This week”s #tbt stands for “throw back Thursday” AND “truth be told”. This article, written almost 20 years ago by the visionary John LeBlanc, is still so relevant today that it”s mind boggling. A lot has changed in the sport…yet many things remain the same.

“Wing Loading and High Performance” 
by John LeBlanc

The article in the August 1995 edition of Parachutist

Canopy control today is a lot different than it used to be. Heavier jumpers under smaller canopies are filling the skies with zippy parachutes that are extremely sensitive to toggle input—especially on landing. The modern, high-performance parachute is one of the most agile flying machines in existence, capable of incredible flight speeds and directions. At high wing loadings, however, your survival is no longer guaranteed just because the nylon over your head is open and flying. Getting safely to the ground becomes more complicated at higher wing loadings, even with all the improvements in technology. Any freedom has its price, and the decision on what wing loading to fly is no exception. This article discusses wing loading and why so many people, whether wisely or not, are choosing to go to a higher wing loading. We”ll also discuss the specific changes in flight characteristics that occur and some of the performance limitations that high wing loading can create and how to reduce the effects of those limitations. Like it or not, these characteristics have created a new and different skydiving environment, so we may need to rethink our ideas about safe canopy flying if we are to avoid accidents.

What Has Changed, and Why

After more than ten years of being totally consumed with working in the design, testing and flying of parachutes, four general ideas come to mind about what has changed since I began jumping in the “70s:

First, the advances in parachute aerodynamics have dramatically improved landing characteristics of most modern parachutes. Jumpers haven”t been satisfied with merely getting better landings at the same flight speeds of the “70s, though. Skydivers have always been the type of people who try to push the limits. The improved landing aerodynamics have given these jumpers new ways to test their limits by jumping smaller parachutes, and these canopies fly and descend at speeds that, just a few years ago, would have never been considered laudable. At the novice or intermediate level, jumpers are often encouraged to transition to canopies that may seem large by today”s standards, but are actually smaller and faster than the “hottest” ram-airs used only a few years ago by the most experienced jumpers on the cutting edge. Sure, they seem quite docile to the expert of today, but perhaps we have forgotten that these canopies are still as fast and just as “hot” as when they were first put on the market.

Third, it has become easy to fall into the trap of thinking that a student or novice has grasped the basics of canopy control simply because he is observed to land softly every time so far. This is often used to establish a student”s readiness for a smaller canopy, but isn”t there more to it? With the improvements in aerodynamics, isn”t it likely that a student will land a modem student canopy very softly even though he is making mistakes in the basics of canopy control?

Doesn”t it make sense that the mistakes that go unnoticed under a large canopy are compounded under a smaller, less forgiving canopy, with dangerous results? There is more to flying fast parachutes than simply landing softly in a big open field.

When larger canopies were the norm years ago, it was much easier for an expert, to keep track of the canopy control environment. Most experts in the sky easily stayed well within their own limits at the slower speeds of the older, larger canopies. It was easy to watch out for the beginners. But today, experts can obtain very small, high-speed canopies capable of flying at speeds and in directions that were impossible a few years ago. The additional speed and maneuverability means that today”s skydiver is faced with much more demanding piloting tasks that require much more concentration, attention and skill than even the “experts” may have! This means that we are all much more likely to find ourselves surrounded by a high concentration of jumpers flying at or beyond their skills envelope threshold, even if they are highly experienced freefallers. Now, tie these four factors together and what do we have? The accident reports answer that question. Perhaps we need to collectively change our attitudes and beliefs about what constitutes acceptable canopy control. No, the answer isn”t banning small canopies or swoop landings, but rather changing how we decide under what conditions they are acceptably safe. Part of the solution to reducing the danger to a more acceptable level may be to go back to the basics, some of which were covered last month (“How to Fly “Em,” July). [We”ve got something special for the person who tracks down this edition of Parachutist! 😉 Email us if you find it.]

Another part may also be to seek greater understanding of the changes that are created by going to a higher wing loading. Wing Loading Defined: Wing loading is the ratio of how much weight is carried by how much parachute. To calculate wing loading, simply take the total exit weight (including the main, reserve and container), then divide this figure by the area of the canopy. It is expressed in pounds per square foot. You need to include the weight of the main canopy because it must also support its own weight as well. The typical student might use a wing loading of 0.5 to 0.6 pounds per square foot, while up to 1.0 lbs./sq. ft. is usually considered reasonable for the more experienced jumper. Though not necessarily required, some people go to an even higher wing loading, especially on the newer zero-porosity canopies. But what”s the point of higher wing loading? Usually it”s one of six reasons:

1. We skydive for fun! The extra speed under canopy generated by increased wing loading can add to that fun. The extra thrill and challenge of going faster than you are accustomed to can be quite intoxicating.

2. More nimble handling and crisp response also adds to the sport”s enjoyment. Small movements of the controls produce notable changes in the flight path that would not be very noticeable at lower wing loadings. This may help you control the canopy more precisely, but it could be a double-edged sword. The canopy doesn”t care if your control input is correct or not!

3. You may want a tiny rig like the one your friend has! Everybody gets the itch for a new toy once in a while, but remember, it must serve an important function: It should save your life and return your body unharmed to the ground.

4. You may think a certain size is needed to achieve the proper wing loading. But what exactly is the right wing loading? There is some confusion here. The maximum recommended weight limit is often misinterpreted to mean a required weight, or even a minimum weight. Usually it is neither. The canopy chart published last month (“1995 Canopy Buyer”s Guide,” July, pg. 43) shows minimum weights for most canopies, and they are frequently much lower than most people would expect, especially for the high-performance canopies. The wing loading you choose is a personal choice. If you feel a certain canopy might be a bit over your head in a tight situation, consider going one size bigger—or two. You”ll still get great performance and landings if the canopy is a good design, but at a slightly slower speed.

5. Long swooping landings are fun! The ability to achieve zero descent rate during the flaring process is what permits landing without injury at higher than normal wing loadings. But don”t forget that the refined aerodynamics that give more effective flare characteristics do not automatically provide good landings, only the potential for one. As wing loading goes up, there is less forgiveness.

6. A higher wing loading can help you avoid backing up in winds. Backing up toward the trees and power lines is no fun, and the higher speeds of a smaller canopy can help. But this is often taken too far. High winds often mean heavy tur-bulence, which increase the chances of canopy collapse. The increased ability to penetrate headwinds may give you a false sense of security in winds that should probably be waited out on the ground.

What is “High” Wing Loading?

These six reasons for going to a higher wing loading are all valid but can obviously be taken too far, possibly with dangerous results. What is the best wing loading? Sorry, but this question involves trade-offs that make a definite answer impossible. A number used to specifically define what is a high wing loading and what is a low wing loading can”t be broken out for two reasons: First, different canopies are more capable of safe flight and landings at certain wing loadings than others. For example, if a jumper whose exit weight is 170 pounds finds that the Sabre 150 flies and lands the way he wants, he should be careful to not assume he is capable of safe flight on all 150-square foot parachutes. He might be very surprised to find that the PD-150 made from low porosity F-111 fabric might actually be tricky to land softly and require an unusual approach technique for a reasonable landing, if it”s possible at all.

Secondly, people always judge a canopy”s flight characteristics according to their own individual frame of reference, which varies greatly from one person to the next. Many people get caught making too large a change in wing loading simply because some expert said the wing loading they were contemplating is still “conservatively low.” Well, by whose standards is the wing loading conservatively low?

Consider two students in the following example: Let”s say we have a 100-pound jumper whose rig and clothing weigh 25 pounds, has been jumping a 260-square foot canopy as a student and is ready to buy his first set of gear. He has heard that 1.0 lb./sq. ft. is “correct,” but a friend says to go bigger for the first canopy at a wing loading of 0.8 lbs./sq. ft. He chooses the more conservative guideline, and he runs the numbers: 125 pounds total suspended weight divided by 0.8 lbs./sq. ft. equals 156 square feet. What a huge change from the 260! While the 260 seemed to float all over the sky at a leisurely pace, the 156 just screams at the ground! Sure, he expected to go a little faster, but not furiously howling fast since his friend told him this was still a “conservatively low” wing loading. It would be better to first try a 230 and see what it”s like, then a 210, and so on until a reasonable size feels right. He may find that he prefers the 190, which happens to work out to 0.65 lbs./sq. ft. He needn”t risk going smaller if the 190 gives him all the speed he is comfortable with. Let”s continue with the other jumper in this example, who has the same number of jumps but weighs 200 pounds. He started on the PD-300, but transitioned to the 260 on the last few jumps before graduation. If he went to the same 0.8 wing loading, he would probably be disappointed. Why? Run the numbers: 200 pounds, plus 25 for gear and clothing equals 225, divided by 0.8 lbs./sq. ft. equals 281 square feet. He would be jumping a bigger canopy than he was used to! So the 0.8 pounds per square foot wing loading might feel quite slow to one jumper but positively frightening to another with the same number of jumps.

What About Experience Level?

