Electrical System; Master Switch; Ammeter - Cessna 150 COMMUTER 1976 Pilot Operating Handbook

SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
CESSNA
MODEL 150M
soft or spongy pedals, short pedal travel and hard pedal, and excessive
travel and weak braking action.
If
any of these symptoms appear, the
brake system is in need of immediate attention. If, during taxi or landing
roll, braking action decreases, let up on the pedals and then re-apply the
brakes with heavy pressure. If the brakes become spongy or pedal travel
increases, pumping the pedals should build braking pressure. If one
brake becomes weak or fails, use the other brake sparingly while using
opposite rudder, as required, to offset the good brake.
ELECTRICAL SYSTEM
Electrical energy (see figure 7 -7) is supplied by a 14-volt, direct-
current system powered by an engine-driven, 60-amp alternator. The
12-volt, 25-amp hour battery is located on the right, forward side of the
firewall. Power is supplied through a single bus bar; a master switch
controls this power to all circuits, except the engine ignition system,
clock, or flight hour recorder, if installed. The flight hour recorder re-
ceives power through activation of an oil pressure switch whenever the
engine is operating; the clock is supplied with current at all times. All
avionics equipment should be turned off prior to starting the engine or
using an external power source to prevent harmful transient voltages from
damaging the transistors in this equipment.
MASTER SWITCH
The master switch is a split-rocker type switch labeled MASTER, and
and is ON in the up position and OFF in the down position. The right half
of the switch, labeled BAT, controls all electrical power to the airplane.
The left half, labeled AL T, controls the alternator.
Normally, both sides of the master switch should be used simulta-
neously; however, the BA T side of the switch could be turned ON separate-
ly to check equipment while on the ground. The ALT side of the switch,
when placed in the OFF position, removes the alternator from the electri-
cal system. With this switch in the OFF position, the entire electrical
load is placed on the battery. Continued operation with the alternator
switch in the OFF position will reduce battery power low enough to open
the battery contactor, remove power from the alternator field, and pre-
vent alternator restart.
AMMETER
The ammeter indicates the flow of current, in amperes, from the
alternator to the battery or from the battery to the airplane electrical
7-22
CESSNA
MODEL 150M
REGULATOR
CLOCK
FLIGHT HOUR
RECORDER
CODE
o
CIRCUIT BREAKER (AUTO_RESET)
Q)
CIRCUIT BREAKER (PUSH_lO_RESET)
• FUSE
-1+
DIODE
f../I/v
RESISTOR
-l~ CAPACITOR INOISE filTER)
SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
TO
WING
FLAP
CIRCUIT
BREAKER
MAGNETOS
FUEL QUANTITY INDICATORS
INSTRUMENT, RADIO, AND
COMPASS LIGHTS
TURN COORDINATOR OR
TURN AND BANK INDICATOR
RADIO
TO RADIO OR TRANSPONDER
AND ENCODING ALTIMETER
TO AUDIO MUTING RELAY
TO CONTROL WHEEL MAP LIGHT
TO NAVIGATION LIGHTS
TO DOME LIGHT
TO F LASH I NG BEACON
TO CIGAR LIGHTER (WITH FUSE)
TO LANDING AND TAXI LIGHTS
Figure 7 -7. Electrical System
7-23