Explanation of Requirements of Rule

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of this same type design, this AD supersedes AD 20000233 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. This AD also adds an appendix and revises certain actions in the existing AD. Determination of Rule's Effective Date

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire.

Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption ADDRESSES. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAApublic contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a selfaddressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 2000NM93AD.'' The postcard will be date stamped and returned to the commenter.

Regulatory Impact

The regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a ``significant regulatory action'' under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket.

A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

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 part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39AIRWORTHINESS 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 removing amendment 3911551 (65 FR 5742, February 7, 2000), and by adding a new airworthiness directive (AD), amendment 3911711, to read as follows:
20000903 Boeing: Amendment 3911711. Docket 2000NM93AD.

Supersedes AD 20000233, Amendment 3911551.

Applicability: Model 747400 series airplanes equipped with General Electric (GE) CF680C2 series engines, certificated in any category.

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 (d) 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 in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight, accomplish the following:
Repetitive Functional Tests
(a) Within 1,000 hours timeinservice after the most recent test of the center drive unit (CDU) cone brake as specified in paragraph (b)(1) of AD 941505, amendment 398976; or within 650 hours timeinservice after the effective date of this AD; whichever occurs later: Perform a functional test to detect discrepancies of the CDU cone brake on each thrust reverser as specified in paragraph (a)(1) or (a)(2) of this AD, as applicable.
(1) For Model 747400 series airplanes equipped with thrust reversers that have NOT been modified in accordance with Boeing Service Bulletin 747782151 or a production equivalent: Perform the test in accordance with Boeing Service Bulletin 74778A2166, Revision 1, dated October 9, 1997; or the applicable section of paragraph III.A. of the Accomplishment Instructions of Boeing Service Bulletin 74778A2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997. Repeat the test thereafter at intervals not to exceed 650 hours timeinservice.
(2) For Model 747400 series airplanes equipped with thrust reversers that HAVE been modified in accordance with Boeing Service Bulletin 747782151 or a production equivalent: Perform the test in accordance with Appendix 1 (including Figure 1) of this AD. Repeat the test thereafter at intervals not to exceed 1,000 hours timein service.

Note 2: Accomplishment of the CDU cone brake test during production in accordance with Production Revision Record (PRR) 80452102 prior to the effective date of this AD is considered acceptable for compliance
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with the initial test required by paragraph (a) of this AD.

Note 3: Model 747400 series airplanes, line numbers 1061 and subsequent, equipped with GE CF680C2 engines, had a third locking system installed during production in accordance with Production Revision Record (PRR) 80452102, and were not modified in accordance with Boeing Service Bulletin 747782151 (which is a retrofit action for airplanes having line numbers 700 through 1060 inclusive). Terminating Action
(b) Accomplishment of the functional test of the CDU cone brake, as specified in paragraph (a) of this AD, constitutes terminating action for the repetitive tests of the CDU cone brake required by paragraph (b)(1) of AD 941505.
Corrective Action
(c) If any functional test required by paragraph (a) of this AD cannot be successfully performed as specified in the referenced service bulletin, or if any discrepancy is detected during any functional test required by paragraph (a) of this AD, accomplish either paragraph (c)(1) or (c)(2) of this AD.
(1) Prior to further flight, repair in accordance with Boeing Service Bulletin 74778A2166, Revision 1, dated October 9, 1997; or Boeing Service Bulletin 74778A2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997.

Or,
(2) The airplane may be operated in accordance with the provisions and limitations specified in the operator's FAAapproved MEL, provided that no more than one thrust reverser on the airplane is inoperative.
Alternative Methods of Compliance
(d)(1) 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.
(2) Alternative methods of compliance approved previously in accordance with AD 20000233, Amendment 3911551, are considered to be approved as alternative methods of compliance with this AD.

Note 4: 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
(e) Special 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.
Incorporation by Reference
(f) Except as provided by paragraphs (a)(2) and (c)(2) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 74778A2166, Revision 1, dated October 9, 1997; Boeing Service Bulletin 74778A2113, Revision 2, dated June 8, 1995; and Boeing Service Bulletin 74778A2113, Revision 3, dated September 11, 1997. This incorporation by reference was previously approved by the Director of the Federal Register as of March 13, 2000 (65 FR 5742, February 7, 2000). Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 981242207. 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.
(g) This amendment becomes effective on May 19, 2000.

Appendix 1.Thrust Reverser CDU Cone Brake Test

1. This procedure contains steps to do a check of the holding torque of the CDU cone brake.

2. CDU cone brake check (Figure 1):

A. Prepare to do the check:
(1) Open the fan cowl panels.
(2) Pull up on the manual release handle to unlock the electro mechanical brake.
(3) Pull the manual brake release lever on the CDU to release the cone brake.

Note: This will release the preload tension that may occur during a stow cycle.
(4) Return the manual brake release lever to the locked position to engage the cone brake.
(5) Remove the two bolts that hold the lockout plate to the CDU and remove the lockout plate.
(6) Install a \1/4\inch drive and a dialtype torque wrench into the CDU drive pad.

FOR FURTHER INFORMATION CONTACT

Holly Thorson, Aerospace Engineer, Propulsion Branch, ANM140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 980554056; telephone (425) 2271357; fax (425) 2271181.