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Proposed Rule

Airworthiness Directives Boeing Model 747SP, SR, -100, -200, and -300 Series Airplanes Equipped with Pratt & Whitney Model JT9D-3, -7, -7Q, and -7R4G2 Series Engines

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747SP, SR, -100, -200, and -300 series airplanes, that currently requires repetitive operational tests of the reversible gearbox pneumatic drive unit (PDU) or the reversing air motor PDU to ensure that the unit can restrain the thrust reverser sleeve, and correction of any discrepancy found. This action would require installation of a terminating modification, and would add repetitive functional tests of that installation to detect discrepancies, and repair, if necessary. This proposal is prompted by the results of a safety review of the thrust reverser systems on Model 747 series airplanes. 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 in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight.

DATES:

Comments must be received by March 13, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-67-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:

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.

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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 99-NM-67-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-67-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Start Printed Page 4180

Discussion

On July 21, 1995, the FAA issued AD 95-16-02, amendment 39-9321 (60 FR 39631, August 3, 1995), applicable to certain Boeing Model 747SP, SR, -100, -200, and -300 series airplanes, to require repetitive operational tests of the reversible gearbox pneumatic drive unit (PDU) or the reversing air motor PDU to ensure that the unit can restrain the thrust reverser sleeve, and correction of any discrepancy found. That action was prompted by the results of an investigation, which revealed that, in the event of thrust reverser deployment during high-speed climb or during cruise, these airplanes could experience control problems. The requirements of that 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.

Actions Since Issuance of Previous Rule

In the preamble to AD 95-16-02, the FAA indicated that the actions required by that AD were considered “interim action” and that further rulemaking action was being considered. The FAA now has determined that further rulemaking action is indeed necessary, and this proposed AD follows from that determination.

Since the issuance of that AD, the FAA has prioritized the issuance of AD's for corrective actions for the thrust reverser system on Boeing airplane models following a 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 correcting the same type of unsafe condition 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 during 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 following these deployments throughout the operating envelope of the airplane. Additionally, safety analyses performed by the manufacturer and reviewed by the FAA, has been unable to establish that the risks for uncommanded thrust reverser deployment during critical flight conditions is acceptably low.

Explanation of Relevant Service Information

The FAA has reviewed and approved the following Boeing Service Bulletins:

  • 747-78-2134, Revision 3, dated March 19, 1998, which describes procedures for installation of provisional wiring for the additional locking system on the thrust reversers.
  • 747-78-2052, Revision 5, dated February 22, 1996, which describes procedures for removal of the thrust reverser sequencing mechanism and installation of a solenoid operated shutoff valve.

The service bulletins described previously reference the Boeing Standard Wiring Practices Manual, which describes wire installation procedures, and Boeing 747 Airplane Maintenance Manual (AMM) as additional sources of service information for accomplishment of the modifications.

  • 747-78-2152, Revision 1, dated December 12, 1996; Revision 2, dated December 18, 1997; and Revision 3, dated August 26, 1999, which describe procedures for, among other things, installation of the following:

1. Four additional microswitches and associated wiring in the aisle stand P8 panel;

2. New relay panels P252 and P253 and associated wiring;

3. Left and right wing/body disconnect panels, engine struts, and associated wiring;

4. Four circuit breakers and associated wiring changes in the P6 and P8 panels; and

5. Sync lock and associated wiring on each thrust reverser.

Accomplishment of Boeing Service Bulletin 747-78-2152, Revision 1, Revision 2, or Revision 3, requires prior or concurrent accomplishment of Boeing Service Bulletins 747-78-2134, Revision 3, and 747-78-2052, Revision 5. Accomplishment of these actions would eliminate the need for certain repetitive tests.

The modification procedures described by Boeing Service Bulletins 747-78-2152 and 747-78-2134 were previously validated by the manufacturer, and the necessary changes have been incorporated into the latest revisions of the service bulletins. The FAA has determined that the procedures specified in Boeing Service Bulletins 747-78-2152, Revision 1, Revision 2, and Revision 3, and 747-78-2134, Revision 3, as well as the other service bulletins referenced in this proposed AD, have been effectively validated and, therefore, proposes that this modification be required. Several airplanes have been successfully modified in accordance with the service bulletins, 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 supersede AD 95-16-02 to continue to require repetitive operational tests of the reversible gearbox pneumatic drive unit (PDU) or the reversing air motor PDU to ensure that the unit can restrain the thrust reverser sleeve, and correction of any discrepancy found. This proposed AD would require installation of a modification, and would add repetitive functional tests of that installation to detect discrepancies, and repair, if necessary. The actions would be required to be accomplished in accordance with the service bulletins described previously, except as discussed below.

Repetitive functional tests to detect discrepancies of the actuation system lock (also called a sync lock) on each thrust reverser would be required to be accomplished in accordance with the procedures described in the Boeing 747 Airplane Maintenance Manual (AMM). Correction of any discrepancy detected would be required to be accomplished in accordance with the AMM.

Differences Between Service Bulletins and This Proposed AD

Operators should note that, although Boeing Service Bulletin 747-78-2152, Revision 1, Revision 2, and Revision 3 recommend no specific compliance time for accomplishment of the additional lock installation, the FAA has determined that an unspecified compliance time 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 installation. In light of all of these factors, the FAA finds a 36-month compliance time for completing the required actions to be warranted, in that Start Printed Page 4181it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Operators also should note that, although the service bulletin does not specify repetitive functional testing of the additional lock installation following accomplishment of that installation, the FAA has determined that repetitive functional tests of the additional lock installation on each thrust reverser, at intervals not to exceed 3,000 flight hours, will support continued operational safety of thrust reversers with actuation system locks.

Cost Impact

There are approximately 457 airplanes of the affected design in the worldwide fleet. The FAA estimates that 220 airplanes of U.S. registry would be affected by this proposed AD.

The operational tests that are currently required by AD 95-16-02, and retained in this AD, take approximately 16 work hours (4 per engine) 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 $211,200, or $960 per airplane, per test cycle.

It would take approximately 544 work hours per airplane, to accomplish the proposed wiring modifications, at an average labor rate of $60 per work hour. Required parts would be provided by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the wiring modifications proposed by this AD on U.S. operators is estimated to be $7,180,800, or $32,640 per airplane.

It would take approximately 104 work hours (26 per engine) per airplane, to accomplish the proposed removal of the thrust reverser sequencing mechanism and installation of a solenoid operated shutoff valve, at an average labor rate of $60 per work hour. Required parts would be provided by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the removal and installation proposed by this AD on U.S. operators is estimated to be $1,372,800, or $6,240 per airplane.

It would take approximately 568 work hours per airplane, to accomplish the proposed sync lock hardware installation, at an average labor rate of $60 per work hour. Required parts would be provided by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the installation proposed by this AD on U.S. operators is estimated to be $7,497,600, or $34,080 per airplane.

The functional tests proposed in this AD would take approximately 8 work hours (2 hours per engine) per airplane to accomplish, 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 on U.S. operators is estimated to be $105,600, or $480 per airplane, per test cycle.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or 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.

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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 removing amendment 39-9321 (60 FR 39631, August 3, 1995), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 99-NM-67-AD. Supersedes AD 95-16-02, amendment 39-9321.

Applicability: Model 747SP, SR, -100, -200, and -300 series airplanes equipped with Pratt & Whitney Model JT9D-3, -7, -7Q, and -7R4G2 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 (e)(1) 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:

Restatement of Requirements of AD 95-16-02

Operational Test

(a) Within 90 days after September 5, 1995 (the effective date of AD 95-16-02, amendment 39-9321), perform an operational test of the reversible gearbox pneumatic drive unit (PDU) or the reversing air motor PDU to ensure that the unit can restrain the thrust reverser sleeve, in accordance with Boeing Alert Service Bulletin 747-78A2131, dated September 15, 1994. Repeat the test thereafter at intervals not to exceed 2,000 flight hours until accomplishment of paragraph (c) of this AD.

Corrective Action

(b) If any of the tests required by paragraph (a) of this AD cannot be successfully performed, or if any discrepancy is found during those tests, accomplish either paragraph (b)(1) or (b)(2) of this AD.

(1) Prior to further flight, correct any discrepancy found, in accordance with Boeing Alert Service Bulletin 747-78A2131, dated September 15, 1994. Or

(2) The 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. Start Printed Page 4182

New Requirements of This AD

Modifications

(c) Within 36 months after the effective date of this AD, accomplish the requirements of paragraphs (c)(1), (c)(2), and (c)(3) of this AD. Accomplishment of the actions required by this paragraph constitutes terminating action for the repetitive tests required by paragraph (a) of this AD.

(1) Install an additional locking system on each thrust reverser in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-78-2152, Revision 1, dated December 12, 1996; Revision 2, dated December 18, 1997; or Revision 3, dated August 26, 1999.

(2) Remove the thrust reverser sequencing mechanism and install a solenoid operated shutoff valve in accordance with Boeing Service Bulletin 747-78-2052, Revision 5, dated February 22, 1996.

(3) Install provisional wiring for the additional locking system on the thrust reversers, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-78-2134, Revision 3, dated March 19, 1998.

Repetitive Tests

(d) Within 3,000 flight hours after accomplishment of paragraph (c) of this AD: Perform a functional test to detect discrepancies of the additional locking system on each thrust reverser in accordance with the procedures described in the Boeing 747 Airplane Maintenance Manual (AMM), Section 78-34-11, dated October 25, 1997. Prior to further flight, correct any discrepancy detected and repeat the functional test of that repair in accordance with the procedures described in the AMM. Repeat the functional tests thereafter at intervals not to exceed 3,000 flight hours.

Alternative Methods of Compliance

(e)(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 paragraphs (a) and (b) of AD 95-16-02, amendment 39-9321, are approved as alternative methods of compliance with the corresponding paragraphs in this AD.

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 Permits

(f) 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.

Start Signature

Issued in Renton, Washington, on January 20, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 00-1778 Filed 1-25-00; 8:45 am]

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