AD 94-16-03 ACTIVE

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 767 series airplanes, that currently requires inspections, adjustments, and functional tests of the thrust reverser system. This amendment adds a requirement for installation of an additional thrust reverser system locking feature, periodic functional tests of that locking feature following its installation, and repair of any discrepancy found. This amendment is prompted by the identification of a modification that ensures that the level of safety inherent in the original type design of the thrust reverser system is further enhanced. The actions specified by this AD are intended to prevent possible discrepancies in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight.

Final rule

94-16-03 BOEING: Amendment 39-8993. Docket 93-NM-178-AD. Supersedes AD 92-03-03, Amendment 39-8157. \n\n\tApplicability: Model 767 series airplanes equipped with Pratt & Whitney JT9D-7R4 or General Electric CF6-80A series engines, certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo ensure the integrity of the fail safe features of the thrust reverser system, accomplish the following: RESTATEMENT OF ACTIONS REQUIRED BY AD 92-03-03: \n\n\t(a)\tFor airplanes equipped with Pratt & Whitney JT9D-7R4 series engines: Within 60 days after January 27, 1992 (the effective date of AD 92-03-03, amendment 39-8157), and thereafter at intervals not to exceed 3,000 flight hours, perform the tests, inspections, and adjustments described in Boeing Service Bulletin 767-78-0054, dated December 13, 1991. \n\n\t\t(1)\tFollowing any maintenance action that could affect the thrust reverser system: Repeat the tests, inspections, and adjustments required by paragraph (a) of this AD on the affected engine, prior to further flight, in accordance with the service bulletin. \n\n\t\t(2)\tThereafter, following any maintenance action, continue to perform the repetitive tests, inspections, and adjustments required by paragraph (a) of this AD on the affected engine at intervals not to exceed 3,000 flight hours. \n\n\t(b)\tFor airplanes equipped with General Electric CF6-80A series engines: Within 60 days after January 27, 1992 (the effective date of AD 92-03-03, amendment 39-8157), and thereafter at intervals not to exceed 3,000 flight hours, perform the tests, inspections, and adjustments described in Boeing Service Bulletin 767-78-0053, dated December 13, 1991. \n\n\t\t(1)\tFollowing any maintenance action that could affect the thrust reverser system, repeat the tests, inspections, and adjustments required by paragraph (b) of this AD on the affected engine, prior to further flight, in accordance with the service bulletin. \n\n\t\t(2)\tThereafter, following any maintenance action, continue to perform the repetitive tests, inspections, and adjustments required by paragraph (b) of this AD on the affected engine at intervals not to exceed 3,000 flight hours. \n\n\t(c)\tIf any test, inspection, and/or adjustment required by paragraph (a) or (b) of this AD cannot be successfully performed, or if any test, inspection, and/or adjustment results in findings that are unacceptable in accordance with Boeing Service Bulletin 767-78-0054, dated December 13, 1991, or Boeing Service Bulletin 767-78-0053, dated December 13, 1991, as applicable, accomplish paragraphs (c)(1) and (c)(2) of this AD. \n\n\t\t(1)\tPrior to further flight, deactivate the associated thrust reverser in accordance with Section 78-31-1 of Boeing Document D630T002, "Boeing 767 Dispatch Deviation Guide," Revision 9, dated May 1, 1991. No more than one thrust reverser on any airplane may be deactivated under the provisions of this paragraph. \n\n\t\t(2)\tWithin 10 days after deactivation of any thrust reverser in accordance with this paragraph, the thrust reverser must be repaired in accordance with Boeing Service Bulletin 767-78-0054, dated December 13, 1991, or Boeing Service Bulletin 767-78-0053, dated December 13, 1991, as applicable; the tests and/or inspections required by paragraph (a) or (b) of this AD must be successfully accomplished; and the thrust reverser must then be reactivated.