AD 96-04-03

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 737-200 and -200C airplanes, that currently requires installation of fail-safe straps onto the engine inlet attach ring of the nose cowl. This amendment requires repetitive inspections to detect cracking of the attach ring of the nose cowl, and replacement of cracked attach rings. Replacement with an improved attach ring, if accomplished, would terminate the requirement to inspect the attach ring repetitively. This amendment is prompted by the development of an improved attach ring that eliminates the need for repetitive inspections. The actions specified by this AD are intended to prevent cracking of the attach ring of the nose cowl, which could result in separation of the nose cowl from the engine following failure of a turbine blade.

Final rule

96-04-03 BOEING: Amendment 39-9514. Docket 95-NM-155-AD. Supersedes AD 95-08-08, Amendment 39-9197. \n\n\tApplicability: Model 737-200 and -200C airplanes equipped with dB Partners Hush Kit having attach ring, part number 65ND-54301-1, installed in accordance with Supplemental Type Certificate (STC) SA5730NM, certificated in any category. \n\n\tNOTE 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 notbeen eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent separation of the nose cowl from the engine following turbine blade failure, accomplish the following: \n\n\t(a)\tWithin 30 days after May 2, 1995 (the effective date of AD 95-08-08, amendment 39-9197), install fail-safe straps onto the attach ring, part number (P/N) 65ND-54301-1, of the nose cowl in accordance with Nordam Service Bulletin SB 71-03, dated March 17, 1995, or Revision 1, dated June 16, 1995. \n\n\t(b)\tAs of the effective date of this AD: Prior to further flight following each incident of turbine blade failure, perform a detailed visual inspection to detect cracking of the attach ring of the nose cowl. Fail-safe straps must be removed to perform this inspection. \n\n\t\t(1)\tIf no cracking is detected, prior to further flight, reinstall the fail-safe straps in accordance with Nordam Service Bulletin SB 71-03, dated March 17, 1995, or Revision 1 dated June 16, 1995. \n\n\t\t(2)\tIf any cracking is detected, prior to further flight, accomplish the requirements of either paragraph (b)(2)(i) or (b)(2)(ii) of this AD. \n\n\t\t\t(i)\tReplace the cracked attach ring with an attach ring having P/N 65ND- 54301-1 in accordance with STC SA5730NM, and reinstall the fail-safe strap in accordance with Nordam Service Bulletin SB 71-03, dated March 17, 1995, or Revision 1, dated June 16, 1995. Repeat the visual inspection of the attach ring prior to further flight following each incident of turbine blade failure. Or \n\n\t\t\t(ii)\tReplace the cracked attach ring with an attach ring having P/N 65ND- 54301-5 in accordance with Nordam Service Bulletin SB 71-04, Revision 1, dated June 16, 1995. After this replacement is accomplished, the inspections required by this paragraph may be terminated. \n\n\t(c)\tInstallation of an attach ring having P/N 65ND-54301-5 constitutes terminating action for the repetitive inspections required by paragraph (b) of this AD. \n\n\t(d)\tAs of May 2, 1995 (the effective date of AD 95-08-08), fail-safe straps must be installed onto the attach ring, P/N 65ND-54301-1, of the nose cowl in accordance with Nordam Service Bulletin SB 71-03, dated March 17, 1995, or Revision 1, dated June 16, 1995, prior to installation of STC SA5730NM on any airplane. \n\n\t(e)\tAn 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 Aircraft Certification Office (ACO), FAA, Transport Airplane 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. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\n\t(f)\tSpecial 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. \n\n\t(g)\tThe actions shall be done in accordance with the following Nordam service bulletins, as applicable, which contain the specified effective pages: \n\n\nService Bulletin\nReference and Date\n\nPage Number\nRevision Level\nShown on Page\nDate\nShown on Page\nSB 71-03,\n1-12\nOriginal\t\nMarch 17, 1995\nSB 71-03,\nRevision 1,\nJune 16, 1995\n1-11\n\n12\n1\n\nOriginal\nJune 16, 1995\n\nMarch 17, 1995\nSB 71-04,\nRevision 1,\nJune 16, 1995\n1, 2\n\n3-18\nOriginal\n\n1\nMay 22, 1995\n\nJune 16, 1995 \n\nThe incorporation by reference of Nordam Service Bulletin SB 71-03, dated March 17, 1995, was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of May 2, 1995 (60 FR 19157, April 17, 1995) The incorporation by reference of the remainder of the service documents listed above is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from The Nordam Group, 624 East 4th Street, Tulsa, Oklahoma 74120. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(h)\tThis amendment becomes effective on March 22, 1996.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 95-08-08, amendment 39-9197 (60 FR 19157, April 17, 1995), which is applicable to certain Boeing Model 737-200 and -200C airplanes, was published in the Federal Register on November 22, 1995 (60 FR 57840). The action proposed to supersede AD 95-08-08 to continue to require installation of fail-safe straps onto the engine inlet attach ring of the nose cowl. The action also proposed to require repetitive inspections to detect cracking of the attach ring of the nose cowl, and replacement of cracked attach rings. That action also proposed to provide an optional terminating action (installation of an improved attach ring) for the repetitive inspections. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the two comments received. \n\n\tBoth commenters support the proposedrule. \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed. \n\n\tThere are approximately 46 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 1 airplane of U.S. registry will be affected by this AD.\n \n\tThe replacement action that is currently required by AD 95-08-08 takes approximately 8 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will be provided at no cost to the operator. Based on these figures, the cost impact of the currently required actions on the sole U.S. operator is estimated to be $480 per airplane. \n\n\tThe inspection that is required by this new AD will take approximately 10 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the newrequirements of this AD is estimated to be $600 per airplane, per inspection cycle. \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tThe regulations adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."\n\n List of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:\n\n PART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 USC 106(g), 40113, 44701. § 39.13 - (Amended) \n\n\t2. Section 39.13 is amended by removing amendment 39-9197 (60FR 19157, April 17, 1995), and by adding a new airworthiness directive (AD), amendment 39-9514, to read as follows: