Most manufacturers publish maximum weights for their canopies. Many also publish advisory weight limits or wing loading limits for their canopies for a variety of experience levels. Even when these advisories are not prominently published, they are usually easily obtained by means of a letter or e-mail. Unfortunately, although a huge amount of information is available to anyone who is armed with a postage stamp or an internet connection, most skydivers, and many instructors, do not know the published limits for the equipment that they use. Even when they do know the figures for their equipment they often misinterpret what the manufacturer actually means by these figures. This raises both safety and litigation fears, particularly where student parachutists are concerned.
Tell a skydiver that a canopy has a weight limit of 250lbs and he will usually think that he can put a 250lb jumper under it in safety. This is usually very wrong. So what does a parachute manufacturer mean by maximum weight?
Maximum All Up Weight / All Up Mass / Exit Weight / Total Weight
These terms all mean essentially the same thing and are the most commonly used type of weight limit. They are used by most British, American and South African manufacturers, indeed by any manufacturer who operates within the FAA TSO system and by most manufacturers who provide equipment to the military. All Up Weight or Exit Weight means the weight of the skydiver and ALL of his equipment at the moment of exit from the aircraft (body weight of jumper plus main plus reserve plus pack and harness plus helmet, goggles, altimeter, clothing, jumpsuit, gloves, AAD, radio, weight vest, sky board, cameras, loose change, pull-up and Polo mints). The weight of experienced equipment combined with lead vests, or the weight of novice equipment alone can easily mean that a 210lb jumper exceeds the quoted 250lb limit for his canopy! This system is confusing and misleading for many skydivers but has to be applied for accurate definition of safe loads in TSO test programs. Many experienced parachutists just can’t make themselves believe that they have to include the weight of the canopy/wing in the calculation, even when specifically told about it by the makers. However, this is a standard aviation practice and you have to get used to it if you want to know what a canopy is actually cleared for.
“Suspended Weight” means different things to different manufacturers. The name suggests that it means all weight suspended from the parachute in use ( i.e. All Up Weight minus the 4-12 lb canopy weight ). This is the way it is used by a major French Manufacturer. However, many American manufacturers use the term “Suspended Weight” but actually mean All Up Weight. You only actually find out by reading in depth in some of their documents or by writing to ask for their definition of “Suspended Weight”. Confusing, isn't it?
I have only come across one manufacturer who defines their canopies maximum weight in terms of jumper body weight (clothed for decency!). This is certainly the easiest definition for a jumper to apply to themselves. However, it is the least accurate and least secure in terms of the risk of overloading a canopy because no account is taken of the large variation in weight of parachute equipment and extras. This particular manufacturer takes the view that you are lucky if a jumper knows their own weight, let alone their exit weight. He writes that limits defined as body weight are more likely to be understood and applied by the majority of jumpers and so has taken the pragmatic decision to use this definition. Notwithstanding the woolliness of this definition, it certainly has a lot of advantages for the average skydiver.
For a single type and size of canopy, some manufacturers specify up to eight different weight limits for various experience levels of jumper. Some are tightly defined and mandatory. Others vaguely defined and purely advisory.
American manufacturers tend to be very forthcoming with a wide range of information and advice, but some European manufacturers are stonily silent, publishing little but a single absolute weight limit to be applied equally to the first jump student and the skygod.
 |
 |
 |
 |
 |
This is the maximum weight that the manufacturer approves for use with this canopy. It is a structural limit. For canopies with an FAA TSO this means that the canopy has been tested and been found strong enough to withstand normal opening shock with this load. If this limit is exceeded by a significant amount the canopy is at increased risk of tears, line breaks or disintegration during deployment. The Maximum All Up Weight is (in theory at least) backed up by law in the U.S.A. It is a federal offence to jump with a reserve whose MAUW is exceeded. The MAUW has no relevance to canopy handling characteristics and there is no implication of safe handling at MAUW. The MAUW is normally the only weight to be stamped on the data panel of the canopy.
These are purely advisory limits. The terms Experienced / Advanced / Intermediate are not defined in any consistent way and indeed there is no need for a tight definition. These limits are provided simply to help the literate, numerate, level headed skydiver make a sensible choice of canopy. I wonder how often that actually happens?
“Student” is a term which is clearly defined by most parachuting organisations and so it is clear to whom it is meant to apply. Since students encompass a wide range of experience and skill levels, the Maximum Student Weight may still be well above the ideal for a first jump student.
