Ezek a legjobb szakirodalmak a netről. Sokat kajtattam utánuk, míg megleltem őket. Talán egyszer fordításuk is lesz, de aki egy kicsit is tud angolul, az egy szótárral simán lefordítja. Csak jó segg kérdése. Mint a termikelés maga. Jó szórakozást!
Thermalling Technique by Will Gadd
My favorite part of flying is undoubtedly thermalling; in fact, thermalling may be my favorite thing to do in life. There’s nothing like hooking a sharp-edged, positive ripper of a thermal and riding it upward for a couple of miles. My least favorite part of flying is also thermalling; those days when everyone else goes up flying straight and you hit the deck like a dropped park bench–repeatedly. On those days you’re glad you landed alone so no one else can hear you scream. The following is my latest “thermalling system.” I hope it helps you develop yours.
A little more thermal theory is useful to understand how to fly them. I believe thermals close to the ground are often quite small and relatively violent. As they rise they tend to smooth out and expand. Pressure also tends to influence thermal formation; high-pressure days tend to produce smaller, sharp-edged, “punchy” thermals. Lower-pressure days can produce very strong thermals obviously, but they tend to have mellower edges and be larger in size.
The day’s lapse rate also influences thermal strength; a hot day with a very strong lapse rate will produce stronger thermals. Think of a very warm piece of air rising out of a collector on a day with a strong difference in air temperatures between the ground and say 5,000 feet above it. A thermal will rise quite quickly in this situation. An inversion is the opposite, and not surprisingly thermals usually stop or at least slow down at inversions.
The above factors (and hundreds more but this is a start) give each day its thermal “profile.” If you launch on a clear blue day (indicating high pressure) with a good lapse rate (you checked the day’s soundings), then you might expect sharp-edged, strong thermals. If, however, the sky is filled with soft cumulus and looks somewhat hazy due to moisture, then you might expect softer thermals. The first thermal of the day provides some good clues about what’s happening; if it rips you upward and all you have to do to stay in it all the way to base is turn a bit then you’re off to a good start. If it’s small and difficult to stay in then ends abruptly 1000 feet later and you can’t take it any higher, then you know the day will be more difficult. I take a mental note of three important characteristics with each thermal I use during the day. What is my average climb rate? Not the spikes, but the true climb rate as expressed by a 20-second average? How high do I get before it totally falls apart, and are there any altitudes that seem tricky to keep climbing through? And finally, what are the size and drift of the circles I’m making?
The climb rate tells you what to expect as the day progresses; climb rates tend to improve until late in the day, and thermal size also tends to increase as the day wears on (sink too unfortunately). If you’re getting solid 600fpm climbs, then it’s probably not worth stopping in 100fpm on a glide unless you’re low (anything going up when you’re low is great). The peak thermal altitude is also useful; if you are getting to 6,000 feet AGL consistently but a strong thermal suddenly “stops” at 4,000 AGL then you’ve probably lost it and should search for it. However, if the thermal stops at 5,800 feet then it’s most likely done and time to go on glide. Remember that the peak altitude of the thermals should increase as the day progresses. On good days in Texas it’s not uncommon to see thermals in the morning only reach 4000 AGL, then 6000 AGL at noon, 10,000 at 2:00 p.m. and 14,000 at 5:00 p.m. This progression is generally less in the mountains but still observable.
Finally, the size and drift of your circles at various altitudes also tells you what to expect on the next climb and information on wind speeds aloft. This tells you what angle your thermal will be flowing from a collector so you can intersect that line I (note-very strong thermals will have no problem pushing the wind around them like a bridge abutment in the river).
Coordinated Circles, not Swings
OK, so you’re flying along and your vario starts beeping with the good noises. What to do? First, did your glider surge forward or fall back behind you just before the beeps? If it went behind you then you’re probably dealing with a “gust.” Wait and see if the beeping continues or goes back to sink. If it’s a thermal and the beeping increases, turn. I don’t worry too much about which direction; if one side of the glider is noticeably more pressurized or higher above you, then lean meaningfully in that direction and pull on the brake smoothly. How much pull ? Higher pressures in your glider indicate a stronger thermal, meaning you can pull harder you can. However, the most common mistake in thermalling is to pull too aggressively on the inside brake. When you pull too hard on the inside brake your body tends to swing to the outside of your turn in a small wing-over. Then your body swings back under the glider, you lose the turn and fly straight out of the thermal. Many pilots then crank another wild-ass turn to try and get back into the thermal; I flew this way for about five years before getting it figured out. What you want to do is fly in a “coordinated” banked turn. This is like riding a bicycle; you and the bike are at the correct bank angle for your speed and the sharpness of the turn. One of the most common problems pilots have is maintaining a consistent circle while thermalling; I expect you know what I mean… The correct technique is to start a turn with a smooth, controlled lean and simultaneous progressive inside brake application. The glider will bank up, your body will follow it, and due to centrifugal force you will continue to stay outside the glider’s circle and smoothly ride the thermal up. Jerking the brake instead of applying smooth increasing pressure will just swing you to the outside of the glider–then you’ll swing back under it, repeat. The glider will also remain over your head in a true coordinated turn; if it falls behind you, reduce brake. If it threatens to surge in front of you, apply a quick correction while maintaining your lean and turn.
If you can’t figure out what I mean, pull on one brake sharply and release it; you’ll swing out from your glider then back under it, usually with an oscillation or two as a bonus. Then try leaning hard for a second or two then go back to neutral lean; you’ll swing out to the side of your glider then back under it, but not as much. Now smoothly lean, pull gently and progressively on the brake and hold it; you’ll enter a gentle spiral dive or circle, same thing. This is what you want.
Airspeed and bank angle are directly related; the higher the bank angle, the more airspeed you need to keep the turn coordinated (think of a spiral dive). The lower the bank angle, the less airspeed you’ll feel on your face. Thermals are seldom perfectly consistent; this means you will have to continually adjust your brake and lean to maintain a coordinated turn. If your airspeed starts decreasing and the glider levels out, lean a little more, let up on the outside brake a little bit, and increase your airspeed and bank angle. If your air speed increases suddenly, lean a little less, pull a bit more on the outside brake, and maintain your bank angle. If you can learn how to thermal in a coordinated bank then you are well on your way to thermalling efficiently.
Centering: The mental map
OK, so your vario is beeping like mad; how long do you wait before turning? If the day’s thermals are small and you’re low, start turning immediately after you’re sure you’ve hit something (not just a gust). Rules of thumb about waiting two seconds etc. are meaningless in my experience. You’ve found lift, initiate a smooth banked turn and see what happens. If you climb really well for a quarter circle and then start sinking, open your circle up a little bit in the direction you found the best lift then tighten as the lift increases; notice the pressure in your wing and how your butt feels in the seat, not just the vario beeping, these are critical clues. Listen to the noise in your ears as well; with practice, you can actually hear the different air flows as you fly through lift or sink; if you can’t hear the air then get a new helmet. At some point in your circle everything will add up to the best lift as defined by your vario, wing pressure and lift under your butt. If you’re flying a coordinated 360 then it’s relatively easy to develop a mental map of where the best lift is in each 360; don’t worry about the ground, but where you encounter the best lift within each circle. Try to develop a “mental map” of what’s happening in each 360.
To fly toward better lift, maintain a coordinated turn, just reduce the bank slightly as you come back around the 360 and move the center of your circle over a little bit toward where you got the best lift. NEVER STOP CIRCLING. Once in the best lift, tighten the circle up slightly while maintaining a coordinated turn. Perhaps you get solid lift for half the turn, general sink for half the turn. Move the circle in the direction of the best lift again. Now you get solid lift for three quarters of the turn and less lift for one quarter. Move it again. Now you’re climbing solidly for the full revolution of your turn at +400 fpm average, but one portion of your circle is going up at +600 and another at only +200. If you weren’t in a coordinated turn, and most pilots aren’t, this would probably be due to the oscillations inherent in thermalling in an uncoordinated turn and you would not have a clue what’s actually going on. But you know to thermal in a coordinated manner, so you move your circle toward the +600 and eventually lock in a perfect 1000fpm climb all the way to base. Irregular thermals may give irregular “instantaneous” readings on your vario, so focus on getting the best average climb rate that you can. Hang gliders and sailplanes can use all kinds of funky ovals and figure-eights to get better average climbs, but I have found paragliders climb best flying coordinated, continuously adjusted circles (or straight if the thermal is big enough!).
Circle Size and Bank Angle
I find I thermal with 30-45 or more degrees of bank on days with small, strong thermals, 15 to 30 on lower pressure days and almost flat on days with light, wide thermals. The extremes of bank angles come in dust devils (almost vertical) versus flying straight and flat while climbing like mad under a big cloud; somewhere between these two extremes is the correct angle for your thermal on that day. Every glider responds differently to brake force and the amount of lean; what works for one pilot on his glider usually has little to nothing to do with yours. However, every glider will circle in a coordinated manner, and the feeling is unmistakable once you get it.
Here are a few scenarios to help pick bank angles for thermalling. Say you’re flying along in -600 fpm and suddenly you’re screaming up at +800. You turn, then go down at -400,so you move your circle toward the +800 but can’t lock it in despite continually re-centering your circle. You probably need a higher bank angle and smaller circle. If you’re very low in a small thermal, you may only be able to get half a turn in. Do your best to just improve how much of each circle you spend in lift, you’ll lock it eventually as you climb. Another scenario: you’re flying along in -600 when your sink rate starts to decrease smoothly to zero sink, then +200, then +300. I would keep flying straight until the lift starts to decrease, then initiate a relatively gentle bank and center on the best average climb rate. A relatively gradual, consistent rise in your climb rate is a sign of a large thermal. Often you can find very strong cores in large thermals that will offer much higher rates of climb, but in general the larger the thermal, the less bank angle the better to maximize your climb rate. Some bank angle is usually good; a glider won’t turn in a coordinated circle without it, but you can fly in a coordinated turn with equal brake using lean; watch a good pilot fly and you can tell he or she is often controlling the glider primarily with lean and modest adjustments to the outside brake.
There is no correct number of pounds to pull on your brakes while thermalling or distance to pull them down (1/4 brake is meaningless across a range of gliders), but there is a correct amount of brake to pull and lean to maintain a coordinated turn. It’s like riding a bike; no one can tell you how to do it, but you stay upright when it works. I generally thermal with roughly twice the amount of brake pressure on the inside brake than the outside, and adjust my turn primarily with lean and the outside brake. You will probably do it differently, but know a good coordinated turn when you hit one.
Don’t change directions when thermalling, especially when low. There are three good reasons for this; First, changing directions messes your coordinated turn up and you have to fly straight for some time between turns which usually takes you away from the lift (all directions but one lead away from the lift…). Second, you lose your mental “map” of where the best part of your circle was. Third, the direction change will cause your vario to beep in all kinds of interesting but non-helpful ways. It is almost always better to simply move your circle over toward the better lift than try to switch directions and fly toward it.
If you’re having a hard time maintaining a coordinated turn, try flying a bit faster; use more lean and less inside and outside brake. Many pilots try to fly a perfectly flat circle; in truly massive lift this works well, and your glider may have its best sink rate with a fair amount of brake on. However, I find flying a bit faster with a mild bank often enables me to lock in the thermal’s best lift. Don’t confuse what works well while ridge soaring with what works best thermalling, it’s a very different game.
What do to do when you lose the lift
First, know if you’re at the top of the thermal or not. If every thermal so far has ended at 6,000 AGL and you’re at 5,700 then forget about it and go on glide. But if you’re climbing well at 3,000 AGL and lose the thermal then it’s time to go into search mode. If there’s any wind at all, the thermal is probably either directly down or upwind of you. The first thing to do is expand the size of your circle and pay attention to your mental map. If you were climbing at +200 fpm and then start sinking at -600 on the upwind portion of the 360, open the circle up back downwind. If the sink improves to -400 and then -200, move it even more downwind. If nothing good happens, try moving upwind; again, an improvement in sink is as as relevant as finding more lift, work toward the area of lesser sink. Also pay attention to your groundspeed; it will generally increase as you follow the air flowing into a thermal, but decrease if you’re bucking the wind flowing into a thermal by flying away from it (remember that thermals, especially when low, pull or entrain air into them). If I’m low on windy days I tend to fall out the upwind edge of the thermal. If I’m high on a windy day I tend to fall out the downwind edge of the thermal. I have no idea why, but that’s how it works.
I’ve seldom encountered thermals that are smooth cylinders from the ground to base; the trick is to follow your vario, wing and seat pressure up in the best lift with continual gentle adjustments to your coordinated circle.
More Clues for Better Thermalling
If the outside of your wing loses pressure suddenly and ruffles or takes a mild collapse, you’ve just found a relative difference in lift. Perhaps you’re in +600 and your outside wing just hit some +50; you want to move your circle away from the area you just took the turbulence in and toward the better lift. If you’re thermalling in a gaggle and see someone take an outside wing deflation ahead of you in the circle, then it’s probably worth tightening your circle away from that area and then opening it slightly to fly toward the better lift, tightening the circle as you encounter better lift. Most pilots tend to fly the “pattern” in a thermal rather than really watching the climb rates of the other gliders; if everyone climbs better in one half of their circle than the other, move your circle toward the better lift; you’ll climb above the other gliders quite quickly using this tactic. If someone is out-climbing you off to one side then move your circle to them; there’s no heroism in climbing slowly by yourself.
If you see the glider in front of you in a gaggle start climbing like mad, you may want to start tightening your circle immediately so you are in a higher bank angle as you hit the rising air and can “grab” more of it; again, fly the thermal, not the other pilots.
Look for pollen, plastic bags, bugs and other debris in your thermal. Birds in general and Swifts in particular will almost always be in the best part of a thermal; follow them immediately. Swifts and other small birds seem to eat the bugs that are drawn into thermals; if you see a group of them swarming upward, jump in with them even if doing so requires a short glide. Because thermals are pulling air into them, trash often automatically centers itself in a thermal; I’ve climbed thousands of feet in the company of newspapers or other debris.
Some days produce thermals that seem to want to spit you out; most of the time I’ve found that this is due to flying with too large a circle. Think of a spout of water shooting upward; if you stick your wing into the center and keep your circle within the column, you’ll go up. But find the edge and you’ll lose pressure on the outside of your wing. This creates drag, you lose your bank angle and tend to get “pulled” out to the side.
Try flying with your vario turned off; Chris Mueller and many other top pilots often fly long distances without their varios ! I don’t want to get too esoteric here, but how your glider feels in lift becomes clear if you focus on the clues. Turning your vario off forces you to pay attention to what’s really happening with your glider in different currents of air. I’ve learned a lot in the last year by playing this game, especially in gaggles where I can watch other gliders.
The smoothest air is often right in the core of a strong thermal, and your glider will be more pressurized and stable if you are flying a higher bank angle; if I’m climbing quite fast, I know that the edge of the thermal is likely to be quite turbulent. I’ve never flown away from a very strong thermal as I know I’ll hit turbulence doing so; the best thing you can do is lock into the core and take it to base.
