ETSO-C112f

European Technical Standard Orders (CS-ETSO) · CS-ETSO · EAR revision 1 Oct 2026

IRImplementing rule

ETSO-C112f

SECONDARY SURVEILLANCE RADAR MODE S TRANSPONDER

1 Applicability

This ETSO provides the requirements which Secondary Surveillance Radar Mode S Transponder that are designed and 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 EUROCAE ED-73F / RTCA DO-181F, ‘Minimum Operational Performance Standards for Secondary Surveillance Radar Mode S Transponders’, dated December 2020, as modified by Change 1, dated January 2022, and as amended by Appendix 1 to this ETSO.

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

None.

3.2.1 Failure Condition Classification

See CS-ETSO, Subpart A, paragraph 2.4.

Failure of the function defined in paragraph 3.1.1 of this ETSO resulting in misleading information is a major failure condition. Failure of the function defined in paragraph 3.1.1 of this ETSO resulting in a lack of responses to valid interrogations to a degree sufficient to create potential for a missing resolution advisory (RA) is a major failure condition.

Failure of the function defined in paragraph 3.1.1 of this ETSO resulting in any of the below is a major failure condition:

— replies sent with incorrect timing;

— replies sent with an incorrect altitude;

— transmission of incorrect information to a connected collision avoidance system. Failure of the function defined in paragraph 3.1.1 of this ETSO resulting in annunciated loss of function is a minor failure condition.

4 Marking

4.1 General

Marking as detailed in CS-ETSO, Subpart A, paragraph 1.2.

4.2 Specific

The marking must also include the transponder’s functional level and optional additional features as provided in ED-73F, Section 1.4.2.2, as well as minimum peak output power identified by the transponder class as defined in ED-73F, Section 1.4.2.4.

5 Availability of Referenced Document

See CS-ETSO, Subpart A, paragraph 3.

[Amdt ETSO/11]

[Amdt ETSO/18]

IR · ETSO-C112f — CS-ETSO · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026

AppendixAppendix

Appendix 1 to ETSO-C112fSecondary Surveillance Radar Mode S Transponder Amendment to EUROCAE ED-73F / RTCA DO-181F requirements

Show the text

Purpose

This Appendix lists the modifications to EUROCAE ED-73F / RTCA DO-181F, ‘Minimum Operational Performance Standards for Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment’, as modified by Change 1. To enhance readability, sections of EUROCAE ED-73F / RTCA DO-181F that are modified by Change 1 are shown with the modifications implemented as the baseline text. Text added to modify EUROCAE ED-73F / RTCA DO-181F is underlined. Text to be removed is struck through. In between the sections an ellipsis, ‘[…]’, is introduced to indicate that the rest of the text is unchanged. For easy reading, all cross references are provided to EUROCAE ED-73F sections. Due to the extensive modifications, Section 5.5.8.36 is included as a complete change.

[…] 3.23.1.12.e.(3) Updating of the Data Link Capability Report

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

At intervals not exceeding four seconds, the transponder compares the current basic data link capability status with that last reported and if a difference is noted, initiates a revised basic data link capability report by Comm-B broadcast for BDS1=1 and BDS2=0.

The transponder shall initiate, generate and announce the revised basic data link capability report even if the aircraft data link capability is degraded or lost. To support this requirement, the transponder shall set the BDS for the basic data link capability report.

NOTE: The setting of the BDS code by the transponder ensures that a broadcast change of the capability report will contain the BDS code for all cases of data link failure (e.g. the loss of the transponder data link interface).

[…]

3.27.1.2 b.(1) Data Link Capability Codes in MB for All Transponder/CAS Systems

The following bits of the Data Link Capability report are allocated to providing information about the CAS system on the aircraft.

