Paragliding Evolution pt.2

Where and when did this evolution actually start?

It was NASA who started the serious work on pilot recovery from orbit. Werner von Braun was rather taken with NASA engineer Francis Rogallo’s partially-braced soft triangular gliding wing, and Rogallo’s 1960 paper on the technicalities can be read here. Check out the Mach number!

‘NASA Parasev’ is also a useful Wikipedia page about the resulting towed Rogallo trike, and includes a remarkable picture of a Gemini capsule under a version of this wing (a few inches above the lakebed). But at the same time another NASA employee, David Barish, designed and made a much simpler and lighter single-skin all-floppy device, and this was flown by Lee Guilfoyle in September 1965. Forty years later Francis Heilmann of France spent some time drawing, cutting and running up his copy of this design which he flew at the Coupe Icare in 2005. I actually saw it, and the majestic title picture of it is by Michel Ferrer.

Heilmann had asked Barish for help, drawings, information and so on for his celebratory replica, but Barish was reluctant. As an American he had a good idea of the product liability litigation that would surely come his way if an American citizen, or perhaps anyone else, crashed under it.

In June 1978, not so far from Annecy, three friends, Jean-Claude Bétemps, André Bohn and Gérard Bosson, went to Pointe du Pertuiset, Mieussy, France, with a square parachute. After inspiration gained from an article on slope soaring in the Parachute Manual magazine they calculated that on a suitable slope, a current "square" ram-air parachute could be inflated by running down the slope.

Bétemps went first, launched successfully, but soon made a 180 straight back towards the steep, deep-snow-covered slope, demonstrating the first fly-on-the-wall landing at cruise speed but without the flare. He was unhurt and the explosion of soft snow was spectacular. Bohn followed him, held his nerve and glided down to the football pitch in the valley 1000 metres below. This event can reasonably be regarded as the birth of paragliding as we know it. Things have changed a lot since then, and this could be my modern evolutionary starting point, but the spectacular and elegant 1965 NASA/Barish sailwing also qualifies.

Francis Heilmann, its 2005 resurrector, unaware that the prototype never flew more than a few feet above the ground, operates it in modern style, albeit carefully. Its relative lightness and simplicity of transport and unravelling has prompted present day questions about Hike and Fly suitability. It’s not the easiest or most agile thing to fly, and his hike&fly answer, “You would have to walk a lot”, tells us about its takeoff management and glide performance.

This picture shows an early paraglider, a lightened version of the square parachute, amongst younger models.

It is interesting that NASA finally settled for the tried and tested plain round parachute. I’m not surprised. But on to Part 2 of this 75 year evolutionary story:

The story so far

Part 1 ended with the international distribution of my 2009 report on the reasons for serious paraglider accidents at FAI world championships, compared with those of the other FAI flying disciplines whose competition accident rates were significantly lower. My only qualification for this task was some experience of another FAI sport, aeroplane aerobatics, and a decade of recreational paragliding in Switzerland, which had led to employment in the only Swiss manufacturer, and incidentally a most responsible, well-managed and meticulous paraglider company. My job is translating into English. As an FAI aerobatic person the conclusion of my report was based on the apparent lack of the paraglider establishment’s ability to filter suitable entrants for world championship level contests, bearing in mind the handling challenges available at the competitor’s discretion in terms of flying style and skill. What this means is don’t push your luck just because it’s a race; the laws of physics and mechanics do not change even when the pilot is tempted to challenge them.

The world reaction

Cross Country magazine wrote that someone (just one) in the UK delegation to CIVL commented that my report was ‘interesting’. Today, 12 years later and with more information, I now suspect that the fatal accident in the January 2009 (same year) world championships may well have given the final impetus to the significant changes that CIVL made in response to FAI demands that year: not a response to my elitist powered notions.