The most extreme variations between sink and lift tend to be below five hundred feet off the deck; you’re flying along in 600 down and suddenly you’re ripping at 1000 up, then falling out of the sky again. However, the best true average climb rates tend to be higher in the thermal until it cools to the point where it won’t give you any more lift. I often will see spikes of over 1500 fpm low to the ground on days where I can’t get more than 600fpm climbs on the 20-second averager. A thermal’s real climb rate is what you can get out of it on the averager, not the “spikes.” I often hear pilots say, “Dude, I got 2000 fpm today!” They are almost invariably referring to the lift spikes and not their true rate of climb. The only place in the world I’ve seen true 2000fpm climbs is the Owens Valley in July, but crank a hard uncoordinated turn and you can easily create your own 1000+fpm “thermal” as your vario swings up and beeps happily; this is a lie, but many pilots will believe it and keep creating their own thermals with wild turns where there is nothing.
Finally, all of the above writing is just my own theory based off sailplane books, conversations with other pilots and personal experience. What really matters is your own theory; question it and refine it continuously for best results. If someone out-climbs you in a thermal it may be due to their glider, but it’s much more likely that they did something you didn’t. Don’t curse yourself as they ascend faster. Instead, try to figure out why. Are they using larger circles or smaller? Did they move their circle into better lift and you didn’t follow? I don’t believe anybody is born a better pilot than someone else, but some pilots do think about what they are doing and try to do better. I look forward to trying to do better this season, and wish everyone the best of luck! And, in the end, the best pilot is the one having the most fun.
Will Gadd will be running XC clinics across the United States and Canada this summer; check gravsports.com for a schedule or contact him at firstname.lastname@example.org if you’re interested!
By James Freeman
1) Thermal Lore
Develop a mental picture of what a thermal looks like. Thermals are rarely exactly like the textbook pictures. Watch some smoke rising from an industrial smokestack, or fast motion film of clouds to visualise the dynamic and somewhat chaotic movement of rising air. Thermals range from short lived bubbles to columns extending from the ground to cloudbase. They may be weak or strong. Some are wide, some narrow, some elongated downwind. Add to your picture with experience.
As you approach a thermal you can expect to find quite strong sink. You often run into alternating short 1-2 second surges of lift and sink as you get closer. Next you will encounter lift.
In almost all thermals there is at least one and often several strong cores of rapidly rising air surrounded by areas of more moderate lift. To find the core you must first LOOK FOR IT. Too many pilots are simply satisfied to be in lift and contentedly circle in 200 up when there is
800 up to be had nearby.
When you enter a thermal you should not stop and circle at the first indication of lift (unless very low, thermals small, etc). Instead continue flying into the thermal. Sometimes a wing may be lifted as the strongly rising air in a core tries to push you away. Do not let this happen! Turn towards the lifted wing to be rewarded with the stronger lift. Alternatively the lift may peak and then drop off without any wing lift if you fly straight through a core. As soon as the lift drops off crank a turn.
Once you have found a core that’s not the end. Expect to make minor bank adjustments every circle to stay centred and often major adjustments every 10 circles to stay in the best lift. Soaring birds rarely circle in neat circles as they search out the best lift, neither should you.
If you have been circling in a core and then lose it you should have a plan. The best one is to first look upwind first as you generally fall out the downwind side (see books for explanation). Next look downwind. Finally look crosswind. If there is no sign of the thermal after this search move on, thermals can and do have bottoms that you can fall through but unfortunately searching up is not an option!
Develop a clover leaf search pattern to explore thermals. Starting from a circle in lift explore the four imaginary quadrants of the clover leaf one at a time. You do this by extending your circles sequentially into each quadrant. After each extension come back to the centre if better lift is not found before going on to explore the next quadrant. In this way you keep track of known lift while continually looking for better lift.
Generally speaking at low altitudes thermals tend to narrower and more bubble like. TIP – NEVER LEAVE LIFT LOW. At intermediate altitudes thermals become wider and strong cores are often present. Towards the top of a thermal lift often drops of while the thermal continues to get wider. Often strong lift may be encountered near cloudbase (cloudsuck). At the beginning of the day bubbles predominate. “Classic thermals” occur during the peak of the day which depends on location but as a rule peak ground heating (and hence thermal strength) is around 2.30pm LOCAL SUN TIME. Towards evening smooth, wide weaker thermals are the norm.
Turbulence is generally worst during the peak of the day and often near cloudbase.
Thermals are generated by buoyant air. Air becomes buoyant because it is less dense than the surrounding air. Differential heating of the ground causes differential heating of the layer of air above the ground. The warmer air expands becoming less dense and thus buoyant. Perhaps
surprisingly the addition of water vapour also makes air buoyant. This is because water vapour is 5/8th as dense as air. So in general we look for areas that will be hotter and or have moisture added as likely sources of thermals. Beware that to much moisture can have a detrimental effect, whereas a little can have a very beneficial effect. A good way to get a feel for this is just take a walk and observe the temperature – if the air feels hotter then the surface you are walking over is a likely THERMAL GENERATOR. Classic generators include dark ground, burnt areas, tarmac roads/carparks, etc. Sand reflects heat so is bad. Some crop paddocks get surprisingly hot, whereas others are cool. The vital point to remember is the concept of differential heating – what you want is a contrast. By a contrast I mean an area that will get hot next to or better still surrounded by area which are cool. The edges of forests,
river banks and lake edges are all potentially good. Areas which heat up fast are good at the beginning of the day. Areas which heat up more slowly can be good towards the end of the day – for example you often find thermals over forests later in the day.
Just because air is buoyant does not guarantee a thermal. Just as water can cling to a ceiling until a drip forms so buoyant air can cling stubbornly to the ground. Before anything happens it must be TRIGGERED to release. A good analogy is to imagine that the ground is the ceiling of a steam room. Anywhere you would expect water to drip from so you can expect thermals to trigger from. In practical terms look for high points. The flatter the ground the less significant the high point. In the mountains ridge tops are good but in the flatlands treelines, houses, rockpiles and even lonely telegraph poles all act as triggers.
Wind complicates the picture. Buoyant air can drift with the wind along the ground until it is triggered far from where it was generated. In this case sloping thermals result and you will tend to fall out the downwind side unless you continually centre the core by flying upwind
(due to the fact that the thermal rises ~200 fpm faster than you do because even though you are climbing up from the ground you are always sinking down through the air. Alternatively the internal turbulence of the moving mass of buoyant air may cause it to trigger independent of
ground features – in this case the thermals will be, perhaps surprisingly, vertical because the source is moving with the wind.
Wind also influences the nature of thermals. Strong winds encourage thermal triggering resulting in short lived bubble type thermals. The air in areas which are protected from the wind can continue to get hotter for longer before triggering – this often results in strong lee
side thermals. Crop paddocks often hold onto their heating airmass for longer and can be better thermal generators than the classic ploughed paddock in windy conditions.
Experience shows us that whenever the wind blows thermals will generally be far longer downwind than they are wide, often with several cores lined up downwind.
On any given day thermals tend to remain similar in nature, unless of course there is a large change in conditions.
2) Bank angle
Good thermal pilots do not necessarily bank more or less than average pilots. What they do do is bank as much as is required to position their gliders in the core of the thermal.
Although some authors labour on about optimum bank angles the rule is simple. Bank up enough to stay in the core! Experiment. More bank -> better climb? -> continue banking it up. If more bank leads to a slower climb then make shallower turns.
