[Federal Register Volume 64, Number 207 (Wednesday, October 27, 1999)] [Proposed Rules] [Pages 57802-57806] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 99-28084] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. 99-NM-64-AD] RIN 2120-AA64 Airworthiness Directives; Boeing Model 747 Series Airplanes AGENCY: Federal Aviation Administration, DOT. ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes equipped with General Electric Model CF6-45 or -50 series engines. This proposal would require repetitive inspections and tests of the thrust reverser control and indication system, and corrective actions, if necessary. This proposal would also require installation of a thrust reverser actuation system (TRAS) lock, repetitive functional tests of that installation, and repair, if necessary. Installation of the TRAS lock would terminate the repetitive inspections and certain tests. This proposal is prompted by the results of a safety review, which revealed that in-flight deployment of a thrust reverser could result in a significant reduction in airplane controllability. The actions specified by the proposed AD are intended to ensure the integrity of the fail-safe features of the thrust reverser system by preventing possible failure modes, which could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane. DATES: Comments must be received by December 13, 1999. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-64-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. FOR FURTHER INFORMATION CONTACT: Larry Reising, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2683; fax (425) 227-1181. SUPPLEMENTARY INFORMATION: Comments Invited Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received. [[Page 57803]] Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket. Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 99-NM-64-AD.'' The postcard will be date stamped and returned to the commenter. Availability of NPRMs Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-64-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Discussion On May 26, 1991, a Boeing Model 767-300ER series airplane was involved in an accident as a result of an uncommanded in-flight deployment of a thrust reverser. Following that accident, a study was conducted to evaluate the potential effects of an uncommanded thrust reverser deployment throughout the flight regime of other Boeing airplane models, including the Boeing Model 747 series airplane equipped with General Electric Model CF6-45 or -50 series engines. The study included a re-evaluation of the thrust reverser control system fault analysis and airplane controllability. The results of the evaluation revealed that, if not prevented, possible combinations of failures within the thrust reverser control system may result in an in- flight deployment of a thrust reverser and that, in the event of thrust reverser deployment during high-speed climb using high engine power, or during cruise, these airplanes may not be controllable. The FAA has prioritized the issuance of AD's for corrective actions for the thrust reverser system on Boeing airplane models following the 1991 accident. Based on service experience, analyses, and flight simulator studies, it was determined that an in-flight deployment of a thrust reverser has more effect on controllability of twin-engine airplane models than of Model 747 series airplanes, which have four engines. For this reason, the highest priority was given to rulemaking that required corrective actions for the twin-engine airplane models. AD's that correct the same type of unsafe condition as that addressed by this AD have been previously issued for specific airplanes within the Boeing Model 737, 757, and 767 series. Service experience has shown that in-flight thrust reverser deployments have occurred on Model 747 airplanes in certain flight conditions with no significant airplane controllability problems being reported. However, the manufacturer has been unable to establish that acceptable airplane controllability would be achieved throughout the operating envelope of the airplane following such a deployment. Additionally, safety analyses performed by the manufacturer and reviewed by the FAA, have been unable to establish that the risks for uncommanded thrust reverser deployment at critical flight conditions are acceptably low. Explanation of Relevant Service Information The FAA has reviewed and approved the following service bulletins:Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995, describes procedures for repetitive inspections and tests to verify proper operation of the thrust reverser stow/deploy switches, the bullnose seals, the airmotor brake, the overpressure shutoff valve electrical connectors, the flexible shafts, the directional pilot valve, and the microswitch pack on each engine; and repair, if necessary. Boeing Service Bulletin 747-78-2150, Revision 1, dated July 2, 1998, describes procedures for installation of a thrust reverser actuation system (TRAS) lock on each thrust reverser half of each engine. This service bulletin specifies that prior or concurrent incorporation of Boeing Service Bulletin 747-78-2067, Boeing Service Bulletin 747-78-2069, Boeing Service Bulletin 747-78-2133, Middle