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rhys

Thermals and Tandems

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Hi Koni,

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I reckon when the wind conditions get too unpredictable it's best to stop jumping for a while until the winds settle inn/down, maybe wait til later on in the day when the ground starts cooling down a bit.



thats exactly what i did! it wasn't the thermal that was kinda cool it was the 28 knot gusts that came shortly afterwards.

we had a mint sunset load when it all settled down.

Say hi to all in Wanaka and see you in october/november!
"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

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I am not that familier with this site ( quote,reply ect) , and english is not my first language.But I agree 100% with UPOZZOLI and I disagree with DIABLOPILOT. BOBDINO is right, one of the world top hang gliders have been suck to 30000 feets during a competition in Australia from a huge cumulus cloud couples weeks ago. She survive and her GPS prove it all.
Tandems are most likely to be affect by those clouds because we open higher. I did more than 3000 tandems since 1985 and even if I was aware of how powerfull and dangerous those cumulus can be for us I had too deal twice with those under tandem. I can tell you that those clouds can shift from one direction to an other what ever the wind direction is. They suck from the side on some occasion ( my second experience ) and from the bottom. Even a nice cumulus that goes from 4k to 10k ( that's not a dangerous one for us at this point) will generate enought lift even 500 feet under it so you will feel a bumpy ride and if you look at the others skydivers around you'll see that while they go down you stay there .Your alltimeter will confirm you that. Higher the cumulus goes (up to 60 K in some case) whorst is the effect. Customers trust us.It is our job to understand all that for them.

UPOZZOLI. ... thanks a lot, you know what you're talking about and you fight for it. I appreciate.

Richard
When you think you're good...this is when you become dangerous.

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A similar thing happened to me - over the Mojave Desert - 15 years ago. Then it was wave lift coming off the Tehachapi Mountains. I had a large (200-ish pound) student, but ventured too close to a small, puffy, cumulous cloud. The next thing I knew, we were "stuck" at 5,000 feet and drifting towards restricted airspace over Edwards Air Force Base.

The only way out was to spiral until the student got air sick.

Note, several glider altitude records have been set over the Owens Valley, which is just a few miles north of Tehachapi.

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We timed a Tandem canopy ride at 27 minutes once in Empuriabrava with a normal opening altitude of about 4.5K . Because of strong winds the TM could do nothing but hold the entire time. The passengers legs went asleep way before landing. If my memory serves me right after all these years. I think the TI was Fred from Skydive Miami.

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Hey Rhys,

We had major thermals all last year at our DZ due to a farmer soft tilling a quarter section (1/4 mile squared)

The real problem I found was that depending on the landing pattern, you often wound up s turning the piss out of the canopy with no idea when you'd get back into a normal decent. The canopy often surged at 50-200 feet, giving a nice, scary forward speed to where ever you were pointed at the time. Getting the surge during an S turn was quite harrowing if you were faced out at the time. I often ended up setting myself up for landing in areas where you could overshoot or undershoot if you had to.

Another dynamic was that on a no wind day, thermal gusts tended to be unpredictable.

Having a huge landing area was the only reason we could tandems safely on hot days! Of course, we had an extreme situation. Besides, seeing thousands of butterflies at 5000' was quite amazing!

Oh, and for the record, if it's jumpable, clouds don't suck you up, the thermal releasing pushes you up. For the clouds to suck, you'd have to have a massive bitch of a storm with internal convection that you would have to be either retarded or not very bright to jump next to! Ther is no way you'd look at a storm like that and say "ah, it's not that bad". They leave very few questions unanswered!

What causes massive towering clouds is initially the thermal (which are akin to soda bubbles) breaking off and rising (they rise because warm air is lighter). When the warm moist air hits the dew point, is begins to drop its moisture creating the tower of cloud you see building. Surface convection is driving this type of cloud formation, not the cloud itself.