We expect small bubbles near the ground so expect to have to bank it up. Late in the day wider thermals are the norm so shallower turns are usually the go.
So how do you centre the core? There are several methods, of which I will mention two.
The standard method is to tighten your turns when the lift drops off (to bring the glider quickly back into the best lift) and to flatten the turns as the lift increases (to fly into the best lift).
The pro method is to fly into the thermal, feel the glider react to the air and then crank (bank it up) when you hit the core – more on this next.
Some pilots have a better natural feel than others, but don’t despair its really quite straight forward.
As you correctly point out variometers have some lag. Sure some are faster and more sensitive than others but as a tool FOR CENTERING thermals they basically suck. Heresy to some no doubt but still true.
In a big gaggle at any given comp you will see pilots circling around many different points. Why is it so? They can’t all be in the core. The fact that some pilots climb much faster proves the point. These eccentric circles result from what I believe is a total over dependence on variometers combined with the standard method for coring a thermal described above.
OK, here is what happens. Consider a glider flying in a straight line at 24mph (36kmh/10 metres per second) straight across the centre of a thermal. It will take this glider 9 seconds to traverse a thermal 90m in diameter. Lets say this thermal has a 30m or 3 second wide core in the centre. The glider enters thermal and is accelerated upwards. After a lag of say 2 seconds the glider ascends far enough for the variometer to note a change in air pressure and indicate a climb. Military studies indicate it will take about 1 second for the pilot to process this information by which time the glider has entered the core. A further 2+1 seconds elapse while the glider accelerates/pressure changes/pilot assimilates change. Just as the pilot notes he is in the core he in reality actually flies out of it. Using classical theory he decides to bank it up when the vario indicates a drop off in lift. This occurs 2+1 seconds later just as the glider exits the thermal. The pilot now banks up the glider which takes a further 2 seconds due to glider response lag. At this stage the pilot is actually 20m past the entire thermal! You can continue this description on indefinitely however the point is this:
“The classical method of centering a thermal will only work if there is no lag in variometer response, pilot (processor) response, and glider response”
So now we come to the secrets of thermaling – visualisation and feel.
The mark 1 accelerometer.
All of us come equipped with remarkably sensitive accelerometers which are perfect for thermaling once we recognise both their power and limitations. We can sense very small accelerations but feel nothing once the acceleration ceases and we are moving at a constant velocity. Our experience in our cars or in a lift shows us this. We feel the initial acceleration but while travelling at constant velocity we feel nothing until we feel the deceleration as we slow down. Our accelerometer is excellent for thermaling.
Our second key ability is our power of visualisation. Just as we can build up a mental picture of a dark room by wandering around bumping into the furniture we can build a similar picture of the invisible currents of air by flying around and bumping into them.
Here’s how its done. Consider our pilot again. The instant he enters the thermal he senses the acceleration. The instant he hits the core he uses all his senses to note the strong surge of lift causing a strong acceleration which combines with a tendency for the gliders nose to pitch up to signal to his brain CORE! The one second processing lag means he is still in the core when the message arrives. Two seconds later he exits the core which he notes as a deceleration (like falling) and the nose of the glider pitching down. One second for processing lag and he initiates his turn. Two seconds later after response lag the glider turns, but this time is still in the thermal.
OK so far so good but we are still going to be plagued by the dual problems of processor and glider response lag. Here is where visualisation takes over. The pilot now constructs a mental picture of the thermal, where he is in it, where he is going, and finally what he needs to do to centre his circle on the core. With each circle more information is added to this mental map until coring becomes as easy as driving round a round about. In simple terms say you are flying south when you feel yourself fall out of the core. OK you think the core is nore to the north so after a 180 you flatten out your turn for a couple of seconds then resume your circle, you are now circling further to the north and should be closer to the core.
Now we come to refinements. The first improvement is this. Pilot hits core and processes it 1 second later. Knowing that the glider response will lag 2 seconds he initiates an immediate turn – presto he is turning in the core, admittedly perhaps not yet centred but still streets ahead.
The second improvement is to recognise the glider as the extension of your body that it really is. Just as you can feel if I come up and push you so you can feel if a thermal pushes your glider. But how do you tell if a wing is being lifted and differentiate this from a wing which is
sinking on the other side, after all they will both result in a roll in the same direction? Lift will be associated with an upward acceleration, cause the gliders nose to pitch up, and if off to one side cause a wing to rise. Sink or less lift (relative sink) will be associated with a downwards acceleration (falling feeling), the gliders nose pitching down, and if off to one side a cause a wing to drop. The bottom line is that differentiating wing lift or drop doesn’t actually make that much difference. Why? Because in either case the glider is heading AWAY from where you want it to go! Be your own boss. Don’t let yourself be sucked into sink and spat out of lift.
The next refinement is speed control. Linger in lift, speed through sink. This goes for thermals to. Sometimes the core may be too small to circle in. Sometimes the air is so bubbly there are no long lasting cores. We can maximise the time spent in the lift by slowing down as much as possible as soon as we sense lift. Our gliders make this easy for us as the nose pitches up automatically. Don’t fight it relax and let it, depending on your speed and altitude (not at 50′ please) slow some more. Stall? Oh well slow a little less next time. You will be surprised just how far you can push the bar out when banked up in a strong core. Make sure you have enough height to recover from an unintentional stall before experimenting.
So what is the role of the vario. Well once we are centred it will happily chirp a continuous tone which is good because now we will get limited feedback from other sources. It also remind us we are not centred by showing oscillating lift strength.
There is no substitute for practice and the best way to see how you’re going is to go to competitions. You don’t need a high performance glider to have fun. I flew 185km (~115miles) in a Moyes XT intermediate glider in my first comp. Ask questions. Read all you can. Buy a copy of Cross Country Soaring by the late sailplane world champion Helmet Reichmann from Amazon.com or the Soaring Society of America – it covers all of this plus speed to fly in great detail.
Thermal Search Patterns
A few people have written to ask for a bit more info about search patterns so here it is.
There are a number of circumstances where a search pattern is particularly useful.
1 When you are low, desperate and in marginal lift
2 Whenever you lose the core
3 Even when you feel you are in a “core” to efficiently look for even
The first place I started to use a search pattern was making low saves. You know the scenario. Gliding, gliding, gliding. Lower, lower and lower. Finally you hit a few bumps and latch onto a workable bubble. You are low so you can’t afford to make too many mistakes or you will be on
the ground. The lighter the lift the better you need to perform. Once you have found some lift you don’t want to lose it right? But say you have only found zero sink, or worse 50 down. You need something better, but you still don’t want to lose what you’ve got. After a few circles to
establish yourself it’s time to go hunting. Sure some pilots just seem to be able to feel which way to go but for mere mortals using a search pattern is the way to go.
The essence of the search pattern technique is to NEVER lose track of your known “good” lift. You maintain contact with this known lift by centring your search pattern around it. Imagine this lift is situated at the junction of an imaginary cross roads. The 4 imaginary “roads” which
lead away from this cross roads represent your search directions. What you do is effectively explore a little way down each of the 4 “roads” which lead away from this crossroads. If, after you explore a little way down a “road” , better lift is not found you return to the crossroads,
maybe do a few reassuring circles, then try another road. If better lift is found you circle in that then repeat you search using this new area of better lift to search out from.
