open-hole HFEC inspections of the chord and web, stop-drilling web cracks, replacing the outboard section of the web, if applicable, and installing new straps) according to Boeing Alert Service Bulletin 747-53A2459, dated January 11, 2001; except where the service bulletin specifies to contact Boeing for appropriate action, repair according to a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or according to 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 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. AND,

(ii) Within 18 months or 1,500 flight cycles after installation of the temporary repair according to paragraph (c)(1)(i) of this AD, whichever is first, do paragraph (c)(2) of this AD.

(2) Accomplish a permanent repair according to a method approved by the Manager, Seattle ACO, or according to data meeting the type certification basis of the airplane approved by a Boeing Company DER 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.

Note 3:

Boeing Alert Service Bulletin 747-53A2459, dated January 11, 2001, does not contain instructions for permanent repairs.

Repetitive Inspections: Post-Modification/Repair

(d) Within 15,000 flight cycles after modification of the upper deck floor beams per paragraph (b) of this AD, or repair of the upper deck floor beams per paragraph (c) of this AD, as applicable: Perform either open-hole HFEC inspections for cracking of fastener holes common to the upper chord, reinforcement straps, and the body frame; or surface HFEC inspections for cracking along the lower edge of the upper chord of the floor beam at the intersection with the body frame; and repeat these inspections at the interval specified in paragraph (d)(1) or (d)(2) of this AD, as applicable. Perform these inspections and repair any cracking found during these inspections according to a method approved by the Manager, Seattle ACO, or according to data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings. For an inspection or 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.

(1) If the most recent inspection used the surface HFEC method: Repeat the inspection within 1,000 flight cycles.

(2) If the most recent inspection used the open-hole HFEC method: Repeat the inspection every 3,000 flight cycles.

Note 4:

There is no terminating action at this time for the repetitive post-modification/repair inspections according to paragraph (d) of this AD, and instructions for these inspections are not provided in Boeing Alert Service Bulletin 747-53A2459, dated January 11, 2001.

Alternative Methods of Compliance

(e) 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 5:

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

(f) 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 December 26, 2001.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.