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Emergency Locator Transmitters (ELTs)

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Notice of intent to cancel Technical Standard Order (TSO)-C91a, Emergency Locator Transmitter (ELT) Equipment.


This notice announces the FAA's intent to cancel TSO-C91a, Emergency Locator Transmitter (ELT) Equipment. The effect of the cancelled TSO will result in no new TSO-C91a design or production approvals. However, cancellation will not affect production according to an existing TSO authorization (TSOA). Articles produced under an existing TSOA can still be installed according to existing airworthiness approvals and applications for new airworthiness approvals will still be processed. This action does not impact operation of TSO-C91a ELTs, and these ELTs will continue to satisfy the 14 Code of Federal Regulation (14 CFR) § 91.207 ELT equipage requirement.


Comments must be received on or before February 10, 2012.


Mr. Albert Sayadian, AIR-130, Federal Aviation Administration, 470 L'Enfant Plaza, Suite 4102 Washington, DC 20024. Telephone (202) 385-4652, fax (202) 385-4651, email to:


Comments Invited

You are invited to comment on the cancellation of the TSO by submitting written data, views, or arguments to the above address. You are requested to use the attached comment sheet to make the comment review process more efficient. Comments received may be examined, both before and after the closing date, in suite 4102 at the above address, weekdays except federal holidays, between 8:30 a.m. and 4:30 p.m. The Director, Aircraft Certification Service, will consider all comments received on or before the closing date.


On December 23, 1992, the FAA published technical standard order (TSO-C126), 406 MHz Emergency Locator Transmitters (ELT), for which numerous TSO authorizations have been approved. On December 17, 2008, the FAA published a revision to the TSO, TSO-C126a. The TSO is a minimum performance standard for ELTs that utilize the 406.0 to 406.1 MHz band. TSO-C126 and TSO-C126a 406 MHz ELTS are monitored by the Cospas-Sarsat system, an international satellite-based search and rescue (SAR) distress alert detection and information distribution system.

On February 1, 2009 Cospas-Sarsat stopped processing signals from 121.5 MHz ELTs. It now only processes signals from 406 MHz ELTs. The decision to discontinue processing of the 121.5 MHz signal was made by the International Cospas-Sarsat program with guidance from the United Nations. This was made due to the problems within the 121.5 MHz frequency band which inundated SAR authorities with poor accuracy and numerous false alerts, thus impacting the effectiveness of lifesaving services. The 406 MHz ELT technology is an advance over the older 121.5 MHz ELT technology.

TSO-C126a incorporates technology that makes the ELT equipment more accurate and reliable than the 121.5 MHz ELT equipment built to the minimum performance standards in TSO-C91a. Examples of these improvements are: (1) Global satellite coverage; (2) a unique beacon identification which is required to be registered so that if an alert is launched the rescued coordination center can confirm whether the distress is real, who they are looking for, and where the search should begin; (3) 406 MHz ELTs can be received by geostationary satellites which are always visible and provide instantaneous alerting and, (4) increased position accuracy that reduces the search area to less than two nautical miles in radius. Additionally, 406 MHz ELTs which have a GPS position input can potentially reduce the search area to within 100 yards of the accident site.

The performance and benefits of TSO-C126a equipment surpasses TSO-C91a equipment. The 406 MHz technology is mature and prevalent in the ELT market today. The FAA feels new TSO authorizations for ELTs should be accomplished to TSO-C126a, or subsequent, and it is appropriate to cancel TSO-C91a.

Susan J. M. Cabler,

Assistant Manager, Aircraft Engineering Division, Aircraft Certification Service.

[FR Doc. 2012-300 Filed 1-10-12; 8:45 am]