Cessna SkyHawk SP 172S NAV III 2005 Pilot Operating Handbook page 364

CESSNA
MODEL 172S NAV III
SECTION 9 - SUPPLEMENTS
SUPPLEMENT 3
NORMAL PROCEDURES
(Continued)
4. NAV Button - PUSH to arm the autopilot NAV lock on
function. Make sure that the autopilot is correctly engaged
from the annunciation on the autopilot:
a. If the HSI D-Bar is less than 2 to 3 dots from center, the
autopilot will go to NAV mode. The NAV annunciator
will be shown on the face of the autopilot.
b. If the HSI D-Bar is more than 2 to 3 dots from center,
the NAVARM annunciator will be shown on the face of
the autopilot. When the computed intercept point is
reached, the ARM annunciator will go off and lock on
(capture and track) will begin automatically. The NAV
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annunciator will stay on the face of the autopilot.
GPS NAV AND ROLL STEERING
The KAP 140 Autopilot has DC (analog) Roll Steering capability.
Roll Steering enables the Flight Guidance System (in this case, the
G1000 GPS navigation computer) to control the autopilot through
automatic course changes at flight plan waypoints and to lock on to
the course to the next waypoint.
The GPS navigation computer uses ground speed, track and turn-
rate data to calculate the bank angle required for waypoint course
changes (the KAP 140 limits bank angle in the 172S to
approximately 18°). The GPS Roll Steering signal will make the
autopilot turn the airplane and lock on course to the next waypoint
without flying directly over the current waypoint, except for
designated fly-over waypoints. The flight path is approximately
tangent to the inbound and outbound flight plan legs.
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FAA APPROVED
172SPHAUS-S3-00
U.S. S3-35
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