[Federal Register Volume 64, Number 248 (Tuesday, December 28, 1999)]
[Proposed Rules]
[Pages 72575-72579]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-33568]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-79-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-200 and -300 Series
Airplanes Equipped With General Electric CF6-80C2 Series Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to certain Boeing Model 747-
200 and -300 series airplanes, that currently requires various
inspections and functional tests to detect discrepancies of the thrust
reverser control and indication system, and correction of any
discrepancy found. This action would require installation of a
terminating modification, and would add repetitive functional tests of
that installation, 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 February 11, 2000.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-79-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: Dorr Anderson, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2684; 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
[[Page 72576]]
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-79-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-79-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On July 12, 1999, the FAA issued AD 99-15-08, amendment 39-11227
(64 FR 39003, July 21, 1999), applicable to certain Boeing Model 747-
200 and -300 series airplanes, to require various inspections and
functional tests to detect discrepancies of the thrust reverser control
and indication system, and correction of any discrepancy found. That AD
superseded, and retained certain requirements of AD 95-06-01, which was
prompted by reports indicating that several center drive units (CDU)
were returned to the manufacturer of the CDU's because of low holding
torque of the CDU cone brake. 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 could result in inadvertent deployment of
a thrust reverser during flight.
Actions Since Issuance of Previous Rule
In the preamble to AD 99-15-08, the FAA specified that the actions
required by that AD were considered ``interim action'' and that the
manufacturer was developing a modification to positively address the
unsafe condition. The FAA indicated that it may consider further
rulemaking action once the modification was developed, approved, and
available. The manufacturer now has developed such a modification, and
the FAA has determined that further rulemaking action is indeed
necessary; this proposed AD follows from that determination.
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 Boeing Service Bulletin 747-78-
2144, Revision 1, dated April 1, 1996, which describes procedures for
accomplishment of certain thrust reverser wiring modifications of the
wings, strut, and fuselage. Boeing Service Bulletin 747-78-2144
references the following service bulletins:
Lockheed Martin Service Bulletin 78-1007, Revision 1,
dated March 18, 1997, and Middle River Aircraft Systems Service
Bulletin 78-1007, Revision 2, dated March 10, 1998, which describe
procedures for adding an actuation system lock bracket and fastening
hardware to each thrust reverser; and
Lockheed Martin Service Bulletin 78-1020, Revision 2,
dated March 20, 1997, and Middle River Aircraft Systems Service
Bulletin 78-1020, Revision 3, dated March 16, 1998, which describe
procedures for installation of an actuation system lock (also called an
electro-mechanical lock or electro-mechanical brake) on each thrust
reverser.
Accomplishment of Boeing Service Bulletin 747-78-2144 requires
prior or concurrent accomplishment of Lockheed Martin Service Bulletin
78-1007, Revision 1, or Middle River Aircraft Systems Service Bulletin
78-1007, Revision 2; and Lockheed Martin Service Bulletin 78-1020,
Revision 2, or Middle River Aircraft Systems Service Bulletin 78-1020,
Revision 3.
The modification procedures described by Boeing Service Bulletins
747-78-2144 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 Bulletin 747-78-2144, Revision 1, 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 99-15-08 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 proposed AD would require installation of a
terminating modification, and would add repetitive functional tests of
that installation, and repair, if necessary. The actions would be
required to be accomplished in accordance with the service bulletins
described previously, except as discussed below.
Differences Between Service Bulletins and This Proposed AD
Operators should note that, although the service bulletins
described previously recommend no specific compliance time for
accomplishment of the actuation system lock installation, the FAA has
determined that an unspecified compliance time would not address the
identified unsafe condition
[[Page 72577]]
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 it represents an appropriate
interval of time allowable for affected airplanes to continue to
operate without compromising safety.
