ETSO-C166c

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

IRImplementing rule

ETSO-C166c

EXTENDED SQUITTER AUTOMATIC DEPENDENT SURVEILLANCE-BROADCAST (ADS-B) AND

TRAFFIC INFORMATION SERVICES-BROADCAST (TIS-B) EQUIPMENT OPERATING ON THE

RADIO FREQUENCY OF 1090 MEGAHERTZ (MHZ)

1 Applicability

This ETSO provides the requirements which Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Services-Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz) 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 EUROCAE ED-102B / RTCA DO-260C, ‘Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Services-Broadcast (TIS-B)’, as modified by Change 1, issued in January 2022, and as amended by Appendix 1 to this ETSO.

This ETSO supports two major classes of 1090 MHz ADS-B and TIS-B equipment:

(a)Class A equipment, consisting of transmit and receive subsystems; and

(b)Class B equipment, containing a transmit subsystem only.

Class A equipment includes Classes A0, A1, A1S, A2 and A3 as defined in EUROCAE ED-102B. This standard requires 1090 MHz airborne Class A equipment to include the capability of receiving both ADS-B and TIS-B messages and delivering both ADS-B and TIS-B reports, as well as transmitting ADS-B messages. A receive-only Class of equipment is allowed.

Class B equipment includes Classes B0, B1, and B1S. Classes B0, B1, and B1S are the same as A0, A1, and A1S, except they do not have receive subsystems. Note that Classes B2 and B3 are not for aircraft use.

3.1.2 Environmental standard

See CS-ETSO, Subpart A, paragraph 2.1. The required performance under test conditions is defined in EUROCAE ED-102B, Section 2.3. 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

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 loss of function is a minor failure condition at equipment level.

Note: The major failure condition for transmission of incorrect ADS-B messages is based on the use of the data by other aircraft or Air Traffic Control for separation services.

4 Marking

4.1 General

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

4.2 Specific

Transmitting and receiving components must be permanently and legibly marked in accordance with EUROCAE ED-102B, Section 2.1.11, ‘Equipage Class Definitions’, the receiving equipment type in accordance with Section 2.2.6, ‘ADS-B Receiving Device Message Processor Characteristics’ and Section 1.3.6 ‘optional additional features’.

5 Availability of referenced document

See CS-ETSO, Subpart A, paragraph 3.

[Amdt ETSO/11]

[Amdt ETSO/13]

[Amdt ETSO/18]

IR · ETSO-C166c — CS-ETSO · CS-ETSO Easy Access Rules · EAR revision 1 Oct 2026

AppendixAppendix

Appendix 1 to ETSO-C166cEASA MODIFICATIONS TO EUROCAE ED-102B / RTCA DO-260C

Show the text

Purpose This appendix lists EASA modifications to EUROCAE ED-102B / RTCA DO-260C. Text added to modify EUROCAE ED-102B / RTCA DO-260C 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-102B sections. Due to the extensive modifications, Section 2.4.5.2.12 is included as a complete change. Excerpts from EUROCAE ED-102B / RTCA DO-260C are reprinted with the permission of EUROCAE and RTCA Inc. All rights reserved. […]

2.4.3.2.7.6.4.4 Verification of ‘Wind Speed’ Subfield in ADS-B Wx Weather State Messages (§2.2.3.2.7.6.4.4) This test procedure is used to verify that the ADS-B Transmitting Subsystem correctly encodes the ‘Wind Speed’ subfield in the Weather State Message as a dynamic value from a variable data input.

Table 2-240: ‘Wind Speed’ Subfield Encoding Test Values

<table>

<tr>

<td colspan="2">Coding</td>

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

</tr>

<tr>

<td>(Binary)</td>

<td>(Decimal)</td>

</tr>

<tr>

<td>

</td>

<td>

</td>

<td>

</td>

</tr>

<tr>

<td>0 ≤ Wind Speed [kts] < 1</td>

</tr>

<tr>

<td>1 ≤ Wind Speed [kts] < 2</td>

</tr>

<tr>

<td>3 ≤ Wind Speed [kts] < 4</td>

</tr>

<tr>

<td>7 ≤ Wind Speed [kts] < 8</td>

</tr>

<tr>

<td>15 ≤ Wind Speed [kts] < 16</td>

</tr>

<tr>

<td>31 ≤ Wind Speed [kts] < 32</td>

</tr>

<tr>

<td>63 ≤ Wind Speed [kts] < 64</td>

</tr>

<tr>

<td>127 ≤ Wind Speed [kts] < 128</td>

</tr>

<tr>

<td>253 ≤ Wind Speed [kts] < 254</td>

</tr>

<tr>

<td>254 ≤ Wind Speed [kts]</td>

</tr>

</table>

Measurement Procedure:

f. Provide an updated ‘Wind Speed’ subfield value to the ADS-B Transmitting Subsystem input interface. Verify that the ‘Wind Speed’ subfield for subsequent Weather State Messages is set to the updated value within 100 milliseconds of the data being made available to the input interface.

