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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 ALT 2 circuit breaker (Essential Bus) 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.
• Note •
Continued operation with the alternators switched off will
reduce battery power low enough to open the battery relay,
remove power from the alternator field, and prevent alternator
restart.
Avionics Power Switch
A rocker switch, labeled AVIONICS, controls electrical power from the
circuit breaker panel bus 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 avionics on the Avionics Non-Essential
and Essential Buses simultaneously. With the switch in the OFF
position, no electrical power will be applied to the avionics equipment,
regardless of the position of the master switch or the individual
equipment switches. For normal operations, the AVIONICS switch
should be placed in the OFF position prior to activating the MASTER
switches, starting the engine, or applying an external power source.
Volts and Ampere Meter/Indication
Serials 1268 through 1581: A 2¼” combination Volts and Ampere
meter is mounted on the right instrument panel outboard of the oil
temperature and pressure indicator. The indicator is internally lighted.
28 VDC for instrument lighting is supplied through the 2-amp INST
LIGHTS circuit breaker on Main Bus 1.
The VOLT pointer sweeps a scale from 16 to 32 volts. Refer to Section
2, Limitations, in basic POH for instrument limit markings. The voltage
indication is measured off the Essential Bus.
March 2010
7-72 Information Manual
Section 7 Cirrus Design
Airplane Description SR20
The AMP pointer sweeps a scale from -100 to +100 amps with zero at
the 9 o'clock position. The amps indication is derived from current
transducers located in the MCU. Output from each alternator and BAT
1 is measured. The panel mounted AMMETER SELECT switch is
used to select the desired indication. When the engine is operating
and the ALT 1 and ALT 2 Master switches are 'on,' the ammeter
indicates the charging rate applied to the batteries. In the event the
alternators are not functioning or the electrical load exceeds the output
of the alternators, the ammeter indicates BAT 1 discharge rate.
Alternator ammeter indications are positive only.
Serials 1582 and subsequent: Main and Essential Bus voltages are
shown as text in the electrical data block located in the mid-right
section of the MFD and are also displayed in the voltage parameters
block located in the upper left corner of the PFD when voltages fall
outside typical operating parameters. The MFD and PFD receive the
voltage signals via the DAU as measured directly off the Main and
Essential Buses.
In the event Main Bus voltage is less than 24.5v or exceeds 32.0v the
MFD will display “Check Main Bus” in a yellow advisory box in the
lower right corner of the MFD.
In the event Essential Bus voltage is less than 24.5v or exceeds 32.0v
the MFD will display “Check Main Bus” in a red advisory box in the
lower right corner of the MFD.
Alternator 1 and Alternator 2 ampere output are shown as text in the
electrical data block located in the mid-right section of the MFD. The
MFD and PFD receive the amp signals via the DAU as derived from
current transducers located in the MCU.
In the event Alternator 1 or Alternator 2 ampere output is less than 2
amps for 20 seconds or more, the MFD will display “Check ALT 1” or
“Check ALT 2” respectively, in a yellow advisory box in the lower right
corner of the MFD.
28 VDC for the digital instrument operation is supplied through the 2-
amp ANNUN / ENGINE INST circuit breaker on the Essential Bus.
March 2010
Information Manual 7-73
Cirrus Design Section 7
SR20 Airplane Description
Ammeter Select Switch
Serials 1268 through 1581: The AMMETER SELECT switch on the
instrument panel is used to select the desired source of electrical
current flow to be indicated on the ammeter. The switch has three
positions: ALT 1, BATT, and ALT 2. The BATT position indicates BAT 1
current flow only. Selecting one of the switch positions will cause the
amperage output from that device to be displayed on the ammeter.
Serials 1582 and subsequent: Main and Essential Bus voltages are
displayed on the MFD and PFD, therefore, no ammeter select switch is
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西锐20飞机信息手册CIRRUS DESIGN SR20 AIRPLANE INFORMATION MA(74)
