This section of the FEDERAL REGISTER
contains notices to the public of the proposedissuance of rules and regulations. Thepurpose of these notices is to give interestedpersons an opportunity to participate in therule making prior to the adoption of the finalrules.Proposed RulesFederal Register29554 
Vol. 88, No. 88 
Monday, May 8, 2023 
1Amendment 39–21810, 86 FR 69984, December 
9, 2021. 
2Amendment 39–21811, 86 FR 69992, December 
9, 2021. DEPARTMENT OF TRANSPORTATION 
Federal Aviation Administration 
14 CFR Part 21 
[Docket No. FAA–2023–0938] 
Proposed Policy Statement; 
Demonstration of Radio Altimeter Tolerant Aircraft 
AGENCY : Federal Aviation 
Administration, DOT. 
ACTION : Notification of availability; 
request for comments. 
SUMMARY : This document announces the 
availability of a draft Policy Statement PS–AIR–600–39–01, Demonstration of Radio Altimeter Tolerant Aircraft. The FAA invites public comment on PS– AIR–600–39–01. 
DATES : The FAA must receive comments 
on this document on or before June 7, 2023. 
ADDRESSES : You may send comments 
identified by docket number FAA– 2023–0938 using any of the following methods: 
bFederal eRulemaking Portal: Go to 
www.regulations.gov and follow the 
instructions for submitting comments electronically. 
bMail: U.S. Department of 
Transportation, Docket Operations, M– 30, 1200 New Jersey Avenue SE, Room W12–140, West Building Ground Floor, Washington, DC 20590–0001. 
bHand Delivery: Deliver to Mail 
address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. 
bFax: (202) 493–2251. 
Docket: Background documents or 
comments received may be read at www.regulations.gov at any time. 
Follow the online instructions for accessing the docket or go to the Docket Operations in Room W12–140 of the West Building Ground Floor at 1200 New Jersey Avenue SE, Washington, DC, between 9 a.m., and 5 p.m., Monday through Friday, except Federal holidays. FOR FURTHER INFORMATION CONTACT : 
Barbara Clark, Aviation Safety Specialist, Avionics and Electrical Systems Section, 800 Independence Ave. SW, DC 20591; telephone: 817– 222–5390; email: operationalsafety@faa.gov. 
SUPPLEMENTARY INFORMATION : 
Privacy: The FAA will post all 
comments it receives, without change, to www.regulations.gov, including any 
personal information the commenter provides. Using the search function of the docket website, anyone can find and read the electronic form of all comments received into any FAA docket, including the name of the individual sending the comment (or signing the comment for an association, business, labor union, etc.). DOT’s complete Privacy Act Statement can be found in the Federal Register published on April 
11, 2000 (65 FR 19477–19478), as well as at https://DocketsInfo.dot.gov. 
Comments Invited 
The FAA invites interested parties to 
take part in the development of the 
proposed policy statement by sending written comments to an address listed under 
ADDRESSES . Include Docket No. 
FAA–2023–0938; Policy No. PS–AIR– 600–39–01 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 policy. 
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 notice 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 notice, 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 notice. Submissions containing CBI should be sent to the individual listed under 
FOR FURTHER INFORMATION  
CONTACT . Any commentary that the FAA 
receives that is not specifically designated as CBI will be placed in the public docket for this notice. 
Background 
The current performance standards 
for radio altimeters (also known as radar 
altimeters) are based on the presumption that no occupancy of an adjacent radio frequency spectrum would cause interference with radio altimeters. During 2021, the radio frequency operating environment surrounding radio altimeters substantially changed when wireless telecommunication service providers began offering 5G C-Band services near the 4.2–4.4 GHz band, which is reserved for aviation radio altimeters. The FAA subsequently determined that radio altimeters cannot be relied upon to perform their intended function if they experience interference from 5G wireless broadband operations in the C- Band. 
Deployment of the new 5G C-Band 
services prompted the FAA to address the risks posed by radio frequency (RF) interference to radio altimeters. On December 7, 2021, the FAA issued AD 2021–23–12
1for transport and 
commuter category airplanes equipped with a radio altimeter and AD 2021–23– 13
2for helicopters equipped with a 
radio altimeter. AD 2021–23–12 and AD 2021–23–12 prohibit certain flight operations requiring radio altimeter data when flying in the presence of 5G C- Band interference as identified by Notices to Air Missions (NOTAMs). In response to AD 2021–23–12, the aviation industry developed a method to show compatibility with 5G emissions 
VerDate Sep<11>2014 18:58 May 05, 2023 Jkt 259001 PO 00000 Frm 00001 Fmt 4702 Sfmt 4702 E:\FR\FM\08MYP1.SGM 08MYP1ddrumheller on DSK120RN23PROD with PROPOSALS129555 Federal Register / Vol. 88, No. 88 / Monday, May 8, 2023 / Proposed Rules 
3Docket No. FAA–2022–1647, 88 FR 1520 
(January 11, 2023). 
4Docket No. FAA–2023–0668, 88 FR 21931 (April 
12, 2023). in the United States national airspace 
system for the initial 5G deployment, which was limited to 3.7–3.8 GHz, and the 5G spurious emissions in the radio altimeter band (4.2–4.4 GHz). The FAA accepted this method as support for proposals for alternative methods of compliance (AMOCs) with AD 2021– 23–12 and AD 2021–23–13. These AMOCs used standardized assessment parameters, values, and methods to 
estimate an installed altimeter system protection radii or distance. Aircraft with an altimeter operating beyond this distance from all 5G base stations would not expect deleterious effects from RF incompatibility and indeed could depend upon the radio altimeter system to fully perform its intended function. These AMOCs were based on interference thresholds of specific individual radio altimeter transceivers. That is, each transceiver was tested to benchmark their performance in the presence of out-of-band and in-band C- Band signals. The thresholds were then modified and tailored to installation factors specific to the installed platform (e.g., measured antenna gains and line 
losses). These values were then used to determine the necessary mitigations to protect the airport airspace most critical for the safety of operations. The mitigations included actions by wireless providers as well as flight limitations imposed by the FAA for the airspace areas identified by NOTAM, unless operating under an approved AMOC. 
On January 6, 2023, the FAA issued 
a notice of proposed rulemaking (NPRM) proposing to supersede AD 2021–23–12.
3On April 5, 2023, the 
FAA issued an NPRM proposing to supersede AD 2021–23–13.
4The flight 
limitations in the new proposed ADs would depend on whether an aircraft has a radio altimeter that demonstrates certain tolerances using a method approved by the FAA. 
Proposed Policy Statement 
This proposed policy would provide 
guidance for operators and 
manufacturers to demonstrate an aircraft is a radio altimeter tolerant aircraft, under the proposed definition in the NPRMs. 
You may review the proposed policy 
statement at www.regulations.gov in 
Docket No. FAA–2023–0938; or on the FAA’s website at www.faa.gov/aircraft/ draft_ docs/. Issued on May 2, 2023. 
Michael Linegang, 
Acting Director, Compliance & Airworthiness 
Division, Aircraft Certification Service. 
[FR Doc. 2023–09622 Filed 5–5–23; 8:45 am] 
BILLING CODE 4910–13–P 
DEPARTMENT OF TRANSPORTATION 
Federal Aviation Administration 
14 CFR Part 39 
[Docket No. FAA–2023–0934; Project 
Identifier AD–2022–01443–T] 
RIN 2120–AA64 
Airworthiness Directives; The Boeing 
Company Airplanes 
AGENCY : Federal Aviation 
Administration (FAA), DOT. 
ACTION : Notice of proposed rulemaking 
(NPRM). 
SUMMARY : The FAA proposes to adopt a 
new airworthiness directive (AD) for all The Boeing Company Model 747–8F and 747–8 series airplanes. This proposed AD was prompted by a report of cracks in stringers, common to the end fittings, on the aft side of the bulkhead at station 2598. This proposed AD would require detailed inspections of the stringers, common to the end fittings, forward and aft of the bulkhead at a certain station for cracking and applicable on-condition actions. 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 June 22, 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–2023–0934; 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. Material Incorporated by Reference: 
•For service information identified 
in this NPRM, contact Boeing 
Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110–SK57, Seal Beach, CA 90740–5600; telephone 562–797–1717; website myboeingfleet.com. 
•You may view this service 
information at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206–231–3195. It is also available at regulations.gov by searching for and 
locating Docket No. FAA–2023–0934. 
FOR FURTHER INFORMATION CONTACT : 
Stefanie Roesli, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206– 231–3964; email: stefanie.n.roesli@faa.gov. 
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–2023–0934; Project Identifier AD– 2022–01443–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 this 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 NPRM. 
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 
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