Electrical System Control - Cirrus SR22 Pilot Operating Handbook

S 7: A
ECTION IRPLANE AND
E S
LECTRICAL YSTEM

Electrical System Control

The rocker type electrical system MASTER switches are 'on' in the up posi-
tion 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 master
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 Distri-
bution 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 master
switch must also be turned on.
Alternator Switches
The ALT 1 and ALT 2 switches control field power to the respective alter-
nator. 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.
AVIONICS Master Switch
A rocker switch, labeled AVIONICS, controls electrical power from the
circuit breaker panel (MAIN BUS 1) to the AVIONICS bus. The switch is
located next to the ALT and BAT Master switches. Typically, the switch is
used to energize or de-energize all non-essential avionics on the
AVIONICS bus simultaneously. With the switch in the OFF position, no
electrical power will be applied to the non-essential avionics equipment,
7-52
S
YSTEMS
• CAUTION •
C D
IRRUS ESIGN
SR22
P/N 13772-006
Reissue A