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Appendix 1 to ETSO-C199 A1 - Traffic Awareness Beacon System (TABS) Requirements

Available versions for ERULES-1963177438-18166

ED Decision 2020/011/R found in: CS-ETSO Amdt 17 - European Technical Standard Orders (Oct 2026)

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###### Appendix 1 to ETSO-C199 A1 – Traffic Awareness Beacon System (TABS) Requirements

*ED
Decision
2020/011/R*

**A1
Introduction**

**A1.1
TABS Intent**

A1.1.1
The intent of a TABS is to increase safety by encouraging the
voluntary equipage of a low-cost, compact, easy-to-install device
that will allow other aircraft equipped with collision avoidance
systems and traffic advisory systems to track and display the TABS
aircraft. TABSs are intended to be used on aircraft that are exempted
from carrying a transponder or Automatic Dependent Surveillance —
Broadcast (ADS-B) equipment, such as gliders, balloons and aircraft
without electrical systems. TABS devices do not meet the transponder
requirements defined in Commission Implementing Regulation (EU) No
1207/2011 of 22 November 2011 laying down requirements for the
performance and the interoperability of surveillance for the single
European sky. A TABS will allow these exempted aircraft to be visible
to other aircraft equipped with:

1. a Traffic Advisory System (TAS) as defined in ETSO-C147();

2. a Traffic Alert and Collision Avoidance System I (TCAS I) as
defined in ETSO‑C118();

3. a Traffic Alert and Collision Avoidance System II, (TCAS II), as
defined in ETSO‑C119d;

4. ADS-B IN capability as defined in ETSO-C166b, and ETSO-C195b; or

5. ADS-B IN capability as defined in ETSO-C154c in airspace where UAT
is used.

A1.1.2 A TABS is designed to:

6. reply to ATCRBS Mode C, and Mode S UF=0, 4, 5, 20 and 21
interrogations;

7. not reply to ATCRBS Mode A interrogations;

8. not reply to Mode S UF=11, and 16 interrogations;

9. incorporate ETSO-C88b, Automatic Pressure Altitude Reporting
Code-Generating Equipment;

10. transmit ADS-B Messages: Aircraft Identification and Category,
Airborne Position, Airborne Velocity, Emergency Priority Status
Message, and Aircraft Operational Status;

11. optionally provide Surface Position Messages;

12. optionally use a commercial GNSS source meeting the requirements
of this ETSO.

A1.1.3
A TABS can potentially act as a low-cost platform for other aviation
applications. Although additional capabilities are beyond the scope
of this ETSO, TABSs may include additional functions such as data
loggers, search and rescue transmitter, or provide flight information
services.

**A1.2
Requirements**

A1.2.1
TABS requirements are derived from existing Mode S transponder and
1090 MHz Extended Squitter ADS-B requirements. A designer who builds
equipment to meet this ETSO may decide to incorporate the full
transponder and ADS-B capability by using a device that meets
ETSO-C112e and ETSO-C166b. If they elect to implement the full
functionality, they must demonstrate that functionality against the
unmodified test procedures in EUROCAE ED-102A, including
Corrigendum‑1, dated January, 2012, that are required by
ETSO-C112e and ETSO-C166b respectively. Designers who wish to take
advantage of the reduced transponder requirements afforded to
ETSO‑C199 Class A devices must meet the modified requirements
outlined in paragraphs A1.2.3 Transponder Function Requirements,
A1.2.4 Altitude Source Function Requirements, and A1.2.5 ADS-B OUT
Function Requirements in this Appendix in their entirety. Designers
wishing to take advantage of the Class B reduced GNSS requirements
will need to meet the requirements outlined in paragraphs A1.2.6 GNSS
Position Source Function Requirements.

A1.2.2
MOPS text is used here with the permission of the RTCA. Table 1
provides notes in italics and parenthesis explaining how to read the
tables that modify the text in the source documents.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
(Source
			document reference)
</td>
<td bgcolor="#808080">
Modified
			text for this ETSO
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
(This
			is a copy of the original text from the source document. Material
			to be deleted from this original text is marked with <strike>strikethrough
			formatting</strike>.)
</td>
<td bgcolor="#d9d9d9">
(This
			is the requirement for this ETSO. Modifications to the source text
			are marked in bold and underlined to assist in
			identifying changes).
</td>
</tr>
</table>

***Table
1 — (Source document
reference) (type of change)***

A1.2.3
Transponder Function Requirements Derived From DO-181E (For Class A
Devices)

A1.2.3.1
The transponder function must meet the Minimum Performance Standards
(MPS) qualification and documentation requirements in RTCA, Inc.
document RTCA document DO-181E, Section 2, for a Level 2, Class 2,
transponder as modified below.

A1.2.3.1.1
Flight Crew Control Function Changes

A1.2.3.1.2
A cost factor in any device is the control and display functions to
interface with the human operator. TABS display and control
requirements are a subset of those required for transponders. Some
user controls are allowed via an external device prior to flight
(e.g., a personal electronic device (PED)). If the system is powered
by batteries, display of the available battery life is recommended.
Table 2 provides an overview of the flight crew control
functions.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
Operation
			mode 

</td>
<td bgcolor="#808080">
Required
			Controls 

</td>
<td bgcolor="#808080">
Required
			Indicators 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
In
			flight 

(i.e.,
			control head) 

</td>
<td bgcolor="#d9d9d9">
-
			Power, 


-
			Emergency (3/A code 7700), 

-
			IDENT (optional) 

</td>
<td bgcolor="#d9d9d9">
Power
			on, 


Transponder
			Fail, 


ADS-B
			Fail, 

Battery
			indicator (optional) 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Non-flight
			(optional in flight) 

(i.e.,
			Personal Electronic Device PED) 

</td>
<td bgcolor="#d9d9d9">
-
			Set 4096 code, 

-
			Set Flight ID 

</td>
<td bgcolor="#d9d9d9">
Display
			of 4096 code, 

Display
			of Flight ID 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Maintenance
			actions (allowed in non-flight conditions only) 

</td>
<td bgcolor="#d9d9d9">
-
			Set ICAO 24-bit aircraft address, 

-
			Set implementation specific configuration 

</td>
<td bgcolor="#d9d9d9">
Display
			of ICAO 24-bit aircraft address, 


Display
			of implementation specific configuration. 

Display
			software version (optional) 

</td>
</tr>
</table>

***Table
2 — Summary of Control and
Indication Requirements by Operation Mode***

A1.2.3.1.3
RTCA document DO-181E, Section 2.1.7.a, Flight Crew Control
Functions, is amended as shown in Table 3.

***Table
3 — DO-181E Section
2.1.7.a amendment***

A1.2.3.1.4
RTCA document DO-181E, Section 2.1.7.b, Flight Crew Control
Functions, is amended as shown in Table 4.

***Table
4 — DO-181E Section
2.1.7.b amendment***

A1.2.3.1.5
RTCA document DO-181E, Section 2.1.7.c, Flight Crew Control
Functions, is amended as shown in Table 5.

***Table
5 — DO-181E Section
2.1.7.c amendment***

A1.2.3.1.6
RTCA document DO-181E, Section 2.1.7.d, Flight Crew Control
Functions, is amended as shown in Table 6.

***Table
6 — DO-181E Section
2.1.7.d amendment***

A1.2.3.2
Reply Rate Capability Changes

A1.2.3.2.1
This section reduces the minimum reply rate capability of the TABS
consistently with the interrogation acceptance based on two
assumptions. The following rationale describes how the modified reply
rates were chosen.

A1.2.3.2.1.1
Assumption 1. The worst-case Mode C interrogation count in a
100-millisecond interval from 1 ATCRBS radar is approximately 14
interrogations. 4 ATCRBS radar overlapping beam dwells in 1 second is
approximately 53 Mode C interrogations. The Mode C interrogation
acceptance rate from 10 TCAS I units is approximately 15
interrogations per second. This represents a total demand on the TABS
of 68 Mode C replies per second for this example.

A1.2.3.2.1.2
Assumption 2. The worst-case Mode S reply rate is primarily derived
from the expected interrogation pattern of a set of 50 nearby TCAS II
units all equipped with hybrid surveillance. The radar load from only
roll-call interrogations would be small and would require networked
sensors, otherwise the Mode S ground interrogation acceptance rate
from radar systems would be 0 (zero).

A1.2.3.2.2
Based on assumptions 1 and 2, RTCA document DO-181E Section 2.2.3.4
Reply Rate Capability is changed as follows:

A1.2.3.2.2.1
RTCA document DO-181E, Section 2.2.3.4.1.a, ATCRBS Reply Rate
Capability, is amended as shown in Table 7.

***Table
7 — DO-181E Section
2.2.3.4.1.a amendment***

A1.2.3.2.2.2
RTCA document DO-181E, Section 2.2.3.4.1.c, ATCRBS Reply Rate
Capability, is amended as shown in Table 8.

***Table
8 — DO-181E Section
2.2.3.4.1.c added***

A1.2.3.2.2.3
RTCA document DO-181E, Section 2.2.3.4.2.a, Mode S Reply Rate
Capability, is amended as shown in Table 9.

***Table
9 — DO-181E Section
2.2.3.4.a amendment***

A1.2.3.2.2.4
RTCA document DO-181E, Section 2.2.3.4.2.b, Mode S Reply Rate
Capability, is amended as shown in Table 10.

***Table
10 — DO-181E Section
2.2.3.4.2.b amendment***

A1.2.3.3
Reply Rate Limiting Changes

A1.2.3.3.1
The modifications in this section address reply rate limiting for
ATCRBS and Mode S reply rates consistently with the previous section.

A1.2.3.3.2
RTCA document DO-181E, Section 2.2.7.3.1, ATCRBS Reply Rate Limiting,
is amended as shown in Table 11.

***Table
11 — DO-181E Section
2.2.7.3.1 amendment***

A1.2.3.4
RTCA document DO-181E, Section 2.2.13.1.2.c, Variable Direct Data, is
amended as shown in Table 12.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
			text 

</td>
<td bgcolor="#808080">
Modified
			text for this ETSO 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
c.
			On-the-Ground Condition

The
			transponder <strike>Shall</strike> report the
			automatically determined on-the-ground state as determined by the
			aircraft in the Flight Status (FS), Vertical Status (VS), and
			Capability (CA) fields (see §2.2.14.4.15, §2.2.14.4.42, and
			§2.2.14.4.6), except when reporting airborne status when
			on-the-ground is reported to the transponder under the conditions
			specified in §2.2.18.2.7. 

</td>
<td bgcolor="#d9d9d9">
c.
			On-the-Ground Condition 

The
			transponder may report the automatically determined
			on-the-ground state as determined by the aircraft in the Flight
			Status (FS), Vertical Status (VS), and Capability (CA) fields (see
			paragraphs 2.2.14.4.15, 2.2.14.4.42, and 2.2.14.4.6), except when
			reporting airborne status when on-the-ground is reported to the
			transponder under the conditions specified in paragraph
			2.2.18.2.7. 

