[Federal Register Volume 64, Number 207 (Wednesday, October 27, 1999)]
[Proposed Rules]
[Pages 57802-57806]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-28084]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-64-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes equipped with General Electric Model CF6-45 or -50 series 
engines. This proposal would require repetitive inspections and tests 
of the thrust reverser control and indication system, and corrective 
actions, if necessary. This proposal would also require installation of 
a thrust reverser actuation system (TRAS) lock, repetitive functional 
tests of that installation, and repair, if necessary. Installation of 
the TRAS lock would terminate the repetitive inspections and certain 
tests. This proposal is prompted by the results of a safety review, 
which revealed that in-flight deployment of a thrust reverser could 
result in a significant reduction in airplane controllability. 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 December 13, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-64-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.

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.

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.

[[Page 57803]]

    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-64-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-64-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On May 26, 1991, a Boeing Model 767-300ER series airplane was 
involved in an accident as a result of an uncommanded in-flight 
deployment of a thrust reverser. Following that accident, a study was 
conducted to evaluate the potential effects of an uncommanded thrust 
reverser deployment throughout the flight regime of other Boeing 
airplane models, including the Boeing Model 747 series airplane 
equipped with General Electric Model CF6-45 or -50 series engines. The 
study included a re-evaluation of the thrust reverser control system 
fault analysis and airplane controllability. The results of the 
evaluation revealed that, if not prevented, possible combinations of 
failures within the thrust reverser control system may result in an in-
flight deployment of a thrust reverser and that, in the event of thrust 
reverser deployment during high-speed climb using high engine power, or 
during cruise, these airplanes may not be controllable.
    The FAA has prioritized the issuance of AD's for corrective actions 
for the thrust reverser system on Boeing airplane models following the 
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 that correct the same type of unsafe condition as that 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 in 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 throughout the 
operating envelope of the airplane following such a deployment. 
Additionally, safety analyses performed by the manufacturer and 
reviewed by the FAA, have been unable to establish that the risks for 
uncommanded thrust reverser deployment at critical flight conditions 
are acceptably low.

Explanation of Relevant Service Information

    The FAA has reviewed and approved the following service bulletins:
     Boeing Alert Service Bulletin 747-78A2160, dated May 4, 
1995, including Notice of Status Change 747-78A2160 NSC 1, dated June 
8, 1995, describes procedures for repetitive inspections and tests to 
verify proper operation of the thrust reverser stow/deploy switches, 
the bullnose seals, the airmotor brake, the overpressure shutoff valve 
electrical connectors, the flexible shafts, the directional pilot 
valve, and the microswitch pack on each engine; and repair, if 
necessary.
     Boeing Service Bulletin 747-78-2150, Revision 1, dated 
July 2, 1998, describes procedures for installation of a thrust 
reverser actuation system (TRAS) lock on each thrust reverser half of 
each engine. This service bulletin specifies that prior or concurrent 
incorporation of Boeing Service Bulletin 747-78-2067, Boeing Service 
Bulletin 747-78-2069, Boeing Service Bulletin 747-78-2133, Middle River 
Aircraft Systems CF6-50 Service Bulletin 78-3011, and Middle River 
Aircraft Systems CF6-50 Service Bulletin 78-3013, is necessary. Such 
installation eliminates the need for the repetitive inspections and 
tests described in Boeing Alert Service Bulletin 747-78A2160.
    The FAA has also reviewed Chapter 78-34-00 of the Boeing 747 
Maintenance Manual, dated April 25, 1998, which describes procedures 
for repetitive functional tests of the TRAS lock.
    Accomplishment of the modification specified in Boeing Service 
Bulletin 747-78-2150, Revision 1, and the repetitive functional tests 
specified in the maintenance manual are intended to adequately address 
the identified unsafe condition.
    The modification procedures described by Boeing Service Bulletin 
747-78-2150, dated March 20, 1997, have been validated previously, and 
the necessary changes have been incorporated into Revision 1 of the 
service bulletin. The FAA has determined that the procedures described 
by Boeing Service Bulletin 747-78-2150, Revision 1, and the numerous 
referenced service bulletins, have been sufficiently validated to now 
propose that this modification be required. Several airplanes have been 
successfully modified in accordance with the service bulletin, 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 require repetitive inspections and tests of the 
thrust reverser control and indication system, and corrective actions, 
if necessary. The proposed AD would also require installation of a TRAS 
lock, repetitive functional tests of that installation, and repair, if 
necessary. Installation of the TRAS lock would terminate the repetitive 
inspections and certain tests.
    This proposed AD would also include a provision for deactivation of 
one thrust reverser in accordance with Section 78-1 of Boeing Document 
D6-33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures 
Guide,'' Revision 22, dated January 30, 1998. No more than one thrust 
reverser on any airplane may be deactivated under the provisions of 
this document.

