User's Manual Part 2

T
2
CAS / Part No. 9000000
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
34-43-20
15 Feb 2003
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6--25
ID--8000643
Figure6--20. PartNumbersPage5(Page6of6)
E. T
2
CAS Computer Unit Self--Test
The T
2
CAS computer unit detects system faults and displays them on its front panel
annunciators. Its flight leg memory stores system status and fault information for 10
consecutive flight legs. A flight leg is the interval between weight --off--wheels and weight--
on--wheels during which T
2
CAS is operative. By recalling the stored data, ground
maintenance personnel can evaluate in --flight performance on the ground and fault
isolate a current or previous failure to a specific LRU or L RU interface.
Table 6--3 summarizes how the T
2
CAS computer unit self--test is activated at power--up,
during operation, and during commanded self --test. The computer unit can activate the
commanded self--test only when the aircraft is on the ground.
Table 6--4 lists the functions of the computer unit’s status annunciators and the
corresponding troubleshooting actions. If the annunciators indicate an antenna problem,
the antenna connections should be checked by measuring the antenna resistance values
at the computer unit mounting tray. The resistance values listed in Table 6--5 are
measured between the center conductor and shield on each LTP and LMP antenna
connector.