[Federal Register Volume 64, Number 155 (Thursday, August 12, 1999)] [Proposed Rules] [Pages 43950-43953] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 99-20881] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. 99-NM-84-AD] RIN 2120-AA64 Airworthiness Directives; Boeing Model 737-200, -200C, -300, and -400 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 737- 200, -200C, -300, and -400 series airplanes, that currently requires repetitive visual inspections to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions, if necessary. That AD also provides an optional terminating action for certain repetitive inspections. This action would add requirements for repetitive high frequency eddy current (HFEC) inspections, and corrective actions, if necessary. This action also would mandate accomplishment of the previously optional terminating action. The actions specified by the proposed AD are intended to prevent fatigue cracking of the corners of the door frame and the cross beams of the aft cargo door, which could result in rapid depressurization of the airplane. DATES: Comments must be received by September 27, 1999. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-84-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. 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, Transport Airplane Directorate, 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 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 99-NM-84-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. 99-NM-84-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. [[Page 43951]] Discussion On November 30, 1998, the FAA issued AD 98-25-06, amendment 39- 10931 (63 FR 67769, December 9, 1998), applicable to certain Boeing Model 737-200, -200C, -300, and -400 airplanes, to require repetitive inspections to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions, if necessary. That action also provides an optional terminating action for the repetitive inspection requirement of that AD. That action was prompted by reports indicating that fatigue cracks have been detected in the corners of the door frame and the cross beams of the aft cargo door on several in-service airplanes, and by another report indicating that rapid depressurization occurred during flight on one of those airplanes. The requirements of that AD are intended to prevent fatigue cracking of the corners of the door frame and the cross beams of the aft cargo door, which could result in rapid depressurization of the airplane. Actions Since Issuance of Previous Rule Since the issuance of AD 98-25-06, the FAA has received a report indicating that during a high frequency eddy current inspection a one- inch crack was detected in the forward corner frame of the aft cargo door. Further investigation revealed a crack in the aft corner frame and cracks in the lower cross beam. No cracking was detected during a detailed visual inspection of these areas that was accomplished approximately 925 flight cycles prior to an incident of rapid depressurization of the airplane. In light of this information, the FAA has determined that the detailed visual inspections of the door frame and the cross beams of the aft cargo door required by the existing AD are not providing the degree of safety assurance necessary for the affected airplanes. 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 98-25-06 to continue to require repetitive visual inspections to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions, if necessary. This proposed AD would add requirements for repetitive high frequency eddy current (HFEC) inspections of the corners of the aft cargo door frame, and corrective actions, if necessary. This proposal also would mandate accomplishment of the previously optional terminating action. The HFEC inspections would be required to be accomplished in accordance with the procedures specified in Boeing 737 Nondestructive Test Manual, Part 6, Chapter 51-00-00 (Figure 4 or Figure 23). Modification of the door frame would be required to be accomplished in accordance with Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996. Repairs of the outer chord of the upper and lower cross beams would be required to be accomplished in accordance with a method approved by the Manager, Seattle ACO, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative. Other Relevant Rulemaking The FAA previously has issued AD 90-06-02, amendment 39-6489 (55 FR 8372, March 7, 1990), applicable to certain Boeing Model 737 series airplanes. AD 90-06-02 requires accomplishment of certain structural modifications, which constitutes terminating action for the repetitive inspection requirements of this proposed AD. Differences Between Service Bulletin and This Proposed ADAs stated in AD 98-25-06, operators should note that, unlike the procedures described in the service bulletin, this proposed AD would not permit further flight with stop-drilled cracks in the frame of the aft cargo door. The FAA has determined that, because of the safety implications and consequences associated with such cracking, any subject aft cargo door frame that is found to be cracked must be permanently repaired and modified prior to further flight. As stated in AD 98-25-06, operators should note that the effectivity listing of the service bulletin includes Boeing Model 737- 200 and -200C series airplanes having line numbers 6 through 873 inclusive. The applicability of this proposed AD includes not only those airplanes listed in the effectivity listing of the service bulletin, but also Boeing Model 737-200, -200C, -300, and -400 series airplanes; having line numbers 874 through 1642 inclusive; that have certain replacement doors installed and that have not been modified in accordance with Boeing Service Bulletin 737-52-1079. Operators also should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposed AD would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. Operators should note that, although the service bulletin describes accomplishment of a visual inspection of the corners of the door frame and the cross beams of the aft cargo door, for the reasons discussed previously, the FAA has determined that accomplishment of a visual inspection only is inadequate to detect cracking in certain areas. Therefore, this proposed AD would add repetitive high frequency eddy current inspections to detect cracking of the four corners of the aft cargo door frame. Operators should note that this AD proposes to mandate, within 4 years after the effective date of this AD, the modification of the door frame of the aft cargo door described in Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, as terminating action for the repetitive inspections of the door frame. The FAA has determined that long-term continued operational safety will be better assured by design changes to remove the source of the problem, rather than by repetitive inspections. Long-term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous continual inspections, has led the FAA to consider placing less emphasis on inspections and more emphasis on design improvements. The proposed modification is in consonance with these conditions. Cost Impact There are approximately 1,636 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 707 airplanes of U.S. registry would be affected by this proposed AD. The detailed visual inspections that currently are required by AD 98-25-06, and retained in this proposed AD, take approximately 2 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 inspections on U.S. operators is estimated to be $84,840, or $120 per airplane, per inspection cycle. The new high frequency eddy current inspections that are proposed in this AD action would take approximately 4 work [[Page 43952]] hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the new inspections proposed by this AD on U.S. operators is estimated to be $169,680, or $240 per airplane, per inspection cycle. The modification that is proposed in this AD action would take approximately 144 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $4,530 per airplane. Based on these figures, the cost impact of the modification proposed by this AD on U.S. operators is estimated to be $9,311,190, or $13,170 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. 