SECTION 3 CESSNA
EMERGENCY PROCEDURES MODEL T182T NAV III
GFC 700 AFCS
U.S.
ELECTRICAL POWER SUPPLY SYSTEM
MALFUNCTIONS
Malfunctions in the electrical power supply system can be detected
through regular monitoring of the main battery ammeter (M BATT
AMPS) and the main electrical bus voltmeter (M BUS VOLTS);
however, the cause of these malfunctions is usually difficult to
determine. A broken alternator drive belt, too much wear on the
alternator brushes, or an error in wiring is most likely the cause of
alternator failures, although other factors could cause the problem. A
defective Alternator Control Unit (ACU) can also cause malfunctions.
Problems of this nature constitute an electrical emergency and should
be dealt with immediately. Electrical power malfunctions usually fall into
two categories: excessive rate of charge and insufficient rate of charge.
The following paragraphs describe the recommended remedy for each
situation.
EXCESSIVE RATE OF CHARGE
After engine starting and heavy electrical usage at low engine speeds
(such as extended taxiing), the battery condition will be low enough to
accept above normal charging during the initial part of a flight.
However, after thirty minutes of cruising flight, the main battery
ammeter (M BATT AMPS) should be indicating less than 5 amps of
charging (+) current. If the charging current remains above this value
on a long flight, the battery electrolyte could overheat and evaporate.
Electronic components in the electrical system can be adversely
affected by higher than normal voltage. The ACU includes an
overvoltage sensor circuit which will automatically disconnect the
alternator if the charge voltage increases to more than approximately
31.75 volts. If the overvoltage sensor circuit does not operate correctly,
as shown by voltage more than 31.75 volts on the main battery bus
voltmeter, the MASTER switch ALT section should be set to the OFF
position. Unnecessary electrical equipment should be de-energized
and the flight terminated as soon as practical.
(Continued Next Page)
T182TPHBUS-01
3-36
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