At our DZ, the "house thermal" would start building these amazing towers over the DZ on humid days that would go from 6000'-10000'. It was the most spectacular tandem jumping I'd ever done. We'd get out about 1000' from a tower and enjoy the site all the way down!B|

Now, clouds that have their out convection system are a whole other kettle of fish. Glider pilots get caught in them because they can launch when it's clear and fly the same thermals that can get the nasties going. A couple hours later....:o

In Skydiving, if you are jumping in conditions that would get you caught in a big nasty, then you should have seen it coming long before take off!

It sounds to me like you had thermal activity that day which made late day storms very likely. A storm was probably 10+ miles away and moving fast. When you laded, it sound like you caught the gust front (I've never heard of thermal gusts being as high as 28 knots! Gust front that high are quite common)

Don't worry, you were not getting sucked into a cloud.
I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet.

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Suck is absolutly the wrong term to use when discussing then phenomina. Can you get sucked into a cloud from the side? The top?

I think "sucks" is an okay term for being drawn into a cumulonimbus cloud via a rising mass of air. I think "sucks" also can be used to describe the vitriol contained in some of these postings. Sucking, blowing, doesn't it all mean the same thing.:P

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There is a distinct difference between a thermal PUSHING you towards small, puffy cumulous clouds on a hot summer's day and a cumulo-nimbus (thundercloud) SUCKING you up.

Thermals dump most of their lift (and warmth) when water vapour condenses at the base of the cloud. Glider pilots avoid entering small cumulous clouds becaue they contain little lift, and even less visibility.

Meanwhile, cumulo-nimbus clouds may start with thermals (or cold fronts if they occur at night), but develop their own internal up-drafts and down-drafts. The turbulence in thunder-clouds is violent enough to rip wings off of airliners!
Oh! ... and the hail inside thunder-clouds can ruin your paint job!

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Hi Rob,

Not arguing mechanics, just semantics. I think the poster was getting waaay too much crap for his choice of wording. I've had all that aviation weather training, courtesy of the FAA, and understand the basics of how it all works. ( I got a 100% on the weather test at the academyB|:D ain't I cool?:D). I thought "sucks" was a good way to describe being lifted into the bosom of a thunderstorm.

There are a ton of ways to get killed skydiving. Thunderstorms rank way down on my hazards list, but the cumulonimbus is still the most hazardous cloud in aviation. :)

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Clouds don't suck.



I believe you are wrong.

The release of latent heat when moist air borne upwards in thermals condenses in the cloud adds to the updraught. This is not an issue for most of what we encounter but for big, big Cu-nim type clouds it is a very real issue. The cloud suck under the base of one of those will be much greater than any thermal activity.
Do you want to have an ideagasm?

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That may all be true, the difference between a "thermal" and a "thunderstorm" (in fact it is) but "once upon a time" I came out of the trusted C182 as the second tandem and ended up in a towering cumulus cloud I thought I was going to miss.

The weather could be described as "sunny but unstable, with patches of so called towering cumili that started at 2000ft and grew to 6500ft."

I ended up right in the middle of that cloud and decided to spiral my way out of it. I started to spiral hard at 4000ft and after 20 seconds or so I was still at 4000ft (!), "going nowhere fast".
Knowing the weather situation and the kind of cloud this probably was I decided to fly straight in a random direction (cloud was so thick I lost sight of both ground and sun) on the premise that the other tandem that I had seen in freefall far enough away from the cloud should be at below 2000 by now and that once out of the cloud, the parachute - which at that time was going up again (!) would start to descend normally. As I approached the side of the cloud, all of a sudden I started to go down with twice the normal speed - comming out of it at 2000 ft.

As luck would have it I came out of it more or less where I would have wanted to be anyway, had I seen where I was going and the rest was uneventfull.

Interesting phenomenon, towering cumulus... :)
edited to say that what jakee says about the release of heath adding to the updraft being basically the same as what my meteorology professor told us about this.

"Whoever in discussion adduces authority uses not intellect but memory." - Leonardo da Vinci
A thousand words...

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edited to say that what jakee says about the release of heat adding to the updraft being basically the same as what my meteorology professor told us about this.



Phew, glad someone agrees with me! Its been a while since I've gone gliding and so I decided to make sure my recollection was correct and found this on a meteo website.

" Latent heat of condensation is energy released when water vapor condenses to form liquid droplets.

An identical amount of calories (about 600 cal/g) is released in this process as was needed in the evaporation process. This is one mechanism of how thunderstorms maintain their intensity. As moist air is lifted and cooled, water vapor eventually condenses, which then allows for huge amounts of latent heat energy to be released, feeding the storm.

Condensation is a warming process."

By the by (and I apologise for going off topic) in ye olde days glider max altitude records were set by intentionally flying into the middle of towering Cu-nims! I once read an insane account of a pilot who broke the UK alt record way back when who topped out of a cu-nim at about 33,000ft, encountering huge turbulence, hail, thunder and heavy icing on the way. Apparently it was so bad on the cockpit he could only see out of the DV panel and he had to bang on full control deflection every minute or so to prevent the control surfaces from icing solid. One crazy story!
Do you want to have an ideagasm?

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Apart from the semantics of whether clouds "suck" or "don't suck" (which is just playing with words anyway, and don't warrant the slagging that went on here), I think every tandem master should have some basic knowledge of meteorology, and the causes and effects of weather on airfoils.

When you are rapidly gaining or losing altitude when you don't WANT to...you have a problem. Whether its a minor or major problem can change in a very short time.....

I find it amazing that some seemingly "expert" skydivers on here have no clues about thermals, turbulence and other weather related factors that can adversly affect your health and life while under canopy.....and yes it can hurt you badly or even kill you AND your passenger.

Every Tandem Instructor should be able to look at the sky and assess whether conditions are suitable for safe jumping, its not often these situations sneak up on you.

There have been some good explanations given on here, although the technical terms used might bamboozle a few who read them. Ask someone who knows to explain them clearly if you don't know.

And remember...the skydive ain't over till you are safely on the ground....

I'm absolutely NOT impressed with the individuals who decided to turn this important topic into a slanging match about whether clouds "suck" or not.

There are plenty of people out there with low jump numbers who know a hell of a lot about different subjects than I do. I'm willing to learn off them....not rubbish their views.

If you don't know about the effects of weather I suggest you go and FIND OUT. It could well save your arse one day.....
My computer beat me at chess, It was no match for me at kickboxing....

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Apart from the semantics of whether clouds "suck" or "don't suck" (which is just playing with words anyway, and don't warrant the slagging that went on here),



Not entirely. Clouds do generate updraughts beyond just the thermals that feed them, and 'cloud-suck' is an accepted term in aviation sports that are far more in tune with the weather than us.

But for sure the effect itself is much more important than the terminology.
Do you want to have an ideagasm?

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That was one of my points....and was ALL you needed to say.....

The KISS principle needs to apply.......which makes for much more effective understanding....

I don't really give a rats arse if the terminology isn't 100% accurate.
My computer beat me at chess, It was no match for me at kickboxing....

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I don't really give a rats arse if the terminology isn't 100% accurate.



Some measure of consistency is important though, otherwise no one ever knows what the hell anyone else is talking about;)
Do you want to have an ideagasm?

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Howzit, a few years ago I was doing video for a Tandem in Victoria falls. We exited near a forming Cumulonimbus cloud. The freefall was great with the cloud streaming by making a great background for the video. The Tandem opened at 5 grand, I fell away to make sure they were open ok then deployed. As the canopy opened and I started my checks I saw the Tandem above me colapse then reinflate. As I saw this the same thing happened to me. Half my canopy colapsed then as I dropped it reinflated then colapsed again. This happened down to 800 feet as I flew away from the cloud with clenched buttocks..
I assume it was cold air rushing down the side of the cloud. I try to keep away from those big babys now..
http://mysite.de/wildsideadventures

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