AD 99-08-01

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires repetitive detailed visual inspections for corrosion, and repetitive high frequency eddy current (HFEC) inspections for cracks, of the upper link assembly on the number 2 and number 3 engine struts, and corrective actions, if necessary. This amendment is prompted by reports of corrosion and cracks located at the four fasteners that attach to the aft end to the upper link assembly on the number 2 and number 3 engine struts. The actions specified by this AD are intended to prevent failure of the upper link due to cracking or corrosion, subsequent damage to other strut support structure, and in-flight separation of an engine from the airplane.

Final rule

99-08-01 BOEING: Amendment 39-11105. Docket 97-NM-326-AD. \n\n\tApplicability: Model 747 series airplanes, line positions 1 through 886 inclusive; equipped with Pratt & Whitney JT9D-3 or -7, or General Electric CF6-45 or -50 engine struts; 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 not been eliminated, the request should include specific proposed actions toaddress it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent failure of the upper link due to cracking or corrosion, subsequent damage to other strut support structure, and in-flight separation of an engine from the airplane, accomplish the following: \n\n\t(a)\tPerform a detailed visual inspection for corrosion, and a high frequency eddy current (HFEC) inspection for cracks, of the upper link assembly on the number 2 and number 3 engine struts, in accordance with Boeing Alert Service Bulletin 747-54A2187, dated May 22, 1997, at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD. \n\n\t\t(1)\tWithin 6,000 total flight cycles, or 8 years after the date of manufacture of the airplane, whichever occurs first. \n\n\t\t(2)\tWithin 600 flight cycles, or 6 months after the effective date of this AD, whichever occurs first. \n\n\t(b)\tIf no crack or corrosion is detected during any inspection required by paragraph (a) of this AD, repeat the inspections specified in paragraph (a) of this AD, thereafter, at intervals not to exceed 18 months. \n\n\t(c)\tIf any crack or corrosion is detected during any inspection required by this AD, prior to further flight, accomplish either paragraph (c)(1) or (c)(2) of this AD, in accordance with Boeing Alert Service Bulletin 747-54A2187, dated May 22, 1997. Thereafter, repeat the inspections required by paragraph (a) of this AD, at intervals not to exceed 6,000 flight cycles or 8 years, whichever occurs first. \n\n\t\t(1)\tRepair the upper link within the limits specified in the alert service bulletin, in accordance with Part 2 of the Accomplishment Instructions of the alert service bulletin. (Complete corrosion and crack removal must be achieved within the limits specified in the alert service bulletin.)\tOr \n\n\t\t(2)\tReplace the upper link with a new upper link assembly, in accordance with Part 3 of the Accomplishment Instructions of the alert service bulletin. \n\n\t(d)\tAccomplishment ofthe modifications required in AD 95-13-07, amendment 39-9287 (for General Electric CF6-45 or -50 engine struts); or AD 95-10-16, amendment 39-9233 (for Pratt & Whitney JT9D-3 or -7 engine struts); constitutes terminating action for the requirements of this AD. \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)\tExcept as provided by paragraph (d) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-54A2187, dated May 22, 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(h)\tThis amendment becomes effective on May 12, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes was published in the Federal Register on April 9, 1998 (63 FR 17344). That action proposed to require repetitive detailed visual inspections for corrosion, and repetitive high frequency eddy current (HFEC) inspections for cracks, of the upper link assembly on the number 2 and number 3 engine struts, and corrective actions, if necessary. \n\nComments Received \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\nSupport for Proposed Rule \n\n\tTwo commenters support the proposed rule. \n\nRequest to Revise Compliance Time for the Initial Inspections of Certain Airplanes \n\n\tOne commenter, Boeing, notes that Chapter 54-00-01 of the Overhaul Manual (OHM) doesnot provide repair instructions other than instructions for replacement of the upper link aft fitting or the upper link tube. For airplanes with upper link assemblies that were overhauled in accordance with Chapter 54-00-01 of the OHM, and on which the four aft end attach bolts were installed with sealant, FLAG NOTE 1 of Figure 1 of Boeing Alert Service Bulletin 747-54A2187, dated May 22, 1997 (which is referenced in the proposed AD as the appropriate source of service information for accomplishment of the required inspections) recommends that the initial inspection be accomplished within 6,000 flight cycles or 8 years after the upper link assembly was overhauled. \n\n\tFrom this comment, the FAA infers that the commenter is pointing out an error in the referenced alert service bulletin and is requesting that all affected airplanes be inspected at the later of the times specified in paragraphs (a)(2)(i) and (a)(2)(ii) of the proposed AD. The FAA concurs. Because the instructions forthe subject overhaul are not available, the FAA has extended the compliance time for those affected airplanes to coincide with the compliance time for all other affected airplanes. The FAA has revised the final rule accordingly. \n\nRequest to Delete NOTE 2 \n\n\tOne commenter requests that FAA delete NOTE 2 of the notice of proposed rulemaking (NPRM). The commenter points out that NOTE 2 removes the operator's "equivalent procedure" allowance specified in Boeing Alert Service Bulletin 747-54A2187. The commenter states that most airlines have FAA-approved procedures that are part of the maintenance program. These procedures are developed because each manufacturer has a slightly different procedure for commonly used processes. If operators are forced to use each manufacturer's specific procedure (i.e., Boeing 747 Airplane Maintenance Manual), as specified in NOTE 2, an undue burden would be placed on the operators. In addition, the FAA's Seattle Aircraft Certification Office (ACO)would receive numerous requests for approval of an alternative method of compliance (AMOC), which could delay implementation of the AD and significantly affect operators' ability to respond to AD's that have short compliance times. \n\n\tThe FAA concurs with the commenter's request to delete NOTE 2 of the NPRM. The FAA has reconsidered its position, as was stated under the heading "Differences Between Proposed Rule and Alert Service Bulletin." The FAA has determined that procedures "equivalent" to those procedures specified in the referenced alert service bulletin for removing or replacing the upper link that are employed by an operator will adequately address the identified unsafe condition and provide an acceptable level of safety. The FAA finds that, if an operator is required to remove or replace the upper link, those corrective actions may be accomplished in accordance with either the applicable chapter of the Boeing 747 Airplane Maintenance Manual (AMM) or an operator's "equivalent procedure," when specified in the referenced alert service bulletin. Therefore, the FAA has removed NOTE 2 of the NPRM from the final rule. \n\nRequest to Clarify the Term "Certain Corrective Actions" \n\n\tOne commenter requests that the FAA clarify whether the term "certain corrective actions," as described under the heading "Differences Between Proposed Rule and Alert Service Bulletin" in the proposed AD, applies to repairs as well as removal and installation. The commenter states that the referenced alert service bulletin specifies that an operator's "equivalent procedure" may be used for removal or installation of the upper links and does not specify that an operator's "equivalent procedure" may be used for repairs of the upper links. In addition, the commenter points out that NOTE 2 of the NPRM states ". . . and Boeing Alert Service Bulletin 747-54A2187, dated May 22, 1997, specifies that corrective actions may be accomplished in accordance with an operator's 'equivalentprocedure.'"\n \n\tThe FAA finds that clarification is necessary. The term "certain" in that paragraph refers to some of the required corrective actions. The operator's "equivalent procedure" does not apply to the inspection specified in Figure 2 or the repair specified in Figure 3 of the alert service bulletin. The alert service bulletin specifies that "certain" corrective actions (i.e., removing, installing, and replacing the upper link) may be accomplished in accordance with an operator's "equivalent procedure." Therefore, the FAA finds that the term "certain" is correct in that paragraph. The FAA acknowledges that NOTE 2 of NPRM incorrectly reads "corrective actions," rather than "certain corrective actions." However, as discussed previously, NOTE 2 is not restated in the final rule, thus, no change to the final rule is necessary. \n\nConclusion \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 with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \nCost Impact \n\n\tThere are approximately 567 Boeing Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 173 airplanes of U.S. registry will be affected by this AD, that it will take approximately 12 work hours per airplane to accomplish the required inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $124,560, or $720 per airplane, per inspection cycle. \n\n\tThe cost impact figure discussed above is 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\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\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 (44 FR 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\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\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\t1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: