[Federal Register Volume 59, Number 205 (Tuesday, October 25, 1994)] [Unknown Section] [Page 0] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 94-25294] [[Page Unknown]] [Federal Register: October 25, 1994] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 93-NM-122-AD; Amendment 39-9047; AD 94-21-05] Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes Equipped With CFM International CFM56-3 Series Engines AGENCY: Federal Aviation Administration, DOT. ACTION: Final rule. ----------------------------------------------------------------------- SUMMARY: This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-300, -400, and -500 series airplanes, that requires modification, adjustments, and tests of the thrust reverser system; and repair, if necessary. This amendment is prompted by results of a safety review of the thrust reverser system on these airplanes, which revealed that the installation of additional features to further minimize the likelihood of an in-flight thrust reverser deployment is necessary. The actions specified by this AD are intended to prevent deployment of a thrust reverser in flight and subsequent reduced controllability of the airplane. DATES: Effective November 25, 1994. - The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of November 25, 1994. ADDRESSES: The service information referenced in this AD may be obtained from Boeing Commercial 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. FOR FURTHER INFORMATION CONTACT: Stephen Bray, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2681; fax (206) 227-1181. SUPPLEMENTARY INFORMATION: 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 737-300, - 400, and -500 series airplanes was published in the Federal Register on October 15, 1993 (58 FR 53457). That action proposed to require modification, adjustments, and tests of the thrust reverser system; and repair, if necessary. - Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. - One commenter supports the proposed rule. - One commenter requests that paragraph (c) of the proposal be revised to specify that the paragraph applies to airplanes identified in the effectivity listing of Boeing Service Bulletin 737-78-1058. The commenter indicates that paragraph (c), as proposed, would require modification of airplanes on which the sync-lock was installed in production, but on which no additional rework was required. Further, as proposed, paragraph (c) would include airplanes that are not listed in the effectivity listing of Boeing Service Bulletin 737-78-1058. The FAA concurs, and has revised paragraph (c) of the final rule accordingly. However, airplanes on which the sync-lock was installed during production continue to be subject to the repetitive integrity test required by paragraph (d) of the final rule. Paragraph (d) of the final rule has been revised to clarify that requirement, and a new paragraph (e) has been included in the final rule to specify the compliance times for accomplishment of that requirement. The Air Transport Association (ATA) of America states that, while its members are not opposed to accomplishing periodic operational tests of the sync-lock following its installation [proposed in paragraph (d) of the AD] as part of their maintenance programs, these members are opposed to accomplishing the tests as part of the requirements of an AD. The ATA members believe that the requirement for operational tests is equivalent to issuing a Certification Maintenance Requirements (CMR) item by means of an AD. - ATA adds that, if the FAA finds sufficient justification to include the requirement for operational tests in the AD, an alternative to accomplishment of the tests should be provided in the final rule. ATA reasons that an alternative is justified because no data exist to show that repetitive tests of a modified thrust reverser cannot be handled adequately through an operator's maintenance program. The suggested alternative follows: Within 3 months after accomplishing the sync-lock installation, revise the FAA-approved maintenance inspection program to include an operational test of the sync-lock. The initial test would be accomplished within 1,000 hours time-in-service after modification. The AD would no longer be applicable for operators that have acceptably revised the maintenance program. Operators choosing this alternative could use an alternative recordkeeping method in lieu of that required by Secs. 91.417 or 121.380 of the Federal Aviation Regulations (FAR) (14 CFR 91.417 or 121.380). The FAA would be defined as the cognizant Principal Maintenance Inspector (PMI) for operators electing this alternative. - The FAA recognizes the concerns of the commenter regarding the requirement for periodic operational tests of the sync-lock following its installation. However, the FAA finds that these tests are necessary to provide an adequate level of safety and to ensure the integrity of the sync-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 ATA, have participated in various discussions and work activities resulting from the recommendations of the task force. - The FAA acknowledges that the