Cirrus SR22 Pilot Operating Handbook page 285

C D
IRRUS ESIGN
SR22
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 guid-
ance 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." message will be displayed
on the PFDs and the vertical deviation indicator (VDI) will be flagged. If
SBAS is required for the approach, the approach mode (e.g. LPV) will be
shown in amber but the GPS/SBAS VDI will be displayed until 60 seconds
prior to the FAF. If the SBAS integrity has not been restored at 60 seconds
prior to the FAF, the system will display the "APR DWNGRADE - Apr
downgraded. Baro VNAV." message and flag the VDI.
Once the pilot acknowledges either message by viewing it on the PFD, the
VDI will be restored using baro altitude vertical guidance instead of SBAS.
There is no downgrade from SBAS to barometric altitude after the FAF or
within 60 seconds of the FAF; "LNAV" is the only downgrade option in
those cases. For approaches using barometric vertical guidance, downgrade
is not allowed; if altitude or temperature data becomes invalid, the vertical
deviation will be flagged.
Sensor Failures
Serials w/ single Air Data Computer (ADC) installations: The Outside Air
Temperature (OAT) from the ADC will be used. If the OAT becomes
invalid, the VDI will be flagged as invalid.
P/N 13772-006
Reissue A
S 7: A
ECTION IRPLANE AND
S
YSTEMS
A
VIONICS
7-79