Technical Tips and Articles
This page contains tips and articles that can help solving many everyday problems paraglider pilots faces. You also find here answers to some of your burning questions of a technical character and advice to follow when buying equipment, so feel free to jot down these tips in journals or something to take with you when looking into equipment. They are based on my long flying experience and a deep knowledge of the technical side of paragliding. Most of them have been published in Australian and overseas magazines. I'm doing my best to keep them up to date, but as the sport and technology is developing constantly, it is an uphill battle. Any e-mail alerting me to a redundant erroneous or obsolete content will be highly appreciated. Any material presented here is to be treated as my opinion only and I recommend to use your own judgment before following any of the tips or advices. Also, if you do some more research there are many Paragliding groups and clubs that offer an answering service dallas to New York, as well as other various locations – and they would be more then happy to help as well!
Modification of the T-bar type of harness
There were quite a few fatal accidents and close calls associated with the combination of T-bar style of leg straps and instrument panel. While the T-bar is one of the safest designs if used alone, the combination with instrument panel it can be deadly. A typical sequence of events leading to a fatal accident:
Pilot gets in the harness. Before closing the T-bar he clips the instrument panel on. The panel obscures his view on the buckle creating the "out of sight, out of mind" situation. At the same time the panel puts a bit of tension on the main karabiners causing a false feel of a closed T-bar. The pilot takes off - period.
After this type of fatal accident in Australia a few years ago I designed a modification virtually 100% preventing this possibility. It is simple, costs nothing, it can be done virtually by anybody and it doesn't have any side effects. I've been using this setup for a number of years and I wouldn't get back to the unmodified harness for all the money in the world. Here is how to do it:
Remove the female clip for the cockpit from one side of the harness and stitch it in the middle of the T-bar facing the direction where it was originally.
Do not worry about the sophisticated part on my harness involving insulation tape, it has nothing to do with this modification. I used it to stop the central buckle catching on the zipper of my flying suit ;-). Your setup is ready for a trial. Put the harness on and clip the unmodified side of the cockpit as usual. Now, run the other strap thru the main karabiner and attach it to the clip you stitched to the T-bar. Check if the cockpit doesn't pull the karabiners together relieving tension from the T-bar. If you can't adjust it long enough, you may have to change this piece of webbing for a longer one.
That's all. From now on, you can't clip your cockpit on the harness before at least one of the sides of T-bar (enough to prevent you from falling from the harness) is properly closed. In fact, if you omit to close one side, you can hardly fail to notice it while clipping the cockpit in. You have just made sure you won't become the victim of one of the most frequent causes of PG fatalities.
Risers joining strap
Unless you are a masochist, you don't disconnect your harness from the glider after every flight (I will never understand, why some people do it and nobody ever presented me with a valid reason why to do so). The time, labor, courtesy to other pilots and safety advantages of not disconnecting are obvious and would feel I am assaulting reader's intelligence going to details. The only problem I ever encountered was, time to time I found myself flying with one or both risers twisted. Reason: throwing the harness through the risers at some stage of handling the setup. Twisted risers are not necessarily life threatening - but they don't add to a peace of mind either. It took me about 5 years (yes, that is how slow I am ;-)) to find this solution - and never had this problem since: A small Velcro strap I wrap around the risers immediately after every landing. I remove it again only just before I get into harness getting ready for the next flight. To have it always ready, I always have one of these around my left shoulder strap. After landing, I reach there, take it off and put it around the risers. A foolproof routine, takes about 5 seconds...
Speed bar 'keep up' olives
I know only a few things more annoying than a speed bar banging into your calves while walking around in your harness. A variety of Velcro patches to hold it up proved to me rather short lived solution, as they attract dirt and wear off quickly. The best method I found so far (not my invention, I saw it somewhere and promptly copied) is a little spring-loaded olive (used on clothing and bags) on each of the lines. I pull them down the lines after every landing and they hold the bar off the way. They slide up easily during the first use of the speed system in the air. Comfy!
After experimenting with variety of ways to mount my radio, I ended up with having it at the rear riser. I was thinking about it since the day one - but the bulk and weight of the old 5W unit put me off it. Only the recent introduction of small, light, efficient radios allowed me to go back to the original idea. After using it for about 2 years now, I couldn't be happier. The advantages are numerous. The antenna is vertical and it is not obstructed giving the beast possible performance. The control panel is in a plain view and all operations can be done while holding the brakes. If you are nor really fussy, you can even get away without a headset. The mike is close close to your mouth and it is no affected by wind noise. Warning: make sure the radio doesn't interfere with a free movement of the risers. Also, a heavy radio on the rear riser can affect the recovery characteristic. Ideally, the radio should be attached below the point the risers are joined.
Bundling your glider
Often, when you need to bundle your glider just to get if quickly of the way, you may find yourself short of something to tie the looped lines with. Leaving them lose is a sure recepy for having them tangled. The solution is strikingly simple: put the wingtip thru the loop...
It is always better to leave a paddock thru the gate. If you find a padlock on it - well, you have no choice. Besides of trying to your best not to damage the fence you also don't want to get zapped by the electric wire. It hurts! Your problem can be solved by about 30 cm of wire (doesn't even have to be insulated) with crocodile clips. I never leave home without it! Before climbing the fence, I clip one end on some non-active metal part of the fence and the second (the sequence is vitally important) on the live wire. When safely on the other side, I unclip the 'live' end - again, the sequence has to be right - and then the other. Simple and painless, doesn't harm the electric fence either..
Brunnel Hooks on your speed system keep separating on takeoff?
A simple help: a piece of inner tube from a racing bike (or any other rubber pipe of similar diameter and flexibility) and a small cable tie. Pictures explain the rest.
The hooks will not separate on their own ever again and they are as easy to connect and disconnect as before.
Press Studs on your brakes get hard to separate?
I tried just about all the lubricants you can think of and none of them worked properly - until I came across a graphite powder. I'm not searching any further, this stuff works magic! Just one application and you will not recognize your old press studs. It typically lasts a whole season. The powder is available from auto parts outlets like Autobarn or hardware shops.
In the dark ages of paragliding some 12-15 years back) manufacturers were holding a serious competition who presents the most impressive performance data in their glossy booklets. Speed was the most popular parameter to stretch closely followed by glide and sink rate. According to these some paragliders were closing fast on the 60km/h barrier then already! The race was fierce and every argument possible was used to support the crazy claims. One of the renowned companies followed the speed data for their prodigious baby with measured by GPS statement. Quite entertaining! One of the reasons anybody was able to claim anything was the fact, the performance data are very difficult to obtain or check. There are too many factors in play and even the most honest manufacturer can slip by miles from the real figures. It gets worse: there are no fixed standards to be followed while obtaining this data and even while using the same instruments the figures obtained by different testers can vary substantially. It can be due to a different environment or some other parts like harness or pilot’s clothing. I don’t want to go into details here; if you want to get a better idea how complex this issue is, look it up in the Paragliding Forum . Prepare yourself for a long reading and a few surprises.The situation has stabilized greatly over the years and most of the figures manufacturers are presenting us with now are at least quite realistic. Still, I would advise using a great caution while using them for comparing gliders in the same category. The differences between the performances of gliders by the top manufacturers are so small, it is virtually impossible to measure them reliably. Even if the claimed difference exists, using it as main point for choosing your glider is rather pathetic. Some manufacturers are better at creating number-hypes about their gliders than others. If they tell you their glider has 0.3 better glide than anything else in that particular category, it sounds impressive. It can be actually true – but let’s put it in a perspective.
Fig. 1 is showing different glide path with different glide ratio – the angles are true. For simplicity I used glide 10 (realistic for the contemporary comp gliders) to illustrate my point. The 0.3 extra gliding ratio has some noticeable effect in the region of 4 or less but it becomes insignificant in the 8-10 area. On a 1km glide it gives the “better” glider 30m (just over 2 spans of you glider) longer path – a difference that can be negated by anything - like less effective takeoff, less aerodynamic harness or even body position. If the extra gliding ratio is really there, it is certainly a sign somebody has done a good job in this best glide area – but nothing more. The advantage in the real world is rather academic. Besides of being truly miniscule the “guaranteed” benefit in the form of a longer flight path is only in the best glide configuration (usually trim) used in absolutely still air. How often do we fly in conditions like this? We are totally in the dark what will happen when the wing is being flown with a speedbar or some brakes – and that is what is happening in the real world. A lot of surprises can be hiding here. Only the whole polar curve can answer our questions. But, you can guess: if a single piece of performance data is hard to obtain, getting enough information for constructing a reasonably accurate polar is virtually impossible. The generic curves presented on the Para 2000 website are probably as accurate as they can be – and that means “not too much”. It is easy to prove how ridiculous the attempts of achieving one or two decimal points accuracy are. I had a closer look at the data published on Para 2000 for two recent gliders (according to the manufacturer each of them the best performer in its category) and found these discrepancies: the first glider has in the “best glide” box numbers 9.2-9.5. Fair enough. But: only 2 lines up there is speed and sink rate at the best glide: 39km/h and 1.1 sink. If you calculate the glide from these figures the result is whopping 9.8! In the case of the other glider it works the other way round: the claimed best glide is 8.9-9.2 while the one calculated from the speed data is meager 8.5!
If you want to see a more practical example, look at fig. 2. You can see 2 tracklogs there from one of the major competition last year. One is by a 6 years old glider where the manufacturer claimed a modest 8.5 glide, while the other is by the latest (and, according to the manufacturer, the best performer in the 2-3 category) machine with glide about 9.3! Sorry, I can’t tell you which one is which because the gliders flew virtually abreast for the most of the task. The winner could hardly claim his better gliding ratio had a major part in the final result.
Now, to make sure you understand me correctly: I’m not saying the new glider is not better. I’m saying it is extremely hard to turn the higher efficiency figures alone in a practical advantage. Trying to do it on the base of higher numbers at the first or even second decimal place is a joke.
Considering the above facts one may finally appreciate this disclaimer on the website of one of the major manufacturers:
“The performance data presented here are for general information only and by no means should it serve for making comparisons with products by other manufacturers. The methods for obtaining this data vary and there are no fixed standards. Any comparisons based on this data can be misleading.“
There is hardly a month in the year you wouldn't hear about at least one flight that makes you turning green with envy. Pilots flying hundreds of kilometers, staying in the air for hours reaching stratospheric altitudes and crossing stretches never crossed before. Also the sheer amount of airtime over a period of time achieved by some pilots can be awe-inspiring. It all makes you wondering: why them and not me? A truly great flight is almost always result of the rare combination of skilled pilot superior equipment and excellent weather conditions - not necessarily in that order. If there is some deficiency in any of these areas, it has to be balanced by some extra strength in the one or both others. There are situations, where magic air carries a poorly equipped pilot of average skills to exceptional distances - or you see a genius pilot with average equipment going places in average conditions. These flights are the exceptions of the rule and I don't know many cases of world records achieved on this type of compromise. In short: everything has to click.
How can we help it? The skills and equipment ingredients are fairly straightforward: work on your skills and borrow steal or buy (if you have no other choice) the right equipment for yourself. It is as simple as that. The 'Perfect Conditions' ingredient is the hardest part. We are talking weather here - and it involves (besides of a sound knowledge of meteorology) a serious amount of luck, black magic and a crystal ball. In the end it is mainly a game of numbers. The more often you try, the greater are your chances. It is extremely unlikely pilot would achieve anything really exceptional unless he (she) makes paragliding his (hers) lifestyle. Full time job, a family (not to mention the combination of these two) is a serious hindrance consuming too much of one's valuable time that could be used for flying. For most people carrying those burdens is trying to catch up with the sky gods a futile and frustrating exercise. In most cases it ends by contracting AIDS (Aviation Induced Divorce Syndrome). The inability to be at the right place at the right time often enough presents a compounded problem: it statistically reduces your chances and it also deprives you of the opportunity to acquire the coveted superior skills. Set realistic goals that fit your situation. If you work from 8 to 5 and live somewhere in the inner suburbs, it is not likely you will ever make one of those epic flights the PG bums living close to the prime sites are doing just about weekly. If it does happen, count your blessings and mark that day by a red ink in your calendar.
Your problem is not so much a lack of time in the absolute value. The keyword is 'Flexibility' - the ability to hop in the car and go flying when the conditions look right and do your work when you can't fly. If you live close to a good flying site, the total time you spent on paragliding may not be too long and it may be fairly close to your airtime. There even may be enough time left to do some serious work (to earn enough money to feed your paragliding addiction) as long as it can be done at night or something. That's why the bulk of the active pilots are known to work in the IT industry or fill in the box 'occupation' something as obscure as a 'company director'. But not all of us are in this enviable situation. In most cases the best you can do is to reduce your driving/flying ratio.
A system introducing some efficiency in your time (and money) management is more important than the efficiency of your glider. Here are some tips I can offer from my long and frustrating experience: Use only one source of weather forecast and use it every time. Change it only if you find it EXTREMELY unreliable over a long period of time. There are many sources available and NONE of them is 100% right. Gets worse: they often vary significantly in their predictions. If you regularly browse thru them, you always find what you subconsciously want to see: either a good reason to go flying - or not to go - depends if you are pessimist or optimist by nature. Eventually, you end up either doing an enormous amount of driving and, yes, hooray, you will also log some airtime - but you will have to extend your hydroponics grass plantation to cover the cost - or you simply will never go anywhere and will sell your gear by the end of the first year. The idea is to stick with one (it almost doesn't matter which one) source of forecast and go flying whenever (your circumstances allowing) it promises good conditions. You will be surprised to see that even the worst source of forecast is about 80% right! Another rule is: Work with the forecast, don't wait for the observations to be right. This is especially important at the coast, where the flying conditions rarely last more than 2 or 3 hours at a particular site. Unless you live 15 or so minutes from the site, waiting for the weather stations to show the right stuff, then drive there in a hope you will have a great time is a waste of time and money. With all likelihood you will arrive just to watch everybody landing because the show is over. Your best punt is to TRUST THE FORECAST (I know it sounds insane) and get on your way well before the conditions start to appear ideal. You may spend some time parawaiting - but most likely you'll be rewarded eventually. Making a 100 or more km trip and go home with no flight under your belt is infuriating. Make sure it won't happen too often. On the other hand, learn to live with the fact it just has to happen sometimes. If the flying site is more than some 200 km away, try to avoid one-day trips. They seldom pay off. You really want some margin in the case the first day turns bad. With the current prices of petrol a cheap overnight stay usually compensates for the cost of an extra trip, not to mention the stress of long driving. Ideally, try to get yourself a retrieve driver, but I'm really stretching my imagination here. Most of us have to cope without this luxury.