\n\n NEW ACTIONS REQUIRED BY THIS AD: \n\n\t(d)\tWithin 5 years after the effective date of this AD, install an additional thrust reverser system locking feature (synch-lock installation) in accordance with Boeing Service Bulletin 767-78-0060, Revision 2, dated August 19, 1993 (for Model 767 series airplanes equipped with General Electric CF6-80A series engines), or Boeing Service Bulletin 767-78-0061, Revision 1, dated August 5, 1993 (for Model 767 series airplanes equipped with Pratt & Whitney JT9D-7R4 series engines), as applicable. Installation of the additional thrust reverser system locking feature, as required by this paragraph, constitutes terminating action for the requirements of paragraphs (a) through (c) of this AD. \n\n\t(e)\tWithin 4,000 hours time-in-service after installing the synch-lock required by paragraph (d) of this AD (either in production or by retrofit), or within 4,000 hours time-in-service after the effective date of this AD, whichever occurs later; and thereafter at intervals not to exceed 4,000 hours time-in-service: Perform functional tests of the synch-lock in accordance with the "Thrust Reverser Synch-Lock Test" procedures specified below. If any discrepancy is found during any test, prior to further flight, correct it in accordance with procedures described in the Boeing 767 Maintenance Manual. The airplane may be operated in accordance with the provisions and limitations specified in the FAA-approved Master Minimum Equipment List (MMEL), provided that no more than one thrust reverser on an airplane is inoperative and thatno synch-lock on that airplane is in an unlocked position. \n\n\t\t\tTHRUST REVERSER SYNCH-LOCK TEST\n 1.\tGeneral \n\tA.\tThere are two thrust reverser synch-locks on each engine. The thrust reverser synch- locks are installed on the lower non-locking hydraulic actuator of each thrust reverser sleeve. \n\tB.\tThis task has two parts that must be accomplished: \n\t\t(1)\tThe first part does a test of the electrical circuit which controls the \n\t\t\toperation of each thrust reverser synch-lock. \n\t\t(2)\tThe second part does a test of the mechanical condition of each \t\t\t\tthrust reverser synch-lock. \n\tC.\tThe thrust reverser synch-lock is referred to as the "synch-lock" in this \t\t\tprocedure.\n 2.\tThrust Reverser Synch-Lock Integrity Test \n\tA.\tEquipment \n\t\t(1)\tMulti-meter, Simpson 260 or equivalent - commercially available. \n\tB.\tPrepare to do the integrity test for the synch-locks. \n\t\t(1)\tSupply electrical power. \n\t\t(2)\tFor the left engine, make sure these circuit breakers on the overhead \t\t\tcircuit breaker panel, P11, are closed: \n\t\t\t(a)\tL ENG T/R CONT \n\t\t\t(b)\tL ENG T/R IND \n\t\t\t(c)\tL ENG T/R SSL CONT \n\t\t(3)\tFor the right engine, make sure these circuit breakers on the overhead \t\t\tcircuit breaker panel, P11, are closed: \n\t\t\t(a)\tR ENG T/R CONT \n\t\t\t(b)\tR ENG T/R IND \n\t\t\t(c)\tR ENG T/R SSL CONT \n\t\t\t(d)\tAIRPLANES WITH HYDRAULIC MOTOR-DRIVEN \n\t\t\t\tGENERATORS (ETOPS): R ENG T/R CONT ALTN \n\t\t\t(e)\tAIRPLANES WITH HYDRAULIC MOTOR-DRIVEN \t\t\t\t\tGENERATORS (ETOPS): R ENG T/R IND ALTN \n\t\t(4)\tOpen the fan cowl panels. \n\tC.\tDo the electrical test for the synch-locks. \n\t\t(1)\tDo these steps to make sure there are no "hot" short circuits in the electrical system which can accidentally supply power to the synch-locks: \n\t\t\t(a)\tRemove the applicable L(R) electrical connectors, D20194(D20196), from the L(R) synch-locks, V170(V171). \nNOTE: You can find the synch-locks attached to the lower non-locking hydraulic actuators on the applicable thrust reverser sleeves. \n\t\t\t(b)\tUse a multi-meter on the plug end of the applicable electrical connector to make sure that these conditions are correct: \n\n\n\nFROM EQUIPMENT\nTO EQUIPMENT\nCONDITION \nD20194 PIN 1\nD20194 PIN 2\n-3 TO +1 VDC AND CONTINUITY \n(LESS THAN 5OHMS) \nD20196 PIN 1\nD20196 PIN 2\n-3 TO +1 VDC AND CONTINUITY \n(LESS THAN 5 OHMS) \n\n\t\t\t(c)\tIf you did not find these conditions to be correct, you must do \t\t\t\tthese steps: \n\t\t\t\t1)\tMake a careful visual inspection of all the electrical \t\t\t\t\twires and connectors between the synch-lock and its \t\t\t\t\tapplicable power circuit breaker. \n\t\t\t\t2)\tRepair all the unserviceable electrical wire and \t\t\t\t\t\tconnectors that you find. \n\t\t\t\t3)\tUse the multi-meter again to make sure there are no \t\t\t\t\t"hot" short circuits in the electrical system which can \t\t\t\t\taccidentally supply power to the synch-locks. \n\t\t\t(d)\tIf you find the correct conditions when you use the multi-meter, continue on and do the mechanical test of the synch-locks. NOTE: Make sure the circuit breakers shown above continue to be set to the closed position. Do not install the electrical connectors on the synch-locks at this time. \n\tD.