Residual evening thermals - A cautionary tale

[norbertflyer]

Just a quick heads up on these hidden monsters. Took off immediately after the Spain match yesterday evening into a southerly 3mph wind direction (prevailing wind was east, with a northerly component above 1200ft asl). Bimbled around the fields about 800-1000ft agl in an approximate 7km radius circle, with only very slight occasional turbulence, but mostly smooth air. 30 minutes into the flight - Bang, left wing collapsed and a cravat. WTF. 10 seconds later after 4 pumps to get the cravat out, I was going up at 600ft/min, but concentrated on recovering the wing and maintaining direction. Where did that come from? Exited the thermal with a couple more minor collapses and back to all smooth again. looked round and thought nothing of it, but noticed that a motorway service station was near me (Lots of black tarmac and retained heat from a very sunny day). Variable wind directions gave me no clues otherwise. The cooling evening air must've had a significant effect on the thermal strength, but completely took me by surprise.

Caught out good and proper (that's despite 550 hours on paragliders with several thermic cross country flights in the UK and abroad).

I won't mention the wing name but its a certified ENB paramotor wing, it was in the certified trimmer setting and I had my hands on the controls at the time.

No issues for me in that situation, given my experience, but may serve as reminder for others with less air time during this wonderful spell of hot sunny weather.

Happy uneventful flying!

Richard

[Lee Jackson]

Thanks Richard... a good reminder to keep your wits about you at this time of year. What sort of time was this (not having seen the football)?

8.00am Sunday morning was uncharacteristically thermic in my neck of the woods too. Lots of hands on flying!

[alan_k]

The sun would have been up for a few hours by then Lee, so not so surprised really.

[Graham]

This reading is what being a club member is all about, thanks.

[Lee Jackson]

14 hours ago, alan_k said:

The sun would have been up for a few hours by then Lee, so not so surprised really.

Hi Alan, ha yes point taken, but it was really quite punchy for such an early hour. I've been doing quite a lot of early flights without it being that thermic.

I guess hot days, back to back, has allowed the ground in towns etc to retain some more of the previous days heat before the next day starts. Maybe obvious to seasoned pilots like you, but no harm in mentioning it.

Look forward to catching up with you at the fly-in 

[Guy]

On 26/06/2018 at 22:52, Graham said:

This reading is what being a club member is all about, thanks.

I fully agree. I'm very cautious about strong thermals, particularly in this glorious weather we are having. As a very rough rule of thumb is there a height at which they may well be expected to loose their strength. I rarely fly above 1500 ft but if generally it would be better at 2500 there are times I might be happy to sit up there (although I do feel that you loose the connection with the ground at that sort of height).

Any ideas?

[HangTen]

A recent example of this.  July 2, 2019

 

 

Edited July 8, 2019 by HangTen

[AndyB]

The collapse coincided with him pulling left brake.

[HangTen]

I have not yet begun to enjoy the hobby yet.  But hope to start acquiring equipment this fall.  So you folks that have lots of hours under an inflatable wing have a great deal of experience with thermals and their effect on wing collapses.   Some of my thoughts....

The rising air part of a thermal (core?) seems less dangerous in and of itself than the falling air part of a thermal surrounding the core with relation to an inflatable wing and lift.

Seems as though you might be more likely to encounter a down draft before actually encountering the updraft associated with most common thermals.  The down draft probably being much more likely to result in a wing collapse.   I'm thinking as far as paramotoring is concerned, watching the terrain below for dark areas that might absorb / hold heat should be treated as areas that could potentially hav down drafts surrounding them during summer months?

That said, being very aware also of any sudden feeling of losing altitude could possibly indicate (along with ground terrain) that you may be entering a thermal down draft before you enter the strong core up draft?

All just food for thought.....what are your thoughts?

Edited July 8, 2019 by HangTen

[HangTen]

34 minutes ago, AndyB said:

The collapse coincided with him pulling left brake.

Thanks.   Good to know.   Did you see him pull left brake in the video?   (As a noob I'm wondering how you knew) ? 

Maybe the wing was already on the verge of a collapse before he pulled Left Brake?

Edited July 8, 2019 by HangTen

[alan_k]

That was a pretty big collapse and I'm in the dark as to why exactly it happened.

Anyone know what type of wing it was, reflex or not? I'm guessing the air was pretty unstable, it looked it from the previous minutes footage. So too much thermic activity at the time to be flying (safely)?

I have never even had a tip tuck but then I fly a reflex wing in calmish conditions.

Thoughts anyone?

[Steve]

Hard to be sure of things like how thermic it was. It did look like he might have pulled left brake just before the left half of the wing went. Hard to be sure though. I would say he was too low for the terrain he was flying over. 

[chrsfrwll]

1 hour ago, alan_k said:

Anyone know what type of wing it was, reflex or not? 

According to his YouTube channel it was a Sky Flux.

Comments suggest a 50 degree wind shear at 200/300 feet with 5kt below and 19+ above.

[asquaddie]

1 hour ago, chrsfrwll said:

Comments suggest a 50 degree wind shear at 200/300 feet with 5kt below and 19+ above.

Well, let's hope we don't get one of those......

It looked unrecoverable if it was not user induced.  

[HangTen]

In the video above the POV is from the rear.  As if he was using a chase cam, but if so it was all over the place.   Plus the distance seems to vary?   Does this look like footage from a chase cam or was someone behind him in another paramotor?  If so, that was awfully close?

I agree with Alan_K in that it looked like there was considerable turbulence in the video.

At 1:25 you can see both his hands if you set the video to HD.   They looked even prior to the collapse and even though his left hand appeared to move forward at the instant of collapse, to me it looked as though it was in response to the collapse.  Of course your trained eye may see it differently.

Edited July 8, 2019 by HangTen

[Patrick1]

The pilot who posted this on YouTube deserves praise, it’s by sharing these things that others learn. I hope he has a speedy recovery and at least he’s now got a cool story to tell in the pub.

Watching the video, I honestly don’t think that was pilot induced in any way, it was a nightmare scenario and to some extent he was just unlucky.

At the end of the day, he survived which is reassuring, however, it’s possible that there are some things that other pilots could do to mitigate and reduce the risk of this happening to them.

 - Height. Height is your friend, this gear generally sorts itself out if you have enough height and it gives you time to throw a reserve. Flying low is fun but comes at a cost so save low flight for benign conditions.

- Glider. I don’t know what version of a sky flux he had, or if another glider would have behaved differently but generally speaking, a more advanced glider will be far less forgiving. Think carefully if you really need a more advanced wing. 

- Speedbar/trimmers. I have to confess, I don’t have trimmers and have no training on them so I’m willing to be corrected on this but assuming they behave like a speedbar, applying trimmers makes the wing less likely to collapse, but when it does go, it really will go. In the video comments, our man says he let the trimmers out and that would have made a collapse much more pronounced. To that end, don’t put trimmers out when low unless in clean air, even then, think twice. Again, height is your friend.

 - Conditions. The narrative on the video noted the wind at take of was benign but it got knarly quite quickly. That also appears to be the case on the chase cam which is all over the place. Bad air increases risk of a collapse.

In summary; this was shitty luck and my worst night mare but even so, he survived so there. If you want to avoid a similar situation maybe fly higher, leave trimmers in if low, particularly if you are being bumped all over the place in bad air.

I broke my back flying (pilot error, I was too low, it was only a minor fracture). My back surgeon gave me some good advice along the lines of, “don’t stop flying, most of the people I see fall in the shower, there’s risk in everything”.  

 

 

[HangTen]

I spoke with the fella in the video on YouTube.   He says he did not pull left brake.   It was purely unexpected wind sheer.

Edited July 9, 2019 by HangTen

[mrbell1984]

.

Edited May 17, 2020 by mrbell1984

[Dariuszk24]

1 no reflex wing, no trimers or trimers fully in.

2 very,very big mistake attaching camera on the string= additional drag ,wing is flying very close to stall point,no need to much to get colaps like this.

on video you can clearly see rear camera(string one) its not in centre,but exactly on the left,

problems with harness setting ,pilot relay to much on torque compensation by paramotor (pulling to right when on gas),some moments its wobbling and try to twist him.no  feel wing

In fact drag to the left side wing+torque to the right side =disaster  

 

[AndyB]

On the FB Paramotor page there is an explanation from the pilot. He says it was very lumpy evening residual thermals. He says there was a big wind shear at about that height.

I still find it difficult to comprehend this type of collapse as I have never had one. I fly in what I think is very bumpy and rough conditions, yet I have never even had so much as a tip tuck in. I fly a safe (ish) Roadster 2, but I am on the lighter end of the loading scale (heavier loaded = better stability as it helps prevent collapse). I fly at any time in the UK summer and often in the 2 pm full sun thermals - yet still no collapse.

As for attaching a camera on a string - I think the force exerted by that device at about 25 mph is not a lot ie. it is not going to have much effect.

[HangTen]

Too bad we cant wear some sort of IR goggles and see the thermals.

[AndyB]

I think what hit him is more than just a left over thermal.

Firstly, he describes feeling a wave of air hit him. This never happens normally. When you are flying there is 25 mph (approx) of constant wind in your face, regardless of direction. To feel a blast of wind means a really BIG gust.

Then, if you watch the wing fold in slow motion, it collapses back and down...and keeps going down. It is more like the edge of small twister!

Thermals do not have severe wind shear with a downward direction, they go up. And yes, I know the air comes back down, but it never does so with the same severity as the up draft.

[admin (Simon W)]

I wonder if the cable from the chase Cam or the Camera on his helmet (which came off) prevented chance of recovery? 

It's been know for Helmet Cams to both cause collapses and prevent recovery from them when the lines get tangled. 

A cable with a nice weight on it dragging behind me would be pretty much the last thing I would want in this situation. 

SW

 

[AndyB]

Yes, I have wondered about helmet cams. I often get lines caught on it when I land.....and it takes a fair bit of untangling!

[Thomas]

There is one more possibility that no one seems to be noticing.

I watched many and i mean MANY crashes on youtube and there is one possible explanation.

The only time i`ve seen such a sudden collapse out of nothing is when you fly into a turbulence caused by an aircraft, especially helicopter.

Any aircraft causes huge turbulence that in calm weather could last for several minutes. 

Guy is flying around the airport...;)