operational tests specified in this AD and CMR items are similar in terms of scheduled maintenance and recordkeeping. This AD addresses an unsafe condition and requires installation of the sync-lock to correct that unsafe condition. The FAA has determined that the requirement for operational tests is necessary to ensure the effectiveness of that installation in addressing the unsafe condition. This determination is based on the fact that the sync-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 sync-lock that may not be evident during normal operation of the thrust reverser system and may not result in activation of the sync-lock ``unlock'' indicator. The ATA's suggested alternative to accomplishment of the operational 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 sync-lock installation in a common manner and at common intervals. - Two commenters question why the proposed operational tests would be required at more frequent intervals following installation of an additional safety feature than prior to its installation. One of these commenters suggests that Boeing should prove the reliability of the system prior to its operation, and that the operational tests should be required at intervals not to exceed 3,000 hours time-in-service. -Several commenters also suggest that the installation of an additional safety feature, in addition to the fact that no failures of the system have occurred, should allow tests at ``C'' check intervals. Another commenter states that accomplishment of the tests at ``2B'' check intervals (or 1,100 hours time-in-service) would be more appropriate. One of these commenters states that a trial test period of the installation by several airlines would be in order. -The FAA has reconsidered the compliance time specified in paragraph (d) of the proposal [identified in paragraph (e) of the final rule] for accomplishment of an initial operational test, as well as the interval specified for accomplishment of repetitive operational tests. In light of the safety implications of the unsafe condition addressed and the practical aspects of accomplishing orderly operational tests of the fleet during regularly scheduled maintenance where special equipment and trained maintenance personnel will be readily available, the FAA finds that the compliance times specified in paragraph (e) of the AD may be extended without compromising safety. The FAA has determined that an interval of 4,000 hours time-in-service corresponds more closely to the interval at which most of the affected operators conduct regularly scheduled ``C'' checks. Therefore, paragraph (e) of the final rule has been revised to require accomplishment of the initial test within 4,000 hours time-in-service and accomplishment of repetitive tests at intervals not to exceed 4,000 hours time-in- service. -One commenter requests that the FAA review the requirement for periodic operational tests specified in paragraph (d) of the proposal because these tests only address a sync-lock failing in the unlocked state. The commenter states that the sync-lock will be totally transparent to the flight crew. Therefore, if a sync-lock fails in the ``locked'' state, the only indication the flight crew will receive is that when reverse thrust is applied, the reverser handles will be stopped by the interlock system and not allowed to move into reverse thrust. -The FAA considers that the operational tests required by paragraph (d) of this AD are adequate to address both the unlocked state and the locked state. The design of the sync-lock is fail-safe in the locked state; its failure in that state during flight would not result in deployment of a thrust reverser. In addition, failure of a sync-lock in the locked state during landing of the airplane does not present an unsafe condition. The airplane can be stopped within the distance specified in the Airplane Flight Manual (AFM) without the use of thrust reversers. The stopping distance specified in the AFM does not take credit for the additional stopping capabilities of the thrust reverser. -Three commenters request revisions to the compliance times specified in paragraph (a) of the proposal for accomplishment of initial and repetitive adjustments and tests of the thrust reverser system. One of these commenters requests that the proposed 30-day compliance time for the initial adjustments and tests be extended to 60 days to accomplish these actions on all of the airplanes in its fleet. The commenter believes that a compliance time of 60 days is more appropriate in light of the fact that no major thrust reverser anomalies have been found. -Two of these commenters request that the proposed compliance time for accomplishment of the repetitive adjustments and tests specified in paragraph (a) of the proposal be revised to ``3,000 hours time-in- service, or at each `C' check, whichever occurs later.'' One of the commenters believes that the compliance interval specified in the proposal is overly restrictive, and that the suggested revision would allow for accomplishment of testing and repairs at a time that coincides with regularly scheduled maintenance. -The