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At this time, a new written test is being polished for Advanced and Intermediate Ratings (Hang 4 & 3). You can count on the fact that it will include questions relating to the gradient.
I think that the fourth paragraph is not very clear. It talks about flaring. The point is that the gradient can tend to cause the flare to be stronger than intended, because the nose of the glider is up in stronger wind. By running a few steps, the student won't have the nose so high. (End of author's note)
The effects of wind gradients probably injure more hang glider pilots than stalls do, yet they are rarely mentioned. Wind gradients and their effects are fairly simple to understand. This article is a brief introduction and will provide a few suggestions for techniques that can help avoid wind gradient-induced problems in flight.
Any sailor will tell you that boats with taller masts hold an advantage over boats with relatively shorter masts. The reason is that they can carry their sails higher where the winds blow stronger. Winds blow stronger where the tall masts reach because the winds are not slowed as much by friction with the earth's surface. A wind gradient is the speed differential along a line across the wind, in this case a vertical line (see figure 1: Schematic representation of a Wind Gradient). When pilots speak of the wind gradient, they are talking about the gradient near the earth's surface caused by friction. If there is any wind, the wind gradient will be present. The more quickly the wind increases with altitude, the stronger is considered the gradient.
Picture a training site. Ideally, it will have about a ten mph breeze with smooth, stable air. It may be surprising, but stable air tends to have a stronger gradient than unstable air. Nice, stable marine air coming onto a beach will invariably have a relatively strong gradient. The reason for this is that unlike unstable air which rolls around and around exchanging momentum within itself, stable air slides over itself and, near the surface, is left alone by the stronger winds aloft.
A student hang glider pilot first encounters the effects of the wind gradient during overly aggressive flares for landings. In first flights at good training sites, the student remains near the ground during the glide. Then, in a strong flare, he sticks the nose of the glider up even farther, sometimes enough so that the glider slides backwards to the ground, perhaps damaging the keel. For this reason it might be wise for instructors to advise the students to try to run a few steps on landing.
Once a student is making flights with altitudes of 30 or 40 feet, he will encounter the best-known effect of the gradient (see figure 2). As the glider descends down through the gradient, airspeed will tend to diminish. In order to maintain airspeed, a pitch stable glider will want to descend more rapidly. The student will counter by easing the nose up, causing the airspeed to drop off. This won't be readily apparent to the student because his groundspeed will remain the same or increase. The result is often a hard mushing landing or even a stall and a bent control bar. The answer is, of course, to carry extra airspeed on final approach. But, the question is: how much extra airspeed? In a nice smooth and large landing area it is difficult to come in with too much, but not all areas allow such liberties. Other things being equal, more airspeed would be advised in more stable air, but other things are not equal. In bumpy, unstable air, a little extra airspeed is advisable for control and to make passage through rolling air quicker. A rule of thumb often heard is to add half the windspeed to your airspeed. The point to remember is that smooth air shouldn't lull you into trouble. Stable winds have the stronger gradient.
So far, we have considered the effects of the gradient in straight and level flight or in a flare straight into the wind. Things get a little more complicated when we introduce the factor of turns in a gradient. Furthermore, in this case, lack of understanding of the effects of the gradient can be more serious and can lead to accidents quite capable of injuring the pilot. Indeed, it is here that we enter into situations that really have hurt a lot of pilots in hang gliding and continue to injure many because some instructors fail to properly explain the situation. It almost goes without saying that those who try to learn by themselves, without the benefit of proper instruction, will almost certainly encounter some hard knocks from mysterious crashes that they attribute to "tip" stalls.
Suppose you are flying crosswind as part of your landing approach. Your intention is to turn into the wind and land when you get down to an altitude of 15 or 20 feet. When you attempt to bank into the turn, the glider will tend to resist the banking and, unless you have anticipated, the turn will overshoot the line you intended to follow to your landing. That's not too great a problem unless there happens to be a tree or power line in the way. Secondarily, as you go around the turn, you must start off applying a great deal of control effort, but as you turn into the wind this effort can put you into too steep a bank and even, perhaps, turn you into a crosswind or cross-downwind heading. The reason for the over control is that the gradient does not affect your banking capability when heading into the wind ... it is just the crosswind portions of turns where the gradient affects the banking.
Now, imagine a turn away from the direction which is into the wind. This is frequently seen in spot landing contests. A glider approaches to one side of the spot and the pilot starts a turn which will give him a crosswind track to the spot. Often the glider flicks around in a steep downwind turn and ends up in either a downwind landing or crash. What happens is that the high wing tends to blow over the low wing causing a steep turn. This "blowing over" of the high wing can be very strong; stronger than is controllable when coming as a surprise. It is hard to over-emphasize the rapidity and power of this effect. The best advice is to never turn out of the wind near the ground unless it is really necessary and keep in mind that the glider will want to turn very quickly and sharply.
These last four paragraphs indicate that when flying in the wind gradient a glider will want to turn downwind and stay flying downwind. When entering a 360' turn from a direction into the wind, the glider will snap right into a nice tight turn until pointing downwind. At that point, however, it will start to want to roll out of the turn and stay flying almost downwind and the pilot will have to apply much more control to maintain a constant turning rate. The slow turning portion of the 360 occurs closest to the hill when the pilot suddenly wants to get around the turn.
A few years ago a large aviation magazine printed an article by two pilots, one a crop duster and the other an airline pilot. The article was over the argument (as old as aviation) about downwind turns. The crop duster argued that the downwind turn was dangerous because you tended to lose airspeed, whereas the airline pilot argued, correctly, that there is no difference in a turn due to the wind. The crop duster was basing his argument on experience. He just knew that the downwind turn was bad news. Unfortunately, he laid the source of this very real experience at the doorstep of the wind. The fact is that his experience was at very low attitudes, where he was in the gradient. It was the gradient, not the wind itself, that was causing him to think downwind turns are different. They are different if you are in the gradient, but not if you are above the gradient.
As pointed out, a turn is affected by the gradient because the high wing is in stronger wind and is blown downwind more strongly. This is the same as saying that the wing which is further from the ground is blown more strongly downwind. The fact is that you can be in straight and level flight, yet your wings can still be across the wind gradient, just as if you were banked in a turn. This situation exists when flying or soaring near to or along a ridge or slope and the ground is banked, instead of the glider (see figure 4: Wind Gradient along a slope).
All pilots who have soared along a ridge have noticed that they have to apply a banking force away from the nearby ridge. This tends to be a steady state thing and hasn't caused too much trouble except in gusts. When a gust hits, the effect of the gradient up the slope will intensify and act to roll the glider into the hill. Pilots have died because of this. They scratch along the edge of a steep ridge and a gust hits them, blowing them towards the lip. As they try to turn away, into the wind, the gradient is lifting their windward wing making the turn slow or impossible or, even, causing them to turn towards the cliff.
A more common accident with neophyte ridge or slope-soaring pilots occurs when they turn. Sometimes this turn is the first turn away from into the wind to fly along the ridge. They don't realize how tough it is going to be to stop the turn, so they allow the turn to go too far and they hook a wingtip. Just as often, an accident occurs when the pilot turns to go back down the slope in the other direction. When he starts the turn, he is turning into the wind and he needs aggressive control application. However, as soon as he has turned across the wind, the glider will want to turn and can catch him by surprise. He turns too far and again ends up by hooking a wingtip and cartwheeling into the ground. This can be very pronounced as both the glider and the ground are banked.
There can be no clear cut rule for handling the gradient in turns and along slopes. My own suggestion is to initiate the roll out of the turn as soon as the glider is pointed into the wind. If you end up recovering from the turn too soon, it is easily dealt with, but if you allow a turn in these conditions to go too far, the result can be serious. Be wary of any downwind turn if you suspect a gradient may exist and, if you must turn, just sort of nibble at it so that the turn doesn't get out of hand. Above all, think the whole concept of the gradient over and over in your mind so that you will reduce the chances of being caught by surprise.
When the hang rating tasks were designed, figure eight patterns were included. One thing about them is that they tend to introduce wind gradient factors.
SOAR (sor, sor) v. To rise, fly upward or glide high in the air.