Looking at the scenario above, one can see that defining “experience level” has become more complicated, too. These two jumpers may have the same number of jumps and a similar freefall skill level, but their experience under canopy is certainly different. The type of experience, rather than the level of experience, is most important when referring to canopy skills. Remember that it”s all relative to what you are used to. Don”t be too quick to drop to another size simply because you landed well this time in an open field with no traffic.

You may be surprised how difficult it can be to land accurately in a tight area, compared to using a larger canopy. One very important point: Be careful talking about high and low wing loadings to others. If you happen to be comfortable with a wing loading of 1.6, then one jump on a friend”s new and untried canopy at 1.2 lbs./sq. ft. will probably seem pretty docile. But don”t describe it as docile to the new owner, or even to someone with twice as many jumps as you! You”ll likely mislead him, especially if he considered his old canopy flown at 1.0 lb./sq. ft. to be “pretty hot.”

Remember that we judge speed according to our own frame of reference, so what one jumper considers slow, another of the same weight and experience may consider lightning fast.

Changes in Performance

There are several characteristics created by having a higher wing loading. It is important that the jumper become fully prepared for these changes before flying at a higher wing loading.

The first and most obvious change is more speed. However, the new feeling of greater speed will one day feel normal, and perhaps one day even slow, though it certainly isn”t. Many people then bring this additional experience to the next smaller size, and the rush is back. But at what cost? Clearly one can push this too far, too fast.

A second characteristic of higher wing loadings is a much higher descent rate. By going to a smaller size of a particular design, the small increase in speed comes mostly from a large increase in descent rate—which means less hang time under canopy, less time to collapse your slider and less time to “play” under canopy. At high wing loadings, the flight might be fun, but the time aloft is usually short.

The glide ratio—which is the ratio of the forward movement though the air compared to the downward movement—also changes under increased wing loading. A canopy that flies three feet forward though the air for every one foot of descent has a glide ratio of three to one (3:1). Some designs emphasize glide angle more than others. However, when you go to a smaller canopy of any particular design, the glide ratio goes down. Some people may contest this point, but their arguments don”t holdup. Aerodynamicists will correctly tell you that increasing the weight of an airplane doesn”t change the glide ratio. However, this doesn”t hold true for parachutes. To explain this, it helps to know that the glide ratio is the same as the ratio of total lift to total drag. When we increase the wing loading of an airplane, we put the weight inside the airplane. This makes it glide faster, so that lift and drag are both increased proportionally, resulting in the same glide ratio. However, when we increase the wing loading of a parachute, we hang a bigger person out there in the breeze. When you jump a smaller canopy to get the higher wing loading, your body becomes a proportionally higher percentage of the drag. In either case, the result is still a poorer glide.

Another change in flight characteristics is how a jumper under canopy is affected by the wind. Keep in mind that glide ratio is not the same thing as the distance covered across the ground from a given altitude because the winds come into play. As mentioned previously, a higher wing loading makes it easier to penetrate headwinds. In a tailwind, you might find that someone flying a big 7-cell may go further than you at full glide on your trusty, familiar 170, even though his glide ratio is lower. However, as described last month, anyone can hold some brakes to slow the descent rate when flying back, and the exact amount of brakes helps considerably in high wing loading situations.

Going to a higher wing loading also increases the slowest possible flight speed of the parachute. When you go to a higher wing loading, unfortunately the stall speed increases. A stall may happen more abruptly, with less warning, and at a higher airspeed. This means it is not possible to fly an approach into a tight area as slowly as you could with a lower wing loading. The landing speed is also higher. Since we are descending much faster on final, the canopy must do more aerodynamic work in the flare to achieve zero rate of descent. With less canopy over your head, it must not only work harder but more efficiently as well. To extract this efficiency from the parachute, the flaring method must be more precise. Moving either toggle even a few inches may have a big effect on the resulting landing. On the other hand, a large student canopy descends slowly on final. It doesn”t have to do much more work to get to a zero rate of descent, and there is lots of surface area to work with. Therefore, the technique for landing a large canopy is not that critical, and a variety of rather crude flaring methods will all give reasonable landings. Toggle movements of as much as one foot will hardly affect the landings at all.  Since poor technique can still produce soft landings under a big canopy, many students develop poor canopy control habits. In many cases, the graduate student carries this poor technique with him to smaller and faster canopies later, and eventually it causes problem landings.

