P/N 11934-003 7-73
Cirrus Design Section 7
SR20 Airplane Description
and illuminates the warning light when the voltage is less than
approximately 24.5 volts.
• Note •
The LOW VOLTS warning light may come on during extended
low RPM operation with heavy electrical loads. Under these
conditions, the light will go out at higher RPM.
ALT Fail Caution Lights
Two ALT Fail caution lights are installed in the annunciator panel. The
ALT 1 and ALT 2 caution lights in the annunciator panel provide
annunciation of alternator failure or overcurrent conditions at the
respective alternator. The lights are operated by circuits in the MCU
and current sensors on the ALT 1 and ALT 2 output lines. Steady
illumination of either light indicates an alternator failure. Serials 1268
through 1581: A flashing ALT light indicates an overcurrent condition.
Circuit Breakers and Fuses
Individual electrical circuits connected to the Main, Essential, and
Non-Essential Buses in the airplane are protected by re-settable
circuit breakers mounted in the circuit breaker panel on the left side of
the center console.
Essential Buses
The circuit breaker panel Essential Bus is powered by ALT 2 from the
MCU Essential Distribution Bus through the 20-amp ESSENTIAL
POWER circuit breaker and from BAT 2 through the 20-amp
BATTERY 2 circuit breaker. The Essential Bus is also powered by
ALT 1 and BAT-1 through an isolation diode connecting the Main and
Essential Distribution Buses in the MCU. The autopilot and Essential
avionics equipment are powered directly from the Essential
Distribution Bus in the MCU through a 25-amp circuit breaker on the
Distribution Bus. Power from the 15-amp AVIONICS circuit breaker is
also controlled through the AVIONICS master switch on the bolster
switch panel.
Main Buses
The circuit breaker panel Main Bus 1 and Main Bus 2 are powered by
ALT 1 and BAT 1 from the MCU Main Distribution Bus through 25-amp
circuit breakers on the Distribution Bus. ALT 2 and BAT 2 are
Revision A5
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