2.4.3.2.7.6.4.5 Verification of ‘Wind Direction’ Subfield in ADS-B Wx Weather State Messages (§2.2.3.2.7.6.4.5) This test procedure is used to verify that the ADS-B Transmitting Subsystem correctly encodes the ‘Wind Direction’ subfield in the Weather State Message as a dynamic value from a variable data input.

Table 2-241: ‘Wind Direction’ Subfield Encoding

<table>

<tr>

<td colspan="2">Coding</td>

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

</tr>

<tr>

<td>(Binary)</td>

<td>(Decimal)</td>

</tr>

<tr>

<td>

</td>

<td>

</td>

<td>

</td>

</tr>

<tr>

<td>0.000 ≤ Wind Direction [degrees] < 0.352</td>

</tr>

<tr>

<td>0.352 ≤ Wind Direction [degrees] < 0.704</td>

</tr>

<tr>

<td>1.056 ≤ Wind Direction [degrees] < 1.408</td>

</tr>

<tr>

<td>2.463 ≤ Wind Direction [degrees] < 2.815</td>

</tr>

<tr>

<td>5.279 ≤ Wind Direction [degrees] < 5.630</td>

</tr>

<tr>

<td>10.909 ≤ Wind Direction [degrees] < 11.261</td>

</tr>

<tr>

<td>22.170 ≤ Wind Direction [degrees] < 22.522</td>

</tr>

<tr>

<td>44.692 ≤ Wind Direction [degrees] < 45.044</td>

</tr>

<tr>

<td>89.736 ≤ Wind Direction [degrees] < 90.088</td>

</tr>

<tr>

<td>179.824 ≤ Wind Direction [degrees] < 180.176</td>

</tr>

<tr>

<td>359.296 ≤ Wind Direction [degrees] < 359.648</td>

</tr>

<tr>

<td>359.648 ≤ Wind Direction [degrees] < 360.000</td>

</tr>

</table>

Measurement Procedure:

Step 1: Conduct variable data input tests a. Configure the ADS-B system as for installed operation b. Power on the ADS-B system and perform start-up procedures (§2.2.3.3.2.1) c. Operate the ADS-B system so as to broadcast Airborne Position Messages (§2.2.3.3.2.2). d. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Wind Speed’ and ‘Wind Direction’ subfields. e. For each ‘Wind Direction’ decimal value in Table 2-241, verify that the system generates Weather State Messages with the ‘Wind Direction’ subfield in each such message set equal to the binary coding value corresponding to the decimal value tested. f. Provide an updated ‘Wind Direction’ subfield value to the ADS-B Transmitting Subsystem input interface. Verify that the ‘Wind Direction’ subfield for subsequent Weather State Messages is set to the updated value within 100 milliseconds of the data being made available to the input interface.

2.4.3.2.7.6.4.6 Verification of ‘Air Temperature Type’ Subfield in ADS-B Wx Weather State Messages (§2.2.3.2.7.6.4.6) This test procedure is used to verify that the ADS-B Transmitting Subsystem correctly encodes the ‘Air Temperature Type’ subfield in the Weather State Message, as either a preconfigured, static value or as a dynamic value based on variable data input(s). It also verifies the encoding of ‘Air Temperature Type’ in the Alternate Weather State Message.

Note: This test procedure assumes ‘Air Temperature Type’ may be preconfigured, provided explicitly, or may be determined from the provision of Total Air Temperature data or Static Air Temperature data. If one or more method is not supported, the test steps associated with that method may be omitted.

Measurement Procedure:

Step 1: Conduct preconfigured data tests a. Configure the ADS-B system as for installed operation, preconfiguring the Weather State Message, ‘Air Temperature Type’ subfield with decimal value ‘0’ (binary 0) in Table 2-90, as appropriate per §2.2.3.2.7.6.4.6. b. Power on the ADS-B system and perform start-up procedures (§2.2.3.3.2.1). c. Operate the ADS-B system so as to broadcast Airborne Position Messages (§2.2.3.3.2.2). d. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Wind Speed’ and ‘Wind Direction’ subfields. e. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Air Temperature Type’ subfield set to the preconfigured value. f. Perform Steps 1.a through 1.e, substituting the untested ‘Air Temperature Type’ decimal value ‘1’ (binary 1) in Table 2-90 for the ‘0’ in Step 1.a. g. Perform Steps 1.a through 1.c. h. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Roll Angle’ subfield. i. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Air Temperature Type’ subfield set to the preconfigured value. j. Perform Steps 1.a through 1.c and 1.h, substituting the untested ‘Air Temperature Type’ decimal value ‘1’ (binary 1) in Table 2-90 for the ‘0’ in Step 1.a. k. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Air Temperature Type’ subfield set to the preconfigured value.