Some manufacturers publish not only a Maximum Weight for Students but also a much lower Ideal Student Weight Range. These weights are usually All Up Weights from which kit weight must be subtracted. The Ideal Student Weight Range is intended to give docile handling and forgiving flare characteristics suitable for a first jump student, while still maintaining adequate drive to allow control against the wind. Some manufacturers may specify that some of their canopy makes and sizes are “not suitable” or “not recommended” for students at any weight whatsoever.
Beware of the term “Novice”. In Britain it usually means a student on his or her very first jump. However, in the USA it seems to be used to refer to jumpers who are “Off Student Status” but still of very low experience. I just couldn't understand why “novices” were being allowed to jump at much higher weights than “students” until one of the American manufacturers explained to me what they meant by “Novice”:
“A novice is someone who is off student status. In other words they have been cleared to jumpmaster themselves. This category can then go through to varying levels. Probably the most reasonable would be to say that a novice is anyone off student status, but not yet licensed. (In my mind a novice is anyone who has not received a D license or equivalent)”
Yet again, two nations divided by a common language!
Where Minimum Weight is specified, the manufacturer often states that the minimum is there just to provide good canopy performance and that it may be used with lighter loads when extra docile handling is required. Probably the majority of manufacturers report no minimum weight or just vaguely report that it "“varies with landing conditions”. This will be discussed further under canopy loading.
I have found one make of reserve with an “absolute minimum weight” quoted. This minimum weight was actually at a level similar to some makers maximum for students. On further enquiry with the manufacturer, it turned out that they had a rather different attitude to canopy loading. They felt that it was important to have plenty of weight under a canopy so that it had plenty of drive to hold against strong wind and so that it had plenty of speed to get good response in the flare. They stated:
“Stability is not the primary factor to be concerned with when loading a canopy a little below the minimum wing loading, but realize that there must be some lower limit. Students who are trained properly in the use of modern ram-air canopies will find better performance when operating within the recommended weight range. (by proper training I mean it is important to know, among other things, how and when to flare) While operating outside the published limitations is dicey at best, there is a much greater danger in excursions beyond the maximum limits than beyond the minimum limits.”
They are of course correct in that best landings are obtained with good flare technique applied to a fast flying canopy and are further correct in that it is very important to teach students when and how to flare. Unfortunately, even with impeccable training and the use of radios, many students still fail to make a satisfactory flare. No flare or a high flare on a highly loaded canopy can each result in injury. It is probably no coincidence that over 50% of all RAPS landing injuries are associated with poor flare technique. This one manufacturer’s advice about minima is probably very relevant to most experienced jumpers but their rather overoptimistic expectation of student landing technique must mean that their advice on minima may have very questionable relevance for students.
Navigator 280 Max AUW 336 LBS, Max Student AUW 254 lbs, Ideal Student AUW Range 140 – 230 lbs.
In terms of body weight this translates to Max Wt 21½ st, Max for Experienced student 15½ st, Ideal Student Weight Range 8 – 14 st. Take note of the 106 lbs difference between the Maximum All Up Weight and the upper end of the ideal student weight range.
Exceeding the weight limits on a canopy can have consequences both for the jumper and for the DZ operator. The consequences of exceeding the MAUW are expressed succinctly by PD :
“The absolute maximum suspended weight for the canopy is the absolute legal limit. There are no situations where it is permissible to exceed the maximum suspended weight for the parachute. Structural failure may occur if you exceed these limits. By exceeding the absolute maximum suspended weight you risk serious injury, death, equipment failure, and FAA violations or fines.”
Sadly there was recently an example of this in the USA where a jumper exceeded the MAUW for his reserve canopy, there was structural failure on deployment and he was killed.
The risk of litigation for a DZ operator who allows a student to exceed the MAUW for a canopy should be fairly obvious. With more and more manufacturers also specifying maximum weights for students and openly publishing them on the internet, it is likely to become increasingly difficult to defend cases of student injury where these limits are exceeded.
It is of interest that some canopies which are openly labeled as “Not Recommended for Student Jumpers” are in common use at some British DZ's for lighter students. I asked the manufacturer whether these canopies could reasonably be used at low wing loadings for very light students and was told:
“N/R indicates Not Recommended……….This means that at no loading do we recommend that model and size for those categories.”
We are taking female students, who are already known to have an injury rate much higher than men and are placing some of them on canopies whose manufacturer considers them to be unsuitable for student use at any wing loading. There used to be a time when it was a defence in court to show that a significant body of parachutists were involved in the use of similar techniques or practices, but there is now an additional requirement to show that any such practice is righteous, reasoned and respectable. Under these circumstances, that may not be so easy.
