Flytec 6030 * - Manual (Page 56)

Flytec 6030-GPS
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9.5.3 Final glide calculation
Here the GPS-Data and the McCready theory go hand in hand. Please also read the section:
9.5.2. Travel optimised Speed to Fly according to McCready. Principally it is about reaching
a goal (of course it must be logged as a waypoint in the list) as fast as possible, or rather,
to get a signal from the instrument of when the last thermal can be left in order to arrive
at the WP as fast as possible. In order to be able to establish a statement about this, the
distance to this location must be known. This distance will be calculated with help of the
GPS-Receiver. In addition, we need the altitude of the waypoint (is mentioned in the list
of waypoints), as well as the current altitude of the pilot. From this smallish amount of
information it is possible to calculate the required glide ratio over ground (L/D req.)
which is necessary to reach the goal. For this purpose all other conditions, such as climb,
sink, wind and wind direction, flight speed and polar curve, are not taken into consideration.
The required glide ratio can be displayed in the user defined fields: L/D req.
It is only when the flyable glide ratio (over ground) has to be determined, that the before
mentioned conditions have indeed an important role.
Basically the final approach consists of two phases which are to be considered separately:
1.)
Climbing in the last thermal and
2.) the straightest possible glide path to the goal.
1.) Let’s assume that the pilot is circling under a cloud in quite a good thermal which provides
him an average climb of 2 m/s. While circling he will naturally try to fly with the speed for
minimum sink. Besides the chart for polar curve in the memory of FLYTEC 6030 GPS, there
is a second table calculated as “S2F (speed to fly)”, which knows the related McCready
speed for each average climb (30 sec Integrator) in a thermal. In relation to this there is
the glide ratio (through the air). If, while circling, the nose of the aircraft turns again and again
in the direction of the goal, the wind component, and, derived from this the wind factor,
may be determined at this moment and consequently the glide ratio over ground (Gnd)
be calculated.
At zero wind the wind factor is = 1; at tail wind > 1 and with head wind < 1.
From the distance to goal and the glide ratio (gnd) the FLYTEC 6030 GPS calculates the
loss in height which the pilot requires on his glide path to the goal. If the altitude of the goal is
added
(for each waypoint also its altitude is saved), then we obtain directly the optimal departure
altitude. As the own altitude is known, therefore the instrument can display directly by
comparison (in the screen Alt a. WP), if we still have to thermal up to arrive as the fastest
one, or if we are already above the fastest glide path.
It is of course subject to the pilot’s experience whether he wants to take-off immediately upon
positive Alt. a WP, or whether he will prefer to climb up further and take some reserve
altitude.
The FLYTEC 6030 GPS naturally does not know whether in the course of the glide path
lifting or
sinking air mass zones are present, or if the wind intends to change. The instrument
calculates with the current wind and assumes that no lifting or sinking zones are to be
expected.
2.) Gliding down to Goal
The pilot has left the thermal at the moment, when the FLYTEC 6030 GPS shows „Alt a. WP“
= 0