\tDo the mechanical test for the synch-locks. \n\t\t(1)\tSupply hydraulic power. \n\n\t\t\tWARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE \n\t\t\tCLEAR OF THE AREA BEHIND EACH THRUST REVERSER. IF \t\t\tYOU DO NOT OBEY THIS INSTRUCTION, INJURIES TO PERSONS \t\t\tOR DAMAGE TO EQUIPMENT CAN OCCUR IF THE \t\t\t\t\tSYNCH-LOCKS DO NOT OPERATE CORRECTLY AND THE \t\t\t\tTHRUST REVERSER EXTENDS. \n\n\t\t(2)\tMove the reverse thrust levers for the two engines to try to extend the thrust reversers with hydraulic power. \n\nNOTE: If the thrust reversers do not extend, the synch-locks are serviceable. If the thrust reversers extend, the applicable synch-locks did not operate correctly. \n\n\t\t(3)\tReplace the applicable synch-locks on the thrust reverser that extended when you moved the reverse thrust levers. \n\t\t(4)\tMake sure the reverse thrust levers are in the fully stowed position. \n\t\t(5)Install the applicable L(R) electrical connectors, D20194(D20196), on \t\t\tthe L(R) synch-locks, V170(V171). \n\n\t\t\tWARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE \n\t\t\tCLEAR OF THE AREA BEHIND THE THRUST REVERSERS. IF \t\t\tYOU DO NOT OBEY THIS INSTRUCTION, INJURIES TO PERSONS \t\t\tOR DAMAGE TO EQUIPMENT CAN OCCUR WHEN THE THRUST \n\t\t\tREVERSERS ARE EXTENDED. \n\n\t\t(6)\tMove the reverser thrust levers for the two engines to extend the thrust reversers with hydraulic power. \n\nNOTE: If the thrust reversers extend, the synch-locks are serviceable. If the thrust reversers do not extend, the applicable synch-locks did not operate correctly. \n\n\t\t(7)\tReplace the applicable synch-locks on the thrust reverser that did not \t\t\textend when you moved the reverse thrust levers. \n\tE.\tPut the airplane back to its usual condition. \n\t\t(1)\tMove the reverse thrust levers to fully retract the thrust reversers on \t\t\tthe two engines with hydraulic power. \n\t\t(2)\tRemove the hydraulic power if it is not necessary. \n\t\t(3)\tRemove the electrical power if it is not necessary. \n\t\t(4)\tClose the fan cowl panels. \n\t(f)\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. \t\n\n\tNOTE: 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(g)\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\t(h)\tThe installation shall be done in accordance with Boeing Service Bulletin767-78- 0060, Revision 2, dated August 19, 1993; and Boeing Service Bulletin 767-78-0061, Revision 1, dated August 5, 1993; as applicable. 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. Certain other actions shall be done in accordance with Boeing Service Bulletin 767-78-0054, dated December 13, 1991; and Boeing Service Bulletin 767-78-0053, dated December 13, 1991; as applicable. The incorporation by reference of these documents 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 January 27, 1992 (57 FR 3004, January 27, 1992). 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(i)\tThis amendment becomes effective on September 12, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 92-03-03, amendment 39-8157 (57 FR 3004, January 27, 1992), which is applicable to certain Boeing Model 767 series airplanes, was published in the Federal Register on February 2, 1994 (59 FR 4870). The action proposed to require inspections, adjustments, and functional tests of the thrust reverser system; installation of an additional thrust reverser system locking feature; periodic functional tests of that locking feature following its installation; and repair of any discrepancy found. \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\n\tOne commenter supports the proposed rule. \n\n\tThe Air Transport Association (ATA) of America, on behalf of its members, requests that a note or provision be added to the proposal to indicate that relief provided by the Master Minimum Equipment List (MMEL) is not revoked by the adoption of this AD. The commenter states that deactivation of a thrust reverser is not considered to be an unsafe procedure and is, therefore, not the subject of the proposed rule. \n\n\tThe FAA concurs. The FAA agrees that certain relief may be provided to operators as requested by the commenter, and finds that the airplane may be operated in accordance with the provisions and limitations specified in the FAA-approved MMEL, provided that no more than one thrust reverser on an