[Federal Register Volume 88, Number 85 (Wednesday, May 3, 2023)]
[Proposed Rules]
[Pages 27786-27799]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-09434]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-0671; Project Identifier AD-2022-01428-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) 
2022-03-20, which applies to all The Boeing Company Model 737-8, 737-9, 
and 737-8200 airplanes. AD 2022-03-20 requires revising the limitations 
and operating procedures sections of the existing airplane flight 
manual (AFM) to incorporate limitations prohibiting the use of certain 
minimum equipment list (MEL) items, and to incorporate operating 
procedures for calculating takeoff and landing distances, when in the 
presence of 5G C-Band interference as identified by Notices to Air 
Missions (NOTAMs). Since the FAA issued AD 2022-03-20, 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 section of the existing AFM to incorporate limitations 
prohibiting the use of certain MEL items, and would retain the 
operating procedures from AD 2022-03-20 for calculating takeoff and 
landing distances, 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-2023-0671; 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;

[[Page 27787]]

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-2023-0671; Project Identifier 
AD-2022-01428-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 737-8, 737-9, and 
737-8200 airplanes and issued AD 2022-03-20, Amendment 39-21937 (87 FR 
4787, January 31, 2022) (AD 2022-03-20). AD 2022-03-20 was prompted by 
a determination that as a result of 5G C-Band interference, certain 
airplane systems may not properly function, resulting in longer than 
normal landing or rejected takeoff distances, due to the effect on 
thrust reverser deployment, spoilers, speedbrake deployment, and 
increased idle thrust, regardless of the approach type or weather. AD 
2022-03-20 requires revising the limitations and operating procedures 
sections of the existing AFM to incorporate limitations prohibiting the 
use of certain MEL items, and to incorporate operating procedures for 
calculating takeoff and landing distances, when in the presence of 5G 
C-Band interference as identified by NOTAMs. The agency issued AD 2022-
03-20 to address degraded deceleration performance, which could lead to 
a runway excursion.

Actions Since AD 2022-03-20 Was Issued

    Since issuing AD 2022-03-20, 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 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.
    AD 2022-03-20 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 required 
by AD 2022-03-20 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 2022-03-20 does not reference NOTAMs, this proposed AD would 
retain that operating procedure requirement with no change.

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 requirements of AD 2022-03-20 
until June 30, 2023. On or before June 30, 2023, this proposed AD would 
require

[[Page 27788]]

replacing those AFM limitations with limitations prohibiting the same 
dispatching or releasing to airports, and takeoff or landings on 
runways, and use of certain MEL items at all airports for non-radio 
altimeter tolerant airplanes. For radio altimeter tolerant airplanes, 
the prohibited operations would be allowed 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 (k)(3) of this proposed AD specifies that AMOCs approved 
for AD 2021-23-12 providing relief for specific radio altimeter 
installations are approved as AMOCs for the requirements specified in 
paragraph (h) of this proposed AD until June 30, 2023. After June 30, 
2023 operators with AMOCs approved for AD 2021-23-12 would be required 
to incorporate the 5G C-Band Interference operating procedure specified 
in paragraph (h)(2) of this proposed AD. The new AFM limitations, which 
would be required by paragraph (i) or (j) of this proposed AD, specify 
that operators must comply with this 5G C-Band Interference operating 
procedure.

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 2022-03-20, 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 276 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 Boeing Model 737-8, 737-9, and 737-
8200 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 737-8, 737-9, or 737-8200 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 \2\ x $85                $0              $85          $23,460
 AD 2022-03-20).                       per hour = $85.
New AFM revisions (new proposed       1 work-hour x $85 per                 0               85       \3\ 23,460
 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.

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) 2022-03-20, Amendment 39-21937 
(87 FR 4787, January 31, 2022), and
0
b. Adding the following new AD:


[[Page 27789]]


The Boeing Company Airplanes: Docket No. FAA-2023-0671; Project 
Identifier AD-2022-01428-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 2022-03-20, Amendment 39-21937 (87 FR 4787, 
January 31, 2022) (AD 2022-03-20).

(c) Applicability

    This AD applies to all The Boeing Company 737-8, 737-9, and 737-
8200 airplanes, certificated in any category.

(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 takeoffs and landings, as a result of this interference, 
certain airplane systems may not properly function, resulting in 
longer than normal landing or rejected takeoff distances due to the 
effect on thrust reverser deployment, spoilers, speedbrake 
deployment, and increased idle thrust, regardless of the approach 
type or weather. The FAA is issuing this AD to address degraded 
deceleration performance, which could lead to a runway excursion.

(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
[GRAPHIC] [TIFF OMITTED] TP03MY23.097

    (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.

[[Page 27790]]

Figure 2 to paragraph (g)(2)(ii)--Spurious Effective Isotropic PSD 
at Outside Interface of Aircraft Antenna
[GRAPHIC] [TIFF OMITTED] TP03MY23.098

    (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.
    (4) Runway condition codes are defined in figure 3 to paragraph 
(g)(4) of this AD.
Figure 3 to paragraph (g)(4)--Runway Condition Codes

[[Page 27791]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.099

(h) Retained Airplane Flight Manual (AFM) Revision

    This paragraph restates the requirements of paragraph (h) of AD 
2022-03-20.
    (1) Within 2 days after January 31, 2022 (the effective date of 
AD 2022-03-20): Revise the Limitations Section of the existing AFM 
to include the information specified in figure 4 to paragraph (h)(1) 
of this AD. This may be done by inserting a copy of figure 4 to 
paragraph (h)(1) of this AD into the existing AFM.
Figure 4 to paragraph (h)(1)--AFM Limitations Revisions
[GRAPHIC] [TIFF OMITTED] TP03MY23.100


[[Page 27792]]


    (2) Within 2 days after January 31, 2022 (the effective date of 
AD 2022-03-20): Revise the Operating Procedures Section of the 
existing AFM to include the information specified in figure 5 to 
paragraph (h)(2) of this AD. This may be done by inserting a copy of 
figure 5 to paragraph (h)(2) of this AD into the existing AFM.
Figure 5 to paragraph (h)(2)--AFM Operating Procedures Revision
[GRAPHIC] [TIFF OMITTED] TP03MY23.101


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[GRAPHIC] [TIFF OMITTED] TP03MY23.102


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[GRAPHIC] [TIFF OMITTED] TP03MY23.103


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[GRAPHIC] [TIFF OMITTED] TP03MY23.104


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[GRAPHIC] [TIFF OMITTED] TP03MY23.105


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[GRAPHIC] [TIFF OMITTED] TP03MY23.106

(i) New Requirement: AFM 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.

[[Page 27798]]

Figure 6 to paragraph (i)--AFM Revision for Non-Radio Altimeter 
Tolerant Airplanes
[GRAPHIC] [TIFF OMITTED] TP03MY23.107

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

[[Page 27799]]

[GRAPHIC] [TIFF OMITTED] TP03MY23.108

(k) 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.

(l) 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. 2023-09434 Filed 5-1-23; 4:15 pm]
BILLING CODE 4910-13-P