Nowadays it is common practice to express the load on a canopy in terms of Wing Loading in pounds per square foot (lb/sq.ft). This is both a precise and concise way for the manufacturer to advise on suitable canopy loadings across a wide range of canopies. Unfortunately, it is even more complicated to apply than MAUW!
Wing loading is simply All Up Weight (or Exit Weight) divided by the surface area of the canopy. There are, in fact several different ways of assessing the surface area and each can give a slightly different figure. It is simpler just to accept the makers figure. PD give a helpful description of the process of calculating wing loading:
“Wing loading is easily calculated by dividing a total suspended weight in pounds by the surface area of the parachute in square feet. Total suspended weight is the weight of the jumper plus all his clothing and gear, including all components of the parachute system. The system area of Performance Designs, Inc. canopies is printed on the data panel on the centre cell top surface near the tail. (Be sure to actually check the data panel; canopies of different sizes may look the same.)
A typical ready-to-jump sport piggyback (rig and both canopies) weighs 20 to 30 pounds. Add this, plus the weight of your jumpsuit, clothing and accessories to your body weight to get the total suspended weight. For example, a jumper who weights 165 pounds with his jumpsuit on and who jumps a packed rig that weighs 25 pounds would have a suspended weight of 190 pounds.
Here's an example of how to calculate wing loading of a 210 square foot canopy and the jumper used in the example above:
190 lb. / 210 sq.ft. = 0.9 lb./sq.ft.”
Rather than write a whole section on wing loading myself, I am going to reproduce part of PD's advice to jumpers. Different manufacturers may give slightly differing numbers for the wing loading to go with each of these definitions but the general principles apply with other canopies too.
“Any canopy's descent rate and forward speed increases as the weight it is carrying - the so called suspended weight - increases. The canopy also becomes more responsive and reacts more radically when it is stalled or turned. Penetration into the wind increases, but glide ratio decreases. Because of these aerodynamic facts, it is unsafe to put too much weight under any particular canopy. Safe and comfortable landings will be difficult to obtain, even for experienced jumpers under ideal conditions. Less experienced jumpers will have even harder time and be at greater risk.
Determining the “wing loading” of the parachute you intend to jump or buy is a good guide to matching your weight to a particular canopy.
The parachute is too large for you. The canopy will fly very slow, and may not have sufficient penetration, even in light winds. Turbulence will have a greater influence on the canopy. Light turbulence or wind gusts that canopies with higher wing loadings fly through easily may be sufficient to stall or collapse your canopy. We recommend that you do not use this canopy if the wing loading is below 0.45.
This is a lightly to moderately loaded parachute. This is a good area for students and low experience level jumpers. The canopy will be relatively slow and docile. It will be easy to land and will not require the very precise flare timing and technique that canopies at higher wing loadings require to get an acceptable landing. However, proper instruction in the use of this canopy is required. When jumping at this wing loading, you will be more limited as to wind speed, wind gusts, and turbulence than jumpers using canopies at higher wing loadings. Even if other jumpers are jumping, the conditions may not be safe for you to jump.
This is moderately to highly loaded canopy. The canopy will fly fast and turn fast. It will require a great deal of skill to land well. When landing at high elevations it may be difficult to get an acceptable landing even for very experienced jumpers. It will also be more difficult to land in confined landing areas. Be sure your skill level is up to the demands of this situation.
This is a highly to very highly loaded canopy. A very high experience level is required to get an acceptable landing,even under ideal landing conditions. The canopy will fly and turn very fast. A very precisely timed dynamic flare will be required to get the rate of descent to an acceptable level. Your forward speed may be very high when you actually land. Stalls will occur at relatively high flight speeds. It will be very difficult to land this parachute in confined areas or at high altitudes. Also keep in mind that if you are rendered unconscious and an AAD opens your reserve, you may still suffer severe injuries or death due to uncontrollable landing.”
There are some limitations to the usefulness of wing loading. It is not the sole predictor of a canopy's flight characteristics. Aerofoil design, wing shape, porosity, line type, line length, steering line rigging, pilot chute type, DZ elevation and weather conditions are just some of the factors that play a part. One would not expect a Para-Foil to have the same flight characteristics as a Stiletto, even if they had the same wing loading. Furthermore, it has been suggested that some small canopies in a series may behave more aggressively than their larger stablemates even when loaded to the same number of pounds per square foot (the basis of the claim is not clear). Nonetheless, Wing Loading is probably the single most useful tool for comparing loads on canopies, particularly for student jumpers.
Amongst the larger manufacturers who recommend specific wing loading ranges for students, 0.7 – 0.8 lb/sq.ft seems to be the upper limit for low experience students on canopies made of F111 or similar material and 0.8 – 1.0 lb/sq.ft for students on zero porosity canopies. Some manufacturers also recommend a limit for minimum wing loading of 0.45 – 0.55 lb/sq.ft on F111 canopies but there is little consistent advice on the lower limit for ZP canopies. Part of the reason for the variability in advice about ideal wing loading is due simply to the fact that different people have different points of view, but another part of the reason is that two different designs of canopy can both be loaded to an identical level of 0.7 lb/sq.ft but can have completely different turn, flare and surge characteristics.
Manufacturers also advise about wing loadings for more experienced jumpers. The recently graduated student may need that advice but often will not even be aware that it is available
If the upper limits for canopy loading are exceeded for students, the flare and surge characteristics become unacceptable and the risk of landing injury increases greatly. If the canopies are underloaded below the lower recommended limits there may be an increased risk of canopy collapse in turbulence and there will certainly be an increased chance of off-landings with all the risks that this entails. It is simply impossible to jump all students on a single size of canopy without grossly under- or over-loading on many occasions. Many drop zones already have two sizes of student canopy, one for the majority of jumpers and one for the very light girls. Not so many appear to have an extra large canopy for the heavier students. Thus the ideal wing loading may be exceeded for the heavier jumpers.
There are too many other things that have to be done on a drop-zone for an operator to individually calculate wing loading for each student that comes on a course. However, there is time to weigh the kit once, calculate what body weight will take a student to the upper or lower loading limits and post the upper and lower limits of body weight prominently for all staff and students to see. Sadly, if the DZ operator doesn't have time to do this, there are certainly plenty of lawyers, with their expert witnesses, who do have the time. If the operator doesn't have the mathematical or technical confidence to do this for themselves, there are others who can help. There are also spreadsheets that can do the job instantly for any DZ with access to a PC.
Many DZ's hold student records on computer nowadays. For these DZ's and indeed for any DZ that has access to a PC, it is possible to use a spreadsheet to instantly show whether a student’s weight places him or her within the ideal limits for most of the student canopies in use. These spreadsheet files can be saved permanently to demonstrate that an operator has actively considered whether a canopy was suitable for a student.
The attached spreadsheet has been designed to compare jumper weight with known limits and recommendations for the most commonly used mains (and also for a few reserves). The information is based on manufacturers data provided through data sheets, web sites, advertisements, direct correspondence, references such as Poynter’s Parachute Manual and actual weighing's of rigs and ancillary equipment. For each jumper, the spreadsheet can show body build, wing loading (or average rate of descent for a round canopy), whether MAUW is exceeded and, finally, make remarks about whether known recommendations are likely to be exceeded. When a manufacturer has expressed no opinion on wing loading, the spreadsheet will look at whether the canopy is normally F111 or ZP and express an opinion on ideal wing loading based on the approximate ranges mentioned above in “Restrictions”. The spreadsheet also makes an allowance for the weight of kit and assumes that a rig with a 320 sq.ft canopy weighs somewhat more than one with a 97 sq.ft canopy. Obviously, kit varies in weight considerably and the spreadsheet will not know the exact weight of a jumpers rig and ancillary equipment. However, it can still make a reasonable estimate, which should not be more than a few pounds out (unless lead, cameras or boards are worn!).
There is no requirement in law in the UK to follow a parachute manufacturers recommendations. Indeed, there may be occasions when an operator has excellent and fully justified reasons for loading a canopy slightly above or slightly below the “ideal” range for a Student. However, if an operator is going to operate outside this range, he or she should do so knowingly rather than in ignorance and should be aware that there is a body of opinion, openly published by manufacturers, which may be used against him or her in the event of an injury. I would suggest that there are no circumstances in which it is acceptable for an operator to provide a canopy which results in a student being above the Maximum All Up Weight as this situation results in a canopy being used outside its demonstrated safe structural limits.
The spreadsheet does not pretend to be the perfect source of all information about all canopies. Not all canopies are listed and not all recommendations for a given canopy may be on the spreadsheet. Moreover, canopy weight limits and recommendations do change with time. Equally, there are bound to be some bugs in any large spreadsheet ( – please try it out and let me know about them). However, as a quick reference source and as a means of stimulating an instructor to read further into detailed manufacturer’s documents, I hope it can be of some use. I am happy for any instructor to take copies of the spreadsheet provided a copy of these notes goes with each copy. I am equally happy to modify the spreadsheet to include new student canopies as their details become available – let me know when you would like a canopy added.
