[Federal Register Volume 88, Number 85 (Wednesday, May 3, 2023)]
[Proposed Rules]
[Pages 27725-27734]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-09436]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-0921; Project Identifier AD-2022-01430-T]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD) 
2022-05-04, which applies to all The Boeing Company Model 737-100, -
200, -200C, -300, -400, -500, -600, -700, -700C, -800, -900, and -900ER 
series airplanes, except for Model 737-200 and -200C series airplanes 
equipped with a certain flight control system. AD 2022-05-04 requires 
revising the limitations and operating procedures sections of the 
existing airplane flight manual (AFM) to incorporate specific operating 
procedures for instrument landing system (ILS) approaches, speedbrake 
deployment, go-arounds, and missed approaches, when in the presence of 
5G C-Band interference as identified by Notices to Air Missions 
(NOTAMs). Since the FAA issued AD 2022-05-04, the FAA determined that 
additional limitations are needed due to the continued deployment of 
new 5G C-Band base stations whose signals are expected to cover most of 
the contiguous United States at transmission frequencies between 3.7-
3.98 GHz. This proposed AD would require revising the limitations and 
operating procedures sections of the

[[Page 27726]]

existing AFM to incorporate specific operating procedures for ILS 
approaches, speedbrake deployment, go-arounds, and missed approaches, 
due to the presence of 5G C-Band interference. The FAA is proposing 
this AD to address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by May 23, 
2023.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to regulations.gov. Follow 
the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2023-0921; or in person at Docket Operations between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD 
docket contains this NPRM, any comments received, and other 
information. The street address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Brett Portwood, Continued Operational 
Safety Technical Advisor, COS Program Management Section, Operational 
Safety Branch, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; 
phone: 817-222-5390; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2023-0921; Project Identifier 
AD-2022-01430-T'' at the beginning of your comments. The most helpful 
comments reference a specific portion of the proposal, explain the 
reason for any recommended change, and include supporting data. The FAA 
will consider all comments received by the closing date and may amend 
the proposal because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
regulations.gov, including any personal information you provide. The 
agency will also post a report summarizing each substantive verbal 
contact received about this proposed AD.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this NPRM contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this NPRM, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this NPRM. Submissions containing CBI should be sent to Brett 
Portwood, Continued Operational Safety Technical Advisor, COS Program 
Management Section, Operational Safety Branch, FAA, 3960 Paramount 
Boulevard, Lakewood, CA 90712-4137; phone: 817-222-5390; email: 
[email protected]. Any commentary that the FAA receives that is 
not specifically designated as CBI will be placed in the public docket 
for this rulemaking.

Background

    The FAA issued AD 2021-23-12, Amendment 39-21810 (86 FR 69984, 
December 9, 2021) (AD 2021-23-12), for all transport and commuter 
category airplanes equipped with a radio altimeter. AD 2021-23-12 was 
prompted by a determination that radio altimeters cannot be relied upon 
to perform their intended function if they experience interference from 
wireless broadband operations in the 3.7-3.98 GHz frequency band (5G C-
Band). AD 2021-23-12 requires revising the limitations section of the 
existing AFM to incorporate limitations prohibiting certain operations 
requiring radio altimeter data when in the presence of 5G C-Band 
interference as identified by NOTAMs. The agency issued AD 2021-23-12 
because radio altimeter anomalies that are undetected by the automation 
or pilot, particularly close to the ground (e.g., landing flare), could 
lead to loss of continued safe flight and landing.
    The FAA subsequently identified an additional hazard presented by 
5G C-Band interference on The Boeing Company Model 737-100, -200, -
200C, -300, -400, -500, -600, -700, -700C, -800, -900, and -900ER 
series airplanes, except for Model 737-200 and -200C series airplanes 
equipped with a certain flight control system, and issued AD 2022-05-
04, Amendment 39-21955 (87 FR 10299, February 24, 2022) (AD 2022-05-
04). AD 2022-05-04 was prompted by a determination that, during 
approach, landings, and go-arounds, as a result of 5G C-Band 
interference, certain airplane systems may not properly function, 
resulting in increased flightcrew workload while on approach with the 
flight director, autothrottle, or autopilot engaged. AD 2022-05-04 
requires revising the limitations and operating procedures sections of 
the existing AFM to incorporate specific operating procedures for ILS 
approaches, speedbrake deployment, go-arounds, and missed approaches, 
when in the presence of 5G C-Band interference as identified by NOTAMs. 
The agency issued AD 2022-05-04 to address 5G C-Band interference that 
could result in increased flightcrew workload and could lead to reduced 
ability of the flightcrew to maintain safe flight and landing of the 
airplane.

Actions Since AD 2022-05-04 Was Issued

    Since issuing AD 2022-05-04, the FAA determined that additional 
limitations are needed due to the continued deployment of new 5G C-Band 
base stations whose signals are expected to cover most of the 
contiguous United States at transmission frequencies between 3.7-3.98 
GHz. Therefore, the FAA issued an NPRM, Docket No. FAA-2022-1647 (88 FR 
1520, January 11, 2023) (the NPRM), proposing to supersede AD 2021-23-
12. In the NPRM, the FAA proposed to retain most of the operational 
prohibitions required by AD 2021-23-12 until June 30, 2023; on or 
before June 30, 2023, operators would be required to revise their 
existing AFM to prohibit these operations unless the airplane has a 
radio altimeter meeting proposed minimum performance levels (a defined 
power spectral density (PSD) curve as well as a defined aggregate 
spurious emission level) and is operating at a 5G C-Band mitigated 
airport (5G CMA). In the NPRM, the FAA also proposed to require all 
airplanes operating under 14 CFR part 121 to have a radio altimeter 
meeting the proposed minimum performance standards by February 1, 2024.
    Since the NPRM was published, the FAA has determined that a PSD 
curve is a more appropriate method to define

[[Page 27727]]

performance than a single fixed emission level. The proposed PSD curve 
more accurately reflects differences in radio altimeter susceptibility 
to interfering emissions at different altitude levels. The FAA plans to 
issue guidance on how to show compliance with both the fundamental PSD 
curve and spurious PSD curve, including the data to be submitted, for 
the FAA to approve the method used.
    2022-05-04 relies on the FAA's use of NOTAMs to identify 5G C-band 
interference at certain airports in the U.S. airspace. As explained in 
more detail in the NPRM, those NOTAMs are no longer the best means of 
communicating the location of the 5G C-Band environment. Therefore, 
this proposed AD would retain the AFM limitations and operating 
procedures required by AD 2022-05-04 until June 30, 2023. On or before 
June 30, 2023, this proposed AD would require operators to replace the 
limitations with limitations prohibiting the same operations, except 
the prohibitions would not be tied to NOTAMs but instead would depend 
on whether the airplane is operated at a 5G CMA as identified by an FAA 
Domestic Notice. Because the 5G C-Band Interference operating procedure 
required by AD 2022-05-04 references AD 2021-23-12 for certain 
prohibited ILS approaches, this proposed AD would require operators to 
replace the procedure with an operating procedure containing the same 
information, except it would list the specific prohibited ILS 
approaches.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or develop on other 
products of the same type design.

Proposed AD Requirements in This NPRM

    This proposed AD would retain the AFM revisions required by AD 
2022-05-04 until June 30, 2023. On or before June 30, 2023, this 
proposed AD would require replacing those AFM revisions with 
limitations requiring the same procedures for dispatch or release to 
airports, and approach, landing, and go-around on runways, at all 
airports for non-radio altimeter tolerant airplanes. For radio 
altimeter tolerant airplanes, the procedures would not be required at 
5G CMAs as identified in an FAA Domestic Notice. The minimum 
performance levels in this proposed AD for determining whether an 
airplane is radio altimeter tolerant are the same minimum performance 
levels proposed in the NPRM, except the FAA has replaced the proposed 
fixed emission level with a proposed PSD curve emission threshold that 
more accurately reflects differences in radio altimeter susceptibility 
to interfering emissions at different altitude levels.
    Paragraph (l)(3) of this proposed AD specifies that AMOCs approved 
for AD 2021-23-12 providing relief for specific radio altimeter 
installations would be approved as AMOCs for the requirements specified 
in paragraph (h) of this proposed AD until June 30, 2023.

Interim Action

    The FAA considers that this AD, if adopted as proposed, would be an 
interim action. Once the Technical Standard Order (TSO) standard for 
radio altimeters is established, which will follow the existing 
international technical consensus on the establishment of the minimum 
operational performance standards (MOPS), the FAA anticipates that the 
MOPS will be incorporated into the TSO. The FAA also anticipates that 
aircraft incorporating equipment approved under the new Radio Altimeter 
TSO will be able to operate in both 5G CMAs and non-5G CMAs with no 5G 
C-Band-related AFM limitations. Once a new radio altimeter TSO is 
developed, approved, and available, the FAA might consider additional 
rulemaking.

Costs of Compliance

    The cost information below describes the costs to change the AFM. 
Although this proposed AD would largely maintain the AFM limitations 
currently required by AD 2022-05-04, the FAA acknowledges that this 
proposed AD may also impose costs on some aircraft operators from 
having to change their conduct to comply with the amended AFM. However, 
the FAA lacks the data necessary to quantify the costs associated with 
aircraft operators changing their conduct. The FAA is seeking public 
comment on these costs so the agency can more fully account for the 
impact of this regulatory action.
    The FAA estimates that this AD, if adopted as proposed, would 
affect 2,328 airplanes of U.S. registry.\1\ The FAA estimates the 
following costs to comply with this proposed AD:
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    \1\ This is the number of affected Boeing Model 737-100, -200, -
200C, -300, -400, -500, -600, -700, -700C, -800, -900, and -900ER 
series airplanes on the FAA's registry as of December 1, 2022.
    \2\ The labor rate of $85 per hour is the average wage rate for 
an aviation mechanic.
    \3\ The estimated cost for this revision would not constitute a 
significant economic impact (even for small entities) because $85 is 
a minimal cost compared to the regular costs of maintaining and 
operating a Model 737-100, -200, -200C, -300, -400, -500, -600, -
700, -700C, -800, -900, or -900ER transport category airplane.

                                                 Estimated Costs
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                                                                                    Cost per       Cost on U.S.
               Action                        Labor cost           Parts cost        product         operators
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AFM revision (retained actions from   1 work-hour x $85 per                $0              $85         $197,880
 AD 2022-05-04).                       hour \2\ = $85.
New AFM revisions (new proposed       1 work-hour x $85 per                 0               85      \3\ 197,880
 action).                              hour = $85.
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Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

[[Page 27728]]

Regulatory Findings

    The FAA has determined that this proposed AD would not have 
federalism implications under Executive Order 13132. This proposed AD 
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.
    For the reasons discussed above, I certify that the proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and
    (3) Would not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The FAA amends Sec.  39.13 by:
0
a. Removing Airworthiness Directive (AD) 2022-05-04, Amendment 39-21955 
(87 FR 10299, February 24, 2022), and
0
b. Adding the following new AD:

The Boeing Company Airplanes: Docket No. FAA-2023-0921; Project 
Identifier AD-2022-01430-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by May 23, 2023.

(b) Affected ADs

    This AD replaces AD 2022-05-04, Amendment 39-21955 (87 FR 10299, 
February 24, 2022) (AD 2022-05-04).

(c) Applicability

    This AD applies to all The Boeing Company 737-100, -200, -200C, 
-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series 
airplanes, certificated in any category, except for Model 737-200 
and -200C series airplanes equipped with an SP-77 flight control 
system.

(d) Subject

    Air Transport Association (ATA) of America Code 34, Navigation.

(e) Unsafe Condition

    This AD was prompted by a determination that radio altimeters 
cannot be relied upon to perform their intended function if they 
experience interference from wireless broadband operations in the 
3.7-3.98 GHz frequency band (5G C-Band), and a determination that, 
during approach, landings, and go-arounds, as a result of this 
interference, certain airplane systems may not properly function, 
resulting in increased flightcrew workload while on approach with 
the flight director, autothrottle, or autopilot engaged. The FAA is 
issuing this AD to address 5G C-Band interference that could result 
in increased flightcrew workload and could lead to reduced ability 
of the flightcrew to maintain safe flight and landing of the 
airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Definitions

    (1) For purposes of this AD, a ``5G C-Band mitigated airport'' 
(5G CMA) is an airport at which the telecommunications companies 
have agreed to voluntarily limit their 5G deployment at the request 
of the FAA, as identified by an FAA Domestic Notice.
    (2) For purposes of this AD, a ``radio altimeter tolerant 
airplane'' is one for which the radio altimeter, as installed, 
demonstrates the tolerances specified in paragraphs (g)(2)(i) and 
(ii) of this AD, using a method approved by the FAA.
    (i) Tolerance to radio altimeter interference, for the 
fundamental emissions (3.7-3.98 GHz), at or above the power spectral 
density (PSD) curve threshold specified in figure 1 to paragraph 
(g)(2)(i) of this AD.

Figure 1 to paragraph (g)(2)(i)--Fundamental Effective Isotropic PSD 
at Outside Interface of Aircraft Antenna

[[Page 27729]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.088

    (ii) Tolerance to radio altimeter interference, for the spurious 
emissions (4.2-4.4 GHz), at or above the PSD curve threshold 
specified in figure 2 to paragraph (g)(2)(ii) of this AD.

Figure 2 to paragraph (g)(2)(ii)--Spurious Effective Isotropic PSD 
at Outside Interface of Aircraft Antenna

[[Page 27730]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.089

    (3) For purposes of this AD, a ``non-radio altimeter tolerant 
airplane'' is one for which the radio altimeter, as installed, does 
not demonstrate the tolerances specified in paragraphs (g)(2)(i) and 
(ii) of this AD.

(h) Retained Airplane Flight Manual (AFM) Revision

    This paragraph restates the requirements of paragraph (g) of AD 
2022-05-04.
    (1) Within 2 days after February 24, 2022 (the effective date of 
AD 2022-05-04): Revise the Limitations Section of the existing AFM 
to include the information specified in figure 3 to paragraph (h)(1) 
of this AD. This may be done by inserting a copy of figure 3 to 
paragraph (h)(1) of this AD into the existing AFM.

Figure 3 to paragraph (h)(1)--AFM Limitations Revisions

[[Page 27731]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.090

    (2) Within 2 days after February 24, 2022 (the effective date of 
AD 2022-05-04): Revise the Operating Procedures Section of the 
existing AFM to include the information specified in figure 4 to 
paragraph (h)(2) of this AD or figure 5 to paragraph (h)(2) of this 
AD, as applicable. This may be done by inserting a copy of figure 4 
to paragraph (h)(2) or figure 5 to paragraph (h)(2) of this AD, as 
applicable, into the Operating Procedures Section of the existing 
AFM.

Figure 4 to paragraph (h)(2)--AFM Operating Procedures Revision for 
Model 737-100, -200, -200C, -300, -400, and -500 series airplanes
[GRAPHIC] [TIFF OMITTED] TP03MY23.091

Figure 5 to paragraph (h)(2)--AFM Operating Procedures Revision for 
Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes

[[Page 27732]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.092

(i) New Requirement: AFM Limitations Revision for Non-Radio Altimeter 
Tolerant Airplanes

    For non-radio altimeter tolerant airplanes, do the actions 
specified in paragraphs (i)(1) and (2) of this AD.
    (1) On or before June 30, 2023, revise the Limitations Section 
of the existing AFM to include the information specified in figure 6 
to paragraph (i) of this AD. This may be done by inserting a copy of 
figure 6 to paragraph (i) of this AD into the existing AFM. 
Incorporating the AFM revision required by this paragraph terminates 
the AFM revision required by paragraph (h)(1) of this AD.
    (2) Before further flight after incorporating the limitations 
specified in figure 6 to paragraph (i) of this AD, remove the AFM 
revision required by paragraph (h)(1) of this AD.