Soaring: Mankind's age-old dream. Sooner or later most hang glider pilots get around to it. But how difficult is it, really? What should I know before I try it?
In order to simplify things, I'm going to assume you have a glider and the necessary skills to begin soaring.
So, now, let's move on to the three problem areas as I see them. They are: conditions, desirable skills, and traffic.
Let's start with conditions. How do we define "soarable" conditions? Soarable conditions exist when there is air rising which equals or exceeds the sink rate of your glider.
Obviously, we can experience a wide range of conditions which enable us to soar. If the rising air merely equals our sink rate, it is considered a marginal soaring day. You will only be able to maintain, not gain, altitude. On a day where the air rising exceeds our sink rate by a large margin (but not so much as to make flying unsafe, i.e., wind too strong to safely penetrate), soaring becomes much easier.
What factors determine the amount of lift available at a given point in time? In a ridge soaring situation, it's the size and shape of the hill, direction and strength of the wind and the lapse rate (stability factor) of the air.
How about turbulence? I've heard sometimes ridge lift can be quite rowdy?
A very good point. Ridge lift can be glassy smooth to bone rattling. The most common factors contributing to this turbulence are gustiness and the presence of thermals.
Okay, I now have a basic understanding of some of the factors involved in ridge soaring conditions. How do I know when it is safe for me to make that first soaring flight?
Safe first-time soaring conditions vary greatly from site to site. So, the best way to determine the conditions is to ask. Most every site has advanced pilots around who know the conditions intimately. Seek out the advanced pilots who have a conservative attitude toward flying and tell them exactly how much experience you've had. Remember, it's better to understate your abilities somewhat rather then overstate them.
With conditions for safe soaring flight out of the way, let's move on to area two: desirable flying skills. Notice I used the word "desirable" instead of "necessary." In this sport, the more you know (and put into practice), the safer you'll be. So, let's take a look at the skills desirable before we attempt soaring. I'll explain why as we cover them.
D.S. (Desirable Skill) -1: Proficiency in launching into stronger winds. Launching into stronger winds is learned gradually, progressively. You shouldn't try to go from a gentle 5 mph training breeze to a very soarable 20 mph. It's a good way to learn your first ground loop.
D.S. -2: Ability to turn your glider smoothly and efficiently in both directions. If you do wide, diving turns, you'll be out of the lift in no time.
D.S. -3: Experience in downwind flight. For most of us, the first time we fly downwind in any good breeze, we get a little frightened. A lot of us stall and fall on that first downwind flight. Why? Because we mistake groundspeed for airspeed. Remember, when you fly into the wind, airspeed minus windspeed gives groundspeed. When you fly downwind, the opposite is true: Airspeed plus windspeed equals groundspeed.
Thus, if our airspeed is 20 mph and we fly directly into a 10 mph headwind, our groundspeed is 10 mph. Now do a 180 degree turn and fly downwind. What's your groundspeed now? Right: 30 mph. The natural tendency is to look at the ground rushing by and think, "Wow! I'm flying way too fast! I'd better slow down." Wrong: You just hit the hill in a downwind stall.
D.S. -4: Experience in stalls and recovery. This means the upwind, downwind and tip stall variety. Your instructor should coach you through these. A very common mistake for new soaring pilots to make is to keep slowing down in the lift until they stall. If you've never stalled your glider before, you're in for a rude surprise. You'll have little or no control and you will possibly spin into the hill. Why? Because you didn't know what it was or how to recover.
All right. We've covered the basic conditions and skills for soaring flight. What's left? You guessed it: TRAFFIC.
How do you cope with the crowded skies? There has been a rash of mid-air collisions lately. Why? Two reasons: pilots not flying according to international soaring rules and not flying defensively.
Remember the very first time you drove a car on a crowded freeway? People that you didn't know or trust were zooming by you at breakneck speeds. Yet you lived through the experience because everybody was supposed to follow certain traffic rules. As long as everyone followed those rules, you didn't get into accidents. Simple.
Now, for some reason or another, some of these same people who drive safely learn to fly a hang glider and go gonzo. I don't know why, exactly; it just happens.
