Figure 3B-141. Maximum Permissible Exposure Level
AVOIDANCE SYSTEM (TCAS II).
a. System Overview.
(1) The Traffic Alert and Collision Avoidance
System (TCAS) is an airborne system that interrogates
mode A/C and mode S transponders in nearby aircraft
and uses the replies to identify and display potential
and predicted collision threats to the flight crew. The
system protects a volume of air space around your
own aircraft. Aural and visual advisories are provided
to the flight crew to assure adequate separation when
a system analysis of the intruding aircraft closure rate,
penetration of the protected airspace. The TCAS II is
controlled through the TTC-920 Transponder/TCAS
control panel located on the pedestal.
(2) Traffic alerts and resolution advisories
are indicated on the TVI-920 Transponder/TCAS
Display. Traffic alerts provide the flight crew with the
relative bearing and distance to intruding aircraft that
are approximately 40 seconds from Closest Point of
Approach (CPA). This alert provides aid in visually
acquiring the intruding aircraft. No maneuvers are
commanded. The resolution advisory provides threat
resolution information in the form of a vertical
maneuver (corrective) or restricted vertical speed
range (preventive) that will increase aircraft separation
when the threat aircraft is approximately 25 seconds
(3) A traffic display and a resolution advisory
display are provided to the flight crew. The traffic
display consists of the relative position of mode A/C
and mode S transponder equipped aircraft around the
TCAS equipped aircraft. The resolution advisory
display indicates the appropriate vertical maneuver or
restricted vertical speed range to avoid a threat.
(4) Only operating mode A/C or mode S
transponders that provide altitude information will
generate resolution advisories. Only traffic alerts will
be generated by mode A/C or mode S transponders
that provide no altitude information, or by aircraft
b. TCAS II Controls and Functions.
(1) Controls and functions of the TTC-920
are illustrated in Figure 3B-142 and detailed in Table
(2) Controls and functions of the TVI-920
Display are illustrated in Figure 3B-143 and detailed in
Table 3B -104.
Symbols. Symbols displayed on TCAS Display are
shown in Table 3B-105.
d. TCAS Mode/Warning Flags and Messages.
TCAS mode/warning flags and messages are shown
in Figure 3B -144 and Table 3B -106. They may appear
in one of the seven indicated slots on the display face.
e. Aural Annunciator Messages. There are
two types of Aural Annunciator Messages: a Traffic
Advisory Annunciation and a Resolution Advisory
described in Table 3B-107.