<table>

<tr>

<td>Field</td>

<td>Notes</td>

</tr>

<tr>

<td rowspan="4">CAS Extended Version Number</td>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

<td>CAS Out of Standby</td>

</tr>

<tr>

<td>Hybrid Surveillance Capability</td>

</tr>

<tr>

<td>CAS RA Capability Enabled</td>

</tr>

<tr>

<td rowspan="2">CAS Version</td>

</tr>

<tr>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

1.CAS Extended Version Number will be 0000 for all versions of TCAS. The definition of this field is as follows:

<table>

<tr>

<td rowspan="2">Meaning</td>

</tr>

<tr>

</tr>

<tr>

<td>Non-extended version</td>

</tr>

<tr>

<td>ACAS Xa version 1</td>

</tr>

<tr>

<td>ACAS Xu version 1</td>

</tr>

<tr>

<td>Reserved for future versions</td>

</tr>

</table>

2.CAS Out of Standby, Bit 48 (‘MB’ bit 16), set to ONE (1) indicates that the both the transponder & CAS functions are operational and the transponder is receiving RI=1, 2, or 3 from the CAS unit. Transponders will only receive RI=1 from CAS that are Active CAS of junior status or passive CAS, i.e. CAS with reduced capability that are limited when interacting with other CAS.

3.Hybrid Surveillance Capability, Bit 69 (‘MB’ bit 37), set to ONE (1) indicates capability of Hybrid Surveillance, and set to ZERO (0) indicates that there is no Hybrid Surveillance capability.

4.CAS RA Capability Enabled, Bit 70 (‘MB’ bit 38), is only relevant if CAS Out of Standby is a ONE (1). This field set to ONE (1) indicates that the CAS is currently capable of generating RAs. This field set to ZERO (0) indicates that CAS is not currently capable of generating RAs. In some systems, such as TCAS and ACAS Xa, this means that the system is currently only able to generate TAs. For other systems, such as ACAS Xu, this means that the system is not currently capable of generating Remain Well Clear (RWC) alerting and guidance.

5.CAS Version, Bits 71, 72 (‘MB’ bits 39, 40), are encoded in accordance with the following table. Note that unlike most other fields in a BDS Register, the MSB of this field is the higher numbered bit.

<table>

<tr>

<td rowspan="2">Meaning</td>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

<td>EUROCAE ED-143 (TCAS 7.1) (ETSO-C119c – TSO-C119e)</td>

</tr>

<tr>

<td>See CAS Extended Version Number</td>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Interrogators, such as ground based Mode S sensors, learn of the specific data link capabilities on board the aircraft by using the Data Link Capability Report protocol specified in §3.23.1.12 e.

The data bits discussed here reside in the MB field of the Data Link Capability Report. The transponder inserts these bits such that the data appears appropriately in response to a request for Data Link Capability Report when BDS1=1 and BDS2=0. As such, these data bits comprise only a small fraction of the entire Data Link Capability Report which may collate data from multiple sources for transfer in the downlink. Care must be taken to ensure that the data fields discussed in the following paragraphs are not compromised when other sources attempt to update the Data Link Capability Report, and that updating of these bits does not compromise other parts of the Data Link Capability Report.

3.27.1.2 b.(2) Data Link Capability Codes in MB for Systems Loaded Directly by CAS The following guidance applies to all ‘loaded directly by CAS’ (as defined in §3.27.f) transponder/CAS.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

[…]

3.27.2.3 CAS Failure Data Handling

When a CAS failure is detected, the transponder shall perform the following:

• Set RI (see §3.27.1.5) to ZERO.

• Set SL (see §3.18.4.35) to ZERO.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

• Set BDS 0,F and 3,2 through 3,F to ZERO.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

2.A CAS failure during an active RA will trigger RA termination (RAT=1). The frozen RA report will be retained while RAT=1 and set to ZERO upon RAT expiration.

[…]

3.31.3 Update Interval a. The maximum update interval at which a data field in a Register will be reloaded with valid data is defined for each register in Table B-2-1 in Appendix B.

b. The transponder will load valid data into the related transponder Register as soon as it becomes available at the Mode S Specific Services Entity.

c. The time between availability of data that causes a change in a data field of a Register and the time that the change is made to the Register will be less than the maximum update interval specified in Table B-2-1 in Appendix B.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

[…]

5.5.8.34 Procedure #30: Sensitivity Level Operation (§3.27.1.5)

This test verifies that the transponder receives sensitivity level information from the CAS unit and correctly reports this information in outgoing DF=0, 16 replies.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

a. Send a status = ‘Active CAS with resolution capability’ and a sensitivity level=6 to the transponder via the transponder/CAS interface.

