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Therefore SinkA is the minimum sink rate and VA is the speed at which this is achieved.
The glide ratio is the ratio between the glider’s horizontal speed and the sink rate. To
find the best glide rate on the graph, a straight line is from the origin of the graph (point
O) to the tangent of the curve (point B). The speed to fly at to achieve the best glide (air
related) is therefore VB and the glide ratio is VB/SinkB.
On your instrument you can insert three different polars, go to (ADVANCED SETUP \ n.
9/17 PX-A/B/C) and choose which polar to use, go to (ADVANCED SETUP \ n. 8 POLA).
If this parameter (ADVANCED SETUP \ n. 8 POLA) is set to “OFF”, all information
relating to McCready, McCready Equivalent, Thermal Sniffer is not displayed on the
instrument, creating a cleaner display for users not needing this functionality.
There are three polars preloaded, (2 for hang gliders and 1 for a paraglider). To see the
three default polar curves and to calculate your own, use the Digifly Excel software
available from the Digifly web site (www.digifly.com).
We suggest that you insert your own polar curve data which best reflects the actual
performance of your glider.
6.5
SPEED TO FLY
To utilize the speed to fly functions you must have an air
speed probe connected. The optional air speed probe should
be plugged in to the right hand socket on the bottom of the
vario.
If this parameter (ADVANCED SETUP \ n. 8 POLA) is set to “OFF”, all information
relating to McCready, McCready Equivalent, Thermal Sniffer is not displayed on the
instrument, creating a cleaner display for users not needing this functionality.
The speed to fly value is the optimum flying speed to obtain the best glide ratio. This
value depends on performance of your glider as well as vertical and horizontal airflow.
In calm air, the optimum flying speed is the same as the best glide speed (point B on
the figure below).