Polishing your groundhandling skills is another vital part on your way to great flights. There is nothing more frustrating than being at the right place at the right time (finally!) and not being able to peel of the ground. I've seen this situation too many times - and believe or not, I don't laugh watching it. It is not funny. But, it is almost always the pilot's fault and he (she) is the only one to blame for the frustration and waste of time. If you live under the impression you finish your course and then you just go and fly, you are for a big disappointment. Paragliding, especially the first 20 or so years, is mostly about learning trying falling etc. Flying comes just as the icing on the cake. Don't miss a single bit because of your inferior groundhandling skills. Practice as often as you can. The beauty of it is, it can be done in much wider range of places and conditions, so there is no excuse. If you apply the above tips, you may be surprised how fast your airtime will start accumulating and in some time you will also find a few flight in your logbook to brag about. The main thing is to persist and not to give up. One doesn't have to fly hundred hours a year or break world records to have a real pleasure from our wonderful sport!
We all know these pictures from our license course or some paragliding textbook. We take for granted they are correct – after all, they’ve been around for some 30 years. I admit, I never gave them a real thought. They were drawn by the top brains in the paragliding industry, so, why not just accept them as they are?
A certain gentleman from Scotland suddenly popped up on the Xtreme Big Air forum, stating, they are all wrong! What part? Well, in his opinion, the wing should be pitched down – not up as all these drawings show. An idea almost blasphemous. Denis Pagen can’t be wrong! Or can he? A heated discussion on the Internet ensued and it is still going on. “Can wing maintain a steady glide with a positive pitch?” No light at the end of the tunnel.
The best way to find out it is to go and see. And, if you look at a paraglider in a steady flight, you will believe the drawings are right. The wings are showing a distinct “nose up” position. So, no wonder we don’t see anything strange on these drawings. They only depict it the way we can see it.
But let’s analyze it a bit closer. Can wing maintain a steady glide while being tilted upwards? To simplify things, let’s replace the cambered wing with a flat sheet of paper. If we let it fly, the only factor determining the direction of its flight will be its pitch. This “wing” will always move in the direction of its lowest point. It will always fly with a negative pitch! In a simplified view, it is a case of 'action and reaction'. While the plate (wing) is being moved down by gravity, it 'spills' the air over its highest edge. It is necessary to understand, the top surface has its role in this process as well (becomes significant in a cambered wing). Reaction to this air movement moves the wing in the opposite direction.
Illustration from ABC of paragliding by H. AupetitThat puts some smoke screen over our observation of a paraglider and it is time for another experiment. I made an improvised spirit level and fitted it to the bottom surface of my canopy. After I took off and established a steady glide I looked up and even took a few photos. Surprise surprise! The bottom surface was distinctly tilted nose down. This experiment confirmed my suspicion: the way we see paragliders pointing up while watching them from the side is an optical illusion! A strong one and very convincing too. I had to repeat this experiment a few times with different gliders to convince myself I really can’t trust my eyes. But I’m sure about it now: despite of what I seem to see, paragliders (at least the ones I tried) in a steady glide have the bottom surface tilted down. The drawings in the textbooks are based on an optical illusion!
Now, let’s get back to the great dispute: 'can wing maintain a steady glide while having a positive pitch at all?' Why all the participants in that endless discussion can’t find a conclusive solution to such a trivial problem? The answer is strikingly simple. The QUESTION IS WRONG – and nobody can find a correct answer to a wrongly formulated question.
First, we look at the definition of pitch: “Pitch is the angle between Chordline and horizon.” So far so good. Now, what is “chordline”? Chordline is the “line drawn between the most distant points of the wing profile.” Ops… something not quite right here. Does the bottom surface of our wing represent the chordline? Catch No. 1: it does not (in most case anyway). So, we can’t use the bottom surface neither for visual nor exact (spirit level) measuring of pitch angle.
Catch No 2 is even worse: chordline is a meaningless reference too – it is purely an engineering (or geometric, if you want) term, but it has no relevance to the aerodynamics of the wing whatsoever! We started to use it in the dark ages of aeronautical engineering and somehow forgot to fix the mistake. As a result, we can now see certain wing profiles that still produce lift at negative angles of attack – something what screams “WRONG” at the first glance. The reason for this oddity has nothing to do with physics (or rather pseudophysics). We simply used that convenient but aerodynamically meaningless chordline as a reference for angle of attack. If we want to start to see some sense in our numbers, we have to use the “absolute” angle of attack term. In this case we relate the angle to the direction of relative wind that produces zero lift. Finally, to our relief, we see “zero lift” at a “zero AoA (absolute)”. Uf…!
In the picture above is the (guestimated ;-)) 'relative wind producing zero
less down than chordline. But, depending on the wing profile, it can be vice-versa as well.
If you move glide path angle in our picture between chordline and the direction
of relative wind producing zero lift, AoA will be negative - but the wing will
still produce lift!
Now, let’s get back to our pitch. In the light of the above, pitch, the way it is defined (or the way we can see it) has nothing to do with the aerodynamics of a wing. So, the question if it should be negative or positive is entirely meaningless. The only case where it makes sense is a flat or symmetrically cambered wing. In such a wing chordline coincides with the direction of the relative wind producing zero lift. And, yes, for a gliding flight pitch has to be negative in this case. It simply determines the direction of flight.
In all other cases it all depends on the wing profile. With the “right” profile glider can fly happily with a positive “pitch” as pitch is conventionally defined.
Where is the difference? A question I can often hear from beginner pilots after they manage to keep their pace with some of the hottest gliders around. This situation is not uncommon. During a simple ridge soaring inside a small bowl there is little more at play than sink rate. A beginner's canopy being flown at the bottom of the weight range can come very close to a performance glider being flown fully loaded. The trim speed will most likely be almost the same as well. While thermaling over a small area the situation will be very
similar. Pilot's skills will show here more, than the performance of his glider. Now, really: Where is the difference between the DHV (German categorigasation generally recognised as a norm worldwide) categories?
Don't worry. It is there - for everyone to see when it comes to crossing gaps - especially in headwind. As soon as the pilots set for a glide, some interesting facts will surface. The easiest way to show the truth is to look at the polar curve of each particular category of a paraglider. If you can't read these, you'd better do something about it. It is simple, anyway.
Curve A is a generic curve of a modern beginner class paraglider, typically rated DHV1 or EN A.
Identifying features: About 30 cells, aspect ratio around 5.0, thick material, thick lines - smart pilot. The whole thing has 'stability' and 'durability' written all over it. As there is no such a thing as free lunch, it will show some deficiency in the performance department. But as we have seen above, for a beginner or an occasional pilot it doesn't have to be any great disadvantage. The stability of their gliders can pay well off.
Behavior: Docile. This thing doesn't bite unless you seriously abuse it. Virtually no active control needed. Have a nap. If you try to do something wild, do not be surprised if it refuses to do it.
The polar will reveal most of the secrets. The min. sink of some 1.3m/s is at a speed very much in line with the other categories - 28kph. On the left there is a nice, not very steep arch leading to a stall point. The speed span between these two is 8kph. A great safety feature! To the right we have the best glide of 1/7.5 at 35kph. Not bad at all for a glider as stable as we have. This point is usually the trim configuration as well.
We were doing OK up to here. Now we are getting to the moment of the truth: We step on the speed bar. A steep arch to the right of the right of the best glide doesn't look too flashy. It ends at a Vmax of about 46kph and an alarming speed rate of 2.5m/s. The glide would be 1/5 here. A quick glance at the polar of a competition glider ('C') reveals, its pilot is barely tickling the speed bar at that speed, his sink rate is still only 1.2m/s and his glide is almost unchanged! The most noticeable difference would be in a headwind of 46kph. Our ugly duckling will get sadly stuck, going nowhere. The pilot of the comp widow maker still can get groundspeed of some 16kph!
Polar 'B' is a signature curve of a Performance Class canopy, rated DHV2-3 or EN D. (For simplicity sake I've omitted the Sports Class, which is the favourite of intermediate pilots. This, obviously, falls somewhere in the middle between beginner's and performance. These are rated DHV1-2 or DHV2 - EN B or ENC in the new system)
Identifying features of the Performance Class: About 50 cells, aspect over 5.5, thin profile, thin lines - a fairly impressive looking machine. Its pilot should sport the 'Advanced' sticker on his helmet if he should be called 'smart' as well. Going thru a SIV course before flying one of these should be a matter of common sense.
Behaviour: In a ridge soaring situation no special skills are necessary. A bit of caution while trying to do something more radical is needed. This wing may be responsive beyond your expectation - this is one of the most frequent ways of getting hurt by these. Inland - a good degree of active flying is needed. This type of wing may not collapse too easily IF TREATED RIGHT. When they do, they expect some help with recovery if it should be reasonably swift. Will punish severely any pilot, who doesn't give them what they need. A 'cascade' type of accidents is common as a result of overcorrecting a super-responsive glider in critical situations.
The polar is more interesting. The back of it is similar to the one of the previous. Anybody capable of stalling this wing accidentally deserves what he gets. There is a wide, hard to overlook margin. Min. sink is again around the speed of 30kph but it is only about 1.1m/s. That's nice! From here the polars gets much flatter through the best glide (often trim), which may be at a speed marginally higher than in the beginners class. But the glide is very impressive indeed: 1/8.5! Then it continues, bending only slightly, to the Vmax point. At a tad over 50kph it will still sink only 2m/s. This is about all the performance a serious CX, non-comp pilot may ever need.
Polar 'C' is that of a serious, latest generation competition wing. Safety rating: open class, no DHV certification.
Identifying features: Seventy or more cells, aspect ratio of about 6.5 and a dental floss for lines. If you realize what you are looking at, you should get goose bumps right away. A VERY recently re-packed reserve is an essential part of the package. The pilot's face should be known to you from some glossy magazines. He is likely to be sponsored by a major manufacturer. Alternatively, he might be an escapee from a nearby mental institution.
Behavior: This glider eats average pilots for lunch. Even in the coastal condition this widow maker can show to the uninitiated what it has in stock. Just a fast release of the speed bar can lead to a steep climb ending by stall. Inland - definitely - 'For Sky Gods only'. It will collapse easily even under the best management and refuse to recover without a substantial expert help. The rewards: high speed, enormous glide ratio and ultra-high agility.
The polar should put you off at the first glance of it. The back part of it is especially nasty. A sheer drop from the Min. sink (under 1m/s!) to a stall takes only 4kph. Any odd puff from behind while having brakes a bit deeper - and you are in a serious trouble. This is the product of a high aspect ratio, needed for the mind-boggling best glide of 1/9.5+. The gentle arch leading to Vmax of 60kph+ is achieved by a highly unstable profile and almost invisible, unshielded lines. Notice, that even close to its maximum speed this marvel of technology still has a gliding ratio matching the best glide of a beginner's paraglider! Very inviting - but unless you are a true professional - give it a wide berth!
The mechanics of flight is not as simple as you might think
after finishing your license course. In fact, it is so complex that a lot in
this area is still to be discovered. As there is no need for a recreational
pilot to have a deep knowledge of physics, we have a few of popular explanations
that give a nice simplified picture of the interaction between wing and the air. You probably know the one using the
difference between airspeed at the flat bottom of a wing and over the
top, cambered surface. Makes sense, but as most of these simplified
explanations, it has its catches. For instance: how do you explain inverted
flight? What about a paper aeroplane – Look mum, no camber! – and, boy, doesn't
it fly!? You are stuck.
In fact, the whole ability of a wing to provide lift has more to do with angle of attack than the shape of the wing. Even a brick will fly if subject to airflow strong enough striking at the right angle. The soundest and probably easiest to comprehend explanation of the function of a wing is the one based on the “action and reaction (Newton's)” principle. It has very few weak spots and a very sound and accurate mathematic backing. Oddly enough, this story is the best to start with helicopters. It is being traded among pilots that these things are simply so ugly, the earth repels them - and that's how they fly. There can be something about it – but if you ever found yourself under a hovering helicopter, you might realize the downdraft could have something to do with their ability to fly as well. The huge stream of air is hard to ignore – especially if you are flying a paraglider at that time. It is easy to imagine the rotor of a helicopter as a big fan accelerating air down. To do so, the rotor has to apply a force to the air – that induces a reaction force of exactly the same size, lifting the chopper up.
What has a fan to do with a wing? Well, the blade of a helicopter rotor IS a wing! Only, it moves in a circular motion eliminating the need for the whole machine to move thru the air. Otherwise the principle is exactly the same. As any other wing the blade can even stall – surprise, surprise – if the chopper flies too FAST! In that case the retreating blade (the one moving backwards) loses its airspeed, the angle of attack increases over certain point and the blade stalls!
Wing of a fixed wing aircraft does exactly the same what the rotor blade does: while moving thru the air, it deflects it downwards. The accelerating force induces reaction we call lift. Why this is not so obvious in a fixed wing? Unlike in a hovering helicopter, this wing deflects a parcel of air and moves forward to deflect another one at a different spot so the belt of sinking air doesn’t reach very deep. You would be surprised: the downwash from a fast flying chopper is not any worse than from an aircraft of a similar size traveling at the same speed. As soon as chopper starts hovering, one parcel of the deflected air has to displace the one below and so on – the result being the typical fast dropping column of air under the rotor. Our wing is nothing but a pump pushing air down (action) and receiving lift (reaction) in return! Obviously, it needs energy to do the job, but that’s another story.
