Notice2025-13086
Notice of Intent To Cancel Withdrawal of TSO-C122a, Equipment That Prevent Blocked Channels Used in Two-Way Radio Communications Due to Simultaneous Transmissions
Primary source
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Published
July 14, 2025
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
This notice announces the FAA's withdrawal of the notice of intent to cancel Technical Standard Order (TSO-)C122a, "Equipment That Prevent Blocked Channels Used in Two-Way Radio Communications Due to Simultaneous Transmissions," dated June 18, 2012. Retaining TSO-C122a as an active TSO allows the continued design or production of articles authorized under the existing TSO approval. This withdrawal reflects the FAA's decision to maintain support for existing authorizations under TSO-C122a.
Full Text
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<title>Federal Register, Volume 90 Issue 132 (Monday, July 14, 2025)</title>
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[Federal Register Volume 90, Number 132 (Monday, July 14, 2025)]
[Notices]
[Pages 31563-31564]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-13086]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
[Docket No.: FAA-2025-1741]
Notice of Intent To Cancel Withdrawal of TSO-C122a, Equipment
That Prevent Blocked Channels Used in Two-Way Radio Communications Due
to Simultaneous Transmissions
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of intent to withdrawal cancellation of TSO-C122a.
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SUMMARY: This notice announces the FAA's withdrawal of the notice of
intent to cancel Technical Standard Order (TSO-)C122a, ``Equipment That
Prevent Blocked Channels Used in Two-Way Radio Communications Due to
Simultaneous Transmissions,'' dated June 18, 2012. Retaining TSO-C122a
as an active TSO allows the continued design or production of articles
authorized under the existing TSO approval. This withdrawal reflects
the FAA's decision to maintain support for existing authorizations
under TSO-C122a.
DATES: Comments on this notice must identify the notice docket number
and must be received on or before August 13, 2025 or as applicable.
ADDRESSES: Send comments identified by docket number FAA-2025-1741
using any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://www.regulations.gov">www.regulations.gov</a> and
follow the online instructions for sending your comments
electronically.
<bullet> Mail: Send comments to Docket Operations, M-30; U.S.
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
<bullet> Hand Delivery or Courier: Take comments to 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.
<bullet> Fax: Fax comments to Docket Operations at (202) 493-2251.
<bullet> Docket: Background documents or comments received may be
read at <a href="http://www.regulations.gov">www.regulations.gov</a> 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.
<bullet> Privacy: Except for Confidential Business Information
(CBI) as described in the following paragraph, and other information as
described in title 14, Code of Federal Regulations (14 CFR) 11.35, the
FAA will post all comments received without change to
<a href="http://www.regulations.gov">www.regulations.gov</a>, including any personal information you provide.
The FAA will also post a report summarizing each substantive verbal
contact received.
<bullet> Confidential Business Information: 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 the indicated comments
will not be placed in the public docket of this notice. Send
submissions containing CBI to the Information Contact below. Comments
the FAA receives, which are not specifically designated as CBI, will be
placed in the public docket for this notice.
FOR FURTHER INFORMATION CONTACT: Stephen P. Van Trees, AIR-626C,
Federal Aviation Administration, 800 Independence Ave., 8th Floor,
Washington, DC 20591; phone (202)
[[Page 31564]]
359-4165; email <a href="/cdn-cgi/l/email-protection#90e3e4f5e0f8f5febee6f1fee4e2f5f5e3d0f6f1f1bef7ffe6"><span class="__cf_email__" data-cfemail="f98a8d9c89919c97d78f98978d8b9c9c8ab99f9898d79e968f">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Background
TSO-C122 provides standards for equipment designed to prevent
blocked channels in two-way radio communications caused by simultaneous
transmissions. Originally issued in April 1994, the current revision,
TSO-C122a, was issued on August 26, 2005.
On June 18, 2012, the FAA issued a Notice of Intent to Cancel TSO-
C122a (77 FR 37734), citing that only one manufacturer has been issued
a letter of TSO design approval since the original issuance of TSO-C122
in 1994. The FAA also cited ``the eventual obsolescence of TSO-C122a
equipment.''
The FAA received no public comments in response to TSO-C122a and
has not granted any new authorizations or letter of TSO design
approvals since the notice was published. As a result, the FAA has not
finalized the cancellation of the TSO. TSO-C122a remains active, and
manufacturers may continue to use TSO-C122a when designing and
producing equipment for TSO authorization or letters of TSO design
approval.
Recent Safety Investigation
The National Transportation Safety Board (NTSB) in 2025
investigated a midair collision. According to the NTSB's investigation
preliminary report, the flightcrew of an aircraft involved in a midair
collision may not have received a critical air traffic control
instruction shortly before the collision due to simultaneous radio
transmissions.
TSO-C122a equipment is designed to prevent blocked communications
caused by simultaneous transmissions. As a result, this TSO-C122a
equipment could reduce the risk of similar incidents in the future.
FAA Action
In light of the NTSB's findings, the FAA is withdrawing its prior
intent to cancel TSO-C122a and is also reopening the associated comment
period.
RTCA Special Committee 226, Audio Systems and Equipment, which was
referenced in TSO-C122a, dated June 18, 2012, is no longer active. When
the committee was active, the FAA intended to ``continue to coordinate
. . . for any new developments on other means being used to address
blocked channels caused by simultaneous transmissions.'' The FAA now
invites stakeholder input on current technical standards or operational
practices that serve a similar function.
Request for Comments
The FAA seeks further public comments on the technical
implementation and operational considerations related to TSO-C122a.
Given that TSO-C122a, dated June 18, 2012, cited ``the eventual
obsolescence of TSO-C122a equipment'' as part of the rationale for the
original intent to withdraw the TSO, the FAA specifically invites
comments on whether TSO-C122a and the standard it references, RTCA/DO-
209 (``Minimum Operational Performance Standards For Devices That
Prevent Blocked Channels Used In Two-Way Radio Communications Due To
Simultaneous Transmissions,'' dated April 23, 1992), are obsolete or
obsolescent. If so, the FAA welcomes input to identify current
technologies that may have replaced them.
Issued in Kansas City, Missouri, on July 9, 2025.
James D. Foltz,
Deputy Director, Policy and Standards Division, Aircraft Certification
Service.
[FR Doc. 2025-13086 Filed 7-11-25; 8:45 am]
BILLING CODE 4910-13-P
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