User`s manual

4 CROSS COUNTRY TASKS
4.6 AAT
AAT Targets
A target is a point within an AAT area that the pilot intends to fly to. These targets can be moved
within the AAT areas so the pilot can adjust the effective distance of the task. Targets may be set
on the ground, during task planning, and modified during flight.
When flying an AAT task, the navigation system directs the glider to the target, and statistics like
distance to waypoint are also relative to the target rather than the waypoint of the AAT area itself.
Automatic task waypoint advancement normally triggers when entering an AAT area, so if the pilot
wishes to fly to the targets, either the ‘arm start’, ‘arm’ or ‘manual’ advancement modes should be
used when flying AAT tasks.
Manually moving targets
In order to make the specification of targets more straightforward, their location is defined by a
range parameter that determines how far from the minimum to maximum possible distance the
target is. This is expressed as a percentage. For example, with range set to 100%, the target is
located to give the maximum overall task distance. With range set to −100%, the target is located
to give the minimum overall task distance.
Zero range yields a nominal task distance: for sectors the target is half way along the bisector
radial; for cylinders the target is in the center of the cylinder.
The targets can be modified in two ways:
• In Task calculator (see 4.3), the ‘Set Range’ field adjusts the targets of all remaining
waypoints in the task.
• In Target (see 4.1), the range of each waypoint may be individually adjusted.
AAT targets and task calculator
Task calculator can be helpful to check the influence of changes (atmosphere, polar, MacCready,
etc) on the estimated task time. It is recommended to keep an eye on the task calculator during
an AAT task in order to be able to modify settings (e.g. MacCready, AAT target position, etc) if
necessary.
Target projection
XCSoar continually analyses the path of the glider through AAT sectors to find the points in previous
AAT sectors through which the achieved scoreable distance will be greatest. Internally, the program
moves the targets for previous AAT sectors, which are then the optimal targets.
In certain conditions, targets for the current AAT sector may be moved automatically:
• When inside an AAT sector, the target in that sector is moved to a line projecting from the
previous sector’s target through the aircraft, at the same distance from the previous sector’s
target to the target prior to entering the sector. The effect of this is to allow pilots to choose
to enter an AAT sector in a different direction or offset from the direct line from the previous
target to the current target.
41 XCSoar Manual (Altair version) • XCSoar-A-EN