Beechcraft C-12C Operator And Technical Reference Manual page 88

TM 1-1510-218-10
Propeller reversing
surfaces should be accomplished carefully
to prevent propeller erosion from reversed
airflow and, in dusty conditions, to prevent
obscuring the operator's vision.
The propeller blade angle may be reversed to
shorten landing roll. To reverse, propeller levers must
be positioned at HIGH RPM (full forward), and the
power levers are lifted up to pass over an IDLE detent,
then pulled aft into REVERSE setting. Power levers
must be pulled back through normal idle speed range
before being positioned in REVERSE.
caution light, placarded REV NOT READY, on the
caution/advisory annunciator panel, Figure 2-17, alerts
the pilot not to reverse the propellers.
illuminates only when the landing gear handle is down,
and if propeller levers are not at HIGH RPM (full
forward). This circuit is protected by a 5-ampere
circuit breaker, placarded LANDING GEAR RELAY
D1 and LANDING GEAR CONTROL
on the overhead circuit breaker panel.
2-58. PROPELLER TACHOMETERS.
a. Propeller Speed Indicator (N
tachometers on the instrument panel register propeller
speed in hundreds of RPM, Figure 2-26.
indicator is slaved to a tachometer generator unit
attached to the corresponding engine.
b. Propeller Speed Indicator (N
digital/bar graph propeller tachometers located on the
center of the instrument panel display the measured
N concurrently in a 1 alphabetic, 3½ numeric
2
character digital display and a 38-segment bar graph
display.
The indicator has a digital range of 0 to 2500
RPM while displaying current N
displaying exceedence N
a range of 0 to 2500 RPM.
The digital display will contain dashes (----) when
the measured N is greater than 2500 RPM. When
2
displaying exceedence N
value, not "----", will be displayed up to 4000 RPM.
The dashes will be prefixed with an "F" if an
EEPROM failure has been detected and with and "E" if
an event has been stored and played back.
The indicator performs BIT on the LCD display,
ROM (program memory), RAM (volatile data memory),
and EEPROM (Non-volatile data memory), and input
signal. The display BIT shall consist of displaying all
2-72
CAUTION
on unimproved
One yellow
This light
D2 T , located
) C D
2
) T .
2
and 0 to 4000 while
2
. The bar graph display has
2
values the actual measured
2
active LCD segments for three seconds on power up.
If the ROM or RAM fails BIT the indicator display will
be blank. If the input signal fails BIT the indicator will
prefix the digital display with "F".
BIT failures are not stored in EEPROM. Failures
detected shall therefore not affect the display after
power is cycled unless the failure is encountered
again.
Each exceedence event will consist of two 16-bit
words. One word will contain the peak RPM
measured during the event and the other word
contains the event duration in seconds.
A maximum of 50 events can be recorded. If
more than 50 events are recorded, only 50 will be
stored. As new events are recorded, the oldest events
will be discarded.
The indicator will prefix the digital display with an
C
"E" when an event is being or has been recorded and
not played back.
The indicator will start recording an event
immediately when the indicator has measured RPM
greater than 2200 or when the indicator has measured
. Two
RPM exceeds 2081.
digital display will be prefixed with an "E" when the
Each
indicator begins recording an exceedence.
indicator will end exceedence recording and store the
event when the measured RPM drops to 2080 or
lower.
Two
The even display takes precedence over normal
digital display. The bar graph will continue to display
current N data. To activate the event display press
2
the EXCEEDENCE DISPLAY switch for 0.2 seconds
or longer. The most recent event will be displayed
first. Each event display contains the following cycle:
(1) The event number will be displayed for
2 seconds.
(2) The event peak RPM will be displayed for
2 seconds.
(3) The event duration in seconds will be
displayed for 2 seconds.
All three data items displayed during playback
will be prefixed with a "P" unless an EEPROM BIT
failure has been detected in which case the display will
be prefixed with an "F".
The event display will be terminated after all of
the recorded events have been displayed. Once the
playback sequence has been performed the "E"
The flashing will cease and
The