Interrogate the transponder with a UF=0 and a UF=16 non-acquisition interrogation.

Show that the transponder correctly reports the CAS status and sensitivity level in the RI and SL fields respectively.

b. Not used.

c. Not used.

d. Send a sensitivity level=4 to the transponder via the transponder/CAS interface. Interrogate the transponder with a UF=0 and a UF=16 non-acquisition interrogation.

Show that the transponder correctly reports the CAS status and sensitivity level in the RI and SL fields respectively.

e. Send a status = ‘CAS with resolution capability inhibited’ and a sensitivity level=2 to the transponder via the transponder/CAS interface.

Interrogate the transponder with a UF=0 and a UF=16 non-acquisition interrogation.

Show that the transponder correctly reports the CAS status and sensitivity level in the RI and SL fields respectively.

f. Send a status = ‘No operating CAS’ and a sensitivity level=1 to the transponder via the transponder/CAS interface.

Interrogate the transponder with a UF=0 and a UF=16 non-acquisition interrogation.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

g. Send a status = ‘Active CAS of junior status with resolution capability or Passive CAS with resolution capability’ and a sensitivity level=3 to the transponder via the transponder/CAS interface.

Interrogate the transponder with a UF=0 and a UF=16 non-acquisition interrogation.

Show that the transponder correctly reports the CAS status and sensitivity level in the RI and SL fields respectively.

[…]

5.5.8.36.2 Procedure #32: Transmission of CAS Capability Information to a Mode S Sensor (§3.27.g, §3.27.1.2.b, §3.27.1.2.b.1, and §3.27.1.2.b.2) and to other CAS Aircraft (§3.27.1.5) for a Transponder Capable of Being Loaded Directly by CAS [Figure or form omitted from this preview — available in the Avioverse workspace library.]

b. Interrogate the transponder with a non-acquisition UF=0 interrogation.

Show that the transponder replies with the correct capability information in the DF=0 reply (i.e. RI=0).

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

UF=4 with RR=17 and DI7;

UF=5 with RR=17 and DI7;

UF=20 with RR=17, DI=7, and RRS=0;

UF=21 with RR=17, DI=7, and RRS=0.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

DO-185A TCAS: Bits 43 – 46: 0000, Bits 71, 72: 10

DO-185B / ED-143 TCAS: Bits 43 – 46: 0000, Bits 71, 72: 01

DO-385 / ED-256 ACAS Xa: Bits 43 – 46: 0001, Bits 71, 72: 11

DO-386 / ED-275 ACAS Xu: Bits 43 – 46: 0010, Bits 71, 72: 11

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

[…]

5.5.8.37.1 Procedure #33: CAS or transponder/CAS Interface Failure During Transmission of RA Report and Data Link Capability Report to a Mode S Sensor (§3.27.1.2 a (2) and §3.27.1.2 b (2) for a Transponder Operating with an RTCA DO-185A or EUROCAE ED-143 or EUROCAE ED-256 compatible CAS For each of the CAS versions use the following values to validate that the CAS version is correctly reported in the Data Link Capability Report:

DO-185A TCAS: Bits 43 – 46: 0000 , Bits 71, 72: 10

DO-185B TCAS: Bits 43 – 46: 0000 , Bits 71, 72: 01

ED-256 ACAS Xa: Bits 43 – 46: 0001 , Bits 71, 72: 11 a. Send the following content for the RA report to the transponder via the transponder/CAS interface once per second for 5 seconds.

<table>

<tr>

</tr>

<tr>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Interrogate the transponder once per second during the 5 seconds described above and for an additional 25 seconds (30 seconds total) with UF=4 interrogations with RR=19, DI=7, and RRS=0 and with UF=4 interrogations with RR=19, DI=7, and RRS=1.

