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Proposed Rule

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:

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 and 767 series airplanes. This proposal would require repetitive functional tests of the directional pilot valve (DPV) of the thrust reversers to detect pneumatic leakage, and corrective action, if necessary. This proposal 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 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 May 1, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-24-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.

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FOR FURTHER INFORMATION CONTACT:

Holly Thorson, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1357; fax (425) 227-1181.

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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.

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 2000-NM-24-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. 2000-NM-24-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA received a report from the manufacturer indicating a new latent failure mode of the fail-safe features of the thrust reverser system. This failure mode was identified as possible leakage of the directional pilot valve (DPV) of the thrust reversers due to a poppet being jammed slightly open or a leaking o-ring. Such undetected leakage past the DPV could result in sufficient pnuematic pressure developing downstream of the DPV at takeoff thrust to actuate the directional control valve to the deploy position. This failure mode, in combination with another thrust reverser failure condition or component failure, could result in the following:

  • Significant degradation of the features intended to ensure that the thrust reverser remains stowed during all anticipated operating conditions for airplanes that have incorporated the thrust reverser actuation system brake. Or
  • A potential in-flight thrust reverser deployment for airplanes that have not incorporated the thrust reverser actuation system brake.

Such conditions, if not corrected, could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-78A2170, and Boeing Service Bulletin 767-78-0084, both dated October 21, 1999, which describe procedures for repetitive functional tests of the DPV of the thrust reversers to detect pneumatic leakage, and correction of any discrepancies. Accomplishment of the actions specified in the service bulletins is intended to adequately address the identified unsafe condition.

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 functional tests of the DPV of the thrust reversers to detect pneumatic leakage, and corrective Start Printed Page 14217action, if necessary. The actions are required to be accomplished in accordance with the service bulletins described previously, except as discussed below.

Correction of any discrepancy detected is required to be accomplished in accordance with the procedures described in the applicable Boeing 747 or 767 Airplane Maintenance Manual.

Cost Impact

There are approximately 331 Model 767 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 108 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 10 work hours (5 work hours per engine) per airplane to accomplish the proposed functional test, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the functional test proposed by this AD on U.S. operators is estimated to be $64,800, or $600 per airplane, per test cycle.

None of the Model 747 series airplanes affected by this action are on the U.S. Register. All Model 747 series airplanes included in the applicability of this rule currently are operated by non-U.S. operators under foreign registry; therefore, they are not directly affected by this AD action. However, the FAA considers that this rule is necessary to ensure that the unsafe condition is addressed in the event that any of these subject airplanes are imported and placed on the U.S. Register in the future.

Should an affected Model 747 series airplane be imported and placed on the U.S. Register in the future, it would require approximately 20 work hours (5 work hours per engine) to accomplish the proposed functional test, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the functional test proposed by this AD would be approximately $1,200 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 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 proposal would not have federalism implications under Executive Order 13132.

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.

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List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

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]

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

Boeing: 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:

(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 dated 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 5,000 flight hours.

(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 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permit

(e) Special flight permits may be issued in accordance with §§ 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.

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Issued in Renton, Washington, on March 10, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 00-6492 Filed 3-15-00; 8:45 am]

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