airplane is inoperative and that no synch-lock on that airplane is in an unlocked position. The FAA has revised paragraph (e) of the final rule accordingly. \n\n\tThe ATA also questions the requirement contained in paragraph (e) of the proposal for repetitive functional tests of the synch-lock installation. The ATA states that its members are not opposed to accomplishing the proposed tests as part of their maintenance programs, but are opposed to accomplishing the tests as part of the requirements of an AD. The ATA reasons that the "intent" of the proposed rule is to terminate the tests required by AD 92-03-03. \n\n\tThe ATA questions the rationale for the proposed repetitive functional tests of the synch- lock installation, since the synch-lock configuration has not been shown to be unsafe. The ATA acknowledges the FAA's statement in the Discussion section of the proposal that the synch-lock is a new design whose reliability has not been adequately proven through service experience. The ATA states that, under this rationale, an operator's maintenance program for newly certificated airplanes would simply consist of Certification Maintenance Requirement (CMR) items, since the reliability of newly designed systems has not been adequately proven through service experience. The ATA believes that AD control of the proposed repetitive tests is justified only if it can be shown that the tests cannot be administered safely within an operator's maintenance program. \n\n\tThe ATA acknowledges that without issuance of an AD, the proposed repetitive tests may not be incorporated into every operator's maintenance program in a common manner at common intervals. In light of this consideration, the ATA requests that an alternative to accomplishment of the repetitive tests be provided in the final rule. The suggested alternative for paragraph (e) of the AD follows: Within 3 months after accomplishing the synch-lock installation, revise the FAA- approved maintenance inspection program to include a functional test of the synch-lock. The initial test would be accomplished within 1,500 hours time-in-service after modification. The AD would no longer be applicable to operators that have acceptably revised their maintenance programs. Operators choosing this alternative could use an alternative recordkeeping method in lieu of that required by section 91.417 or 121.380 of the Federal Aviation Regulation (14 CFR 91.417or 121.380). The FAA would be defined as the cognizant Principal Maintenance Inspector (PMI) for operators electing this alternative. \n\n\tThe ATA believes that its proposal should be adopted because the proposed repetitive tests will likely continue for as long as Model 767 series airplanes are operated. The ATA adds that, while there are numerous AD's that require repetitive inspections that would continue for the life of the aircraft, in such cases, either a satisfactory terminating action has not been developed or service experience has shown that control of the inspections cannot be safely administered through an operator's maintenance program. The ATA's proposal is intended to minimize the impact of the AD process on an operator's maintenance program. \n\n\tThe FAA recognizes the concerns of the commenter regarding the requirement for periodic functional tests of the synch-lock following its installation, as required by paragraph (e) of this AD. However, the FAA has determinedthat such tests are necessary in order to provide an adequate level of safety and to ensure the integrity of the synch-lock installation. The actions required by this AD are consistent with actions that have been identified by an industry-wide task force as necessary to ensure adequate safety of certain thrust reverser systems installed on transport category airplanes. Representatives of the Aerospace Industries Association (AIA) of America, Inc., and the FAA comprise that task force. Representatives from other organizations, such as the ATA, have participated in various discussions and work activities resulting from the recommendations of the task force. \n\n\tThe FAA acknowledges that the functional tests specified in paragraph (e) of this AD and CMR items are similar in terms of scheduled maintenance and recordkeeping. However, this AD addresses an unsafe condition and requires installation of the synch-lock to correct that unsafe condition. The FAA has determined that the requirement for functional tests