Beechcraft C-12C Operator And Technical Reference Manual page 558

TM 1-1520-218-10
3C-31. GROUND
ADVISORY SYSTEM (GPAAS).
WARNING
The GPAAS will provide little, if any,
warning for flight into precipitous terrain
approaching a sheer wall if there is little
gradually rising terrain before reaching the
steep terrain.
a. Description. The GPAAS is provided to aid
the flight crew in terrain avoidance. Refer to Figure
3C-149.
The GPAAS is a completely automatic system
(requiring no input from the crew) which continuously
monitors the aircraft's flight path at altitudes of
between 100 and 2000 feet AGL.
The GPAAS computer processes the data and,
when conditions warrant, selects the appropriate
digitized voice advisory/warning message from its
memory. This message is then announced over the
pilot's and copilot's audio systems. If the condition is
not corrected, the GPAAS will rearm, and will again
announce and repeat the warning if the condition
recurs. The GPAAS computer remains ready to
announce a different message during the intervals
between repetitions. All messages are disabled below
100 feet AGL. The GPAAS system receives 28 Vdc
power through a 1-ampere circuit breaker placarded
GPAAS, located on the overhead circuit breaker
panel.
Figure 3C-149. Ground Proximity Altitude Advisory System Controls and Indicator
3C-204
PROXIMITY ALTITUDE (1) GPAAS Switch-Indicator
switch-indicator is located on the instrument panel.
The upper half of the switch-indicator (yellow) is
placarded VOICE OFF. The lower half is an indicator
(red) only and is placarded VA FAIL. Pressing the
VOICE OFF switch indicator disables the GPAAS
voice advisory, and illuminates the VOICE OFF
indicator light. The VA FAIL annunciator light (red) will
illuminate when the GPAAS fails.
(2) GPAAS Volume Control.
volume control placarded VOL, located on the
instrument panel just to the right of the GPAAS switch
indicator lights, controls the audio volume of the
GPAAS advisory/warning messages down to a certain
minimum level.
(3) GPAAS Aural Warning Indications. The
following is a list of aural indications.
possibility of activating more than one condition at a
time, a warning priority has been established. The
highest priority message will be announced first. If a
higher priority item is received after a message is
started, voice annunciation of the higher priority
message shall be announced after a lower priority
message in progress at the end of the message
segment. It will not stop in the middle of a word. On
messages that are repeated three times at 4-second
intervals, the priority list will be scanned for higher
priority messages and will insert them in the interval
between the messages. The messages provided by
the system are listed in descending order of priority.
1. "Two thousand" at 2000 feet AGL.
Lights. A
A GPAAS
Due to the