TCAS791
Operating Instructions
Pilot’s Guide
2-17
Barometric Input Failures
The TCAS791 will display the TCAS Failed/Barometric Input screen
(figure 2-12) and will stop transmitting interrogations when it fails to
detect barometric altitude (e.g. input from an encoding altimeter). The
TCAS791 can not operate without a barometric altitude input. Most
barometric input failures will more than likely be due to the failure of
equipment external to the TCAS791. If the TCAS Failed/Barometric
Input screen appears, do not turn off the TCAS791. When the baromet-
ric altitude input is restored, the TCAS791 will automatically return to
normal operation.
Maintenance Codes
A maintenance code can only show up when your aircraft is on the ground.
Figure 2-8 shows a maintenance code on the standby screen. Figure 2-13
shows a maintenance code with the aircraft on the ground but not in standby.
The TCAS791 can be used when a maintenance code is displayed, but
should be scheduled for maintenance as soon as possible.
Figure 2-12. TCAS Failed/Barometric Input Screen
Figure 2-13. Maintenance Code When on the Ground but Not in Standby
