Flytec 6030 * - Manual (Page 53)

Flytec 6030-GPS
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GPS enabled, then this raise of best flight speed shall automatically be considered for the
displayed arrow of Speed to Fly.
On the contrary to sailplane gliders, for which the polar curve measured by the manufacturer
remains valid for a long time, there is in regard to hang gliders and even more so for para
gliders, the polar curve dependent on the age of the surface, the state of the sail canvas,
the pilot’s weight, his harness set and other conditions.
In order to manage the best possible use of Speed to Fly for the flights to come, it is
necessary to enter the polar curve as precisely as possible; which means that it should
be flight experienced by the pilot himself. It is self-evident that such a measuring flight
will provide best results if possible under calm air conditions. The value doublets are
particularly interesting (speed and its related sink rate) in the upper third of the speed scale,
(maximum speed achieves nothing!) within the range of best glide and the speed of minimum
sink rate. Each speed value should be kept evenly over several seconds. With the help of
the Flychart software the data obtained are easily to be analysed and the polar curve to be
determined. The can now be entered manually as polar curve in Set-Mode into the
FLYTEC 6030 GPS.
Two polar curve points are only required for the data entry:
1.) the velocity (km/h) and the value of minimum sink rate (m/s). At this position the polar
curve runs horizontally.
2.) A value doublet in the upper speed range.
It makes no sense to mislead yourselves, too good a polar curve will in the end require a
speed to fly that is too fast. Because the entry of both polar curve points always has to be
effected as „true“ values, the middle altitude at which the polar curve was effectively flown
has also to be entered. In the polar curve chart calculated by the instrument (one value
doublet for each km/h), all saved polar curve points are converted and stored as „Indicated“.
This means that this polar curve is valid for all altitudes.
9.5.2 Travel optimised Speed to Fly according to McCready
In contrast to the simple required speed which allows to reach a goal with the least possible
loss of altitude (which is synonymous with the maximum safety against landing out), one can
reach a goal with the help of the McCready theory in the shortest possible time. For this
reason, competition or record pilots have to deal with this theory. If a pilot finds himself
thermalling up in order to approach a goal (this might be a waypoint, a landing point or
even the next thermal source), then he will consider whether to leave the thermal as early as
possible in order to reach the goal at best glide, or whether it would be better to thermal up
higher in strong lift and then fly on the glide path with higher speed to goal.
McCready has discovered that with a given polar curve, there is only one departure altitude
that enables someone to reach the goal within the shortest possible time. This departure
altitude is dependent on the average climb and on the prevailing wind component. The speed
for final approach is primarily dependent on the average climb in a thermal.
When taken seriously, the McCready theory is only valid if one flies from thermal to thermal
and if there is no difference in altitude between take-off and landing. It has been developed
for sailplanes being flown over flat territory.