is necessary in order to ensure the effectiveness of that installation in addressing that unsafe condition. As discussed in the preamble of the proposal, this determination is based on the fact that the synch-lock is a new design whose reliability has not been adequately proven through service experience. In addition, service experience to date has demonstrated that failures can occur within the synch- lock that may not be evident during normal operation of the thrust reverser system and may not result in activation of the synch-lock "unlock" indicator. The FAA notes that the ATA's suggested alternative to accomplishment of the functional tests would permit each operator to determine whether and how often these tests should be conducted. In light of the severity of the unsafe condition, however, the FAA has determined that allowing this degree of operator discretion is not appropriate at this time. Therefore, this AD is necessary to ensure that operators accomplish tests of the integrity of the synch-lock installation in a common manner and at common intervals. \n\n\tThe ATA also requests that the proposed interval of 1,000 hours time-in-service for accomplishment of the repetitive functional tests specified in paragraph (e) of the proposal be extended to 1,500 hours time-in-service. The ATA explains that Boeing has recommended an interval of 4,000 hours time-in-service for inclusion in the next Maintenance Review Board (MRB) report. If the FAA denies an extension of the proposed interval, the ATA requests that the FAA explain why its analysis is so stringent in comparison with Boeing's recommendation. The ATA believes that AD compliance times should be consistent with operators' regularly scheduled maintenance unless a risk analysis requires otherwise. The ATA reasons that compliance times that are inconsistent with scheduled maintenance holds force operators to reschedule maintenance actions at considerable expense and disruption to their operations. \n\n\tThe FAA has reconsidered the proposed interval of 1,000 hours time-in-service for accomplishment of the initial and repetitive functional tests required by paragraph (e) of this AD. The FAA recognizes that an initial and repetitive interval of 4,000 hours time-in-service for accomplishment of these functional tests, as recommended by Boeing, corresponds more closely to the interval at which most of the affected operators conduct regularly scheduled "C" checks. In light of the safety implications of the addressed unsafe condition and the practical aspects of accomplishing orderly functional tests of the fleet during regularly scheduled maintenance where special equipment and trained maintenance personnel will be readily available, the FAA finds that accomplishment of the tests at intervals of 4,000 hours time-in-service will provide an acceptable level of safety. Paragraph (e) of the final rule has been revised accordingly. \n\n\tThe ATA also requests thatthe cost of parts be included in the economic impact information, below, in order to present a total cost impact of the rule on the "U.S. public." The ATA recognizes that Boeing plans to supply parts at no cost to operators; however, the ATA suspects the parts costs borne by Boeing would be substantial. The FAA does not concur with the commenter's request. The total cost impact figures shown in the economic impact information, below, represent the costs for time necessary to perform the inspections, adjustments, tests, and modification required by this AD. The cost analysis in AD rulemaking actions typically does not include parts costs when those parts are provided by the manufacturer at no cost to operators. Such costs are not attributable to the AD; the manufacturer would incur these costs even if no AD were issued. \n\n\tThe FAA has revised paragraph (d) of the final rule to specify that the correct reference for Boeing Service Bulletin 767-78-0061 is Revision 1, rather than Revision 2, as cited in the proposal. The issue date of Revision 1 (August 5, 1993) appeared correctly in the proposed rule. \n\n\tThe FAA also has revised paragraphs (a) and (b) of the final rule to clarify the appropriate compliance time. Those paragraphs restate requirements for accomplishment of certain actions required by AD 92-03-03. The FAA's intent is that the tests, inspections, and adjustments required by those paragraphs would have been accomplished within 60 days after January 27, 