by Gordon Buckland. (Reproduced with permission from Model Aviation Mag.)
As I participate in many Soaring contests throughout the US, I can’t help noticing that many serious Thermal Duration (TD) pilots still fail to complete their allotted task time in air that is actually Sailplane friendly.
What is it that makes their Sailplanes founder and sink, while many other Sailplanes are riding high? Why do many Soaring pilots regularly miss the thermal boat?
There are various reasons, but a basic prerequisite to keeping the model aloft for the required duration is that the pilot must choose to fly in buoyant or rising air. Even if lift is not obvious, the pilot must avoid flying his aircraft in sinking air if there is to be a chance of completing the max. When a pilot launches a Sailplane, he or she makes a choice about where to go (and with open winch contests, when to go). This choice will ultimately determine whether the aircraft ends up on the ground early or whether the pilot will be setting up for the landing task at the business end of a 10-minute max. It’s rare that all the air is going up, so to succeed in achieving every max, the first step is to know where to go before you launch.
As a budding Thermal Duration pilot, I made it my business to find the answers and develop my sixth sense—my thermal sense! To succeed at this game you must use all of the senses you were blessed with. If you have the basic five that God gave most of us and they are in reasonable repair, with some practice you are in good shape to develop your thermal sense.
Let’s look at how we can make best use of each of those five senses we were born with.
Don’t depend on poaching from birds and other gliders already in lift. Your eyes can tell you much more. Practice “seeing” thermals by always watching the air whether you are flying or not. Become aware of what the air is doing at all times. It doesn’t matter whether you are at work or play, in another country or at home, driving your car or sitting in the park with your dog. If you become disciplined about watching the air and become aware of lift as it passes by, it will become second nature to steer your Sailplane into lift when you actually fly.
The things you can look for in the air are the less-obvious objects going up or suspended, such as bugs, spiders, seedpods, birds, dust, or anything else heavier than air. Watch what the wind is doing to ground-based objects, particularly how it is affecting long grass, trees and flags, bunting, streamers, etc. Knowing the state of the wind at all times is one big step toward understanding where the lift is exactly. Having a transmitter-mounted streamer to indicate accurate wind direction can be a huge advantage.
The best advice I ever received regarding this was from Gordy Stahl, who encouraged me to obtain a pair of dedicated prescription sunglasses for flying. Oh what a difference that made! I got a long-distance prescription at the Walmart optometrist for $60, and a pair of 50% amber-tinted, aviator-style prescription sunglasses from an online company called Zenni Optical for $56. For less than $120 I could now see better than ever. The extra confidence gained from being able to see your model well at a distance is a phenomenal advantage. With a good set of prescription glasses you can see many other things you never even saw before such as small birds high or a long way off, or seedpods and spiders on the end of webs being carried skyward by the very forces you are seeking. Your newfound ability to observe the direction of movement of distant trees and tall grass upwind of your position also allows you to predict the arrival of lift.
Another side to seeing lift is watching your own model intently once you are in the air. Your Sailplane is easily your best indicator, but you must know what you are looking for. If you are passing nearby lift it will often steer or yaw your model away from the thermal. The inflow of air toward the thermal acts on your vertical fin and the result often steers your craft the wrong direction. If you are alert and watching for any such effect, you can counter this pull and turn toward the indicated lift. If you are doing a thermal search, you should learn to fly your model in a straight geographical line (toward a fixed point), crosswind at approximately 45°. Any deviation by your model is then apparent, possibly indicating the effect of adjacent thermals. Another technique to make better use of your eyes while you are searching is to keep your model’s fuselage visible from side-on as a means to allow you to see the effect of lift on its pitch axis.
In conjunction with watching the wind, you will be feeling it on your skin. Warming air is usually an indicator of lift forming overhead or somewhat upwind. This increase in temperature is often accompanied by a lull or decrease in the prevailing wind speed confirming lift building in an upwind direction. You can feel these subtle changes more easily on bare skin such as your neck and your feet. I’m sure many of you have observed Joe Wurts feeling the air by flying in shorts and no shoes! Cooling air, often in conjunction with increased wind velocity, is an indicator of lift having passed and now being somewhere downwind of you. Your sense of touch should be able to register the temperature of the air passing by you, its velocity, and direction. You are feeling for the thermal inflow or infill as nearby air rushes in to replace the thermal air which left skyward.
