Minimum Aviation System Performance Standards for Aircraft ...

Appendix A
Page A-21
Traffic Situation Display (TSD) – A TSD is a cockpit device that provides graphical information on
proximate traffic as well as having a processing capability that identifies potential conflicts with
other traffic or obstacles. The TSD may also have the capability to provide conflict resolutions.
Traffic symbol – A depiction on the CDTI display of an aircraft or vehicle other than the own-ship.
Traffic target – This is an aircraft or vehicle under surveillance. In the context of the ASA subsystems at
a receiving ASA participant, traffic targets are aircraft or vehicles about which information is
being provided (by ADS-B, TIS-B, TCAS, etc.) to the ASSAP.
Transmission Rate – The sustained rate at which periodic ADS-B messages are transmitted.
Transponder – A piece of equipment carried on board an aircraft to support the surveillance of that
aircraft by secondary surveillance radar sensors. A transponder receives on the 1030 MHz and
replies on the 1090 MHz downlink frequency.
Trajectory Uncertainty – Trajectory uncertainty is a measure of predictability of the future trajectory of
each aircraft. There are a number of factors involved in trajectory predictability. These include
knowledge of a valid future trajectory, capability of the aircraft to adhere to that trajectory,
system availability (e.g., ability to maintain its intended trajectory with a system failure in a non
redundant system versus a triple redundant system), and others.
Update Interval – The time interval between successful message receipt with a given probability of
successful reception at a specified range. (Nominal Update Interval is considered 95%
probability of successful reception at a specified range.)
Update Rate – The reciprocal of update interval (e.g. if the update interval is 5 s, the update rate = 1/5 ~
0.20 Hz for the example above).
User-Preferred Trajectories (UPT) – A series of one or more waypoints that the crew has determined to
best satisfy their requirements.
Velocity – The rate of change of position. Horizontal velocity is the horizontal component of velocity
and vertical velocity is the vertical component of velocity. In these MASPS, velocity is always
expressed relative to a frame of reference, such as the WGS-84 ellipsoidVref – The reference
landing air speed for an aircraft. It is weight dependent. Flight crews may vary their actual
landing speed based on winds, etc.
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