The main area of concern became not pilot quality but high performance paraglider behaviour and the difficulty of coping with it in emergency; after all, this is a cheap and convenient flying sport for all. The FAI’s determination that their paraglider competitions must become statistically safer persuaded CIVL, the FAI paragliding committee, and the PMA (Paraglider Manufacturers’ Association) to put their heads together. The result was a decision not to permit uncertified prototypes to take part. Therefore, only wings that conformed to the certification standards, relevant to public sale, could be used in future FAI competition. These standards relate to a judgment of the level of skill required for the satisfactory piloting of the subject glider.

What these standards say

Although experienced paraglider pilots worldwide will have a similar understanding of practical flying, the problem of quantifying this broad subject in words is difficult. Words mean different things to different people, even when written and read by users of the same language.

Here are the summaries from the early days, 30 years ago. The system started with three classifications, soon subdivided into five: 1, 1-2, 2, 2-3, and 3.

CLASS 1: Simple and very forgiving flying characteristics

CLASS 1-2: Good-natured flying characteristics

CLASS 2: Demanding flying characteristics and potentially dynamic reactions to turbulence and pilot errors. Recommended for pilots who fly regularly

CLASS 2-3: as for 2 except add Very demanding, violent reactions, and experienced pilots who . . etc.

CLASS 3: as for 2-3 except add very violent reactions, little scope for pilot errors. For expert pilots.

These are worse case words, but well worth considering if you wish to enjoy your flying without that uncomfortable feeling of unexplored risk. Only personal experience of surprise airborne challenges and their successful survival will give credence to these warnings. However, if, despite your limited experience in real terms, your basic handling is good, careful and thoughtful, then to fly today’s high performance paraglider on a quiet atmospheric day is a delight. The high aspect ratio wing gives a stately and secure feeling to the ride. Control is more sensitive, but pleasant if you have good hands; and the glide angle a revelation. The glider hardly wants to come down it seems, and soon you find yourself looking and thinking far into the distance, aware of a greater area of action with less concern for planning your nearby landing.

But you haven’t met a big bump yet. The classifications assume the possibilities you could meet, and certainly will if you go racing or intend to make long cross countries in rewarding conditions. Continued paragliding evolution in recent years has improved performance across the board, mainly by drag reduction. Reduced equipment weight (by 50% in my 20 years) has widened accessibility to the sport, and encourages more exploration of the hills and mountains on foot before flying down, or to destinations far away.

The second quarter century of paragliding has added a huge amount of piloting experience and knowledge: is paragliding coming of age, catching up the other sports in safety statistics? Technical improvements may have moved the reality of problem behaviour nearer the tops of the classifications, in two separate realms - the high-end B (for amateurs), and the less-discussed high-end D (for professionals, international competitors, - and competent but careful amateurs with mature judgment). But positive learning experience has spread, to confirm our evolutionary model, and more than balances its new challenges.

Paraglider certification

This is carried out by independent testing authorities, and consists of a detailed list of handling topics covering all aspects of normal flight, and a series of departed situations and the recovery from them. Each individual flight test item is scored according to its judged classification, and the highest number or letter awarded, whatever the topic, becomes the certification for the glider.

The most common (European) system today has 4 classifications, A to D, but the general idea is the same as the previous 1,2,3 system. Of course the words can be rewritten, detuned or ramped up, but this does not change the technical analysis, or the level of skill required to cope with handling problems caused by turbulence encounters. Certification is based on artificial simulations of set-piece incident scenarios. Having revisited this subject I do not think my comparison with aircraft piloting in the 2009 report far fetched or over the top. Today’s D class notes (equivalent to 3 above) state ‘Recovery to normal flight requires precise pilot input’, and ‘for pilots who accept the implications of flying such a wing’. This is a toned down description of much the same animal, and it reflects more global piloting experience and exchange of knowledge rather than the more benign high performance wing it suggests.

Because there is no such thing as standard turbulence the testing is done in calm air, to achieve consistent results. Stalling and spinning are performed in a similar way to aircraft piloting, and other departed manoeuvres, usually the results of significant turbulence, are simulated by specific pilot action. The end result presents a standard version of the situation that may result from real turbulence: glider behaviour is observed and the response to pilot recovery action, if required, noted. Real life can be very different, especially if pilot action is not correct or not applied carefully enough at the D end, where most high performance paragliders reside.

