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In the example of Figure 5.2, the pilot is fiying to the ESS at a certain true air speed
(TAS). There is an optimum TAS value which minimizes the time to reach the ESS.
This value depends on the polar and cone ratio, and is not afiected by the wind or
thermals. The LIVE-SD calculates the optimal TAS value 56 and show this in the
OptSpdCone data field. In order to know the TAS the pilot needs a TASProbe. So for
the pilots who do not have the TASProbe the LIVE-SD calculates the optimal ground
speed by adding a Wind component to the TAS. The optimal ground speed is shown in
the OptGndSpdCone Data Field. Note: The OptGndSpdCone accuracy depends on the
wind accuracy. When the ESS is a cylinder the distance to the ESS does not depend
on the pilot altitude. On the contrary, when the ESS is a cone the distance to the ESS
depends on the altitude. Because of this, the LIVE-SD provide 2 distances in 2 difierent
data fields. The Dist.Cone data field shows the distance to the ESS at the current pilot
altitude (see Figure 5.2). As the glider glide ratio (GR) is usually positive and finite the
altitude at which the pilot reaches the ESS is difierent from the current altitude, so real
distance to the cone depends on the GR. The Dist.ConeA data field shows the
horizontal distance to the ESS considering the expected average GR trough the
remaining path (see Figure 5.2). Note: The expected GR is calculated considering
historical data and also the wind component at that direction. If a pilot is fiying at the
polar point corresponding to value indicated in the OptSpdCone data field it will take
him a certain time to reach the cone. There is a vertical speed (thermal speed) which
allows the pilot to climb and reach the cone in the same amount of time. This vertical
speed value is shown in the ConeVSpd data field and corresponds to the minimum
thermal speed which compensates climb instead of fiying straight to reach the cone
faster.
Note: The minimum thermal speed indicated in the ConeVSpd data field does not take
in account the wind drift. If the winds blows in the cone direction the minimum thermal
speed is lower than indicated, otherwise is higher.
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