Revision 4 - December 17,1998 Ryan TCAD 9900 Series Page 3-6
3.6 THE AIR TRAFFIC SHIELD
The volume of airspace in which traffic should be detected changes with the traffic
density. When traffic is light, and aircraft are at cruising speeds, a large area of airspace
should be monitored. In higher density airspace, when the pilot is more alert for traffic
and speeds are limited, a smaller surveillance volume is generally appropriate.
The concept of an Air Traffic Shield is used to describe an adjustable volume of airspace,
controlled by the pilot to display potential threats, yet prevent extraneous traffic from
being displayed.
The Air Traffic Shield is a slice of airspace of specified radius and specified height above
and below the aircraft, where a detected threat normally cannot enter without generating
an alert.
3.7 OPERATING MODES
The Ryan TCAD provides three quickly selectable and pilot programmable shield volumes,
designated as the Enroute (ENRT), Standard (STD), and Terminal (TRML) modes. See
Figure 1-2 for Shield limits.
The TCAD displays threat data when an intruder is detected near the shield, and a tone is
generated when the threat enters the shield. The MUTE button may be used to suppress
the tone for a specified duration.
To avoid nuisance indications on the ground, a special sub-mode of the Terminal Mode,
called the Ground Mode, can be automatically activated. The Ground Mode has the same
height as the Standard Mode shield size and range dimension of the Terminal Mode.
Traffic is not displayed at and below 100 feet above the host altitude, and all alert tones
are muted. Thus data available from traffic near the airport is displayed, and aircraft on
the ground are not displayed.
The Ground Mode is activated automatically upon initialization, or by pressing the TRML
and STD buttons. See Paragraph 3.11 and the Pilot's Handbook for more information.
A transition symbol of "DP", for departure is shown in the Mode cell during the transition
from the 200 foot level to the full dimension of the Terminal shield.
The Approach Mode can be activated before landing to eliminate tones caused by aircraft
on the ground as the TCAD-equipped airplane approaches the runway.
In order to use the Approach Mode before landing, TCAD must be supplied with the
destination elevation.
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