Task turn angles other than 180 degrees, when is it safe?

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So for race tasking it is a bad idea to call a task that has pilots do an out and return, 180° U-turn and turn back into oncoming traffic.
So a 0° angle between incoming and outgoing traffic certainly is bad.

What angle is sufficient to be relatively safe, 30, 40, 60?

And does this vary with the size of the turnpoint, 1 mile, 5 mile, 15 mile?

I think to make this easier to task for a CD this way it would help to have a lot bigger turnpoint list than the typical 30 points. With more points you can add steering points that create a safe turn without adding more distance than you want.

Chris

[Don Johnstone[_4_]]

At 23:02 16 December 2016, wrote:
>So for race tasking it is a bad idea to call a task that has pilots do
an
>o=
>ut and return, 180=C2=B0 U-turn and turn back into oncoming
traffic.
>So a 0=C2=B0 angle between incoming and outgoing traffic
certainly is bad.
>
>What angle is sufficient to be relatively safe, 30, 40, 60?
>
>And does this vary with the size of the turnpoint, 1 mile, 5 mile,
15 mile?
>
>I think to make this easier to task for a CD this way it would help
to
>have=
> a lot bigger turnpoint list than the typical 30 points. With more
points
>=
>you can add steering points that create a safe turn without adding
more
>dis=
>tance than you want.
>
>Chris

I always tried to make sure that the angle round the first turnpoint
was greater than 60, degrees, more if the first turnpoint was close
<50km, as this is where there is the greatest potential of large
numbers of gliders all being in the same area. Even with a longer
first leg the angle should be a great as possible as the tracks into a
turnpoint are more variable. After the first turnpoint the angle is not
so critical as the flield tends to get more spread, where gliders are
still close they tend to be in a group anyway and are aware of each
others position. If a control point is used near to the finish airfield
to bring the gliders in from one direction the track in/track out
angle should be as great as possible, speeds are likely to be
increased and pilots are in final glide mode. 180 degree turns
should be avoided where possible.
The one thing that you can almost be certain of is that gliders will
not fly on the track drawn on the task.

[Tim Taylor]

I agree with Don. I prefer to keep all turns at least 60 degrees. 45 should be the absolute minimum and should only be used as a last resort. The bigger the turn area the greater the angle should be. The scariest I have ever flown was a big ring at Uvalde with a cloudstreet that bisected the turn area. Everyone lined up on the street and flew it in and out. Nothing like 45 gliders at cloudbase at 110 knots flying out and back on one street. This was pre-Flarm and I was afraid to pull up because of the loss of forward visibility. The midair at Uvalde was event that really made most tasking committees realize that nearly 180 degree (0 degree) turns must be avoided.