Step 2: Conduct variable data input tests for dynamic, explicitly provided Air Temperature Type variable input a. Perform Steps 1.b through 1.d b. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature Type’ subfield in the form of ‘Air Temperature Type’ data set to decimal ‘0’ (binary 0) c. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘0’ (binary 0). d. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature Type’ subfield in the form of ‘Air Temperature Type’ data set to decimal ‘1’ (binary 1). e. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘1’ (binary 1). f. Provide an updated ‘Air Temperature Type’ subfield value to the ADS-B Transmitting Subsystem input interface. Verify that the ‘Air Temperature Type’ subfield for subsequent Weather State Messages is set to the updated value within 100 milliseconds of the data being made available to the input interface. g. Perform Steps 1.b and 1.c and 1.h. h. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature Type’ subfield in the form of ‘Air Temperature Type’ data set to decimal ‘0’ (binary 0). i. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘0’ (binary 0). j. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature Type’ subfield in the form of ‘Air Temperature Type’ data set to decimal ‘1’ (binary 1). k. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘1’ (binary 1). l. Provide an updated ‘Air Temperature Type’ subfield value to the ADS-B Transmitting Subsystem input interface. Verify that the ‘Air Temperature Type’ subfield for subsequent Alternate Weather State Messages is set to the updated value within 100 milliseconds of the data being made available to the input interface.

Step 3: Conduct variable data input tests for determining Air Temperature Type from variable input of Total Air Temperature data a. Perform Steps 1.b through 1.d b. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature’ subfield in the form of ‘Total Air Temperature’ data only. c. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘0’ (binary 0). d. Provide an updated ‘Air Temperature’ subfield value to the ADS-B Transmitting Subsystem input interface in the form of Static Air Temperature. Verify that the ‘Air Temperature Type’ subfield for subsequent Weather State Messages is set to decimal ‘1’ (binary 1) within 100 milliseconds of the data being made available to the input interface. e. Perform Steps 1.b and 1.c. f. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature’ subfield in the form of ‘Total Air Temperature’ data only. g. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘0’ (binary 0). h. Provide an updated ‘Air Temperature’ subfield value to the ADS-B Transmitting Subsystem input interface in the form of Static Air Temperature. Verify that the ‘Air Temperature Type’ subfield for subsequent Alternate Weather State Messages is set to decimal ‘1’ (binary 1) within 100 milliseconds of the data being made available to the input interface.

Step 4: Conduct variable data input tests for determining Air Temperature Type from variable input of Static Air Temperature data

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

Step 5: Conduct variable data input tests for determining Air Temperature Type from variable input of both Total Air Temperature data and Static Air Temperature data a. Perform Steps 1.b through 1.d b. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature’ subfield in the form of both ‘Total Air Temperature’ data, and ‘Static Air Temperature’. c. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘1’ (binary 1). d. Perform Steps 1.b and 1.c. e. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Air Temperature’ subfield in the form of both ‘Total Air Temperature’ data and ‘Static Air Temperature’ data. f. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Air Temperature Type’ subfield in each such message set to decimal ‘1’ (binary 1).

[…]

2.4.3.2.7.6.4.8 Verification of ‘Airspeed Type’ Subfield in ADS-B Wx Weather

State Messages (§2.2.3.2.7.6.4.8)

This test procedure is used to verify that the ADS-B Transmitting Subsystem correctly encodes the ‘Airspeed Type’ subfield in the Weather State Message, as either a preconfigured, static value or as a dynamic value based on variable data input(s). It also verifies the encoding of ‘Airspeed Type’ in the Alternate Weather State Message.

Note: This test procedure assumes ‘Airspeed Type’ may be preconfigured, provided explicitly, or may be determined from the provision of Indicated Airspeed data or True Airspeed data. If one or more method is not available, the test steps associated with that method may be omitted.

Measurement Procedure:

Step 1: Conduct preconfigured data tests a. Configure the ADS-B system as for installed operation, preconfiguring the Weather State Message, ‘Airspeed Type’ subfield with decimal value ‘0’ (binary 0) in Table 2-92, as appropriate per §2.2.3.2.7.6.4.8. b. Power on the ADS-B system and perform start-up procedures (§2.2.3.3.2.1). c. Operate the ADS-B system so as to broadcast Airborne Position Messages (§2.2.3.3.2.2).

d. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Wind Speed’ and ‘Wind Direction’ subfields. e. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Airspeed Type’ subfield set to the preconfigured value. f. Perform Steps 1.a through 1.e, substituting the untested ‘Airspeed Type’ decimal value ‘1’ (binary 1) in Table 2-92 for the ‘0’ in Step 1.a. g. Perform Steps 1.a through 1.c. h. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Roll Angle’ subfield. i. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield set to the preconfigured value. j. Perform Steps 1.a through 1.c and 1.h, substituting the untested ‘Airspeed Type’ decimal value ‘1’ (binary 1) in Table 2-92 for the ‘0’ in Step 1.a. k. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield set to the preconfigured value.