How fast should I fly? That's a burning question pilot starts to ask when he wants to get as far as possible as fast as possible. This issue is simple and complicated at the same time. The simplicity is in the fact, all the answers are in the polar curve. The complications come with the fact they are, in its raw form, valid only for a still air. To make some use of polar curve in a real life, we need a whole set of data about the air we are flying in: its both horizontal and vertical speed, direction of the airflow and its relation to our path. To obtain all this information we need a lot of hardware: vario-altimeter, GPS and an airspeed sensor. Processing the data fast enough to make them useful in real time is task for a serious computer. There are instruments on the market incorporating all the above. They are not cheap and require a lot of attention from the pilot during his flight. Before investing in one of these, an average recreational pilot should spend some time studying the polar curve of his machine and get some understanding of the principles involved. It can improve his flying dramatically. Polar curve is a graph showing the relation between airspeed speed and sink rate of a particular glider. It is of a roughly parabolic shape. The flatter and longer the curve is, the more efficient is the wing we are dealing with. The polar curve of a paraglider stands out from other flying machines like a sore thumb. It is short and looks like a camel's back. Yes, paraglider is a bit of a dog. A good reason for us to try to get the most of the little performance this contraption can offer.
Fig. 1 is is a typical polar of DHV 1 or low DHV 1-2 paraglider. Tangential line 'G' reveals the best glide point of the curve and the best glide angle. The gliding ratio in this case is 1:7. A line from '0' to any particular point of the curve reveals the glide angle for that point. Easy!
But, wait! All this is true in relation to the block of air we are flying in - or to the ground if the air is perfectly still. What about wind, lift and sink? If these conditions exist, we have to move the polar to get the ground-related data. It involves a bit of work. Print the picture above first on a normal paper. Then once more, on a transparency. Replace the polar (only on the transparency), if needed, by polar of your own glider. Now, let's say, you want to know how to get the best distance in 10k/h headwind and 2m/s sink. Move the transparent sheet so that the 'lift' line crosses -10k/h and the 'speed' line crosses -2m/s on the paper. Draw a tangential line line from the '0' on the paper to the polar on the transparency. Bingo! You have to fly at airspeed of 46 k/h. Your gliding ratio will be rather disappointing 1:2.5. Not too inspiring, but true... Play with this setup to simulate different situations. One surprise will follow another, I'm sure. Remember: read the ground-related data from the paper, the air-related ones from the transparency. Another point to realize is, the 'lift' and 'sink' numbers are not what your vario tells you (unless you have it set on 'net') and you have to compensate for the sink of the glider at any particular point of the polar. Have fun!
There is a long history of radiocommunication in the HGFA and while we are making progress all the time, our communication still has a lot of room for improvement. Very much from the beginning we were using UHF CB radios because of their compact size short antennas and the citizen band sector being free of any license requirement. While there are channels allocated for us on the VHF Airband, a wide use of them can’t be expected because of the high cost and license restrictions. There is only a small part of our flying where there is a legal requirement for their use. A majority of the HGFA membership never gets in these situations and UHF will remain the main means of communication for our everyday use.
All was going reasonably well, until due to the increasing popularity the CB sector became overloaded making it virtually unsuitable for any practical purposes. We are especially exposed to radio channels congestion, because of the altitude at which we usually operate. It provides a long line of sight and that is how UHF signals propagate. As a result, were are receiving all the chatter by hikers, truckies or just children playing with radios from over 100 km radius. It is not only annoying, but it also makes picking up the significant messages all but impossible.
HGFA went to the rescue and a few years ago purchased mobile land channel for exclusive use by its members. It was a good idea, but there is a dark side of it as well. To use this channel and the 4 CTCSS subchannels you have to have a professional UHF radio. A cheap dedicated CB transceiver available from Dick Smith or Jaycar Electronics won’t do the job.
By coincidence, at about the same time the technology made a quantum leap forward in the CB radios and CTCSS (tone squelch) became a standard feature of even the cheapest CB units. This feature opened the possibility of dividing each of the 40 CB cannels into 50 subchannels increasing the number of choices to 2,000. Shortly afterwards new Australian Standards for CB radios were issued increasing the number of open CB channels to 80 by halving the channel width from 25 to 12.5 kHz. With the use of tone squelch this pumped up the number of available choices to staggering 4,000. This number enables virtually anybody to find his “own” free channel for an interference free communication – unless somebody makes a deliberate effort to annoy you.
Does this make the HGF channel redundant? Not really. Schools, instructors conducting special event and comp organisers often want to have a GUARANTEED interference free communication and that will never be possible on a frequencies segment available to general public. But, it is safe to say, for an every-day recreational pilot the CB sector provides all what he can ever wish for - if he uses it correctly.
Unfortunately, we still seem to have a long way to go in this area. There are a few points that are not properly understood and we are encountering problems that we don’t have to. The mysterious “tone squelch” feature is a typical example. Also known under the acronym CCTSS, it is not a magic bullet. It doesn’t really divide every open channel in 50 “subchannels” as it may seem. It doesn’t stop the radio receiving any signal using the same carrying frequency. It only monitors the already received and demodulated signal and decides if to open audio or not. And that is the main limitation of CTCSS.
CTCSS is ideal for filtering off weak distant stations that would normally cause a nuisance. Radio using CTCSS receives them, but doesn’t open audio because a specific tone squelch is not included in the demodulated signal. If there is another, much stronger signal detected, your radio will start receiving it instead and if it contains a specific tone squelch, it will open audio. Tone squelch is less perfect for separating communications of 2 or more groups in the same area. Example; you are in a busy area and in contact with pilot who is at some distance already. All goes well, until somebody in your vicinity starts transmitting on the same main channel using a different or none tone squelch. Your radio will immediately lock on the stronger signal, ignoring the station you were communicating with. The worst thing about this situation is, you won’t know about it. You simply don’t hear anything (audio is disabled) and you may as well assume your partner has stopped talking to you or got out of range.
For this reason using the same main channel by two or more groups of people in the same area should be avoided. Some organisers of special events are doing exactly the opposite, for the worst possible reason of all: because THAT main channel is BEING USED in THAT particular area! The HGFA channels obviously suffer from the same problem. It is not a good practice more than one group using them at the same location. The HGFA channel and subchannels are recommended to be programmed with “transmittion blocker” (radio won’t transmit if it detects traffic on the same main channel), but not all radios have this feature. The best option for event organisers (if HGFA channel can’t be used) would be selecting a “club channel” (we have at least 10 of them in Australia) from area at least 300 km from the venue. It would cause no interference and it would be easy for the participants as well; they will have it most likely pre-programmed in their radios and they won’t have to test their skills at radio programming. Again, some event organisers insist on choosing some channel/tone squelch combination from the top of their hats. These do not offer any technical advantage and only make life harder for the participants.
There is also a lot of confusion about the legality of radios being used. In reality, it is as simple as this: your unit has to be compliant with Australian Standards 4365 for CB radios. The compliance has to be confirmed by a sticker similar to the one on the photo, normally located in the battery compartment. No sticker, no compliance. The radio is not legal, no matter how much its features may be technically matching AS 4365. ACMA (Australian Communication and Media Authority) is a law enforcement agency with powers matched only by police force, customs or ATO. There are multi-thousand dollar fines and even jail terms at their disposal for enforcing Australian communication laws. You don’t want to cross their wires.
Fortunately for some in our community, ACMA is undermanned and overworked. Being responsible for all TV and radio broadcasting, Internet, mobile phones, radio communication etc, CB radios are on the fringe of their interest. But, as the use and abuse of them is growing, it is only matter of time before ACMA will step in. Some “helpful” individuals around are selling “bargain” PG or HG radios to unsuspected customers exposing them to serious legal consequences. Yes, you do can get fine of a few grand just for being in possession of a gizmo like that! These people, obviously, don’t advertise their illegal products believing they won’t be caught that way. A rather naive assumption, nobody can keep cheating the law forever. I suggest checking any radio you have purchased recently for a sticker similar to the one here.
If it is absent, you have been taken for a ride. Go to http://www.acma.gov.au/theACMA/equipment-compliance-and-labelling-complaints and report the case. Request a full refund from the merchant as well. The merchant will be ordered to issue a recall by ACMA anyway but it may take some time. By acting early, you may find him still solvent before he spends all his money on fines and legal fees.
Another problem is the physical setup of you radio. Any piece of equipment that in order to be operated compromises the control of your aircraft is a dangerous piece of equipment. Try to dispute this statement... A bare radio, no matter how good it is, is exactly that. It may be perfectly suitable for your retrieve driver (if he is not using it while driving that is), but to use it safely and effectively in the air you will need some specilised accessories, namely headset and ideally also a finger-mounted PTT. If you are contemplating buying a radio, check the availability suitability and price of these bits and pieces and make sure you take it in account while making your choice.
When you have all what you need, pay a close attention to a proper installation of the accessories and mounting of the radio. Having it at a spot where you can operate at least the channels selector and volume control is essential. A part of the conditions for use of CB radio is, you have to check the receiving indicator (usually a blue LED) before you transmit. It warns you, the main channel is being used by somebody else if you are using the CTCSS filtering. If this indicator is not in your sight, you can’t comply with this condition and you can become a major nuisance for all other users in a wide radius. Also bear in mind the UHF signal is, by agreement, vertically polarised. If the antenna is off vertical more than by a few dg, you are seriously reducing your range TX and RX as well. In my experience the best location for the radio is the rear riser of your paraglider. Make sure, it doesn’t interfere with its control though.
As it is obvious from the above, there are actually some rules to be followed in the CB world. Just to mention a few:
1) At least 90% of your transmittion has to be human voice.
2) Re- transmitting a signal received from another source is prohibited.
3) A continuous transmitting must not last more than 3 minutes. There has to be an automatic cut-off timer (TOT) to assure adherence to this rule. If there is somebody who has PTT locked continuously (the most common and serious disruption of communication on our flying sites), you know he is using a non-compliant, illegal transmitter.
4) The transmitter power must not exceed 5 W – again, this rule can be broken only by a non-compliant device. BTW: using the low power setting (usually 100 mW) will give you a shocking range often of 20 km or so. This setting saves battery power and also will cause less interference to distant users. Use the full power only for extreme distances or when on the ground. There is nothing unusual making contact at over 200 km air to air distance using 5 W output.
5) Surprisingly, you are allowed to swear and use coarse language as you would do in a normal verbal communication. However, you are not allowed to transmit messages likely to seriously affront somebody – racist or sexist comments for instance.
6) Do not use repeater (duplex) channels for simplex communication and duplex channel 5 for anything but distress emergency calls. Channel 5 duplex is being monitored by volunteers and some emergency services as well. It has a broad coverage and often it may be your only life line in case of accident.
All the above comes from AS 4365 and unawareness of these rules is no legal excuse for breaking them. Paradoxically, the standards are not available to general public and you have purchase the issue if you want to know more. Gets worse. I would be actually breaking the conditions of my license if I copy the exact phrasings from the publication. Rather absurd, but again; if you have a compliant radio, its user manual has to contain all the points of concern specified by Australian Standards.
To summarise; we have all the technology at our disposal to make our communication safe and effective. A bit more of education in this area would definitely help and HGFA should pay more attention to this matter.
In our sport we concentrate heavily on the safety of our equipment – for a good reason. Anything going wrong with it can hurt. Comfort seems to be a secondary issue and however we find flying in comfort more pleasant; we may not pay enough attention to small details. Sometimes, it may turn against us in a nasty way – if we like it or not, comfort and safety are closely connected. Example - how many times you lost direction, almost running into somebody while trying to adjust your harness? Never? Well, either you are a prodigy or you are fooling yourself.
Once in the air, you want to have everything at the right place, accessible and comfy. You don’t want anything restricting your movements and visibility or having to perform contortionist exercise to get to your radio or drink. Some people are getting more annoyed by discomfort than other. I, unfortunately, belong to the group of people who have to have everything a 100% and wouldn’t stop until they have it. A zipper on my flight suit scratching my neck can spoil my day to the point I rather land if I can’t fix it. Some of these nuisances can be detected during a pre-flight check. Some you can find out only when you are airborne and it is too late to do anything with it for the duration of the flight. In that case it is important to take a mental note of it and make a firm resolution: “I will rectify that bloody problem before my next flight.” I admit I sometimes don’t keep that promise given to myself – just to regret it bitterly later. Often the excuses can be: “It is not going to happen again.” For instance, the cable to my headset kept getting caught between my body and the flightdeck every time I got in a landing position in my harness. Not a major problem – until you find out you can’t lift your head to look upwards. Every time it happened, I was convincing myself it was an odd chance not likely to be repeated. And indeed, whenever I tried to achieve it under simulated conditions with the harness suspended from a beam, the cable ran free every single time. Obviously, I forgot a small detail – the relative wind. Anyway, I allowed this nuisance to spoil my whole season before the cable finally broke. Replacing it with one 10cm shorter took me 15 minutes… Problem with any cables getting under tension in some situations should be solved ASAP for the sake of the cables and the gadgets they connect as well. Something is going to snap eventually causing problems during the flight and incur some expenses later.
Besides of the above mentioned cables the most common sources of discomfort and distraction are – besides of ill fitting underpants (very serious):
Poorly fitted or designed instrument panel. If you have to fiddle with it each time you want to look at your instruments, it is time to do something about it.
Radio at a place you can’t see or operate it comfortably. Especially if you have to reach somewhere to press PTT, the radio can bring more trouble than benefits.
Camera - a cool pilot is not complete without one. Just getting it from your pocket in flight is often source of a major distress, not to mention taking pictures and then trying to put the camera back. If you want to use camera, make sure you are well organized. Video cameras fitted on various parts of your equipment is becoming wide spread. Beware of the safety issues, as these tend catch lines during collapses. A helmet mounted camera is the worst and it should be avoided like a plague.
Ill fitting helmet. Helmet should fit snugly without moving around on your head or, on the other hand, causing headaches by being too small.
Zipper scratching your neck. I find this one especially distractive. A neck warmer is not only good for your health, but it will also deal with this nuisance.
Ill fitting gloves. If too big, they make operating fiddly bits difficult. Too small ones will cause numbness of your fingers after a short while.
Speedbar you can’t get to without using our hands. If you have one of these, get yourself a proper one.
Mobile phone. Take it with you, by all means, and have it somewhere you can reach it without getting off the harness. But: have it switched off to eliminate the temptation answering an incoming call during flight. No call is likely to be worth the trouble. In fact, you should switch the gizmo off as the first thing when you become your flight preparation. A distraction caused by an incoming call during your preflights can cost you your life.