Operators also should note that this AD proposes to mandate, within
36 months, accomplishment of the actions specified for installation of
the actuation system lock as described in Lockheed Martin Service
Bulletin 78-1007, Revision 1; Middle River Aircraft Systems Service
Bulletin 78-1007, Revision 2; Lockheed Martin Service Bulletin 78-1020,
Revision 2; Middle River Aircraft Systems Bulletin 78-1020, Revision 3;
and Boeing Service Bulletin 747-78-2144, Revision 1; as terminating
action for the requirements of AD 99-15-08, and paragraph (b) of AD 95-
06-01. Following accomplishment of the installation, the FAA has
determined that repetitive functional tests of the CDU cone brake and
actuation system lock on each thrust reverser will support continued
operational safety of thrust reversers with actuation system locks.
Cost Impact
There are approximately 9 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 2 airplanes of U.S. registry
would be affected by this proposed AD.
The actions originally required by AD 95-06-01, and retained in
this proposed AD, take approximately 33 work hours 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 $3,960, or $1,980 per airplane, per
inspection/test cycle.
The other actions (repeating the functional test of the cone brake
required by AD 95-06-01 at reduced intervals) that are currently
required by AD 99-15-08, and retained in this proposed AD, would not
add any additional economic burden on affected operators.
The bracket installation proposed in this new AD would take
approximately 64 work hours per airplane to accomplish, 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 bracket installation proposed by this AD on U.S.
operators is estimated to be $7,680, or $3,840 per airplane.
The actuation system lock installation proposed in this new AD
would take approximately 16 work hours per airplane to accomplish, 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 lock installation proposed by
this AD on U.S. operators is estimated to be $1,920, or $960 per
airplane.
The functional test proposed in this new AD would take
approximately 2 work hours 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 $240, or $120 per airplane, per test cycle.
The wiring modifications proposed in this new AD would take
approximately 833 work hours per airplane to accomplish, 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 modifications proposed by this AD on U.S.
operators is estimated to be $99,960, or $49,980 per airplane.
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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
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 removing amendment 39-11227 (64 FR
39003, July 21, 1999), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 99-NM-79-AD. Supersedes AD 99-15-08, amendment 39-
11227.
Applicability: Model 747-200 and -300 series airplanes equipped
with General Electric Model CF6-80C2 series engines with Power
Management Control engine controls, 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 (h)(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:
[[Page 72578]]
Restatement of the Original Requirements of AD 95-06-01
Repetitive Tests and Inspections
(a) Within 90 days after April 13, 1995 (the effective date of
AD 95-06-01, amendment 39-9171), perform tests of the position
switch module and the cone brake of the center drive unit (CDU) on
each thrust reverser, and perform an inspection to detect damage to
the bullnose seal on the translating sleeve on each thrust reverser,
in accordance with paragraphs III.A. through III.C. of the
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
78A2130, dated May 26, 1994. Repeat the tests and inspection
thereafter at intervals not to exceed 1,000 hours time-in-service
until the functional test required by paragraph (d) of this AD is
accomplished.
(b) Within 9 months after April 13, 1995, perform inspections
and functional tests of the thrust reverser control and indication
system in accordance with paragraphs III.D. through III.F., III.H.,
and III.I. of the Accomplishment Instructions of Boeing Alert
Service Bulletin 747-78A2130, dated May 26, 1994. Repeat these
inspections and functional tests thereafter at intervals not to
exceed 18 months.
Corrective Action
(c) If any of the inspections and/or functional tests required
by paragraphs (a) and (b) of this AD cannot be successfully
performed, or if any discrepancy is found during those inspections
and/or functional tests, accomplish either paragraph (c)(1) or
(c)(2) of this AD.
(1) Prior to further flight, correct the discrepancy found, in
accordance with Boeing Alert Service Bulletin 747-78A2130, dated May
26, 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.
