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ETSO-C121b

European Technical Standard Orders (CS-ETSO) · CS-ETSO · EAR revision 14 Aug 2026

IRImplementing rule

ETSO-C121b

UNDERWATER LOCATING DEVICE (ACOUSTIC) (SELF-POWERED)

1 Applicability

This ETSO gives the requirements which Underwater Locating Device (Acoustic) (Self-Powered) that are manufactured on or after the date of this ETSO must meet in order to be identified with the applicable ETSO marking.

2 Procedures

- 2.1 General

Applicable procedures are detailed in CS-ETSO, Subpart A.

- 2.2 Specific

None.

3 Technical conditions

3.1 Basic

3.1.1 Minimum performance standard

Standards set forth in the SAE AS8045A, Minimum Performance Standard for Underwater Locating Devices (Acoustic) (Self-Powered), dated August 2011.

3.1.2 Environmental standard

See CS-ETSO, Subpart A, paragraph 2.1.

3.1.3 Software

See CS-ETSO, Subpart A, paragraph 2.2.

3.1.4 Airborne electronic hardware

See CS-ETSO, Subpart A, paragraph 2.3.

3.2 Specific

The battery used in the underwater locating device authorized under this ETSO must be appropriate for the intended operational environment, not pose a hazard to the aircraft and meet the requirements of acceptable battery standards. If non-rechargeable lithium batteries are used to power the underwater locating device, ETSO-C142a 'Lithium Batteries' provides MPS for such lithium batteries.

Demonstrate the saltwater immersion tests in SAE Document AS8045A, section 5.13, using a seawater solution meeting the requirements of ASTM D1141-98, Standard Practice for the Preparation of Substitute Ocean Water, dated 2008.

3.2.1 Failure condition classification

See CS-ETSO, Subpart A, paragraph 2.4.

Failure or loss of the function defined in paragraph 3.1.1 of this ETSO has been determined to be a minor failure condition.

4 Marking

4.1 General Marking is detailed in CS-ETSO, Subpart A, paragraph 1.2. 4.2 Specific None.

5 Availability of referenced document

See CS-ETSO, Subpart A, paragraph 3. [Amdt ETSO/3]

[Amdt ETSO/8]

IR · ETSO-C121b — CS-ETSO · ED Decision 2013/012/R · CS-ETSO Easy Access Rules · EAR revision 14 Aug 2026

All rules in SUBPART B -LIST OF ETSOS

Consolidated from the EASA Easy Access Rules (revision 14 Aug 2026, extracted 17 Aug 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.

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