Garmin GPS III Pilot - Manual (Page 53)

With the profile set, the HSI Page will guide you through the maneuver. Data fields
on the HSI Page can be configured to indicate the time to beginning of maneuver, glide
ratio and vertical speed to target. A VNAV indicator on the HSI display will guide you
along the proper descent angle. Expect the following to occur when using the vertical
navigation feature:
• As you approach the initial descent point, the time to vertical navigation
(‘Time to VNV’) field indicates the time to reach the initial descent point.
• At one minute prior to the initial descent point, a message ‘Approaching
VNAV Profile’ occurs. The time to vertical navigation (‘Time to VNV’) will
sequence from indicating time to initial descent point to indicating time to
reach target altitude. Finally, the descent angle will lock to prevent changes
in speed from altering the profile.
• At 500 feet above the target altitude, an ‘Approaching Target Altitude’ mes-
sage is provided. The time to vertical navigation (‘Time to VNV’) figure will
go blank and the VNAV indicator will disappear from the HSI Page.
WARNING: GPS accuracy may be degraded by the U.S. Department of Defense-
imposed Selective Availability (SA) program. With ‘SA’ on, GPS altitude may be in error
by several hundred feet. Errors of this magnitude may result in fluctuations in the
VNAV indicator on the HSI Page. The GPS III Pilot is a VFR navigation tool and should
not be used to perform instrument approaches.
Within one minute of the
initial descent point, an
‘Approaching VNAV Profile’
message will appear.
Once you are within 500 feet
of the target altitude, the
‘Approaching Target Altitude’
message will appear and the
VNAV indicator will be
removed from the HSI
display.
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REFERENCE
Vertical Navigation
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GPS III Pilot B2 4/1/99 2:02 PM Page 45