So, to increase our chances of survival, we (USHGA, pilots in general) have adopted the International Soaring Rules. They are very easy to remember, and they make sense. They are as follows:
1. Never fly directly above or below another glider.
2. Make all reversing turns away from the ridge.
3. When overtaking another glider from behind, the overtaking glider yields.
4. Gliders approaching head-on both yield to the right.
5. Higher altitude glider yields to lower one.
6. When entering a thermal, circle in the direction established by the glider(s) already in the thermal.
In order to have a better understanding of these rules, let me write a sentence or two explaining them.
#1 should be fairly obvious. We never know when we will get some unexpected lift or sink.
#2 is to establish a norm for turns. If you allowed both inside and outside turns on the ridge, the person behind you wouldn't know where to go.
#3 means that it's up to the overtaking glider to get out of the lead glider's way. This is accomplished in one of two ways. Either you reverse direction before he does, or pass on the ridge side of his glider.
#4 is very critical. Everyone must do the same thing in this situation. Once, years ago, I was soaring with a crowd at Funston. As I approached another pilot head-on, I started my yielding turn to the right. The other pilot hesitated for a moment, then quickly turned to his left. I dived to miss him. He realized at the same moment I started to pull in that he make a mistake and pulled in to miss me. I pushed out and missed his kingpost by three inches. Later, when I spoke to him on the ground, I asked why he had turned left. He said that he turned better to the left, so he thought he could get out of my way faster. Very scary.
#5 is, again, obvious. When you're higher, you have more options available.
#6: It's almost impossible to thermal safely if everyone is going helter-skelter. Even if you're 3,000 feet above the pilot who found the thermal, turn in his direction. Often, in this situation, the lower man is in a stronger portion of the lift and can rapidly catch up to you. Remember Rule #5: Low man has the right-of-way.
And, a last one which isn't on the list, but should be, is: CLEAR YOUR TURNS. I mention this last and in capital letters because everyone is guilty of it sooner or later. This is just a good part of flying defensively.
To close, let me summarize what's been discussed. We have gone over the basic requirements for safe soaring flight, which are conditions, desirable skills and traffic. Ideally, I hope I have provided enough material to clarify the events leading up to your first soaring flight.
If there is something you don't understand about what's been covered or if I've raised a question in your mind which I didn't answer, it's your responsibility to find out. Good pilots learn by reading, flying, talking to other pilots and studying nature.
Most "explanations" of flight take you into an intellectual land filled with Bernoulli, vector diagrams, and elegant equations. This may be a garden for designers, but it is a swamp for pilots. Have you ever heard a pilot in trouble call out for Bernoulli or offer up a final expletive of "p - !,- pV' = H" just before the crunch?
Exhaustive research in the field has shown that the pilot's most frequent final words are "Oh shit!" It has been assumed by these researchers that pilots are simply an uncouth crew of semi-literates. However, independent research has brought out the fact that the expletive refers to the pilot's opinion of a theory of flight which he has discovered too late and is useless in crisis. Elegant theories of flight, laced with impressive differential equations, are not the stuff from which a clear mental picture of controlling flight is drawn:-they are the tools of designers, not pilots. These quantitative theories are generically classed as the "Oh shit" group. Pilots should learn useful concepts from a qualitative group, sometimes referred to as the "Made it again" group of explanations. We must never confuse theory, no matter how hoary from repetition, with explanation.
All of us have read countless books and articles describing the airflow over and under a wing or airfoil. The stall is defined as the point, or angle of attack, at which the airflow separates and dissolves into a mess of eddies. That's true enough, but the writers spoil it by then announcing that most of the lift is lost because the top surface is the major source of lift - yet they fail to speak of the role of drag. And this failing is where they lead us down the paths of pain.
The fact is, assuming a constant airspeed, not that much lift is lost as you stall. The loss amounts to something like 20 or 30%. That loss could be compensated for by an increase in airspeed of only about 15% or something like three miles per hour in an ordinary hang glider. Of course, the problem is getting that three miles per hour! This brings us to the sin of not emphasizing the role that drag plays in a stall. It is the increase of drag, not the decrease of lift, that can bring worry lines to the face of a pilot. But first, the Law of Stalls:
The study of the role of drag during a stall is the Rosetta Stone (means of discovery) of these laws.