FAA concurs with these commenters' requests to revise the compliance times for the initial and repetitive adjustments and tests required by paragraph (a) of the final rule. The FAA's intent was that these adjustments and tests be conducted during a regularly scheduled maintenance visit for the majority of the affected fleet, when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. In light of this consideration, the FAA has determined that an extension of the compliance time for the initial adjustments and tests to 60 days, and an extension of the repetitive interval to 4,000 hours time-in-service, will not affect safety adversely. Paragraph (a) of the final rule has been revised accordingly. -Several commenters question the references to certain pages of the Boeing 737 Maintenance Manual cited in paragraphs (a) and (d) of the proposal. ATA requests that a statement be added to those paragraphs to allow operators to use later versions of the Maintenance Manual, provided that no substantive change is included in those later versions. One commenter points out that since certain Maintenance Manual pages referenced in the proposal have already been revised, operators must seek approval from the FAA for an alternative method of compliance in order to deviate from the Maintenance Manual pages cited in the AD. One commenter mentions that the Maintenance Manual page numbers cited in paragraph (d) of the proposal do not exist. Two commenters state that the specific Maintenance Manual pages referenced in the proposal include a number of tests that are redundant and unnecessary. One commenter states that the tests specified in paragraph (a) are normally performed after component replacement or after a system error has occurred. The commenter indicates that performing the ``Normal Operation Test'' and the ``Auto-Restow Test,'' in addition to using the thrust reverser during normal flight operations, will satisfy all testing requirements for the thrust reverser. -Boeing requests specifically that the proposal be revised to include copies of the procedures for the required tests so that reference to the Maintenance Manual is not necessary. Boeing explains that the Maintenance Manuals are customized for each operator to reflect all of the equipment in that operator's fleet. Therefore, the number of pages for any given procedure is variable, depending on the number of different equipment configurations documented in an operator's Maintenance Manual. Boeing also indicates that Maintenance Manual procedures are revised periodically for non-technical reasons. Boeing adds that changes to the structure of the procedures are necessary to accommodate an upgrade of the publishing system that is currently under way, which, in addition to repagination, will necessitate the issuance of revised Maintenance Manual pages. -Boeing states that the effect of specifying Maintenance Manual page numbers and revision dates in the AD is that operators may be unable to use the procedure contained in the Maintenance Manual to perform certain tests required by the AD. Each operator would be required to maintain an obsolete version of the procedure, or to request FAA approval of an alternative method of compliance with the AD that would allow the use of the current version of the Maintenance Manual. -The FAA concurs partially. In light of the information submitted by the commenters, the FAA finds that specific reference to page numbers and dates of the Boeing 737 Maintenance Manual should not be specified in paragraph (a) of the final rule. However, for that paragraph, the FAA does not agree that copies of the specific procedures should be included in the final rule. Therefore, paragraph (a) of the final rule has been revised to cite only the appropriate section specified in the Maintenance Manual for accomplishment of the tests required by that paragraph. The procedures specified in that section of the Maintenance Manual contain the appropriate tests recommended by the manufacturer for verification of the proper operation of the thrust reverser system. However, the FAA would consider requests from individual operators for approval of use of alternative test procedures, in accordance with the provisions of paragraph (f) of this AD. -Subsequent to the issuance of the proposal and the receipt of Boeing's comments to the proposal, Boeing has submitted to the FAA separate procedures for accomplishment of the operational tests of the sync-lock integrity following its installation. The FAA has included these procedures in paragraph (d) of the final rule; therefore, the Maintenance Manual references specified in paragraph (d) of the proposal have been removed from the final rule. -One commenter requests that the compliance times be expressed in terms of cycles, instead of operating hours, since degradation of the thrust reverser system is related to cycles. The FAA does not concur. The FAA finds that the simplest expression of compliance times for purposes of this AD is in terms of a specific number of hours of operation at which compliance is required for affected airplanes. The FAA based