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Underwater Locating Devices (Acoustic) (Self-Powered)

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Federal Aviation Administration, FAA, DOT.


Notice to extend the revocation date of Technical Standard Order (TSO) C-121 and C-121a, Underwater Locating Devices (ULD) (Acoustic) (Self-Powered).


This Notice extends the planned revocation date of Technical Standard Order (TSO) authorization for the production of Underwater Locating Devices (ULD) (Acoustic) (Self-Powered) manufactured to TSO-C121 and TSO C-121a specifications. This action is necessary to facilitate an efficient transition to UDLs with a 90-day minimum battery operating life manufactured to the TSO-C121b specifications.

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Mr. John Barry, AIR-130, Federal Aviation Administration, 470 L'Enfant Plaza, SW., Suite 4102, Washington, DC 20024. Telephone 202-267-1665, Fax 202-267-8589, email:

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The FAA published a Notice in the Federal Resister, 76 FR 52734, August 23, 2011, announcing the planned revocation of TSO-C121 and TSO-C121a. Notice of that conformation was published in the Federal Register, 77 FR 13174, March 5, 2012. Thus far, only two manufacturers currently hold TSO authorizations (TSOAs) under TSO-C121 or TSO-C121a; both are domestic. Both manufacturers are now authorized to produce longer duration TSO-C121b units as envisioned by the March 5, 2012 Federal Register notice. One manufacturer received its TSO-C121b authorization in December 2014, the other in February 2015. Although both manufacturers received approval to manufacture devices meeting the current standard, the TSOA by itself does not authorize installation in an aircraft. Recent events have driven additional testing requirements for installation of lithium batteries, which these devices contain. Prior to the FAA's issuing the TSOAs to the two applicants, testing of the lithium batteries produced satisfactory results, such that the newly approved TSO-C121b devices will contain the effects of catastrophic battery failures. The ULD manufacturer's data may be used to support installations of the device on an aircraft, but each installer must analyze their design for safety impacts on their aircraft. A major aircraft manufacturer requested additional time to complete testing and analysis of the TSO-C121b device's installation. They also requested additional time to update their part numbers and drawings in their various Type Certificated (TC) aircraft once the analysis is complete. Granting this additional time will prevent a disruption in aircraft production as the necessary documentation changes are updated to reflect the current production of TSO-C121b devices.


Based on the recent award of TSO-C121b authorizations, additional testing and analysis of lithium battery Start Printed Page 12699installations and the lead time required to update required documentation, the FAA has delayed the revocation of TSO-C121 and TSO-C121a authorizations to December 1, 2015.

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Issued in Washington, DC. on March 4, 2015.

Susan J. M. Cabler,

Assistant Manager, Design, Manufacturing and Airworthiness Division, Aircraft Certification Service.

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[FR Doc. 2015-05501 Filed 3-9-15; 08:45 am]