</td>
</tr>
</table>

***Table
12 — DO-181E Section
2.2.13.1.2.c amendment***

A1.2.3.5
RTCA document DO-181E, Section 2.2.13.1.2.d, Variable Direct Data, is
amended as shown in Table 13.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
			text 

</td>
<td bgcolor="#808080">
Modified
			text for this ETSO 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
d.
			Special Position Identification (SPI)
<strike>In
			the ATCRBS mode, an SPI pulse </strike><strike>Shall</strike><strike>
			be transmitted upon request, following a Mode A reply</strike>. In
			the FS field of Mode S replies, an equivalent of the ATCRBS SPI
			pulse Shall be transmitted upon <strike>the same request</strike>.
			The code is transmitted for 18 ±1.0 seconds after initiation and
			can be reinitiated at any time.
</td>
<td bgcolor="#d9d9d9">
d.
			Special Position Identification (SPI)
In
			the FS field of Mode S replies, an equivalent of the ATCRBS SPI
			pulse shall be transmitted upon request if the
			optional IDENT flight crew control is implemented per A1.2.3.1.6
			of this ETSO. The code is transmitted for 18 ± 1.0
			seconds after initiation and can be reinitiated at any time.
</td>
</tr>
</table>

***Table
13 — DO-181E Section
2.2.13.1.2.d amendment***

A1.2.3.6
RTCA document DO-181E, Section 2.2.13.1.2.e, Variable Direct Data, is
amended as shown in Table 14.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
			text 

</td>
<td bgcolor="#808080">
Modified
			text for this ETSO 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
e.
			Aircraft Identification Data
If
			the aircraft uses a flight number for aircraft identification, a
			means Shall be provided for the variable aircraft
			identification to be inserted by the pilot while on the ground<strike>,
			or during flight. The means for modifying and displaying aircraft
			identification </strike><strike>Shall</strike><strike> be a
			simple crew action independent of the entry of other flight data.</strike>
</td>
<td bgcolor="#d9d9d9">
e.
			Aircraft Identification Data
If
			the aircraft uses a flight number for aircraft identification, a
			means SHALL be provided for the variable aircraft
			identification to be inserted by the pilot while on the ground. A
			means may be provided for modifying aircraft identification in
			flight.

</td>
</tr>
</table>

***Table
14 — DO-181E Section
2.2.13.1.2.e amendment***

A1.2.3.7
Interrogation Acceptance Protocol Changes (All-Call reply capability)

A1.2.3.7.1
The transponder All-Call interrogation reply acceptance requirements
are reduced to reply only to ATCRBS Mode C (P1-P3) interrogations.
The purpose is to reduce the reply rate of TABS while maintaining
TCAS and TAS interoperability. The requirements of this ETSO are
identical to RTCA document DO-181E except for the changes shown
below.

A1.2.3.7.2
RTCA document DO-181E, Section 2.2.18.2.2.b, Interrogation Acceptance
Protocol (Figure 2-12), is amended as shown in Table 15.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
			text 

</td>
<td bgcolor="#808080">
Modified
			text for this ETSO 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
All-Call
			Address – If the address extracted from the received
			interrogation consists of 24 ONEs and UF=11, the transmission is a
			Mode S-Only All-Call and the received interrogation Shall be
			accepted <strike>according to “i” below unless the lockout
			protocol is in effect. Mode S-Only All-Call Shall not be accepted
			(no replies) when in the on-the-ground state (consistent with the
			CA, VS and FS fields)</strike>
</td>
<td bgcolor="#d9d9d9">
All-Call
			Address – If the address extracted from the received
			interrogation consists of 24 ONEs and UF=11, the transmission is a
			Mode S-Only All-Call and the received interrogation SHALL not
			be accepted.
</td>
</tr>
</table>

***Table
15 — DO-181E Section
2.2.18.2.2.b amendment***

A1.2.3.7.3
RTCA document DO-181E, Section 2.2.18.2.2.c, Interrogation Acceptance
Protocol (Figure 2-12), is amended as shown in Table 16.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<thead>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
				text
</td>
<td bgcolor="#808080">
Modified
				text for this ETSO
</td>
</tr>
</thead>
<tbody>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS/Mode
				S All-Call – An ATCRBS/Mode S All-Call interrogation (1.6
				microseconds P4) Shall be <strike>accepted unless the TD timer is
				running or side lobe suppression is in effect or when in the
				“on-the-ground” state (consistent with the CA, VS and FS
				fields).</strike>

</td>
<td bgcolor="#d9d9d9">
ATCRBS/Mode
				S All-Call – An ATCRBS/Mode S All-Call interrogation (1.6
				microseconds P4) SHALL not be accepted. 

</td>
</tr>
</tbody>
</table>

***Table
16 — DO-181E Section
2.2.18.2.c amendment***

A1.2.3.8
RTCA document DO-181E, Section 2.2.18.2.2.g, Interrogation Acceptance
Protocol, paragraph g, All-Call Lockout Conditions, is amended as
shown in Table 17.

***Table
17 — DO-181E Section
2.2.18.2.g amendment***

A1.2.3.9
RTCA document DO-181E, Section 2.2.18.2.2.i, Interrogation Acceptance
Protocol Stochastic All‑Calls, should not be implemented in
Class A TABS.

A1.2.3.10
Two new sections are added here to explicitly define interrogation
acceptance criteria for TABS.

A1.2.3.10.1
RTCA document DO-181E, Section 2.2.18.2.2.L, Interrogation Acceptance
Protocol (Figure 2-12), is added as shown in Table 18.

***Table
18 — DO-181E Section
2.2.18.2.2L addition***

A1.2.3.10.2
RTCA document DO-181E, Section 2.2.18.2.2.m, Interrogation Acceptance
Protocol (Figure 2-12), is added to as shown in Table 19. This change
reduces the range at which addressed Mode S ground interrogations
would be replied to. The intent is to reduce the reply rate of the
TABS. Sensitivity to TCAS interrogations is not affected.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<thead>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
				text
</td>
<td bgcolor="#808080">
Modified
				text for this ETSO
</td>
</tr>
</thead>
<tbody>
<tr valign="top">
<td bgcolor="#d9d9d9">
None
				

</td>
<td bgcolor="#d9d9d9">
Ground-to-Air
				Mode S Acceptance – Mode S interrogations, excluding
				UF=0 SHALL be accepted at the Mode S MTL (paragraph 2.2.2.4 b)
				+3dB ± 1dB. 

</td>
</tr>
</tbody>
</table>

***Table
19 — DO-181E Section
2.2.18.2.2.m addition***

A1.2.3.11
RTCA document DO-181E, Section 2.2.18.2.3, Interrogation Reply
Coordination, is amended as shown in Table 20.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080" colspan="2">
DO-181E
			text
</td>
<td bgcolor="#808080" colspan="2">
Modified
			text for this ETSO
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9" colspan="2">
The
			transponder SHALL generate replies as follows, except when in the
			on-the-ground state:
</td>
<td bgcolor="#d9d9d9" colspan="2">
The
			transponder SHALL generate replies as follows, except when in the
			on‑the‑ground state:
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Interrogations
</td>
<td bgcolor="#d9d9d9">
Replies
</td>
<td bgcolor="#d9d9d9">
Interrogations
</td>
<td bgcolor="#d9d9d9">
Replies
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS
			Mode A 

</td>
<td bgcolor="#d9d9d9">
4096
			Codes 

</td>
<td bgcolor="#d9d9d9">
ATCRBS
			Mode A 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not reply 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS
			Mode C 

</td>
<td bgcolor="#d9d9d9">
Altitude
			Codes 

</td>
<td bgcolor="#d9d9d9">
ATCRBS
			Mode C 

</td>
<td bgcolor="#d9d9d9">
Altitude
			Codes 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS
			Mode A/Mode S All-Call 

</td>
<td bgcolor="#d9d9d9">
Reply
			is DF=11 

</td>
<td bgcolor="#d9d9d9">
ATCRBS
			Mode A/Mode S All-Call 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not Reply 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS
			Mode C/Mode S All-Call 

</td>
<td bgcolor="#d9d9d9">
Reply
			is DF=11 

</td>
<td bgcolor="#d9d9d9">
ATCRBS
			Mode C/Mode S All-Call 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not Reply 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Mode
			S-only All-Call (UF=11) 

</td>
<td bgcolor="#d9d9d9">
Reply
			is DF=11 

</td>
<td bgcolor="#d9d9d9">
Mode
			S-only All-Call (UF=11) 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not Reply 

</td>
</tr>
</table>

***Table
20 — DO-181E Section
2.2.18.2.3 amendment***

A1.2.3.12
RTCA document DO-181E, Section 2.2.18.2.4, Lockout Protocol, should
not be implemented in Class A TABS.

A1.2.3.13 RTCA document DO-181E, Section 2.2.18.2.5, Multisite
Lockout Protocol, should not be implemented in Class A TABS.

A1.2.3.14 RTCA document DO-181E, Section 2.2.18.2.7, Flight Status
and Vertical Status Protocols, is amended as shown in Table 21.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
			text 

</td>
<td bgcolor="#808080">
Modified
			text for this ETSO 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Mode
			S-equipped aircraft Shall report details of their flight status.
			The source of and the rules for such reports are as follows:
a.
			Alert – The transponder Shall transmit the 4096 identification
			code <strike>in ATCRBS Mode A replies</strike> and in the ID field
			of downlink format DF=5. <strike>This code can be changed by the
			pilot, and</strike> when a change is made an alert condition Shall
			be established. If the identification code is changed to 7500,
			7600 or 7700, the alert condition Shall be permanent. If the
			identification code is changed to any other value, the alert
			condition Shall be temporary and self-canceling after 18 ± 1
			seconds (TC timer). The TC timer Shall be retriggered and
			continued for 18 ± 1 seconds after any change has been
			accepted by the transponder function. The alert condition Shall be
			reported in the FS field. The permanent alert condition Shall be
			terminated and replaced by a temporary alert condition when the
			identification code is set to a value other than 7500, 7600 or
			7700.
</td>
<td bgcolor="#d9d9d9">
Mode
			S-equipped aircraft SHALL report details of their flight status.
			The source of and the rules for such reports are as follows:
a.
			Alert – The transponder SHALL transmit the 4096 identification
			code in the ID field of downlink format DF=5. When a change is
			made an alert condition SHALL be established. If the
			identification code is changed to 7500, 7600 or 7700, the alert
			condition SHALL be permanent. If the identification code is
			changed to any other value, the alert condition SHALL be temporary
			and self-cancelling after 18 ± 1 seconds (TC timer). The TC
			timer SHALL be retriggered and continued for 18 ± 1 seconds
			after any change has been accepted by the transponder function.
			The alert condition SHALL be reported in the FS field. The
			permanent alert condition SHALL be terminated and replaced by a
			temporary alert condition when the identification code is set to a
			value other than 7500, 7600 or 7700. 

</td>
</tr>
</table>

***Table
21 — DO-181E Section
2.2.18.2.7 amendment***

A1.2.3.15
RTCA document DO-181E, Section 2.2.18.2.9, All-Call Reply Protocol,
should not be implemented in Class A TABS.

A1.2.3.16
RTCA document DO-181E, Section 2.2.19.1, Minimum Level 2 Transponder
Requirements, is amended as shown in Table 22.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
DO-181E
			text
</td>
<td bgcolor="#808080">
Modified
			text for this ETSO
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
The
			operational functions described in §1.4.3.2 require that this
			transponder Shall, in addition to the functions of the Level 1
			transponder: 


a.
			Process uplink and downlink formats DF=16, UF=DF=20 and 21 (Figure
			2-14). The format UF=16 <strike>is optional.</strike>

<strike>Note:
			UF=16 is supported by transponders connected to an on-board
			operational TCAS (see §2.2.22). </strike>


<strike>b.
			Receive broadcast transmissions from sensors (§2.2.19.1.11). </strike>


c.
			Follow the protocols for: 


<strike>Comm-A
			(see §2.2.19.1.10). </strike>


Comm-B
			(see §2.2.19.1.12). 


<strike>Comm-U/V
			(air-air) (see §2.2.19.1.16). </strike>


<strike>Multisite
			message operation (see §2.2.19.2). </strike>


Report
			Codes 4 through 7 in the CA field (see §2.2.14.4.6). 

TCAS
			crosslink capability (see §2.2.19.1.18).
</td>
<td bgcolor="#d9d9d9">
The
			operational functions described in paragraph 1.4.3.2 require that
			this transponder SHALL, in addition to the functions of the Level
			1 transponder: 


a.
			Process uplink and downlink formats DF=16, UF=DF=20 and 21 (Figure
			2-14).

The
			format UF=16 SHALL not be accepted. TABS SHALL not be
			installed with an on-board TCAS system. 


b.
			Requirement Deleted.


c.
			Follow the protocols for: 


Comm-B
			(see paragraph 2.2.19.1.12.1 through 2.2.19.1.12.3). 


Report
			Codes 4 through 7 in the CA field (see paragraph 2.2.14.4.6). 

TCAS
			crosslink capability (see paragraph 2.2.19.1.18). 

</td>
</tr>
</table>

***Table
22 — DO-181E Section
2.2.19.1 amendment***

A1.2.3.17
RTCA document DO-181E, Section 2.2.19.1.3, Information Transfer,
should not be implemented in Class A TABS.

A1.2.3.18
RTCA document DO-181E, Section 2.2.19.1.4, Interrogation-Reply
Coordination, is amended per Table 23. Equipment using Minimum Level
2 Transponder Requirements, SHALL follow the text in DO-181E as
written.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080" colspan="2">
DO-181E
			text
</td>
<td bgcolor="#808080" colspan="2">
Modified
			text for this ETSO
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9" colspan="2">
The
			transponder SHALL generate replies to interrogations as follows:
</td>
<td bgcolor="#d9d9d9" colspan="2">
The
			transponder SHALL generate replies to interrogations as follows:
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Interrogation
			

</td>
<td bgcolor="#d9d9d9">
Reply
			

</td>
<td bgcolor="#d9d9d9">
Interrogation
			

</td>
<td bgcolor="#d9d9d9">
Reply
			

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS
			Mode A (see Note) 

</td>
<td bgcolor="#d9d9d9">
<strike>4096
			code</strike>
</td>
<td bgcolor="#d9d9d9">
ATCRBS
			Mode A (see Note) 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not reply 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS
			Mode C (see Note) 

</td>
<td bgcolor="#d9d9d9">
Altitude
			Code
</td>
<td bgcolor="#d9d9d9">
ATCRBS
			Mode C (see Note) 

</td>
<td bgcolor="#d9d9d9">
Altitude
			Code 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
ATCRBS/Mode
			S All-Calls (see Note) 

</td>
<td bgcolor="#d9d9d9">
<strike>DF
			= 11 </strike>

</td>
<td bgcolor="#d9d9d9">
ATCRBS/Mode
			S All-Calls (see Note) 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not reply 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
UF=4
			and UF=5 

</td>
<td bgcolor="#d9d9d9">
as
			below
</td>
<td bgcolor="#d9d9d9">
UF=4
			and UF=5 

</td>
<td bgcolor="#d9d9d9">
as
			below 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
UF=11
			(see Note) 

</td>
<td bgcolor="#d9d9d9">
<strike>DF
			= 11</strike>
</td>
<td bgcolor="#d9d9d9">
UF=11
			(see Note) 

</td>
<td bgcolor="#d9d9d9">
SHALL
			not reply 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
UF=20
			and UF=21 

</td>
<td bgcolor="#d9d9d9">
as
			below
</td>
<td bgcolor="#d9d9d9">
UF=20
			and UF=21 

</td>
<td bgcolor="#d9d9d9">
as
			below 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
Broadcast
			

</td>
<td bgcolor="#d9d9d9">
None
</td>
<td bgcolor="#d9d9d9">
Broadcast
			

</td>
<td bgcolor="#d9d9d9">
None
			

</td>
</tr>
</table>

***Table
23 — DO-181E Section
2.2.19.1.4 amendment***

A1.2.3.19
The Lockout Protocol described in RTCA document DO-181E, Section
2.2.19.1.5, should not be implemented in Class A TABS.

A1.2.3.20
The UM Protocol described in RTCA document DO-181E, Section
2.2.19.1.9, should not be implemented in Class A TABS.

A1.2.3.21
The Comm-A Protocol described in RTCA document DO-181E, Section
2.2.19.1.10, should not be implemented in Class A TABS.

A1.2.3.22
The Broadcast Protocol described in RTCA document DO-181E, Section
2.2.19.1.11, should not be implemented in Class A TABS.

A1.2.3.23
The Air-Initiated Comm-B Protocol described in RTCA document DO-181E,
Section 2.2.19.1.12.4, should not be implemented in Class A TABS.

A1.2.3.24
The Comm-B Broadcast Protocol described in RTCA document DO-181E,
Section 2.2.19.1.12.5, should not be implemented in Class A TABS.

A1.2.3.25
The Updating the Data Link Capability Report described in RTCA
document DO-181E, Section 2.2.19.1.12.6.3, should not be implemented
in Class A TABS.

A1.2.3.26
The Change of Aircraft Identification described in RTCA document
DO-181E, Section 2.2.19.1.13.e, should not be implemented in Class A
TABS.

A1.2.3.27
Linked Comm-A Coding described in RTCA document DO-181E, Section
2.2.19.1.14, should not be implemented in Class A TABS.

A1.2.3.28
The Comm-U/V Protocol described in RTCA document DO-181E, Section
2.2.19.1.16, should not be implemented in Class A TABS.

A1.2.3.29
The Data Handling Interfaces described in RTCA document DO-181E,
Section 2.2.19.1.17, should not be implemented in Class A TABS.

A1.2.3.30
The Multisite Message Protocol described in RTCA document DO-181E,
Section 2.2.19.2, should not be implemented in Class A TABS.

A1.2.3.31
Surveillance Identifier (SI) requirements contained in RTCA document
DO-181E, Section 2.2.24.2, should not be implemented in Class A TABS.

A1.2.3.32
The Elementary Surveillance (ELS) Compliant Transponder requirements
in RTCA document DO-181E, Section 2.2.24, do not apply to TABS
equipment. TABS SHALL not claim ELS compliance. Changes made to ELS
registers do not need to be indicated via a Comm-B broadcast. If one
or more of the ELS registers are supported, then Section 2.2.24
requirements SHALL apply except Sections 2.2.24 b 4, 2.2.24 c,
2.2.24.2, 2.2.24.3.2.5, and 2.2.24.3.4, which do not apply.

A1.2.3.33
The Enhanced Surveillance (EHS) Compliant Transponders requirements
in RTCA/DO-181E, Section 2.2.25, do not apply to TABS. TABS equipment
SHALL not claim EHS compliance. Changes made to EHS registers do not
need to be indicated via a Comm-B broadcast. If one or more of the
EHS registers are supported, then Section 2.2.25 requirements SHALL
apply except Sections 2.2.25.1.2.4 and 2.2.25.2.3, which do not
apply. Also, Section 2.2.25, paragraph 6 ‘Transponder capable of
supporting EHS…’, must support ELS per A1.2.3.32 of this ETSO.

A1.2.4
Altitude Source Function Requirements (For Class A Devices)

A1.2.4.1
The altitude source function shall meet the performance requirements
of ETSO-C88b, Automatic Pressure Altitude Reporting Code-Generating
Equipment, dated 5 August 2016. It is recommended that the altitude
source provide 25 ft or better resolution.

A1.2.5
ADS-B OUT Function Requirements Derived From EUROCAE ED-102A,
including Corrigendum-1, (For Class A Devices)

A1.2.5.1
The ADS-B OUT function must be 1090 Extended Squitter (ES) OUT, to
support TCAS surveillance. The 1090ES OUT function must meet the
Minimum Performance Standards (MPS) qualification and documentation
requirements in EUROCAE ED-102A, MOPS for 1090 MHz Extended Squitter
Automatic Dependent Surveillance – Broadcast (ADS-B) and Traffic
Information Services – Broadcast (TIS-B), dated December, 2009,
including Corrigendum-1, Section 2, dated January, 2012, for a Class
B0 ADS-B OUT transmitter with the following modifications.

A1.2.5.2
EUROCAE ED-102A, including Corrigendum-1, Section 2, dated January,
2012, Paragraph 2.2.2.1.c, Mode S Transponder Based Transmitters, is
amended as shown in Table 24.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
ED-102A
			text 

</td>
<td bgcolor="#808080">
Modified
			text for this ETSO 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
If
			the ADS-B transmitter is based on Mode S transponders, then for
			transponder functions it Shall comply with RTCA/DO-181D (EUROCAE
			ED-73C) for each class of transponder specified in the latest
			version of FAA TSO C112 (ETSO 2C112)
</td>
<td bgcolor="#d9d9d9">
<strike>If
			the ADS-B transmitter is based on Mode S transponders, then for</strike>
The transponder functions SHALL comply with RTCA/DO-181E
			(EUROCAE ED-73E) for each class of transponder
			specified in the latest version of ETSO-C112 (FAA TSO C112),
			except where modified by Appendix 1 to this
			ETSO.
</td>
</tr>
</table>

***Table
24 — ED-102A Section
2.2.2.1.c amendment***

A1.2.5.3
The output power SHALL be as specified in EUROCAE ED-102A, including
Corrigendum-1, dated January, 2012, Section 2.2.2.2.10.1.a., for
Class A0 and B0 equipment. The RF Peak Output power SHALL be at least
18.5 dBW (70 watts).

A1.2.5.4
Broadcast of the ADS-B Surface Position Messages defined in EUROCAE
ED-102A including Corrigendum-1, Section 2.2.3.2.4, is optional.

A1.2.5.5
EUROCAE ED-102A including Corrigendum-1, Section 2.2.3.2.7.2,
Aircraft Operational Status Messages, is amended as shown in Table
25.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
ED-102A
			text
</td>
<td bgcolor="#808080">
Modified
			text for this ETSO
</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
The
			‘Aircraft Operational Status Message’ is used to provide the
			current status of the aircraft. The format of the Aircraft
			Operational Status Message shall be as specified in Figure 2-11,
			while further definition of each of the subfields is provided in
			the subsequent paragraphs. 

</td>
<td bgcolor="#d9d9d9">
The
			‘Aircraft Operational Status Message’ is used to provide the
			current status of the aircraft. The format of the Aircraft
			Operational Status Message shall be as specified in Figure 2-11,
			while further definition of each of the subfields is provided in
			the subsequent paragraphs. Broadcast of Aircraft Operational
			Status Message subtype=1, Surface Messages, is optional.

</td>
</tr>
</table>

***Table
25 — Aircraft Operational
Status Message***

A1.2.5.6
When TABS is installed with a position source meeting the Class B
requirements of this ETSO and transmitting a valid position, the
transmitted NIC SHALL be set to 6 (0.5 NM), reference EUROCAE ED-102A
including Corrigendum-1, dated January 2012, Section 2.2.8.1.16. The
transmitted SIL SHALL be set to 1 (1×1E-3/ h), reference EUROCAE
ED-102A including Corrigendum-1, dated January 2012, Section
2.2.5.1.40. When TABS is installed with a position source compliant
with ETSO-C145, ETSO-C146 or ETSO-C196, NIC and SIL SHALL be set in
accordance with EUROCAE ED-102A including Corrigendum-1, dated
January, 2012. When the position is not valid, NIC and SIL SHALL be
set to 0 (zero).

A1.2.5.7
The System Design Assurance (SDA), SHALL be set to 1, reference
EUROCAE ED-102A, including Corrigendum-1, dated January 2012, Section
2.2.5.1.50. The probability of an undetected fault causing
transmission of false or misleading information SHALL be less than or
equal to 1E-3.

A1.2.5.8
Navigation Accuracy Category for Position, (NACp) SHALL be derived
from the Horizontal Figure of Merit (HFOM) in accordance with EUROCAE
ED-102A, including Corrigendum-1, dated January 2012, Section
A.1.4.9.9; however, TABS Class B position sources may not provide
HFOM directly. When HFOM is not available directly, HFOM SHALL be
derived from Horizontal Dilution of Precision (HDOP) according to the
following formula: HFOM = 2 \* HDOP \* User Equivalent Range Error
(UERE), where the UERE is 6 metres. This UERE is based on typical
single frequency (L1) receiver performance and an assumption of
mid-latitude atmospheric propagation. Although the real-time UERE may
fluctuate, this assumption is sufficient to support the TABS use
case. (Ref. Global Positioning System Signals, Measurements and
Performance, by Pratap Misra and Per Enge, copyright 2001).

A1.2.5.9 When a TABS is installed with a position source meeting the
Class B requirements of this ETSO and transmitting a valid position,
the transmitted Navigation Accuracy Category for Velocity, (NACv)
SHALL be set to 1 (10 m/s), reference EUROCAE ED-102A including
Corrigendum-1, dated January, 2012, Section 2.2.5.1.19. When position
is not valid, NACv SHALL be set to 0 (zero).

A1.2.5.10 Geometric Vertical Accuracy (GVA) SHALL be derived from
Vertical Figure of Merit, (VFOM) in accordance with EUROCAE ED-102A
including Corrigendum-1, dated January, 2012, Section 2.2.3.2.7.2.8.
Class B position sources may not provide VFOM directly. When VFOM is
not available directly, VFOM SHALL be derived from Vertical Dilution
of Precision (VDOP) according to the following formula: VFOM = 2 \*
VDOP \* UERE, where the UERE is 6 metres.

A1.2.5.11 The Type Code 31, Operational Status Message, subfield
‘Airborne Capability Class Code’, SHALL be changed to indicate
the device is a TABS.

A1.2.5.11.1 The Operational Status Message SHALL be modified to
indicate that it meets the performance standards of this ETSO.
ED-102A, including Corrigendum-1, dated January, 2012, paragraph
2.2.18.4.7 and Figure 2-40, is modified by this ETSO. Message bits
53-54, (ME Bits 21‑22), SHALL describe the capabilities of the
TABS per Table 26. Set bit 54 to 1 (one) to indicate that either TABS
Class A, Class B, or both classes of equipment are installed.

<table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0">
<col/>
<col/>
<col/>
<tr valign="top">
<td bgcolor="#808080">
Bit
			53 

</td>
<td bgcolor="#808080">
Bit
			54 

</td>
<td bgcolor="#808080">
Description
			

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
0
			

</td>
<td bgcolor="#d9d9d9">
0
			

</td>
<td bgcolor="#d9d9d9">
Not
			TABS equipped 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
0
			

</td>
<td bgcolor="#d9d9d9">
1
			

</td>
<td bgcolor="#d9d9d9">
TABS
			Equipped 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
1
			

</td>
<td bgcolor="#d9d9d9">
0
			

</td>
<td bgcolor="#d9d9d9">
TABS
			device (reserved for future use) 

</td>
</tr>
<tr valign="top">
<td bgcolor="#d9d9d9">
1
			

</td>
<td bgcolor="#d9d9d9">
1
			

</td>
<td bgcolor="#d9d9d9">
TABS
			device (reserved for future use) 

</td>
</tr>
</table>

***Table
26 — ED-102A Airborne
Capability Class Message format***

A1.2.6
GNSS Position Source Function Requirements (For Class B Devices)

A1.2.6.1
Manufacturers may use commercial off-the-shelf (COTS) GNSS position
sources to meet the performance of this ETSO as long as the sensor
meets the requirements in this section. The position source shall be
capable of using satellite-based augmentation system (SBAS)
corrections and health messages to exclude satellites from the
position solution or to correct satellite range errors. In areas
where the SBAS is available, the TABS shall use the SBAS corrections
and health messages to exclude satellites from the position solution
or to correct satellite range errors. In areas where the SBAS is not
available or out of service, the TABS may continue to operate. The
regional airspace authority will determine what operational impacts
this may have on air‑to‑ground usage of TABS equipment.
According to the FAA the GPS constellation experiences a significant
ramp error approximately once a year. During these events, a chipset
which uses the SBAS will, depending on the received SBAS messages,
either correct or exclude the faulty satellite. Refer to RTCA
document DO-229E, Minimum Operational Performance Standards for
Global Positioning System/Satellite-Based Augmentation System
Airborne Equipment, when interpreting SBAS-related requirements.

A1.2.6.2
The GNSS position source SHALL provide a GPS-only solution for use by
the TABS ADS-B function. The FAA and EASA have not evaluated the
performance of other GNSS systems for use in support of
aviation-intended functions. This ETSO will be updated once
sufficient analysis has been performed to show that other GNSS are
appropriate for use by TABS equipment. Note, the GPS-only solution
refers to the use of the GPS satellite constellation, it does not
exclude augmentation of the GPS solution, such as provided by SBAS or
GBAS systems.

A1.2.6.3
The GNSS horizontal position error SHALL not exceed 30 metres, 95th
percentile, when the Horizontal Dilution of Precision (HDOP) is 2.5
or less. The GNSS position source SHALL either transmit a Horizontal
Figure of Merit (95 %) (HFOM) or an HDOP metric.

Note:
The 30-metre horizontal position fixing error requirement assumes a
UERE of 6 metres, consistent with Section A1.2.5.8.

A1.2.6.4
Removed.

A1.2.6.5
The GNSS position source SHALL be capable of transmitting horizontal
velocity measurements more accurate than 10 m/s, 95th percentile.

A1.2.6.6
The GNSS position source SHALL not transmit false or misleading data
in the presence of broadband interference. There is no minimum
interference rejection requirement for TABS equipment and loss of
position in the presence of interference is acceptable behaviour.

A1.2.6.7
The GNSS position source SHALL not use SBAS corrections when the SBAS
satellite is broadcasting message type 0.

A1.2.6.8
The GNSS position source SHALL exclude satellites with UDREI=15
reported in the SBAS fast corrections.

A1.2.6.9
The GNSS position source SHALL apply SBAS fast and long-term
corrections when available.

A1.2.6.10
The GNSS position source SHALL be capable of transmitting geometric
altitude, Height Above the Ellipsoid (HAE) measurements more accurate
than 45 metres, 95th percentile, when the Vertical Dilution of
Precision (VDOP) is 3.7 or less. The GNSS position source SHALL
either transmit a Vertical Figure of Merit (95 %) (VFOM) or a
Vertical Dilution of Precision (VDOP) metric.

Note:
The 45-metre vertical position fixing error requirement assumes a
UERE of 6 metres, consistent with Section A1.2.5.10.

A1.2.7
Antenna Function Requirements

A1.2.7.1
The requirements for transponder antennas are specified in
ETSO-C112e. The requirements for GNSS antennas are specified in
ETSO-C190 and ETSO-C144a. The antennas should be designed to meet the
performance specified in the applicable ETSO. However, the TABS may
benefit significantly in installation costs from implementations
where the antennas are integrated in the TABS equipment. Small
degradations in antenna performance may be acceptable as a trade-off
for installation cost.

A1.2.7.2
Antennas may be installed internally on aircraft that are transparent
to radio frequencies. An internal antenna may not be appropriate on
aircraft with a metal hull. If an antenna is installed internally,
testing will need to be conducted to ensure the TABS is not
negatively impacted and installation guidance must accompany the unit
to ensure the system is properly fitted to the aircraft.

A1.2.7.3
Because TABS may be installed on a radio frequency (RF) transparent
fuselage near a pilot or passenger, or in a cockpit in close
proximity to a pilot or passenger, consideration must be given to
antenna placement to ensure it does not pose a hazard to humans or
combustible materials. Manufacturers must provide installation
guidance describing the minimum safe distance the antenna can be to
the nearest human body or if applicable, combustible material.
Appendix 3 to this ETSO provides a more in-depth discussion of this
subject based on FCC and European documents.

A1.2.8
Form factor and power

A1.2.8.1
An ideal implementation of the TABS would be a single integrated unit
with minimal connections to the airframe, such as; mechanical
mounting, power, and static air source. Where the equipment might be
shared between multiple airframes, the mechanical mounting could
incorporate an airframe-specific configuration module (containing
such items as the ICAO 24-bit aircraft address), and be designed such
that no tools are required to remove or install the TABS.

A1.2.8.2
Low-power consumption design is important. Designs specifically
intended for long-term battery operation are ideal. If the TABS is
battery powered, it should be designed to provide system integrity
commensurate with the failure condition category / classification
stated in paragraph 3.2.1.

[Amdt. ETSO/13]

[Amdt. ETSO/16]