2-76 Change 3
CABIN LIGHTS, in the overhead circuit breaker panel.
(4) Cabin door latching mechanism light. A light is
provided to check the cabin door latching mechanism. It
is controlled by a red pushbutton switch located adjacent
to the round observation window, which is just above the
2-77. EMERGENCY LIGHTING SYSTEM.
An independent battery-operated emergency lighting
system is installed. The system is actuated automatically
by shock, such as a forced landing. It provides adequate
lighting inside and outside the fuselage to permit the oc-
cupants to read instruction placards and locate exits. An
inertia switch, when subjected to a 2 G (minimum) shock
will illuminate the interior lights in the cockpit, forward and
aft cabin areas, exterior lights aft of the emergency exit,
and aft of the cabin door. The battery power source is au-
tomatically recharged by the aircraft electrical system.
a. Emergency Lighting System Operation. An emer-
gency lights override switch, located on the overhead
control panel (fig. 2-13), is provided to turn the system off
if it is accidentally actuated. The switch is placarded
EMERGENCY OFF/RESET - AUTO - TEST. Should the
system accidently actuate, the emergency lights will illu-
minate. Placing the switch in the momentary OFF/RE-
SET position will extinguish the lights. To test the system,
place the switch in the momentary TEST position. The
lights should illuminate. Moving the switch to the OFF/
RESET position will turn the system off and reset it. The
switch is normally in the AUTO position.
2-78. PITOT SYSTEM.
The pitot system (fig. 2-33) provides ram air pressure
for the airspeed indicators and air data computer. The pi-
tot system consists of two pitot masts (one located on
each side of the lower portion of the nose), and associat-
ed plumbing. The pitot masts are protected from ice
formation by internal electric heating elements.
2-79. STATIC AIR SYSTEM.
a. Description. The static system (fig 2-33) provides
static air pressure for the pilots and copilots airspeed
indicators, copilots altimeter, air data computer, and pi-
lots and copilots vertical speed indicators. The static air
pressure ports are located on the right and left sides of
the aft fuselage exterior skin.
b. Alternate Static Air Source. An alternate static air
line, which terminates just aft of the rear pressure bulk-
head, provides a source of static air for the pilots instru-
ments in the event of source failure from the pilots static
air line. A control on the pilots subpanel placarded PI-
LOTS STATIC AIR SOURCE, may be actuated to select
either the NORMAL or ALTERNATE air source by a two
position selector valve. The valve is secured in the NOR-
MAL position by a spring clip.
2-80. TURN-AND-SLIP INDICATOR.
A turn-and-slip indicator is installed on the pilots side
of the instrument panel (fig. 2-16). This indicator is gyro-
scopically operated and pneumatically powered.
2-81. AIRSPEED INDICATORS.
Two identical airspeed indicators are installed sepa-
rately on the pilots and copilots sides of the instrument
panel (fig. 2-16). These indicators require no electrical
power for operation. The indicator dials are calibrated in
knots from 40 to 300. A striped pointer automatically dis-
plays the maximum allowable airspeed at a given aircraft
2-82. COPILOTS BAROMETRIC ALTIMETER.
a. Description. The copilots barometric altimeter (fig.
2-34), provides an indication of the aircrafts pressure
altitude above sea level.
b. Controls, Indicators, and Functions.
(2) Altitude indicator needle. Used in conjunction
with altitude scale to display aircraft altitude in hundreds
(3) Barometric pressure counter-drum indicator
(millibars). Indicates barometric pressure in millibars that
has been set by the barometric pressure setting knob.
(4) Barometric pressure counter-drum indicator
(Inches of mercury). Indicates barometric pressure in
inches of mercury that has been set by the barometric
pressure setting knob.
(5) Barometric pressure setting knob. Used to
manually set barometric pressure displayed in the IN HG
and MB windows.
(6) Counter-drum altitude display. Indicates air-
craft altitude in tens of thousands, thousands, and
hundreds of feet above sea level.