Show that in the DF=20 RA report replies:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

For the first 5 seconds, the RA Report has the following content:

<table>

<tr>

</tr>

<tr>

<td>Same as input</td>

<td>Same as input</td>

</tr>

</table>

<table>

<tr>

</tr>

<tr>

</tr>

</table>

For the next 18 ±1 seconds, the content is:

<table>

<tr>

</tr>

<tr>

<td>Same as input</td>

<td>Same as input</td>

</tr>

</table>

<table>

<tr>

</tr>

<tr>

</tr>

</table>

For the remaining 7 ±1 seconds, the values are:

<table>

<tr>

</tr>

<tr>

</tr>

</table>

<table>

<tr>

</tr>

<tr>

</tr>

</table> b. Repeat the steps in step ‘a’, except during the 5th second, cause the transponder to recognize a failure on the transponder/CAS interface (i.e. disconnect or otherwise interrupt the interface). The results should be the same as in step ‘a’.

c. Send ‘Active CAS with resolution capability’ (RI=3), CA operational = 1, hybrid surveillance capability, and the CAS version to the transponder via the transponder/CAS interface for 5 seconds.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Interrogate the transponder once per second for 30 seconds with UF=4 interrogations with RR=17, DI 7 and RRS=0.

Show that in the DF=20 Data Capability Report replies:

For the first 5 seconds, bits 43, 44, 45, 46, 71 and 72 indicate the correct CAS version, bit 48=1, bit 69=1, and bit 70=1.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

d. Repeat steps a., b. and c., this time using the following content as input:

<table>

<tr>

</tr>

<tr>

</tr>

</table>

The results should be the same as in test steps a., b. and c.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

a. Send the following content for the RA report to the transponder via the transponder/CAS interface once per second for 5 seconds:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

<table>

<tr>

</tr>

<tr>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

<table>

<tr>

</tr>

<tr>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Show that in the DF=20 RA report replies:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

For the first 5 seconds, the RA Report has the following content:

<table>

<tr>

</tr>

<tr>

<td>Same as input</td>

<td>Same as input</td>

</tr>

</table>

<table>

<tr>

</tr>

<tr>

<td>Same as input</td>

</tr>

</table>

For the next 18 ±1 seconds, the content is:

<table>

<tr>

</tr>

<tr>

<td>Same as input</td>

<td>Same as input</td>

</tr>

</table>

<table>

<tr>

</tr>

<tr>

<td>Same as input</td>

</tr>

</table>

For the remaining 7 ±1 seconds, the values are:

<table>

<tr>

</tr>

<tr>

</tr>

</table>

<table>

<tr>

</tr>

<tr>

</tr>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Show that in the DF=20 Data Capability Report replies:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

d. Repeat steps a., b. and c., this time using the following content as input:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

<table>

<tr>

</tr>

<tr>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

<table>

<tr>

</tr>

<tr>

</tr>

</table>

The results should be the same as in test steps a., b. and c.

[…]

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Introduction:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

5.8.1 Purpose and Definition (§3.31.1)

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

5.8.2 Data Requirement (§3.31.2)

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

b. Interrogate the transponder using GICB protocols as specified in §3.23.1.12.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

5.8.2.1 Data Field ‘y’ (§3.31.2.1)

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

c. For each ‘y’ parameter, verify that the transponder replies with an ‘MB’ field having:

(1). Each ‘y’ parameter encoded in the proper register location.

(2). Each ‘y’ parameter encoded in two’s complement arithmetic unless otherwise specified.

(3). Each ‘y’ parameter value properly rounded to preserve accuracy of ±½ LSB.

(4). Status bit for each applicable ‘y’ parameter set to ONE (1) if data is valid and set to ZERO (0) if data is invalid.

5.8.3 Update Rate (§3.31.3)

Change the data provided to the transponder and repeat the interrogation given in §5.8.2.1.b as necessary to complete the following steps:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

b. If the appropriate value required in ‘a’ above cannot be realized within twice the [Figure or form omitted from this preview — available in the Avioverse workspace library.]

5.8.4 Service Reporting (§3.31.4)

Change the data provided to the transponder and repeat the interrogation given in §5.8.2.1.b as necessary to complete the following steps:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

Note: The following procedure uses XY to define the register as opposed to XX used in §5.8.

Repeat all of §5.8.1 through §5.8.4 using the following interrogation.

