User manual

XCSoar User Manual
The glide computer assumes the glider’s average cross-country
speed is equal to that achievable under classic MacCready theory
taking wind into account, with the current MacCready setting.
The next major release of XCSoar will allow several ways of cal-
culating time estimates:
• MacCready speed (as currently implemented)
• Task average, the average speed achieved on this task.
• Manual input, so the user can specify the expected average
speed
Task speed estimates for achieved speed so far, are compensated
for altitude variations, such that the effects of climbs are taken into
account in calculating the average task speed.
5.11 Optimal cruise track
In order to help reduce the cross-track error when flying between
non-final waypoints, XCSoar calculates an adjustment to the cruise
track, called the ’optimal cruise track’. This track is adjusted so
that it compensates for the wind drift incurred when circling, and
as such it needs to estimate the proportion of time spent circling
according to classical MacCready theory.
The optimal cruise track is displayed on the map area as a large
blue arrow, and it recommends the glider steers so that the glider’s
track is lined up with the blue arrow during cruise. For example,
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