Step 2: Conduct variable data input tests for dynamic, explicitly provided Airspeed Type variable input a. Perform Steps 1.b through 1.d. b. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed Type’ subfield in the form of ‘Airspeed Type’ data set to decimal ‘0’ (binary 0). c. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘0’ (binary 0). d. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed Type’ subfield in the form of ‘Airspeed Type’ data set to decimal ‘1’ (binary 1). e. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘1’ (binary 1). f. Provide an updated ‘Airspeed Type’ subfield value to the ADS-B Transmitting Subsystem input interface. Verify that the ‘Airspeed Type’ subfield for subsequent Weather State Messages is set to the updated value within 100 milliseconds of the data being made available to the input interface. g. Perform Steps 1.b and 1.c and 1.h h. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed Type’ subfield in the form of ‘Airspeed Type’ data set to decimal ‘0’ (binary 0).

i. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘0’ (binary 0). j. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed Type’ subfield in the form of ‘Airspeed Type’ data set to decimal ‘1’ (binary 1). k. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘1’ (binary 1). l. Provide an updated ‘Airspeed Type’ subfield value to the ADS-B Transmitting Subsystem input interface. Verify that the ‘Airspeed Type’ subfield for subsequent Alternate Weather State Messages is set to the updated value within 100 milliseconds of the data being made available to the input interface.

Step 3: Conduct variable data input tests for determining Airspeed Type from variable input of Indicated Airspeed data a. Perform Steps 1.b through 1.d. b. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed’ subfield in the form of ‘Indicated Airspeed’ data only. c. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘0’ (binary 0). d. Provide an updated ‘Airspeed’ subfield value to the ADS-B Transmitting Subsystem input interface in the form of True Airspeed. Verify that the ‘Airspeed Type’ subfield for subsequent Weather State Messages is set to decimal ‘1’ (binary 1) within 100 milliseconds of the data being made available to the input interface. e. Perform Steps 1.b and 1.c. f. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed’ subfield in the form of ‘Indicated Airspeed’ data only. g. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘0’ (binary 0). h. Ensure that the ‘Air Temperature Type’ subfield is set to ‘Static Air Temperature’. Provide an updated ‘Airspeed’ subfield value to the ADS-B Transmitting Subsystem input interface in the form of True Airspeed. Verify that the ‘Airspeed Type’ subfield for subsequent Alternate Weather State Messages is set to decimal ‘1’ (binary 1) within 100 milliseconds of the data being made available to the input interface.

Step 4: Conduct variable data input tests for determining Airspeed Type from variable input of True Airspeed data a. Perform Steps 1.b through 1.d.

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

Step 5: Conduct variable data input tests for determining Airspeed Type from variable input of both Indicated Airspeed data and True Airspeed data a. Perform Steps 1.b through 1.d. b. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed’ subfield in the form of both ‘Indicated Airspeed’ data and ‘True Airspeed’ data. c. Verify that the ADS-B Transmitting Subsystem transmits Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘1’ (binary 1). d. Perform Steps 1.b and 1.c. e. Ensure that the ‘Air Temperature Type’ subfield is set to ‘Static Air Temperature’. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed’ subfield in the form of both ‘Indicated Airspeed’ data and ‘True Airspeed’ data. f. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘1’ (binary 1). g. Ensure that the ‘Air Temperature Type’ subfield is set to ‘Total Air Temperature’. Provide variable input data to the ADS-B Transmitting Subsystem at the nominal update rate for the ‘Airspeed’ subfield in the form of both ‘Indicated Airspeed’ data and ‘True Airspeed’ data. h. Verify that the ADS-B Transmitting Subsystem transmits Alternate Weather State Messages with the ‘Airspeed Type’ subfield in each such message set to decimal ‘0’ (binary 0).

[…]

2.4.3.2.7.8.1.6 Verification of ‘Peak EDR Offset’ Subfield in Emergency / Priority Status Messages (§2.2.3.2.7.8.1.6)

Purpose/Introduction:

If supporting the ADS-B Wx AIREP option, this test procedure is used to verify that the ADS-B Transmitting Subsystem correctly encodes the ‘Peak EDR Offset’ subfield in the Emergency / Priority Status Message as a dynamic value from a variable data input. The test procedures in §2.4.3.3.2.6.3 verify that encodings other than ‘NO or INVALID Data’ occur only when Airborne Position Messages are being broadcast. If ADS-B Wx AIREPs are not supported, this test verifies that the ‘Peak EDR Offset’ subfield is set to ALL ZEROs.

Measurement Procedure:

If NOT implementing ADS-B Wx AIREP:

Configure the ADS-B Transmitting Subsystem to transmit Airborne Position Messages. Set the ADS-B Transmitting Subsystem to Airborne status. Produce valid Airborne Position Messages at the nominal rate with valid position and altitude data. Verify that the ADS-B Transmitting Subsystem begins to transmit Extended Squitter Aircraft Status Messages at the nominal rate with the TYPE Subfield set to 28 (binary 1 1100) and the Subtype Subfield set to ONE (binary 001). Verify that the ‘Peak EDR Offset’ subfield (‘ME’ bits 40 – 42; Message bits 72 – 74) is set to ALL ZEROs.

If implementing ADS-B Wx AIREP:

Conduct variable data input tests

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

[…]

2.4.3.3.2.3 Verification of ADS-B Surface Position Message Broadcast Rate

(§2.2.3.3.2.3)

Purpose/Introduction:

This test verifies the Surface Position broadcast rates. Broadcast rates for 1090 MHz Extended Squitter ADS-B Messages are summarized in Table 2-128.

Equipment Required:

Provide a method of loading valid data for broadcasting ADS-B Messages into the ADS-B equipment under test. Provide a method of monitoring the transmitted ADS-B Messages and measuring the rate at which they are output.

Measurement Procedure:

Step 1: Broadcast Rate (§2.2.3.3.2.3.a, b and c)

Ensure that the equipment is set to the ‘On-Ground’ condition and that the appropriate valid ADS-B Surface Position data are available such that the position data is initiated and changes such that the position reflects an increased displacement from the initial position of 1 meter each second.

After 15 seconds, verify that the ADS-B Surface Position Messages are broadcast at random intervals that are uniformly distributed over the range of 0.4 to 0.6 seconds using a time quantization no greater than 15 milliseconds as specified in §2.2.3.3.2.3.b.

Provide position and movement data to the ADS-B equipment such that the position is stationary. Note the initial time that the position data is no longer changing. After 15 minutes and 10 seconds from the start of the input of stationary position data, verify that the ADS-B Surface Position Messages are broadcast at random intervals that are uniformly distributed over the range of 4.8 to 5.2 seconds using a time quantization no greater than 15 milliseconds as specified in §2.2.3.3.2.3.c.

Provide position data such that the position is moving 10 meters per minute and note the time the input changes from stationary to moving. After 61 seconds from the change from stationary position to moving, verify that the ADS-B Surface Position Messages are broadcast at random intervals that are uniformly distributed over the range of 0.4 to 0.6 seconds.

Step 2: Initiation, Timeout, and Termination (§2.2.3.3.2.1.2, §2.2.3.3.2.11.b, §2.2.3.3.2.12.b) Ensure that the equipment is set to the ‘On-Ground’ condition. Input Movement and Heading / Ground Track, but do not input position. Verify that Surface Position Messages are not broadcast.

Cease input of Movement and Heading / Ground Track. Input position with a simulated movement at a rate high enough to result in a ‘High’ broadcast rate. Verify that Surface Position messages are initiated.

Input all data for the Surface Position Messages. Stop the input of position data, but continue with data sufficient to populate the Movement and Heading / Ground Track subfields.

Verify that the Surface Position Messages broadcast within 2.6 seconds after stopping the data input have all data bits set to the last reported valid value. Verify that Surface Position Messages broadcast more than 2.6 seconds after stopping the data input have all data bits set to ZERO. Verify that the ADS-B Surface Position Messages cease to be broadcast 60 seconds from stopping the position input.

Note: The 60 second termination does not apply to Non-Transponder

Devices.

Resume input of position data and stop the input of Movement data. Verify that the Surface Position Messages broadcast within 2.6 seconds after stopping the data input have the Movement subfield set to the last reported valid value. Verify that Surface Position Messages broadcast more than 2.6 seconds after stopping the data input have the Movement subfield set to ZERO with all other subfields correctly populated.

Resume input of Movement data and stop the input of Heading / Ground Track data. Verify that the Surface Position Messages broadcast within 2.6 seconds after stopping the data input have the Heading / Ground Track subfield set to the last reported valid value. Verify that Surface Position Messages broadcast more than 2.6 seconds after stopping the data input have the Heading / Ground Track subfield set to ZERO with all other subfields correctly populated.

Note: It is acceptable to validate the data in the subsequent Surface

Position Message received after the indicated time has elapsed.

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

2.4.3.3.2.4 Verification of ADS-B Aircraft Identification and Category Message Broadcast Rate (§2.2.3.3.2.4) Purpose/Introduction:

This test verifies the Aircraft Identification and Category broadcast rates. Broadcast rates for 1090 MHz Extended Squitter ADS-B Messages are summarized in Table 2-128.

Equipment Required:

Provide a method of loading valid data for ADS-B broadcast messages into the ADS-B equipment under test. Provide a method of monitoring the transmitted ADS-B Messages and measuring the rate at which they are output.

Measurement Procedure:

Step 1: Broadcast Rate (§2.2.3.3.2.4)

Ensure that the equipment is set to the ‘Airborne’ condition and that the appropriate valid Aircraft Identification and Category data are available. Verify that the Aircraft Identification and Category Messages are broadcast at random intervals that are uniformly distributed over the range of 4.8 to 5.2 seconds using a time quantization no greater than 15 milliseconds as specified in §2.2.3.3.2.4.a.

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

Note: It is acceptable to validate the data in the subsequent

Aircraft Identification and Category Message received after the indicated time has elapsed.

Step 2: Initiation, Timeout, and Termination (§2.2.3.3.2.1.2, §2.2.3.3.2.11.d, §2.2.3.3.2.12.c) Reset the ADS-B device. Input only ADS-B Emitter Category data. Verify that the Aircraft Identification and Category Messages are initiated.

Stop the input of data. At least 60 seconds later, verify that the Aircraft Identification and Category Messages continue to be broadcast with the same data that existed prior to stopping the data input.

Reset the ADS-B system. Input only Aircraft Identification data. Verify that the Aircraft Identification and Category Messages are initiated.

[…]

2.4.3.3.2.6.1 Verification of ADS-B Target State and Status Message Broadcast Rates (§2.2.3.3.2.6.1) Purpose/Introduction:

This test verifies the Target State and Status broadcast rates. Broadcast rates for 1090 MHz Extended Squitter ADS-B Messages are summarized in Table 2-128.

Equipment Required:

Provide a Method of loading valid data for ADS-B broadcast messages into the ADS-B equipment under test. Provide a method of monitoring the transmitted ADS-B Messages and measuring the rate at which they are output.

Measurement Procedure:

Step 1: Broadcast Rate (§2.2.3.3.2.6.1)

Ensure that the equipment is set to the ‘Airborne’ condition and that the appropriate valid Target State and Status data are available. Verify that the Target State and Status Messages are broadcast at random intervals that are uniformly distributed over the range of 1.2 to 1.3 seconds using a time quantization no greater than 15 milliseconds as specified in §2.2.3.3.2.6.1.

Step 2: Initiation, Timeout, and Termination (§2.2.3.3.2.1.2, §2.2.3.3.2.11.e, §2.2.3.3.2.12.e) Provide the ADS-B Transmitting Subsystem with valid data necessary for the generation of Target State and Status Messages and Surface Position Messages. Ensure that the equipment is set to the ‘On-Ground’ condition. Verify that Target State and Status Messages are not broadcast.

Discontinue the input of Selected Altitude, Selected Heading, and BPS data. Ensure that the equipment is set to the ‘Airborne’ condition. Generate Airborne Position messages. Verify that Target State and Status Messages are not broadcast.

Input valid Selected Altitude data. Verify that Target State and Status Messages are initiated.

Discontinue input of Selected Altitude data. Verify that the Target State and Status Messages cease to be broadcast 2.6 seconds after stopping the data input.

Input valid Selected Heading data. Verify that the Target State and Status Messages are initiated.

Discontinue input of Selected Heading data. Verify that the Target State and Status Messages cease to be broadcast 2.6 seconds after stopping the data input.

Input valid BPS data. Verify that the Target State and Status Messages are initiated. Discontinue input of BPS data. Verify that the Target State and Status Messages cease to be broadcast 2.6 seconds after stopping the data input.

Input valid Target State and Status data, and discontinue Airborne Position Message broadcast (e.g. no position or altitude data provided to the system). Verify that the ADS-B Transmitting Subsystem is not broadcasting any ADS-B Target State and Status Messages.

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

Note: It is acceptable to validate the data in the subsequent Target State and Status Message received after the indicated time has elapsed.

[…]

2.4.3.3.2.6.3 Verification of ADS-B Emergency/Priority Status Message Broadcast Rate (§2.2.3.3.2.6.3) Purpose/Introduction:

This test verifies the Emergency/Priority Status Message broadcast rates. Broadcast rates for 1090 MHz Extended Squitter ADS-B Messages are summarized in Table 2-128.

Equipment Required:

Measurement Procedure:

Step 1: Broadcast Rate (§2.2.3.3.2.6.3)

Ensure that appropriate valid Emergency/Priority Status Message data are available. Verify that the Emergency/Priority Status Messages are broadcast at random intervals that are uniformly distributed over the range of 4.8 to 5.2 seconds using a time quantization no greater than 15 milliseconds as specified in §2.2.3.3.2.6.3.b.

Input a Mode A Code of 1000. Verify that the Emergency/Priority Status Messages are broadcast at random intervals that are uniformly distributed over the range of 0.7 to 0.9 seconds using a time quantization no greater than 15 milliseconds seconds as specified in §2.2.3.3.2.6.3.a. Verify that the Emergency/Priority Status Messages return to the nominal rate 24 ±1 seconds after changing the data.

Input a Mode A Code of 7400. Verify that the Emergency/Priority Status Messages are broadcast at random intervals that are uniformly distributed over the range of 0.7 to 0.9 seconds using a time quantization no greater than 15 milliseconds seconds as specified in §2.2.3.3.2.6.3.a. At least 60 seconds after changing the Mode A Code, verify that the Emergency/Priority Status Messages remain at the higher rate.

Input a Mode A Code of 1000. After the Emergency/Priority Status Message reverts to the low broadcast rate, input a Mode A Code of 7500. At least 60 seconds after changing the Mode A Code to 7500, verify that the Emergency/Priority Status Messages are broadcast at the higher rate.

Input a Mode A Code of 1000. After the Emergency/Priority Status Message reverts to the low broadcast rate, input a Mode A Code of 7600. At least 60 seconds after changing the Mode A Code to 7600, verify that the Emergency/Priority Status Messages are broadcast at the higher rate.

Input a Mode A Code of 1000. After the Emergency/Priority Status Message reverts to the low broadcast rate, input a Mode A Code of 7700. At least 60 seconds after changing the Mode A Code to 7700, verify that the Emergency/Priority Status Messages are broadcast at the higher rate.

Input a Mode A Code of 1000. After the Emergency/Priority Status Message reverts to the low broadcast rate, input an Emergency/Priority Status of decimal 6. At least 60 seconds after changing the Emergency/Priority Status, verify that the Emergency/Priority Status Messages are broadcast at the higher rate.

Step 2: Initiation, Timeout, and Termination (§2.2.3.3.2.1.2, §2.2.3.3.2.11.i, §2.2.3.3.2.12.g) Provide the ADS-B Transmitting Subsystem with only Emergency/Priority Status data. Verify that the Emergency/Priority Status Message is initiated.

Discontinue input of Emergency/Priority Status data. At least 60 seconds later, verify that the Emergency/Priority Status Messages continue to be broadcast.

Reset the ADS-B Transmitting Subsystem. Provide the ADS-B Transmitting Subsystem with only Mode A Code data. Verify that the Emergency/Priority Status Message is initiated.

Reset the ADS-B Transmitting Subsystem. Provide the ADS-B Transmitting Subsystem with Mode A Code data and with Manned/Unmanned Operation data setting the subfield to ONE (binary 1). Verify that the Emergency/Priority Status Message is initiated.

Discontinue input of Mode A Code and Manned/Unmanned Operation data. At least 60 seconds later, verify that the Emergency/Priority Status Messages continue to be broadcast with the same Mode A Code data as was previously input and with the Manned/Unmanned Operation subfield set to ONE (binary 1).

If implementing support for the optional ADS-B Wx AIREP Messages, the following additional tests apply:

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

Reset the ADS-B Transmitting Subsystem. Operate the ADS-B system so as to broadcast Surface Position Messages. Provide the ADS-B Transmitting Subsystem, additionally, with Peak EDR data only. Verify that the Emergency/Priority Status Message is not initiated. Provide the ADS-B Transmitting Subsystem with Mode A Code data in addition to Peak EDR data. Verify that the Emergency/Priority Status Message is initiated and that [Figure or form omitted from this preview — available in the Avioverse workspace library.]

Note: It is acceptable to validate the data in the subsequent

Emergency/Priority Status Message received after the indicated time has elapsed.

[…]

2.4.5.2.4 Verification of Airborne Velocity Message – Subtype=1 Latency (§2.2.5.2.4, §2.2.3.2.6.1) Purpose/Introduction:

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

Measurement Procedure:

Step 1: Airborne Velocity Message - Subtype=1 – ‘TYPE’ Subfield (§2.2.3.2.6.1.1 and §2.2.5.2.4) Configure the ADS-B Transmitting Subsystem to transmit Airborne Velocity Messages – Subtype=1 by providing subsonic velocity information at the nominal update rate. Provide the data externally at the interface to the ADS-B system. Set the ADS-B Transmitting Subsystem to Airborne status. Provide valid non-zero subsonic velocity data to the ADS-B System. Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged. Verify that the TYPE subfield in the Airborne Velocity Message – Subtype=1 equals 19, which is the only TYPE value assigned to Airborne Velocity Messages.

Step 2: Airborne Velocity Message - Subtype=1 – ‘Subtype’ Subfield (§2.2.3.2.6.1.2 and §2.2.5.2.4) Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged. Increase the velocity data input to the ADS-B System to a supersonic value so that the change occurs at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the ‘Subtype’ subfield value has changed to TWO (2) in the next transmitted Airborne Velocity Message.

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

Step 4: Airborne Velocity Message - Subtype=1 – ‘East/West Direction Bit’ Subfield (§2.2.3.2.6.1.6 and §2.2.5.2.4) Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged. Verify that the East/West Direction Bit equals Zero (0). Insert changed data to the ADS-B System to cause a change to occur in the East/West Direction Bit so that the direction will become ‘West’ and so that the change is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the East/West Direction Bit subfield value has changed to ONE (1) in the next transmitted Airborne Velocity Message.

Step 5: Airborne Velocity Message - Subtype=1 – ‘East/West Velocity’ Subfield (§2.2.3.2.6.1.7 and §2.2.5.2.4) Configure the ADS-B Transmitting Subsystem to transmit Airborne Velocity Messages – Subtype=1 by providing subsonic velocity information at the nominal update rate. Provide the data externally at the interface to the ADS-B system. Set the ADS-B Transmitting Subsystem to Airborne status. Provide valid non-zero subsonic East/West Velocity data to the ADS-B System. Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged.

Insert changed data to the ADS-B System to cause a change to occur in the East/West Velocity so that it is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the East/West Velocity subfield value has changed in the next transmitted Airborne Velocity Message and that the value in the subfield is correct.

Step 6: Airborne Velocity Message - Subtype=1 – ‘North/South Direction Bit’ Subfield (§2.2.3.2.6.1.8 and §2.2.5.2.4) [Figure or form omitted from this preview — available in the Avioverse workspace library.]

Step 7: Airborne Velocity Message - Subtype=1 – ‘North/South Velocity’ Subfield (§2.2.3.2.6.1.9 and §2.2.5.2.4) [Figure or form omitted from this preview — available in the Avioverse workspace library.]

Step 8: Airborne Velocity Message - Subtype=1 – ‘Vertical Rate Source Bit’ Subfield (§2.2.3.2.6.1.10 and §2.2.5.2.4) a. Continue transmitting Airborne Velocity Messages - Subtype=1 at the [Figure or form omitted from this preview — available in the Avioverse workspace library.]

Step 9: Airborne Velocity Message - Subtype=1 – ‘Sign Bit for Vertical Rate’ Subfield (§2.2.3.2.6.1.11 and §2.2.5.2.4) a. Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged. Verify that the ‘Sign Bit for Vertical Rate’ subfield equals ZERO (0), indicating Vertical Rate information in the UP Direction. Insert changed data to the ADS-B System to cause a change to occur in the ‘Sign Bit for Vertical Rate’ so that the Vertical Direction information will be DOWN, and so that the change is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the ‘Sign Bit for Vertical Rate’ subfield value has changed to ONE (1) in the next transmitted Airborne Velocity Message. b. Continue transmitting Airborne Velocity Messages – Subtype=1 at the nominal rate with all parameters unchanged and verify that the ‘Sign Bit for Vertical Rate’ subfield contains the value of ONE (1). Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged. Insert changed data to the ADS-B System to cause a change to occur in the ‘Sign Bit for Vertical Rate’ so that the Vertical Direction information will be UP, and so that the change is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the ‘Sign Bit for Vertical Rate’ subfield value has changed to ZERO (0) in the next transmitted Airborne Velocity Message.

Step 10: Airborne Velocity Message - Subtype=1 – ‘Vertical Rate’ Subfield

(§2.2.3.2.6.1.12 and §2.2.5.2.4)

Configure the ADS-B Transmitting Subsystem to transmit Airborne Velocity Messages – Subtype=1 by providing subsonic velocity information at the nominal update rate. Provide the data externally at the interface to the ADS-B system. Set the ADS-B Transmitting Subsystem to Airborne status. Provide valid non zero Vertical Rate data to the ADS-B System. Continue transmitting Airborne Velocity Messages - Subtype=1 at the nominal rate with all parameters unchanged.

Insert changed data to the ADS-B System to cause a change to occur in the Vertical Rate so that it is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the Vertical Rate subfield value has changed in the next transmitted Airborne Velocity Message and that the value in the subfield is correct.

Step 11: Airborne Velocity Message - Subtype=1 – ‘Extended Difference From

Barometric Altitude Sign Bit’ Subfield (§2.2.3.2.6.1.14 and §2.2.5.2.4)

Configure the ADS-B Transmitting Subsystem to transmit Airborne Velocity Messages - Subtype=1 by providing subsonic velocity information at the nominal update rate, including non-zero Barometric and Geometric Altitude data. Provide the data externally at the interface to the ADS-B system. Ensure that the ‘Extended Difference From Barometric Altitude Sign Bit’ subfield equals ZERO (0), indicating geometric altitude source data is greater than or equal to barometric. Insert changed data to the ADS-B System to cause a change to occur in the ‘Extended Difference From Barometric Altitude Sign Bit’ so that the geometric altitude source data is less than barometric, and so that the change is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the ‘Extended Difference From Barometric Altitude Sign Bit’ subfield value has changed to ONE (1) in the next transmitted Airborne Velocity Message.

Step 12: Airborne Velocity Message - Subtype=1 – ‘Extended Difference From

Barometric Altitude’ Subfield (§2.2.3.2.6.1.15 and §2.2.5.2.4)

Configure the ADS-B Transmitting Subsystem to transmit Airborne Velocity Messages – Subtype=1 at the nominal rate with all parameters unchanged. Insert data to the ADS-B System to cause a change to occur in the Extended Difference From Barometric Altitude so that it is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the Extended Difference From Barometric Altitude subfield value has changed in the next transmitted Airborne Velocity Message and that the value in the subfield is correct.

Step 13: Airborne Velocity Message - Subtype=1 – ‘NIC Supplement-D’ Subfield

(§2.2.3.2.6.1.16 and §2.2.5.2.4)

Set the ADS-B Transmitting Subsystem to Airborne Status. Continue transmitting Airborne Velocity Messages – Subtype=1 at the nominal rate.

For Type Codes=20 & 22, insert changed data to the ADS-B System to cause a change to occur in the NIC Supplement-D subfield, so that the change is detected at least 100 milliseconds prior to the next scheduled Airborne Velocity Message transmission. Verify that the value in the NIC Supplement-D subfield equals the corresponding value in the NIC Supplement-D column in the applicable row of Table 2-28.

[…]

2.4.5.2.12 Verification of Aircraft Operational Status Message Latency (§2.2.3.2.7.2, §2.2.5.2.12) [Figure or form omitted from this preview — available in the Avioverse workspace library.]

APPENDIX · Appendix 1 to ETSO-C166c — 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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