AD 97-17-02

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 777-200 series airplanes. This action requires repetitive torquing of the bushing retainer nuts of the pivot pins in the horizontal stabilizer hinge assembly to tighten loose nuts to the new torque value; and repetitive visual inspections, if necessary, to detect bushing migration or damage to adjacent structures, and repair of any damage. This proposal also provides for an optional terminating action for the repetitive inspections. This amendment is prompted by a report of a loose bushing retainer nut, which may be attributed to low nut torque. The actions specified in this AD are intended to detect and correct loose bushing retainer nuts of the pivot pins in the horizontal stabilizer hinge assembly, which could result in bushing migration and consequent damage to the adjacent structure, and reduced controllability of the airplane.

Final rule; request for comments.

97-17-02 BOEING: Amendment 39-10104. Docket 97-NM-124-AD. \n\n\tApplicability: Model 777-200 series airplanes, line numbers 3, 5, 7 through 9 inclusive, 11 through 13 inclusive, 15 through 17 inclusive, and 19 through 22 inclusive; 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 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 (d) 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 actionsto address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo detect and correct loose bushing retainer nuts of the pivot pins in the horizontal stabilizer hinge assembly, which could result in bushing migration and consequent damage to the adjacent structure, and reduced controllability of the airplane, accomplish the following: \n\n\t(a)\tWithin 150 flight cycles after the effective date of this AD, torque the bushing retainer nuts to the new torque value of 1,000 to 1,500 in-lbs, in accordance with Figure 2 of the Boeing Service Bulletin 777-53-0006, dated May 8, 1997. Repeat the torquing thereafter at intervals not to exceed 1,000 flight cycles. \n\n\tNOTE 2: Where there are differences between the AD and the service bulletin, the AD prevails. \n\n\t(b)\tIf any bushing retainer nut is loose and is not correctly attached to the bushing, prior to further flight, perform a visual inspection to determine whether bushing migration has occurred, in accordance with Figure 2 of the Boeing Service Bulletin 777-53-0006, dated May 8, 1997. \n\n\t\t(1)\tIf bushing migration has not occurred, prior to further flight, tighten the bushing retainer nuts in accordance with Figure 2 of the service bulletin. Repeat the visual inspection thereafter at intervals not to exceed 1,000 flight cycles. \n\n\t\t(2)\tIf bushing migration has occurred, prior to further flight, inspect/replace the bushing and other affected components and repair any damage, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(c)\tAccomplishment of installing an anti-rotation bracket in accordance with Figure 3 of Boeing Service Bulletin 777-53-0006, dated May 8, 1997, constitutes terminating action for the repetitive inspection requirements of this AD. \n\n\t(d)\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 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. \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(e)\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(f)\tCertain actions shall be done in accordance with Boeing Service Bulletin 777-53-006, dated May 8, 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(g)\tThis amendment becomes effective on September 4, 1997.

Boeing recently notified the FAA that an unsafe condition may exist on certain Boeing Model 777-200 series airplanes. Investigation revealed that a loose bushing retainer nut of the pivot pin in the horizontal stabilizer hinge assembly was found on a Boeing Model 777-200 flight test airplane that had accumulated approximately 2,000 total flight cycles. The cause of the loose bushing retainer nut may be attributed to low nut torque. A loose bushing retainer nut of the pivot pin in the horizontal stabilizer hinge assembly, if not corrected, could result in bushing migration and consequent damage to the adjacent structure, and reduced controllability of the airplane. \n\nExplanation of Relevant Service Information \n\n\tBoeing has issued Service Bulletin 777-53-0006, dated May 8, 1997, which describes procedures for repetitive inspections of the bushing retainer nuts of the pivot pins in the horizontal stabilizer hinge assembly to detect and correct loose bushing retainer nuts, migration of the bushings, or damage to adjacent structures. This service bulletin also describes optional procedures for tightening the bushing retainer nuts to a torque level of 1,000 to 1,500 in-lbs. In addition, this service bulletin describes procedures for tightening the bushing retainer nuts and installing anti-rotation brackets to prevent the nuts from rotating, which would eliminate the need for repetitive inspections.\n\nExplanation of the Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Boeing Model 777-200 series airplanes of the same type design, this AD is being issued to detect and correct loose bushing retainer nuts of the pivot pins in the horizontal stabilizer hinge assembly, which could result in bushing migration and consequent damage to the adjacent structure, and reduced controllability of the airplane. This action requires repetitive torquing of the bushing retainer nuts of the pivot pins in the horizontal stabilizer hinge assembly to tighten loose nuts to the new torque value of 1,000 to 1,500 in-lbs; and repetitive visual inspections, if necessary, to detect bushing migration or damage to adjacent structures. This proposal also provides for an optional action of installing brackets to prevent rotation of the bushing retainer nuts, which would constitute termination for the repetitive inspections. These actions are required to be accomplished in accordance with the service bulletin described previously. \n\nDifferences Between the AD and the Relevant Service Information \n\n\tOperators should note that, although Boeing Service Bulletin 777-53-0006 provides procedures to eliminate the need for repetitive inspections after accomplishment of a third inspection (2,150 flight cycles), this AD requires repetitive inspections at intervals not to exceed 1,000 flight cycles, until accomplishment of the terminating action. In developing an appropriate compliance time for this AD, the FAA has determined that the repetitive inspections should not be extended to a third inspection (2,150 flight cycles) and that, in order to provide an acceptable level of safety, repetitive intervals should not exceed 1,000 flight cycles. \n\n\tOperators should also note that, although the service bulletin specifies that the manufacturer must be contacted for instructions in the repair of damage, this AD requires the repair to be accomplished in accordance with a method approved by the FAA.\n \nInterim Action \n\n\tThe FAA is considering further rulemaking to supersede this AD to require installing anti- rotation brackets to prevent the nuts from rotating. However, the planned compliance time for accomplishment of this action is sufficiently long so that prior notice and time for public comment will be practicable. \n\nDetermination of Rule's Effective Date \n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found thatnotice 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. Factual information 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-124-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 ofpower 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 and placed 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. \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 U.S.C. 106(g), 40113, 44701. § 39.13 - (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: