90 FR 132 pgs. 31563-31564 - Notice of Intent To Cancel Withdrawal of TSO-C122a, Equipment That Prevent Blocked Channels Used in Two-Way Radio Communications Due to Simultaneous Transmissions
Type: NOTICEVolume: 90Number: 132Pages: 31563 - 31564
Pages: 31563, 31564Docket number: [Docket No.: FAA-2025-1741]
FR document: [FR Doc. 2025-13086 Filed 7-11-25; 8:45 am]
Agency: Transportation Department
Sub Agency: Federal Aviation Administration
Official PDF Version: PDF Version
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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.
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:
• Federal eRulemaking Portal: Go to www.regulations.gov and follow the online instructions for sending your comments electronically.
• 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.
• 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.
• Fax: Fax comments to Docket Operations at (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.
• 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 www.regulations.gov, including any personal information you provide. The FAA will also post a report summarizing each substantive verbal contact received.
• 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:
[top] Stephen P. Van Trees, AIR-626C, Federal Aviation Administration, 800 Independence Ave., 8th Floor, Washington, DC 20591; phone (202)
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]
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