Avidyne IFD540 Pilot's Manual page 83

COOL FEATURE
Fuel Range Ring
The green fuel range ring depicted on the map
provides a visual indication of the max range of the
aircraft, allowing a 45-minute reserve. Winds are
indirectly taken into account. The calculation uses
groundspeed to compute the size of the circle and is
based on the value of the fuel totalizer. The dashed
green circle indicates the total maximum range
without using the reserve. A wider solid green circle
indicates the extra range the reserve fuel should
provide. The circle turns yellow indicating that only
reserve fuel remains. The rings are always
displayed and cannot be turned off.
The indications depicted are for a maximum fuel
range, calculated with reference to the current
groundspeed and the remaining fuel as indicated by
the fuel totalizer. Changes in power settings or
winds aloft or inaccurate fuel totalizer data will alter
your range and endurance depiction. There will be
no fuel range rings depicted if the IFD is not
connected to a fuel flow system. An inaccurate
manual entry of initial fuel will result in an inaccurate
fuel range ring depiction.
Map Pages 3-7