Reverse launches, wind gradients and turbulence

Learning to Paraglide Day 5

The winds just wouldn’t cooperate today, even for learning reverse launches in the paddock. We all got up ready to go, packed ourselves into the basher 4WD with our gear in the trailer, but didn’t even leave. The winds at the top of the mountain were getting stronger rather than weaker over the previous half-an-hour, so that it was currently gusts of 30km/h or 8m/s. So we came inside to do more theory: this time learning about wind gradients, turbulence and strategies for judging whether you’ll clear obstacles. We did head out to the paddock before lunch to learn reverse launches with Bob, but the wind in the paddock then died down so we couldn’t practise the new skill, so more theory instead. We headed out to the paddock again in the late afternoon when the wind had picked up a bit but again it died off on us and we were left standing there “parawaiting”.

Waiting in the paddock for a puff of wind

There was a slight chance the winds would turn before sunset, but that didn’t eventuate either.

Disclaimer: This is part 5 of an 8 part series detailing what I learned and experienced recently while undertaking the fantastic paragliding course with the team at FlyManilla. You can find links to the rest of the details for each day from my overall course summary. I’m taking notes for my own personal reference and learning while it’s fresh, but it’s totally possible I’ve remembered incorrectly and have made mistakes. These are not notes for others to learn from but may give an interested passer-by who is considering a course a good idea about how valuable the course at Manilla is. If you’re interested in learning to paraglide, I’d totally recommend this live-in 9-day course at FlyManilla.

Reverse launch technique

The little practical skills that I did learn on day 5 were related to the reverse launch technique taught in Australia, which is slightly different to that in the textbook The Art of Paragliding by Dennis Pagan:

  1. Layout the glider, untangle and connect your harness as normal (ie. forward facing), checking both risers to ensure the A’s are facing forward and lines on top.
  2. Step back (not on the lines) and lift the right riser above your head, turning to face the glider with the right risers on top
  3. Take your right brake in your right hand and your left brake in your left hand
  4. Take the rear risers of both into your left hand, laying them together so that the quick links are flat and together, holding them in a good grip
  5. With your right hand reach under the risers to take the A’s of both, holding them similarly flat with the quick links together in a good grip

Check that you can now lift the A’s cleanly, building a small wall. If the leading edge rises higher on one side first, step towards that side and try again (in doing so you are adjusting the tension in the lines).

When there’s the right wind, step back and guide the wing up past the power zone (it may pull you forward while passing through) until it’s above your head. If it comes up too quickly you may need to slow it down with the rear risers in your left hand. Once the glider has come up straight and is above your head, you control the glider in this position just as if you were balancing a big broom on your left hand (the one holding the rear risers), moving your left hand and your feet to stay under the centre point of the glider (usually the logo). But importantly, if the glider comes up on an angle you are much better off just bringing it down again straight away, resolving why it came up on an angle and then trying again.

To bring it back down again from this position, pull long and hard with your left arm to bring the glider back down (it feels like a huge amount of brake pressure in this position, but this is because you’ve go the rear risers, not just the brakes). You can even lever your left hand back with your body by hooking your left thumb into your harness and twisting your torso (a technique I learned later from Bob). Importantly, step towards the wing as it comes down to leave the leading edge open ready for the next inflation, rather than collapsed forward and needing help.

Continuing theory for emergency situations

Back in the theory room, after a quick recap, we picked up where we left off from yesterday.

Trees, Rocks, Surf, Water or tailwind towards the shore

If faced with landing in trees, surf, water, a tailwind towards the shore or rocks next to the shore or cliff, what would you prioritise and why? It turns out that the surf and the rocks are the most dangerous places to land for both obvious and non-obvious reasons. With the surf (or water) the danger is our perception that we can just pull the glider out, where as in reality, the glider is like a huge container that normally contains air, but fill just a tenth of it with water and you’re trying to pull around a tonne of water. On top of that, the chance of getting tangled in the lines (and it only takes one line getting caught on you) is very high with the surf washing everything around you.

Even if you have a tail-wind towards the shore, you’d think it’d help to get you there faster, but the risk is that you’re also travelling much faster (remember, your ground speed is your glider’s speed through the air - 30-50km/h - plus the wind speed) and will most likely be landing on an uphill slope (the beach), if you make it. So in reality you’d need enough height to safely get past the shore-line with enough room to land and then do a 180 degree turn for your final approach, but if that were the case you’d not be in the emergency situation in the first place.

The rocks aren’t less risky and are usually a lot bigger than you think from above… so potentially hitting a hard wall of a large rock at 40 kms/h is not going to turn out well. Also the bottom of the edge of a cliff with a sea wind pushing up over the cliff is where you’ll find rotor winds which should not be mixed with landing a paraglider on rocks.