this determination on the fact that the maintenance program for these airplanes is based on operating hours, the Maintenance Manual specifies compliance in terms of operating hours, and the maintenance program is based on operating hours. Further, recommended compliance intervals reflected in a safety assessment completed for the affected airplane/engine combination were expressed in terms of hours time-in- service. -Two commenters request that the proposed 5-year compliance time for accomplishing the sync-lock installation be revised to 6 years to allow airplanes to be modified during scheduled heavy maintenance visits. The FAA does not concur with the commenters' requests to extend the compliance time. In developing an appropriate compliance time for this action, the FAA considered the safety implications, parts availability, and normal maintenance schedules for timely accomplishment of the modification. In consideration of these items, as well as input from the manufacturer with regard to parts availability, and industry representatives with regard to incorporation schedules, the FAA has determined that 5 years represents the maximum interval of time allowable wherein the modification can reasonably be accomplished and an acceptable level of safety can be maintained. ATA, on behalf of one of its members, requests that paragraphs (a) and (d) of the proposal be revised to provide an option for operators to lock out a thrust reverser that fails the tests required by those paragraphs in order to avoid unnecessary flight delays and cancellations. The commenter states that the Boeing 737 Master Minimum Equipment List (MMEL) presently grants this relief, provided that the thrust reverser in question is properly locked out. The FAA concurs partially. The FAA agrees that an option for dispatch relief should be allowed in accordance with the existing provisions and limitations specified in the MMEL. Paragraph (a) of the final rule has been revised accordingly. However, for airplanes on which a sync-lock is installed, the FAA, in conjunction with the Model 757/767 Thrust Reverser Working Group, finds that a thrust reverser may be locked out, but the sync-lock must be operational at all times in order to ensure safe flight. Paragraph (d) of the final rule has been revised accordingly. The FAA also has revised paragraph (a) of the final rule to specify that only airplanes on which the sync-lock installation, the sync-lock wiring modification, or Production Revision Record (PRR) 35105 has not been accomplished are subject to the requirements of that paragraph. Two commenters suggest that the work hour estimates for accomplishment of the adjustments and tests [specified in paragraph (a) of the proposal] and operational tests [specified in paragraph (d) of the proposal] be increased. One commenter states that an estimate of 2 work hours is more realistic for accomplishment of the adjustments and tests. The second commenter states that the operational tests would actually take approximately 2.5 work hours. The FAA does not concur. The information provided by the manufacturer to the FAA indicates that the adjustments/tests and the operational tests each take approximately one hour to accomplish. The FAA established its work hour estimate based on that information. ATA requests that the FAA coordinate with Boeing a revision to the service bulletin to incorporate a change for routing certain wiring, since one ATA member had to deviate from the service bulletin instructions to route certain wire bundles. The commenter does not specify the service bulletin it recommends be revised. The FAA has coordinated with Boeing all requests from operators concerning wire bundle routing, and has ensured that any necessary changes to service bulletin instructions have been incorporated in subsequent revisions to the service bulletins cited in this final rule. A summary of service bulletin revisions reviewed and approved by the FAA since the issuance of the proposed rule follows: 1. Boeing Service Bulletin 737-78-1053, Revision 2, dated February 17, 1994, and Revision 3, dated June 30, 1994: Revision 2 of the service bulletin adds notes explaining that certain wire bundles were installed in production on some of the affected airplanes, that installation of these wire bundles is not necessary for those airplanes, and that wire bundle W084 is necessary on only some of the affected airplanes. Certain revised drawings also are included in Revision 2, one subkit number is corrected, a list of fasteners is added, and procedures for installation of splices is added. Revision 3 of the service bulletin provides procedures for replacement of different aluminum foil markers on a particular circuit breaker panel on some airplanes. Paragraph (b) of the final rule has been revised to reflect Revisions 2 and 3 of this service bulletin as additional sources of service information. 