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Collapses - how normal are they?
Posted by Judith Mole at 2010-05-29 13:30

I got the following email from a member and wondered what others thought? Any advice/observations?

"At the Mynd last evening [Friday, 28th May] I made an innocuous turn of less than 45 degrees towards the hill in the middle of one of the 2 bowls (on the left) with another glider nearby, valley-side. As I turned I had a collapse of some sort; I felt weightless, dropped a bit, my wing re-inflated and I carried on flying. The whole thing lasted only about 2 seconds but I've never had one before so it was a shock. It is very reassuring to have find out how well the wing recovers. Conditions were still thermic and it was still gusting a bit - can I learn anything more from this other than that the conditions make such an event more likely. How often do you experience collapses? If you often enter very rough air can you expect a collapse every now and again?"

Posted by Judith Mole at 2010-05-29 14:25

My view is that asymmetric collapses are quite common in thermic air. In my experience, having only flown DHV1/2 and DHV2 gliders, they are usually pretty small and you hear them popping out before you even realise that there was a collapse. Although I used to think these were worrying, I find them less so now, so long as they a) don't induce a turn and b) don't make you drop too much. A collapse that makes you feel weightless is a bigger deal.

The vast majority of wings these days are designed to recover with minimal turn, but the if the collapse is great enough to cause you to turn, then the most important thing is to counter the turn and fly away from any obstacles/hill/other pilots. Never mind your wing. It will happily fly with more than 50% of the surface area collapsed, so you need to get the flight direction stabilised (using weight shift) and then worry about getting the wing back into the right shape.

There are many theories of how to do that, but I think currently the accepted wisdom (and please, please others chip in on this if you think I am mistaken) is for a frontal collapse - hands up. For an asymetric, give the brake a shape tug and release. The term 'pumping' is misleading as repeated tugging achieves less than one quick, but slightly harder stab.

Ok, so how to avoid them?

Thermals can be rough around the edges, but in the UK we usually get nice benign ones that just cause small collapses, rather than the big 'blowouts' you hear about abroad on higher rated wings. The stronger the thermals the more likely it is that the air will be turbulent. There are various forecasts that predict thermal strength, so not flying in the part of the day that is predicted to have the strongest thermals is probably advisable until a pilot has more experience, has learnt good wing control skills, can handle a range of collapses and, most importantly, doesn't get freaked out by them. (It's very off-putting and can set your confidence back if you have a very disconcerting rough collapse). Wind and thermals combined very often make for rough conditions.

The other factor is terrain and wind direction. If the wind is slightly off, the bowls on the Mynd can be rotory and therefore flying into them can make it more likely that the wing will collapse. It's always important not to fly too close to the out-of-wind side of a bowl and closer into the into-wind side. Bowls are also excellent thermal triggers, so the air will funnel up the bowl and release there, so it's likely that there will some turbulent air there.

Personally, having come from hang gliding, it has taken me some years to accept and cope with collapses (any rustle above me used to send me into spasms of panic - 6 years on I am a lot more relaxed about it all!). As I have gained more experience, I have started to fly in more rough, thermic air and am less worried about it. I spend a lot of time in the air, so know my glider well and because I am current, my muscles are pretty relaxed in the air, which aids smooth glider control skills. I can't say how many collapses I have in an average flight, but very few if any at all.

I would say on an XC flight probably more than I am aware of, but that's because they are small and I don't pay them any attention. Worrying, big collapses have happened to me lately only on two flights: 1) when I flew over a quarry on a recent XC flight and I really, really should have known better and 2) on another XC flight when I got low and there were things kicking off below me. Otherwise, it's been a fairly uneventful season for me so far!

Hope this helps. Please everyone else, let's hear your views...

Collapses
Posted by Roy Dade at 2010-05-29 15:36

Hi Judith

I agree with everything said here. From personal experience I piled in after a collapse at low level but thankfully walked away, well limped more like. The wind then was strong and gusty; how often do we read that in accident reports? It was also 12 years ago when wings had less passive safety, today things are much better.

After having a very close call I spent the winter reading everything I could get hold of concerning meteorology, Dennis Pagen, Tom Bradbury etc. Since then I have avoided strong winds especialy when things are looking very thermic as the combination of dynamic and thermic turbulence makes it unpleasant as well as unsafe.

Also I think its good to get high where its generally smoother, less chance of tucks and more height to sort it out if something does go wrong so if you are on take off on the Mynd go out and up before beating off over those big bowls.

Make sure too the chest strap is set as per the glider manual. I recently discovered a new CP whose chest strap was set at 55cm, having brought it down to 46cm he felt much more in tune with is glider and able to sense what was going on above. It was much easier to steer without masses of weightshift he reported.

Finally I would srtongly recommend geting in touch with a coach and getting on with the Pilot rating which will develop the kind of knowledge skills to help undertstand, avoid and deal with collapses as well as a host of other stuff! Better to be over qualified I think!

Regards

Roy

Posted by Pete Cook at 2010-05-29 16:40

Umm, Roy I must watch out for you "beating off over those big bowls" ...
Mmm, I didn't realise you could do that sort of thing at the Mynd...

Posted by Dave Thomas at 2010-05-29 21:36

The key to collapses is to avoid them. There are two ways to this, first one is like Judith says and that is avoid the most turbulent air conditions and especially terrain considerations - this really does make a huge difference. The second one is called 'active piloting' which is something that is often not particurly well explained during training. This involves flying by the weight on your brakes, if a wing is about to collapse asymetrically the brake will go light on pressure - you immediately lower your hand to regain the same 'normal' brake pressure, and then progressively bring your hand back up to the 'normal' position with the 'normal' brake pressure. This will in most cases prevent the wing collapse in the first place, and is something that has to be practiced with thought and care for it to become instinctive. There is a potential downside to this for low airtime pilots, it can leave your hands in unusual positions which can be confusing and disoreintating to recover back to the correct status quo. If done correctly the wing remains above your head at all time, never turns and never collapses or if it does, it is never seen, but goes as quick as it comes.

Last week I actually got to see my wing collapse, It's a very unusual experience but I was looking up at the time, and probably wasn't concentrating well enough and let it happen in the first place. Everything is normally controlled through the feel of brake pressure, you don't have to look at the wing at all once in the air. When I first moved from HG to PG - I had to look at the wing about every 10 seconds to believe it was still up there!

Full frontals are different, and I can't give much guidance on those, as I've only had one proper one and it was enough to get me to land immediately as I was close to the ground and it spooked me - I was flying a renowned extremily turbulent quarry site. Others may be able to advise better but I think it's simply a case of using both hands to control the weight of brake pressure, just as you do to stabilise the wing during normal flight as the wing dives and hangs back in any thermic conditions.

Hope this helps, but if unsure, please contact a coach and they can watch your flying, and advise on your technique. Ground handling in light conditions is perfect for you to practice this - when it is light enough so that you can only just keep the wing above your head by constantly having to apply and reduce brake pressure.
Dave Thomas LMSC Safety and Chief Coach

A good link on Paraglider Collapses
Posted by Andrew Donnison at 2010-05-29 23:04

http://www.footflyer.com/PPGBibleUpdates/Chapter19/WingCollapse/handling_paraglider_wing_collapses.htm

Posted by David Broughton at 2010-05-30 09:38

Collapses used to be a lot more 'normal' than they are with today's modern wings so long-term pilots probably don't think think they're such a big deal.

It's better to go 'neutral' (hands in ears!) than to over-control incorrectly. The wing is designed to fly and will do if you let it.

Coming from another angle - suppose your canopy was effectively rigid and COULD NOT collapse. How might it behave in very turbulent air ?

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