Beechcraft C-12C Operator And Technical Reference Manual page 53

T The basic engine fuel system consists of an
engine driven fuel pump, a fuel control unit, a dual fuel
manifold, 14 fuel nozzles, and a fuel purge system.
The fuel purge system forces residual fuel from the
manifolds to the combustion chamber, where it is
consumed.
a. One fuel control unit is on the accessory case
of each engine. This unit is a hydro-mechanical
metering device, which determines the proper fuel
schedule for the engine to produce the amount of
power requested by the relative position of its power
lever. The control of developed engine power is
accomplished by adjusting the engine compressor
turbine (N ) speed. N
1 1
the amount of fuel injected into the combustion
chamber through the fuel nozzles. Engine shutdown is
accomplished by moving the appropriate condition
lever to the full aft, FUEL CUTOFF position, which
shuts off the fuel supply.
2-27. POWER LEVERS.
Moving the power levers into reverse range
without the engines running may result in
damage to the
mechanisms.
Two power levers are located on the control
pedestal, Figures 2-7 and 2-9. These levers regulate
power in the reverse, idle, and forward range, and
operate so that forward movement increases engine
power. Power control is accomplished through
adjustment of the N speed governor in the fuel control
1
unit. Power is increased when N
The power levers also control propeller reverse pitch.
Distinct movement (pulling up and then aft on the
power lever) by the pilot is required for reverse thrust.
Placard beside the lever travel slots reads POWER.
Upper lever travel
(increase), supplemented by an arrow pointing
forward. Lower travel range is marked IDLE / LIFT
and REVERSE. A placard below the lever slots reads,
CAUTION – REVERSE ONLY WITH ENGINES
RUNNING.
2-28. CONDITION LEVERS.
Two condition levers are located on the control
pedestal. Each lever starts or stops the fuel supply,
and controls the idle speed for its engine. The levers
have three placarded positions: FUEL CUTOFF, LO
IDLE, and HIGH IDLE.
position, the condition lever controls the cutoff function
speed is controlled by varying
CAUTION
reverse linkage
RPM is increased.
1
range is designated
In the FUEL CUTOFF
of its engine-mounted fuel control unit. From LO IDLE
to HIGH IDLE, they control the governors of the fuel
control units to establish minimum fuel flow levels. LO
IDLE position sets the fuel flow rate to attain 52% ±
2% C D ; 56-58%
HIGH IDLE position sets the rate to attain 70%
minimum N . The power lever for the corresponding
1
engine can select N
maximum power. An increase in low idle N
experienced at high field elevation.
2-29. FRICTION LOCK KNOBS.
Four friction lock knobs are located on the
control pedestal to adjust friction drag.
Figures 2-7 and 2-9. One knob is below the propeller
levers, one below the condition levers, and two under
the power levers. When a knob is rotated clockwise,
friction restraint is increased opposing movement of
the affected
Counterclockwise rotation of a knob will decrease
friction drag thus permitting free and easy lever
movement.
located on the pedestal adjacent to the knobs.
2-30. ENGINE FIRE DETECTION SYSTEM
A flame surveillance system is installed on each
engine to detect external engine fire and provide alarm
to the pilot. Both nacelles are monitored, each having
a control amplifier and three detectors.
wiring connects all sensors and control amplifiers to dc
power and to the cockpit visual alarm units. In each
nacelle, one detector monitors the forward nacelle, a
second monitors the upper accessory area, and a third
the lower accessory area.
a. Fire emits an infrared radiation that will be
sensed by the detector, which monitors the area of
origin. Radiation exposure activates the relay circuit of
a control amplifier, which causes signal power to be
INCR
sent to cockpit warning systems.
surveillance system will return to the standby state
after the fire is out. The system includes a functional
test switch.
b. Warning Of Internal Nacelle Fire.
(1) The red MASTER WARNING light on the
glare shield
illumination of a red warning light in the appropriate fire
control T-handle, placarded FIRE PULL. Fire detector
circuits are protected by a single 5-ampere circuit
breaker, placarded FIRE DETR located on the
overhead circuit breaker panel, Figure 2-16.
TM 1-1510-218-10
T , (at sea level) minimum N
from the respective idle setting to
1
lever as set by
Two FRICTION LOCK placards are
illuminates accompanied
and
1
will be
1
Refer to
the pilot.
C D T1 .
Electrical
An activated
by the
2-37