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Page 7-32
Cirrus Perspective™ Line Maintenance Manual
Rev. E
190-00920-00
7.4.3
GRS
77/GMU
44
Alignment
NOTE
Cirrus
Perspective™
system
software
allows
valid
outputs
from
the
AHRS
prior
to
completion
of
the
AHRS
and
magnetometer
calibration
procedures,
as
long
as
the
GRS
77
can
definitively
determine
that
the
aircraft
is
not
moving
.
This
gives
a
technician
the
ability
to
perform
functional
tests
during
aircraft
assembly
that
require
valid
AHRS
outputs.
Additionally,
a
“CALIBRATE
AHRS/MAG”
message
is
displayed
on
the
PFD
until
a
successful
magnetic
calibration
has
been
completed.
The
following
criteria
is
used
by
the
AHRS
to
determine
the
aircraft
is
moving:
1.
If
valid
GPS
data
is
available
and
each
component
of
3D
GPS
velocity
is
less
than
4
knots,
the
aircraft
is
considered
“not
moving”
and
attitude/heading
will
become
valid.
2.
If
valid
3D
GPS
data
is
not
available,
but
valid
true
airspeed
is
less
than
30
knots,
the
aircraft
is
considered
“not
moving”
and
attitude/heading
will
become
valid.
3.
If
both
3D
GPS
and
true
airspeed
are
unavailable,
attitude/heading
will
not
become
valid.
No
configuration
is
required
for
the
GRS
77,
unless
the
mounting
bolts
that
secure
the
mounting
rack
are
loosened.
If
the
mounting
bolts
are
loosened
a
new
post
‐
installation
calibration
is
required.
Any
GMU
44
that
is
removed
and/or
replaced
requires
a
magnetometer
calibration.
There
are
five
calibration
procedures
available:
•
Pitch/Roll
Offset
(Procedure
A1)
•
Magnetometer
Calibration,
(Procedure
B)
•
Heading
Offset
Compensation,
(Procedure
C)
•
Engine
Run
‐
Up
Vibration
Test,
(Procedure
D)
•
Magnetometer
Interference
Test,
(Procedure
E)
NOTE
Procedure
C
is
not
required
and
should
not
be
performed
on
Cirrus
Perspective™
aircraft.
Turn
the
PFD
and
MFD
off
by
pulling
the
PFD
and
MFD
circuit
breakers.
Restart
both
displays
in
configuration
mode.
Follow
the
steps
given
for
each
procedure
on
the
PFD
GRS/GMU
CALIBRATION
page.
The
CALIBRATE
command
cannot
be
selected
and
activated
until
the
installer
acknowledges
all
required
steps
have
been
carried
out
by
pressing
the
ENT
key
for
each
step.