____________________________________________________________________
Page 3-4
Cirrus Perspective™ Line Maintenance Manual
Rev. E
190-00920-00
3.1
FLIGHT
INSTRUMENTATION
The
GRS
77
AHRS,
GDC
74A
Air
Data
Computer,
and
GMU
44
Magnetometer
provide
the
system
with
flight
instrumentation
data.
The
data
consists
of
aircraft
attitude,
heading,
altitude,
airspeed,
vertical
speed,
and
outside
air
temperature
information,
all
displayed
on
the
PFD
(the
same
data
is
displayed
on
the
MFD
in
reversionary
mode).
Data
outputs
from
the
GRS
77
and
GDC
74A
are
sent
directly
to
the
PFD
using
ARINC
429.
Additional
communications
paths
connect
the
GRS
and
GDC
74A
to
GIA
63W
units
providing
quadruple
redundancy.
The
GRS
77
receives
GPS
data
from
both
GIAs,
airspeed
data
from
the
GDC
74A,
and
magnetic
heading
from
the
GMU.
Using
these
three
external
sources,
combined
with
internal
sensor
data,
the
GRS
accurately
calculates
aircraft
attitude
and
heading
(Figure
2
‐
1).
In
addition
to
using
internal
sensors,
the
GRS
77
uses
GPS
information,
magnetic
field
data,
and
air
data
to
assist
in
attitude/heading
calculations.
In
normal
mode,
the
GRS
77
relies
upon
GPS
and
magnetic
field
measurements.
If
either
of
these
external
measurements
is
unavailable
or
invalid,
the
GRS
77
uses
air
data
information
for
attitude
determination.
Four
GRS
77
modes
of
operation
are
available
and
depend
upon
the
combination
of
available
sensor
inputs.
Loss
of
air
data,
GPS,
or
magnetometer
sensor
inputs
is
communicated
to
the
pilot
by
message
advisory
alerts.
3.2
GFC
700
AUTOPILOT
The
GFC
700
is
a
fail
‐
passive
digital
flight
control
system
composed
of
multiple
Garmin
LRUs
and
servos.
The
following
functions
are
provided
by
the
GFC
700
in
a
Perspective™
installation:
•
Flight
Director
•
Autopilot
•
Pitch
Trim
•
Yaw
Damper
(optional)
3.2.1
Flight
Director
The
Flight
Directors
operate
within
the
GIA
63Ws
and
use
data
from
the
GARMIN
system,
including
air,
attitude,
and
flight
data,
to
calculate
commands
for
display
to
the
pilot
and
for
the
Autopilot.
Flight
director
command
bars
and
mode
annunciations
are
sent
to
the
PFDs
through
a
high
‐
speed
Ethernet
connection
for
display
to
the
pilot
and
copilot.
The
flight
director
operates
independently
of
the
autopilot
and
allows
the
pilot
to
hand
‐
fly
the
command
bars
if
desired.
3.2.2
Autopilot
The
autopilot
operates
within
two
GSA
81
servos
(pitch
and
roll).
Flight
director
data
is
processed
within
the
servos
and
turned
into
aircraft
flight
control
surface
commands.
The
autopilot
cannot
operate
unless
the
flight
director
is
engaged.
Summary of Contents for Cirrus Perspective SR20
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