Zen and the Art of Circles (copied from http://www.xcmag.com/articles/133/)

I copied this from http://www.xcmag.com/articles/133/ so that our site can index/search on the contents. I didn't write it and this is just the text (not the nice pictures)

My own initiation in to the black art of thermalling began on my tenth flight. Stood on a take-off in France, my mentor Keith gave me a thorough briefing. “When your vario starts beeping, count to four and crank on one brake.” Armed with this precious jewel I launched into the midday thermals and was blasted upward in a straight line counting slowly in my head. On four I choose my direction and cranked as hard as I could. By my fourth attempt that day I knew I was doing something wrong. Surely someone would’ve mentioned all the G force? There was something going on here that I couldn’t quite put my finger on. Something subtler than I’d first imagined thermalling would involve. Twenty spiral dives later I was back on the ground feeling both frustrated and a little sick, but ready for Keith’s next priceless gem. “I think you might be flying a little too fast. Try more outside brake.”
Just as the Hitchhiker’s Guide to the Galaxy manages to so astutely and succinctly summarise the entire population of planet Earth as ‘mostly harmless’, Keith’s few words to me all those years ago actually did capture the essence of thermalling in its most elemental form; turn in circles to stay in the lift, and fly slowly to stay in it as long as possible. The next day I did slow spirals instead when the vario sang and managed twenty-five kilometres in two hours. It was amazing, I was hooked, but I could tell that there was more to this than Keith was letting on. I set about gathering information through both my own experience and the wise words of others. What I discovered though, was not a hard and fast set of guidelines to follow, but a mish mash of opinions and rules that sometimes even contravene themselves. How to thermal is such a vast subject with very few true rules that can actually be rigidly applied. So instead over the next two issues we’ve brought together the words and advice from some of the best pilots in the world in an attempt to convey the finer details of the Zen of circles.
Before you look at how best to use a thermal you first have to find one. Thermals are invisible, so finding them is normally a process of stacking the odds in your favour. I teach pilots the ‘Five Star’ assessment system to help them increase the odds of finding a thermal. It’s a simple system that awards a rating to the place you are considering going to look for a thermal, based on how many of the following clues you can see there: sunshine, wind, landscape, cloud, birds or gliders. Let’s look more closely at each clue to understand them.

THE SUN
It’s our fuel. Without it there is no radiation, no heating and no thermals. If you are flying on a day with clouds and shadows, the ground will be being heated in the areas of sunshine and not in the areas of shade. Although shadows can trigger warm air to leave the ground as they pass overhead, as a general rule the shade is a pretty poor place to be for any soaring aircraft or bird. Ex-double world champion, Rob Whittall, once told me when I pressed him for his single most important piece of advice, “If you stay in the sunshine you’ll not go far wrong.” Award your potential thermal source one star if it’s basking in sunshine.

WIND
Not only does it create dynamic lift on hillsides, which prolongs your flight and radically increase your chances of catching a climb, it also blows the thermals along the ground and up the hillside to the top where they trigger. In proper mountain systems that are subject to valley winds and anabatic flows you should always remember that it’s these lower winds that bring the warmed air from the valley up on to the mountains, the meteo wind is often of little real importance until you are high up. You should study the shape of the valley below and imagine a huge river is washing up the valley. The places where your river would collide with the landscape and be forced upwards are always good places to look for thermals.
In the flatlands things work a little differently. The wind blows the warmed air along the ground until it reaches a trigger point like a river, a line of trees, a road or simply an undulation in the landscape where the thermal releases and begins to climb. Remember warm air is buoyant and will never go down hill, if the landscape dips, the thermal releases. Loitering slightly downwind of the trigger line is a very good trick for flatland flying. If the place you want to go next has sun and wind then you are looking at a two star location. Worth a go if there’s nowhere else better within reach, but it’s still not a dead cert.

LANDSCAPE
Neither the sun nor the wind will produce any lift without a landscape to interact with. In the flatlands the landscape’s ability to absorb the sun’s warmth is crucial to thermal generation. Dark-coloured things heat up better than light-coloured things. Wear a black T-shirt on a sunny day for ten minutes and then change in to a white one and you’ll immediately feel the difference. A dark area on the landscape, like an area of freshly ploughed fields surrounded by green pastures, will heat up much quicker than the fields around it. But it’s not just colour that’s important, texture and aspect also play their role too. Bubbles of air move easily over or away from a smooth surface whereas a rough surface, like the stubble in a field of a recently cut crop, can have a Velcro-like effect on the warmed air. Although it takes longer to heat up it will hold on to the heat longer than a smooth surface, which releases quickly and often, therefore it often produces a hotter bubble of air. In Piedrahita in central Spain you can often experience this; hunting around on the dark rocky places produces nothing whilst often a dive out into the light gold fields of the plains sees you booming to cloudbase.
In the mountains the colour and texture of the landscape is far less important than its aspect to the sun. If a hillside is facing directly in to the sun it absorbs maximum radiation and produces good thermals. The most reliable XC routes, or the big lines, stay in the strongest sunshine all day. They begin on east faces and move around to south faces for the early afternoon and then use west faces toward the end of the day. Taking yourself to a west face early on is often a recipe for an early bath, as is trying to limp home in the evenings along east faces.
Be you in the flats or deep in the mountains, if the landscape ahead is favourable for thermals then add another star. A dark rocky hillside that is facing bang into the sun and the wind is a three star choice and unless you have another stunning option within reach you’d be rash to turn away from it.

CLOUDS
A cumulus cloud is just the part of the thermal you can see. If there’s a cumulus cloud there, then there’s a thermal there, because cumulus clouds are only formed by rising air. This is one of the most difficult rules of XC flying to follow, because often other clues conspire against you and lure you away. Cu’s might be forming in odd places away from where you normally expect to see them or you might come across a cu in the middle of the valley with no apparent reason to be there. It doesn’t matter if it’s defying all your local knowledge and everything you’ve ever learnt. It doesn’t matter if you haven’t the faintest idea what’s causing it and why it’s there. Cumulus clouds are only formed by rising air. If there’s a cu there, you can climb there. I’ve often forced myself to turn away from my planned route, or I’ve dived low into what appears to be a stupid place according to all the other rules, because a cu has started building nearby and shows me where the air is definitely rising. Equally, I have landed confused as to why the really obvious sunny ridge didn’t work only to realise I’ve ignored an unexplainable line of Cu that was actually in easy reach. This is the one rule of XC flying that you should follow religiously. Plugging on with your flight plan into a cloudless area on a day where cu is forming elsewhere is folly, and will almost always put you on the ground or get you stuck. If your next destination has sun, wind, a good landscape and a cloud it’s a four star choice and you are just about guaranteed a climb.

BIRDS AND GLIDERS
If you’re confronted with a four star location there is only one thing that can possibly give more confirmation of the presence of a thermal and that’s the sight of someone or something climbing in it. Five stars means that the thermal is definitely there and good enough for you to climb in. Only ever ignore a five star location if you can see another high-ranking location within reach further along your course.

zen-pt1-column-thermal.jpg

Looking down the barrel of a column thermal during the PWC Final, Portugal, 2005. Photo: Martin Scheel

The Five Star system is a fairly accurate method of deciding the potential of your next location. However, flying is a very fluid art. The sky is continually changing and developing and a good XC pilot is continually assessing what they see and updating their mental picture of the sky ahead. I asked one of Britain’s best pilots, Adrian Thomas, for his guidelines on thermal detection. Living in the plains of central England Adrian does a lot of flatland flying and gave me a fascinating insight into his thermal detection process and what’s going through his head on a good XC day.
“Firstly it’s really important to be able to picture the shape of a thermal. Thermals all leave the ground with a mushroom shaped vortex head that climbs upwards dragging a tail with it. The tail remains attached to the ground as long as there is warm air to feed it and then breaks away and accelerates towards the head. The fastest climb rates are in the accelerating tail, which is why you can sometimes climb quickly up to pilots who were way above you only minutes before. But you’ve got to fly very well to stay in it or the tail will accelerate past you and you’ll be left in the sink below.
“At altitude I use clouds to find thermals. On transitions I stare very hard at the clouds looking for places where wispy tendrils are forming at cloudbase and being sucked in. Tendrils alone are no good (they might just be the remnants of evaporating cloud) it’s the upward motion that matters.

zen-pt1-wisps.jpg

Wisps of cloud climb upwards indicating the presence of a thermal. Photo: Adrian Thomas

“At mid-level, halfway between the clouds and the ground, I route my track between ground sources and clouds, and detect thermals by feeling the turbulence and drift patterns. zen-pt-1-thermal.jpgI picture thermals as rising bubbles of air with a doughnut-shaped leading vortex at the top, and a long tail dragged along behind (see picture). Usually we don’t encounter the doughnut bit unless we hit the very top of the thermal (if there is a cloud that is where the doughnut vortex is). Instead we encounter the long tail. “In the tail the air is being dragged into the rising column-thermal. That means that there is a drift towards the thermal core, and at the same time the updraft is generally increasing in strength towards the core. That means that generally the wing nearest the core will be in more upwards-moving air than the wing further from the core. That differential up draft will cause the wing to roll and yaw away from the core, yet at the same time it drifts towards it. To detect thermals at mid level it is essential to be very, very aware of your drift and of the roll and yaw effects the air’s having on the wing. Fight the roll and yaw inputs, but go with the drift. Use the controls to keep flying straight and the inflow will drag you towards the core. Remember the rule: ‘roll right, yaw right, drift left,core is to your left’.

zen-pt1-ripples.jpg

“This all refers to perfect flows, but thermals are turbulent beasts with sink and lift combined in the flow around them. In general, at mid-level, in my experience, the turbulence feels as if it spreads out from the core like ripples on a pond (see picture 2). These ripple-like disturbances can provide information about where the thermal is - if you hit the ‘ripples’ at an angle then they affect one side of the wing first. Turning towards that side will take you towards the core of the thermal. Finding thermals through patterns of turbulence is difficult and something that only comes with practice and a good mental image of thermal shaping. However, once you crack it you will open a new door in your flying and your thermalling will go up a level.
“When I’m at low levels I take my track over ground features. I still pay attention to the positions of the clouds and aim to position myself simultaneously over a ground-trigger and below the good bit of a working cloud. The lower I am the more attention I pay to ground features like hills, sun, fields, differences in surface texture and moving things like cars or livestock that might trigger the hot air next to the ground. It’s when you’re low that you’re most likely to encounter the mushroom shaped dome of an emerging thermal rather than its twisting tail. If you do you’ll experience a different set of feelings from the air.
“Imagine a balloon rising up and hitting you from underneath. You’d feel a sudden lift as it hits you but then you’d slide sideways off the top of the balloon’s dome.
“The drift can be very strong while the roll and yaw inputs might be relatively weak. It feels like you have been grabbed by a giant hand and dragged off to one side. If you get the combination of roll, yaw and drift all going in the same direction then you are above the head of the thermal and you need to fight the roll, yaw and drift and turn in towards them to find the core. The core will be difficult to centre, and you will climb at a lower rate than usual - at the actual rate of ascent of the thermal as a whole, rather than that of the tail rising up into the climb. Still, you are in the climb at its beginning, so you can expect to go as high as the climb goes as it is unlikely to fall apart on you. When you hit the top of a thermal the rule is different from when you hit the tail; instead it’s ‘roll right, yaw right, but drift right, the core is to your left.’
Finding thermals is one of the greatest skills you will develop as a pilot and one that is worth spending a lot of time perfecting. Ex-world record holder Godfrey Wenness passed on this great training technique he uses to help pilots familiarise themselves to those exact sensations that Adrian has been describing.
“When I first started flying I used to practice climbing in a house thermal for a few hundred metres then flying out and away for 5-10 seconds. Then I’d turn back and find it again paying attention to the way the glider behaved as I neared the thermal. Feel for the pitch, yaw and roll and notice how they change when you approach from different angles, heights and wind directions. Doing this over and over again will teach you what you feel when you are close to a thermal, how to enter it and which way best to turn to stay in.”
Airwave’s designer, three times UK champion and current European vice champion, Bruce Goldsmith added further to this when he told me, “Be aware of subtle changes in your airspeed and ground speed so that you can feel your groundspeed pick up if you start to get sucked towards a thermal.” Bruce’s fellow team mate and double UK champion, Russell Ogden, compounds the theory. “Let the glider follow its own path and go with the flow rather than forcing the glider to fly a straight path.”
Thermal detection is a Zen-like art that brings together all your senses with your understanding of fluid dynamics and meteorology. Understanding how the sun, air and landscape interact to create lift is only half the story, awareness of all aspects of your glider’s movement and position in the air, both vertically and horizontally, is also crucial to build the mental picture we need to visualise the air around us. Our instrumentation should merely confirm what our senses are telling us.

