Flytec 5030 v2.24 * - Manual (Page 45)

Flytec
5030 GPS
of the speed scale, in the area of the best glide and the speed of the minimal sink rate.
(Maximum speed achieves nothing!) Each speed should be maintained evenly over several
seconds. With the aid of FLYCHART- PC program, the data attained can be analyzed and
the polar curve can be determined. This polar curve can now be entered manually into the
Flytec 5030 GPS in the Set Mode.
Two polar curve points only are needed for the input.
1) The velocity (km/h or mph) and the value of the minimum sink rate (m/sec or ft/m).
At this position the polar curve runs horizontally;
2) A pair of values in the upper speed range. (not at max. speed )
It doesn't make sense to mislead yourself; too good a polar curve will, in the end, require a
speed that is too high. Because the input of both polar curve points always result in “true”
values, the middle altitude at which the polar curve was flown has also to be recorded. In
the polar curve chart, which is calculated by the instrument (a value pair for each km/h), all
of the documented polar curve points are converted and saved as “Indicated”. This means
that this polar curve is valid for all altitudes.
5.5 McCready Theory - Optimized Speed to Fly
In contrast to the simple required speed which allows us to reach a goal with the least
possible loss of altitude (which is synonymous with the maximum safety against landing out),
one can get to a goal in the shortest possible time with the help of the McCready theory.
Therefore, competition or record pilots have to deal with this theory. If a pilot finds him/her
self thermalling up in order to approach a goal (that can be a turning point, a landing field, or
even the next thermal source), then he/she must consider whether to leave the thermal as
early as possible in order to reach the goal at best glide, or whether it is better to thermal up
higher in strong lift and then glide with higher speed to goal.
McCready has found that with a given polar curve, there is only one departure altitude that
enables one to reach the goal in the shortest time. This departure altitude is dependent on
the average climb in the thermal and the prevailing wind component. The speed for the final
approach is primarily dependent on the average climb in a thermal.
Because the Flytec 5030 GPS knows all the parameters during thermalling , it can give the
all clear to the pilot to leave the thermal to reach the selected goal as fast as possible.
The unit works, making the presumption that, on the glide path to goal, rising and sinking air
neutralize each other and the wind remains constant. Because these conditions do not
always exist, it is also dependent on experience and care by the pilot to climb to safety
height above the glide path before leaving the thermal. This height above glide path,
determined in advance, is continuously recalculated and displayed. In addition McCready
discovered that, exactly as with speed to fly, the speed of the best glide depends on the
sinking of the surrounding air mass. The same flight speed can also be used for the fastest
possible arrival at your goal if one takes the average lift in a thermal instead of the sinking air
mass. In other words, if the average climb in the last thermal was 2 m/sec, the pilot who will
reach his/her goal first is the one who circles up high enough that best Speed to Fly,
corresponding to a sinking air mass of 2 m/sec, can be flown directly to the goal.
With earlier mechanical vario pilots constructed a ring, which was arranged to swivel around
the circular vario scale. In the centre of this McCready Ring a thick arrow stood opposite the
vario zero point of the vario. (This is the ring position for the best glide.) In the lower half of
the ring, were the required speed recommendations. (in km/h). To use it, the pilot first had to
turn the ring so that the arrow stood opposite the average climb mark on the vario scale.
Next he/she was able to read the recommended speed behind the current vario indication.
Then he/she corrected his flight speed following the recommendation, which of course
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