Cirrus SR22 Pilot Operating Handbook page 242

Section 7 Cirrus Design
Systems Description SR22
through 30-amp fuses inside the MCU and also by BAT 2 through the
20-amp BAT 2 circuit breaker.
In the event of ALT 1 or ALT 2 failure, the Essential Buses in the circuit
breaker panel will be powered by the remaining alternator through the
Main Distribution Bus 1 or Main Distribution Bus 2 in the MCU. In the
case of both alternators failing, BAT 1 is connected directly to the
Essential Distribution Bus in the MCU and will power ESS BUS 1 and
ESS BUS 2. In the event of both alternators and BAT 1 failing, BAT 2 is
connected directly to ESS BUS 1.
Main Buses
The circuit breaker panel MAIN BUS 1 and MAIN BUS 2 are powered
by ALT 2 from the MCU Main Distribution Bus 2 and - in the event of
ALT 2 failure - by ALT 1 and BAT 1 from the Main Distribution Bus 2 via
the diode interconnecting the MCU distribution buses through 30-amp
fuses inside the MCU.
The 10-amp AVIONICS circuit breaker on MAIN BUS 1, controlled
through the AVIONICS master switch on the bolster switch panel,
powers all loads on the AVIONICS BUS.
The circuit breaker panel MAIN BUS 3 is powered by ALT 1 and BAT 1
from the MCU Main Distribution Bus 1 through a 30-amp fuse inside
the MCU. In the event of ALT 1 failure, BAT 1 will power MAIN BUS 3.
ALT 2 is prevented from powering MAIN BUS 3 by the isolation diode
interconnecting the MCU distribution buses 1 and 2.
Non-Essential Buses
The circuit breaker panel NON ESS BUS is powered by ALT 2 from
the MCU Main Distribution Bus 2 and - in the event of ALT 2 failure -
by ALT 1 and BAT 1 from the Main Distribution Bus 2 via the diode
interconnecting the MCU distribution buses through 30-amp fuses
inside the MCU. The Avionics Non-Essential Bus is powered through
the 10-amp AVIONICS circuit breaker on MAIN BUS 1 and is
discussed above.
The circuit breaker panel A/C BUS 1 and A/C BUS 2, is powered by
ALT 1 and BAT 1 from the MCU Main Distribution Bus 1 through a 30-
amp fuse inside the MCU. In the event of ALT 1 failure, BAT 1 will
power A/C BUS 1 and A/C BUS 2. ALT 2 is prevented from powering
A/C BUS 1 and A/C BUS 2 by the isolation diode interconnecting the
MCU distribution buses 1 and 2.
7-56 P/N 13772-004
Revision 1