Cirrus SR22 Pilot Operating Handbook page 280

Section 7
Systems Description
Approach Baro-VNAV
While executing an LNAV/VNAV approach with SBAS unavailable,
Baro-VNAV is used for vertical approach guidance. This occurs due to
any of the following conditions:
• SBAS fails or becomes unavailable prior to final approach fix
(FAF)
• the aircraft is outside SBAS coverage
• SBAS is manually disabled on the GPS Status page (To
simulate a Baro-VNAV approach, SBAS must be manually
disabled prior to activation of the approach procedure.)
Baro-VNAV is also the source of vertical approach guidance if the
LNAV/VNAV procedure does not support SBAS vertical guidance.
While Baro-VNAV is being utilized, the Glidepath Indicator appears as
a magenta pentagon. If the approach type downgrades past the FAF,
"NO GP" is displayed in place of the pentagon.
While executing an LNAV/VNAV approach, between FAF and missed
approach point (MAP), excessive deviation indicators appear as
vertical yellow lines to indicate an area where the vertical deviation
exceeds ±75 feet.
Autopilot Interface
The GFC 700 Automatic Flight Control System uses the GP mode via
the APR button to follow Approach Baro-VNAV guidance, as opposed
to the VNAV mode via the VNV button. When coupled in GP mode, the
GFC 700 will not capture a preselected altitude while tracking a Baro-
VNAV glidepath.
Approach Downgrades
For approaches with minimums that support both SBAS and baro
altitude vertical guidance, downgrading or reverting to barometric
altitude guidance is allowed prior to 60 seconds before the FAF. If
SBAS becomes unavailable after the approach is active but prior to 60
seconds before the FAF, an approach downgrade may be performed
(e.g. LPV to LNAV/VNAV) or a vertical source reversion to baro
altitude may be performed (e.g. SBAS LNAV/VNAV to baro LNAV/
VNAV).
If a loss of SBAS occurs prior to 60 seconds before the FAF, the
system will determine whether or not the approach mode can be
supported using Baro-VNAV. If Baro-VNAV can be supported, the
"APR ADVISORY - SBAS VNAV not available. Using Baro VNAV."
7-94
Cirrus Design
SR22
P/N 13772-004
Revision 1