Revision 4 - December 17,1998 Ryan TCAD 9900 Series Page 3-7
Anytime before landing, the pilot can access the mode by pressing the MUTE and TRML
buttons (thus Muting the Terminal). The status window will show APCH. The top line
of the TCAD Display will show FldElev:, and the lower line will show >>xx00ft (xx is
normally the elevation previously set into this mode). The s and t buttons can be used
to enter the destination field elevation. Pressing the MUTE button again restores TCAD
to the previously selected mode (or eight seconds elapsed time will return TCAD to the
previously selected mode). When the base of the Terminal shield gets within 100 feet of
the selected field elevation, TCAD automatically enters the Approach Mode, as
shown by "AP" in the Mode cell. When the airplane gets within 100 feet of the field
elevation, threat tones are muted, as indicated by the "M" in the status window, and the
Ground Mode is activated, as indicated by the "G" in the Mode cell.
When preset, TCAD will automatically enter the Approach Mode from the Terminal,
Standard, Enroute, or Unrestricted Mode.
The Unrestricted Mode can be selected by pressing the Enroute and Standard buttons
simultaneously (the letter "U" is indicated in the mode cell). This increases the airspace
monitored by TCAD, but alert tones are not issued unless the traffic is detected inside the
Enroute shield. See Figure 1-2 for Unrestricted Mode limits.
If, while in the Unrestricted Mode, traffic is detected inside the ENRT shield, the alert
tone will sound and TCAD automatically enters the Enroute Mode.
3.8 BEARING (Model 9900B)
Bearing to traffic is provided through a patented antenna and receiver system. Two
antennas, the first oriented longitudinally on the top of the aircraft, and a twin-blade on the
bottom of the aircraft, provide bearing resolution. Each antenna provides the bearing
solution and the opposing antenna provides the sense resolution. The signals are
combined and bearing to the traffic is presented on the TCAD Display in 45° increments.
The use of a multifunction display provides a more precise display of bearing to the traffic.
The patented TCAD Bearing Antenna system does not require phase matching of the
antenna cables.
Several benefits are realized through use of this technology. Bearing to traffic is available
at a lower cost. The antenna system is greatly simplified. Top and bottom antenna
coverage is preserved. Phase matching of the antenna cables is not required, which
reduces the complexity of the reception circuitry and simplifies the installation. Complete
antenna and equipment checkout can be accomplished on the ground without expensive
test equipment.
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