Cirrus DESIGN SR22T Pilot Operating Handbook page 489

Cirrus Design Section 9
SR22 / SR22T Supplements
GPSS converts this information and sends this heading error directly
to the autopilot.
In the GPSS mode the autopilot can be directly coupled to the roll
Commands produced by the GPS Navigator, eliminating the need for
the pilot to make any further adjustments to the HSI course arrow.
ALT - Altitude Hold Button
When ALT is selected, the autopilot will hold the altitude at the time the
mode was selected. Altitude hold will not engage if an autopilot roll
mode is not engaged. Altitude correction for enroute barometric
pressure changes may be made by rotation of the VS knob on the
Programmer/Computer.
VS - Vertical Speed Button
When VS is selected, the autopilot will synchronize to and hold the
vertical speed at the time the mode was selected. Altitude hold will not
engage if an autopilot roll mode is not engaged. The vertical speed is
displayed in 100-foot increments at the far right of the Programmer/
Computer window next to the VS annunciation. A plus (+) value
indicates climb and a negative or minus (-) value indicates descent.
Vertical speed can be adjusted by rotating the VS knob on the
Programmer/Computer.
APR - Approach Button
When APR is selected, the autopilot provides increased sensitivity for
VOR or GPS approaches. APR may also be used to provide increased
sensitivity for enroute course tracking
REV- Reverse Course Button
When REV is selected, the autopilot will automatically execute high
sensitivity gain for an approach where tracking the front course
outbound or tracking the back course inbound is required. The APR
and REV annunciations will illuminate when REV is selected.
TRIM - Autotrim Mode
When both a roll mode and a pitch mode are engaged, the autopilot
will provide an annunciation whenever it is automatically trimming the
aircraft. Should the pitch servo loading exceed a preset threshold for a
period of three seconds, the autopilot will annunciate either TRIM  or
TRIM  as an advisement that the autopilot is automatically trimming
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Revision 01: 01-06-10