River Aircraft Systems CF6-50 Service Bulletin 78-3011, and Middle River Aircraft Systems CF6-50 Service Bulletin 78-3013, is necessary. Such installation eliminates the need for the repetitive inspections and tests described in Boeing Alert Service Bulletin 747-78A2160. The FAA has also reviewed Chapter 78-34-00 of the Boeing 747 Maintenance Manual, dated April 25, 1998, which describes procedures for repetitive functional tests of the TRAS lock. Accomplishment of the modification specified in Boeing Service Bulletin 747-78-2150, Revision 1, and the repetitive functional tests specified in the maintenance manual are intended to adequately address the identified unsafe condition. The modification procedures described by Boeing Service Bulletin 747-78-2150, dated March 20, 1997, have been validated previously, and the necessary changes have been incorporated into Revision 1 of the service bulletin. The FAA has determined that the procedures described by Boeing Service Bulletin 747-78-2150, Revision 1, and the numerous referenced service bulletins, have been sufficiently validated to now propose that this modification be required. Several airplanes have been successfully modified in accordance with the service bulletin, and this past experience should minimize the likelihood for subsequent service bulletin revisions, requests for alternative methods of compliance, and superseding AD's. Explanation of Requirements of Proposed Rule Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require repetitive inspections and tests of the thrust reverser control and indication system, and corrective actions, if necessary. The proposed AD would also require installation of a TRAS lock, repetitive functional tests of that installation, and repair, if necessary. Installation of the TRAS lock would terminate the repetitive inspections and certain tests. This proposed AD would also include a provision for deactivation of one thrust reverser in accordance with Section 78-1 of Boeing Document D6-33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,'' Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may be deactivated under the provisions of this document. Differences Between Proposed Rule and Service Bulletins The effectivity of Boeing Alert Service Bulletin 747-78A2160 identifies all Model 747-100 and -200 series airplanes powered by General Electric Model CF6-45 or -50 series engines, line numbers 232 through 886 inclusive; however, this proposed AD would apply to all Model 747 series airplanes powered by General Electric Model CF6-45 or -50 series engines. The FAA has been notified by the airplane [[Page 57804]] manufacturer that there are Model 747-300 and 747SR series airplanes, and airplanes having line numbers lower than 232, that are powered by Model CF6-45 or -50 series engines. Operators should note that, although Boeing Alert Service Bulletin 747-78A2160 recommends accomplishing the inspections and tests within 1,500 flight hours or 4 months (after the release of the service bulletin), the FAA has determined that the recommended interval would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the inspection. In light of all of these factors, the FAA finds a 90-day compliance time for initiating the inspections and tests of the thrust reverser stow/deploy switches, the bullnose seals, and the airmotor brakes; and a 6-month compliance time for initiating the inspections and tests of the overpressure shutoff valve electrical connectors, the flexible shafts, the directional pilot valves, and the microswitch packs; to be warranted, in that those times represent appropriate intervals of time allowable for affected airplanes to continue to operate without compromising safety. Operators should also note that, although Boeing Service Bulletin 747-78-2150, Revision 1, does not specify a compliance time for accomplishment of installation of the TRAS locks, this proposal would require that action to be accomplished within 36 months after the effective date of this AD. In developing an appropriate compliance time for this proposed AD, the FAA considered the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to accomplish the proposed actions (approximately 791 work hours). In light of these factors, the FAA finds a compliance time of 36 months for accomplishing the proposed actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety. Although not described in either service bulletin, this proposed AD would allow the option to dispatch an airplane with one thrust reverser deactivated and operate the airplane for up to 10 days with one thrust reverser deactivated. This option would be allowed in the event of unsuccessful accomplishment of the repetitive inspections and tests specified in paragraphs (a) and (b) of this AD or installation of a spare thrust reverser assembly with a different configuration than that installed on the other engines of the airplane. Cost Impact There are approximately 138 airplanes of the affected design in the worldwide fleet. The FAA estimates that 27 airplanes of U.S. registry would be affected by this proposed AD. It would take approximately 12 work hours per airplane to accomplish the proposed inspections and tests of the thrust reverser stow/deploy switches, the bullnose seals, and the airmotor brakes, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed repetitive inspections and tests on U.S. operators is estimated to be $19,440, or $720 per airplane, per inspection and test cycle. It would take approximately 11 work hours per airplane to accomplish the proposed inspections and tests of the overpressure shutoff valve electrical connectors, the flexible shafts, the directional pilot valves, and the microswitch packs, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed repetitive inspections and tests on U.S. operators is estimated to be $17,820, or $660 per airplane, per inspection and test cycle. It would take approximately 791 work hours per airplane to accomplish the proposed installation of TRAS locks, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of the proposed installation on U.S. operators is estimated to be $1,281,420, or $47,460 per airplane. This cost impact figure does not reflect the cost of the modifications described in the service bulletins listed in paragraph I.K.1.h. of Boeing Service Bulletin 747-78-2150, Revision 1, that are proposed to be accomplished prior to, or concurrently with, the installation of the TRAS lock. (The cost impact figure does reflect the cost of the modifications described in the service bulletins listed in paragraph I.K.1.j. of the service bulletin that are also proposed to be accomplished prior to, or concurrently with, the installation of the TRAS lock.) Since some operators may have accomplished certain modifications on some or all of the airplanes in its fleet, while other operators may not have accomplished any of the modifications on any of the airplanes in its fleet, the FAA is unable to provide a reasonable estimate of the cost of accomplishing the terminating actions described in the service bulletins listed in paragraph I.K.1.h. of Boeing Service Bulletin 747-78-2150. As indicated earlier in this preamble, the FAA invites comments specifically on the overall economic aspects of this proposed rule. Any data received via public comments to this proposed AD will aid the FAA in developing an accurate accounting of the cost impact of the rule. It would take approximately 4 work hours per airplane to accomplish the proposed functional test of the TRAS lock, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed repetitive functional tests on U.S. operators is estimated to be $6,480, or $240 per airplane, per test cycle. The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. Regulatory Impact The regulations proposed herein would 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. For the reasons discussed above, I certify that this proposed regulation (1) is not a ``significant regulatory action'' under Executive Order 12866; (2) is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety. [[Page 57805]] The Proposed Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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. 106(g), 40113, 44701. Sec. 39.13 [Amended] 2. Section 39.13 is amended by adding the following new airworthiness directive: Boeing: Docket 99-NM-64-AD. Applicability: Model 747 series airplanes; certificated in any category; equipped with General Electric Model CF6-45 or -50 series engines. Note 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 (h) 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. Compliance: Required as indicated, unless accomplished previously. To ensure the integrity of the fail-safe features of the thrust reverser system by preventing possible failure modes, which could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane, accomplish the following: Repetitive Inspections and Tests Note 2: For the purposes of this AD, a detailed visual inspection is defined as: ``An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.'' (a) Within 90 days after the effective date of this AD, perform the applicable detailed visual inspections and tests to verify proper operation of the thrust reverser stow/deploy switches, the bullnose seals, and the airmotor brake on each engine, in accordance with Work Package I of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995. Repeat the applicable inspections and tests thereafter at intervals not to exceed 1,300 flight hours, until accomplishment of paragraph (d) of this AD. (b) Within 6 months after the effective date of this AD, perform the applicable detailed visual inspections and tests to verify proper operation of the overpressure shutoff valve electrical connectors, the flexible shafts, the directional pilot valve, and the microswitch pack on each engine, in accordance with Work Package II of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995. Repeat the applicable inspections and tests thereafter at intervals not to exceed 18 months, until accomplishment of paragraph (d) of this AD. Corrective Actions (c) If any of the inspections and tests required by paragraphs (a) and (b) of this AD cannot be successfully performed, or if any discrepancy is detected during the inspections and tests, accomplish paragraphs (c)(1) or (c)(2) of this AD, as applicable. (1) Prior to further flight, repair in accordance with Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995. Additionally, prior to further flight, any failed inspection or test required by paragraph (a) or (b) of this AD must be repeated and successfully accomplished. (2) Accomplish both paragraphs (c)(2)(i) and (c)(2)(ii) of this AD. (i) Prior to further flight, deactivate the associated thrust reverser in accordance with Section 78-1 of Boeing Document D6- 33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,'' Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may be deactivated under the provisions of this paragraph. Note 3: The airplane may be operated in accordance with the provisions and limitations specified in the operator's FAA-approved Master Minimum Equipment List, provided that no more than one thrust reverser on the airplane is inoperative. (ii) Within 10 days after deactivation of any thrust reverser in accordance with paragraph (c)(2)(i) of this AD, the affected thrust reverser must be repaired in accordance with Boeing Alert Service Bulletin 747-78A2160, dated May 4, 1995. Additionally, prior to further flight, any failed inspection or test required by paragraph (a) or (b) of this AD must be repeated and successfully accomplished; once such inspections and tests have been successfully accomplished, the thrust reverser may then be reactivated. Modification (d) Within 36 months after the effective date of this AD, install a thrust reverser actuation system (TRAS) lock on each thrust reverser half of each engine, in accordance with Boeing Service Bulletin 747-78-2150, Revision 1, dated July 2, 1998. All of the modifications described in the service bulletins listed in paragraphs I.K.1.h. and I.K.1.j. of Boeing Service Bulletin 747-78- 2150, Revision 1, must be accomplished, as applicable, in accordance with those service bulletins, prior to, or concurrently with, the accomplishment of the installation of the TRAS lock. Accomplishment of these actions constitutes terminating action for the repetitive inspections required by paragraphs (a) and (b) of this AD. Note 4: Accomplishment of the installation specified in Boeing Service Bulletin 747-78-2150, dated March 20, 1997, is acceptable for compliance with the installation required by paragraph (d) of this AD. Functional Tests (e) Within 3,000 flight hours after accomplishing the modification required by paragraph (d) of this AD, or within 1,000 flight hours after the effective date of this AD, whichever occurs later, perform a functional test of the TRAS lock on each reverser half, in accordance with Chapter 78-34-00 of the Boeing 747 Maintenance Manual, dated April 25, 1998. Correction Actions (1) If no discrepancy is detected, repeat the functional test thereafter at intervals not to exceed 3,000 flight hours. (2) If any discrepancy is detected, prior to further flight, repair in accordance with the procedures specified in the Boeing 747 Maintenance Manual. Additionally, prior to further flight, the functional test must be successfully accomplished. Repeat the functional test thereafter at intervals not to exceed 3,000 flight hours. Spares (f) If, after incorporation of the modification required by paragraph (d) of this AD on any airplane, it becomes necessary to install a thrust reverser assembly that does not have the TRAS locks installed, dispatch of the airplane is allowed in accordance with the provisions and limitations specified in the operator's FAA- approved Master Minimum Equipment List, provided that the thrust reverser assembly that does not have the TRAS locks installed is deactivated in accordance with Section 78-1 of Boeing Document D6- 33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,'' Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may be deactivated under the provisions of this paragraph. Within 10 days after deactivation of the thrust reverser, install a thrust reverser assembly that has the TRAS locks installed and reactivate the thrust reverser. (g) If, prior to incorporation of the modification required by paragraph (d) of this AD on any airplane, it becomes necessary to install a thrust reverser assembly that has the TRAS locks installed, dispatch of the airplane is allowed in accordance with the provisions and limitations specified in the operator's FAA- approved Master Minimum Equipment List, provided that the thrust reverser assembly that has the TRAS locks installed is deactivated in accordance with Section 78-1 of Boeing Document D6-33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures Guide,'' Revision 22, dated January 30, 1998. No more than one thrust reverser on any airplane may [[Page 57806]] be deactivated under the provisions of this paragraph. Within 10 days after deactivation of the thrust reverser, install a thrust reverser assembly that does not have the TRAS locks installed and reactivate the thrust reverser. Alternative Methods of Compliance (h) 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 5: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. Special Flight Permits (i) Special flight permits may be issued in accordance with Sec. Sec. 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. Issued in Renton, Washington, on October 21, 1999. D. L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-28084 Filed 10-26-99; 8:45 am] BILLING CODE 4910-13-P