Differences Between Proposed Rule and Service Bulletins

    The effectivity of Boeing Alert Service Bulletin 747-78A2160 
identifies all Model 747-100 and -200 series airplanes powered by 
General Electric Model CF6-45 or -50 series engines, line numbers 232 
through 886 inclusive; however, this proposed AD would apply to all 
Model 747 series airplanes powered by General Electric Model CF6-45 or 
-50 series engines. The FAA has been notified by the airplane

[[Page 57804]]

manufacturer that there are Model 747-300 and 747SR series airplanes, 
and airplanes having line numbers lower than 232, that are powered by 
Model CF6-45 or -50 series engines.
    Operators should note that, although Boeing Alert Service Bulletin 
747-78A2160 recommends accomplishing the inspections and tests within 
1,500 flight hours or 4 months (after the release of the service 
bulletin), the FAA has determined that the recommended interval 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 inspection. In light of all of these factors, the FAA finds 
a 90-day compliance time for initiating the inspections and tests of 
the thrust reverser stow/deploy switches, the bullnose seals, and the 
airmotor brakes; and a 6-month compliance time for initiating the 
inspections and tests of the overpressure shutoff valve electrical 
connectors, the flexible shafts, the directional pilot valves, and the 
microswitch packs; to be warranted, in that those times represent 
appropriate intervals of time allowable for affected airplanes to 
continue to operate without compromising safety.
    Operators should also note that, although Boeing Service Bulletin 
747-78-2150, Revision 1, does not specify a compliance time for 
accomplishment of installation of the TRAS locks, this proposal would 
require that action to be accomplished within 36 months after the 
effective date of this AD. In developing an appropriate compliance time 
for this proposed AD, the FAA considered the degree of urgency 
associated with addressing the subject unsafe condition, the average 
utilization of the affected fleet, and the time necessary to accomplish 
the proposed actions (approximately 791 work hours).
    In light of these factors, the FAA finds a compliance time of 36 
months for accomplishing the proposed actions to be warranted, in that 
it represents an appropriate interval of time allowable for affected 
airplanes to continue to operate without compromising safety.
    Although not described in either service bulletin, this proposed AD 
would allow the option to dispatch an airplane with one thrust reverser 
deactivated and operate the airplane for up to 10 days with one thrust 
reverser deactivated. This option would be allowed in the event of 
unsuccessful accomplishment of the repetitive inspections and tests 
specified in paragraphs (a) and (b) of this AD or installation of a 
spare thrust reverser assembly with a different configuration than that 
installed on the other engines of the airplane.