1992 (the effective date of AD 92-03-03). \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. \n\n\tThere are approximately 119 Model 767 series airplanes equipped with General Electric CF6-80A seriesengines of the affected design in the worldwide fleet. The FAA estimates that 69 airplanes of U.S. registry will be affected by this AD. The inspections, adjustments, and functional tests required currently by AD 92-03-03 require approximately 16 work hours per airplane to accomplish the required actions, at an average labor rate of $55 per work hour. Based on these figures, the total cost impact of those actions on U.S. operators of Model 767 series airplanes equipped with General Electric CF6-80A series engines is estimated to be $60,720, or $880 per airplane. \n\n\tFor U.S. operators of Model 767 series airplanes equipped with General Electric CF6-80A series engines, the FAA estimates that it will take approximately 786 work hours per airplane to accomplish the modification required by this AD, and 1 work hour to accomplish the required functional tests, at an average labor rate of $55 per work hour. Required parts will be supplied by the manufacturer at no cost to operators. Based on these figures, the total cost impact of those actions on U.S. operators of Model 767 series airplanes equipped with General Electric CF6-80A series engines is estimated to be $2,986,665, or $43,285 per airplane. \n\n\tThere are approximately 95 Model 767 series airplanes equipped with Pratt & Whitney JT9D-7R4 series engines of the affected design in the worldwide fleet. The FAA estimates that 30 airplanes of U.S. registry will be affected by this AD. The inspections, adjustments, and functional tests required currently by AD 92-03-03 require approximately 16 work hours per airplane to accomplish the required actions, at an average labor rate of $55 per work hour. Based on these figures, the total cost impact of those actions on U.S. operators of Model 767 series airplanes equipped with Pratt & Whitney JT9D-7R4 series engines is estimated to be $26,400, or $880 per airplane. \n\n\tFor U.S. operators of Model 767 series airplanes equipped with Pratt & Whitney JT9D-7R4 series engines, the FAA estimates that it will take approximately 812 work hours per airplane to accomplish the modification required by this AD, and 1 work hour to accomplish the required functional tests, at an average labor rate of $55 per work hour. Required parts will be supplied by the manufacturer at no cost to operators. Based on these figures, the total cost impact of those actions on U.S. operators of Model 767 series airplanes equipped with Pratt & Whitney JT9D-7R4 series engines is estimated to be $1,341,450, or $44,715 per airplane. \n\n\tThe total 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\n\tThe number of required work hours for accomplishing the required functional tests, as indicated above, is presented as if the accomplishment of those tests required by this AD were to be conducted as "stand alone" actions. However, in actual practice, those tests for the most part will be accomplished coincidentally or in combination with normally scheduled airplane inspections and other maintenance program tasks. Therefore, the actual number of necessary additional work hours for accomplishment of the functional tests will be minimal in many instances. Additionally, any costs associated with special airplane scheduling will be minimal. \n\n\tThe FAA recognizes that the required modification will require a large number of work hours to accomplish. However, the 5-year compliance time specified in paragraph (d) of this AD should allow ample time for the synch-lock installation to be accomplished coincidentally with scheduled major airplane inspection and maintenance activities, thereby minimizing the costs associated with special airplane scheduling. \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\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.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n\t2.\tSection 39.13 is amended by removing amendment 39-8157 (57 FR 3004, January 27, 1992), and by adding a new airworthiness directive (AD), amendment 39-8993, to read as follows:

The service information referenced in this AD may be obtained from Boeing\nCommercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Richard Simonson, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2683; fax (206) 227-1181.