[Federal Register Volume 61, Number 223 (Monday, November 18, 1996)] [Proposed Rules] [Pages 58669-58671] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-29417] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 96-NM-71-AD] RIN 2120-AA64 Airworthiness Directives; Boeing Model 747-200, -300, and -400 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 747-200, - 300, and -400 series airplanes. This proposal would require repetitive inspections to detect cracking of the front spar web of the center section of the wing, and repair, if necessary. This proposal is prompted by reports of fatigue cracking found in the front spar web. The actions specified by the proposed AD are intended to prevent the leakage of fuel into the forward cargo bay, as a result of fatigue cracking in the front spar web, which could result in a potential fire hazard. DATES: Comments must be received by December 30, 1996. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-71-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: Tamara Dow, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2771; fax (206) 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 96-NM-71-AD.'' The postcard will be date stamped and returned to the commenter. [[Page 58670]] Availability of NPRMs Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-71-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Discussion The FAA has received reports indicating that fatigue cracks have been found on several Boeing Model 747-100 series airplanes in the front spar web of the center section of the wing. Two operators reported cracks at the tangent point of the pocket fillet radius running vertically along the edge of the web stiffener. One crack was found while troubleshooting a whistling sound in the cabin that occurred during flight. These cracks were detected on airplanes that had accumulated between 13,932 and 24,264 total landings, and between 27,080 and 37,625 total hours time-in-service. The manufacturer evaluated trimmed sections of webs that contained cracks. This evaluation revealed that the cracks, which were propagated by fatigue, originated at the tangent point of the pocket fillet radius on the forward surface, spread aft through the thickness of the web, and then radiated vertically. Because fuel on Model 747-200, -300, and -400 series airplanes is located behind the front spar web, fuel could leak through these cracks into the forward cargo bay. This leakage, if not corrected, could result in a potential fire hazard. Explanation of Relevant Service Information The FAA has reviewed and approved Boeing Alert Service Bulletin 747-57A2298 Revision 1, dated September 12, 1996, which describes procedures for conducting repetitive high frequency eddy current (HFEC) inspections to detect cracking of the front spar web along the tangent point of the pocket fillet radii. It also describes procedures for repairing any cracking that is found during an inspection. Additionally, the service bulletin describes procedures for an optional HFEC inspection to confirm cracking, and repair if cracking is confirmed. Explanation of Requirements of Proposed AD 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 repetitive HFEC inspections to detect cracking of the front spar web along the tangent point of the pocket fillet radii., and repair, if necessary. These inspections and certain repairs would be required to be performed in accordance with the alert service bulletin described previously. Other repairs would be required to be accomplished in accordance with a method approved by the FAA. The proposed AD also would require that certain operators report initial inspection results, positive or negative, to the FAA. Due to a lack of information about the extent of cracking in the front spar web of airplanes that have accumulated less than 18,000 total landings, this information is needed to determine, among other things, how widespread this occurrence might be among airplanes in this category, the total number of accumulated landings when initial cracking may be occurring, the size of cracking, and other conditions that may contribute to cracking or its propagation. Interim Action This proposal is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking. Explanation of Applicability of Proposed AD This proposed AD would be applicable only to Boeing Model 747-200, -300, and -400 series airplanes. Model 747-100, 747SR, and 747SP series airplanes are not included in the applicability of this proposed AD because they have a dry bay located behind the front spar web. This would preclude the type of potential fire hazard situation addressed by this AD. In addition, if the subject fatigue cracking were to occur on these airplanes, the cabin pressure would vent through the front spar web and then the limiting access holes of the front spar; this would result in a loss of pressurization, but not sudden decompression. Differences Between the Proposed AD and the Alert Service Bulletin Operators should note that the alert service bulletin indicates that vertical cracks of 10 inches or greater in length, or cracks that extend in a diagonal direction (regardless of length), or cracks that would affect an existing repair, should be repaired in accordance with the manufacturer's instructions. However, the proposed AD would require that these types of cracks be repaired in accordance with a method approved by the FAA. Cost Impact There are approximately 485 Model 747-200, -300, and -400 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 105 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 48 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $302,400, or $2,880 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 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. [[Page 58671]] Sec. 39.13 [Amended] 2. Section 39.13 is amended by adding the following new airworthiness directive: Boeing: Docket 96-NM-71-AD. Applicability: Model 747-200, -300, and -400 series airplanes, up to and including line number 744, certificated in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 prevent the leakage of fuel into the forward cargo bay through fatigue cracks in the front spar web, which could result in a potential fire hazard, accomplish the following: (a) Perform a high frequency eddy current (HFEC) inspection to detect cracking of the front spar web of the center section of the wing, in accordance with Boeing Alert Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996, at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable. (1) For airplanes that have accumulated 12,000 to 17,999 total landings as of the effective date of this AD: Within 12 months after the effective date of this AD. Perform this inspection again prior to the accumulation of 18,000 total landings or within 1,400 landings, whichever occurs later, and thereafter at intervals not to exceed 1,400 landings. (2) For all other airplanes: Prior to the accumulation of 18,000 total landings or within 12 months after the effective date of this AD, whichever occurs later, and thereafter at intervals not to exceed 1,400 landings. (b) Except as provided by paragraph (c) of this AD, if any cracking is detected during an inspection required by paragraph (a) of this AD, prior to further flight, repair in accordance with paragraph (b)(1) or (b)(2) of this AD, as applicable. Thereafter repeat the HFEC inspection required by paragraph (a) of this AD at intervals not to exceed 1,400 landings. (1) If any vertical crack is found that is less than 10 inches in length, repair in accordance with Boeing Alert Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996. (2) If any vertical crack is found that is 10 inches or greater in length; or if any crack is found that has extended in a diagonal direction (regardless of length); or if any crack is found that would affect an existing repair; repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. (c) In lieu of accomplishing the procedures specified in paragraph (b) of this AD: If a crack in the front spar web is detected during an HFEC inspection required by paragraph (a) of this AD, prior to further flight, operators may accomplish the procedures for an optional HFEC inspection to confirm cracking, as described in paragraph III.D.2. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996. (1) If this optional inspection is accomplished and cracking is not confirmed, thereafter repeat the HFEC inspection specified in paragraph (a) of this AD at intervals not to exceed 1,400 landings. (2) If this optional inspection is accomplished and confirms cracking, prior to further flight, repair the cracking in accordance with paragraph (b)(1) or (b)(2) of this AD, as applicable. (d) For airplanes that are required to perform an initial HFEC inspection in accordance with paragraph (a)(1) of this AD: Within 30 days after accomplishing the initial inspection, submit a report of inspection results, negative or positive, that includes the information identified in paragraphs (d)(1) through (d)(5) of this AD, to the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; fax (206) 227-1181. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056. (1) Airplane serial number. (2) Total number of landings accumulated. (3) Total number of hours time-in-service accumulated. (4) Location, size and orientation of each crack. (5) Whether fuel leakage resulted from the crack. (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 Directorate. 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 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (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 November 8, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-29417 Filed 11-15-96; 8:45 am] BILLING CODE 4910-13-U