Suppose your glider had two instruments which showed its lift and drag characteristics. Suppose that each instrument read half scale - say fifty on a scale of 0-100 - at an airspeed which gave minimum sink performance. Now, suppose you slowed up a little, so that a stall resulted. The lift indicator would drop a little to around 35 or 40, but the drag indicator would go right off the top of its scale. The clear result would be that you would have to increase your rate of descent drastically to maintain what airspeed and lift you have remaining. If the glider is not allowed to drop to compensate for this huge increase in drag, the airspeed will be jerked right out from under you and, then, lift will be reduced sharply and you will fall out of the sky. But keep in mind that the original culprit is the increase of drag. An explanation of the three Laws of Stalls is now in order.
When you expect a stall, you react as soon as it occurs. You get the nose down a little and immediately, so that you don't lose much more airspeed and what little is lost is quickly regained. But if the stall comes as a surprise, you will react late in the game and you may try to maintain altitude for a brief period, forcing the nose even higher. This allows drag, the time needed to suck away your airspeed. insuring the necessity of a longer recovery period. Even worse. the chances are that one wing will precede the other into the stalled condition. The much greater drag will tend to pivot the glider around, which will reduce the wing's airspeed and lift relative to the other wing. This, of course, is the start of a spin or a rolling crunch into the ground. The proof of this pudding lies in the fact that, regardless of aircraft type, very few practice stalls - they are not surprises - result in spins, whereas most accidental stalls result in a wing dropping out. All this is to emphasize the First Law: The severity of a stall is proportional to surprise.
The Second Law should be obvious. Air causes no pain. The ground does. And the awkwardness with which you hit the ground can contribute to how hard you hit it.
The Third Law should be simple. If something will hurt, you won't want to do it. The only intentional stall you'll be likely to do when near the ground is during the landing. But if your mind is on the crowd, winning the spot landing contest, trying to get rid of altitude with low S turns, or hanging on to altitude to clear some wires, then the stall can sneak up on you and be a painful surprise in its severity. Now let's get into flying.
Consider a pilot who thinks himself advanced. He decides to soar the face of a hill where he sees Henry Hotshoes staying up. Our hero's glider is known to be mellow and he has practiced stalls a number of times. He makes a few passes back and forth along the hill and finds himself right up there with Henry. He vows that now is the time to show that he can stay up there with the "experts." He slows up a little more, milking the lift. He finds himself a little above and behind Henry and is really pleased with himself. He thinks, "how great this is;" how he is a born bird. He loses a little altitude, and without thinking, pushes out a little more. Without any apparent warning his mellow glider starts to roll into the hill and to drop its nose. His momentary response, being caught by surprise, is to push out and try to turn away from the hill. The glider just falls off into the hill and he wakes up in traction.
Our hero was the victim of thinking that practicing intentional stalls would prepare him for accidental stalls. He was not prepared for this stall, so he failed to do the only thing that will correct for a stall - get the nose down immediately and sharply, before drag takes its toll of remaining airspeed and lift.
Now let's relate an actual accidental stall at a bad time - during a tight turn near the ground. A national champion hang glider pilot was competing at the Dog Mountain Nationals. He was doing a series of figure eights over some pylons downwind of the landing area and he was getting very low. He had a chance at the contest if he could crank out one more turn around the pylons, so he turned towards them, away from the landing area, for one last pass. He suddenly realized that he was getting too low and would have to get back or he'd land short. He turned abruptly and stalled the glider at an altitude of about 40 feet. He realized his error and momentarily pulled forward. He lost about 15 feet of altitude and came up short of the landing area.
The point is that, with everything riding on not losing altitude, he still allowed his conditional reflex to cause himself to pull in at the first sign of stall. If he had hesitated at all, he would have piled right in and would have been hurt. That conditioned reflex is what every pilot has to acquire. There is only one way to acquire this reflex and it is not to go up and practice intentional stalls. They will help to teach you that a well-designed glider will recover, but that is about all they do for you.
