PI-135 OPERATOR’S MANUAL
124
INSTRUMENTS AND SYSTEMS FAIL URES
Individual in stru ments can be failed in two dif fer ent ways:
Freeze (in stru ment main tains in di ca tions 1.
that ex ist at time of fail ure)
Gradual2.
To “Freeze” an in stru ment, click on
its as so ci at ed ARM but ton under
the “Freeze” col umn. To have an
in stru ment fail grad u al ly, click on
its as so ci at ed ARM but ton un der
the “Grad u al” col umn. A gradual
fail ure of this type is some times
re ferred to as an “in sid i ous” fail ure
as it is not as readily apparent and
thus could po ten tial ly be more dan ger ous. Fix at ing on the
At ti tude In di ca tor and fl y ing the aircraft to maintain “wings
lev el” as it (the AI) slowly tumbles, is one example of the
con se quenc es of this type of failure.
FAILURE TIME WIN DOW
The “Be tween” col umn is used to set the
“failure time win dow” in ter val. The val ues
en tered in min utes (00-99) are com
pared
to the Ref. Fail ure Time and de ter mine
when or during what time pe ri od (win dow)
the cor re spond ing ARMed fail ure will
oc cur. If for ex am ple we want the At ti tude
Indicator to grad u al ly fail at some point
be tween sev en and fi f teen minutes from
now, we would sim ply en ter 07 and 15 re spec tive ly in
the “Be tween” col umn and press the ARM button in the
“Grad u al” column next to “AI.” If this were done at the start
of our fl ight the Ref. Fail ure Time would al ready be set to
zero. But, if we had been fl y ing for some time and want ed
the failure to occur be tween sev en and fi f teen min utes
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