Cirrus SR20 - Electrical System; Low Voltage on Main Bus 1; Low Voltage on Main Bus 2

Cirrus Design Section 3A
SR20 Abnormal Procedures
P/N 21399-004 3A-11P/N 21399-004 3A-11
Electrical System
Low Voltage on Main Bus 1
M BUS 1 Caution
1. Perform ALT 1 Caution (Failure) Checklist.
Amplification
Main Bus 1 Voltage is low, indicates Alt 1 failure and will typically be
associated with low M1 voltage Alt 1 current indications, Battery 1
discharge and ALT 1 Caution message.
Low Voltage on Main Bus 2
M BUS 2 Caution
1. Perform ALT 1 Caution (Failure) and ALT 2 Caution (Failure)
Checklists.
Amplification
Main Bus 2 Voltage is low, indicative of dual Alt 1 and 2 failures and
will typically be associated with low M1 and M2 voltages, Alt 1 and Alt
2 current indications, Battery 1 discharge, ALT 1 & 2 and M BUS 1 & 2
Caution messages, and ESS BUS Warning message.
Battery 1 Current Sensor
BATT 1 Caution
1. Main Bus 1, 2 and Non-Essential Bus Loads...................REDUCE
2. Main Bus 1, 2 and Essential Bus Voltages .................... MONITOR
3. Land as soon as practical.
Amplification
Battery 1 discharge while Alt 1 is functioning normally, indicative of an
internal power distribution failure within the MCU.
M BUS 1
M BUS 2
BATT 1
Revision A1