AD 97-19-08

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires ultrasonic inspection of certain engine strut diagonal brace lugs for cracks, and replacement, if necessary. This amendment requires new repetitive inspections to detect discrepancies of the diagonal brace lugs, and rework of the diagonal brace lug, if necessary. In lieu of accomplishing the rework for certain cases, this amendment provides for an option to defer the rework by accomplishing repetitive inspections and resealing the bushing. This amendment also provides for an optional terminating modification for repetitive inspections. This amendment is prompted by additional reports of fatigue cracking in the diagonal brace lug. The actions specified in this AD are intended to prevent such fatigue cracking, which could result in failure of the strut and consequent separation of the engine from the airplane.

Final rule; request for comments.

97-19-08 BOEING: Amendment 39-10128. Docket 97-NM-180-AD. Supersedes AD 89-07-15, Amendment 39-6167.\n \n\tApplicability: Model 747 series airplanes having line positions 1 through 1046 inclusive; equipped with Pratt & Whitney Model JT9D series engines, General Electric Model CF6-45 and -50 series engines, or Rolls Royce Model RB211 series engines; 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 (g)(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.\n \n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent fatigue cracking in the diagonal brace lug, which could result in failure of the strut and consequent separation of the engine from the airplane, accomplish the following: \n\n\t(a) For airplanes identified as Groups 1, 2, 3, and 4 in Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997: Perform a detailed visual and ultrasonic inspection to detect cracking, corrosion, and migrated or rotated bushings of the diagonal brace lugs, in accordance with and at the times specified in Table 1 of Figure 1 of the alert service bulletin; except that where the alert service bulletin states that an inspection is to be performed within a specified number of days after receipt of the alert service bulletin, the inspection shall be accomplished within that number ofdays after the effective date of this AD. Thereafter, repeat the inspections of the diagonal brace lug as specified in paragraph (a)(1) or (a)(2) of this AD, as applicable. After the effective date of this AD, only Revision 5 of the alert service bulletin shall be used.\n \n\t\t(1) For the aft diagonal brace lug: Repeat the detailed visual and ultrasonic inspections thereafter at intervals not to exceed those specified in paragraph (d) or (e) in Table 1 of Figure 1 of the alert service bulletin, as applicable. \n\n\t\t(2) For the forward diagonal brace lug: Repeat the detailed visual and ultrasonic inspections thereafter at intervals not to exceed 600 landings. These inspections on the forward diagonal brace lug must be accomplished in accordance with 747 Non-Destructive Test (NDT) Manual D6-7170, Part 4, Subject 54-40-05. \n\n\tNOTE 2: Where there are differences between the AD and the referenced alert service bulletin, the AD prevails. \n\t(b) For airplanes identified as Groups 3, 4, and 5 in Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997: Perform a detailed visual and ultrasonic inspection to detect cracking, corrosion, or migrated or rotated bushings of the diagonal brace lugs, in accordance with and at the times specified in Table II of Figure 1 of the alert service; except that where the alert service bulletin states that an inspection is to be performed within a specified number of days after receipt of the alert service bulletin, the inspection shall be accomplished within that number of days after the effective date of this AD. Repeat the detailed visual and ultrasonic inspections thereafter at intervals not to exceed 1,000 flight cycles. After the effective date of this AD, only Revision 5 of the alert service bulletin shall be used.\n \n\t(c) If any migrated or rotated bushing is detected during any of the inspections required by paragraph (a) or (b) of this AD, prior to further flight, rework the diagonal brace lug, inaccordance with Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997; except as provided in paragraph (d) of this AD. Thereafter, repeat the detailed visual and ultrasonic inspections required by paragraph (a) of this AD prior to the accumulation of 5,000 landings and/or repeat the detailed visual and ultrasonic inspections required by paragraph (b) of this AD prior to the accumulation of 9,000 landings. If the lug bore diameter is not within the rework limits, prior to further flight, replace the diagonal brace or repair it, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(d) In lieu of accomplishing the requirements of paragraph (c) of this AD, perform an ultrasonic inspection to detect cracking or corrosion of the diagonal brace lug, in accordance with Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997. \n\n\t\t(1) If no other damage is detectedduring the inspection required by paragraph (d) of this AD, prior to further flight, reseal the bushings in accordance with the alert service bulletin; and thereafter, repeat the inspections of the diagonal brace lug as specified in paragraph (d)(1)(i) or (d)(1)(ii) of this AD, as applicable. Within 15 or 18 months (as applicable in the alert service bulletin) since the initial migrated or rotated bushing was detected, rework the diagonal brace lug in accordance with the alert service bulletin; and thereafter, repeat the detailed visual and ultrasonic inspections required by paragraph (a) of this AD prior to the accumulation of 5,000 landings and/or repeat the detailed visual and ultrasonic inspections required by paragraph (b) of this AD prior to the accumulation of 9,000 landings. If the lug bore diameter is not within the rework limits, prior to further flight, replace the diagonal brace or repair it, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t\t\t(i) For the aft diagonal brace lug: Repeat the detailed visual and ultrasonic inspections required by paragraphs (a) and (b) of this AD thereafter at intervals not to exceed those specified in paragraph (d) or (e) in Table 1 and paragraph (d) of Table II of Figure 1 of the alert service bulletin, as applicable; except that the repetitive detailed visual inspections are required within 9 months following accomplishment of the resealing.\n \n\t\t\t(ii) For the forward diagonal brace lug: Repeat the detailed visual and ultrasonic inspections required by paragraphs (a) and (b) of this AD thereafter at the repetitive intervals specified in those paragraphs, as applicable; except that the repetitive detailed visual inspections are required within 9 months following accomplishment of the resealing. These inspections on the forward diagonal brace lug must be accomplished in accordance with 747 NDT Manual D6-7170, Part 4, Subject 54-40-05. \n\n\t\t(2) If any cracking or corrosion is detected during the inspection required by paragraph (d) of this AD, prior to further flight, rework the diagonal brace lug in accordance with the alert service bulletin; and thereafter, repeat the detailed visual and ultrasonic inspections required by paragraph (a) of this AD prior to the accumulation of 5,000 landings and/or repeat the detailed visual and ultrasonic inspections required by paragraph (b) of this AD prior to the accumulation of 9,000 landings. If the lug bore diameter is not within the rework limits, prior to further flight, replace the diagonal brace or repair it, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(e) If any cracking or corrosion is detected during any of the inspections required by paragraph (a) or (b) of this AD, prior to further flight, rework the diagonal brace lug in accordance with Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997; and thereafter, repeat the detailed visual and ultrasonic inspections required by paragraph (a) of this AD prior to the accumulation of 5,000 landings and/or repeat the detailed visual and ultrasonic inspections required by paragraph (b) of this AD prior to the accumulation of 9,000 landings. If the lug bore diameter is not within the rework limits, prior to further flight, replace the diagonal brace or repair it, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(f) Accomplishment of the strut/wing modification in accordance with Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26,1997, constitutes terminating action for the repetitive inspection requirements of this AD. \n\n\t(g) (1) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved bythe 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\t(g) (2) Alternative methods of compliance, approved previously in accordance with AD 89-07-15, amendment 39-6167, and AD 95-10-16, amendment 39-9233; are not considered to be approved as alternative methods of compliance with this AD. \n\n\tNOTE 3: 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(h) 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.\n \n\t(i) The actions shall be done in accordance with Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997. This incorporation by reference was 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 Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. 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(j) This amendment becomes effective on September 29, 1997.

