User manual

XCSoar User Manual

Break-off height : This is the elevation above ground, below which it is recom-

mended for pilots to consider the cross-country task failed

and to concentrate on ﬁnding a suitable ﬁeld to land in. Cur-

rently this break-off height does not affect XCSoar in any

way but it is reserved for future use to provide warnings etc.

These may be set to zero but this is highly discouraged since all

glide computers, instruments and data sources (such as terrain el-

evation models) are subject to some degree of error and the atmo-

sphere through which the glider ﬂies is also unpredictable.

XCSoar determines the height above sea level of any turn point

or landing point either from the waypoint ﬁle, of if no height is

speciﬁed in the waypoint ﬁle, from the terrain ﬁle.

The estimated arrival altitude displayed next to landable waypoints

is calculated for best glide angle at zero MacCready ring setting

(Mc= 0), adjusted for wind.

Landable ﬁelds are only marked as reachable if the estimated ar-

rival elevation above ground is above the arrival altitude safety

height, and the glide path does not intersect the terrain clearance

safety elevation.

At all times, if the ﬁnal glide through terrain marker (a red cross)

is displayed on the screen, then the glider must climb in order to

safely reach the destination.

When calculating the arrival heights of landable ﬁelds (for map

display purposes and in abort mode), a safety MacCready value

can be speciﬁed in the conﬁguration settings. This safety value

is set to zero by default. Larger values make the arrival height

calculation more conservative.