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Wing Loading

Buying skydiving equipment for the new skydiver

When Should Beginners Buy Their Own Gear

ORDER FORMS click here

Maximum Allowable Canopy Wing Loading for Skydivers

i.e.: 225 lb/Wt + Gear = 225 lb divided by 150sf = 1.5 wing loading

Jump Range

Max. Wing Load allowed

Non-licensed

0.8

25 to 100 ... A-B license

1.1

101 to 200 ... B-C License

1.3

201 to 400 ... C License

1.4

401 to 600 ... C-D License

1.5

601 to 800 ... D License

1.6

801 to 1,000 ... D License

1.7

Over 1,000 ... D License

Use Proper Judgment

Wing loading is the ratio of jumper exit weight to canopy size. The formula for wing load is the exit weight divided by the canopy size.

For example:

Joe has an exit weight (Joe + gear) of 225 pounds and is jumping a 150 square foot canopy; Joe’s wing loading is 1:1.5.  It is common to drop the 1: and call it a 1.5 wing loading.  Joe would need at least 401 jumps and a C license for this canopy.

 

A seminar by Performance Designs, Inc.

Speaker: John LeBlanc

I. Wing Loading Defined

Wing loading is a measurement of how much total weight is supported by how large a wing,

and is usually expressed in pounds per square foot. Everything the jumper exits with, including

all clothing, the rig and both canopies must be included in the weight.

Example: Exit weight Canopy size Wing Loading

190 pounds 190 square feet 1.0 lb./sq. ft.

150 pounds 150 square feet 1.0 lb./sq. ft.

190 pounds 95 square feet 2.0 lb./sq. ft.

150 pounds 75 square feet 2.0 lb./sq. ft.

In very general terms, the heavier the wing loading of a parachute, the more quickly everything

happens in flight, and the more critical correct flight techniques becomes.

II. General Concepts that are frequently misunderstood

A. Different canopy models of the same size may perform differently, but they will

fly approximately the same speed.

Wing loading is the biggest determinant of speed. A Stiletto 190 is not really faster

than a Sabre 190, or even a PD 190! Other aspects of performance will be different,

however. (Turn rate, glide angle, etc.) These differences may influence a person’s

impression of speed.

B. A person evaluates a canopy’s speed according to their individual frame of

reference, which has been created through their own, unique experiences.

Example: Jumper A and jumper B weigh the same, jump the same canopy, and have

the same number of jumps. They may have completely opposite opinions of the

speed and handling of their canopies. Why? Different frames of reference! The

canopy may be the smallest one jumper A has flown. He may have chosen it to get

more speed, quicker turns and hotter landings, and might feel that it’s a handful! Yet

jumper B may have moved up one or two sizes to this canopy, to create more

forgiving handling and easier landings than he had previously.

C. When discussing the speed and forgiveness of a particular canopy, remember

the different frames of reference of the individuals involved.

Be careful to avoid projecting your frame of reference onto a person to whom you’re

describing a canopy. Example: If a person is asking advice about trying a new

canopy that is much larger than what you are currently jumping, you’ll likely consider

it rather slow and docile. But telling them so could be a big mistake if they’ve spent

their whole skydiving career on a much larger canopy. Regardless of how you feel

about the canopy, it will be the fastest, most responsive canopy they’ve ever jumped.

This is true regardless of any wing loading calculations you might make.

D. It is not necessary to heavily load a high performance canopy to make it fly and

land correctly.

This is a common misconception even with many experts. If a person’s canopy is

going the speed they are comfortable with, then that should be fine. If they’re not

getting good landings on a properly designed canopy flown at a lower wing loading,

they’re probably not flaring it correctly.

E. Choose your canopy size by reflecting on your impression of the canopy sizes

and models you have recently flown, combined with your desire to go faster or

slower.

Choosing a canopy this way is much safer than using only a chart published by a

manufacturer. Such a chart may be a rough guide, but cannot be used effectively

without applying your own experience. If you don’t want to go faster, don’t go smaller

than what you are using!

