Cessna 17273274 Pilot Operating Handbook page 146

CESSNA
MODEL 172N
cabin just forward of the pilot and is helpful when checking maps and othe1
flight data during night operations. To operate the light, first turn on the
NAV LT switch; then adjust the map light's intensity with the knurled disk
type rheostat control located at the bottom of the control wheel.
A doorpost map light is located on the left forward doorpost. It contains
both red and whit.e bulbs and may be positioned to illuminate any area
desired by the pilot. The light is controlled by a switch, below the light,
which is labeled RED, OFF, and WHITE. Placing the switch in the top
position will provide a red light. In the bottom position, standard white
lighting is provided. In the center position, the map light is turned off. Red
light intensity is controlled by the outer knob on the light dimming
rheostat labeled PANEL LT.
The most probable cause of a light failure is a burned out bulb:
however, in the event any of the lighting systems fail to illuminate when
turned on, check the appropriate circuit breaker. If the circuit breaker has
opened (white button popped out), and there is no obvious indication of a
short circuit ( smoke or odor), turn off the light switch of the affected lights.
reset the breaker, and turn the switch on again. If the breaker opens again,
do not reset it.
CABIN HEATING, VENTILATING AND
DEFROSTING SYSTEM
The temperature and volume of airflow into the cabin can be regulated
by manipulation of the push-pull CABIN HT and CABIN AIR control
knobs (see figure 7-8).
For cabin ventilation, pull the CABIN AIR knob out. To raise the air
temperature, pull the CABIN HT knob out approximately 1/ 4 to 1/2 inch
for a small amount of cabin heat. Additional heat is available by pulling
the knob out farther; maximum heat is available with the CABIN HT knob
pulled out and the CABIN AIR knob pushed full in. When no heat is desired
in the cabin, the CABIN HT knob is pushed full in.
Front cabin heat and ventilating air is supplied by outlet holes spaced
across a cabin manifold just forward of the pilot's and copilot's feet. Rear
cabin heat and air is supplied by two ducts from the manifold, one
extending down each side of the cabin to an outlet at the front doorpost at
floor level. Windshield defrost air is also supplied by two ducts leading
from the cabin manifold to defroster outlets near the lower edge of the
windshield. Two knobs control sliding valves in either defroster outlet to
permit regulation of defroster airflow.
Separate adjustable ventilators supply additional air; one near each
1 July 1979
AIRPLANE & SYSTEMS DESCRIPTIONS
SECTION 7
7-29