High wing loading also changes the flight characteristics of turns. The aerodynamic relationship between bank angle, turn radius and rate make the turns different at high wing loadings. Misunderstanding of this often leads to the dangerous low turn accidents all too common today, even with conservative people who never want to do hook turns. Obviously as the canopy gets smaller, the turns get quicker, right? Well, yes and no. To explain, think of two motorcycles going around the same curve but at different speeds. The faster bike must be leaned over much more to make the turn, while the slower rider leans much less. For turns that have a constant radius, more bank angle is required as the speed increases. If the slower rider now chose to lean exactly the same amount as the faster one, he would go off the inside of the road and make a much tighter turn. The slower bike would turn a complete circle much quicker than the faster one. For turns that have a constant bank angle, the slower the speed, the tighter and quicker the turn. These two observations are also true for airplanes and parachutes. For a given bank angle, the slower parachute will make a 360-degree turn more quickly, and in a smaller area. So in some ways, the canopy at the lower wing loading has better turn performance, especially if you start looking at how much space a certain turn occupies! In this description, we are referring to a turn where the flight path is still somewhat flat, and turning at a full glide rather than a vertical spiral straight toward the ground. At full glide, an attempt to turn faster results in a spiral dive with a rapid increase in descent rate. When flying a smaller canopy, this spiralling dive rotates much faster. As the wing loading goes up, the spiraling rate does get quicker. Since more speed requires greater bank angle for a given turn rate, the altitude loss builds up much faster at high wing loadings. A large student canopy might double its rather low rate of descent in a hard spiral. A modern canopy flown at high a wing loading, however, may quadruple its already high rate of descent in the same turn! At extreme wing loadings, the increase in rate of descent can be astronomical, with a 180-degree turn consuming as much as 500 feet of altitude!

Better, Earlier Planning

It is underestimating the amount of altitude lost in a turn that can easily get you into trouble when flying at wing loadings higher than you”re used to. Planning your landing pattern becomes much more challenging. Many conservative jumpers are often caught off guard by this when trying a smaller canopy. The typical experienced yet conservative jumper flying his own canopy becomes accustomed to judging how much time and altitude he needs to fly a conventional downwind, base and final approach, where the final turn is just high enough to be called conservative and not a hook turn. When this conservative jumper tries the smaller canopy, the turns cover more ground than he expects. Since the turns run wide, he turns a little sharper. As he does this, the flight path becomes very steep, resembling a diving spiral, eating up altitude very quickly. After a turn like this onto downwind, then another onto base, the unfortunate jumper may have insufficient altitude to complete his last turn to final. But often the extra speed taxes his perceptual skills, throws his judgment skill slightly behind, and he finds himself doing an unwanted low hook turn. Yes, his first hook turn, on the fastest canopy that he has ever jumped—and an unfamiliar one too!

The solution to dealing with this rapid altitude loss in turns is three fold: First, make only a small change to the next size down, and if you”re not sure, wait! Second, plan farther ahead. Enter your downwind leg much higher, and fly a larger pattern with larger radius turns. Use brakes to adjust flight path and descent rate. The third part of the solution is to really experiment and learn all about flying braked turns. (This concept of trading excess air-speed for precious altitude was discussed in last month”s article.) By using braked turns early in the pattern to conserve altitude, you can leave lots of altitude for a safe turn to final. Doing the opposite (making full-glide turns early and a low, braked hook turn at the last second) shows poor planning skills and a lack of good judgment. It is also somewhat suicidal.

Swoop Landings

Accidents occur when swoop landings are done incorrectly. Turning approaches, though fun, add to the danger and compound the problem. The higher risks of such landings cannot be ignored. I hate it when some knucklehead takes himself out doing something stupid, but it”s even more infuriating when they take someone else with them. Forgive me if I sound a bit brutal here, but while I don”t wish to encourage the uninterested to experiment with swoops, I feel some safety hints may help those presently involved. Avoiding the discussion is to ignore a vital safety problem.

• First of all, there is no real reason for a swoop landing—except for the pure enjoyment of the last part of flight. Put down your ego for a while. This need for speed does not dominate over the obligation to fly in a manner that enhances the safety of all the jumpers in your vicinity. Don”t even think of swooping if traffic is even a little heavy. It”s not even close to permissible just because you didn”t hit anybody.

If your fancy landing startles some novice jumper or causes others to become preoccupied with your actions, then your fancy landing was dangerous and rude.

• For those attempting such a maneuver, an efficient swoop is made with a smooth but conservative approach. You”ll swoop farther than the guy making the radical snapping turn with the coarse control movements. If you make turning approaches, do so much higher and smoother, with less bank angle. You”ll be amazed at how much speed can build up using this technique.
• If you think a turning approach is needed to build up enough speed to get a good landing, you probably need to work on perfecting your technique. A conventional landing approach should work well, even at high wing loadings. But if you insist on experimenting with turning approaches, do so only on a canopy you are very familiar with, not some new canopy that you have only one or two hundred jumps on.