Pilot-simulated collapse, used in testing and training

The paraglider collapse (wing folding)

The structural integrity of the paraglider wing depends on the downward forces of the lines that support the pilot, countered by the upward lift forces of the wing itself. The spanwise curved shape also provides the outward forces necessary to keep left and right wingtips suitably spaced.

Wing and pilot represent a very unequal two-body inertia system, which has much to do with the dynamic behaviour of the combination. The 90 kg pilot, harness and equipment represents 90% of the total mass. The Spitfire area wing itself weighs less than 5 kg and the 5 kg mass of air inside make up the other 10% of the total, but this large, low mass wing, at such a distance from its stabilising weight hanging far below, has the potential to create mayhem if it were able to maintain its full flying potential under all turbulent circumstances. The partial (temporary) structural failure, presented when part of the wing loses its lift due to a local downward gust, is in fact the paraglider’s safety valve. This is a fortunate fact of nature rather than deliberate intention, and without it the complete unweighted paraglider wing would have terrifying powers of its own. A partial loss of lift raises the restoring forces in the remaining area, and the pilot retains a measure of control.

This behaviour can be largely resisted by timely pilot action, and is generally self-correcting if the wing does fold, the more so the lower the classification level, but, as the classification words above suggest, the pilot skill required to satisfactorily manage D gliders under turbulent conditions is of a high order.

This wing has encountered a downward gust that attempts to fold the left wing. The pilot has resisted this effect by rapidly applying brake, which temporarily increases internal wing pressure. Angle of attack also increases, which will increase dynamic pressure at the air intakes as well as providing additional corrective lift.

Practice and familiarity can only be obtained by flying in representative conditions, with a clear plan of what to do in a variety of situations. Until normal flight has been regained, over-controlling or instinctive attempts to correct the situation by normal flying responses may be very unhelpful.

Performance improvements in the previous 12 years, and their effect on safety

Parasite drag reduction is a major part of performance improvement for all kinds of flying machine, including the paraglider. It means all drag that is not associated with producing lift, and over a number of years the spider’s web of the paraglider’s suspension lines has been considerably thinned out by the use of ever more elaborate load sharing structure within the wing. But this leaves larger spaces between these lines for a collapsed and flailing outer wing section to make its way between a line or two, and get caught there, especially as its natural inflation recovery behaviour may well take place before it has slid itself safely out.

This is a modern beginners’ (A) wing showing diagonal ribs (blue). These improve spanwise sharing of wing loads and allow fewer support lines between wing and pilot. The numerous holes in the rib structure saves weight, and also allows free transfer of internal pressure, especially speeding up the reinflation process when required.

Then we have the other performance improvement: reinforced leading edges. Old school 100% floppy paragliders distorted locally, all the time, under the changes of aerodynamic pressures caused by micro-turbulent air, especially at the hardest working part of a wing - the leading edge. The wing itself, assisted by the pilot with whom it communicated well through the brake lines in his hands, would do its best to compensate for this, but wing section (profile) modifications in flight, together with the pilot’s on-going control activity to keep the show on the road meant that the designer’s ideal lift-over-drag, distance-for-height ratios may not be realised - anything like. Why not sew some thin nylon rods into the front of the ribs to keep the shape? It worked well. But there was a problem: if some of a flailing wing (with its rods) went through the lines it was more likely to be caught up there. This concern was true, and a matter of prototype interest in 2009.

A modern intermediate (B - C) wing. The blue lines are thin nylon rod reinforcements, the triangles extra fabric riblets to maintain a better trailing edge shape. These trailing edge devices also provide longer and more progressively loaded pilot control travel. This improves inadvertent stall protection.

To jump or not to jump . .

If something happens to a paraglider wing a basic rule for the experienced pilot is to resist its tendency to turn - if possible. Once his weight is reestablished vertically underneath the resulting wing configuration, corrective action can begin. This should be done carefully.

