CHAPTER 96
ELECTRICAL SYSTEM
96-00 Description
CAUTION
The installation of electrical devices can affect the accuracy
and reliability of the electronic tachometer.
A 28-volt DC electrical system is standard. Primary system components are a sealed lead-acid
battery, a starter-generator, and a generator control unit. The battery is located beneath the
left front seat or in a compartment in the left side of the baggage compartment.
The circuit breaker panel is on the ledge just forward of the left front seat. Breakers are
marked to indicate function and amperage and are of the push-to-reset type.
The battery switch controls the battery relay which connects the battery to the electrical
system. A wire protected by a fuse near the battery bypasses the battery relay to allow the
tachometers and clock to receive battery power with the battery switch OFF.
The avionics switch controls power to avionics. This allows avionics to be switched OFF via
a single switch. Having sensitive electrical equipment off when the generator is switched ON
protects against voltage spikes.
An ammeter indicates total generator output. A digital voltmeter which reads main bus voltage
at the circuit breaker panel is incorporated as part of the OAT indicator. Normal indication is
27.3 to 28.7 volts with the generator ON.
A generator control unit (GCU) controls starter-generator function. Below 58 percent N
1
RPM,
the GCU is in start mode regardless of generator switch position. Above 58 percent, the GCU
automatically switches to generate mode. The generator switch should normally be off for
starting to prevent applying generator load to the engine before reaching idle RPM.
If the GEN annunciator illuminates in flight, turn off nonessential electrical equipment and
switch generator to reset (momentary position) and then ON. If the GEN annunciator remains
illuminated, land as soon as practical.
SEP 2012 R66 Maintenance Manual Chapter 96 Electrical System Page 96.1
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