It’s one of the most sensorially exciting moments in any pilot’s life. I doubt if anyone who’s experienced it could ever forget it. Your heart pounds, your palms sweat and your mouth goes dry. The brake lines snap tight and the force of your quarry is enough to throw you violently to one side. It’s as though you’ve just hooked your first big game fish and it’s now wriggling and thrashing at the end of the line. Except this isn’t ’Fishing Weekly’ you’re reading and what I’m talking about is no living animal. You’ve got your first proper thermal, hook, line and sinker; all you’ve got to do now is make sure it doesn’t get away.
The ensuing seconds are both intoxicating and rife with decision: left or right, crank it hard, gently drift in or do you just straight line it in even deeper? To give yourself the best chance of getting it right you need to have a good idea of the shape, size and make-up of a thermal. Where are the strongest bits, the weak bits and the edges?

Thermals are rarely made up of equal lift. The ground which created the thermal would have been warmer and colder in different places and so a thermal will have hot spots and cool spots. Hot spots rise faster than the cooler spots and form cores. The fastest way to climb in a thermal is to constantly stay in the hottest part of the airmass as it rises the quickest. In a windless environment, cores will normally be drawn in to the centre of the thermal (diagram 1),

Diagram 1

However, in reality we are rarely ever in a windless environment. Inevitably there will be a valley wind or the true meteo wind blowing on and affecting the structure of the thermal and so the cores won’t necessarily be in the centre of the climb. Instead, the wind will shape the thermal into a teardrop shape. As the strongest lift is climbing faster it has more vertical velocity than the weaker lift and so is less affected by the wind. The weaker lift is more easily affected by the horizontal wind and gets blown downwind (diagram 2), leaving the strongest lift upwind. This is one reason why good pilots search for strong climbs a long way out from the hill on windy days. In addition, Diagram 2because the thermal actually has a mass of its own, the meteo wind rides up the front face of it as if it was a hillside and creates dynamic lift. This is why we can sometimes soar up the sides of cumulus clouds and why pileus caps form on the tops of clouds where the wind accelerates over them (diagram 3).

But before you can worry about finding the core of the thermal, you need to fly deep enough into it to zen-pt2-diag3.jpgbe able to turn a 360 without falling back out. To do this many pilots employ the ’count of four rule’. Once you hit a thermal you fly straight on into it counting, “One banana, two banana, three banana, four!” If you’re still inside the thermal by the time the fourth banana comes along, then it should be big enough to climb in.

But which way are you going to turn first? Gliders react differently as they enter thermals depending on which angle they enter the thermal from. On first encounter you can’t be sure exactly where the thermal is in relation to you or what shape it is. So it’s best to follow some basic guidelines.

First and foremost you should try to establish a 360 pattern, unless you are very low and trapped against the landscape in a strong wind, rather than flying in figure-of-eights as soon as you hit a thermal. The reason why birds wheel effortlessly in circles above your head on a sunny day is because this is the most efficient way to fly and the best way to keep track of a thermal. British champion and Ozone test pilot, Russell Ogden, told me,
“If I feel a strong pull to one side then it’s obvious which way to turn, but if I’m unsure and feel that I could go either way I’ll turn one way for a couple of seconds then turn back the opposite way, just as I would if I drove onto a roundabout. Now I am in the right position to fly around the centre of the thermal without falling into the sink around it.”

If you’ve hit the thermal whilst soaring along a hillside you will also have to think about keeping yourself safe in relation to the landscape. Turn out from the hillside and fly far enough away so you can throw in your first 360 without hitting it. That first turn is usually the worst as you haven’t established an angle of bank yet and the glider will often pendulum behind you after the first 180 degrees and want to sit back with little energy for the turn. Quickly whipping the brakes up to pitch the glider back in front of you may feel unnatural as the scenery rushes towards you, but it will put energy back in to the glider and give it the speed to carry on turning. Once you’ve made the first 360 the glider should settle down into a more regular pattern and the scenery won’t seem to rush at you so quickly every time you turn to face it.

Once you’ve managed to complete three 360s in a row in constant lift with the vario singing all the way around it’s time to start exploring and looking for the strongest lift. If you don’t suspect there to be much wind then a simple search pattern will work. As you hit stronger bits of lift on your way around the circle straighten up slightly and push deeper that way for a moment before turning inwards again. Each time you do that you should be moving closer towards the core (diagram 4).zen-pt2-diag4.jpg

Ex world record holder, Godfrey Wennes, told me, “We teach our students to ’follow the sound’ of the vario to chase the thermal.
“Fly to make and keep the sound at a peak. Fly straight as the sound gets louder and turn if it starts dropping. Learn the tones and set acoustic delays to anticipate the top of the core (peak sound). In most cases of strong lift / cores you need to turn before the peak evens out otherwise you fall out the other side and need to do an inefficient hook turn to get in again. The pendulum swing of a paraglider can also play havoc with the sounds - be aware that a sudden sharper turn will increase tone for a moment as you wing over higher thus giving the impression you have hit the core.”
Godfrey cautions, “The inexperienced will fall for that trap every time while the steady turner will out climb him.”
If there’s any wind about you need to find the upwind / leading edge of the thermal so you can locate the strongest lift by finding the core and the dynamic lift of the wind blowing up the front of the thermal. You should be able to see the glider slow down in relation to the landscape each time you face into the wind. If you straighten up for a moment, each time you face the wind you will slowly edge your way towards the upwind / leading edge of the thermal, and the best lift. On reaching the upwind side of the thermal you might feel an increase in lift as you encounter the dynamic lift where the wind is being forced up the side of the thermal, but then, if you fly too far, you’ll fall out into the sink. Falling out of the upwind side of the thermal is never as bad as falling out of the downwind side but if you do then quickly turn the glider around and fly back downwind, through the dynamic lift and back into the strongest lift. In comparison falling out of the back of the thermal is much worse. Then you’ll fall into heavy sink and have to turn back into wind and fly slowly back through the sink only to get into the weakest lift. Whenever you see someone fall out of your thermal and appear to free fall away, you usually find that they have fallen out of the downwind side of the climb.

What are the actual mechanics of what we are trying to do? What’s the best way to control your glider and get the most from it as you search? Hugh Miller, ex British champion and winner of the 1997 World Air Games, offers this advice:
“Damp out the surges with the outside brake. Try and keep the glider calm and settled above you Keep the roll rate as constant as possible with weightshift controlling the glider’s dives with sharp stabs on the outside brake, holding where needed, always looking and leaning into the circle. Don’t let the thermal bully you. Fly actively.”

Russell Ogden says, “You need to be able to crank it tightly or switch effortlessly into a smooth languid turn. A common mistake pilots make is that they don’t turn tight enough in thermals. You need confidence in your skills to be able to bank the wing up and force it into a tighter circle once you have located the core and this can be hard as the air in the core might well be turbulent. It is important to know your wing and be able to use the pitch and energy to get the roll right without spinning.

zen-pt2-photo1.jpg

“If I want to straighten a little during the 360, I keep on the weightshift but use a touch of outside brake. This changes your direction without upsetting the wing too much. When I’m ready to continue the 360 I release the outside and resume with the inside. That way you do not create too much unnecessary roll and are always ready to tighten because your weightshift is there already.”
Russell adds, “The more aggressive the thermal is with me, the more aggressively I fly. The gentler the thermal the smoother I fly, holding the brake handle as though it were a fragile glass of wine that I mustn’t break or spill.”
Using the outside brake to vary your turn radius, you can start to explore the thermal, and exploration is everything. Triple British vice champion, Innes Powell, once told me,
“If you do two 360s the same you’ve let yourself down. You’ve missed an opportunity to gather more information about the thermal.”
The current female world champion, Louise Crandal points out that you need to open your mind to all the information that’s available:
“It’s important to be aware of any changes in the air. When you see a sign of better lift elsewhere react to it and change pattern to take you there.
“While I’m thermalling I give all my attention to smell, temperature, change of wind direction and of course, all the information I get from the glider and vario. I change turn direction whenever it makes sense to and I move around the sky in a constant search for better lift. It sounds exhausting but it’s not. Vultures sleep while they thermal and we can do the same. Once it becomes our flying style it’s just like riding a bicycle, but much more fun.”

Louise, who has her own trained Steppe Eagle that flies with her, knows exactly how much we can learn from birds.
“Follow the birds. They’re the masters of the sky, so do what they do. It’s as simple as that! I had to stop thinking in the usual patterns I had trained myself to use over the years and just follow. Suddenly I was thermalling better than ever before. I realized that birds don’t fly in circles. They turn in thermals but never in neat 360s. Every single lap is different and they constantly adjust and move to where the thermal is stronger or even move a couple of hundred metres to the side to find better lift.

“Whenever you get the chance to fly with a bird try to follow it as closely as possible. Depending on what kind of bird you meet it might try to get away from you, but even if it chooses to leave the thermal, if you have the height it’s worth following it. Soaring birds automatically stay in lift for as long as possible, even with an annoying paragliding pilot on their tail, so there’s always something to learn.”

zen-pt2-photo2.jpg

Indeed, good pilots always want more from the thermal so they explore all the time. They often don’t turn very tightly in cores because they are wandering about the gaggle picking off the best bits of lift. They do this by staying alert to all the information they can get. If they see a glider or a bird rising faster than they are, they fly straight over them and profit from the better lift. Sharing a thermal requires an acceptance on the part of all the participants that their ability to roam wherever they like in a thermal has been compromised. However, the additional information all the other pilots floating around you in the gaggle can give is immeasurable.

Thermalling is all about mental mapping, staying alert to new information, deciphering the feedback your glider gives you and exploration within the thermal. Mastering it requires you to have a good mental image of the air and then lots and lots practice to familiarize yourself with the sensations the glider and the thermal give you.

TIP: HOW TO JOIN A BUSY THERMAL
Joining a busy thermal is like jumping onto a playground roundabout. If you try and jump straight in the middle, or worse still, against the flow, you’ll cause carnage. Instead, run along on the outside of the roundabout until you find a slot or get offered one by someone, then slot quietly into place.