User's Manual
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 6−9
15 Dec 2005
(4) RAD/ALT Status Page
Selection of code 0002 displays the RAD/ALT Status page, Figure 6−4. This page
displays the status of the selected radio altimeter interface to the TCAS.
AD−53901,SH3@
Figure 6−4. Typical RAD/ALT Status Page
The first information line (line 3) of the RAD/ALT STATUS page indicates which of the
two radio altimeter ports is being used by the TCAS computer. The TCAS computer
attempts to use radio altimeter No. 1 first. If it determines this input is invalid, it
automatically switches to radio altimeter No. 2.
The current status of the two radio altimeter ports is displayed on lines 5 and 6. If a
signal is valid, the radio altitude value is displayed in either “FT” for English type
altimeters, or “M” for Metric type altimeters.
If one of the radio altitude signals is determined to be invalid, the altitude value is
replaced by INACT. Radio altitude INACT indicates the radio altimeter has failed, is
not powered, or is not connected.
The radio altimeter input is determined to be invalid if, for an analog radio altimeter
input, 28 V dc valid is not present at TCAS CU pin RMP−2K for Radio Alt #1 or pin
RMP−3C for Radio Alt #2, or for a digital radio altimeter input, the sign status matrix
(SSM) of the radio altimeter output indicates not valid or no data is present on the
digital bus.
If the radio altimeter output is greater than 2200 feet (source is valid, but data is
invalid), the radio altitude value is replaced by OVR RNG.
When both radio altitude sources are invalid, line 3 is blank.