The paraglider does not have direct roll control, but the secondary effect of yaw is very apparent due to the 10%/90% mass distribution of wing and suspended pilot. As soon as the light wing changes its direction of flight the heavy pilot far below tends to continue straight ahead, and thus an angle of bank is immediately achieved, quickly resulting in a balanced turn. The pilot flies a larger circle than the wing, and therefore travels at a greater speed, but the statically-stable wing responds to the extra lift demand by increasing its airspeed in the downward direction. The spiralling behaviour of a paraglider is similar to the traditional aircraft’s stable spiral dive mode (unusual attitudes exercise), but this effect is greatly magnified when the lifting area of the wing area is reduced by deformation (some sort of folding which also produces the yawing moment). This heavily-loaded paraglider wing or part thereof performs what may look like a vertical downward roll.

This high g, high speed, high rotation rate, out-of-control vertical dive of a folded and/or cravatted wing is best prevented at its outset, if possible. This implies pilot control on the ‘good’ (lift-producing) side in order to counter the drag on the problem side, and maintain some sort of straight, low energy flight while sorting out the stricken wing with the other hand. This phase of recovery involves delicate and separate multi-tasking by both hands because the flying part of the wing flies at a higher wing loading than normal, and at a higher angle of attack because of the brake control required keep straight and to prevent the spiral dive. In fact it may have to be flown at or in and out of a stalled condition (like a parachute). This is not a natural behaviour of the paraglider which is a wing, not a parachute, and requires careful coordination and adjustment.

[This principle resembles the Concorde technique for escaping a thunderstorm downburst on final approach - encountered at low height, low speed, and a very high drag situation. In purist terms the approaching Concorde is permanently stalled, and this technique called for all the thrust you could muster, and pilot pitch control that flew in and out of stick shake (16½⁰𝞪), whatever the attitude, without reference to airspeed. (There is no magic about 16½⁰𝞪 for a Concorde, and this is 3⁰ short of the stick wobbler trigger, but it’s a reasonable compromise between normal flying and very un-airliner-like characteristics.) The paraglider can be flown (and landed) at 90⁰𝞪, but not by everyone]

At the same time the pilot’s other hand is pulling a choice of lines to help free whatever tangle or hang-up is preventing the stricken wing from reinflating fully. In prototype testing I have seen this achieved successfully after a vertical 5,000 feet of shaking and flapping parachutal descent. From my rescue boat I had long before decided that the chief test pilot would get wet, and was racing to the estimated splashdown point. Not only was the problem sorted at an impossibly low height, but he made it to the landing field. This shows you what a high performance (high aspect ratio) glider will do for you when it flies normally. The example of patient tenacity was something of a tour de force, but you may not have 5000 feet and a lake available underneath during a race.

Enough science: but the high speed spiral dive is the dangerous problem of out-of-control paraglider flight. This chief test pilot has a rule: only throw your reserve if you are in out-of-control rotation; in other words sort the problem out if possible. Advice may be quite different for beginners, and even experienced pilots flying high performance wings may not hesitate to throw if they consider their situation might become out of control. The emergency parachute use may have been unnecessary, but they have this option. Sometimes a paraglider immediately recovers itself when the pilot decides to throw and abandons his misguided interference with the controls. I might add that previous world championship fatals have occurred because high airspeed, g forces and other problems in the spiral mode already described made it impossible for the pilot to physically reach or operate his reserve deployment handle. Twisted lines or pilot entanglements are possible additions to the list.

The fatal accident in the Mexico 2009 world championships happened to a very good pilot who was familiar with the sort-it-out policy described above, but one should consider what is assured if you throw your reserve in a world championship. With one non-scoring flight you will not stand anywhere near the podium. He was expected to do very well, perhaps win, and had countered the spiral that followed the collapse and cravat over the dry and rocky terrain. He was attempting to sort the wing out when renewed thermal turbulence at a low altitude took the upper hand, control was lost and he spiralled into the ground at speed. Should he have thrown his reserve earlier? Hindsight says yes - he was not over a safety lake, nor was he testing at home - but we all know about hindsight.