On March 14, 1989, the FAA issued AD 89-07-15, amendment 39-6167 (54 FR 11693, March 22, 1989), applicable to certain Boeing Model 747 series airplanes, to require ultrasonic inspection of certain engine strut diagonal brace lugs for cracks, and replacement, if necessary. That action was prompted by reports of cracked diagonal braces. The actions required by that AD are intended to prevent overloading of the remaining strut attach points and possible structural damage.\n\nActions Since Issuance of Previous Rule\n\n\tSince the issuance of that AD, the FAA has received several reports of six additional diagonal braces with cracks in one lug of the aft clevis on Boeing Model 747 series airplanes. These incidents occurred following accomplishment of the optional terminating action specified in AD 89-07-15.\n\n\tOne diagonal brace, which had 3,386 flight cycles, had a crack from the bore to the part edge in the aft lug. The second diagonal brace, which had 5,206 flight cycles, had one lug in the aft clevis completely fractured. The third diagonal brace, which had 13,964 flight cycles, had a crack less than 0.10 inch in the aft lug bore. The fourth diagonal brace, which had 1,275 flight cycles, had a crack from the bore to the part edge in the aft lug. The fifth diagonal brace, which had approximately 3,360 flight cycles, had a through thickness crack in the lug. The sixth diagonal brace, which had approximately 8,350 flight cycles, had a crack in the aft lug. The length of the cracks for the fifth and sixth diagonal braces is not known. (The above mentioned flight cycles refer to cycles following accomplishment of the rework.)\n\n\tInvestigation revealed that the apparent cause of these cracks was attributed to fatigue, which may initiate at lug bore corrosion pits or other lug surface anomalies. Fatigue cracking in the diagonal brace lugs, if not detected and corrected in a timely manner, could result in failure of the strut and consequent separation of the engine from the airplane.\n\nDiscussion of Relevant Service Information\n\n\tSubsequent to the finding of this new cracking, the manufacturer issued, and the FAA reviewed and approved, Boeing Alert Service Bulletin 747-54A2126, Revision 5, dated June 26, 1997. The revised alert service bulletin describes procedures for new repetitive detailed visual and ultrasonic inspections to detect cracking, corrosion, and migrated or rotated bushings of the diagonal brace lugs, and rework of the diagonal brace lug or a follow-on ultrasonic inspection, if necessary. In lieu of the rework for certain cases, the revised alert service bulletin also describes procedures for resealing the bushing and follow-on repetitive inspections. In addition, the revised alert service bulletin provides procedures for modification of the strut/wing, which would eliminate the need for repetitive inspections. The revised alert service bulletin also expands the effectivity listing to include additional airplanes that are subject to the addressed unsafe condition.\n\nExplanation of Requirements of Rule\n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of this same type design, this AD supersedes AD 89-07-15 to require new repetitive detailed visual and ultrasonic inspections to detect cracking, corrosion, and migrated or rotated bushings of the diagonal brace lugs, and rework of the diagonal brace lugs, if necessary. In lieu of accomplishing the rework (prior to further flight) for certain cases where no cracks or corrosion is detected, this AD provides operators with an option to defer the rework for a short period of time by accomplishing repetitive inspections and resealing the bushing. This AD also provides procedures for modification of the strut/wing, which would constitute terminating action for the repetitive inspections requirements. In addition, this AD expands the applicability of the existing AD to includeadditional airplanes.\n\nDetermination of Rule's Effective Date\n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.\n\nComments Invited\n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factualinformation that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.\n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.\n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-NM-180-AD." The postcard will be date stamped and returned to the commenter.\n\nRegulatory Impact\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\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared andplaced in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."\n\nList 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\nPART 39 - AIRWORTHINESS DIRECTIVES\n\n\t1. The authority citation for part 39 continues to read as follows:\n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701.\n\n§ 39.13 - (Amended)\n\n\t2. Section 39.13 is amended by removing amendment 39-6167 (54 FR 11693, March 22, 1989), and by adding a new airworthiness directive (AD), amendment 39-10128, to read as follows: