AD 99-15-08

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747-200 and -300 series airplanes, that currently requires various inspections and functional tests to detect discrepancies of the thrust reverser control and indication system, and correction of any discrepancy found. This amendment reduces the repetitive interval for one certain functional test. This amendment is prompted by reports indicating that several center drive units (CDU) were returned to the manufacturer of the CDU's because of low holding torque of the CDU cone brake. The actions specified by this AD are intended to ensure the integrity of the fail safe features of the thrust reverser system by preventing possible failure modes in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight.

Final rule

99-15-08 BOEING: Amendment 39-11227. Docket 98-NM-247-AD. Supersedes AD 95-06-01, Amendment 39-9171. \n\n\tApplicability: Model 747-200 and -300 series airplanes equipped with General Electric Model CF6-80C2 series engines with Power Management Control engine controls, certificated in any category. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been 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 (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo ensure the integrity of the fail safe features of the thrust reverser system by preventing possible failure modes in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight, accomplish the following: \n\nRESTATEMENT OF REQUIREMENTS OF AD 95-06-01: \n\n\t(a)\tWithin 90 days after April 13, 1995 (the effective date of AD 95-06-01, amendment 39-9171), perform tests of the position switch module and the cone brake of the center drive unit (CDU) on each thrust reverser, and perform an inspection to detect damage to the bullnose seal on the translating sleeve on each thrust reverser, in accordance with paragraphs III.A. through III.C. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994. Repeat the tests and inspection thereafter at intervals not to exceed 1,000 hourstime-in-service until the functional test required by paragraph (d) of this AD is accomplished. \n\n\t(b)\tWithin 9 months after April 13, 1995, perform inspections and functional tests of the thrust reverser control and indication system in accordance with paragraphs III.D. through III.F., III.H., and III.I. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994. Repeat these inspections and functional tests thereafter at intervals not to exceed 18 months. \n\n\t(c)\tIf any of the inspections and/or functional tests required by paragraphs (a) and (b) of this AD cannot be successfully performed, or if any discrepancy is found during those inspections and/or functional tests, accomplish either paragraph (c)(1) or (c)(2) of this AD. \n\n\t\t(1)\tPrior to further flight, correct the discrepancy found, in accordance with Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994. Or \n\n\t\t(2)\tThe airplane may be operated in accordance with the provisions and limitations specified in an operator's FAA-approved Minimum Equipment List (MEL), provided that no more than one thrust reverser on the airplane is inoperative. \n\nNEW REQUIREMENTS OF THIS AD: \n\n\t(d)\tWithin 1,000 hours time-in-service after the most recent test of the CDU cone brake performed in accordance with paragraph (a) of this AD, or within 650 hours time-in-service after the effective date of this AD, whichever occurs first: Perform a functional test to detect discrepancies of the CDU cone brake on each thrust reverser, in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997, or paragraph III.B. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994. Repeat the functional test thereafter at the interval specified in paragraph (d)(1) or (d)(2) of this AD, as applicable. Accomplishment of such functional test constitutes terminating action for the repetitive test of the CDU cone brakerequired by paragraph (a) of this AD. \n\n\t\t(1)\tFor airplanes equipped with thrust reversers NOT modified in accordance with Boeing Service Bulletin 747-78-2144, Revision 1, dated April 11, 1996: Repeat the functional test at intervals not to exceed 650 hours time-in-service. \n\n\t\t(2)\tFor airplanes equipped with thrust reversers modified in accordance with Boeing Service Bulletin 747-78-2144, Revision 1, dated April 11, 1996: Repeat the functional test at intervals not to exceed 1,000 hours time-in-service. \n\n\t(e)\tIf any functional test required by paragraph (d) of this AD cannot be successfully performed, or if any discrepancy is found during any functional test required by paragraph (d) of this AD, accomplish either paragraph (e)(1) or (e)(2) of this AD. \n\n\t\t(1)\tPrior to further flight, correct the discrepancy found, in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997, or paragraph III.B. of the Accomplishment Instructions of Boeing AlertService Bulletin 747-78A2130, dated May 26, 1994. Or \n\n\t\t(2)\tThe airplane may be operated in accordance with the provisions and limitations specified in the operator's FAA-approved MEL, provided that no more than one thrust reverser on the airplane is inoperative. \n\nAlternative Methods of Compliance \n\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, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\nSpecial Flight Permits \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\nIncorporation by Reference \n\n\t(h)\tExcept as provided by paragraphs (c)(2) and (e)(2) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994, or Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997, as applicable. \n\n\t\t(1)\tThe incorporation by reference of Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997, is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. \n\n\t\t(2)\tThe incorporation by reference of Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994, was approved previously by the Director of the Federal Register as of April 13, 1995 (60 FR 13623, March 14, 1995). \n\n\t\t(3)\tCopies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington98124-2207. 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 August 25, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 95-06-01, amendment 39-9171 (60 FR 13623, March 14, 1995), which is applicable to certain Boeing Model 747-200 and -300 series airplanes, was published in the Federal Register on January 21, 1999 (64 FR 3226). The action proposed to continue to require various inspections and functional tests to detect discrepancies of the thrust reverser control and indication system, and correction of any discrepancy found. The action also proposed to reduce the repetitive interval for one certain functional test. \n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received. \n\n\tThe commenter supports the proposed rule. \n\nExplanation of Change to the Final Rule \n\n\tIn the notice of proposed rulemaking (NPRM), the FAA proposed to require repetitivefunctional tests of the CDU cone brake on Model 747-200 and -300 series airplanes, at intervals not to exceed 650 hours time-in-service, regardless of whether the airplane is equipped with thrust reversers modified in accordance with Boeing Service Bulletin 747-78-2144. Since the issuance of the NPRM, the FAA has determined that a repetitive interval of 1,000 hours time-in-service would adequately ensure safety on airplanes equipped with thrust reversers modified in accordance with Boeing Service Bulletin 747-78-2144, Revision 1, dated April 11, 1996. This decision is based on the FAA's determination that frequent maintenance on such systems as the thrust reverser system could increase the risk of maintenance errors. Also, Boeing Service Bulletin 747-78-2144, Revision 1, recommends functional tests at intervals not to exceed 1,000 hours time-in-service for thrust reversers that have been modified to incorporate a third locking device in accordance with that service bulletin. Performing the functional test of the cone brake at the same interval as the functional test of the third locking device would allow both thrust reverser tests to be scheduled and performed at the same time. Therefore, paragraph (d) of this final rule has been revised accordingly, and new paragraphs (d)(1) and (d)(2) have been added to this final rule. \n\nConclusion \n\n\tAfter careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nInterim Action \n\n\tThis is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, theFAA may consider additional rulemaking. \n\nCost Impact \n\n\tThere are approximately 9 airplanes of the affected design in the worldwide fleet. The FAA estimates that 2 airplanes of U.S. registry will be affected by this AD.\n \n\tThe actions required by this AD will not add any additional economic burden on affected operators, other than the costs that are associated with repeating the functional test of the cone brake at reduced intervals (at intervals not to exceed 650 hours time-in-service rather than at intervals not to exceed 1,000 hours time-in-service). The current costs associated with AD 95-06-01 are reiterated in their entirety (as follows) for the convenience of affected operators. \n\n\tThe actions that are currently required by AD 95-06-01, and retained in this AD, take approximately 33 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $3,960, or $1,980 per airplane, per inspection/test cycle. \n\n\tThe 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\nRegulatory Impact \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\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. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\n\t2. Section 39.13 is amended by removing amendment 39-9171 (60 FR 13623, March 14, 1995), and by adding a new airworthiness directive (AD), amendment 39-11227, to read as follows: