CESSNA
SECTION 7
MODEL 172S NAV III
AIRPLANE AND SYSTEMS DESCRIPTION
BRAKE SYSTEM
The airplane has a single-disc, hydraulically actuated brake on each
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 are operated by applying pressure to the top of
either the left (pilot's) or right (copilot's) set of rudder pedals, which
are interconnected. When the airplane is parked, both main wheel
brakes may be set by utilizing the parking brake which is operated
by a handle under 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 brake system properly
maintained, and minimize brake usage during taxi operations and
landings.
Some of the symptoms of impending brake failure are: gradual
decrease in braking action after brake application, noisy or dragging
brakes, soft or spongy pedals, 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 reapply 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
The airplane is equipped with a 28-volt direct current (DC) electrical
system consisting of a belt-driven 60-ampere alternator and a 24-
volt main storage battery (refer to Figure 7-7). The storage battery
is located inside the engine cowling on the left firewall. The
alternator and battery are controlled through the MASTER switch
(ALT and BAT) found near the top of the pilot's switch panel.
Power is supplied to most electrical circuits through two primary
buses (ELECTRICAL BUS 1 and ELECTRICAL BUS 2), with an
Essential Bus and a crossfeed bus connected between the two
primary buses to support essential equipment.
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172SPHAUS-00
U.S. 7-43