Restatement of Requirements of AD 99-15-08
Repetitive Tests/Terminating Action
(d) Within 1,000 hours time-in-service after the most recent
test of the CDU cone brake performed in accordance with paragraph
(a) of this AD, or within 650 hours time-in-service after August 25,
1999 (the effective date of AD 99-15-08, amendment 39-11227),
whichever occurs first: Perform a functional test to detect
discrepancies of the CDU cone brake on each thrust reverser, in
accordance with Boeing Service Bulletin 747-78A2166, Revision 1,
dated October 9, 1997, or paragraph III.B. of the Accomplishment
Instructions of Boeing Alert Service Bulletin 747-78A2130, dated May
26, 1994. Repeat the functional test thereafter at the interval
specified in paragraph (d)(1) or (d)(2) of this AD, as applicable.
Accomplishment of such functional test constitutes terminating
action for the repetitive test of the CDU cone brake required by
paragraph (a) of this AD; the position switch module tests and the
bullnose seal inspections continue to be required as specified in
paragraph (a) of this AD.
(1) For airplanes equipped with thrust reversers NOT modified in
accordance with Boeing Service Bulletin 747-78-2144, Revision 1,
dated April 11, 1996: Repeat the functional test at intervals not to
exceed 650 hours time-in-service.
(2) For airplanes equipped with thrust reversers modified in
accordance with Boeing Service Bulletin 747-78-2144, Revision 1,
dated April 11, 1996: Repeat the functional test at intervals not to
exceed 1,000 hours time-in-service.
Corrective Action
(e) If any functional test required by paragraph (d) of this AD
cannot be successfully performed, or if any discrepancy is found
during any functional test required by paragraph (d) of this AD,
accomplish either paragraph (e)(1) or (e)(2) of this AD.
(1) Prior to further flight, correct the discrepancy found, in
accordance with Boeing Service Bulletin 747-78A2166, Revision 1,
dated October 9, 1997, or paragraph III.B. of the Accomplishment
Instructions of Boeing Alert Service Bulletin 747-78A2130, dated May
26, 1994. Or
(2) The airplane may be operated in accordance with the
provisions and limitations specified in the operator's FAA-approved
MEL, provided that no more than one thrust reverser on the airplane
is inoperative.
New Requirements of This AD
Terminating Action
(f) Accomplish the requirements of paragraphs (f)(1) and (f)(2)
of this AD at the times specified in those paragraphs.
Accomplishment of the actions required by paragraph (f)(1) of this
AD constitutes terminating action for the requirements of paragraphs
(a), (b), (d), and (e) of this AD.
(1) Within 36 months after the effective date of this AD,
accomplish the requirements of paragraphs (f)(1)(i) and (f)(1)(ii)
of this AD.
(i) Install an actuation system lock bracket and fastening
hardware to each thrust reverser in accordance with the
Accomplishment Instructions of Lockheed Martin Service Bulletin 78-
1007, Revision 1, dated March 18, 1997, or Middle River Aircraft
Systems Service Bulletin 78-1007, Revision 2, dated March 10, 1998.
(ii) Install an actuation system lock (also called an electro-
mechanical lock or electro-mechanical brake) on each thrust reverser
in accordance with the Accomplishment Instructions of Lockheed
Martin Service Bulletin 78-1020, Revision 2, dated March 20, 1997,
or Middle River Aircraft Systems Service Bulletin 78-1020, Revision
3, dated March 16, 1998.
(2) Prior to or concurrent with the accomplishment of the
requirements of paragraph (f)(1) of this AD, perform the thrust
reverser wiring modifications of the wings, strut, and fuselage, in
accordance with the Accomplishment Instructions of Boeing Service
Bulletin 747-78-2144, Revision 1, dated April 11, 1996.
Repetitive Tests
(g) Within 1,000 hours time-in-service after accomplishment of
paragraph (f) of this AD, or within 1,000 hours time-in-service
after the effective date of this AD, whichever occurs later: Perform
a functional test to detect discrepancies of the CDU cone brake and
actuation system lock on each thrust reverser, in accordance with
Appendix 1 of this AD. Prior to further flight, correct any
discrepancy detected and repeat the functional test of that repair,
in accordance with the procedures described in the Boeing 747
Maintenance Manual. Repeat the functional tests thereafter at
intervals not to exceed 1,000 hours time-in-service.
Alternative Methods of Compliance
(h)(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 99-15-08, amendment 39-11227, are approved as
alternative methods of compliance with the corresponding
requirements specified 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
(i) 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.
Appendix 1--Thrust Reverser Electro-Mechanical Brake and CDU Cone Brake
Test
1. General
A. This procedure contains steps to do two checks:
(1) A check of the holding torque of the electro-mechanical
brake.
(2) A check of the holding torque of the CDU cone brake.
2. Electro-Mechanical Brake and CDU Cone Brake Torque Check
A. Prepare to do the checks:
(1) Open the fan cowl panels.
B. Do a check of the torque of the electro-mechanical brake:
(1) Do a check of the running torque of the thrust reverser
system:
(a) Manually extend the thrust reverser six inches and measure
the running torque.
(1) Make sure the torque is less than 10 pound-inches.
(2) Do a check of the electro-mechanical brake holding torque:
(a) Make sure the thrust reverser translating cowl is extended
at least one inch.
(b) Make sure the CDU lock handle is released.
(c) Pull down on the manual release handle on the electro-
mechanical brake until the handle fully engages the retaining clip.
Note: This will lock the electro-mechanical brake.
[[Page 72579]]
(d) With the manual drive lockout cover removed from the CDU,
install a \1/4\-inch extension tool and dial-type torque wrench into
the drive pad.
Note: You will need a 24-inch extension to provide adequate
clearance for the torque wrench.
(e) Apply 90 pound-inches of torque to the system.
(1) The electro-mechanical brake system is working correctly if
the torque is reached before you turn the wrench 450 degrees (1\1/4\
turns).
(2) If the flexshaft turns more than 450 degrees before you
reach the specified torque, you must replace the long flexshaft
between the CDU and the upper angle gearbox.
(3) If you do not get 90 pound-inches of torque, you must
replace the electro-mechanical brake.
(f) Release the torque by turning the wrench in the opposite
direction until you read zero pound-inches.
(1) If the wrench does not return to within 30 degrees of
initial starting point, you must replace the long flexshaft between
the CDU and upper angle gearbox.
(3) Fully retract the thrust reverser.
C. Do a check of the torque of the CDU cone brake:
(1) Pull up on the manual release handle to unlock the electro-
mechanical brake.
(2) Pull the manual brake release lever on the CDU to release
the cone brake.
Note: This will release the pre-load tension that may occur
during a stow cycle.
(3) Return the manual brake release lever to the locked position
to engage the cone brake.
(4) Remove the two bolts that hold the lockout plate to the CDU
and remove the lockout plate.
(5) Install a \1/4\-inch drive and a dial type torque wrench
into the CDU drive pad.
CAUTION: DO NOT USE MORE THAN 100 POUND-INCHES OF TORQUE WHEN
YOU DO THIS CHECK. EXCESSIVE TORQUE WILL DAMAGE THE CDU.
(6) Turn the torque wrench to try to manually extend the
translating cowl until you get at lease 15-pound inches.
Note: The cone brake prevents movement in the extend direction
only. If you try to measure the holding torque in the retract
direction, you will get a false reading.
(a) If the torque is less than 15-pound-inches, you must replace
the CDU.
D. Return the airplane to its usual condition:
(1) Re-install the lockout plate.
(2) Fully retract the thrust reverser (unless already
accomplished).
(3) Pull down on the manual release handle on the electro-
mechanical brake until the handle fully engages the retaining clip
(unless already accomplished).
Note: This will lock the electro-mechanical brake.
(4) Close the fan cowl panels.
Issued in Renton, Washington, on December 21, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-33568 Filed 12-27-99; 8:45 am]
BILLING CODE 4910-13-U