<table>

<tr>

</td>

</tr>

<tr>

</tr>

<tr>

</td>

</tr>

</table>

<table>

<tr>

<td>Not Assigned =</td>

</tr>

<tr>

</tr>

</table>

[…]

APPENDIX B […]

Table B-2-1: GICB Register Number Assignments

<table>

<tr>

<td>Transponder Register Number</td>

<td>Assignment</td>

<td>Implementation Reference</td>

<td>Maximum update interval (Note 1)</td>

</tr>

<tr>

<td>

</td>

<td>Not valid</td>

<td>Not defined as a specific register, however corresponding protocol used to extract AICB and Comm-B Broadcast on Level 2</td> <td>N/A</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Linked Comm-B, segment 2</td>

<td>Level 2 with AICB Capability</td>

</tr>

<tr>

<td>

</td>

<td>Linked Comm-B, segment 3</td>

<td>Level 2 with AICB Capability</td>

</tr>

<tr>

<td>

</td>

<td>Linked Comm-B, segment 4</td>

<td>Level 2 with AICB Capability</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Airborne Position</td>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Surface Position</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from subnetwork version number 6)</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Identification and Category</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Airborne Velocity</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from ADS-B v3)</td>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from subnetwork version number 6)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Reserved for CAS</td>

</tr>

<tr>

<td>

</td>

<td>Data Link Capability Report</td>

<td>Level 2</td>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>Data Link Capability Report (extension)</td>

<td>Level 2 with Basic Dataflash</td>

</tr>

<tr>

<td>

</td>

<td>Reserved for extension to datalink capability reports</td>

</tr>

<tr>

<td>

</td>

<td>Common usage GICB Capability Report</td>

<td>Level 2</td>

</tr>

</table>

<table>

<tr>

<td>Transponder Register Number</td>

<td>Assignment</td>

<td>Implementation Reference</td>

<td>Maximum update interval (Note 1)</td>

</tr>

<tr>

<td>

</td>

<td>Mode S Specific Services Capability Reports (GICB Capability)</td>

<td>Level 2</td>

</tr>

<tr>

<td>

</td>

<td>Mode S Specific Services Capability Reports (MSP Capability)</td>

<td>Level 2</td>

</tr>

<tr>

<td>

</td>

<td>Aircraft Identification</td>

<td>Level 2</td>

</tr>

<tr>

<td>

</td>

<td>Aircraft and airline registration markings</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from subnetwork version number 6)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Aircraft type</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>CAS Active Resolution Advisory</td>

<td>Level 2 with CAS</td>

<td>1.0s (when RA active)</td>

</tr>

<tr>

<td>

</td>

<td>CAS Active Resolution Advisory (Part 2)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved for CAS</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Operational Coordination Message</td>

<td>1.0s (when RA active)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved for CAS</td>

</tr>

<tr>

<td>

</td>

<td>Selected vertical intention</td>

</tr>

<tr>

<td>

</td>

<td>Next waypoint identifier</td>

</tr>

<tr>

<td>

</td>

<td>Next waypoint position</td>

</tr>

<tr>

<td>

</td>

<td>Next waypoint information</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from subnetwork version number 6)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>VHF channel report</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Track and turn report</td>

</tr>

<tr>

<td>

</td>

<td>Position report coarse</td>

</tr>

<tr>

<td>

</td>

<td>Position report fine</td>

</tr>

<tr>

<td>

</td>

<td>Air-referenced state vector</td>

</tr>

<tr>

<td>

</td>

<td>Waypoint 1</td>

</tr>

<tr>

<td>

</td>

<td>Waypoint 2</td>

</tr>

<tr>

<td>

</td>

<td>Waypoint 3</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from subnetwork version number 6)</td>

</tr>

<tr>

<td>

</td>

<td>Heading and speed report</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Aircraft Status (Subtype 1: Emergency/Priority Status)</td> <td>ADS-B v1 – v3 (6)</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Target State and Status Information</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Aircraft Status (Subtype 4: UAS/RPAS Lost Link, Current TCP)</td> <td>ADS-B v3 (6)</td>

</tr>

</table>

<table>

<tr>

<td>Transponder Register Number</td>

<td>Assignment</td>

<td>Implementation Reference</td>

<td>Maximum update interval (Note 1)</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Aircraft Status (Subtype 4: UAS/RPAS Lost Link, Next TCP)</td> <td>ADS-B v3 (6)</td>

</tr>

<tr>

<td>

</td>

<td>Extended Squitter Aircraft Operational Status</td>

</tr>

<tr>

<td>

</td>

<td>IRM – Interrogation Rate Monitor</td>

</tr>

<tr>

<td>

</td>

<td>IRM – Reply Rate Monitor</td>

</tr>

<tr>

<td>

</td>

<td>ADS-B Wx AIREP (Subtype 0: Aircraft State)</td>

</tr>

<tr>

<td>

</td>

<td>ADS-B Wx AIREP (Subtype 1: Weather State)</td>

</tr>

<tr>

<td>

</td>

<td>ADS-B Wx AIREP (Subtype 2: Alternate Weather State)</td>

</tr>

<tr>

<td>

</td>

<td>ADS-B Wx PIREP (Subtype 0: Flight Weather)</td>

<td>Indefinite</td>

</tr>

<tr>

<td>

</td>

<td>ADS-B Wx PIREP (Subtype 1: Temp, Wind & Turbulence)</td>

<td>Indefinite</td>

</tr>

<tr>

<td>

</td>

<td>ADS-B Wx PIREP (Subtype 2: Hazardous Weather)</td>

<td>Indefinite</td>

</tr>

<tr>

<td>

</td>

<td>High Velocity and/or Altitude (Subtype 0: Position)</td>

</tr>

<tr>

<td>

</td>

<td>High Velocity and/or Altitude (Subtype 1: Velocity)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Interval Management Report</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>Transponder type/part number</td>

<td>Recommended in European CS-ACNS AMC1 ACNS.D.ELS.015</td>

</tr>

<tr>

<td>

</td>

<td>Transponder software revision number</td>

<td>Recommended in European CS-ACNS AMC1 ACNS.D.ELS.015</td>

</tr>

<tr>

<td>

</td>

<td>CAS unit part number</td>

<td>Level 2 with CAS</td>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>CAS unit software revision number</td>

<td>Level 2 with CAS</td>

<td>

</td>

</tr>

<tr>

<td>

</td>

<td>Transponder Status and Diagnostics</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Vendor Specific Status and Diagnostics</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

<tr>

<td>

</td>

<td>Reserved (Removed from subnetwork version number 6)</td>

</tr>

<tr>

<td>

</td>

<td>Reserved</td>

</tr>

</table>

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

1 The term ‘minimum update rate’ is used in this document. The minimum update rate is obtained when data is loaded in one Register field once every maximum update interval.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

6 ADS-B requirements are defined by state regulations including but not limited to [Figure or form omitted from this preview — available in the Avioverse workspace library.]

[…]

Table B-3-17: BDS Code 1,1 — Data Link Capability Report (extension)

MB FIELD

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

PURPOSE: To extend the reporting of data link capability of the Mode S transponder/data link installation. 1) See Table B-3-16a (BDS 1,0) Note 7. 2) Encoding of Monitoring bits for each Basic Dataflash Register shall be encoded as follows:

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

<table>

<tr>

<td colspan="3">Monitoring Bit Encoding</td>

</tr>

<tr>

<td>Meaning</td>

</tr>

<tr>

<td>Register is NOT monitored. (see §3.32.3.a and §3.32.4.f).</td>

</tr>

<tr>

<td>

</td>

</tr>

<tr>

<td rowspan="2">Register is monitored and data contents are changing such that the Monitoring Bits shall be toggled ‘10’, ‘11’, ‘10’, etc., each time the contents change in accordance with §3.32.4.b. through §3.32.4.e.</td> </tr>

<tr>

</tr>

</table>

3) These bits remain reserved for future system expansion needs. 4) Starting from the MSB, each subsequent bit position shall represent the DTE sub-address in the range of 0 to 15. 5) The current status of the on-board DTE shall be periodically reported to the GDLP by on-board sources. Since a change in this field results in a broadcast of the capability report, status inputs shall be sampled at approximately one minute intervals.

[Figure or form omitted from this preview — available in the Avioverse workspace library.]

[Amdt ETSO/11]

[Amdt ETSO/18]

APPENDIX · Appendix 1 to ETSO-C112f — CS-ETSO · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026

All rules in SUBPART B – LIST OF ETSOs

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.

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