III. More advanced concepts about wing loading

A. Test your beliefs about canopy Wing Loading:

Which of these general statements are true and which are false?

1. Two jumpers with widely different exit weights will get the same performance

if they have the same model of canopy, sized for the same wing loading.

2. Its possible for two jumpers with widely different exit weights to get the same

performance, but the lighter jumper must load their canopy a little more

heavily.

3. Its possible for two jumpers with widely different exit weights to get the same

performance, but the lighter jumper must load their canopy a little more

lightly.

4. When you downsize to a smaller canopy of the same type, you will have the

same glide angle, but you’ll go faster.

The following questions concern two jumpers with exit weights of 135 and 230

pounds, flying a Sabre 135 and 230 respectively. They have the same wing

loading of 1.0 lb./sq. ft. Which of the following statements about these two

jumpers are true and which are false?

5. The canopies will provide identical performance for both jumpers.

6. The jumpers will have the same glide angle and speed.

7. The canopies will have similar handling and responsiveness in turns.

8. The canopies will have similar stall characteristics.

9. Assume the lighter jumper above stays with a Sabre (a rectangular canopy)

but the heavier jumper changes to a highly elliptical canopy at the same wing

loading, for quicker turns. In this case, the heavier jumper will definitely be

capable of out turning the lighter jumper.

10. Assuming that both jumpers have similar skill levels, and both are planning

to transition to smaller Sabres that give a 1.3 lb./sq. ft. loading. In this

situation, they will have similar challenges with getting good no wind

landings because their change in wing loading was the same.

B. Do equal wing loadings on a given design give the same performance?

1. Though many canopy models may come in several different sizes that are

usually scaled geometrically from one to another, they don’t fly the same at

equivalent wing loadings. Why? Because the physical and aerodynamic laws

that the parachute must obey don’t scale up and down with the parachute.

2. Most jumpers do not normally consider the above point. They assume that a

change in performance when downsizing is due purely to a change in wing

loading. Since they normally don’t change their exit weight very much when

jumping a particular canopy, they don’t ever load that canopy at wing

loadings similar to what they would if they downsized.

3. However, the change in handling from one size to another is due to much

more than a change in wing loading. This can be proven by jumping a small

canopy at your normal exit weight, and then jumping a much larger, scaled

canopy, with enough extra ballast so that the wing loading is the same. The

difference is dramatic. The larger canopy certainly goes faster when carrying

the additional weight, about the same speed as the smaller canopy flown at

the same wing loading. However the handling still feels very similar to when

it was lightly loaded.

C. Some reasons for differences in performance between large and small

canopies:

1. Turns: In general, the smaller the canopy, the shorter the lines. Its true that

two proportionally scaled canopies may have similar full glide speed at the

same wing loadings, but they turn very differently. The big canopy, with its

long lines, has relatively sluggish reaction to the controls, and the small

canopy has relatively quick reaction to the controls. This is due to the fact

that the large canopy must move the jumper a much greater distance out to

the side, in order to achieve a certain bank angle needed for any given turn

rate. This means that the smaller version of a canopy will feel much more

agile, even if flown at the same wing loading.

2. Flaring: A dynamic flare is one that results in a change in flight direction

from a descending path to one parallel with the ground. This requires a

change in the angle of the canopy, when viewed from the side. (Initially, the

amount of the angle change is about equal to the angular change of the flight

path.) This angle change is accomplished using toggle a movement that

causes the jumper to move out in front of his natural hanging place under the

canopy. The long lines of a big canopy require the jumper to be moved a

greater distance out in front to achieve the same angle. Shorter lines mean

that the jumper doesn’t need to move as great a distance forward to achieve

the same angle. This means the toggle movement must be more aggressive

on the larger canopy, compared to the smaller canopy, even at the same

wing loading.

3. For similar reasons to those above, the smaller canopy will also dive more in

hard turns, when compared to a larger scaled canopy, even when flown at

the same wing loading.

IV. Applications of these ideas in today’s canopy environment:

A. Lighter jumpers face a greater challenge than heavier jumpers do when

jumping typical first - jump student gear, due to very slow flight and sluggish

controls.

1. Lighter students usually start at lighter wing loadings and very slow flight

speed, compared to larger students, because they often use the same

canopy.

2. The instructors are less likely to give a lighter student the attention to canopy

control they deserve. It’s easier for an instructor to notice a slight problem

with the larger student’s performance, and they are more likely to correct it.

The instructor is likely to be less concerned about the lighter student,

because the canopy is so slow that the landing is likely to be soft, even with

poor technique, and the possibility of injury is remote.

B. Lighter student graduates face considerably different challenges when they

start downsizing.

1. Lighter students are normally encouraged to be more aggressive when down

sizing, making much larger changes in wing loading than their heavier

counterparts. Though the resulting speed may be similar or even less than

that of a heavier novice, they’ve experienced a much bigger change in speed

compared to what they started with.

2. Due to the fact that the smaller jumper will likely be transitioning to a smaller

canopy than the larger jumper will, they’ll get quicker responsiveness from

that canopy. Again, this is true even though they’re wing loading is probably

lower.

3. There is a bigger difference between what a lighter jumper is told and

what they are experiencing. Though the lighter novice may be jumping a

fairly small canopy with fairly responsive controls, they may be incorrectly

told that they are still being very conservative, because their wing loading is

low compared to a heavier novice jumper. The heavier jumper, on the larger

but more heavily loaded canopy, will still have more sluggish response from

the canopy, which dampens the effect of his incorrect control inputs.

C. We have been erroneously attributing the lighter jumper’s general preference

for lower wing loading to the wrong reasons.

1. Looking at the entire skydiving population, females are generally lighter, on

the average, than the males. The fact that female jumpers generally settle on

a lower wing loading is usually attributed to the fact that society considers

them to be somewhat conservative and less aggressive, whether this is

justified or not.

2. I believe that experienced jumpers, whether light or heavy, are probably

looking for a certain degree of responsiveness from their canopy. The lighter

jumpers will get that responsiveness at a lighter wing loading. The heavier

jumpers will get that responsiveness at a heavier wing loading. This is the

main reason for canopy wing loading differences.

D. We have been attributing the lighter jumper’s preference to more conservative

models of canopies to the wrong reasons.

1. The typical experienced jumper’s choice in a style or model of canopy may

also be examined in the same way. A smaller jumper gets plenty of

responsiveness from their smaller canopy. Therefore, it is likely that they will

be less attracted to the quick responses of a highly elliptical canopy, and

instead will prefer a more conservative model of canopy. This will allow them

to go quite small on the canopy to get the speed they may want, but without

getting handling that is too “twitchy”.

E. Highly experienced lighter jumpers should be very careful in the logic they use

to justify their downsizing process.

1. Until very recently, very small canopies were not available to the smaller

jumpers who wanted to experiment with very high wing loadings. Now that

they are becoming more common, lighter jumpers are often encouraged to

downsize to similar wing loadings as their heavier counterparts. They are

often pressured to downsize against their own judgment

2. We need to consider the fact that at equal wing loadings, the smaller jumper

has a much more responsive canopy than the heavier jumper has ever had

to deal with. This responsiveness of the small canopy tends to magnify small

errors in technique. A larger jumper, at a similar wing loading, is flying a

larger canopy, which will tend to minimize the effect of small errors in

technique.

V. Conclusions:

As you can see, the answers to the questions in the quiz are all false. We must be very

careful when discussing canopies with those who are downsizing. Do not recommend

specific canopies to individuals without spending some time to learn about the jumper’s

particular frame of reference. Assist others in making small changes in canopy size from

what they are used to, and only if they’re ready to deal with the higher speeds and more

agile handling. Have fun, but be careful!


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