2. Boeing Service Bulletin 737-78-1058, Revision 1, dated February 17, 1994, and Revision 2, dated July 7, 1994: Revision 1 of the service bulletin includes a list of fasteners and provides procedures for removal of two panels for access to the J20 box assembly and related wiring. That revision also provides improved procedures for removal of the thrust reverser manual drive units and installation of the sync- locks. Revision 2 of the service bulletin revises certain test procedures for the thrust reverser system. Paragraph (c) of the final rule has been revised to reflect Revisions 1 and 2 of this service bulletin as additional sources of service information. The FAA has revised the applicability of the final rule to clarify its intent that the AD applies to Model 737-300, -400, and -500 series airplanes equipped with CFM International CFM56-3 series engines. The applicability of the proposed rule stated incorrectly that Model 737- 300, -400, and -500 series airplanes equipped with General Electric CFM56 series engines were affected by this AD. After 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. It should be noted that no evidence currently exists that in-flight deployment of a thrust reverser was responsible for the accident involving a Boeing Model 737-300 series airplane that occurred on September 8, 1994. There are approximately 1,079 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 531 airplanes of U.S. registry will be required to accomplish adjustments and tests of the thrust reverser system, installation of the sync-lock, and operational tests of the sync-lock installation. The FAA estimates that it will take approximately 1 work hour per airplane to accomplish the required adjustments and tests, 198 work hours to accomplish the required installation, and 1 work hour to accomplish the required operational tests. The average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators of airplanes on which the sync-lock feature was not installed during production or as a modification is estimated to be $5,841,000, or $11,000 per airplane. The FAA estimates that 8 airplanes of U.S. registry will be required to accomplish adjustments and tests of the thrust reverser, modification of the sync-lock wiring, and operational tests of the sync-lock installation. The FAA estimates that it will take approximately 1 work hour to accomplish the required adjustments and tests, 70 work hours to accomplish the required wiring modification, and 1 work hour to accomplish the required operational tests. The average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators of airplanes on which the sync-lock feature was installed during production or as a modification is estimated to be $31,680, or $3,960 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $5,872,680. The 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. The FAA recognizes the large number of work hours required to accomplish the modification. The 5-year compliance time specified in paragraphs (b) and (c) of this AD should allow the sync-lock installation and wiring modification to be accomplished coincidentally with scheduled major airplane inspection and maintenance activities, thereby minimizing the costs associated with special airplane scheduling. The 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. For 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. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. Adoption of the Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39--AIRWORTHINESS DIRECTIVES 1. The 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. Sec. 39.13 [Amended] 2. Section 39.13 is amended by adding the following new airworthiness directive: 94-21-05 Boeing: Amendment 39-9047. Docket 93-NM-122-AD. Applicability: Model 737-300, -400, and -500 series airplanes equipped with CFM International CFM56-3 series engines, certificated in any category. Compliance: Required as indicated, unless accomplished previously. To prevent deployment of a thrust reverser in flight and subsequent reduced controllability of the airplane, accomplish the following: (a) For airplanes on which the sync-lock installation [specified in paragraph (b) of this AD], sync-lock wiring modification [specified in paragraph (c) of this AD], or Production Revision Record (PRR) 35105 has not been accomplished: Within 60 days after the effective date of this AD, and thereafter at intervals not to exceed 4,000 hours time-in-service, perform adjustments and tests of the thrust reverser system that are specified in Section 78-31-00 of the Boeing 737 Maintenance Manual to verify proper operation of the thrust reverser system, in accordance with that section of the maintenance manual. If any discrepancy is found, prior to further flight, accomplish either paragraph (a)(1) or (a)(2) of this AD. (1) Repair any discrepancy found, in accordance with procedures described in the Boeing 737 Maintenance Manual. Or (2) Deactivate the associated thrust reverser in accordance with the existing provisions and limitations specified in the Master Minimum Equipment List (MMEL). (b) For airplanes on which the sync-lock feature was not installed during production or as a modification in accordance with Boeing Service Bulletin 737-78-1053, dated December 17, 1992: Within 5 years after the effective date of this AD, install