It can actually take thousands of jumps on a single canopy to become consistent with turning approaches, and the accident reports are littered with those who seemed to be consistent until that last jump…

• When the decision is made to attempt a turning approach, do so with lots of excess altitude. This will give more time to correct errors in judgment before they can hurt you or others. You will also have lots of time and space to change the plan entirely. For example, if you set up very high and notice previously unseen traffic halfway through your turn, you should have both the speed, altitude and skill to quickly abort the diving approach and change to a rapid gain of altitude, even continuing the turn if necessary. Make a braked approach to a straight-in landing, then walk over to the other jumper and apologize for your poor performance and lack of vigilance for other traffic. None of this is possible from a “low hook turn.” If you can”t visualize the methods needed for this set of maneuvers, including the apology, then don”t even think about doing a turning approach—especially when I”m in the air with you.
• Learn how little altitude can be lost in a turn while at higher altitudes, but only use this method as an emergency salvage maneuver to abort the normal turn that seems a little too close. Never intentionally attempt a turn so close to the ground that the salvage method is the only possibility of pulling it out. Your judgment is probably off, so you might smack the ground. You don”t think your judgment will be off? Then how did you get into the position of needing this low turn anyway?
• If you find yourself needing to pull the toggles down hard to avoid hitting the ground, of course do so. Try hard to keep the wings exactly level, all the way through touch down, until all movement stops. Don”t give up! Then, assuming you have survived, get up (if you can) and kick yourself hard for exhibiting such poor planning, such poor judgment and such poor skill. It”s critical to understand that an intentional “low turn” has no value for swoop landings since it doesn”t allow enough possibilities for salvage maneuvers if you misjudge. It does not allow enough altitude for a more efficient, gentle pullout, nor enough altitude to build up lots of speed. Therefore, little energy is left after the pullout, resulting in little ground skim, if any. Every weekend, people foolishly impress themselves with these low hook turns with sharp pullouts, actually believing that they have it all figured out. They should stop kidding themselves.

Canopy collisions are more frequent now than ever before. As jumpers continue to buy smaller and faster parachutes, it”s everyone”s job to stay alert under canopy.

• If experienced jumpers, especially swoopers, are getting concerned enough about your approaches to try and talk to you, listen well! Carefully evaluate what is said, and determine whether the information is helpful or dangerous. There is always more to be learned—no matter who you are or how many jumps you have.
• Finally, never underestimate how much your approach decisions affect traffic that is very far away. Don”t be selfish, Don”t be stupid. If somebody seems angry because of an approach you made, listen to him and think carefully about what he says. Be considerate.

The Future

The aerodynamic advancements in canopy design have created better landing qualities and have permitted jumpers to experience the challenge of higher speeds and swoop landings. Unfortunately, our decision-making skills don”t speed up just because the canopy flies and descends faster. Our workload under canopy has greatly increased, whether we fly a fast canopy or not. This has forced our sport to grow, and the accident reports show us that we are having growing pains.

Our bodies are fragile. Since we occasionally make mistakes, we must be very careful to choose a parachute size and model that allows for some reasonable margin of error consistent with the type of canopy flying experiences each person has.

We must also choose a flying style that allows for the same margin of error. We need to realize that as wing loading becomes extreme, the options for safe flight in traffic can become so limited they restrict the canopy flying experience too much to be really enjoyed. Perhaps a slightly larger canopy will allow experimentation with more aggressive techniques and provide more fun, greater freedom and greater safety. As more and more jumpers become highly skilled and more courteous to each other in the air, our sport will become safer and more enjoyable. One result would be a decline in today”s high accident rate under canopy. Our wonderful flying machines have been made possible not only by the extensive research into parachute aerodynamics, but also by the public”s improvement in canopy flying skills. In some ways, getting a parachute through development and onto the market depends as much on the public”s skills and readiness as it does the manufacturer”s research. Parachute manufacturers feel uneasy knowing that their new products will be flown improperly by some. This will continue to delay introduction of new and totally different parachutes that have capabilities undreamed of. In my place of work, these parachutes of the future sometimes feel like decades away, but who knows? If we all move toward more courteous piloting, higher canopy control skills and better judgment, perhaps these “super canopies” may come sooner than we think.

About the Author

John and some awesome hair

John LeBlanc, D-10824, completes his second installment on canopy control with this article; part one was published in July. As vice-president of Performance Designs, Inc., in Deland, Florida, LeBlanc remains on the cutting edge of new parachute technology.