Generally, if you’re a good swimmer, the calmer water out behind the surf is going to be the safest option as long as you prepare for a water landing early (ie. undo your harness early, arms out of shoulder straps) and get out of your harness as you land, swimming underwater in the same direction away from your glider. But it is still risky due to currents that could quickly bring your glider towards you, so don’t stop moving away from it.

Trees are relatively safe, especially coastal trees which tend to be softer than the drier trees inland. See the earlier notes on tree landings.

Wind gradient

A wind gradient is just the slowing of the wind closer to the ground due to friction with mountains, buildings, trees, shrubs, grass and sand etc. It happens both near the surface through to high in the atmosphere as the slower moving air below is still causing friction for the faster moving above.

This can be very noticable when coming in to land which means you can easily overshoot your approach or just find yourself creeping forward on your figure-8 beats. You also need to account for wind gradient when in a thermal as the thermal may lift you up to faster wind potentially pushing you further back behind an obstacle or mountain into the lee-side or sinking air. In this situation you’ll find yourself facing a faster headwind to be able to get back.

On a smaller scale (10s of metres), it can also be significant during takeoff, especially on a cliff, where the wind coming up over the cliff from below can form a compression at the edge of the cliff, which compresses the wind gradient also, so the changes in wind speed per metre of height can be much greater. There are quite a few incidents where people take off on a coastal site in strong winds, but within their limit, without realising the a few metres above their heads (ie. where their wing will be) the wind may be much stronger, sending them backwards on take-off and unable to get back.

Minimum sink, best glide and speed bar

To achieve the minimum amount of sink, you actually need to travel slower with 10-20% of brakes (to the carabiner level), gaining some lift potential by increasing the angle of attack and a larger curvature of the profile. This is often what you want to do in a thermal to get the best lift, but not what you want if you want to achieve the best glide distance.

Best glide speed, on the other hand, is usually the gliders trim speed (ie. no brakes, hands completely up). This will give you the best distance for the height.

The speed bar is used to change the profile of the wing, basically giving it less camber resulting in faster speeds, but less lift. When you’re flying into a headwind, the speed bar will give you a better best-glide (as you’re travelling faster into the wind, even if you’re descending faster). You should only use the speed bar in smooth air, as it flattens out the wing making the glider more susceptible to a frontal collapse in turbulence.

The speed bar can also be used to descend more quickly together with big ears. Don’t use it much, if at all, when low to the ground as the extra speed that you’ll have means a longer recovery time for a frontal collapse.

360 degree turns

360 turns are used when thermalling but there are a few things for the novice to watch out for:

  1. Look for traffic and objects along the whole path of your circle, not just the direction you intend to turn,
  2. Check that you have enough height as a turn with 20% brake input correlates to about a 2m/s loss of height so it takes 15 seconds to descend 30 metres while turning (obviously depends on how flat your turn is),
  3. In traffic, ensure you’re turning in the same direction as everyone else,
  4. Since you’ll normally be flying in wind, you will be drifting while doing 360s, so you need to be careful around hills and cliffs. You can even use your 360 to determine the wind direction - pick a point such as the corner of a field then do a consistent 360 at 20% brake and check your position afterwards.
  5. Normally you’d not need to go past 20% (carabiner level) of brake input. Be aware that a tighter turn leads to a higher loss of altitude. With a spiral you can achieve 20m/s vertical speed, compared to 2m/s for your 20% brake turn.

The Foreground/Background method for judging whether you’ll clear an object

A simple technique for checking whether you are going to clear an object is the foreground / background method. If a forground object that you are trying to get over is rising relative to the background object behind it then you won’t make it at your current descent rate. This method works on both small and large scales (ie. the bush in front or a mountain in front).

Problems with flying in rain and snow

Reasons not to ever fly in rain:

  • With rain you can stall at 50% brake due to the loss of the coanda effect as the air isn’t sticking to the wing as it passes due to the droplets disturbing it’s path.
  • You also have more sink in rain, as the air is being pushed downward by friction.
  • Water enters the cell openings at the front of the wing, filling the trailing edge which affects braking among other things.
  • In the event of a collapse, the wet material will stick together both inside and out leading to a delayed recovery from a collapse, if at all.
  • The normal 5km visibility is not possible. Also the rain hitting your eyeballs when you’re travelling around 40-50km/h hurts (and glasses don’t make it easier to see).
  • Hypothermia is a possibility if you’re flying with wet clothes and have relative winds of around 50km/h.
  • The pilot and clothes gets heavier too, so the stall point is at a higher speed.
  • Don’t use bigears, or if you do, do so with the speed bar for extra speed to avoid going parachutal.

Just don’t go flying in rain or potential rain. In snow you have all of the things mentioned above for rain, and additionally

  • snow accretion on the leading edge changes the shape of the wing so that a stall or going parachutal is more likely.
  • running in snow is hard, then there’s the danger of slipping, so the launch location needs to be chose wisely.
  • physiologically there’s not enough O2 o take off at certain altitudes (eg Mt Blanc experience)
  • thinner air also means you need to run faster (on less oxygen) to achieve the same lift.
  • snow makes it hard to see the terrain, to know for example when to flare.
  • Cables from chair lifts can get in the way.
  • Often there’s a downward slop wind (especially in the evening when places go katabatic).
  • Frozen lakes are not the perfect large, flat landing field. They are treacherous, don’t land on them.

Wake turbulence

Wake turbulence is mostly seen in the swirls of air that are created on your wing tips as the air escapes over the tip. The whirls of turbulence are accentuated during turns, so be careful flying close to other gliders generally but especially in areas of heavy turns, as the turbulence can cause collapses. As you’d expect, wake turbulence flows with the wind, so even if you’re off to the side but down-wind you can be affected. Wake turbulence can last much longer in smooth air, just like the wake from a jetski on a lake will last much longer and travel further than the wake from a jetski in the surf, as the rotors don’t get disturbed by the churning water.

Wake turbulence can also be an issue during take-off if someone flies past below the cliff line and the wind is moving up over the cliff, so be careful! Obviously there can be a much larger wake from powered aircraft such as para-motors or helicopters and you can even run through your own wake in certain scenarios.

If you are expecting to hit wake (or any) turbulence, apply some brake, 10-20% as you anticipate to run through the wake - which is not something you want to do during takeoff where you just avoid wake turbulence by waiting after another glider passes by.

Flying amongst hang gliders

The biggest issue flying with hang gliders is the different fields of view. A hang glider pilot should check for traffic before they turn but as soon as they roll to begin their turn they cannot see in the direction they are turning due to the wing above their head, so be very careful of getting in their path. They also fly 50% faster than a paraglider and so need to react faster to unexpected incidents. If you are ridge soaring together with hang gliders, don’t make sudden unexpected turns. Normally they should pass you on the inside as per the rules (because you will be doing figure 8’s away from the ridge), but they will sometimes give you a wide berth and pass you on the outside of the ridge.

Hang gliders also fly different patterns to a paraglider which can make their turns unexpected to you. When circling in a thermal a hang glider will be further outside in the circle, but again due to the wing above their head, they will need to roll back flat every quarter of a circle to be able to sight who is on the inside and verify that they are still turning safely.

Paraglider wear and tear

There are a number of factors contributing to the wear and tear of your paraglider, including

  • physical / mechanical wear and tear,
  • UV sunlight, chemicals and fumes from chemicals (don’t store them in a shed with paint tins or similar),
  • salt water which impregnates salt into the material of the wing or lines making them abrasive when the material rubs together,

If your glider does get salt water on it, put it in a bath tub of fresh water then drip dry, then repeat with a tub of fresh water etc., continuously diluting the salt.

The harness can also be affected by UV light too, so like your glider, don’t leave it in the sun. See the checks at the end of the operations manual for other items to avoid.

Examining the condition of the glider

A visual check from the riser attachment loop through to the lines for cuts, tears or abbrasion, then the lines themselves and their sheaths and/or loop stitching, then check the stitching joining the loops on the under-canopy surface to the lines on the glider, then the lower and upper surface of the glider, as we did on day one. You can do a manual, mouth based porosity check of the upper and lower surfaces. You can check for kinks in lines by pushing the whole line through as S-bend in your hands.

You can also pay to have this done professionally, checking the material tear strength as well as porosity and line stretch and strength.

Getting repairs

Small tears in the canopy can be repaired yourself with special tape, though be sure to always cut the ends of the tape to smooth semi-circles. For other work, Manilla can assess the damage and either send it to their repairer in Perth or back to the factory in Switzerland. Be aware of taking your wing for repairs to a sail-makers loft or a skydivers loft - they may repair the damage so it will be flyable but it may not be a pretty job.

Landing in strong winds

It’s more important than normal to ensure you are landing into the wind and this should be easier to see. The main thing to remember is that you should not necessarily flare: either flare very gently (10 or 20% brake) or not at all as you may not need to slow yourself down too much due to the wind strength but more importantly, you want to minimize the time that the wing is in the power-zone behind you. As soon as your feet touch the ground, turn and run towards the glider (wraps on the brakes if necessary) to avoid pulling on the wing as it falls through the power zone.

Remember, when you touch down, your weight is transferred from the wing to the ground, so the wing finds it’s not weighted by your body and falls back automatically.

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