Typically a low save might go something like this. First you usually hit a few bumps of alternating sink and lift (pilots usually refer to this air as feeling live). Crank a turn as soon as any solid surge is felt (using the MK I Accelerometer rather than the variometer). Consolidate
for a turn or two moving towards area where best surge of lift is felt as acceleration up (not the same a best vario response due to lag). Check variometer averager to see how you are going. Allow heart beat to return to normal if averager shows positive number but don’t dawdle if you’ve only achieved 50 down. Flatten turn and head in one direction (say north) for say 3 seconds then do a 180 degree turn, fly south for 3 seconds then resume original circle. You have then explored ~100 feet to the north of your known good lift before returning to your circle in this lift. The same procedure can be used to search the other three main directions (E, W, S). You can explore greater or lesser distances by varying the time you fly straight for. Provided you fly the same number of seconds out and back and do an accurate 180 degree turn you should never lose track of your area of known lift. You search distance should be tailored to the expected size of thermals on the day, in the local area, and at your altitude. Initially I usually make fairly nervous little explorations before running back to circle in the centre. If experience shows that the sink monster is not lurking nearby I get a little more adventurous. Sometimes their simply is nothing better nearby. If you already seem to be in the best available lift patience is required and endless searching will just lose you altitude so you need to use this technique with restraint.
When you’re really low the direction of the first explorations can be critical as you simply don’t have enough altitude to explore far. Typically this direction will be either:
1 A continuation of the direction I was going when I hit lift on the basis that I was desperate and probably started turning before I got to the thermal proper
2 Towards any wing lift or area where better climb is felt
3 Towards any circling birds, leaves, etc
4 Towards any likely trigger areas like tree lines, etc
5 Upwind as we tend to fall out the back side of thermals
6 According to the formula:
Turn Direction (in degrees magnetic)= [Dry adiabatic lapse rate + altitude (in feet) - barometric pressure (in hectopascals) / 3 *log (# fairies dancing on head of pin in local area)] + RND(n=360)
The benefits of adopting this search technique in low save conditions are:
1 To maximise the chances of finding a good climb
2 To minimise the time taken to find the best climb going.
3 To minimise altitude loss and thus minimise the risk of decking it.
A search pattern is the most effective way of ensuring that low save. It is also a logical way to search for lost cores or look for better lift during general thermaling. You will find the core more often if you look for it. You are less likely to miss it if you do a logical search pattern rather than blundering around hoping for the best.
If you look at racing a glider, or long distance XC it is in large part a climbing contest. Inter thermal glides are definitely important (indeed vital) but the fastest pilots over the course are invariably amongst the fastest climbers. If you have ever been fortunate enough to watch the really top pilots like Tomas Suchanek and Manfred Rhumer in action you will see them continuously exploring for the best lift, but usually not for long because they find it, out climb you, and are gone.
I once heard a pilot say “As soon as Tomas flew into this 400 up thermal it changed into an 800 up”. Witchcraft? I think not. The truth is that he led the other pilots into the core. Looking for and finding the core, at whatever altitude, is just one of the many secrets of the black art of thermaling.
Thermalling Hints by Wayne Hobbs
Thermalling is an advanced flying skill that most pilots will encounter late in their Hang 2 skill level, and really concentrate on as they enter their Hang 3 rating. I think from personal experience and from observation, that there are many styles of thermalling.
Mine have changed over the years and especially since I began flying an Exxtacy rigid wing. Any of the advice and techniques I list below may be heavily influenced by what I’m flying, so take that into account when you try and translate it for your equipment.
As always, I bring up a topic like this to provide my own narrow minded view but primarily to bring about discussion from many listees, who are far moreable to put into writing, what I intuitively understand, but can’t alwaysverbalize.
I have been fortunate to have been around to read many great articles written across a very long time span of Hang Gliding issues and some I have re-read more than once. I have also, and advise you to do so as well, read many sailplane books on thermalling to help build my knowledge base. I still do so because just like you, I am also still learning. From a hanggliding consensus, some things that seem to be general rules are:
1. The lower you are in altitude, the higher the bank angle you will need to thermal at, to stay in the thermals, because they are likely to be small. Better to over bank at first than to under bank.
2. As you gain altitude, thermals often widen and strengthen, and you are able to lower your bank angle and often obtain a better climb rate.
3. Often I see pilots bank to quickly upon encountering lift and then fall off the thermal as they do their down wind rotation. A very good rule of thumb is counting to 3 before you turn. If you are low, then quickly may be your best option as you don’t have time and altitude to spare.
If higher, than you can afford to wait a little longer to explore the width of the thermal before you turn. I prefer waiting as I’d rather turn back for a thermal that’s behind me, than fall off the edge and lose altitude before I can rotate back to the lift.
4. Locating and staying within the thermal is often a tricky part of thermalling and we use different tricks to do this. One of the most important for new pilots to start out using, I think, is to visually locate a point on the ground below where you are thermalling so you can obtain a reference point. Recognizing that your thermal will drift with the prevailing wind. Strong thermals don’t seem to drift as fast as the wind so don’t over estimate the drift rate. If you lose your thermal, be sure and do a search down wind and then upwind on your expected drift line.
5. Instrument location is also an excellent way to thermal and especially useful at higher altitudes. It is the method I use, so don’t fly close to me when you see me thermalling! In this method, you actually watch your instrument climb rate and as it peaks in strength during your rotation, you pick a point on the horizon off your outside wing and as you come back around, you move your thermal circle in that direction. Also keep in mind that your instrument deck has a delay in it so a good pilot will recognize that maximum lift actually occurred at a point slightly behind this visual
point and adjust his circle accordingly.
6. The most efficient thermalling circle is one that is very concentric.
I am speaking from a glider efficiency point of view. It is also easier to stay centered if you can circle concentrically. Advanced pilots will often change their bank angles constantly as they milk the pulses in a thermal.
I’d advise waiting a while on that technique as it can cause you to lose the core.
7. The most common mistake I see in recreational thermalling, is that pilots fly through lift without testing it and giving up on lift to soon.
If you fly through some lift that is more than 2 seconds wide, and you have a safe glide to a landing field, unless you have a visual reference of something better, than I’d advise you to turn and explore what you just flew through. If you are in lift that is sustaining you, or allowing you to climb, unless you have a visual reference of something better, than I’d advise staying right where you are and continue to work and explore what you have. This is key to becoming a sky god!
8. If the core is tight and strong, then I’d advise flying it in kind. Meaning attack it with high bank and higher flying speed. If the core is broad and mellow lift, then fly it the same way, lower bank, lower speed, and mellower.
9. THE MOST IMPORTANT 100 FEET OF CLIMB IS YOUR FIRST 100 FEET! I can’t emphasize this enough.
If you can climb 100 feet in a thermal, then it is likely that you can climb out on that thermal. The first 100 feet is generally your hardest and longest, so really sink your teeth into it. Get mad if you need to . Be aggressive.
Act as if you don’t stay in this thermal then you will have to go land (this might be true!).
10. If you have landable fields down wind in the direction that you are thermalling and drifting, then quit worrying about the landing field! This is also a very important lesson to learn and remember.
11. Depending on your site, don’t be afraid to drift up, over, and to the back side of your hill as long as your are high and can stay safe from rotors. Ask your local mentors what they think is a safe altitude for the wind conditions and your equipment.
12. Learn to be patient in your thermalling. It is very easy to climb and then bail out down wind for distance and then find yourself on the ground watching your more patient friends flying over and into the distance as you break down. Don’t out fly the lift. Unfortunately, I speak from experience on this matter!
13. Try and fly with, and like, those mentors who always seem to thermal well and stay up the longest in the thermal conditions. They must be doing something right.
14. Don’t be afraid to be at high altitudes. The rules of aerodynamics are the same. The higher you are, generally the safer you are. It just doesn’t look that way.
15. Be aware that learning how to thermal will be something you will be working on for the next 50 years of your hang gliding career. It is never mastered, only improved upon!
There are many more, but these should give you newer pilots some food for thought and hopefully others will add to, and correct, some of my mis-explanations.
GRAHAM’S XC TIPS 1
This is the first of what I hope to be a regular feature in the newsletter. Don’t take what I say as Gospel, you should verify it for yourself in your own flying. What I say should be used as things to look for and to try. Develop an exploratory attitude to your flying. It is best to fly the air more than the theory. Often things happen for which there is no easy explanation. If you are locked into a theoretical idea that the lift will be in set places and that you should do set things to utilize it, you will miss opportunities that can greatly improve your understanding of the air and hence your flying. The discussion will be from a paragliding perspective, but should mostly be applicable also to hang gliders.
The classic model of a thermal is a nice column of rising hot air. Around the Sunshine Coast this is more the exception than the rule. Mostly the thermals are much more complicated. You have to be continually adjusting your turn to maximise your climb rate. Thermals can have multiple cores that shift, merge and peter out. There can be bubbles and lines of lift.
It’s a good idea to sit down with a pencil and draw a horizontal cross section of a thermal and think about what your vario will do and how you should turn for all possible ways of hitting a thermal and being off centre in your circling.
ie draw a circle to represent a simple classical thermal. The closer to the centre you fly the stronger the lift will be. Outside the circle the lift drops off gradually to nothing.
If you fly into a thermal at the edge, the wing tip in the strongest lift can be lifted and the vario starts beeping. On a paraglider you may also notice that the brake pressure can increase on the strongest lift side. You should turn into this stronger lift side. Be aware that this lifting of the wing on the stronger side will tend to turn you away from the thermal, so have to go the opposite way to the way it wants to turn you.
If you hit a thermal dead centre, or the edges of the thermal are indistinct, there may not be much difference from one wing tip to the other. You will first feel the upward acceleration then a second later your vario will beep. (varios have a delay). If you are looking at the circle you have drawn you can see that to most quickly core the thermal you first need to turn one way before turning the other. ie following the shape of a question mark. When I hit a thermal and feel no difference from one side or the other I will often gently turn one way. If my climb rate drops off I roll into an opposite bank to follow the question mark shape. If instead my climb rate picks up, then I continue around into a simple 360.
The alternative is to fly right thru the centre of the thermal and initiate a turn as soon as the vario shows that the lift is starting to drop off on the other side. In this situation your first 360 is likely to be off centre with more lift on one side than on the other side of the 360. (follow this on your drawn circle).
This initial flying straight thru the thermal first is most useful while still low on the hill as it gets you further out from the hill and can often allow you to follow a line of lift well out headwind from the hill.
Look at your thermal drawing and imagine you are following an off centre circle that goes thru the centre of the core and also outside the thermal at the other side of the 360. Notice that AS SOON as the lift STARTS increasing you need to flatten out your turn for a bit before pulling back into the turn. Also as you leave the thermal you can tighten your turn a bit to minimise the time you spend outside the thermal. Be aware here that a tight turn is not an efficient turn so the opening up of the turn as the lift increases is more important than tightening the turn are the lift drops. In fact I generally don’t tighten my turns much at all as I fall out the side of a thermal I rely mostly on opening up my turn as the lift increases.
Sometimes you commit to a turn one way only to find you have just flown out of the thermal. Continue the turn for 270 degrees (you can tighten it a bit if it feels comfortable) before opening it out as you renter the thermal.
It is best to keep turning the same direction, opening up the turn and tightening it to shift the centre of your turns in increments into the centre of the thermal. If you change the direction of your turns you shift your circle a full diameter to one side and can loose the thermal.
Cross Country Tips 4
Some important things to know about thermalling for inexperienced XC pilots are:
Let yourself get well into a thermal before starting a turn. Some people say wait 4 seconds as this is about how long it takes to fly across the diameter of a 360. Another (in my opinion better) approach is to keep flying into the thermal until the vario reaches it’s peak, then immediately turn as soon as the climb rate starts to drop a bit. There are delays in the vario, in your reaction time, and in the response time of the glider that will centre your turn somewhere near the peak of the climb rate. These approaches allow you to fly thru much of the thermal to see how big and strong it is before you turn back into it.
If you hit lift that lasts more than a few seconds then do turn. The most common mistake of novice pilots is to fly straight thru thermals. If you’re too close to the hill to do 360′s then do figure of eights.
The strongest part of a thermal tends to be on the upwind side, as faster climbing air doesn’t drift back as far as slower climbing air.
If you commit to a turn and the vario drops such that you realize that you’ve turned the wrong way:- Continue the turn for 270 degrees, then straighten up for a few seconds and you’ll be back into the core ready to commence the turn anew.
YOU HAVE TO CONTINUALLY NOTICE WHICH SIDE OF THE THERMAL HAS THE BEST CLIMB RATE, AND KEEP MOVING YOUR 360,s OVER IN THAT DIRECTION. The way to do this is to open (flatten) your turn for a couple of seconds just as the vario STARTS to increase on the stronger side (don’t wait for it to peak). This moves the centre of the turn over by about one radius. It is better to just move your circles over by these small increments as if you flatten out for too long you can lose the thermal.
Inexperienced pilots should not normally change turn direction while in a thermal as it will move the centre of the turn over by at least one diameter, and this can cause you to lose contact with the thermal.
Just because you lose the thermal don’t give up too quickly. Thermals tend to be multi-cored. The most likely place to find a thermal core is close to the core that has just died or you lost. So if you fall out of it, have a search around a bit before giving up. The best place to look is often straight upwind, but any other direction can work also. Go which ever way that the strongest side of the thermal seemed to be on. Don’t let yourself drift too far back over the hill though. It takes quite a lot of experience to know how far you can go back behind and still get back out in front of the hill.
Tight turns are inefficient and are only worth doing in small, strong cores. It’s normally better to do flatter turns that have a better sink rate. Do your turn as you would turn when scratching low in light wind on a small coastal site. ie it’s a compromise that minimises the diameter of the turn without badly compromising sink rate.
Don’t be afraid to bomb out, it happens to the best of us and is a necessary part of the learning process. I’ve seen Godfrey Winness in the bombout when others are getting away. Coastal pilots tend to develop habits that are counter productive or dangerous when flying inland. An aversion to bombing out is one of the merely counterproductive habits.
Inland flying is not as predictable as coastal flying. There’ll always be days when you go home disappointed, but this is more than made up for by the good days. There is nothing on the coast like hooking into a thermal and climbing out, watching the ground recede away, when you thought you were about to be on the deck.
XC Tips 7 Planning your XC flight path
For everyone but gun pilots, the best way to maximize your XC flight is not to be trying to go big distance but to be trying to stay up as long as possible. This is the most difficult bit and needs to be the main focus of attention.
When they hit the top of a thermal, many beginning XC pilots think that they have to head off on a planned course. This is only what you do if you are very high and there are good-looking clouds along the way. Firstly if you are not at cloudbase it is worthwhile looking around to see if there is another core nearby, as the most likely place to find another thermal is right next to the core you have been working. It’s worth while committing a couple of hundred feet to making sure that there isn’t another core nearby before you risk losing a couple of thousand feet going on a long glide. A bit of a search pattern is a good idea (try not to search thru the same place twice), maybe trying upwind first as stronger cores climb more vertically and so will be upwind. However other cores can be in any direction. Down wind is probably the second most likely place to find another core but is usually the last place that you look as you check it last thing before heading off.
If you are at cloudbase, then you are looking to perhaps head for the nearest building cloud that is roughly in the direction you want to go. If it is all blue in this direction it is often better to sidetrack around it or even wait for a little Cu or two to begin to pop in it before proceeding. I have even gone back headwind to a good cloud a kilometer upwind when the cloud I was under died and there was only a big blue hole in front. Half an hour later I over-flew where I likely would have bombed if I had tried to cross such a blue hole with insufficient ground clearance to glide across it.
As you’re climbing, watch surrounding clouds to see where they are popping and how long they are lasting. There is no point heading off on a long glide to a cloud at the end of it’s useable life when it will have turned to crap by the time you get there. Often clouds keep forming in the same areas. Those are the areas that you should be incorporating into your flight path. Don’t be reticent about making big detours in order to be able to follow where the best lift is likely to be.
When high, you should be following the clouds, not the roads. You tend to go where you are focused. If you are focused on roads and bombouts, that is where you will end up all too soon. Don’t be afraid of a long walk out, as that is also part of the adventure. The real beauty of paragliders is that we CAN walk out and easily hitch hike etc.
Try to stay high. Inexperienced pilots are often not persistent enough. They tend to leave dribbly bits that might just allow them to maintain height until a stronger core comes thru. Remember that once you leave whatever pitiful lift you might have you are going down. It is better not to commit a shit load of height going on a long glide if you don’t have to, or unless there are good indicators of lift ahead.
Don’t however, allow yourself to be so focused on getting up and staying up that you can’t glide to a safe landing somewhere if it all dies. A safe landing should always be within reach, even allowing for the possibility of hitting sink on the way.
by Will Gadd
…with input from many top pilots who patiently and repeatedly answered the question, “What’s important for successful XC flying?”
The first step toward successful cross-country flying is simply leaving the security of the local hill and venturing out into the wide world. It doesn’t matter if a an XC flight ends one or 100 miles from the start point, but that it was attempted. For every flight that ends in a new LZ requires the same basic set of skills: An appreciation of local conditions, constant analysis of immediate air conditions in flight and, above all else, a safe place to land at the end of a flight.
The planning of an XC flight is often as or more important than the actual flight. For example, task committees at competitions set tasks every morning armed with the best information they can gather on wind speeds, possible cloud development, barometric pressure, satellite photos and every other scrap of information they can muster. As your own task committee, get as much information as possible before setting your task. There are also days that simply aren’t good for going XC; rather than forcing a day to meet your goal, set your goal around the day. Assuming the day looks reasonable for XC flying (no thunderstorms forecast for noon or other large-scale problems), a good map of potential routes is essential, preferably one with airspace restrictions,
mountain ranges, major roads, powerlines, railroads and other feature visible from the air.
Information from any local source about XC flying always has to be examined with an eye toward who is giving it, but I like to pump local HG and PG pilots about where they have been and what happened. For example, they may know that a local canyon turns into a death venturi about noon every day, as well as good thermals or areas where the powerlines make landing all but impossible. After establishing the general conditions for the day and area, the next step is to set some kind of goal and state it: “I’m going to fly from Aspen to Leadville.” Even if you don’t make your goal, you’ll still learn something about XC flying, while you’re guaranteed not to learn anything if you’re boating around with 20 other pilots at the regular hill. XC flying in a group has advantages, but it’s often difficult to get anyone to go with you. Break the herd mentality and go anyhow, but try to tell someone generally where you’re going in case you don’t show up later. In many states, a fishing license covers rescue costs for the purchaser; it’s a small investment that can go a long way.
Because paragliders go upwind very poorly, upwind flying should be kept to a minimum. Understanding local wind conditions such as the difference between morning, afternoon and evening valley flows versus predominate winds aloft can be critical. Using Aspen as an example, the wind usually flows down the valleys in the mornings and evenings and up the valleys in the afternoons, often in direct opposition to the winds aloft. If you’re flying XC in valley terrain, generally plan your flight to go with the wind aloft, but realize that the wind low in the valleys may be very different. The windward side of a high mountain ridge may well be the lee side of a ridge facing the same direction in the valley and vice versa; it usually only takes getting rotored hard once to appreciate this phenomena.
Say the wind is out of the West, and you’re flying a valley that generally runs from south to north, with the top of it at the North end. It’s evening, you’re getting low and returning from a long XC, and you’re coming down the valley from the north. A long spine sticks diagonally out into the valley from the East side, it’s in the sun, and it’s about a perfect glide from where you are now. You know the wind is from the west aloft, so you head for southwest side of the spine, arrive there very low and get hammered because the valley wind, with a strong valley flow, is pumping down the valley, essential from the North. You get rotored into the trees, it gets dark, you have a lousy walk.
Although it may seem morbid, I repeatedly analyze my current XC flying situation by asking myself, “What’s the worst possible thing that could happen here?” This tool helps me choose what I want to do in light of what could kill me. If there is a set of high-tension wires between me and my next thermal source, then it’s key to get enough altitude to clear them. Every paragliding flight has numerous situations that could be lethal, but I think being aware of the possible dangers is critical to avoiding them. For example, scratching valiantly all way down to an LZ is a good effort, but not if it puts the pilot too low to glide to a safe LZ (funny how trees tend to get bigger when you have to glider over them).
Understanding the dangers in every given situation also forces the pilot to have a plan. I like to think of XC flights as a series of small steps that connect individual points into a line ending at a goal. If you fly with a plan and an attitude of success, you won’t get bogged down in indecision until you waffle your way to the ground. Decide what you think will work and then try to do it; if your plan doesn’t work you’ll at least learn something about what not to do instead of suddenly being on the deck for no good reason.Once in flight, always have an LZ you can effectively use within an easy glide. While XC gods can get away with diving into areas without LZs, it’s not a good plan to start with. Once you gain altitude and go on glide to your next thermal source (cloud, ridge, whatever), switch from your first LZ to a new one. This process will soon become instinctive, but until it does LZs define XC flying. Like driving an unfamiliar road at night, safe XC flying demands an extra safety margin for unexpected conditions.
An often-heard XC mantra goes, “When you’re high, fly the sky, when you’re low, fly the ground.” Clouds are usually the best indicators of lift, so try to get to cloudbase and then work from cloud to cloud, paying attention that the cloud you’re shooting for isn’t developing extremely rapidly or decaying. “Fly the sky” just means flying from one cloud or cloud street to another, based on how the clouds are developing or dissipating. It’s hard to make the switch from looking at the ground for thermal sources to the sky for lift, but the paradigm shift is essential for long-distance flying.
While thermaling up under a cloud, remember to look at the cloud regularly; it’s amazing how quickly you can be hundreds of feet below it one moment and totally whited out the next. Plan your last turns to take you to the edge of the cloud, and leave a safe margin so you don’t get sucked into the cloud. If you do get sucked into a cloud, radical spiral diving is often the only effective method of descent in strong lift. As I approach the bottom of a cloud, I like to dump trim, step on the speed bar and, if necessary, pull big ears while blasting out from under it. If the lift is extremely strong, get a bearing on your compass before you hit the edge of the cloud so you can navigate out the side in a worst-case scenario.
While it’s important to fly the sky, sooner or later you either end up low or flying on a day with no clouds. First, while you are high and on days with clouds, try to connect the cloud to the feature or area that’s causing the cloud. Try to find patterns to thermal development for your area for
particular types of days; on days with strong winds, thermals more often come off spines; low-wind days generally result in thermals from bowls, while areas where multiple ridges come together are often very reliable. While every pilot has theories on what works for thermals and what doesn’t, it’s essential to develop your own models and check their accuracy, because in flight you’ve only got yourself.
If you get low, pick a likely spot in the sun, one that meets all your mental requirements for what a likely spot is, and wait for a thermal. If you get to a suspected trigger point and find no thermals but zero sink, wait and things will probably get better. You wouldn’t leave your local site if a thermal didn’t come through in thirty seconds, so treat your likely thermal spot the same way. Ridge soaring is one good but often overlooked trick for staying in the game while flying XC; you can use valley wind flow on a ridge to soar until a thermal comes through, just be careful to establish wind direction early.
Watch the vegetation, dust and trees to determine local wind direction. For example, dry grass leans over in line with the wind, while leaves will flip upside down with the wind. In addition to establishing wind direction, these changes often indicate that thermals are lifting off near the disturbance. Dry, dark areas of ground produce better thermals than wet, lighter-colored areas, with moisture content more important than color. For example, dark, dry fields are usually very active thermal generators while green grass seldom is.
In general, height is safety in paragliding, both in case you put your wing through a maneuvers clinic and also so you don’t land early and watch all your friends fly over your head at cloudbase. Be patient with the day while flying XC, which means waiting for good conditions to develop, and also flexible, meaning that it’s not only OK but often imperative to modify your goal as the day changes. Flats generally take more time than mountain ridges to start working, as do deep valleys or shady hillsides. If there’s no development for the next ten miles of air, get under a cloud and just wait for the sky to improve. Likewise, unless you’re at cloudbase, don’t fly over shady areas. Thermals come from the sun, so no sun almost certainly means no thermals, no matter how much try.
Fight to the bitter end to stay up, but always accept your fate early enough that you can still make a good landing in a safe LZ. Allow more room for error than you would at your local LZ; think about how carefully you looked at your local LZ the first time you flew it, then think about having to establish the hazards and problems of a brand new LZ from the air. Look at the ground for strings of telephone poles (visualize the wires running between the poles both in straight lines and at right angles to unseen poles), ridges that could cause mechanical turbulence, drifting smoke, wind on lakes, dust blowing and any other clue you can find for wind direction and hazards in your LZ of the moment.
When choosing an LZ from the air, pick one shaped like a runway rather than one shaped like a square. All other things being equal, long and narrow is better than short and wide because you can line up on final and not worry about needing to turn near the ground if you get unexpected lift or sink at the last minute.
I like to land fast rather than boating around waiting for something bad to happen, especially in strong mid-day conditions. If I’m landing in a baking field, I usually pull in two lines of big ears and come in hot, only flaring as my feet almost hit the dirt. I’ve seen too many accidents where people come into an LZ and float aimlessly around, until they get hit with a strong thermal cycle or dust devil close to the ground. Although I’m not sure why, it seems like landing in a field often precipitates thermals out of that field. Awing in serious big ears coming in fast is extremely stable and more likely to simply slam through small, violent thermals than be slammed by them.
If you’re committed to an LZ and you suddenly see powerlines in your path, it’s better to crash downwind, stall your glider or B-line to the ground than to hit most powerlines in LZs. If the electricity doesn’t kill you the fall out of the lines will.
Remember to radio your potential landing position while you still have a line of sight or communication with other pilots in the air. Your signal goes much farther from 500 feet above the ground than it will once you have landed.
Equipment for XC flying
- A wing you feel totally comfortable on. XC flying puts enough demands on a pilot’s skill without having to learn how to fly a difficult wing. Competition wings do have good glide and speed, but it’s more important to trust your equipment in the lee of a big ridge or while landing in a tree-encircled LZ than to glide a little farther;
- A map of where you’re going and where you could conceivably end up. Most hunting stores sell these nifty clear map holders you can strap to your leg. I put my cheap compass in this clear case so I can navigate out of clouds should I get sucked into one.-A first aid kit fortified with industrial strength painkillers. If you crash a long way from a road, your only chance may be to take good painkillers to help prevent shock and keep you clear-headed enough to talk to the rescue helicopter;
- Radios, both yours and the chase crew’s, should have adequate batteries. I like to carry a spare clip of alkalines that I can plug into my radio in an emergency. Agree on a frequency and write that frequency down so that if the dial gets pumped you can remember which channel to use;
- A GPS is a great tool for judging wind speed, landing position, air speed and distance. Two GPSs are especially handy when flying over featureless areas, one for you and one for the chase vehicle. “I’m over the brown field” generally won’t get you retrieved, while Lat. and Long. coordinates will;
- Cell phones are increasingly useful for retrieval, especially if you fly with a list of numbers for all your flying buddies with cell phones;
- Water and food, especially water. You can walk two or three days without food, but you’re dead without water;
- Matches, a signal mirror and flag tape are also all useful.
Bio: Will Gadd flew more 1000 total XC miles on his Edel Energy during the ’95 season, and hopes to fly many more this year. Later he set two world distance records. The opinions above are gathered from his own experience and comments from many other pilots.
THE SAHARA CONCLUSION
Let me start by explaining the Hexagon Theory from the beginning. In the 1980s there was a group of French meteorologists who went on a trip to the Sahara to study the way that clouds form in a region with no thermal sources. The desert they studied was covered with small sand dunes and there were no other significant features. The sand was a uniform colour and there were no mountains or hills to form or trigger thermals. When the atmosphere was unstable the thermals still set up in the way you would expect, but they had some rather astounding conclusions. They concluded that in nil-wind conditions, the thermals form along the edge of hexagonal patterns. These hexagons are regular in shape with the length of each side being 6 km.
Imagine a saucepan of water on a stove to boil. As the water boils it will form bubbles that rise in the same way thermals rise through the atmosphere, and these bubbles will rise in some areas and the water will also flow down to the bottom of the pan in other areas, thus forming cells of water that circulate. The size of these cells in a saucepan is of course only a few centimetres across, but in the atmosphere the same type of thing happens on a much larger scale. The exact length of the sides of the hexagons will of course vary according to the density and viscosity of the air. The height of the cloudbase and the strength of the thermals will also be important factors, but you can understand the principle.
Here comes the interesting part. When there is wind, the theory says that two sides of the hexagon will line up automatically with the wind direction, and these two sides will then become longer. The stronger the wind the longer these two sides will become. The other four sides of the hexagon will remain 6 km long. These long sides of the hexagon are of course cloudstreets.
IMPLICATIONS FOR PILOTS
This has important implications for pilots flying in cloud streets over flatlands. Firstly it means that cloud streets do not go on forever, but are of limited length and fit together into an elongated hexagonal grid. Secondly it means that if you are flying downwind and come to the end of your cloud street, then you should not continue to fly directly downwind to find lift. The theory suggest that you should turn 60 degrees away from your downwind flight path and fly cross wind for approximately 6 km where you should find the beginning of the next cloud street, if all is going according to theory.
The hexagon theory also explains why you get “blue holes”. These are simply the middle of the hexagons. I used to think that if you flew into an area of blue sky where the sun was heating the ground strongly then you would inevitably be rewarded with a nice thermal. I soon found out that this idea did not work well and I ended up too many times on the ground looking downwind at amazing skies due to landing early. The hexagon theory says that the air is flowing downwards in these blue holes and so even though the sun is heating the ground it cannot overcome the downward flow of the air.
It is important to understand that the hexagon theory should only be applied over flatlands. Mountains are such strong thermal sources that they destroy the application of the theory, but what I find interesting is that it explains why some thermal sources may work and why others may not. If you have two thermal sources of the same strength, then the one that lines up with the hexagon pattern is going to be the one that works and the one in the blue hole will not work, even though it looks so great.