User's Manual
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 1−55
15 Dec 2005
(4) VSI Scale Overlays
During a resolution advisory, red and green bands overlay the VSI scale. The red
band indicates what vertical speed range is to be avoided by the pilot (prohibited
vertical speed). The green band indicates the vertical speed the pilot is to attain to
achieve safe separation from a threat aircraft (recommended vertical speed). The
red/green band reflects the RA in progress and acts as a vertical speed advisory for
the pilot.
(5) Reference Graphics and Annunciations
A white airplane symbol is displayed in the lower center of the VSI representing the
aircraft own position. A white range ring made up of 12 dots, each corresponding to
a normal clock position, is included. The range ring surrounds the airplane with a
radius of 2 nautical miles and is intended to assist in interpreting TCAS traffic
information.
The scale of the VSI display is 6.0 nautical miles to the top display edge of the VSI
(ahead of the aircraft), 4 miles to the left and right edges, and 2.5 nautical miles to
the bottom (behind the aircraft).
Annunciations in white letters serve as a reminder of the current operation mode.
They include TCAS OFF, TA only and RA only. Fault annunciations in amber letters
replace the mode annunciations in case of system failure. They include TCAS FAIL,
RA FAIL, VSI FAIL, and TA FAIL (traffic display failure). Figure 1−12 shows a typical
failure display.
C. Aural Messages
The TCAS generates aural alerts or messages announced over the aircraft audio system.
These messages accompany the visual TA or RA display and are softened or
strengthened, depending on the urgency of the situation. The TCAS audio level is preset
and is not adjustable by the aircrew.
If a logic change occurs before a message is completed and a new message is initiated,
the original alert is terminated and the new alert announced immediately.
(1) Requirements and Limitations
The following is a list of the requirements and limitations for issuing an aural advisory
by the TCAS Computer Unit:
(a) Voice announcements are inhibited below 500 feet above ground level (AGL).
(b) The CANCEL BUTTON, halts voice announcements after the CANCEL BUTTON
is activated. An aural advisory in progress is terminated and not repeated after
deactivation of the CANCEL BUTTON.
(c) During TCAS computer unit self−test, an aural advisory confirms proper
operation of the aural advisory system by annunciating the message “TCAS
TEST”. The aural advisory system annunciates the pass/fail status of any
monitored functions with the messages “TCAS TEST PASS” and “TCAS TEST
FAIL”, respectively.