Figure 6 to paragraph (i)--AFM Limitations Revision for Non-Radio 
Altimeter Tolerant Airplanes
[GRAPHIC] [TIFF OMITTED] TP03MY23.093

(j) New Requirement: AFM Limitations Revision for Radio Altimeter 
Tolerant Airplanes

    For radio altimeter tolerant airplanes, do the actions specified 
in paragraphs (j)(1) and (2) of this AD.
    (1) On or before June 30, 2023, revise the Limitations Section 
of the existing AFM to include the information specified in figure 7 
to paragraph (j) of this AD. This may be done by inserting a copy of 
figure 7 to paragraph (j) of this AD into the existing AFM. 
Incorporating the AFM revision required by this paragraph terminates 
the AFM revision required by paragraph (h)(1) of this AD.
    (2) Before further flight after incorporating the limitations 
specified in figure 7 to paragraph (j) of this AD, remove the AFM 
revision required by paragraph (h)(1) of this AD.

Figure 7 to paragraph (j)--AFM Limitations Revision for Radio 
Altimeter Tolerant Airplanes

[[Page 27733]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.094

(k) New Requirement: AFM Operating Procedures Revision

    For all airplanes, do the actions specified in paragraphs (k)(1) 
and (2) of this AD.
    (1) On or before June 30, 2023, revise the Operating Procedures 
Section of the existing AFM to include the information specified in 
figure 8 to paragraph (k) of this AD or figure 9 to paragraph (k) of 
this AD, as applicable. This may be done by inserting a copy of 
figure 8 to paragraph (k) of this AD or figure 9 to paragraph (k) of 
this AD, as applicable, into the Operating Procedures Section of the 
existing AFM. Incorporating the AFM revision required by this 
paragraph terminates the AFM revision required by paragraph (h)(2) 
of this AD.
    (2) Before further flight after incorporating the operating 
procedures specified in figure 8 to paragraph (k) of this AD or 
figure 9 to paragraph (k) of this AD, remove the AFM revision 
required by paragraph (h)(2) of this AD.

Figure 8 to paragraph (k)--AFM Operating Procedures Revision for 
Model 737-100, -200, -200C, -300, -400, and -500 series airplanes
[GRAPHIC] [TIFF OMITTED] TP03MY23.095

Figure 9 to paragraph (k)--AFM Operating Procedures Revision for 
Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes

[[Page 27734]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.096

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Operational Safety Branch, FAA, has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, 
send your request to your principal inspector or responsible Flight 
Standards Office, as appropriate. If sending information directly to 
the manager of the Operational Safety Branch, send it to the 
attention of the person identified in paragraph (m) of this AD. 
Information may be emailed to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.
    (3) AMOCs approved for AD 2021-23-12, Amendment 39-21810 (86 FR 
69984, December 9, 2021) providing relief for specific radio 
altimeter installations are approved as AMOCs for the requirements 
specified in paragraph (h) of this AD until June 30, 2023.

(m) Related Information

    For more information about this AD, contact Brett Portwood, 
Continued Operational Safety Technical Advisor, COS Program 
Management Section, Operational Safety Branch, FAA, 3960 Paramount 
Boulevard, Lakewood, CA 90712-4137; phone: 817-222-5390; email: 
[email protected].

(m) Material Incorporated by Reference

    None.

    Issued on April 28, 2023.
Michael Linegang,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-09436 Filed 5-1-23; 4:15 pm]
BILLING CODE 4910-13-C