[Federal Register Volume 88, Number 70 (Wednesday, April 12, 2023)]
[Proposed Rules]
[Pages 21931-21938]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-07743]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-0668; Project Identifier AD-2023-00199-R]
RIN 2120-AA64


Airworthiness Directives; Various Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede Airworthiness Directive 2021-23-
13, which applies to all helicopters equipped with a radio (also known 
as radar) altimeter. AD 2021-23-13 requires revising the limitations 
section of the existing rotorcraft flight manual (RFM) for your 
helicopter to incorporate limitations prohibiting certain operations 
requiring radio altimeter data when in the presence of 5G C-Band 
interference in areas as identified by Notices to Air Missions 
(NOTAMs). Since the FAA issued AD 2021-23-13, 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 RFM to incorporate limitations prohibiting 
certain operations requiring radio altimeter data, 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 12, 
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-2023-0668; 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: David Swartz, Continued Operational 
Safety Technical Advisor, COS Program Management Section, Operational 
Safety Branch, FAA, 222 W. 7th Ave, M/S #14 Anchorage, AK 99513; phone: 
817-222-5390; email: [email protected].

[[Page 21932]]


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-2023-0668; Project Identifier 
AD-2023-00199-R'' 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 David 
Swartz, Continued Operational Safety Technical Advisor, COS Program 
Management Section, Operational Safety Branch, FAA, 222 W. 7th Ave, M/S 
#14 Anchorage, AK 99513; 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 Airworthiness Directive (AD) 2021-23-13, Amendment 
39-21811 (86 FR 69992, December 9, 2021) (AD 2021-23-13), for all 
helicopters equipped with a radio altimeter. AD 2021-23-13 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 2021-23-13 requires revising the limitations section of the 
existing RFM 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 2021-23-13 
because radio altimeter anomalies that are undetected by the automation 
or pilot, particularly close to the ground, could lead to loss of 
continued safe flight and landing.
    On the same day, the FAA also issued AD 2022-23-12, Amendment 39-
21810 (86 FR 69984, December 9, 2021) (AD 2021-23-12), to correct the 
same unsafe condition on, and require similar operating limitations 
for, all transport and commuter category airplanes equipped with a 
radio altimeter.

Actions Since AD 2021-23-13

    Rotorcraft Capability and Alterations: Since issuing AD 2021-23-13 
and AD 2021-23-12, the FAA has reviewed data from alternative method of 
compliance (AMOC) requests, demonstrating that these radio altimeters 
can be relied upon to perform their intended function when operating 
beyond a certain protection radius around 5G C-Band transmitters. The 
iterative AMOC process allowed the FAA to gain insight into 5G C-Band 
transmission impacts in a progressively more sophisticated manner. At 
first, the FAA made conservative assumptions about the potential for 
impact on radio altimeters from 5G C-Band transmissions and applied 
them to all airspace. During the FAA's initial analyses of AMOC 
requests, the FAA looked to protect against 5G C-Band interference 
during critical operations that rely on radio altimeters, by 
prohibiting these operations within the vicinity of known 5G C-Band 
emitters. After some time and an improved understanding of the 5G C-
Band signals and their effects on specific radio altimeters, the FAA 
was able to reduce the protected area around the 5G C-band emitters to 
protect rotorcraft.
    The FAA received and reviewed many more AMOC proposals from 
transport category airplane operators for AD 2021-23-12 than from 
helicopter operators for AD 2021-23-13. Some of the radio altimeters 
used on rotorcraft are the same model as, or similar to, the radio 
altimeters installed on transport category airplanes. As a result, the 
AMOC process for AD 2021-23-12 and AD 2021-23-13 also provided data 
about the varying levels of interference tolerance for a majority of 
radio altimeters on the market, allowing the FAA to understand the 
overall susceptibility to interference of the existing fleet of 
rotorcraft. In addition, the FAA learned about the aircraft alterations 
that can be accomplished quickly to improve a radio altimeter's 
tolerance to transmissions in adjacent or nearby spectrum bands. Now 
that the FAA better understands the performance of specific radio 
altimeters and the means to make them more tolerant of transmissions in 
adjacent or nearby spectrum bands, the FAA is proposing to retain the 
existing prohibitions in AD 2021-23-13 with an option to upgrade to a 
radio altimeter tolerant rotorcraft to avoid the prohibitions.
    5G Compatibility: AMOCs allowing operations otherwise prohibited by 
AD 2021-23-13 were based on voluntary operational mitigations 
undertaken by AT&T and Verizon, 5G C-Band licensees. The FAA, AT&T, and 
Verizon have collaborated extensively to ensure 5G C-Band radio 
frequency transmissions and rotorcraft operations can safely co-exist. 
In early January 2022, the FAA progressively tailored runway safety 
zones around airports to envelop only the airspace areas where critical 
phases of flight occur. Although these tailored runway safety zones 
around airports primarily benefited transport and commuter airplane 
operations, they also benefited rotorcraft operating at those airports. 
This collaborative work has allowed safe rotorcraft operations to 
continue in the short term.
    Update to Safety Determination: The FAA's initial determination 
that radio altimeters cannot be relied upon to perform their intended 
function if they experience interference from wireless broadband 
operations in the 5G C-Band remains unchanged. Unlike the Terrain 
Awareness and Warnings Systems (TAWS) in transport airplanes, most 
Helicopter Terrain Avoidance Warning Systems (HTAWS) do not rely on 
radio altimeter inputs, but rather use radar altimeter data for 
vertical situational awareness in low visibility conditions (i.e., snow 
and dust blown up by rotor down wash) and as an input into several 
procedures and automated system. This means that a 5G C-Band 
interference event in most helicopters does not result in an erroneous 
HTAWS alert.
    The FAA is concerned that 5G C-Band interference events will occur 
more frequently as telecommunication companies continue to deploy 5G C-

[[Page 21933]]

Band services throughout the country and the safety benefit from the 
use of radio altimeters in helicopters will be lost. On January 11, 
2023, the FAA published an NPRM that would supersede AD 2021-23-12 for 
transport and commuter category airplanes equipped with a radio 
altimeter (88 FR 1520) (``transport NPRM''). The transport NPRM 
proposed, in part, to require that after February 1, 2024, operations 
under part 121 must be conducted with a radio altimeter tolerant 
airplane. This proposed requirement was prompted by the FAA's 
determination that erroneous system warnings due to a malfunctioning 
radio altimeter will lead to flightcrew desensitization to system 
warnings. The FAA has assessed the cumulative effects of increasing 
numbers of erroneous warnings for rotorcraft, such as the display of 
erroneous vertical position input to the pilot, and determined that it 
has not yet risen to the level of an unsafe condition. For this reason, 
the FAA is not proposing to mandate equipage of radio altimeters 
meeting certain tolerance requirements for all helicopters, as proposed 
in the transport NPRM for airplanes.
    Why New Corrective Action is Needed: The FAA expects an increase in 
the number of 5G C-Band base stations around airports in the national 
airspace system (NAS) and expects these stations to transmit in the 
entire 5G C-Band frequency band (from 3.7 to 3.98 GHz). Since the FAA 
issued AD 2021-23-13, which focused solely on a limited airspace 
environment, 5G C-Band base stations have increasingly begun 
transmission in other areas of the country. Whereas 5G C-Band 
transmissions were initially limited to 3.7 to 3.8 GHz, these 
transmissions have also begun to expand to 3.8 to 3.98 GHz, and the FAA 
expects deployment at the higher end of the frequency range to expand 
after July 1, 2023.\1\ These higher frequencies are nearer to the 
spectrum allocation where radio altimeters operate (4.2 to 4.4 GHz), 
which means that the potential for interference to radio altimeters 
from in-band and spurious \2\ emissions may be more likely. In 
addition, the FAA expects approximately 19 additional telecommunication 
companies in addition to AT&T and Verizon will begin transmitting in 
the C-Band at some point after June 2023.\3\ As the 21 
telecommunication companies authorized to transmit 5G C-Band continue 
to expand transmissions throughout the country, using NOTAMs to 
identify affected areas and assessing proposed AMOCs will become 
untenable. NOTAMs are temporary means of disseminating information 
until the information can be publicized by other means. Given 5G C-Band 
signals are not expected to be temporary and that 5G C-Band signals 
will cover the contiguous U.S., NOTAMs are no longer the best means of 
communicating the location of the 5G C-Band environment. In addition, 
given the information gleaned over the past year, the FAA is now able 
to identify the conditions under which radio altimeters can be relied 
on to perform their intended function in the presence of a 5G C-Band 
environment. Therefore, case-by-case AMOC approvals that allow 
performing certain operations otherwise prohibited by an AD are no 
longer the most efficient way for helicopter operators to show that 
their radio altimeters perform their intended function in the 5G C-Band 
environment.
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    \1\ FCC licenses authorized 5G transmissions from 3.7 to 3.98 
GHz.
    \2\ The tolerance to 5G spurious emissions is the level of 
aggregate interference in the radio altimeter band below which the 
installed radio altimeter system will meet its performance standards 
and perform its intended function.
    \3\ The additional 19 telecommunications companies will have 
access to the FCC-licensed spectrum after current users vacate use 
of the frequencies.
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    Determination of Rotorcraft Radio Altimeter Tolerance Requirements: 
The FAA is proposing interference tolerance requirements for radio 
altimeters that can be used across the affected fleet. Rotorcraft 
meeting these proposed minimum performance levels would be allowed to 
perform the prohibited operations in the contiguous U.S. airspace and 
would no longer be required to include the RFM limitations specified in 
AD 2021-23-12. After July 1, 2023, rotorcraft that do not meet the 
proposed minimum performance levels would be subject to the prohibited 
operations.
    The FAA determined the proposed interference tolerance requirements 
by using the fuller understanding of specific radio altimeter 
capabilities the FAA gained during the AMOC process for AD 2021-23-12 
and AD 2021-23-13. This process revealed the radio altimeter 
modifications that would not require a substantial system redesign, 
allowing aircraft operators to readily replace radio altimeters or 
install filters that allowed the aircraft to operate safely in a 
mitigated 5G environment.
    The interference tolerance requirements are represented by a power 
spectral density (PSD) curve. The PSD curve, as depicted in figure 1 to 
paragraph (g)(1) of this proposed AD, represents the height over the 
ground and received power from a 5G C-Band emitter, at or below which 
the radio altimeter is expected to function reliably, measured in 
decibel-milliwatts (dBm) per megahertz (MHz). For purposes of this 
proposed AD, a ``radio altimeter tolerant rotorcraft'' is one for which 
the radio altimeter, as installed, demonstrates tolerance to radio 
altimeter interference at or above PSD curve threshold specified in 
figure 1 to paragraph (g)(1) of this proposed AD. A radio altimeter 
tolerant rotorcraft also demonstrates tolerance to an aggregate 
spurious emission level of -42 dBm/MHz in the 4200-4400 MHz radio 
altimeter band. For purposes of this proposed AD, a ``non-radio 
altimeter tolerant rotorcraft'' is one for which the radio altimeter, 
as installed, does not demonstrate those tolerances. Operators will 
have the option to upgrade to a radio altimeter tolerant rotorcraft if 
they wish to avoid the prohibitions in this proposed AD. Some operators 
may need to install filters between the radio altimeter and antenna to 
increase a radio altimeter's tolerance. For others, the addition of a 
filter will not be sufficient to address interference susceptibility; 
therefore, the radio altimeter will need to be replaced with an 
upgraded radio altimeter. The FAA has determined that radio altimeter 
tolerant rotorcraft are not expected to experience interference during 
a critical phase of flight in the contiguous U.S. airspace.
    Areas of Operation: Over the past year, the FAA and the aviation 
industry, using data voluntarily provided by AT&T and Verizon, have 
identified maximum power levels for 5G C-Band transmissions that would 
permit safe aircraft operations. This data includes 5G C-Band tower or 
antenna locations, fundamental transmission power levels, and antenna 
height. The FAA has found that rotorcraft meeting the proposed 
standards as represented by the PSD curve can safely perform the 
prohibited operations specified in this proposed AD. These operations 
are safe for radio altimeter tolerant rotorcraft to perform within the 
contiguous U.S. airspace as long as telecommunication companies 
transmit at parameters under the current voluntary agreements with the 
FAA and FCC.
    Compatibility with 5G C-Band Providers: The FAA has determined that 
any U.S. 5G C-Band provider that maintains the mitigated actions will 
not have an effect on the safety of rotorcraft with radio altimeters 
that meet the interference tolerance requirements. The FAA will assess 
the effects of any changes to transmission parameters in

[[Page 21934]]

the contiguous U.S. airspace to determine whether they would result in 
a hazard to air navigation. If the transmission changes negatively 
affect the safe operation of a radio altimeter tolerant rotorcraft, the 
FAA will re-evaluate the risks and determine if further rulemaking is 
warranted.
    Therefore, the FAA has determined that an unsafe condition exists 
when performing certain operations in the presence of 5G C-Band 
transmissions affecting the proper function of radio altimeters. For 
that reason, operators would be required to revise their existing RFM 
to prohibit these operations unless operating a radio altimeter 
tolerant rotorcraft. This proposed requirement would take effect on 
July 1, 2023.

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

    For rotorcraft with radio altimeters that meet the proposed 
interference tolerance requirements, this proposed AD would terminate 
the operational limitations imposed by AD 2021-23-13 with no further 
action.
    For rotorcraft with radio altimeters that do not meet the proposed 
interference tolerance requirements, this proposed AD would retain the 
requirement in AD 2021-23-13 to revise the existing RFM to incorporate 
limitations prohibiting the following operations in the presence of 5G 
C-Band wireless broadband interference as identified by NOTAM (NOTAMs 
will be issued to state the specific airports where the radio altimeter 
is unreliable due to the presence of 5G C-Band wireless broadband 
interference) until June 30, 2023. On or before June 30, 2023, this 
proposed AD would also require, for non-radio altimeter tolerant 
rotorcraft, revising the existing RFM to incorporate limitations 
prohibiting these same operations in the contiguous U.S. airspace.

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 
rotorcraft incorporating equipment approved under the new Radio 
Altimeter TSO will be able to operate in the contiguous U.S. airspace 
with no 5G C-Band-related RFM limitations. Once a new radio altimeter 
TSO is developed, approved, and available, the FAA might consider 
additional rulemaking.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 1,128 helicopters of U.S. registry. The FAA estimates the 
following costs to comply with this proposed AD.

                                                 Estimated Costs
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                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
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RFM revision for non-radio altimeter    1 work-hour x $85 per                 $0             $85         $95,880
 tolerant rotorcraft (Retained action    hour = $85.
 from AD 2021-23-13).
New RFM revision for non-radio          1 work-hour x $85 per                  0              85          95,880
 altimeter tolerant rotorcraft.          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) 2021-23-13, Amendment 39-21811 
(86 FR 69992, December 9, 2021), and
0
b. Adding the following new AD:

Various Helicopters: Docket No. FAA-2023-0668; Project Identifier 
AD-2023-00199-R.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by May 12, 2023.

[[Page 21935]]

(b) Affected ADs

    This AD replaces AD 2021-23-13, Amendment 39-21811 (86 FR 69992, 
December 9, 2021) (AD 2021-23-13).

(c) Applicability

    This AD applies to all helicopters, certificated in any 
category, equipped with a radio (also known as radar) altimeter. 
These radio altimeters are installed on various helicopter models 
including, but not limited to, the helicopters for which the design 
approval holder is identified in paragraphs (c)(1) through (20) of 
this AD.

(1) Airbus Helicopters
(2) Airbus Helicopters Deutschland GmbH
(3) Air Space Design and Manufacturing, LLC
(4) Bell Textron Canada Limited
(5) Bell Textron Inc.
(6) Brantly International, Inc.
(7) Centerpointe Aerospace Inc.
(8) Columbia Helicopters, Inc.
(9) The Enstrom Helicopter Corporation
(10) Erickson Air-Crane Incorporated, DBA Erickson Air-Crane
(11) Helicopteres Guimbal
(12) Siam Hiller Holdings, Inc.
(13) Kaman Aerospace Corporation
(14) Leonardo S.p.a.
(15) MD Helicopters Inc.
(16) PZL Swidnik S.A.
(17) Robinson Helicopter Company
(18) Schweizer RSG LLC
(19) Scotts-Bell 47 Inc.
(20) Sikorsky Aircraft Corporation

(d) Subject

    Air Transport Association (ATA) of America Code 3444, Ground 
Proximity System.

(e) Unsafe Condition

    This AD was prompted by 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). The FAA is issuing this AD 
because radio altimeter anomalies that are undetected by the 
automation or pilot, particularly close to the ground, could lead to 
loss of continued safe flight and landing.

(f) Compliance

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

(g) Definitions

    (1) For purposes of this AD, a ``radio altimeter tolerant 
rotorcraft'' is one for which the radio altimeter, as installed, 
demonstrates the tolerances specified in paragraphs (g)(1)(i) and 
(ii) of this AD, using a method approved by the FAA. No actions are 
required by this AD for radio altimeter tolerant rotorcraft.
    (i) Tolerance to radio altimeter interference at or above the 
power spectral density (PSD) curve threshold specified in figure 1 
to paragraph (g)(1) of this AD.
    (ii) Tolerance to an aggregate base station conducted spurious 
emission level of -42 dBm/MHz in the 4200-4400 MHz radio altimeter 
band.

Figure 1 to paragraph (g)(1)--Effective Power Spectral Density
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[[Page 21936]]

[GRAPHIC] [TIFF OMITTED] TP12AP23.030

    (2) For purposes of this AD, a ``non-radio altimeter tolerant 
rotorcraft'' is one for which the radio altimeter, as installed, 
does not demonstrate the tolerances specified in paragraphs 
(g)(1)(i) and (ii) of this AD.

(h) Retained Rotorcraft Flight Manual (RFM) Revision for Non-Radio 
Altimeter Tolerant Rotorcraft

    For non-radio altimeter tolerant rotorcraft: On or before 
January 4, 2022, revise the Limitations Section of the existing RFM 
for your helicopter by incorporating the limitations specified in 
figure 2 to paragraph (h) of this AD. This may be done by inserting 
a copy of this AD into the existing RFM for your helicopter. The 
action required by this paragraph may be performed by the owner/
operator (pilot) holding at least a private pilot certificate and 
must be entered into the aircraft records showing compliance with 
this AD in accordance with 14 CFR 43.9(a)(1) through (4) and 14 CFR 
91.417(a)(2)(v). The record must be maintained as required by 14 CFR 
91.417 or 14 CFR 135.439.
Figure 2 to paragraph (h)--RFM Revision

[[Page 21937]]

[GRAPHIC] [TIFF OMITTED] TP12AP23.031

(i) RFM Revision for Non-Radio Altimeter Tolerant Rotorcraft

    For non-radio altimeter tolerant rotorcraft, 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 RFM for your helicopter by including the information 
specified in figure 3 to paragraph (i) of this AD. This may be done 
by inserting a copy of this AD into the existing RFM for your 
helicopter. The action required by this paragraph may be performed 
by the owner/operator (pilot) holding at least a private pilot 
certificate and must be entered into the aircraft records showing 
compliance with this AD in accordance with 14 CFR 43.9(a)(1) through 
(4) and 14 CFR 91.417(a)(2)(v). The record must be maintained as 
required by 14 CFR 91.417 or 14 CFR 135.439. Incorporating the RFM 
revision required by this paragraph terminates the RFM revision 
required by paragraph (h) of this AD.
    (2) Before further flight after incorporating the limitations 
specified in figure 3 to paragraph (i) of this AD, remove the RFM 
revision required by paragraph (h) of this AD.
Figure 3 to paragraph (i)--RFM Revision for Non-Radio Altimeter 
Tolerant Rotorcraft 
[GRAPHIC] [TIFF OMITTED] TP12AP23.032

(j) 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 (k) 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 2021-23-13 are approved as AMOCs for 
the requirements specified in paragraph (h) of this AD until June 
30, 2023.

(k) Related Information

    For more information about this AD, contact David Swartz, 
Continued Operational Safety Technical Advisor, COS Program 
Management Section, Operational Safety Branch, FAA, 222 W. 7th Ave, 
M/S #14 Anchorage, AK 99513; phone: 817-222-5390; email: 
[email protected].

(l) Material Incorporated by Reference

    None.


[[Page 21938]]


    Issued on April 5, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-07743 Filed 4-10-23; 8:45 am]
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