Imagine strong thermals rising through a strong wind. We have two types of current colliding at right angles, so there will be significant turbulence and thermals may not have consistent texture or shape. When wind distorts them a subtle variation of the uniform circle may help to maintain position within their cores. Flying a broad, flat turn on the windward side of each circle and a tight, steep turn on the lee side can offset that tendency to drift downwind from the best lift. This is essentially the same maneuver that power pilots refer to as ‘turns around a point’.
Even in the center of a large thermal, if you lose contact with the strongest lift you probably have been ejected by the turbulence of the core. (Or rather the air you’re rising in has been ejected.) When this happens it usually will push you out the downwind side as your thermal boils up through stronger horizontal winds at higher altitude. New lift rising from the same source will arrive upwind of the position to which you have drifted. So again, in the absence of any other indication and especially if a climb seems to have slowed with unexpected suddenness, moving upwind will often bring a climb back to life.
The upcoming week should bring some of our best thermal soaring of the whole season here at Crystal. It will also correspond to one more heat spell (whether that part’s welcome or not). If we see any cumulus, they’re apt to be very, very high – and marking only the strongest and highest lift…
Well the hottest days are behind us now, and some of our year’s sweetest days are coming next. Expect blue conditions this weekend, then as the new month comes on watch for beautiful clouds of all kinds to begin decorating the Mojave sky – it goes with the season. Meanwhile, thermal conditions will remain fine for several more weeks even as their strength and height decline with the sun.
SEE YOU SOON
The basis of good thermal technique is flying a round circle concentric with the area of lift. Most circles in lift should be banks of 30- to 40 degrees at the minimum sink speed for that bank. Speed control is fundamental to keeping circles truly round, and the key to that is holding constant attitude. The most common error in all aspects of soaring technique is moving the stick far too much while neglecting to use the rudder with necessary precision. Think critically about the way you handle your bird. It is not possible to maintain a constant attitude while jerking the stick. Instead, dance with your thermal, lightly holding the stick to steady the craft. Maintain attitude, direction and coordination within the lift by moving the stick as little possible and using light but aggressive pressures from both feet. (Modern sailplanes demand less rudder – but even less stick as well.)
Once a particular thermaling turn is chosen, use the position of your ship’s nose on the horizon to fix all three axes – roll, pitch and yaw – as solidly as possible. Concentrate your vision for several moments (not minutes!) at a time STRAIGHT AHEAD as you pan around the horizon. Frequent, quick control pressures are necessary to hold position firm against continuous changes in the airflow around you. When your bank is flattened by lift beneath the inboard wing, you can see it and instantly react with momentary aileron and rudder into the turn. As you skirt a thermal’s core you may see the yaw slowed or even stopped by stronger lift there, despite your continued bank. This calls for inside, or ‘bottom’ rudder to reinitiate the turn – followed by a moment of ‘top’ rudder to reset and stabilize attitude. When you fly out of stronger lift or bank too steeply the nose will drop, requiring back stick and/or top rudder to avoid gaining speed and moving out of position within the thermal. Or arcing into stronger lift, the nose may rise, demanding forward stick or bottom rudder (or both) to maintain speed and control effectiveness. Notice that, as with your car’s steering wheel, the more of any control you apply in one direction the more you might need the other way a moment later to reestablish balance.
Whenever you’re having difficulty in a thermal, maintaining the right attitude is a major part of the solution, and the key to that is looking STRAIGHT AHEAD, through the yaw string, to the HORIZON. After a full circle or two, look around for all kinds of information, such as traffic, clouds and their shadows, important terrain features, and drift in the wind. But then get your eyes back out front. If you consciously practice using the horizon directly ahead as your primary reference, awareness, response time and overall results are sure to improve.
Meanwhile, it is most important to remain steady. Make a point of sitting straight in the cockpit – not leaning to one side – with the yaw string directly in the middle of your field of view so you can look through it to the horizon and react instantly. The best results come only through a fluid economy of movement. Excessive misuse of aileron (and unwillingness to move their feet) causes many pilots to adverse yaw their way away from lift and down! Stop jerking the stick!
The yaw string should always be straight in level flight, and of course every turn should be coordinated, but in the ongoing battle to resist a thermal’s outward push and stay within its best lift, ATTITUDE trumps exact coordination. (We can forgive uncoordination for a moment if it helps hold your attitude and keeps you pointed into lift.)
You should understand that skidding is always bad, for multiple reasons. Most important, excess rudder can lead to a spin, but it also lowers the nose and increases speed, both counterproductive in a thermal. Slips are okay safety-wise, and sometimes even helpful, but sustained skids are always wrong. Be sure you know the difference and continually respond to what the yaw string tells you. This piece of yarn is the one instrument that always reads accurately. Spend more time looking through it, out to the non-virtual space beyond rather than into a panel of gizmos, and you’ll discover all kinds of cool, actual stuff!