He was certainly one of my good enough 20%ers, and the initial runaway rotation bailout situation had been recovered. But were the Mexican thermals more gnarly than expected, and how much testing had he been able to make with his made-to-measure personal prototype? Had, historically, the glider characteristics and equipment been as much to blame as inadequate pilot skill and judgment in an extreme and novel situation?

The resulting CIVL decision and its results

Did my elitist (powered aerobatics) pilot selection recommendation have any influence? I’ve no idea, but it may have encouraged a different response to the call for an improvement in safety for this people’s sport: the glider must be made safer.

In retrospect, ten years later, I can only support the paragliding situation today, however this has developed. Natural selection, perhaps? After a year or two of certification compromises, technical development has blossomed with new generations of better, lighter and more user-friendly equipment.

Acro (paraglider aerobatics)

The certification manoeuvres, used as a base for the advanced training syllabus recommended for any pilot, developed into acro, evolving from the early experimentations of adventurous test pilots. This entertaining collection of complex and spectacular figures has evolved into a formal competitive sport, with suitably comprehensive judging rules and adherence to the sporting code. The popularity and dedicated development of suitable acro gliders makes this specialisation available to more, and even a new beginner’s wing will gain favour if it shows itself suitable for basic acro figures.

Has evolution made paragliding easier?

My answer is yes and no. Recent years of evolution have resulted in a great increase in the spread and number of skilled and experienced pilots, at all levels, and a better general understanding of what the certification levels actually mean - when things get difficult. The design field is now more accepting of universal aeroscience knowledge and design technology, and the image of the private and taciturn mountain man with a sewing machine is fading. Yachting-style starting gun racing-to-goal has been superseded by more flexible pilot-controlled starting gate timing, reducing the temptation to fly permanently at a risky full speed if you are not in the lead, in fact all of the above has encouraged more appropriate and universal uses of this incredible flying device. The paraglider is not fast, but it’s portable, you can take it anywhere. It’s an aeroplane in a bag. A look at the recent 2021 RedBull X-Alps race depicts what paragliding is really about, but does this mean it’s become easier, and for whom?

For the beginner perhaps it has. This is better for flying school business, though it may mean that your students escape the training environment sooner. My view is that modern wing performance advances make ‘basic’ extreme manoeuvre training more extreme for the beginner. Historically straightforward stalling and spinning behaviours now require new and quite sophisticated refinements of technique, but you can find many training professionals who disagree (of course they do).

The skill level required by those who reach even halfway to the top of the syllabus is unchanged. My original comparison of aircraft and paraglider piloting skill demands still stands. Very hands-on, in the midst of nature, paraglider piloting can go way off the top of the fly-by-wire Richter scale if circumstances are challenged or unwittingly encountered. Is this a good thing? In evolutionary terms definitely yes. The choice is yours.

But, fundamentally, the natural evolution of this novel sport to date has spread better understanding, skill and maturity of judgment among many more people - as a function of the passage of time. In fact the effect of positive communal experience is exponential.

Paragliding can be demanding, should deserve your full attention, and is an absorbing and rewarding way to take to the air. Could this glimpse at what birds achieve by instinct be something rather special as a challenge for the human today? Actually yes - in spades.

Who can also benefit from this evolution?

You, the reader, can, if you feel so inclined. This two-part essay is written from the point of view of an experienced aeroplane pilot, but the aeroplane pilot should not be dismayed by the references to the life and death reputation of competitive paragliding. That is history, and evolution has improved the statistics a lot. There are many excellent teachers of paragliding, and I advise that you find one if you wish to learn. Any suggestion of bravery, ‘are you up to it?: run a mile, at least (or a couple of kilometres).

The paraglider is a very low energy flying device. Its best lift/drag speed is similar to Usain Bolt crossing the finish line, but you will never have to run at this speed to take off or land. Crashing under normal circumstances could be described as Usain Bolt falling over (worse things can happen in the street). But the progression through grappling with the Spitfire sized wing (on the ground in a light breeze) to getting airborne properly for the first time is an important but brief step to achieving paraglider flight, after which cruising around and landing are much easier than flying a simple aircraft. You will have already learned a lot. You have the choice of learning a lot more, if you wish.