AD 96-14-06

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 777-200 series airplanes. This action requires repetitive inspections for broken lockwires on the bearing retainer nut of the pivot fittings of the horizontal stabilizer. This AD also requires eventual modification of the bearing nut retention means, which, when accomplished, terminates the repetitive inspections. This amendment is prompted by reports of broken lockwires on the bearing retainer nut of the pivot fittings of the horizontal stabilizer due to inadequate torquing of the nut. The actions specified in this AD are intended to prevent failure of the lockwires, which could result in loosening of the retainer nut for the pivot bearing of the horizontal stabilizer, and subsequent migration of the pivot bearing. This condition, if not corrected, could result in reduced controllability of the airplane.

Final rule; request for comments

96-14-06 BOEING: Amendment 39-9688. Docket 96-NM-134-AD. \n\n\tApplicability: Model 777-200 series airplanes; line positions 1, 3, 5, 7, 8, 9, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, and 23; 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 (b) 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 reduced controllability of the airplane due to failure of the lockwire on the bearing retainer nut of the pivot fittings of the horizontal stabilizer, loosening of the retainer nut for the pivot bearing, and subsequent migration of the pivot bearing, accomplish the following: \n\n\t(a)\tWithin 150 flight cycles after the effective date of this AD: Perform a visual inspection for broken lockwires on the bearing retainer nut of the pivot fittings of the horizontal stabilizer (left and right sides), in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 777-55A0003, Revision 1, dated June 20, 1996. \n\n\t\t(1)\tIf no broken lockwire is found: Repeat the inspection within 500 flight cycles following accomplishment of the initial inspection. Within 1,000 flight cycles after accomplishment of the initial inspection, modify the bearing nut retention means in accordance with Figure 3 of the alert servicebulletin. Following accomplishment of the modification, no further action is required by paragraph (a) of this AD. \n\n\t\t(2)\tIf only one broken lockwire is found: Repeat the inspection thereafter at intervals not to exceed 150 flight cycles. Within 450 flight cycles after accomplishment of the initial inspection, modify the bearing nut retention means in accordance with Figure 3 of the alert service bulletin. Following accomplishment of the modification, no further action is required by paragraph (a) of this AD. \n\n\t\t(3)\tIf two broken lockwires are found: Repeat the inspection and ensure that the bearing retainer nut is tight thereafter at intervals not to exceed 10 flight cycles. Within 100 flight cycles after accomplishment of the initial inspection, modify the bearing nut retention means in accordance with Figure 3 of the alert service bulletin. Following accomplishment of the modification, no further action is required by paragraph (a) of this AD. \n\n\t(b)\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(c)\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(d)\tThe actions shall be done in accordance with Boeing Alert Service Bulletin 777-55A0003, Revision 1, dated June 20, 1996. This incorporation by reference was approved by the Director of the FederalRegister 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(e)\tThis amendment becomes effective on July 24, 1996.

The FAA has received reports indicating that broken lockwires were found on the bearing retainer nut of the pivot fittings (bearings) of the horizontal stabilizer on Boeing Model 777-200 series airplanes. In one of these incidents, the retainer nut on the left and right sides of the horizontal stabilizer also was loose. The lockwires may have broken and the retainer nuts may have become loose due to inadequate torquing of the nut. Failure of the lockwire could result in loosening of the retainer nut for the pivot bearing of the horizontal stabilizer. Loss of the retainer nut could result in migration of the pivot bearing. This condition, if not corrected, could result in reduced controllability of the airplane. \n\nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 777-55A0003, Revision 1, dated June 20, 1996, which describes procedures for repetitive visual inspections to detect broken lockwires on the bearing retainer nut of the pivot fittings of the horizontal stabilizer (left and right sides). The alert service bulletin also describes procedures for eventual modification of the bearing nut retention means, which, when accomplished, eliminates the need for the repetitive inspections. The modification involves removing all lockwire on the nut, tightening the nut, and installing a new nut retainer. Accomplishment of the modification will prevent rotation of the bearing retainer nut.\n\n Explanation of the Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Model 777-200 series airplanes of the same type design, this AD is being issued to prevent reduced controllability of the airplane due to failure of the lockwire on the bearing retainer nut of the pivot fittings of the horizontal stabilizer, loosening of the retainer nut for the pivot bearing, and subsequent migration of the pivot bearing. This ADrequires repetitive visual inspections for broken lockwires on the bearing retainer nut of the pivot fittings of the horizontal stabilizer (left and right sides). This AD also requires eventual modification of the bearing nut retention means, which, when accomplished, terminates the repetitive inspections. The actions are required to be accomplished in accordance with the alert service bulletin described previously. \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\n Comments 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 invitedto 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 thesubstance 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 96-NM-134-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 isnot 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. \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: 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: