User's Manual

SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 1−37
15 Dec 2005
The VSI/TRA also displays symbology corresponding to traffic in the vicinity of the
aircraft. Threat information is received from the TCAS Computer Unit on a dedicated
high−speed ARINC 429 bus. The display uses the bearing, altitude, and range data
for each threat to provide an indication of the proximity of the threat. Allowable
(nonilluminated or green illuminated bands) and prohibited (red illuminated bands)
vertical rates are displayed based on information received from the TCAS computer
unit. The VSI/TRA can be pin programmed to provide vertical speed data only,
vertical speed and resolution advisory data, or vertical speed, resolution advisory and
traffic advisory data. Display of the TCAS system fault status is provided on the
VSI/TRA in response to extended TCAS control panel TEST activation.
Display dimming is controlled from several inputs consisting of an internal light sensor
mounted on the bezel of the LRU, a remote light sensor, and the aircraft dimming
bus. The display is dimmed by varying the brightness of the LCD panel backlighting.
(2) Software Considerations
VSI/TRA software is developed to a DO−178A category of Level ll (essential). The
software continually monitors and displays vertical speed and TCAS information.
Output discretes supply user components with the status of the LRU. TCAS valid
indicates that the LRU is displaying valid TCAS information. On the 55−pin version,
VSI valid indicates that the LRU is displaying valid vertical speed information. This is
needed to support the bootstrap feature, which is exclusive to the 55−pin version of
the VSI/TRA display.
(3) Built−In Test Equipment (BITE) and Self−Test Capability
The LRU has input discretes that allow a calibration and test program to be run. This
mode allows the display to be adjusted and various diagnostic tests to be performed.
These tests and adjustments can only be done in a shop on a dedicated test fixture.
When the LRU application program is operating in the aircraft, the background loop
continuously monitors the power supply status, the ROM integrity, and the analog
range limits. A failure results in the setting of bad status output discretes. A cold
start will continuously be attempted until the LRU passes the built−in test. There is a
dedicated self−test input for both versions of the VSI/TRA Display. When this pin is
activated, the unit will display symbology that aids in the detection of unit faults.