User's Manual
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
T
3
CAS/Part No.9005000
The T3CAS unit has the following FAA approved software deviations. These do not affect the installation
or performance of the system. The following table is a compilation of deviations across multiple releases.
Deviation numbering within this document may not correlate to deviation numbering used elsewhere.
Table 1-5 - T3CAS Unit Deviation Notes
Deviation 1: TSO-C119c and TSO-C119d: DO-185B 2.2.4.6.2.2.4, 2.4.2.1.7.6 - Mode S Power
Programming in High Density
DO-185B Paragraph 2.2.4.6.2.2.4 indicates that the transmit power level of Mode S tracking
interrogations to targets (but not air-to-air coordination interrogations) shall be automatically reduced
as a function of range for targets within 10 NMI.
The deviation allows the use of a precursor interrogation to be transmitted at the lower of either the
MOPS calculated power level for power programming or a power level based on previously received
replies from the intruder aircraft. If a reply is not received from the precursor interrogation, then
tracking interrogations are transmitted at a higher power level according to the MOPS requirements
for tracking interrogation transmissions.
Deviation 2: TSO-C119c and TSO-C119d: DO-185B 2.2.4.4.2.2b, 2.4.2.1.5.1 Mode S Preamble
Reception
This deviation from DO-185B allows the use of the enhanced pulse decoder techniques defined in
DO-260B Appendix I of the TCAS pulse decoder techniques specified in DO-185B
2.2.4.4.2.2b.
The test procedures defined in DO-185B 2.4.2.1.5.1 are replaced by test procedures defined in DO-
260B section 2.4.4.4.2.2 for System Bench tests, where a DF-11 replaces a DF-17 in the test
procedures. For Environmental Qualification tests, DO-260B section 2.3.2.4.6.2 is used, where a DF-
11 replaces a DF-17 in the test procedure. (Note - 2.3.2.4.6.2 tests have been approved by SC-186
WG3 and will be included in release DO-260B of that document). The ADS-B Enhanced Preamble
Detection techniques in DO-260B Appendix I provide a more robust implementation than the legacy
TCAS Mode S Preamble Detection techniques defined in DO-185B, and therefore provide an
equivalent level of safety.
Deviation 3: TSO-C166a: DO-260A 2.4.10.6.3 Report Verification of Reasonableness Test Applied
to Positions Determined from Locally Unambiguous CPR Decoding
This deviation from DO-260A 2.4.10.6.3 increases the tolerance from 6 NMI ±5 m to 6 NMI ±100 m
for airborne participants and 0.75 NMI ±1.25 m to 0.75 NMI ±100 m for surface participants.
Deviation 4: TSO-C166a: DO-260A 2.2.3.2.7.3.2.1 TEST Message with SUBTYPE=7, Global
Enable/Inhibit
This deviation from DO-260A Change 2, paragraph 2.2.3.2.7.3.2.1 and 2.2.3.2.7.3.2.2 complies with
the proposed change to DO-260A. The change removes the geographic filter which is defined in
2.2.3.2.7.3.2.2 and makes the default setting of the global parameter to Enable Transmission of the
TEST Message with SUBTYPE=7.
The transmission of the TEST message has no effect on system safety, and therefore will have an
equivalent level of safety. The current system with the geographic filter enabled transmits the TEST
message only in North America. The effect of the change is to allow it to be transmitted at all
locations. The effect of the change provides additional ADS-B data outside North America.
Pub. No. 8600200-001, Revision 004
34-45-29
1-9
04 Nov 2014
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