Federal Aviation Administration, DOT.
Notice of proposed rulemaking (NPRM).
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 777 series airplanes. This proposal would require repetitive inspections for cracking of the floor beam structure located at body station 246; and repair, if necessary. This action is necessary to find and fix such cracking, which could extend and sever the floor beam, resulting in rapid depressurization of the airplane and consequent collapse of the floor structure. This action is intended to address the identified unsafe condition.
Comments must be received by August 5, 2002.
Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-30-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: firstname.lastname@example.org. Comments sent via fax or the Internet must contain “Docket No. 2001-NM-30-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.Start Further Info
FOR FURTHER INFORMATION CONTACT:
Suzanne Masterson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2772; fax (425) 227-1181.End Further Info End Preamble Start Supplemental Information
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-30-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-30-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
The FAA has received numerous reports of fatigue cracking of the floor beam structure located at body station (BS) 246 on several Boeing Model 777 series airplanes. Investigation revealed that the fatigue is caused by high bending stresses in the forward and aft directions of the BS 246 floor beam during flight. The high stress is due to the temperature difference between the fuselage skin and the floor structure, which results in contraction of the fuselage skin and subsequent cracking of the floor structure. Additionally, cracked stiffeners and mid-chord cracking of the left and/or right body line (BL) 38.5 were found. Several web cracks were also found at left and right BL 32.5. Such cracking could extend and sever the floor beam, resulting in rapid depressurization of the airplane and consequent collapse of the floor structure.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Service Bulletin 777-53-0031, dated October 26, 2000, which describes procedures for a detailed inspection for cracking of the floor beam structure located at BS 246. The inspection includes the floor beam clips, stiffeners, webs, and chords. The service bulletin also describes procedures for a low frequency eddy current (LFEC) inspection for cracking of the upper flange of the mid-chord at left and right BL 38.5. As an alternative to the LFEC inspection, the service bulletin allows for a detailed inspection of those areas. The alternative inspection necessitates removal of certain equipment and floor panels installed on the aft side of the BS 246 floor beam for access. If cracking is found, the service bulletin describes procedures for repair, as specified in the Boeing Model 777 Structural Repair Start Printed Page 41641Manual. The service bulletin also specifies obtaining repair data from Boeing for certain cracking. 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.
Difference Between This Proposed AD and the Service Bulletin
Although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repairs/inspection procedures, this proposed AD would require such repairs/inspection procedures 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.
This is considered to be interim action. The manufacturer has advised that it currently is developing a modification to address the unsafe condition that will reduce or eliminate the need for the requirement imposed by this proposed AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking.
There are approximately 184 airplanes of the affected design in the worldwide fleet. The FAA estimates that 81 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1 work hour per airplane to accomplish the proposed inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the inspections proposed by this AD on U.S. operators is estimated to be $4,860, or $60 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.
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.Start List of Subjects
List of Subjects in 14 CFR Part 39
- Air transportation
- Aviation 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:Start Part
PART 39—AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
2. Section 39.13 is amended by adding the following new airworthiness directive:
Boeing: Docket 2001-NM-30-AD.
Applicability: All Model 777 series airplanes, certificated in any category.
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 (c) 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 floor beam structure located at body station (BS) 246, which could extend and sever the floor beam, resulting in rapid depressurization of the airplane and consequent collapse of the floor structure, accomplish the following:
(a) Within 2,500 flight cycles or 5,000 flight hours after the effective date of this AD, whichever is first: Do the inspections for cracking of the floor beam structure located at BS 246 as specified in paragraphs (a)(1) and (a)(2) of this AD, per Boeing Service Bulletin 777-53-0031, dated October 26, 2000. Repeat the inspections every 2,500 flight cycles or 5,000 flight hours, whichever is first.
(1) Do a detailed inspection for cracking of the floor beam structure (including floor beam clips, stiffeners, webs, and chords) located at BS 246.
(2) Do a low frequency eddy current (LFEC) inspection for cracking of the upper flange of the mid-chord at left and right body lines 38.5: As an alternative to the LFEC inspection a detailed inspection of this area may be done, provided that removal of certain equipment and floor panels installed on the aft side of the BS 246 floor beam is done to obtain access.
For the purposes of this AD, a detailed 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.”
(b) If any crack is found during any inspection per paragraph (a) of this AD: Before further flight, repair per Boeing Service Bulletin 777-53-0031, dated October 26, 2000; except where the service bulletin specifies to contact Boeing for disposition of certain repairs, 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 as required by this paragraph, Start Printed Page 41642the approval must specifically reference this AD.
There is no terminating action currently available for the repetitive inspections required by this AD.
Alternative Methods of Compliance
(c) 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.
Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.
Special Flight Permit
(d) 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 June 12, 2002.
Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 02-15368 Filed 6-18-02; 8:45 am]
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