Harness you have adjust after takeoff. In general, ANYTHING you have to adjust after takeoff. Also, if the harness has the habit of catching cables or lanyards of your instruments, camera etc on its buckles needs your urgent attention. I’m sure, you can add a few items to the list yourself. Do not underestimate these “trivial” details. They can become big issues in some situations and it is not worth the risk trying to cope with them. Get comfy – get safe!
For simplicity sake, the weight of the canopy has been omitted throughout the article.The load produced by the weight of the wing acts in a different way than the main (pilot induced) load and can cause changes in AoA. As the weight of the canopy represents only 5% of the weight of the whole system, these changes are negligible in the situations covered by this article. They will have to be taken in account if an extreme drag is applied (deploying reserve).
An interesting article has been published in the Cross Country magazine recently. It was dealing with problems of drag caused by PG pilot and his harness. This part caught the most attention and it is still being discussed in some forums at the Internet: drag at the pilot’s end is not necessarily a bad thing. It can actually cause an increase of airspeed! No, it wasn’t an April issue. Follow the logics behind it as presented: We all know, when you want to make a glider fly faster, you simply increase its negative pitch – point its nose down – and gravity will do the rest. So, if you increase drag at the pilot’s end, you effectively apply a torque to the system and it will rotate. The system will tilt forward until a new equilibrium between the pilot’s drag and his pendulum is reached. The pitch of the wing will become more negative and – BINGO. We’ll fly faster! Or, will we?
It is interesting how many principles from a fixed wing planes can’t be applied to an aircraft with a strong pendular stability such as a paraglider. To see why, we have to establish some less obvious (or less known) facts first: The first thing we have to realize, paraglider is not being loaded directly by the weight of the pilot. Our wing is being loaded by a force in the direction of the lines (direction best visible on the risers just above hang points). This force is a vector of pilot’s weight and his drag. It is always slanted forward against horizontal, as a result of the pilot’s drag.
Again, there were lengthy discussions on some forums, if the drag adds to the load or reduce it. To make it obvious, try to apply an extremely high drag – a large drogue chute, for instance. It is easy to imagine the pilot being suspended now between the chute and the wing, its weight divided between these two. A simple vector diagram confirms our suspicion: the force on the lines is ALWAYS lower than pilot’s weight.
Another fact, rather hard to absorb, is: the angle of attack (AoA) of a paraglider is given exclusively by the trim of the glider – by the length of the respective lines. It is vital to absorb this fact as it is the key for understanding to virtually anything in PG flight mechanics. Doesn’t matter if the PG is in a steady flight, being deployed or towed: the direction of the “lines” force relative to the canopy and thus AoA of the glider remains the same - As long as we don’t change the length of some of the lines (applying brakes or speed system), that is. The magnitude of the force may change, but not its direction relative to the canopy. Still, we have to understand, the ONLY factor determining the airspeed of a given wing, flying at a given AoA, is its load: the bigger load, (or, more accurately, the square root of load), the higher airspeed and vice versa. Now we are ready for the close: we add drag at the pilot’s end. The glider pitches forward. At the same time the glide path (L/D) becomes steeper. As result, AoA stays the same (we know it can’t change anyway). The added drag reduces the force on the lines thus the load of the wing. Now we have the same wing, flying at the same AoA, with a smaller load. The net result: it will be SLOWER. Period.
If you don’t wont to bother about all the stuff above, just follow my intuitive reaction on reading the “Drag Rocket” (as I call it) theory: “So, if hanging in a strong wind just above the launch, going nowhere, I should ask somebody: ‘please, pull me back a bit, I need to penetrate!’ And, I idiot, always ask people to push me forward…” By the way, pushing is not the best solution either. A forward force in the direction of glide path (at pilot’s level) also causes reduction of load and consequently reduction of airspeed – but the glider will be climbing in this case. If you ever tried, you know! A vector diagram would show you why. The right words in this situation are actually “Pull me down! (help me to load the glider more)".
The gist of this whole article: if you found somewhere a piece of advice suggesting to stand up in you harness (to increase drag) if you are in the danger of being blown back, think twice. It may work (to a degree) in some special cases while flying a very heavy glider, probably made from a wet wool. In that case the load caused by the weight of the canopy may become significant enough to cause a miniscule increase of speed.
We’ve established already that in the world of aviation we rarely get what we see. In an environment like this, it is no surprise, a number of myths or misconceptions appears and often holds for many years. Some of them are harmless other can cause serious problems or even accidents in some situations. We have to admit there is still a lot to be discovered in aeronautics and there are parts nobody fully understands yet. On the other hand: it would be foolish to believe the mechanics of flight has some exemptions from the general laws of physics. For this reason there is no such a thing as a “compression zone” on the top of a hill. By using this term we are contradicting a lifetime work of an 18th century physicist, Daniel Bernouli. He discovered the pressure exerted by fluid is in reverse proportion to its speed. A hill causes a virtual narrowing of the cross section available for airflow, forcing it to move faster. As a net result the pressure on the top of a hill is lower!
Very much the same mistake are making people, trying to explain Ground Effect as a result of “air compressing between wing and the ground”. The exact opposite applies! A venturi effect would actually cause the wing being “sucked” towards the ground – if it ever comes close enough. Ground effect is caused by blocking off wingtip vortexes.
“A less loaded paraglider will stall easier than a more loaded one…” A proper interpretation is needed here. Your glider will stall at the same position of brakes, regardless of its load. The truth of the initial statement will appear only if we apply it to a turbulent air. The less loaded wing will be slower in both, horizontal and vertical direction. Sudden changes in airflow will more easily change its angle of attack and stall will be more likely to occur.
“If we overload a wing, it will stall.” Not true. Stall is a result of an excessive angle of attack. In a paraglider the angle of attack is given by the trim and can be increased by pulling on brakes. Again, angle of attack will remain the same regardless of load. If we apply more load the sink rate will increase. But the forward speed will immediately increase by the same rate and angle of attack will remain the same. We can get some problems in extreme cases, where the overloading approaches the limits of structural integrity. Nothing changes on the above principle, but the changes in the shape of the wing (stretching of lines etc.) can change angle of attack.
“The stall speed (or any other speed) of this wing is xxx kph.” A meaningless number. This statement is valid only if a load is specified for that particular instance. Wing can stall at any speed – in dynamic situations even at very high speed – if the critical angle of attack is reached. It is true: within the weight range the differences in speed are rather insignificant. But we have to realize a load is not always only the static force exerted by the total weight.
“Weight shifting in the direction of turn will make turning more efficient.” This belief survived about 2 decades and only the birth of Acro Paragliding put some doubts on it. Acro pilots need to turn more efficiently and safely than CX pilots. They discovered soon, the accepted technique doesn’t work in all situations. If you look at the mechanics of it, you’ll easily understand why: In a turn, you want the outer wing to fly faster than the inner one. In order to make it fly faster, you need to put more load on it. Furthermore, you want to maintain the correct angle of attack. If you reduce the load at a given speed, angle of attack will get lower and the wing will eventually tuck. The inner wing, on the contrary, has to fly slower and you can guess: loading it more doesn’t exactly help the cause. We also want it to stall as late (at as low speed) as possible. A funny thing… the higher the loading, the higher the stall speed is. So, now: why, for god’s sake, should you transfer more weight to the inner wing? Possibly to bank the wing into the turn... Do you really think you can bank (to any significant degree) a wing with a strong pendular stability by weightshifting? If there is no any other force but gravity (straight flight), you will aways hang straigh down, wighshifting or not. Bank will come as result of the turn (certifugical force), it will not cause it.
Despite of the mechanics of it was clear to me from the day one, it took me almost 2 years to learn the new technique and find it perfectly natural. The reason it took so long: I believe we have some instincts inherited from riding a motorbike. Takes a while to get over it. At this stage I apply more weight in the direction of the turn only for a brief period needed to initiate the turn and associated bank. Why it is needed and why it works at all is a bit of a puzzle. I discussed this phenomenon with some highly involved people. Nobody was able to give me a full explanation. The whole thing seems to be several factors working together (or against each other). Changes in the shape of the wing seem to be one of them, but I wouldn’t try to elaborate on this problem myself. The final result depends on the proportion of each of the factors involved and it may not be the same with different wings and in different situations. Anyway – from the point of initiation of the turn I transfer my weight immediately to the outside wing while braking on the inside – and bingo: everything works exactly the way the theory says. A word of warning: Timing is an important part of the equosion and it may not work for you until you master it properly. However, when you once do it right, you'll recognize it right away. Once having it right you can get results you never thought possible before. Applied during a spiral you go down more than 20m/s during the second turn. In a wingover you’ll find yourself above the canopy before you know it. Do NOT use this technique for any kind of radical maneuvers unless under supervision of an instructor and in a safe environment (above water). For improving the efficiency of your “normal” turns however, it is perfectly safe. Tuck of the outside wing will become a history and negative spin will be harder to induce. Do not push it too far though and discuss the matter with your favourite instructor before trying at home.
“The number of collapses and their severity is directly proportional to the strength of thermals.” Not true. Wing has no idea how fast the vertical movements of the air are. It will fly exactly the same way in a parcel of air rising 20m/s or falling at the same rate. It does take notice of the speed of the changes. Acceleration will cause a change of its loading (“F=m * a” - where “F”[N] represents the load, “m”[kg] the mass of the aircraft and “a”[m/s^] acceleration). If the change of vertical speed is fast the loading will change dramatically. Just an example: if you enter a 10 m/s thermal within one second, the wing loading will DOUBLE during this period of time. Due to the pendulum effect the results in a paraglider are especially unpleasant. However, as soon as the wing adopts the new ground related vertical speed, its load and resulting airspeed (both vertical and horizontal) will become the same as in a still air. The problem is not in the absolute speed of the air movements. It is in the horizontal distribution of them and related speed of the changes applied to the glider. Especially if one part of your wing finds itself in an air moving vertically only a fraction of m/s faster than another, the change of angle of attack will cause a serious tuck or collapse. Flying in broken thermals of speed of 1m/s or so would become a frightening experience, while entering a 10m/s boomer can be a pure pleasure if the transition is slow. In the next issue we will have a closer look at the units and terms we are using to measure and calculate some of the aspects of our flying.
Most of our experience at perceiving the world around us comes from living as earthlings. So, we know that “down” is towards the earth, “up” is towards the sky “forwards” “backwards” and “sidewise” is always towards the horizon. As soon as we leave the earth surface and apply a bit of dynamics, all this can change dramatically and all our previous experience becomes a burden. If you keep relying on visual references like horizon or the ground in dynamic situations, you’ll come to grief sooner or later. It is hard to overcome our natural instincts and it may take a long time of conscious effort before pilot stops judging angle of attack (for instance) from the position of the wing to the horizon. Towing is the best example, how deceiving this reference can be.
Two interesting, and never-ending, threads popped up on the famous Xtreme Big Air discussion group. Both of them became so complicated, because some of the participants refused to accept the above. One Scottish gentleman has developed a completely new theory of a paragliding flight based on his observation that wing appears to fly in front of the pilot. As lines can transfer only “pull”, not a “push”, his conclusion was simple: Wing is producing a force (a component of lift) that pulls the pilot thru the air. He claimed, he’s discovered a 30 years old mistake in the theory of flight - causing a ferocious verbal battle between his followers and opponents. He fell in a simple optical illusion trap - using horizon for a reference. He watched the situation from the human perspective. Paraglider is different from a human - it can’t see. Our wing senses only two aspects of the surrounding world: the pull on the lines (it is NOT vertical) and the relative airflow (glide path) that is NOT horizontal. Any other concepts, like the horizon, are entirely foreign to it and wing behaves only in relation to the two references above.
So, if we look at our vector diagram from the perspective of the wing (using the glide path as a main reference), we see the PILOT is IN FRONT of the wing. A component of gravitation force applied to the pilot pulls the wing forward generating the required speed. For a better understanding see caption 1.
Effect of the weight of the wing and drag on the lines were omitted as negligible for our purpose. Pilot’s drag is responsible for the slight visible declination of the lines from the vertical. A reaction for this drag is the pendulum effect (not drawn) as the pilot is continuously trying to swing directly under the wing - so, he is being pulled by it after all! Well, in a sense, yes. Depends on the frame of reference we are using - either conclusion is correct. But the "prime mover" is always gravity.
Another mayhem on the forum was triggered by somebody’s query: “Can wing stall while shooting forward of the pilot?” A seemingly stupid question: We all know, wing will stall while well behind the pilot. Or does it? The first thing to take in account is, it is not always the movement of the wing that causes the apparent change of mutual position of the wing and pilot. It is more often the swinging motion of the pilot (the surrounding air has to be used as a reference to get the right picture) in relation to an almost steady wing that creates this impression. We are getting sucked into perceiving this as movements of the wing as we use the pilot’s position as a fixed observation point. The second aspect: go back to the beginning of this article and forget the horizon. And you have the answer. Yes, you can stall your wing while it is “shooting in front of you” if you apply enough brakes - exactly the same way as if the wing is above or behind you.
Capt. 2 Capt. 3
Look at caption 2. Everything fits in the picture, as you know it. Wing stalling behind the pilot – but only before you look at caption 3 and realize caption 2 is only an inverted crop from caption 3… The story of this picture (I talked to the pilot after taking it): This pilot decided to abort a tumble (felt like he didn’t have enough speed) and stalled the wing by applying brakes while the lines were approx. 45 dg up. But, there was plenty of speed after all and the wing-pilot system kept rotating another 45 dg, almost causing the pilot falling in the canopy. He missed it by inches… So, beware: In the air things are rarely exactly as you can see them!
We all like flying. Unfortunately, sometimes things do not go exactly as planed and we end up with a totally different activity: bush walking or swimming, for instance. Landing in the water, Needles to say, is a health hazard. But even such an innocent event like tripping on a beach landing and rolling in an ankle-deep puddle can be very painful - for your pocket. An average hang glider or paraglider pilot carries at least $1,000 worth of electronic equipment on him nowadays. These things do not need much salt to be rendered worthless; as little as a few drops of a sea water and that is it. I've seen enough of these. My swimming pool served as a regular first aid for canopies of those pilots who didn't quite make it on the east coast. Unfortunately, often by the time they arrive, it is far too late for their high tech gadgets. Knowing what to do after flooding your toys by that solution of sodium chloride can save you a fortune - but not always. The little factor called luck is always needed here as well. The actions described below are acts of desperation, but they are worthy of trying. Once the item has been in salt water, there is very little left for you to spoil...
The most important part just after the flooding is the speed by which you remove the batteries. Do not waste time by switching the gadget off. Not only it is useless (salt water is highly conductive and will bridge the contacts regardless), but you may even destroy the switch! And worse: if the instrument case is almost watertight and there is a couple of minutes delay, the electrolytic process will fill it with an explosive mixture of hydrogen and oxygen. Your action will produce the last important ingredient for every good blast: A spark.
The first objective is to REMOVE the batteries. In fact, you often have only a few seconds to perform this task and still have some chance of success. All the following effort will help only if you were fast enough on this primary task! The batteries safely out, take the unfortunate gadget and drop it unceremoniously in a bucket of fresh water. Leave it there for some 15 minutes, stirring occasionally. Even if it doesn't help, at least you'll attract a crowd of spectators and you can charge some moderate fee for the show. Then you can relax a bit. Drive to the nearest petrol station and buy a couple of litres of distilled water, by which you replace the existing brine. From now on the treatment will vary for each different kind of equipment. Devices with some mechanical and optical components (cameras) shall be left in the water, the container filled to the top, made airtight and delivered ASAP to a specialized service facility. Look for people specialized in drowned equipment - they advertise in SCUBA diving magazines. A regular service technician might send you, well, somewhere else. If the camera was a modern SLR (the past tense here is fully justified), don't bother. Give it to your 3-year-old. If you get a smile in return, smile too. You've made a bargain! With radio gear, varios and similar you have a good chance even without professional help. Leave the items the distilled water for about 2 hours and stir a few times. After that, put them briefly in methylated spirits, blow off with a low pressure compressed air and place them in an oven (not microwave!) heated to 50 dg C for about 4 hours. After cooling down, spray all switches, contacts, potentiometers and metal parts by a water displacing lubricating agent, like CRC2/26. Keep this stuff well away from RF parts (especially varicaps) pressure sensors and soft push buttons. It can cause some problems there.
Now you are ready for the moment of the truth. In most cases everything will work like a chime! Often only a speaker, with a paper diaphragm, suffers and has to be replaced. A very cheap experience indeed! If it doesn't work at all, see professionals.
The rechargeable sealed battery packs need special attention too. Take the word "sealed" with reservation. The casing will positively let the salt water in, SEALING it perfectly inside - hence the name. Such a pack will become a serious fire hazard and it will fail shortly, often with spectacular sound and light effects. To give you some idea what it can do, I can show you (for a small fee) one of my old radios. To eliminate this time-bomb factor, DISCHARGE THE PACK THOROUGHLY ASAP through an automotive globe or a similar load. Never shorten it! Until it is completely flat, wear glasses and gloves as it can explode at any moment. Then break it open, wash and dry thoroughly in similar fashion as described above and glue it back together. If you do not want to bother with the above, GET RID OF IT! Beware; none of the drowned items is as healthy as it looks now: DO NOT FULLY TRUST THEM AGAIN! The most effective, but highly unethical solution is to sell them quickly to an unsuspecting enthusiastic. If you want to keep them, replace all insulated wires inside (usually, there are not many of them) within about a month. The salt water seeped under the insulation and there is no way of getting it out. After powering the gadget again, it will start eating the core at a surprising speed. The terminals or soldered ends will usually fall off within a few weeks... After the wires exchange you can expect ALMOST the original reliability.
Finally, for god's sake, do not fall for some much faster and simpler treatments, unless you want to make sure nobody will be able to fix your gear ever again! One of the recipes circulating here is, to wash the items in VINEGAR, which NEUTRALIZES!!! the see water! Mere spraying them with some moisture-displacing agent is at least harmless, but equally useless. And the last advice: if you are being offered a second hand electronic device, look for the telltale greenish-blue deposits of copper chloride around the positive terminals. If these are present, politely decline the offer, even if it looks like a deal of the century!
Water and paragliders - DO NOT MIX. Sounds obvious. Nobody will put his $4,000+ toy in the drink by purpose. Just the associated health hazard should put you off well enough. But your glider can get wet by some different means as well. Rain for instance. Or, flying at the coast in close to 100% relative humidity and with a high lapse rate. After a descent from mere 100m of altitude, in the warmer air the moisture will condensate on the colder material rendering it DRIPPING wet. Salt water is the worst enemy - even when paragliders are made from materials resilient to the chemistry of seawater. Sharp salt crystals grinding the microscopic fibbers of the lines is the last thing you need. It will keep absorbing moisture as well. So, if it gets in the bay, SOAK the whole glider thoroughly in fresh water and let it dry SLOWLY. Are you out of the woods? Far from that. The fabric and the cores of the lines will cope well. The main problem is the protective shielding of your lines. Invariably, it will shrink - sometimes substantially so. As all the lines will shrink at the same rate, not a big issue - yet. It will show only after a few flights. The coating will need relatively small load to get back to normal. In the case of A and B lines this load will be probably reached after the first spiral or a tow. The rest will remain shortened. Result: a higher angle of attack with all the consequences. Treatment: stretch the rest of the lines by applying about a quarter of the breaking load to all lines, one by one. The result is not guarantied though. Check the length of each line against the manufacturer's specifications. If there are differences of more than few millimeters, changing of the whole set is the answer. My sympathy... not cheap, but better safe than sorry!
Generally known as “varios” these instruments went a long way during the last 15 or so years. From simple mechanical pressure gauges to the modern flight computers they became essential parts of the paragliding equipment. Varios use changes of air pressure with altitude to monitor height and the rate of lift or sink. This data is conveyed to the pilot via LCD or fed to a computer for further processing. Bear in mind, the air pressure changes quite dramatically with weather conditions and a frequent calibration is essential for accuracy. To get some idea: at sea level 1 Hp corresponds roughly 8 m of height. This ratio increases rapidly with altitude.
The heart of an electronic vario is a pressure sensor. It is usually a capacitor where the plates bend with air pressure, changing its capacity. This capacitor is a part of an oscillator where the changes of capacity control the output frequency – and that is what we measure. A sophisticated, usually software-driven circuitry process’ this signal and gives us the information usually in both digital and analog form, often accompanied by an acoustic signal as well. The peaks are stored in memory for a later basic flight evaluation. Most of the entry-level instruments now also include thermometer and watch/timer.
Used together with GPS (not connected to it) it tells to a typical recreational pilot just about all what he needs to know about his flight. The more sophisticated instruments are using the combined vario and GPS data for further processing. This enables us to get information like wind speed and direction, speed to fly, height over the next waypoint etc. While choosing a vario to suit our purposes we have to asses how effective this features are and how much we really need them. Remember: you have to pay for them. To start with: due to a low speed and efficiency of paragliders the value of some of the more sophisticated functions is rather questionable. Even with the most elaborated instruments the pilot has to apply a lot of skills to filter off “noise” from useful information. Some of the best pilots in the world are still flying with very basic equipment achieving excellent results. However, as the technology is improving and getting more accessible, flying by the seat of one’s pants is getting increasingly rare.
Another point to stress: the “medium range” of instruments has some limitations. For the advanced functions information about the horizontal movements of the air is needed. While there is no input from GPS (external or integrated) this information has to be entered by pilot before the flight. Any changes of these conditions render all the related calculations inaccurate at the best. Any expensive vario offering glide ratio based functions without GPS is a poor value for money.
To get a full use of a full-blown flight computer, another piece of hardware is needed: an Airspeed Sensor. Computer uses the airspeed data to determine the point of polar curve the wing is flying at any given moment. Needles to say, the correct polar curve has to be known to the computer as well. In a PG application the position of the sensor presents a huge problem. Taking in account the Venturi effect around pilot’s body and pendulum movements of the pilot, the ideal place would be somewhere in the lines near the wing. This brings out serious safety issues and I strongly advise against this solution. The whole problem is actually so complicated, only a few serious solutions exist. Forget completely the impellers hanging down. The data is of a poor quality and the whole thing is just a cumbersome nuisance. The C-Probe by Compass is as close to perfect as it gets - at a cost - of about $600 actually. The complexity of this instrument illustrates the extend of the problem it has to cope with. C-Probe consists of a Pitot Tube, gyro-stabilized compass, 2 accelerometers, thermometer and bluetooth device. While it works, you have to ask yourself a question: "Do I really need data this accurate?" Unless you are a very ambitious comp pilot flying a top comp wing, the answer is probably "no".
So, what an instrument like this can do for you? Besides of what virtually any other vario tells you (altitude, sink/lift, temperature etc.) flight computers have a lot of other bells and whistles. One of the most important features is a detailed 3D recording of your flight including vario data and airspeed. The tracklog is an excellent tool to analyze your flight and identify any mistakes – after the flight, that is. A special software can project your flight into 2 or 3D map and let you re-play it with an incredible reality. In flight the instrument gives you visual and acoustic information about the proximity and validation of waypoint (adjustable FAI cylinders). That’s just for a starter. The other functions include:
Auto Start recording – anybody who ever lost a comp because he forgot to switch recording on knows where the value of this feature is. Wind speed and direction – an invaluable information for safety and evaluating your chances to reach your goal.
This is further refined by the Speed To Fly function. A set of arrows advises you to fly either faster or slower for achieving the best ground-related glide ratio. To evaluate your chances of arriving at a preset height above the next waypoint the actual (custom averaged) gliding ratio is being constantly displayed, together with the gliding ratio needed for that task. It can be replaced by a display of the height you will arrive above the next waypoint if flying with the current gliding ratio. Extremely useful in long glides.
McCready Function should help with reaching the next waypoint at the shortest possible time. I found it virtually useless (for paragliders anyway) though, as it requires a lot of guesstimated input at each occasion. This function has more use for sailplanes or hanggliders.
The Total Energy Compensation function helps you to ignore false lift generated by washing off excessive speed. A bit of an overshot for a paraglider – but, yes – it works.
Netto Vario is an option for monitoring vertical movements of the air instead of movements of the glider. Some pilots find it more useful than normal vario. Again, it needs the correct polar curve for the machine you are flying.
Stall point warning – no of much use in the PG application. The best you can do with it is to switch it off to prevent driving you mad due to false low airspeed reading during swings back.
Air speed display – flying a paraglider you know your speed from the position of the brakes anyway. This function has its use only while checking if your wing characteristic hasn’t changed after taking it for a swim or a tree landing. The list can go on – if you are a serious XC or comp pilot, it may be worth considering an instrument like this. Very little left for imagination. A scary stuff… Only autopilot can beat this. I wouldn’t be surprised if somebody is working on it already!
I followed with interest the discussions concerning UHF 2 way radios on Topica. As there are lots of myths surrounding these gadgets, I decided to shed some light on the subject. UHF CB stands for Ultra High Frequency Citizen Band radio. This band (around 470 MHz) is assigned by the Department of Transport and Communication to non-licensed radio operators and can be used by anybody who can put his hands on an appropriate transceiver. There are simple rules to follow, which, however, are hard to impose. One of them is 90% of the transmitting has to be a human voice. It is also prohibited to re-transmit any broadcast or recording except by approved repeaters on duplex (more below). The ban of foul language and swearing has been lifted a few years ago - so, help yourself. A plain courtesy dictates not to block channels deliberately and allow other users to communicate. After all, there are 80 channels in that band. The only ones subject to some restrictions are Ch. 5 and 35, reserved for emergencies only. Ch 22 and 23 are reserved for telemetric data transfer. Channel 40 is being dominated (but not licensed to) by truckies. Do not let your children listen to this one.
Skyhigh club is using Ch. 16 coded by 97.4 Hz squelch tone (CCTSS) but be aware: This channel is as public as any other in the CB system. The squelch tone frequency of 97.4 Hz can be listed under different subchannel numbers depending on the manufacturer. The most used: Icom and Motorola - subchannel 11. The easist way to hook on it is to have PGHQ radio, where you simply select "Skyhigh" on the alphanumeric display.
The maximum transmitting power is restricted by law to 5 W. A serious power in fact, as it allows reaching distances of some 200 km in ideal conditions - or even more using special antennas. The range is a tricky subject, as UHF signal is in the habit of traveling in a straight line, bending only slightly by the earth magnetic field. The result is, two radios, held at the head level can communicate even in a perfectly flat terrain, only over some 10 km. Then the signal gets blocked by the earth's curvature. This problem can be, off course, fixed by gaining elevation over the terrain. Even a small elevation can increase the distance dramatically. Conversely, it gets worse with any solid obstacles in the way - hills, buildings or vegetation. These block the signal very effectively and any conceivable increase in transmitting power is futile.
Special cases are conductive objects of 1/4 wavelength long. These act as simple quarter wave antennas, absorbing and weakening the signal even if they are not directly in its path. Gum leaves fit the bill almost perfectly.
Knowing the above is a part of the answer on the "Should I have 300mW or the full 5W radio?" $5,000,0000 question. True, in ideal conditions - at the distances we normally communicate - there is no difference worth to mention and the smallest hill will block 5W as reliably as 300mW. However, if the extra power shouldn't cost you much, go for it. The more power, the better - no doubts.
Note: only radios approved by ACMA and carrying the "tick" sticker are legal to use in Australia. If you are using a non-compliat device, you are risking severe penalties and confiscation of your radio.
Antennas are another story. Do not try to improve you signal by simply lengthening the antenna. You'll be tampering with a finely tuned device, making things only worse. The simplest antenna is a piece of straight wire exactly 1/4 of wavelength long. It transmits - or receives - signals from all directions except of sharp-angle cones in the directions of the tip and the base of the antenna. For our purposes it works fine. The performance can be improved by an antenna with a gain. There is, in fact, no gain whatsoever. These antennas only direct signal in certain directions, reducing emission in the others. Typically, they widen the angle of the above-mentioned "Cones of Silence", strengthening the signal around the rod. This is making the antenna more sensitive to its position as well. With any rod-type antenna the area in the direction of the antenna tip or base has virtually no coverage. The worst result is achieved by pointing the tip or the base of the antenna to the other station. The position of antenna is important for other reason as well. Our radio signal is polarized. It means two communicating antennas work the best if they are parallel. Any deviation of this positioning will significantly reduce their effectiveness. The worst results (theoretically 100% loss) will be achieved if the communicating antennas will be poised 90 dg one to another. As the UHF CB signal is, by agreement, vertically polarized, try to keep your antenna as close to the vertical position as possible.