To effectively feel lift and know its location, you must be constantly thinking about the wind direction and speed so you are immediately aware of any change from the status quo. An increase in wind speed indicates a thermal has passed and will be downwind somewhere in the direction the wind is blowing. A decrease in wind speed indicates a thermal is rising somewhere upwind of where you are and will soon be upon you. A change in wind direction indicates that thermal activity is sucking or redirecting the air, where you are standing off its previous course and changing the winds direction where you are standing. The thermal is going to be somewhere on a vector toward this new wind direction. The strength of a wind shift to either side will have a bearing on the direction of the thermal causing the shift. Understanding the combination of wind-velocity change and wind-direction change gives you a compass directing you to the rising air.
The best way to visualize this compass is to use Joe Wurts’ “Third Vector” illustration. The blue vector represents what you normally feel as the prevailing wind direction and the length of the blue vector depicts the speed of the prevailing wind. The green vector is what you feel as the new wind direction and its length is the new speed. The thermal direction is then indicated as the yellow third vector. This concept can be visualized as you fly and you then have a compass always telling you which direction the ground signs are telling you to go.
The sound of the wind as it ebbs and flows also helps you to become aware of wind shifts. Learn to listen to what the wind sounds like as it blows past your ears or through nearby trees or grass and when the sound changes, look to see why. The other important benefit of your ears is that the wind can carry sounds from a great distance. Often the sound of an upwind highway, building site, or loud music becomes louder as the wind speed increases from the sound source’s direction. This can indicate that lift is on its way from the upwind direction.
Your ears have other secrets to reveal as well. How often have you heard the chirping of crickets and cicadas come and go on a hot summer day? Aren’t they often really loud for a short period and then their chirping wanes for a while? If you haven’t noticed before, you might discover that these insects are actually telling you something as they communicate with each other much more vigorously during a lift phase. If you are listening carefully and you hear them singing, then they are telling you their air is good for flying! I have to thank my flying partner, Jody Miller, for this wonderful piece of extra sensory information he passed on to me, which he learned as a FF US Junior representative.
Your nose is there whether you like it or not. Why not use it to sniff out some lift and maybe keep your Sailplane up a little longer? The smell of smoke from a fire upwind, or the smell of fertilizer being applied, can easily carry many miles. In Florida we often fly at a landfill site and when we are downwind of the active landfill, we can sometimes smell the odor of refuse, smoke, or the smell of dust as earthmoving equipment works on the site. When we can smell a strong odor from an upwind source, it generally indicates that the air between us and the source of the odor is not rising air. We can smell upwind odors because the air has descended (or at least not risen) on its travels to reach us. In this case, your odds of finding lift may be better to launch and go anywhere else except toward the source of the ground-hugging smell.
The reverse applies as well, so when the constant smell of an upwind site is suddenly missing, we know that good buoyant air is likely to be found upwind from us.
Can you taste lift? Maybe Joe Wurts can if anyone can. You sure will taste the sweetness of victory, though, if you can command the use of all your God-given sensory receptors when you fly in Thermal contests.
There is no mystery to consistently finding rising air. It just takes a simple understanding of your surroundings, your model, and diligent practice using each of your receptors to maintain a mental picture of what the air is doing at all times. Each time you launch your Sailplane, practice so you can make decisions based on the available information as to where the lift should be. You will quickly begin to sharpen your sensory skills. There is no doubt that your eyes are your most important lift receptor, so get that new amber sunglasses prescription and go out and begin to develop your thermal sense by processing the information collectively from all of your receptors (whether you are flying or not).
You can always be practicing the skills you need to stay up when you can decide where to go before you launch. Find that good air and enjoy your well-earned max or enjoy being the last to land in your man-on-man flight group!
Your thermal sense is waiting.
Fly downwind and soar!
League of Silent Flight