Brake System; Electrical System - Cessna 172 P Pilot Operating Handbook

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indicators on the left side of the
instrument panel. An empty tank
is indicated by a red line and the
letter E. When an indicator shows
an empty tank, approximately
1.5 gallons remain in a standard
tank, and 2 gallons remain in a
long range tank (3 gallons when
long range integral tanks are
installes) as unusable fuel. The
indicators cannot be relied upon
for accurate readings during
skids, slips, or unusual attitudes.
The fuel selector valve should be
in BOTH position for takeoff,
climb, landing and maneuvers
that involve prolonged slips or
skids. Operation from either LEFT
or RIGHT tank is reserved for
cruising flight.
NOTE1:
When the fuel selector valve
handle is in the BOTH position in
cruising flight, unequal fuel flow
from each tank may occur if the
BRA K E S YS TEM
The airplane has a singe -disc,
hydraulically-actuated brake on
ech main landing gear wheel.
Each brake is connected, by a
hydraulic line, to a master
cylinder attached to each of the
pilot's rudder pedals. The brakes
a r e o p e r a t e d b y a p p l y i n g
pressure to the top of either the
left (pilot's) or right (copilot's)
set of rudder pedals, which are
i n t e r c o n n e c t e d . W h e n t h e
airplane is parked, both main
wheel brakes may be set by
utilizing the parking brake which
is operated by a handle under
EL ECTRICA L S YS TEM
The airplane is equipped with a
28-volt, direct-current, electrical
system. The system is powered
b y a b e l t - d r i v e n , 6 0 - a m p
alternator and a 24-volt battery,
located on the left forward side
of the firewall. Power is supplied
to most general electrical and all
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wings are not maintained exactly
level. Resulting wing heaviness
can be alleviated gradually by
turning the selector valve handle
to the tank in the heavy wing.
NOTE2:
When the fuel tanks are 1/4 full
or less, prolonged uncoordinated
flight such as slips or skids can
cover the fuel tank outlets.
Therefor, if operating with one
fuel tank dry or if operating on
LEFT or RIGHT tank when 1/4 full
or less, do not allow the airplane
to remain in uncoordinated flight
for periods in excess of 30
seconds.
NOTE3:
It is not practical to measure the
time required to consume all of
the fuel in one tank, and, after
switching to the opposite tank,
expect an equal duration from
the remaining fuel. The airspace
the left side of the instrument
panel. To apply the parking
brake, set the brakes with the
rudder pedals, pull the handle
aft, and rotate it 90° down.
For maximum brake life, keep the
b r a k e s y s t e m p r o p e r l y
maintained, and minimize brake
usage during taxi operations and
landings.
S o m e o f t h e s y m t o m s o f
impending brake failure are:
gradual decrease in braking
action after brake application,
noisy or dragging brakes, soft or
spongy pedals, and excessive
avionics circuits through the
primary bus bar and the avionics
bus bar, which is interconnected
by an avionics power switch. The
primary bus is on anytime the
master switch is turned on, and
is not affected by starter or
external power usage. Both bus
AIRPLANE & SYSTEMS DESCRIPTION
i n b o t h f u e l
interconnected by a vent line and,
therefor, some sloshing of fuel
between tanks can be expected
when the tanks are nearly full
and the wings are not level.
The fuel system is equipped with
drain valves to provide a means
for the examination of fuel in the
system foe contamination and
grade. The system should be
examined before the first flight
of every day and after each
refueling, by using the sampler
cup provided to drain fuel from
the wing tank sumps, and by
utilizing the fuel strainer drain
under an access door on the aft
right side of the top engine
cowling. If takeoff weight
limitations for the next flight
permit, the fuel tanks shoul be
filled after each flight to prevent
condensation.
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.
bars are on anytime the master
and avionics power switches are
turned on.
CAUTION:
Prior to turning the master switch
on or off, starting the engine or
applying an external power
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