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. Sec. 39.13 [Amended] 2. Section 39.13 is amended by removing amendment 39-10931 (63 FR 67769, December 9, 1998), and by adding a new airworthiness directive (AD), to read as follows: Boeing: Docket 99-NM-84-AD. Supersedes AD 98-25-06, Amendment 39- 10931. Applicability: The following airplane models, certificated in any category: Model 737-200 and -200C series airplanes, line numbers 6 through 873 inclusive; Model 737-200, -200C, -300, and -400 series airplanes; line numbers 874 through 1642 inclusive; equipped with an aft cargo door having Boeing part number (P/N) 65-47952-1 or P/N 65-47952-524; excluding: 1. Those airplanes on which that door has been modified in accordance with Boeing Service Bulletin 737-52-1079; or 2. Those airplanes on which the door assembly having P/N 65- 47952-524 includes four straps (P/N's 65-47952-139, 65-47952-140, 65-47952-141, and 65-47952-142) and a thicker lower cross beam web (P/N 65-47952-157). 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 (f)(1) 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 fatigue cracking of the corners of the door frame and the cross beams of the aft cargo door, which could result in rapid depressurization of the airplane, accomplish the following: Restatement of the Requirements of AD 98-25-06: Inspections and Corrective Actions (a) Within 90 days or 700 flight cycles after December 24, 1998 (the effective date of AD 98-25-06, amendment 39-10931), whichever occurs later, perform an internal detailed visual inspection to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, in accordance with Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996. (1) If no cracking is detected, accomplish the requirements of either paragraph (a)(1)(i) or (a)(1)(ii) of this AD. (i) Repeat the internal visual inspection thereafter at intervals not to exceed 4,500 flight cycles. Or (ii) Prior to further flight, modify the corners of the door frame and the cross beams of the aft cargo door in accordance with the service bulletin. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD. (2) If any cracking is detected in the upper or lower cross beams, prior to further flight, modify the cracked beam in accordance with paragraph III.C. of Part I of the Accomplishment Instructions of the service bulletin. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD for the repaired beam. (3) If any cracking is detected in the forward or aft upper door frame, prior to further flight, repair the frame and modify the corners of the door frame of the aft cargo door, in accordance with paragraph III.E. of Part I of the Accomplishment Instructions of the service bulletin, except as provided by paragraph (b) of this AD. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD for the upper door frame. Note 2: Cracks of the forward or aft upper door frame, regardless of length, must be repaired prior to further flight in accordance with paragraph III.E. of Part I of the Accomplishment Instructions of the service bulletin. (4) If any cracking is detected in the forward or aft lower door frame, prior to further flight, replace the damaged frame with a new frame, and modify the corners of the door frame of the aft cargo door, in accordance with paragraph III.F. of Part I of the Accomplishment Instructions of the service bulletin. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD for the lower door frame. (b) Where Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, specifies that certain repairs are to be accomplished in accordance with instructions received from Boeing, this AD requires that, prior to further flight, such repairs be accomplished in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. New Requirements of This AD: Inspections and Corrective Actions (c) If any cracking of the outer chord of the upper or lower cross beams of the aft cargo door is detected as a result of any inspection required by paragraph (a) of this AD, prior to further flight, repair in accordance with a method approved by the Manager, Seattle ACO, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. [[Page 43953]] (d) Within 4,500 flight cycles or one year after the effective date of this AD, whichever occurs later: Perform a high frequency eddy current inspection (HFEC) to detect cracking of the four corners of the door frame of the aft cargo door, in accordance with the procedures specified in Boeing 737 Nondestructive Test Manual, Part 6, Chapter 51-00-00 (Figure 4 or Figure 23) . (1) If no cracking of the corners of the door frame of the aft cargo door is detected, repeat the HFEC inspections thereafter at intervals not to exceed 4,500 flight cycles until accomplishment of the modification specified in paragraph (e) of this AD. (2) If any cracking of the corners of the door frame of the aft cargo door is detected, prior to further flight, replace the damaged frame with a new frame, and modify the four corners of the door frame, in accordance with Parts II and III of the Accomplishment Instructions of Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (d)(1) of this AD for that door frame. Terminating Action (e) Within 4 years after the effective date of this AD: Modify the four corners of the door frame and the cross beams of the aft cargo door, in accordance with Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of this AD. Note 3: Accomplishment of the modification required by paragraph (a) of AD 90-06-02, amendment 39-6489, is considered acceptable for compliance with paragraph (e) of this AD. Note 4: Modification of the corners of the door frame and the cross beams of the aft cargo door accomplished prior to the effective date of this AD in accordance with Boeing Service Bulletin 737-52-1079, dated December 16, 1983; Revision 1, dated December 15, 1988; Revision 2, dated July 20, 1989; Revision 3, dated May 17, 1990; or Revision 4, dated February 21, 1991; is considered acceptable for compliance with paragraph (e) of this AD. Alternative Methods of Compliance (f)(1) 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. (f)(2) Alternative methods of compliance, approved previously in accordance with AD 98-25-06, amendment 39-10931, are approved as alternative methods of compliance with this AD. 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 (g) 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 August 6, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-20881 Filed 8-11-99; 8:45 am] BILLING CODE 4910-13-P