Electrical System Control - Cirrus DESIGN SR22 Pilot Operating Handbook

Cirrus Design
SR22

Electrical System Control

The rocker type electrical system MASTER switches are 'on' in the up
position and 'off' in the down position. The switches, labeled BAT 2,
BAT 1, ALT 1, ALT 2 are located in the bolster switch panel
immediately below the instrument panel. These switches, along with
the AVIONICS power switch, control all electrical power to the
airplane.
Battery Switches
The BAT 1 and BAT 2 switches control the respective battery. Setting
the BAT 1 switch 'on' energizes a relay connecting BAT 1 to the MCU
Distribution Buses (also energizing the circuit breaker panel buses)
and the open contacts of the starter relay. Setting the BAT 2 switch 'on'
energizes a relay connecting BAT 2 to the circuit breaker panel ESS
BUS 1. Normally, for flight operations, all master switches will be 'on'
However, the BAT 1 and BAT 2 switches can be turned 'on' separately
to check equipment while on the ground. Setting only the BAT 2 switch
'on' will energize those systems connected to the circuit breaker
panel's ESS BUS 1 and ESS BUS 2. If any system on the other buses
is energized, a failure of the Distribution Bus interconnect isolation
diode is indicated. When the BAT 1 switch is set to 'on,' the remaining
systems will be energized. To check or use non-essential avionics
equipment or radios while on the ground, the AVIONICS power switch
must also be turned on.
Alternator Switches
The ALT 1 and ALT 2 switches control field power to the respective
alternator. For ALT 1 to start, the BAT 1 switch must be 'on'. Setting the
ALT 1 switch 'on' energizes a relay allowing 28 VDC from the 5 amp
ALT 1 circuit breaker on A/C BUS 1 to be applied to a voltage regulator
for ALT 1. For ALT 2 to start, either the BAT 1 switch or the BAT 2
switch must be 'on.' Setting the ALT 2 switch 'on' energizes a relay
allowing 28 VDC from the 5 amp ALT 2 circuit breaker on ESS BUS 2
to be applied to voltage regulator for ALT 2. Positioning either ALT
switch to the OFF position removes the affected alternator from the
electrical system.
Continued operation with the alternators switched off will
reduce battery power enough to open the battery relay,
remove power from the alternator field, and prevent alternator
restart.
P/N 13772-002 P/N 13772-002
Reissue A
• Caution •
Section 7
Systems Description
7-53 7-53