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Airworthiness Directives; Boeing Model 747 and 767 Series Airplanes Equipped With General Electric CF6-80C2 Series Engines

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Information about this document as published in the Federal Register.

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 and 767 series airplanes, that requires repetitive functional tests of the directional pilot valve (DPV) of the thrust reversers to detect pneumatic leakage, and corrective action, if necessary. This amendment is prompted by a report of a latent failure mode of the fail-safe features of the thrust reverser system identified as possible leakage of the DPV that is due to a poppet being jammed slightly open or a leaking o-ring. 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, which could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane.

DATES:

Effective October 5, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of October 5, 2000.

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.

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FOR FURTHER INFORMATION CONTACT:

Dennis Kammers, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2793; fax (425) 227-1181.

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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 747 and 767 series airplanes series airplanes was published in the Federal Register on March 16, 2000 (65 FR 14216). That action proposed to require repetitive functional tests of the directional pilot valve (DPV) of the thrust reversers to detect pneumatic leakage, and corrective action, if necessary.

Comments

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Supportive Comment

One commenter concurs with the proposed rule and states that it has accomplished the initial inspection (functional test) specified in the proposal, and has incorporated the 5,000 hour repetitive inspection (test) requirements into its existing maintenance program for the affected airplanes.

Request Credit for Previous Accomplishment of Functional Test

One commenter requests that the FAA revise the proposal to provide credit for accomplishment of the directional pilot valve (DPV) functional test during production. The FAA concurs. The required DPV functional test can be accomplished in accordance with either the service bulletin or a production equivalent. A note has been added to the final rule to clarify that credit is given for previous accomplishment of the DPV functional test during production.

Request To Extend Repetitive Test Interval

One commenter requests that the FAA extend the interval for the proposed repetitive functional tests, as specified in paragraph (b) of the proposal, from 5,000 flight hours to 6,000 flight hours. The commenter states that the 6,000-flight-hour interval coincides with the check recommended in the Boeing 767 Maintenance Planning Document, and would allow operators to accomplish the functional test during scheduled “C” checks. The commenter adds that this extension would decrease the necessity to schedule additional maintenance time for its airplanes in order to meet the 5,000 flight-hour requirement.

The FAA concurs with the commenter's request. The intent of the AD is that the functional tests be conducted during a regularly scheduled maintenance visit, for the majority of the affected fleet, while still ensuring the thrust reverser system integrity. This would occur when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. Based on the information supplied by the commenter, the FAA now recognizes that an interval of 6,000 flight hours corresponds more closely to most of the affected operators' normal maintenance schedules. Paragraph (b) of the final rule has been revised to require accomplishment of the repetitive tests at intervals not to exceed 6,000 flight hours.

Request To Revise Cost Impact Information

One commenter notes that the proposed rule incorrectly states, “None of the Model 747 series airplanes affected by this action are on the U.S. Register.” The commenter states that this is inaccurate because all of its Model 747 series airplanes are affected by the proposed rule.

In light of the information supplied by the commenter, the FAA agrees that there are eight Model 747 series airplanes on the U.S. Register that are affected by this final rule. Therefore, the cost impact information, below, has been revised accordingly. Start Printed Page 52906

Terminating Modification

One commenter states that the proposed rule appears to be open-ended in that there is no modification available to correct the potential latent failure of the DPV and terminate the DPV inspections/tests. The commenter requests information on any planned corrective modification to the DPV in the future.

The FAA agrees with the commenter's observation that there is no proposed modification to the potential latent failure of the DPV or to terminate the repetitive DPV inspections/tests. Since the issuance of the proposed rule, the manufacturer has advised the FAA that it is developing a modified DPV that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking. That rulemaking may provide terminating action for the requirements of this final rule if a DPV that is not subject to the unsafe condition is approved for installation on an airplane equipped with GE CF6-80C2 series engines.

