Flatland Cross Country from the Winch



Based on DHV Info 122, Dietrich Muenchmeyer

Ideal wind conditions for good XC in flatlands is 20 km/h.  Which can give one a 40km/h average.

With a winch launch one got maybe 2-3 minutes to find a thermal.
Important to communicate between the pilots to establish the trigger points to get away.
Even with weak wind do not fly wind upwards to find a thermal after releasing.
If you feel a thermal during tow, release and take it.

Any change in contour can be a thermal trigger for a winch site. Some trees, a hangar, ...
As long as you do not sink, stay in it. Do not leave a weak, zero lift thermal low to find something better.

The fields around your launch site, along with the vegetation and the season can differ the thermal triggering.
Young green Corn and raps , green, do not generate thermals.
While when they are ripe they become ideal thermal creators.

Mealie maize grows slow in dry soil, good thermal creator, while once ripe, not so good anymore.

Stay in your first thermal until cloudbase ( or ceiling )
Even when you think the thermal is weakening or stops and you are not on top yet. Hang around until it picks up.

If you fall out of the thermal, loose it, immediately initiate a tight 270 degree turn.

Once you got away and going XC

In sink the glide ratio goes down to 3-4.
Priority 1
what do you know about the terrain. Where are the hills, wet areas, dry spots, groundwater level,..
From high up everything looks flat.
And  warmed up air still flows uphill. Thermals will release at the windward , luv side, in the upper area of hills.
Or on the sunny side of a hill, but not necessary. And since you do not see from high up the contours, study the maps upfront.
Priority 2
Observe the clouds. Once you are halfway up to cloudbase, use the clouds as the only factor.
Approach the clouds on the luv side, taking into account the thermal drift due to the wind.
Best climb can be expected somehow luv sided from the cloud center.

With any little bit of wind there is one golden rule to find the next thermal. And that is with the wind, downwind.
At cloudbase decide where the next thermal has to be and go straight for it. Once the vario beeps, turn immediately.
One can always center the thermal better. If you missed it, turn back only if there was really lift.
Sometime you got clouds which  are off the straight downwind path and look much closer, compared to clouds straight downwind.
Ignore them, the chances are less to reach them.

On blue thermal days one can also determine in the inversion layer where the thermals are.

Priority 3
Never give up. If you are low and got a safe landing, keep on searching and look for a thermal.
But often the thermals trigger at the edge of a forest. Take the thermal and drift over the forest low?
Or bail out and land safe? That depends on how you have been flying for the day. If you have been in topform, use it.
If you anyway stuffed up a few times before, leave it..

More on XC and winching , have a look at  Winch Tips    http://stpxml.sourceforge.net/skygod/Airmanship/winchtips.html