The way to learn about stalls is to practice not stalling; seeing just how close you can come to them without stalling. This is, of course, called "slow flight." The first step is to pick a nice large smooth landing area. Then make a fast approach and try to keep the glider about 6 feet above the ground and pay attention to the feel of the glider just before it lets you down. Then follow this exercise at an altitude of at least a few hundred feet. Try to not let the glider stall - just to see how close you can come to the stall. If you do it right, you will stall sometimes. When you do stall, pop the nose down a little just as soon as you realize what's happening. Pretty soon, you will seldom really stall and you will gain a feel for things when they are slow and sticky.
Then, the next step is to do the same things in gentle turns, then steeper turns. Always practice this slow flight away from the hard ground and only in a well-designed modern hang glider. After a few hundred "accidental" partial stalls out of slow flight, you will be ready to take on Henry Hotshoes. And you will be a far better pilot than those who spend their time flailing around the sky impressing all those who have yet to recognize precision flying when they see it.
Over the years, I have observed the problem of pilots taking off not having hooked into their gliders. I've also read about and seen the tragic results. Some pilots have gotten away lucky; most have not.
Since I believe that the only person responsible for my personal safety is myself, I've developed habits to insure that I won't make such a careless error. Wire assistants, launch assistants and my friends can never be to blame if I am forgetful. I must take the full responsibility. You must, too.
Just doing a hang check is not enough. Don't get me wrong, a hang check is a very important step that should be done prior to every launch. A hang check shows the pilot that he/she is hooked in and is the correct height above the bar. It also assures the pilot that harness lines and straps are untangled.
The point I'm trying to make is that every pilot should make a second check to be very certain of this integral part of every flight. In many flying situations a hang check is performed and then is followed by a time interval prior to actual launch. In this time interval the pilot may unconsciously unhook to adjust or check something and then forget to hook in again. This has happened many times!
If, just before committing to a launch, a second check is done every time and this is made a habit, this tragic mistake could be eliminated. Habit is the key word here. This practice must be subconscious on the part of the pilot. As we know, there are many things on the pilot's mind before launch. Especially in a competition or if conditions are radical the flyer may be thinking about so many other things that something as simple as remembering to hook in is forgotten. Relying on memory won't work as well as a deeply ingrained subconscious habit.
In the new USHGA rating system, for each flight of each task "the pilot must demonstrate a method of establishing that he/she is hooked in, just prior to launch." The purpose here is obvious. It is left up to the pilot to demonstrate whatever method works best for him. Here are some suggested methods:
Upon looking for a topic for this month's installment of Hang Gliding 101, I figured that there were two very important topics that needed to be covered at some point in the series, and now seemed as good a time as any to cover one of the two. Those topics are launching and landing.
The most dangerous things you can do in a hang glider (short of aerial photography of Sean Penn and Madonna) are launching and landing. We all know that with proper instruction, flying a hang glider is a very simple thing that almost anyone can accomplish with some proficiency. Launching and landing, however, is a whole 'nuther thing completely. They are not passive acts. They are precision maneuvers that require expertise gained from proper instruction. This article will contain lots of important tips on what to do and what not to do concerning launching a hang glider. Next month's article will deal with landing.
As I've said before (and undoubtedly will say again), these instructional columns are meant to be used in conjunction with a good training program that can only be obtained at a good hang gliding school. Do not use this information to teach yourself how to hang glide. USING THIS INFORMATION WITHOUT AN INSTRUCTOR CAN KILL YOU. For a certified school in your area, look in the back of this magazine or in the yellow pages.
One of the significant differences between hang gliding and most other forms of aviation is the fact that hang glider pilots launch and land on their feet, as opposed to wheels. In fact, if you think about it, that's one of the many things that makes hang gliding flights much like the flight of birds. Very seldom do you see birds screw up their launches and landings. That's where we differ greatly from our feathered friends.