Earlier on, I mentioned repeaters. We seem to stubbornly ignore these devices, despite of their ability to let us talk over the hills. Repeaters on CB system are privately owned, but a part of the license agreement is, they have to be available for a public use. They can be found on channels 1-8 and work this way: If you switch you radio on "duplex" and use, let say, Ch. 4, your radio will transmit on Ch. 4 + 30, i.e. 34. The repeater will receive it and re-transmit it on Ch. 4. Another transceiver switched on either "duplex" or "simplex" Ch. 4 can receive that signal. If the repeater is on a top of a hill - and that is where they mostly are - the coverage can be enormous. To find out if a particular area is covered by a repeater is simple. Switch you radio on "duplex". Select channel 1 and press the PTT button momentarily. If you, immediately afterwards, receive a burst of static-like noise, it is the repeater. If not, try the next channels up to 8. Beware: the louder the response is, the weaker is the repeater signal. A good, strong signal induces a barely audible response! Repeaters also introduce themselves in certain intervals by Morse-coded signals, for instance "M 3" means Melbourne, Ch. 3. By the way: this particular one situated somewhere near the Police Academy is virtually useless as it is being continually misused by all kind of lunatics. But the ones in country areas - where we need them the most - do not suffer from this problem that often.
A word about courtesy. In situations where our channel 16 is busy - like the club's fly-ins, use this channel only for information of either of general interest or short messages to a particular person. If the conversation is likely to be more than a few sentences long, it should look like this: "A to B, A to B. Go to Channel 12 (or whichever), confirm." After receiving the confirmation go on that channel and discuss your dinner arrangement for as long as you wish. Needles to say, your channel selector has to be accessible while in flight. This feature prevents you disturbing other users and also stops you from transmittig message that may not be received.
While using CTCSS it is a good idea to check if the channel is not busy by pressing the "monitor" button before transmitting. Some radios can be programmed to block transmitting if the channel is not free.
Another spot of annoyance are handheld radios without a proper headset or a wrongly positioned microphone. Nothing can beat VOX (voice activated microphone) on the scale of annoyance. Never use it! If you do, do not be surprised, when you get told off. Rig your radio properly and TEST IT before using it at a flying site. A proper headset with a finger-mounted PTT is the way to go. The best radio if not properly installed and fitted with the above is virtually useless to us. Do not fall for a supplier who do not provide the headset and PTT as standard. You may find either impossible or terribly expensive to get it later on. Hand-held speakerphone is a half-baked solution and it not only compromises safety but they also produces a lot of wind noise.
A blocked PTT button can spoil a whole day to a whole bunch of pilots. It can happen to anybody, any time. But the problem shouldn't last long. If you can't hear anything for 5 minutes or so, it is time to check your "Transmit" LED. If it is on, switch the radio off immediately and leave it that way until you fix the problem. It is actually illegal to use radios without TOT feature. These will stop transmitting after a preset short period of time. The most educating example of the consequences of ignoring this advice would that tandem pilot in Bright a few years ago. He accidentally transmitted his one hour presentation intended for the ears of his female passenger only. The whole flying fraternity was glued to Ch. 22! Note: ACMA approved radios will automatically cut of after max. of 3 minutes transmitting.
Also, while in the air and communicating only over a few kilometers distance, switch your radio on "Low Power". Note, this will affect only your transmitting range. Reception will not be affected. This will make you less obnoxious to not participating distant stations but also SUBSTANTIALLY save your batteries. You are also less likely to attract attention of some imbecile who is taking pleasure in blocking other people's communication. The world is full of these.
Orthodox radio geeks are using their own language. We are not obliged to follow but it comes handy to know at least the basic:
Affirmative - Yes
Negative - No
Roger - Received, understand
Say again - Repeat
A copy B, A copy B - A, please, answer B
Go ahead, B - Answer to the above
Radio check - Is my radio working?
You are working - answer to the above
Breaker - Sorry to interrupt you conversation, I have something important to say
Go ahead, breaker - answer to the above (more common is "Get f%&cked", but one can always try)
Over - end of my transmitting, but I'm still listening
Over and Out - end of my transmitting, switching off.
And the most important ones - NEVER use these without a sufficient reason and NEVER interrupt these transmittings:
Mayday Mayday Mayday - My life is in danger. Details will follow.
SOS - obsolete and rarely used nowadays is the equivivalent of the above. Used in the past for its easy to remeber Morse Code shape.
Pan Pan Pan - Somebody's life is in danger. Details will follow.
Securite Securite Securite - Important message concerning safety in general will follow.
I hope you found this article useful and we'll see some improvement in our radio communication. We need it.
We'll be talking about flying, so the answer won't be as clear as you might expect, girls. Take all the following with a grain of salt as in this field very few things are as black & white as they might appear in other areas. Also, please, fill in the usual "(she)"; after every "he" for yourself as I'm tired of it. Why aren't all languages as accurate as Czech?
One of the crucial questions while buying a new wing is: "What size?" Pilot often finds himself in a situation, when he has to choose between being either on the top or at the bottom of the weight range. NOW WHAT!? There are a few aspects we have to consider. Stability: The more loaded wing will collapse less easily - on the other hand - when it does, things will be happening more quickly and the height loss will be more substantial. Pretty well balanced situation - toss a coin and then adjust your flying to the situation :-).
Gliding Ratio (efficiency): In the general mechanics of flight the answer is clear. It will stay the same. But paraglider, the nightmare of every aeronautic engineer, has its own peculiarity; While the drag and lift of the wing itself will change at the same rate with the size of it, we have to consider the drag of the pilot as well. As it stays the same, the total drag of a larger wing will be relatively smaller then the one of the smaller wing. Net result: A large wing will have a better glide than its smaller counterpart! That is, if we ignore Reynold's Numbers and aero-elasticity. Effects of these two are largely unpredictable. A tough decision.
Speed: Again, in the general mechanics of flight, the smaller wing will be faster. But the two factors mentioned above (especially significant in paragliders) can play strange games with us. If speed is your objective, the smaller one should be the right pick. Still, don't worry too much: The difference will be somewhere between 1-2 k/h.
Sink rate: Very much as the above, just the other way round. The outcome is even more predictable than it is with speed: Virtually always the lower wing loading will result in a better sink rate - just a tad, but as we'll see later, it can show in some situations.
Agility: The more loaded wing will, invariably, be more agile. If you want to do large wingovers, SATs, loops - your aim should be ABOVE the recommended weight range. Conclusion: The choice of size is largely a personal matter and it depends on what you want to use that thing (paraglider, we are talking about) for. For a recreational pilot flying often on the coast and not too concerned about speed, a better sink rate can bring almost unfair advantage during ridge soaring. Due to the character of a ridge lift, you will be on the top of the stack all the time, regardless how good or bad pilot you are. It can also make the fundamental difference between bombing out or not in light conditions. In strong winds - if the small variation of speed should make the difference between you penetrating or not - you should not be flying in that conditions anyway.
Competition pilots, almost always, go for a high wing loading. In thermal conditions the marginal advantage of a better sink rate can be wiped out by one tuck or a single wrong turn. You are either able to core that thermal, or you are not. Again, in light conditions the better sink rate does can show. Now; assuming two pilots flying differently loaded wings reached the top of the thermal at the same time and set on a glide: The more loaded wing will be faster. Furthermore, in a headwind, that wing will have a better ground-related gliding ratio - and in a comp - you can't beat that. Play a bit with the polar curve, shifting it back and forth along the best glide line to see what I mean.
Sumarizing: Unless your have special reasons for some extremes in either direction, the choice should be somewhere in the middle. If this choice is not available - I, personally, go for the higher loading. I like the dynamics. But, that's me. Your needs might be different. It is important to realize; you fly in different conditions and a variety of tasks. Whatever you choose, you sometimes will get in a situation when you regret you don't have the other size. So, don't get too stressed about the choice. If really desperate, toss a coin!
I'm aware, anything I say can be used against me, but I'll try to be as objective as possible. By all means, all the following is only my opinion. It might be worth considering: I've been flying paragliders for more than 20 years, purchasing (for myself) in total fifteen of these contraptions on the way. I also used to sell them (and now do it again - some people never learn) so I know well the dilemmas pilots are facing.
Size: I wrote quite an exhaustive chapter about it above.
Manufacturer: If anything was this easy. Buy GRADIENT! Just joking... The reasons why I'm buying ( selling and flying as well) this brand, are very much in line with the philosophy and principles you can apply on a lot of other brands too. There are dozens of manufactures around the world. In Australia we live under the impression there are about five. The chosen few found by some means their way to the local market. Their popularity here doesn't always reflect the same in Europe or other countries. By all means all the locally established brands are at least good enough to deserve their share of our market and any of them is worth considering when you have to make that hole in your budget. If you live in Australia buying a glider which is being marketed in here is a wise idea. Buying anything else can cause enormous problems if anything goes wrong. Even if it doesn't, the re-sale value of that glider will be close to zero (do not have any illusions about the re-sale of ANY paraglider anyway), but in this case you will probably have to pay somebody to dispose it off. My personal policy is to fly paragliders to destruction. No headaches with reselling. If you renew them as fast as I do, at the end of their useful life good canopies will be still fairly competitive to the latest models.
Buying an unknown brand has also a distinct physical danger. We are putting our lives in the hands of the manufacturer here. Do not have any illusions. Some of them consists of converted tent makers who know close to nothing about flying. They are only copying the products of the "real" people. Some of them do it well and can be very competitive price-wise. The design and certification factor in the price of a paraglider is significant. Things do can get dangerous when these people start mucking around with the design or materials. As you never know - keep your hands off! Note: This advice is for an average pilot. There are some people around with enough knowledge, information and connections who can go against this advice, saving some money and still be safe. Do not try at home if you are not one of them. Summarized: You are looking for a manufacturer represented in Australia, with a good reputation overseas who's gliders show some success in international comps (adds the credibility and also it's the image-building factor behind your re-sale value) and whose products are reasonably priced. The presentation and service (cost of repairs, namely the cost of a set of lines, is worth investigating before you buy) is an important aspect as well.
Warranty can be quite tricky. Product without warranty should be dismissed right away. One year or three years (the two most common terms today) obviously can make a difference. How big, depends on the conditions applied to the multi-years warranty. In some cases you realize that to get something out from those extra years you shouldn't fly your machine at all. Most paragliders today are made from the same materials and using similar production technologies. Why one should be expected to last 3 times longer then another? The "Accidental Damage" warranty offered by Gradient is a great bonus, especially when most of the repairs (subject to some conditions) can be performed in Australia.
Avoid miracles. An enormous amount of "bull" is oozing from some of those glossy pamphlets. Just about every manufacturer is the best in the world and has just released the latest model speed (the most popular area) of which is about 10k/h higher then anybody else's. A flight with a Speed Sensor can become a real eyes-opener. Also the glide at the max speed can be something of a surprise as the general policy is not to publish polar curves. A very touchy subject... At the current state of information technology and competition the field is almost even. If somebody finds a way to improve the existing design just a tad, others copy by the speed of a lightning before the novelty even hits the market. Some of the "revolutionary design miracles" are products of wishful thinking not based on any science known to mankind. Note that the basic shape, layout and structure of a paraglider didn't change significantly in the last ten years. All those batons, inflatable spars, aerodynamic lines, deviations from the elliptical ground plan etc. mostly disappeared as quickly as they popped up. If you find a miracle, WAIT AND SEE. The real ones are not frequent.
The design features giving some manufactures that little edge you are looking for are rarely visible by a naked eye. A skilful application of existing principles and meticulous attention to details is what makes the difference between the winners and losers today. Steer away from gliders displaying some highly conspicuous design features. If they work so well, why nobody else copies them? These are mostly marketing tools and you pay for the privilege of being sucked in.
Certification and stability: The stability of your would-be glider is important. Unfortunately, it doesn't stand alone, and you have to balance it with performance. This can lead to some nail-biting situations because both of these aspects have large grey areas. There are some reasonably exact ways how to asses the performance of a glider. But stability is an untidy mess of various standards, opinions, numbers, with pure random occurrences topping the list. There is not an Australian benchmark for paragliders. We merely accept the opinion of testing authorities of other countries - and we even do not insist on these. But, if you do not have rocks in your head, look for a glider, which has been tested by some organization with a good international reputation (ACPUL SHV DHV...).
The most recognized today are the EN testing standards. Unfortunately, what you are getting is called in statistics "an accurate product of inaccurate data". If you are going to fly in a glasshouse, sit stiffly in your - EN certified - harness then you will get what they did. In a real world a EN B glider can send you plummeting from the sky in a series of cascade collapses which any pilot of a hot twitchy comp bastard never even dreamt of (been there, seen that). You were supposed to sit still and avoid any turbulence while falling you dummy!
I'm not trying to discount the EN (or any other tests). Just trying to show these numbers are not a bible. They are only an indication what you can reasonably expect from the glider if something goes wrong. Furthermore, they will not tell you at all HOW EASILY things can go wrong.
It has almost become a rule lately: "I'm an intermediate pilot now, I want a EN C glider." It looks like we automatically associate safety rating with performance. This is true only within certain limits and EN C rated glider doesn't necessarily have to a better performer then EN B by another manufacturer or of a younger generation - although it's reasonable to assume so. Our simplified approach can often lead to purchase of a glider only because it has a WORSE safety rating. Some amazing performers are in the EN B class now and if you are really safety conscious recreational pilot, you may never find the need for anything higher. There are pilots consistently winning major comps with EN B rated gliders. Often the extra stability in rough air can overweight the slight performance disadvantage.
Test flights: I have some amazing stories about these. I might cause a serious stir of the hornet nest but my sincere advice is: "unless you are a very experienced pilot, do not use a test-flight as a major decision point." If you base you decision mainly on test flights, you are likely to end up with a dog of a glider which you happened to test-fly in a perfect condition. You can also as easily miss out on real gem just because you didn't set that chest strap right. The worst scenario is, if you manage to crash the demo. Even assuming you walk away from the crash, it would be my educated guess your quotient of desire to buy the machine might have been severely depleted. If there is any damage to it (imaginary or real), the dealer will try to "persuade" you to buy the wreckage. The legal side of that practice is worth investigating, but more often or not - you'll become a happy owner. In my long experience it works like this: the typical "testpilot" takes of and indeed, the glider flies that's about all what he can establish with certainty. From that point all depends on the conditions. If hey are perfect, he makes some distance and lands safely. Then all I have to ask is, what color he wants...
Unfortunately, the weather doesn't always cooperate and the pilots ends up with a sledie. No even point asking any question. This testpilot will be looking for another glider and it may take a while before he manages to find the right one. I would have to search my memory hard to find an exemption from the rule :-).
As for myself - I bought all of my 15 gliders without testing them. I just didn't feel qualified enough to be able to find something about the glider what some of the best designers in the world didn't. I surely never regretted buying any of them. Do not have me wrong, I did my homework at each of the cases VERY thoroughly. I got all the references I possibly could, talked to the manufacturer, looked at their reputation and checked the official test results, Then I bought that thing - and took my time learning how to fly it. It took me some time to squeeze the best (if I ever got that far) out of each of my new toy. If there was anything I had a problem with it always was me using an inappropriate technique for the particular model and a simple change of my approach have solved it all. These are things you can never clear up during one or two testflights and any hopes to get some meaningful results are futile.
I have a deep admiration for anybody, who tells me everything (or anything at all) about a new glider after a 5 minutes sleddy. I can't do it. Do your homework, have your test flight if you like - every hour under somebody else's canopy is good for your back pocket - but put most of the weight on reliable, professional, and independent references. I know cases where even the most experienced competition pilots, like Craig Collings or Ron McKenzie bought their gliders without test-flying them. They just followed the simple recipe above. How do I know? They bought them from me. If I can judge from the results they both achieved in the comps, they have to be quite happy with them!
Let's close this chapter with one of the many test flight stories... Some years back a friend of mine was trying to sell his almost new DHV 1 glider by a reputable manufacturer to a new pilot. The asking price was ridiculous but the customer wanted a TEST FLIGHT. Well, we made a trip to 3 Sisters and set everything up. I took off first - and immediately wished I wouldn't have. I wanted to go home. The inside of a cloth dryer seemed to be a serene paradise in comparison with the air I was flying in. Having no radio, I couldn't warn my friends and they didn't get the message from the way I flew either - they thought I was enjoying myself! I managed to land somehow, scared of my wits and not having anything to say as where or when I actually wanted to meet the ground. The new pilot launched in the meantime. I was getting airsick only from watching him and I used all the prayers I knew from my early childhood. The guy landed in about 15 minutes, fresh as a daisy, about 20 meters away from me. "No, I do not want it. I almost missed the paddock with this one. The one I flew at school had much better handling!"
Many happy test flights!
Every pilot should regard a 2 way radio as an essential part of his equipment nowadays. The question is not if you should have a radio – the question is “Which one?” As for the frequency band, it is simple – at least as long as you are going to use it only in Australia. The UHF band has been adopted here as the first option and you can’t go wrong. As for features and brands – a different story. Only some 3 years ago there wasn't much of a choice either. Icom or Uniden – had to be 5 watts if you wanted some decent quality. Anything else was just a toy and better to avoid.
Lately – it seems like every man and his dog in China is making of a very acceptable quality packed with features – for about 2 bowls of rice a piece. If you are willing to spend around $100, you can expect a very good product already. The problem is, not everything you buy will suit our purposes. We are a fussy bunch of customers with specific needs. If the product doesn’t do exactly what we need, all kind of dramas will follow.
Catch No.1: the radio has to approved for for use in Australia by ACMA - otherwise it is illegal and you may face $multi-thousand penalties not just for using, but only for being in possession of one!
Let’s have a look at all the features one by one to make sure your next radio is the right one and the first step is checking, for the ACMA "tick sticker". If it absent, don't bother with the rest. This unit is illegal.
Power – this part reflects the most in the price of the unit. The highest power by law is 5W for a CB UHF. As the range is a logarithmic function of power, with 5W you will get only about 30% percent longer range than from the 1W, often much cheaper unit. Do not get put off by the numbers in the user manual, where the range is often in the region of 3 or 5 kilometers. These figures are pure guesstimate based on an average use on the ground. The 5W units actually do not fare much better in the same condition. We have the advantage of a clear line of sight while flying and your little 1W baby can cover 50km easily. But still, the more power the better and I’d suggest not to buy anything under 1 Watt.
Low Power Switch – very useful. Low Power usually means 1W. That means 1/5 of battery drain while transmitting on the 5W radio. A substantial saving indeed. You will be surprised how rarely you will need to switch back on high power. Bear in mind, this setting doesn’t affect the receiving ability of the radio.
Size - Smaller is not always better. Keep in mind you will have to operate your radio often while wearing gloves. Leave those miniature beauties for your kids.
Channels available – very important. The cheap, dedicated CB radios, have installed only the public, CB channels. The UHF CB band is, due to a general availability and lack of regulation grossly overloaded. For that reason HGFA is using a dedicated licensed channels outside the CB range. If the HFA channels are absent, you will have a limited use of your radio and encounter serious problems on flying sites. Check with your supplier how much he charges for programming of the extra channels, or, more to the point; if they can do it at all - legally.
Scan – not often used in our application as we usually know who is at what channel. Dual channel watch is more useful, go for it if you find it.
Automatic squelch – avoid if you can. It is better if you have control over the minimum strength of the received signal.
Duplex – allows you access to repeaters. It would be very useful - if we use it. As we don’t (I don’t know why), this feature is not really critical – but most units have it anyway.
Interference Eliminator Code (CTCSS) - essential, as all CB channels used by clubs and also HGFA channels are CTCSS coded. People using non-coded radios can hear all the subchannels, but can't interfere with them. An easy way how to block all the turkeys if you operate on CB. As this feature is becoming a major hit, I'd suggest to buy only radios with Interference Eliminator Code (CTCSS). All radios without it are virtually useless for us.
Pushbuttons Lock – an absolutely vital feature. Your radio is subject to all kind of abuse during launch and in flight as well. It is easy to switch accidentally to another channel or change other settings – unless you have the buttons locked.
VOX (voice activated transmitting) – most radios have it now. Make sure, it can be switched off. This feature proved to be a major source of nuisance and its use should be avoided like a plague. It may come handy for towing – as long as you don’t forget to deactivate it after you pin off.
Socket for headset and remote PTT – don’t even think about buying radio without it. Using radio without headset and remote PTT button is highly impractical and dangerous. Unfortunately, most original brand headsets do not suit our purposes and have to be modified. Often you have to go a custom made one – which can cost almost as much as the whole radio. Investigate if there is a SUITABLE headset available for the radio you intend to buy - otherwise, DON'T buy it. You may end up with an expensive gizmo absolutely unsuitable for our application no matter how sophisticated the unit may look like.
General setup – The simpler, the better. In the air you don't want to play with complicated functions and menus. You practically want only to select channel and then transmit and receive. Anything more is a nuisance. If you take this aboard, you can't go pass by my PGHQ unit. It took me a long time to develop it and from a business point of view it was completely cowboyish to have made something special for the small Australian market. Fortunately, it worked well and I am receiving an excellent feedback.
It is important you have all basic functions at your fingertips and have the display in a plain view. As the antenna has to be positioned vertically for best efficiency, make sure, the display will be visible to you while the radio is positioned this way - depends where you put it. The same applies to the channel selector, volume and squelch control. If there are any pushbuttons that can’t be locked (especially the power button) protruding from the case, grind them down mercilessly. Sooner or later they will cause problems either in flight or during transport.
If there is a detachable battery unit, make sure it has a safe lock – if not, secure it by an insulation tape against sliding off. If you can’t guess why, don’t bother. You will find out one day.
A word about programmable channels and dual bands: Both of these features can be handy when you travel overseas, but such a unit will be DEFINITELY illegal in Australia. Also, the bands and channels can be completely different in other countries. But before you spend megabucks on a radio with these features, I want you to know: The licensing conditions may be different as well. Much stricter in most countries, in fact. Don’t be surprised when a customs officer at the border produces a cordless drill and makes a neat hole or two in your precious toy. Nothing personal - just to make sure you won’t violate the communication laws in that country (been there, seen that, cost me enough…).
Your head – or what is inside it – is a precious asset. One would say protecting it should be one of the first priorities. Surprisingly enough, HGFA doesn’t see it that way and helmet is NOT compulsory for a paraglider pilot. I have to give a huge credit to the members of our community for using their common sense and wearing helmets almost religiously. Still, sometimes I have a sneaking suspicion, certain pilots do it for the wrong reason: some helmets look really COOL! As it happens, under the right circumstances, some of the cool looks can cost you your neck – literally. A proper helmet is often a product of years of research, experiments and design work. Some attributes are in a direct conflict: protection/field of vision, weight/overall strength etc.
The problem is compounded by the fact every application has different requirements. The best helmet for a motorbike rider can be entirely unsuitable for a paraglider pilot and vice versa. Still, all helmets have one thing in common: they should protect the wearer against a head injury while not likely to cause other serious bodily harm. Simple? Well, not quite. There is number of ways our head brain or neck can be injured – and a wrong helmet can contribute to the damage. Our brain is very well protected. That important chunk of grey matter is floating in a liquid filled cranial cavity. It is capable of withstanding deceleration of a few hundred Gs before suffering a serious damage. Unfortunately, when one’s hard skull hits a hard object those Gs can be achieved at surprisingly low speeds. A short stopping distance is to blame. It is the stopping distance a good helmet has to increase. Even the hardest helmet will not achieve this without a bulky and tough special lining. The other soft layer inside it doesn’t provide any significant protection and it is there for comfort only. The outer hard shell protects our head – and the lining – against penetrating objects.
Most helmets now go a bit further beyond protecting the brain, providing a facial protection as well. Not so important as the primary function, but especially in minor accidents a full-face helmet can make the difference between a bloody mess and no injury at all. So, how a good helmet for paragliding should look like? Probably the first thing to look for is some kind of certification. There are no Australian standards for paragliding helmets, but any certification by an authority from some civilized country is an indication you can be on the right track. The certification alone may not be enough. The criteria for issuing these are frequently quite ridiculous and often cover only the Gs protection factor. There are many other aspects to consider.
Paragliding helmet should be light – but not for the reason you may think. A motorbike helmet, for instance, is designed for a head-first impact. Weight in this case is an important commodity, reducing the deceleration and thus the damage caused to the brain. In paragliding this scenario is unlikely. We are dealing mostly with a feet-first impact and helmet serves as a protection against a secondary collision(s) with a solid object. Our helmet, ideally, should weight nothing as any mass added to the head increases the chances of a neck injury during the primary impact.
Bicycle helmet without the hard outer shell is not too good for us either. True: the expanded polystyrene that is made from is generally accepted as the best shock absorbing material for helmets. But, it is fragile: in paragliding we often get in a situation, where our head hits something more than once. When you roll down the hill, this helmet will deal well with the first rock, disintegrating in the process. The second rock you meet on the way down will crack your unprotected skull.
The “aerodynamic” shape, no matter how much it makes you look like a storm trooper, is not too good for us either. The aerodynamic gain is close to zero. This shape originates in bike riding and hanggliding, where it (due to higher speeds and the position of the head) brings some tangible advantage. PG pilots adopted this shape (It looks so sexy!) without realizing the danger it posses to them. If pilot rolls backwards over his head (quite a common occurrence), this helmet is capable of breaking his neck either forwards or sidewise by the twisting action. This danger is not fictional; quite a few cases of this type of injuries have been recorded. I was fortunate enough myself, to suffer only a fractured vertebra without the crippling consequences ten years ago. That adored spike in the back of a helmet can also serve to rotate your head really fast on certain type of impact, causing the rotation type of brain injury. The far protruding chin protector in full-face helmets can cause the same trauma – but at least this part has another useful purpose. In a well-designed helmet the chin protector is supposed to break off when the force of impact exceeds certain limit.
The helmet on the left cracked after pilot fell flat on his back (stall). It has done its job - the pilot suffered only a minor concussion. Can you guess what the monstrosity on the right would have done to his neck? Yuck! One of the important factors for any aviation helmet is, what parts of your field of vision gets obscured. There are surprising differences between brands and it is something to consider while making your choice. In full-face helmets some restriction of vision is inevitable. It has been generally accepted the advantages of a full-face helmet greatly overweight this minor shortcoming. Another advantage of a full-face helmet is the ease of installing a radio headset – do not forget this one. Adequate ventilation is also important and comes in play especially during long waiting on launch in the summer.
Color of the helmet can also make a noticeable difference in the temperature inside. There is nothing better if you want to suffer a decent heat stroke than the fashionable matt-black finish. Light colors not only reduce heat absorption, but also increase your visibility in the air. Another aspects to consider is the general comfort the helmet provides, how much it blocks your hearing and how secure the chinstrap is.
Do not leave anything to chance. Helmet is an important piece of your equipment and should stay with you for about 5 years – that is when you should consider replacing it, as the protective lining is loosing its shock-absorbing properties. Replacing only the insert could be the way to go – but surprise, surprise! The inner lining is about as expensive as the outer shell. It is not the cost of the material – that is almost nothing – but the cost of the mould goes into tens of thousands of dollars. That explains why you can get a decent helmet only from the large manufacturers. Also avoid any protrusions on the helmet (again, including the sexy spike at the back) – they can catch lines in situations when you need it the least. Visor or its hinges fall in this category too. I was experimenting with a visor for a while just to find the cons overweighing the pros and taking that thing off in the end. One of the biggest problems: the visor needs more care than you can possibly give to it during a normal use.
Paragliding harnesses made a log way from the pieces of webbing and (sometimes) a plywood plate they were in the dark ages of our sport. Contemporary harness is a sophisticated marvel of technology, sometimes almost as expensive as the wing. It is important to know what you can get for your money before you spend it. There is no such a thing as a “perfect” harness. The choice of this piece of equipment is subject to not only many personal preferences, but also to the purpose we are going to use it for – comps, general recreational flying or acro. I will concentrate at the largest, recreational cross-country sector of the market. Obviously, your harness has to be of the right color and look trendy. But we will leave this aspect to the very end, just after the overall comfort.
Don’t have me wrong. Comfort is extremely important. If you once get an uncomfortable harness, it can spoil years of your flying. But testing of this aspect should come only after you examine all the other features and you are happy with them. Then you will most likely find out, the desired comfort can be achieved by a proper combination of the adjustment available. Hang that thing somewhere, sit in it, try to get in and out a few times – get the feel of it and try to pull at all the webbing you can find. And make sure, you really find them all. Some adjustments can be well hidden. Most of the “other aspects” may not look important, because they involve parts you don’t use too often – such as the reserve extractor. But it is easy to imagine situation when a bad design of it can spoil your whole day. So, let’s start with this one.
Virtually all new harnesses have the reserve bridles integrated. They run from the shoulder straps to the reserve container, usually integrated into the harness as well. The reserve container can be found at different locations and it is important to know the advantages and disadvantages of each design. Experience collected during many incidents involving rescue parachutes indicates, the reserve has to be not only easy to reach, but the whole setup should be in a plain view during launch and in flight as well. Especially the pin(s) status has to be visible at a glance. This is rather hard to achieve with the back mounted containers. The disadvantage of these also includes the choice between having the handle at a hard to reach position or having it connected to the inner bag by a long webbing – less control, chance of entanglement. In the high mounted reserves the extractor at the shoulder may be hard to reach up during high Gs. Side mounted containers fare much better and the only point against seems to be the extra bulk on one side. This problem has been solved by the bottom-mounted reserves, tucked neatly under the seat with extractor on either side. Unfortunately, these designs are also the most sensitive for proper packing. There were serious problems with some brands – the inner container getting stuck inside. Compatibility of the inner container can be a factor as well. Judged strictly by reliability and safety, the front mounted containers seem to be winning. The most prominent advantage is pilot can reach the extractor by either hand – an important factor especially in mid-air collision when one of pilot's hands my be injured. Reason against: Most of these also serve as an instrument panel, and it is always a compromise. If you are fussy about the arrangement of your instruments, you are not likely to be happy. There are also pilots who just hate to have ANYTHING hanging in front of them.
Regardless of the position of the container, the design of the extractor has also developed in certain direction. I have mentioned the importance of the easy visibility of the pins already. The once popular Velcro holding handle in place is a no-go nowadays. It tends to stick extensively with time, causing the handle becoming hard to pull. In designs where the “hook” side of the Velcro was used on the handle, there also were recorded cases of failure due to lines sticking to the handle… The design of the pins is important too. Some of them tend to get stuck if inserted in certain manner. The plastic ones showed a tendency to break at extremely low temperatures. Every detail counts where your “last chance” is involved. Investigate, before you buy.
Another important design feature is the way how the chest strap closes. Taking off with the leg straps open is often fatal – and nobody is immune to this simple omission. We’ve learned this lesson recently in the most tragic way. Since then there was another similar fatality in Israel and Italy. Some designs, like the popular “fool strap”, offer nothing more than a false sense of security. They can fail easily. The T-Bar design is closer to perfection and it is simpler as well. But even T-Bar won’t help if there are other webbings by their function resembling a chest strap. These include bands holding shoulder straps together, front mounted reserves and instrument panels. There are very few manufacturers that take care of this problem with a reasonable degree of success. Pay a special attention to this part of the design. These “extras” should be incorporated into the closing mechanism of the leg straps. Otherwise they can negate the safety advantage of the T-bar.
The back protector is another part you may not find terribly important – until you hit the deck. No harness comes without it nowadays, but not each off them deserves the name. A bad back protector can make things worse than no protector at all in some cases. The design of this part involves much more than meets the eye. Don’t try to assess the quality yourself. The most reliable guide should be a DHV placard. If it is missing, you have a good reason to have some doubts. There are 2 mainstreams in the design of a back protector. The airbag and foam. The airbag has a distinct advantage in its low volume and weight while not in use. A major setback: Most designs are self-inflating and they are not going to help you during a take-off accident. The foam is bulky and heavy, but it is there all the time, ready to absorb the crippling impact.
It is almost a rule of a thumb: the most comfortable harnesses are hard to get into – and vice versa. Some manufactures solve this problem by fitting a stirrup. It makes slipping in the harness a breeze, while serving as a footrest and weight-shifting tool later in flight. The setback for low-hours pilots is, it can cause confusion while using speedbar. Take it in account where applicable. How you find the harness responsive to weightshift is highly subjective. I often find 2 people reporting opposite extremes for the same product. It may be the way they had the harness adjusted, it may be the wing. Who knows... The only way to find out is to fly with your own wing and try a few different adjustment. Don't discard otherwise good harness because it doesn't feel right on the first try. And, to close the list of important features: look at the size and numbers of the pockets available. Don’t forget to check if there is at least one pocket of a decent size that can be accessed in flight – or more importantly, while you are hanging from a 30m tall gumtree.
Everybody is familiar with the term “Pre-flight checks” and knows what they involve. We all know they are important and the life expectancy of those who neglect them is believed to be greatly reduced. What is hardly ever mentioned – or performed – is a series of “after-launch checks” that are about equally important. Some of the points merely double the pre-flights. Even the most thorough people can miss something for a variety of reasons and there is no harm in checking again. Besides, take off puts extra stress on a variety of your equipment and something what was perfectly right during pre-flights can be in a terrible mess after launch. Some other defects are almost impossible to see expect during flight. Most of the problems can be rectified or at least the subsequent damage can be reduced if the faults are detected in the early stage of flight. I do my “after-launches” religiously and have similar system in them as in pre-flights.
I start with the points that can have a direct impact on the stability and control of my glider:
1) Are the brake lines routed correctly and not wrapped around risers? Aren’t the brake lines heavily twisted creating potential for curling and blocking the pullies? Mistake here happens only too easily and it is easy to overlook it while still on the ground. Any problems in this area can usually be corrected easily as soon as you are at a safe distance from all solid objects and in a reasonably stable air.
2) Don’t I have any tangles or foreign objects in the lines? Isn’t there any damage to the lines? If a problem is detected the action should be matching the severity of the problem and experience of the pilot. If the trouble can’t be rectified by shaking the lines a few times, your next response can be anything ranging from simply continuing the flight to throwing reserve. The latest option should be considered carefully and the action delayed, whenever possible, until you are above a safe landing area. Throwing the silk can be in many cases safer than trying to land with a wing on the verge of stall or spin. Underestimating this kind of predicament can lead to serious consequences. For instance a little twig in the top cascade causing not any immediate deformation of the glider at all can cause a total failure of recovery from a tuck by catching more lines. It may be acceptable to ignore it at the coast but in thermic condition this “detail” should be a good reason for heading to the nearest safe landing area right away.
3) Is the reserve handle secure? The consequences of reserve deploying accidentally can be about as serious as the rescue not opening when needed. The handle can be pulled out easily during launch especially if you have people helping you (Is there anything better to hold you than that conveniently located red handle?). Often you have only seconds to prevent the reserve from falling out. In most cases there it is not possible to restore the device back into a safe and still useable state – in that case the only prudent action is to land ASAP while preventing the inner bag from opening by whatever means available first.
4) Are my leg straps securely closed? It is perfectly possible to take off with the leg straps undone (or they can open during launch) without noticing it. If you don’t check it now, you may first become aware of the crisis when you get in the landing position 20m above the deck. It may well become one of the last things you become aware of - ever. Closing the leg straps (providing you are sitting safely in the harness) is usually easy. If you can’t do it, head for a safe landing area immediately and land the way porcupines make love; very, very, carefully.
5) Are my karabiners properly locked? Most karabiners are designed to lock their gates automatically and then they shouldn’t open without a deliberate human action. Unfortunately, nothing is perfect and you may find one of your karabiners open. No reason for an immediate panic. Even an open one can take easily multiples of the loads produced during a steady flight. However, a bit of acro or a large collapse can cause a total failure or at least an irreparable damage. Close the gate ASAP and make a mental note to check the locking mechanism for a proper function after landing – unless the reason for malfunction was obvious (e. g. a foreign object in the gate). If not possible, land without any further delay.
6) Is my speedsystem connected properly? The Brunel hooks used by most manufacturers nowadays are useless pieces of junk that should have been rejected a long time ago. Unless you use some extra trick to hold them securely together, they will open every now and then (usually during takeoff) rendering you speedsystem useless. If detected early, it is usually easy to rectify this problem. It may become harder if you find out while being blowed back over that ridge… It is also worthy checking if speedsystem is not pulling on the front risers while not in use (line wrongly adjusted or caught on some other piece of equipment). If this can’t be rectified easily, land.
Having finished with the above items, you can relax. There is no indication you are going to die in the immediate future and you have time to go thru some fine details. The following predicaments are not of the “life or death” type, but it is better to discover them ASAP and whenever possible fix the problems before you actually need to use the offending piece of equipment in a hurry.
1) Is my altimeter set correctly? You are looking for an obvious large error – like when right after your launch from Mystic you read 1,500m altitude. It is usually not possible to fix this in flight but you can take a mental note of the approximate size of the error and use it for future reference.
2) Is my GPS (computer) recording? Especially vital in competitions where overlooking this problem can really bring tears in your eyes later.
3) Is my radio still working? Nothing is easier than pulling one of those plugs out of its socket during takeoff. Make another “radiocheck” call and try to rectify any problem you may detect. If you can’t fix it, modify your flight plan when necessary taking in account you are without communication.
So, now you have covered about all what could conceivably have gone wrong after launch. Enjoy your flight but keep looking. There is always something you failed to notice!
I read the XCFiles article about thermalling in the June issue of Skysailor with interest and I did learn a thing or two. But, there were some sections that made me wonder…
I have to admit, I know close to nothing about meteorology and have some tendency to call it a “pseudoscience”. BOM appears to me as a criminal organization siphoning money from gullible people the same way as alchemists were in the dark ages promising something what they could never deliver. Only they are not promising gold, but an accurate weather forecast. Exaggerating here a bit, of course; I really believe meteorologists are nice, hard-working people. But unfortunately, they are dealing with system so complex, it may never be fully understood.
Anyway; I do have a strong background in physics and my knowledge here clashes often with what I read in aviation magazines about the behaviour of the air or an aircraft. In many cases it seems like the authors are trying to bend the laws of physics while in order to find the simplest explanation of a particular occurrence while ignoring the scientistic reality. The undisputable fact is: meteorology has to obey the laws of physics, not vice versa.
The weak part of the above article is the “ridge soaring of a thermal” section. It has to make any physicist wonder, what kind of miracle can cause this work and poor Isaac Newton is surely spinning in his grave. Experience tells us, yes, there is often a lift in front of a cloud. But whatever is causing it (meteorologists, please, do something useful for once and help me here), is not a dynamic lift caused by wind hitting the cloud or thermal.
The “dynamic lift” part myth is caused by the generally accepted (but entirely wrong) view, that if an object is moving fast in a certain direction, the object becomes resistant to forces perpendicular to that movement. This may be supported by a mix-up with Coriolis Effect that is alive and kicking – but it applies only to a rotating frame of reference.
Without going deep into physics, let’s start with a question: “Have you ever done some shooting?” If the answer is “yes”, you know if you are trying to hit a target in a crosswind, you have to compensate for drift of the bullet (moving forward by supersonic speed) otherwise you’ll miss severely. The reason: your bullet will become accelerated sidewise by the crosswind (and also downwards by gravity) as soon as it leaves the barrel. It will be moving, besides of moving forward and down, also sidewise and given enough time, its speed in this direction will match the speed of the wind. The forward speed, however high, has absolutely no effect on how the bullet moves sidewise - or downwards for that matter. It is so hard to swallow, even Mythbusters had a go at the following “myth” – and confirmed it without a shade of doubts; “If you shoot exactly horizontally and drop another bullet from the height of the barrel at the same time, both bullets will hit the ground exactly at the same moment.” The “fast” one won’t be affected by gravity any less than the “stationary” one. The same, obviously, applies to the wind.
Our thermal is not different from the example above. A parcel of air leaving the ground will have zero horizontal speed initially. As it has certain cross section exposed to wind, wind will produce horizontal force, accelerating it in its direction. At this transient stage, there will be some airflow around that parcel. The parcel has a certain mass, so it takes some time to accelerate it to the speed of the wind; v=F*t/m, where v = groundspeed, F= horizontal force applied on the parcel of air, t=time for which the force is being applied. However, this time will be fairly short and our thermal will cover only small vertical distance during this process. If you ever watched smoke rising from a chimney or from a bushfire (just a filthy thermal) on a windy day, you know what I mean. It will be safe to say, our typical thermal will travel by the speed of the wind within a few tens of meters (at the most) after leaving the ground. From that point, the thermal will become a part of the horizontally moving airmass (wind) and its horizontal airspeed will be zero. Even if we treat it as a solid object, it will generate about as much dynamic lift or disturbance to the horizontal airflow as a hot air balloon (a thermal wrapped in fabric); none. There is no horizontal airflow around thermal or balloon except of the brief period of horizontal acceleration after leaving the ground or, higher up after hitting a wind sheer (can it be of a practical significance?). I’m sure, when you see in some Hollywood blockbuster people in a balloon basket with their hair flying and having clothes ripped of them by a howling wind, you have a good laugh. That’s Hollywood. Strangely, we don’t find wind blowing around a thermal equally absurd.
So what have we left? O.K., if you fall out of the thermal downwind, you do will start sinking like a brick. True, but this is not a result of a “rotor” on the “leeside” of a thermal. This is due to the fact, the path of the glider through the transient region between lift and sink is shorter than when leaving the tilted thermal in the upwind direction (A). On that side your exit will be more gradual and less dramatic. This difference is accentuated by the glider always sinking relatively to the surrounding air. The same factors (in reverse) account for the difference in returning in thermal from the upwind direction and downwind direction. Getting back to the thermal after falling out of it downwind (B) will take longer – not because you are “fighting headwind”, but because your path will be longer. Also the entry will be more gradual and the feel of lift will be less distinct. Return path to thermal from the upwind direction will be shorter and the entry will be less gradual; that accounts for the feel of stronger lift. If you would somehow manage to produce a tilted thermal in a still air, the results would be exactly the same.
Thermal doesn’t even “know” there is any wind the same way as your wing doesn’t “know” it as soon as it leaves the ground.
That’s about it. So, next time you get the impression you are ridge-soaring a cloud, remember Mencken's Metalaw: “For every complex question there is always a simple answer. And this answer is wrong”.