The Turn Area Task (TAT) offers extensive flexibility for cross country or racing tasks, but as a result, it can be difficult to optimize your performance.
This article describes a number of tools included in the ClearNav flight computer to help realize the best performance possible in a TAT. These tools include the ellipse, estimated speed to finish, the leader line and the ability to set a point in a turn area in place of the ellipse.
The ClearNav ELLIPSE (curved blue line) in the turn area you are in, or navigating to, is the locus of points that will give an equal distance from your present position to the ellipse and then to the next turn area (usually the center) or the finish.
The position of the ellipse is calculated to give a total task time equal to the assigned task time based on the time used so far and the calculated remaining speed to the finish.
Thus, the ellipse allows the pilot the to choose a route that optimizes soaring conditions while remaining confident he will achieve the distance required to arrive close to the minimum task time.
Early in the first leg of the task, the ellipse will have minimal importance, as the estimated speed to the finish is not based on enough data to be reasonably accurate.
Also, it is likely the pilot will elect to fly beyond the ellipse in the first turn area if soaring conditions are good to allow more flexibility later in the task.
The ellipse will be present in the turn area you are in or are navigating to, and target points will show in subsequent turn areas. When a subsequent turn area becomes the destination turn area, (or when a turn area point is designated- see below) the ellipse will move to the new destination turn area and will be drawn through the previously displayed point.
The ellipse is always moved first if a change is required to keep the Total Task Time equal to the Assigned Task Time. Points in subsequent turn areas are moved in sequence if necessary. For example, if you are going to be under time, the ellipse in the current turn area will first move to the far edge of the turn area before the point in the subsequent turn area is moved. This logic keeps the most flexibility and margin by keeping the target point in the last turn area in the center as long as possible.
You will find that later in the flight (last turn area), the ellipse will be quite accurate in predicting where to turn to come home within a minute or so of the assigned time.
However, in some cases the “calculated remaining speed” may be incorrect due to conditions on the last leg of the task being significantly different from earlier in the task. This includes a really good cloud street or ridge on the last leg, or conditions degrading overall. In this case, the prudent pilot will choose “Manual Speed” on the Task Action page and enter his best estimate of the remaining speed to finish. This will make suitable adjustments to the ellipse in the last turn area and to the time to finish.
The LEADER LINE (blue line extending in front of the glider symbol) is the extension of a line drawn through the previous turn (or start) and the glider. This represents the most efficient direction of flight for adding additional distance made good (DMG) on the active leg.
As you fly a given leg of the task, you will note the course line will adjust its intersection point with the ellipse to match the direction of the leader line, thus showing the most efficient line (DMG) to the ellipse based on your track so far.
Note that flying along the ellipse is quite inefficient in adding DMG, thus when approaching the ellipse, the leader line assumes greater importance in choosing your course line.
If you elect to go deeper into the turn area than the ellipse, because of good soaring conditions for example, the ellipse will automatically move to the next turn area, thus disappearing from the current turn area. This is logical because at this point, the leader line is the best tool for showing the most efficient route deeper into the turn area, and the ellipse will now be available in the next turn area for route planning of the next leg. If the next turn area is not visible on the map page, it may be viewed on the Task Map page.
When in a turn area, but still short of the ellipse, a button labeled “Ellipse Next TA” is available. If this button is selected, the ellipse will move to the next turn area and will disappear from the current turn area. Another button, “Ellipse This TA” will now become available. At any time before reaching where the ellipse would be if it were still in the current turn area, you can move the ellipse back to the current turn area by selecting the “Ellipse This TA” button. You can turn at any point, or, continue to fly deeper into the current turn area. In either case, the task statistics will update correctly.
In the last turn area when short of the ellipse, a button labeled “Turn Here” will be displayed. Selecting that button will shift the destination to the finish. If you fly past the ellipse in the last turn area, the ellipse will disappear, the destination will shift to the finish and the task total time will begin to count up beyond the assigned task time.
If at any time this becomes confusing, you can always go to the Task Action page and find the button you are looking for!
A new feature is SET TURN AREA POINT. If you wish to navigate to a specific point in a turn area instead of to an ellipse, you can move the cursor box with the arrow keys placing the cross in the center of the box at the desired point to navigate to, press select to bring up the dialog box and select “Set Turn Area Point”. The ellipse will then move to the next turn area and the course line will move to the desired point. The destination will remain the current Turn Area until you are within a kilometer of the desired turnpoint, or when you select “Turn Here” which will appear when you enter the turn area with the selected point. Your task statistics will update correctly even if you do not select “Turn Here” and the destination will change when you exit the current turn area.
The set turn area point feature can be quite useful for task planning if you know you want to fly past the ellipse in the current turn area.
Once set, you can change your turn area point, by moving the cursor box to the new desired point and repeating the process.
You can always retrieve the ellipse to the current turn area after setting a point (assuming you have not already passed it) by selecting “Turn Here”, and then going to the Task Action page and selecting “Ellipse This TA”.
While this all sounds complicated, it is really quite simple in flight. Give it a try!
Note 1 - Based on glide speed and glide ratio achieved, climb rate achieved, MC setting, and altitude