A trip to the LZ of any local flying site will prove to you that we don't spend enough time working on our landing technique. A trip to launch will show us the same about launching. Luckily, launching is inherently more forgiving than landing simply because you usually have a certain amount of vertical area in front of the launch in which to recover from your bad form. That doesn't mean that it's acceptable to have bad launch form, it just means that it's usually survivable.
There are many areas in the East, and a few in the rest of the country, where almost any mistake you make in pitch during launch will be forgiven, because of the 300-500 feet of vertical nothing you have in which to allow the glider to recover from your screw-up. For much of the remainder of the sites, and especially out west, you find lots fewer forgiving launches. Launches that have shrubs and trees close below them, and launches that are very flat with very little slope to run on are just a couple of the "less forgiving" kinds of launches. For these and other reasons (including the fact that we just don't want to look like geeks), we're gonna work on our launch form.
Constants are thing you always figure into any given situation or equation. They're always a factor. The two constants when launching a hang glider are: wings level and evenly loaded. Let's take a moment and analyze these.
First, wings level. You definitely want to launch your glider with the wings level. Launching with one wing higher than the other will put the glider into an instant turn that now has to be compensated for just to keep from contacting the hill you've just attempted to leave. Always launch straight off the hill and don't start to turn the glider until you have ample clearance from the terrain. The only exception to this rule would be for dune soaring, and that should only be learned under the guidance of a dune-soaring instructor.
Second, wings evenly loaded. Having both wings evenly loaded simply means that both wings have the same amount of upward force (created by the wind) on them. A good way to think of wing loading is in pounds. If one wing seems to be pulling up with about 10 pounds of pressure, then you want the other wing to pull up at about 10 pounds as well. Even if each wing has 100 pounds of pressure, the most important thing is that both wings be loaded equally. Launching with the wings unequally loaded will produce an instant turn which will result in the same scenario that resulted from launching with the wings not level.
These two constants, no matter what other variables are involved, always stay the same. Now, armed with that knowledge, let's tackle the variables.
THE BIG PICTURE
Launching is nowhere near as difficult as some pilots make it look. Being smooth and deliberate will make launching much easier. The pilots you see being really forceful, jerky and generally non-focused on launch are by and large the ones you see having the most questionable and shaky looking launches. There are only three major things that you need to focus on during your launch (outside of the constants). They are, in this order: relax, angle of attack, and acceleration. That's all. It's really pretty simple and with practice, you too can soon be having confident, consistently primo launches.
Relaxation is something lots of us have a problem with in life in general. Some of my better friends have "type A" personalities which don't allow for kickin' back and just smelling the roses on occasion. All aspects of hang gliding should be approached in a relaxed mode and launching is no different. The hang glider is constantly trying to talk to you and when it talks, it talks through the control bar. But since it doesn't talk verbally, you can't listen with your ears. Your hands are your ears. If you have a light, relaxed grip on the control frame you'll be able to hear the glider loud and clear. If you have a death grip and are trying to squeeze water out of the downtubes, then you'll be muffling the glider's main means of communication with you. Relax your entire body and use a gentle, light grip to control the glider--from the time you're standing at launch until you're standing in the landing zone. The more you relax, the more you'll enjoy hang gliding in general.
ANGLE OF ATTACK
What is angle of attack? It's the angle at which the glider "attacks" the relative wind. If the wind is horizontal, we can relate the angle of attack to the general "attitude" of the nose of the glider. If the nose of the glider is pointed high toward the sky, then we have a "high" angle of attack. And likewise, if the nose is pointed low toward the ground, then we have a "low" angle of attack (see figure 1). If the keel of the glider is basically parallel to the relative wind, then you have a neutral angle of attack.
Our intent at launch is to start out with the proper angle of attack and maintain that angle all the way through the complete launch sequence. The old school taught us to hold the nose of the glider at a low angle of attack to build up groundspeed and then increase the angle of attack, by raising the nose, to produce more lift and get us airborne. Starting with and maintaining the proper angle of attack is in my opinion a more consistent means of producing a good launch. (If your instructor disagrees with this then use his method.)
So what's the proper angle of attack? The proper angle of attack is approximately 10-15 degrees nose high from parallel to the relative wind (figure 2). Keep in mind that the angle of attack is compared to the relative wind and not compared to the horizon or the terrain. The relative wind will change in relation to the terrain that it is striking (figure 3) and you must adjust the glider accordingly.
