Cirrus SR20 Pilot Operating Handbook page 267

Cirrus Design
SR20
3 and the 5-amp MFD 2 circuit breaker on MAIN BUS 1. Either circuit
is capable of powering the MFD. System start-up is automatic once
power is applied. Power-on default brightness is determined by
ambient lighting and is user adjustable.
GCU 478 Flight Management System Keyboard
The Flight Management System Keyboard is found on the upper
section of the center console and is the primary interface for avionics
system data entry, PFD/MFD operation, NAV/COM tuning, and
heading, course and altitude selection.
28 VDC for Flight Management System Keyboard operation is
supplied through the 5-amp KEYPADS / AP CTRL circuit breaker on
MAIN BUS 1.
GRS 77 Attitude and Heading Reference System (AHRS)
The Attitude and Heading Reference System (AHRS) unit(s), mounted
behind the PFD, provide airplane attitude and heading information to
both the PFD and the primary Air Data Computer. The AHRS units(s)
contain advanced sensors (including accelerometers and rate
sensors) and interfaces with the; primary Magnetometer to obtain
magnetic field information, the Air Data Computer to obtain air data,
and both Integrated Avionics Units to obtain GPS information.
28 VDC for AHRS 1 operation is supplied through the 5-amp AHRS 1
circuit breaker on the ESS BUS 1. If option installed, 28 VDC for
AHRS 2 operation is supplied through the 5-amp AHRS 2 circuit
breaker on the MAIN BUS 2.
GDC 74A Air Data Computer (ADC)
The Air Data Computer(s), mounted behind the instrument panel to
the right of the MFD, process data from the Pitot/Static system and
outside air temperature (OAT) sensor(s). This unit(s) provide pressure
altitude, airspeed, vertical speed and OAT information to the
Integrated Avionics System, and communicate with the primary PFD,
Integrated Avionics Unit, and AHRS units. The Air Data Computer(s) is
also connected directly to the Outside Air Temperature probe(s) and
Pitot-Static System.
28 VDC for ADC 1 operation is supplied through the 5-amp ADC 1
circuit breaker on the ESS BUS 1. If option installed, 28VDC for ADC 2
operation is supplied through a 5-amp AHRS 2 / ADC 2 circuit breaker
on the MAIN BUS 2.
P/N 21399-004 P/N 21399-004
Revision A1
Airplane and Systems Description
Section 7
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