an additional thrust reverser system locking feature (sync-lock installation) in accordance with Boeing Service Bulletin 737-78-1053, Revision 1, dated July 1, 1993; Revision 2, dated February 17, 1994; or Revision 3, dated June 30, 1994. Installation of the additional locking feature constitutes terminating action for the tests required by paragraph (a) of this AD. (c) For airplanes listed in Boeing Service Bulletin 737-78-1058, dated July 1, 1993: Within 5 years after the effective date of this AD, modify the sync-lock wiring in accordance with Boeing Service Bulletin 737-78-1058, dated July 1, 1993; Revision 1, dated February 17, 1994; or Revision 2, dated July 7, 1994. Modification of the sync-lock wiring constitutes terminating action for the tests required by paragraph (a) of this AD. (d) At the times specified in paragraph (e) of this AD, accomplish the ``Thrust Reverser Sync-lock Integrity Test'' specified below to verify that the sync-locks are not failing in the unlocked state. If any discrepancy is found, prior to further flight, accomplish paragraph (d)(1) or (d)(2) of this AD. (1) Repair any discrepancy found, in accordance with procedures specified in the Boeing 737 Maintenance Manual. Or (2) Deactivate the associated thrust reverser in accordance with the existing provisions and limitations specified in the MMEL. The sync-locks installed on the deactivated thrust reverser must remain operational. ``Thrust Reverser Sync-lock Integrity Test 1. General A. Use this procedure to test the integrity of the thrust reverser sync-locks. The procedure must be performed on each engine. 2. Thrust Reverser Sync-Lock Test A. Prepare for the Thrust Reverser Sync-Lock test. (1) Do the steps that follow to supply power to the thrust reverser system: (a) Make sure the thrust levers are in the idle position. (b) Make sure the thrust reversers are retracted and locked. (c) Make sure these circuit breakers on the P6 circuit breaker panel are closed: (1) Engine 1 thrust reverser cont sys (2) Engine 2 thrust reverser cont sys (3) Engine 2 thrust reverser cont sys-alt (4) Engine 1 thrust reverser ind sys (5) Engine 2 thrust reverser ind sys (6) Engine 1 Sync-lock (7) Engine 2 Sync-lock (8) Engine 2 Sync-lock-ALTN (9) Landing gear air/gnd relay and lights (10) Radio ALTM-2 (d) Make sure this circuit breaker on the P18 circuit breaker panel is closed: (1) Radio ALTM-1 (e) Supply electrical power. (f) Remove pressure from the A (for the left engine) or B (for the right engine) hydraulic system. B. Do the thrust reverser sync-lock test. (1) Move and hold the manual unlock lever on the upper actuator on both thrust reverser sleeves to the unlock position. (2) Make sure the thrust reverser sleeves did not move aft. (3) Move the left (right) reverse thrust lever up and rearward to the reverse thrust position. (4) Make sure both thrust reverser sleeves move aft (approximately 0.15 to 0.25 inch). (5) Release the manual unlock lever on the upper actuators. Warning: Make sure all persons and equipment are clear of the area around the thrust reverser. When you apply hydraulic pressure, the thrust reverser will extend and can cause injuries to persons or damage to equipment. (6) Pressurize the A (B) hydraulic system. (7) Make sure the thrust reverser extends. (8) Move the left (right) reverse thrust lever to the forward and down position to retract the thrust reverser. C. Put the airplane back to its usual condition. (1) Remove hydraulic pressure. (2) Remove electrical power. D. Repeat the thrust reverser sync-lock test on the other engine.'' (e) Accomplish the test required by paragraph (d) of this AD at the times specified in paragraph (e)(1) or (e)(2) of this AD, as applicable. (1) For airplanes that are subject to the requirements of paragraphs (b) and (c) of this AD: Within 4,000 hours time-in- service after accomplishing the modification required by paragraph (b) or (c) of this AD, as applicable, 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. (2) For all other airplanes: Within 4,000 total hours time-in- service, 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. (f) An 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. Note: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (g) Special flight permits may be issued in accordance with Secs. 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. (h) The installation and wiring modification shall be done in accordance with Boeing Service Bulletin 737-78-1053, Revision 1, dated July 1, 1993; Boeing Service Bulletin 737-78-1053, Revision 2, dated February 17, 1994; Boeing Service Bulletin 737-78-1053, Revision 3, dated June 30, 1994; Boeing Service Bulletin 737-78- 1058, dated July 1, 1993; Boeing Service Bulletin 737-78-1058, Revision 1, dated February 17, 1994; or Boeing Service Bulletin 737- 78-1058, Revision 2, dated July 7, 1994. 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. (i) This amendment becomes effective on November 25, 1994. Issued in Renton, Washington, on October 6, 1994. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 94-25294 Filed 10-24-94; 8:45 am] BILLING CODE 4910-13-U