User's Manual

SYSTEM DESCRIPTION AND INSTALLATION MANUAL
T
3
CAS/Part No.9005000
SYSTEM DESCRIPTION
1. General
The T
3
CAS Integrated Platform combines TAWS, TCAS and a Mode S Transponder to form a
combined system (T
3
CAS). Optionally, the T
3
CAS may contain obstacle alerting in addition to
terrain and Eleview functions within the same LRU. The integration of the functions provides
significant cost and space advantages to the customer. The implementation method used
preserves the independence of the TCAS, TAWS and Transponder functions within the T
3
CAS
LRU. The system reliability for the T
3
CAS LRU is greater than a federated system with separate
TCAS, TAWS and Transponder LRUs.
The TCAS function, within T
3
CAS, determines the range, altitude, and bearing of other aircraft
equipped with Mode S/Air Traffic Control Radar Beacon System (ATCRBS) transponders, with
respect to the location of own aircraft. It also monitors the trajectory of these aircraft for the
purpose of determining if any of them constitute a potential collision hazard. The TCAS function is
responsible for estimating the projected intruder track and determining if a potential conflict exists.
If so, the system displays an advisory to the pilot. The system also provides guidance for the
optimum vertical avoidance maneuver. Complementary avoidance maneuvers between two
TCAS equipped aircraft are ensured by coordination of mutual intentions with the other aircraft
through the Mode S Transponders. The T
3
CAS TCAS function meets the TSO requirements
referenced in Table 1-2.
The Automatic Dependent Surveillance-Broadcast (ADS-B) function accepts and decodes several
types of ADS-B messages. The ADS-B message types that are supported include: Flight
Identification, Surface and Airborne Position, Airborne Velocity, Target State and Status, and
Aircraft Operational Status.
The ADS-B function takes the traffic information from the 1090 MHz squitters (ADS-B messages)
and generates a list of the aircrafts within the receiver area. The function is a part of the ATSAW
functionality and is performing the underlying tracking of targets and the correlation of ADS-B and
TCAS data.
The ADS-B function correlates traffic targets, if possible, to present a single traffic with the best
possible position to the other systems. This provides filtering based on the reported quality of the
data provided by the traffic and filtered against the values provided by the receiving function. The
filter uses quality parameters provided with the ADS-B transmissions and defined in either RTCA
DO-260, DO-260A or DO-260B depending on what protocol the traffic is using. The result of the
tracking calculations and the filtering is provided in a traffic list customized for each function
receiving this data. The output of the ADS-B function is a graphical Display Traffic Information
File (DTIF) as well as an MCDU list of traffic within receiver range and within a maximum number
of traffic limits. This information forms the base for the higher-level ADS-B function of In-Trail
Procedures (ITP).
The T
3
CAS TAWS function, within the T
3
CAS, provides Collision Prediction and Alerting (CPA),
as well as conventional Ground Proximity Warning System (GPWS) modes of operation. The
CPA uses data provided by the Flight Management Computer, the GPS receiver, and other
aircraft subsystems to predict a 3-D flight path based upon a curve-fit extrapolation of the most
recent position and velocity data received. This predicted flight path is then compared with the
internal terrain profile of the immediate area and the CPA algorithm computes an assessment of
Pub. No. 8600200-001, Revision 004
34-45-29
1-1
04 Nov 2014
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