Exhaust and propeller danger areas to be
avoided by personnel while aircraft engines are being
operated on the ground are depicted in Figure 2-4.
Distance to be maintained with engines operating at
idle are also shown. Temperature and velocity of
exhaust gases at varying locations aft of the exhaust
stacks are shown for maximum power. The danger
area extends to 40 feet aft of the exhaust stack outlets.
Distances to be maintained with engines operating at
idle and propeller danger areas are also shown.
2-7. LANDING GEAR SYSTEM.
electrically controlled and hydraulically actuated. The
landing gear is extended and retracted by a hydraulic
power pack, located in the left wing center section,
forward of the main spar. The power pack consists
primarily of a hydraulic pump, a 28 Vdc motor, a gear
selector valve and solenoid, a two section fluid
reservoir, filter screens, a gear-up pressure switch,
and a low fluid level sensor. Engine bleed air,
regulated to 18 to 20 psi, is plumbed into the power
pack reservoir and the system fill reservoir to prevent
cavitation of the pump. The fluid level sensor activates
an yellow caution annunciator, placarded HYD FLUID
LOW, located on the caution / advisory annunciator
panel, whenever the fluid level in the power pack is
low. Test the annunciator by pressing the HYD FLUID
SENSOR TEST switch located on the pilot's subpanel
for the aircraft. Refer to Figure 2-5, Sheets 1 through
Power for the hydraulic power pack is supplied
through the landing gear motor relay and a 60-ampere
circuit breaker located under the floorboard forward of
the main spar. The motor relay is energized by power
furnished through the 2-ampere LANDING GEAR
RELAY circuit breaker located on the pilot's subpanel.
A time delay module that senses operation voltage
through a 5-ampere circuit breaker protects the power
pack motor. Both are located beneath the aisleway
floorboards, forward of the main spar. Landing gear
extension or retraction is normally accomplished in 6
to 7 seconds. Voltage to the power pack is terminated
after the fully extended or retracted position is
reached. If electrical power has not terminated within
14 seconds, a relay and 2-ampere landing gear circuit
breaker will open and electrical power to the system
power pack will be interrupted.
The landing gear system utilizes folding braces,
called drag legs, which lock into place when the gear
is fully extended. The nose landing gear actuator
incorporates an internal down lock to hold the gear in
the fully extended position. The two main landing
gears are held in the fully extended position by
mechanical hook and pin locks. The landing gear is
held in the up position by hydraulic pressure. The
power pack pressure switch and an accumulator that
is pre-charged with nitrogen to 800 ± 50 psi control the
pressure. Gear doors are opened and closed through
a mechanical linkage connected to the landing gear.
The nose wheel steering mechanism is automatically
centered and the rudder pedals relieved of the steering
load when the landing gears are retracted. Air-oil type
shock struts, filled with compressed nitrogen and
hydraulic fluid, are incorporated with the landing gear.
a. Landing Gear Control Switch. Landing
gear system operation is controlled by a manually
actuated, wheel-shaped switch, placarded LDG GEAR
CONTROL UP / DN, located on the pilot's subpanel.
The control switch and associated relay circuits are
protected by a 2 -ampere circuit breaker, placarded
LANDING GEAR RELAY, located on the pilot's
b. Landing Gear Down Position Indicator
Lights. Visual indication of landing gear position is
provided by three individual green GEAR DOWN
position indicator lights located on the pilot's subpanel.
Testing of the indicator lights is accomplished by
pressing the annunciator test switch. The circuit is
protected by a 5 -ampere circuit breaker, placarded
LANDING GEAR IND, on the right sidewall circuit
breaker panel. Refer to Figure 2-6, Sheets 1 through
5, for the circuit breaker panels for the C-12R, C-12T3,
and C-12F3 (OSA) (ANG) aircraft.
c. Landing Gear Position Warning Lights.
Two parallel-wired red indicator lights, located in the
LDG GEAR CONTROL switch handle, illuminate to
show that the gear is in transit or unlocked. The red
indicator lights in the handle also illuminate when the
landing gear warning horn is actuated. Both red
indicator lights indicate the same warning conditions,
but two are provided for a fail-safe indication in case
one bulb bums out. The circuit is protected by a
5-ampere circuit breaker, placarded LANDING GEAR
IND, on the right sidewall circuit breaker panel.
d. Landing Gear Warning Indicator Light Test
Switch. A test switch, placarded HDL LT TEST, is
located on the pilot's subpanel. When this test switch
is pressed, failure of the landing gear handle to
illuminate red indicates two defective bulbs or a circuit
fault. The circuit is protected by a 5-ampere circuit
breaker, placarded LANDING GEAR WARN, on the
right sidewall circuit breaker panel.