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APPENDIX C
Troubleshooting Q & A
217
190-00357-00 Rev E
minalmodetoapproachmode.CDIscalingistightened
from 1.0 NM full scale deflection to either 0.3 NM or 2°
full scale deflection whichever is less at the FAF. The scal-
ing change occurs gradually over a 2 NM distance and is
completed before crossing the FAF.
IfVectorstoFinalisselected,theunitprovidesCDI
scaling appropriate to the approach, which is typically ±2
degrees angular from the origin of the approach. This an-
gular course deviation reaches the max ±1 NM deviation
at approximately 27 NM from the MAP. The course width
and angular deviation for GPS approaches are similar to
whatisprovidedforVHFlocalizersignals.(seetheg-
ure–Full-ScaledeectionanddenedpathforVTFap-
proach).
Ifamissedapproachisexecuted,theCDIscalewill
change to ±0.3 NM or ±1.0 NM, as described in Section
5 - Procedures - Flying the Missed Approach.
Full-Scale deflection and defined path for normal approach
Sensitivity must change from ±1 NM FSD to either ±0.3 NM or
±2° FSD, whichever is less at the FAF. Change occurs over 2 NM
and is completed at the FAF.
Full-Scale deflection and defined path for VTF approach
Why does my CDI not respond like a VOR when OBS
mode is active?
UnlikeaVOR,theCDIscaleusedonGPSequipment
is based on the cross-track distance to the desired course
in OBS mode, not an angular relationship to the desti-
nation.Therefore,theCDIdeectionontheGPSiscon-
stant regardless of the distance to the destination and does
not become less sensitive when you are further away from
thedestination.FormoreinformationontheCDIscale,
see Section 9 - Aux Pages - Setup Page (CDI/Alarms).
2 NM2 NM 2 NM2 NM
1
NM
1
NM
CDI Comparison: GPS vs. VOR