Cost Impact

    There are approximately 138 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 27 airplanes of U.S. registry 
would be affected by this proposed AD.
    It would take approximately 12 work hours per airplane to 
accomplish the proposed inspections and tests of the thrust reverser 
stow/deploy switches, the bullnose seals, and the airmotor brakes, at 
an average labor rate of $60 per work hour. Based on these figures, the 
cost impact of the proposed repetitive inspections and tests on U.S. 
operators is estimated to be $19,440, or $720 per airplane, per 
inspection and test cycle.
    It would take approximately 11 work hours per airplane to 
accomplish the proposed inspections and tests of the overpressure 
shutoff valve electrical connectors, the flexible shafts, the 
directional pilot valves, and the microswitch packs, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the proposed repetitive inspections and tests on U.S. 
operators is estimated to be $17,820, or $660 per airplane, per 
inspection and test cycle.
    It would take approximately 791 work hours per airplane to 
accomplish the proposed installation of TRAS locks, at an average labor 
rate of $60 per work hour. Required parts would be provided at no cost 
by the airplane manufacturer. Based on these figures, the cost impact 
of the proposed installation on U.S. operators is estimated to be 
$1,281,420, or $47,460 per airplane.
    This cost impact figure does not reflect the cost of the 
modifications described in the service bulletins listed in paragraph 
I.K.1.h. of Boeing Service Bulletin 747-78-2150, Revision 1, that are 
proposed to be accomplished prior to, or concurrently with, the 
installation of the TRAS lock. (The cost impact figure does reflect the 
cost of the modifications described in the service bulletins listed in 
paragraph I.K.1.j. of the service bulletin that are also proposed to be 
accomplished prior to, or concurrently with, the installation of the 
TRAS lock.) Since some operators may have accomplished certain 
modifications on some or all of the airplanes in its fleet, while other 
operators may not have accomplished any of the modifications on any of 
the airplanes in its fleet, the FAA is unable to provide a reasonable 
estimate of the cost of accomplishing the terminating actions described 
in the service bulletins listed in paragraph I.K.1.h. of Boeing Service 
Bulletin 747-78-2150. As indicated earlier in this preamble, the FAA 
invites comments specifically on the overall economic aspects of this 
proposed rule. Any data received via public comments to this proposed 
AD will aid the FAA in developing an accurate accounting of the cost 
impact of the rule.
    It would take approximately 4 work hours per airplane to accomplish 
the proposed functional test of the TRAS lock, at an average labor rate 
of $60 per work hour. Based on these figures, the cost impact of the 
proposed repetitive functional tests on U.S. operators is estimated to 
be $6,480, or $240 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 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.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

[[Page 57805]]

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:

PART 39--AIRWORTHINESS 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 adding the following new 
airworthiness directive:

Boeing: Docket 99-NM-64-AD.
    Applicability: Model 747 series airplanes; certificated in any 
category; equipped with General Electric Model CF6-45 or -50 series 
engines.

    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 (h) 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 Inspections and Tests

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (a) Within 90 days after the effective date of this AD, perform 
the applicable detailed visual inspections and tests to verify 
proper operation of the thrust reverser stow/deploy switches, the 
bullnose seals, and the airmotor brake on each engine, in accordance 
with Work Package I of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 747-78A2160, dated May 4, 1995, including 
Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995. 
Repeat the applicable inspections and tests thereafter at intervals 
not to exceed 1,300 flight hours, until accomplishment of paragraph 
(d) of this AD.
    (b) Within 6 months after the effective date of this AD, perform 
the applicable detailed visual inspections and tests to verify 
proper operation of the overpressure shutoff valve electrical 
connectors, the flexible shafts, the directional pilot valve, and 
the microswitch pack on each engine, in accordance with Work Package 
II of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status 
Change 747-78A2160 NSC 1, dated June 8, 1995. Repeat the applicable 
inspections and tests thereafter at intervals not to exceed 18 
months, until accomplishment of paragraph (d) of this AD.

Corrective Actions

    (c) If any of the inspections and tests required by paragraphs 
(a) and (b) of this AD cannot be successfully performed, or if any 
discrepancy is detected during the inspections and tests, accomplish 
paragraphs (c)(1) or (c)(2) of this AD, as applicable.
    (1) Prior to further flight, repair in accordance with Boeing 
Alert Service Bulletin 747-78A2160, dated May 4, 1995. Additionally, 
prior to further flight, any failed inspection or test required by 
paragraph (a) or (b) of this AD must be repeated and successfully 
accomplished.
    (2) Accomplish both paragraphs (c)(2)(i) and (c)(2)(ii) of this 
AD.
    (i) Prior to further flight, deactivate the associated thrust 
reverser in accordance with Section 78-1 of Boeing Document D6-
33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures 
Guide,'' Revision 22, dated January 30, 1998. No more than one 
thrust reverser on any airplane may be deactivated under the 
provisions of this paragraph.

