--- title: "ETSO-2C41d — CS-ETSO · Avioverse" description: "Airborne Automatic Direction Finding (ADF) Equipment 1 Applicability This ETSO gives the requirements which airborne automatic direction finding…" url: "https://avioverse.aero/regulations/easa/cs-etso/subpart-b/etso-2c41d" --- # ETSO-2C41d European Technical Standard Orders (CS-ETSO) · CS-ETSO · EAR revision 1 Oct 2026 IR Implementing rule ## ETSO-2C41d Airborne Automatic Direction Finding (ADF) Equipment 1 Applicability This ETSO gives the requirements which airborne automatic direction finding equipment that is 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 EUROCAE document ED-51 (1983 rev. 1987) or RTCA DO-179 plus additions shown paragraph 3.2 below. 3.1.2 Environmental Standard See CS-ETSO Subpart A paragraph 2.1 3.1.3 Computer Software See CS-ETSO Subpart A paragraph 2.2 3.2 Specific Radio Technical Commission for Aeronautics (RTCA) Document DO-179 (1982), used in US TSO-C41d differs from EUROCAE document ED-51 as follows: ED-51 demands tuning increments of 0.5 kHz or less to match the European NDB frequency scheme (500 Hz channels), DO-179 demands increments of 1 kHz. 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. IR · ETSO-2C41d — CS-ETSO · ED Decision 2003/10/RM · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026 [All rules in SUBPART B – LIST OF ETSOs](https://avioverse.aero/regulations/easa/cs-etso/subpart-b) Consolidated from the EASA Easy Access Rules (revision 1 Oct 2026, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.