Request To Revise Paragraph (c)

One commenter states that paragraph (c) of the proposal should be revised to allow use of the 747-400 Dispatch Deviations Procedures Guide-specifically, minimum equipment list (MEL) Chapter 78-31-1, which enables airplanes to dispatch with a thrust reverser deactivated for up to 10 days. The commenter states that this ensures flight safety. The FAA does not concur. The MEL is not intended to provide safeguard measures for hardware with known, potentially catastrophic, failure modes. While this DPV failure mode does not lead directly to a thrust reverser deployment, it does lower the overall reliability of the thrust reverser system. Therefore, when DPV leakage is identified, this AD requires correction of the problem, rather than deferral. No change to paragraph (c) of the final rule is necessary in this regard.

Conclusion

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.

Cost Impact

There are approximately 418 Model 747 and 767 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 116 airplanes of U.S. registry will be affected by this AD.

For affected Model 747 series airplanes (8 U.S.-registered airplanes): It will take approximately 20 work hours (5 work hours per engine) to accomplish the required functional test, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the functional test required by this AD on U.S. operators is estimated to be approximately $9,600, or $1,200 per airplane, per test cycle.

For affected Model 767 series airplanes (108 U.S.-registered airplanes): It will take approximately 10 work hours (5 work hours per engine) per airplane to accomplish the required functional test, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the functional test required by this AD on U.S. operators is estimated to be $64,800, or $600 per airplane, per test cycle.

The cost impact figures discussed above are 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 cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

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.

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.

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List of Subjects in 14 CFR Part 39

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Adoption of the Amendment

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Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (

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PART 39—AIRWORTHINESS DIRECTIVES

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1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]
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2. Section 39.13 is amended by adding the following new airworthiness directive:

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2000-17-06 Boeing: Amendment 39-11880. Docket 2000-NM-24-AD.

Applicability: Model 747 and 767 series airplanes equipped with General Electric CF6-80C2 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, which could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane, accomplish the following:

Repetitive Functional Tests

(a) For Model 747 and 767 series airplanes equipped with thrust reversers that HAVE NOT been modified in accordance with Boeing Service Bulletin 747-78-2151 or 767-78-0063, as applicable, or a production equivalent: Within 60 days after the effective date of this AD, perform a functional test of the directional pilot valve (DPV) of the thrust reversers to detect pneumatic leakage in accordance with Boeing Alert Service Bulletin 747-78A2170, or Boeing Service Bulletin 767-78-0084, as applicable, both Start Printed Page 52907dated October 21, 1999. Repeat the functional test thereafter at intervals not to exceed 1,000 flight hours.

(b) For Model 747 and 767 series airplanes equipped with thrust reversers that have been modified in accordance with Boeing Service Bulletin 747-78-2151 or 767-78-0063, as applicable, or a production equivalent: Within 180 days after the effective date of this AD, perform a functional test of the DPV of the thrust reversers to detect pneumatic leakage in accordance with Boeing Alert Service Bulletin 747-78A2170, or Boeing Service Bulletin 767-78-0084, as applicable, both dated October 21, 1999. Repeat the functional test thereafter at intervals not to exceed 6,000 flight hours.

Note 2:

For airplanes modified during production: Functional tests accomplished in accordance with a production equivalent are acceptable for the initial functional test required by paragraph (b) of this AD.

Corrective Action

(c) If any functional test required by paragraph (a) or (b) of this AD cannot be successfully performed as specified in Boeing Alert Service Bulletin 747-78A2170, or Boeing Service Bulletin 767-78-0084, as applicable, both dated October 21, 1999; or if any discrepancy is detected during any functional test required by paragraph (a) or (b) of this AD: Prior to further flight, correct the discrepancy in accordance with the procedures specified in the applicable Boeing Model 747 or 767 Airplane Maintenance Manual. Additionally, prior to further flight, any failed functional test required by paragraph (a) or (b) of this AD must be repeated and successfully accomplished. Repeat the functional test thereafter at the intervals required by paragraph (a) or (b) of this AD, as applicable.

Alternative Methods of Compliance

(d) 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 3:

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 (b) and (c) of this AD, the functional test shall be done in accordance with Boeing Alert Service Bulletin 747-78A2170, dated October 21, 1999; or Boeing Service Bulletin 767-78-0084, dated October 21, 1999. 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.

(g) This amendment becomes effective on October 5, 2000.

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Issued in Renton, Washington, on August 21, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 00-21717 Filed 8-30-00; 8:45 am]

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