    Note 3: The airplane may be operated in accordance with the 
provisions and limitations specified in the operator's FAA-approved 
Master Minimum Equipment List, provided that no more than one thrust 
reverser on the airplane is inoperative.
    (ii) Within 10 days after deactivation of any thrust reverser in 
accordance with paragraph (c)(2)(i) of this AD, the affected thrust 
reverser must be repaired in accordance with Boeing Alert Service 
Bulletin 747-78A2160, dated May 4, 1995. Additionally, prior to 
further flight, any failed inspection or test required by paragraph 
(a) or (b) of this AD must be repeated and successfully 
accomplished; once such inspections and tests have been successfully 
accomplished, the thrust reverser may then be reactivated.

Modification

    (d) Within 36 months after the effective date of this AD, 
install a thrust reverser actuation system (TRAS) lock on each 
thrust reverser half of each engine, in accordance with Boeing 
Service Bulletin 747-78-2150, Revision 1, dated July 2, 1998. All of 
the modifications described in the service bulletins listed in 
paragraphs I.K.1.h. and I.K.1.j. of Boeing Service Bulletin 747-78-
2150, Revision 1, must be accomplished, as applicable, in accordance 
with those service bulletins, prior to, or concurrently with, the 
accomplishment of the installation of the TRAS lock. Accomplishment 
of these actions constitutes terminating action for the repetitive 
inspections required by paragraphs (a) and (b) of this AD.

    Note 4: Accomplishment of the installation specified in Boeing 
Service Bulletin 747-78-2150, dated March 20, 1997, is acceptable 
for compliance with the installation required by paragraph (d) of 
this AD.

Functional Tests

    (e) Within 3,000 flight hours after accomplishing the 
modification required by paragraph (d) of this AD, or within 1,000 
flight hours after the effective date of this AD, whichever occurs 
later, perform a functional test of the TRAS lock on each reverser 
half, in accordance with Chapter 78-34-00 of the Boeing 747 
Maintenance Manual, dated April 25, 1998.

Correction Actions

    (1) If no discrepancy is detected, repeat the functional test 
thereafter at intervals not to exceed 3,000 flight hours.
    (2) If any discrepancy is detected, prior to further flight, 
repair in accordance with the procedures specified in the Boeing 747 
Maintenance Manual. Additionally, prior to further flight, the 
functional test must be successfully accomplished. Repeat the 
functional test thereafter at intervals not to exceed 3,000 flight 
hours.

Spares

    (f) If, after incorporation of the modification required by 
paragraph (d) of this AD on any airplane, it becomes necessary to 
install a thrust reverser assembly that does not have the TRAS locks 
installed, dispatch of the airplane is allowed in accordance with 
the provisions and limitations specified in the operator's FAA-
approved Master Minimum Equipment List, provided that the thrust 
reverser assembly that does not have the TRAS locks installed is 
deactivated in accordance with Section 78-1 of Boeing Document D6-
33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures 
Guide,'' Revision 22, dated January 30, 1998. No more than one 
thrust reverser on any airplane may be deactivated under the 
provisions of this paragraph. Within 10 days after deactivation of 
the thrust reverser, install a thrust reverser assembly that has the 
TRAS locks installed and reactivate the thrust reverser.
    (g) If, prior to incorporation of the modification required by 
paragraph (d) of this AD on any airplane, it becomes necessary to 
install a thrust reverser assembly that has the TRAS locks 
installed, dispatch of the airplane is allowed in accordance with 
the provisions and limitations specified in the operator's FAA-
approved Master Minimum Equipment List, provided that the thrust 
reverser assembly that has the TRAS locks installed is deactivated 
in accordance with Section 78-1 of Boeing Document D6-33391, 
``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures 
Guide,'' Revision 22, dated January 30, 1998. No more than one 
thrust reverser on any airplane may

[[Page 57806]]

be deactivated under the provisions of this paragraph. Within 10 
days after deactivation of the thrust reverser, install a thrust 
reverser assembly that does not have the TRAS locks installed and 
reactivate the thrust reverser.

Alternative Methods of Compliance

    (h) 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 5: 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

    (i) Special flight permits may be issued in accordance with 
Sec. Sec. 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.

    Issued in Renton, Washington, on October 21, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-28084 Filed 10-26-99; 8:45 am]
BILLING CODE 4910-13-P