Okay, so now you've got yourself all relaxed up and the angle of attack is where it should be. To get the glider into the air you have to accelerate it to flying speed while keeping the appropriate angle of attack. To get a glider to support its own weight takes roughly 7 mph of airspeed. If the wind is already blowing 5 mph then only 2 mph of forward groundspeed (coupled with the proper angle of attack), will have that sucker off your shoulders and beginning to tug at your harness straps. To get to this point you've got to get the glider moving.
While you're still supporting the glider's weight (on your shoulders and with your arms) you have to start the acceleration by using your shoulders and upper arms. Be careful at this point to gradually accelerate. A common error is a "jackrabbit" start. Since your body, including the shoulders, is positioned below the glider's center of gravity, if you do a sudden acceleration it will naturally tend to make the nose of the glider pitch up. For this reason start with a "momentum" step, which will gently start the forward movement of the glider, and then quickly accelerate to flying speed.
So you've started your acceleration by pushing with your upper body on the downtubes, and the glider has lifted off your shoulders and is carrying its own weight, but it is not yet lifting you off the ground. It's important at this point to continue the acceleration without hesitation. Since you can no longer push with your shoulders, continue to pick up speed, accelerating the glider through the pull of the harness on the hang strap. Use your hands on the downtubes to lightly adjust the pitch as needed to maintain the proper angle of attack. As you accelerate through flying speed the glider will lift you off the hill and into the air, where you should increase flying speed slightly to give plenty of maneuvering speed as you move away from the hill.
There are some variables on launch that we should consider. One such variable is the case in which the wind is blowing 10 mph or more. Keep in mind that I mentioned it only takes approximately 7 mph of airspeed to get the glider to support its own weight. If the wind's blowing 10 mph, then the glider is already wanting to be off your shoulders and carrying its own weight. What do you do about it? Nothing! Don't fight it. If you're standing on launch, and the wind is blowing with sufficient velocity to make the glider want to rise up off your shoulders, then let it. Actually, you're one step ahead of the game in this case. The glider will be pulling up on your harness through the hang strap and now you will only have to accelerate the glider through the hang strap (by running), and maintain the proper angle of attack to get airborne.
Another variable is windy cliff launching. Anytime there is wind blowing up the face of the cliff it will try to be more parallel with the face of the cliff than with the horizon. Because of this you will inherently be launching with a higher than normal angle of attack. The actual angle of the keel compared to the horizon may be low, but the angle as compared to the relative wind will be high. It is especially important to have good pitch control on this type of launch. "Popping" the nose or allowing for a too-high angle of attack can be deadly.
Another variable associated with windy cliff launching is "ramp suck." While this may sound intriguing to some twisted minds, ramp suck can be very frightening. This phenomenon is created during cliff launch by wind that is striking the front of the glider (at a very high angle of attack) and "rotors" over the top of the wing and back under the trailing edge. This makes it feel as though someone is pushing up on the keel at the rear of the glider (figure 4). The best way to handle ramp suck is to get as far out into the wind flow as possible. This is a very unnerving thing to do, but it will help to equalize the pitch pressures somewhat. Try not to fight ramp suck. Just have a wire person on the rear wires of your glider for safety, in case a strong gust should come through and make it too much to handle. I hope it goes without saying that side-wire assistance is needed in conditions such as these. Do not attempt this type of launch until you have "regular" launching figured out. Ask your instructor.
So, the three main things to keep in mind when it comes to launching (along with the wings level and equally loaded constants) are: relax, proper angle of attack and acceleration. That's all. Pretty simple.
As an instructor I try not to overload the student with too many things to think about, but simply lay down the basics on which to build. Your instructor will be able to fine tune these basics to fit your individual needs. If any of this advice directly disagrees with what your instructor is teaching you, then go with his or her advice. Only your instructor knows your personal training deficiencies and strong points. If you have any questions I can always be reached at (619) 450-9008.
Man has dreamed for thousands of years of doing what you now can do--give thanks.