tdog
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Quotei was terified of the dark....so i would stand by the light switch and turn it off,
Quotei was afraid of snakes so i bought a boa....then another one.
Someone after my own heart!!! As a kid, I had a lot of fears. Heights, rollercoasters or spinney rides, needles, speaking to crowds, going fast – all things I avoided or could not do…
One day – I just said screw this – and I tackled my FIRST fear --
Heights = I climbed a 120' ladder straight up to the "grid" above a stage. The grid had metal grate floor so it appeared you were walking on air – with gaps for pulleys that you could fall thru if you did not step over - and stayed there until I felt ok about it. The next week I rappelled auzie style off the same grid.
Once I was ok with heights, then I knew I had a “system” to cure the other fears.
Rollercoasters = rode everyone I could. (Last count, over 130 different rollercoasters, but it only took two to cure my fear.)
Needles = gave a shit load of blood. (Excuse me nurse; what is the biggest gauge needle you use???)
Speaking to crowds = tried acting on stage then volunteered to teach a class.
Going fast = can you say 120MPH on my sportbike?
What I have learned about fear is that once you tackle a few – the rest are easy. And, I think I am more willing to try new things than my friends because I know how to tackle fear head on. Most of my friends say, “I could never stand in the doorway of a plane”. I say, “That is one of the most fun parts. You should try sticking your head out and spotting, that is a trip.” -
QuoteWhat good is that brinks
truck following your hearse going to do???
A business professor told me 6 years ago - "Remember, when you die you are worth only what your organs will fetch on the wholesale market. Give all your money away before you die." That is what I am doing, I am giving it all to the DZ. ;-) -
QuoteWould you mind putting that into the Safety & Training forum to start a conversation there maybe? Because the more people that see it, the better.
Wendy W.
Per Wendy's (wmw999) request - here is a cut and paste of a post I made yesterday about a canopy colapse on landing... I am not an expert, take it for what it is worth.
I did not see anyone yet talk of thermals. I am much more experienced in paragliding than skydiving – and in paragliding we really respect the thermals as they are what we need to fly – but at the same time can cause all sorts of havoc close to the ground. The following MAY HAVE NOTHING to do with this incident – but is food for thought.
Thermals are bubbles of rising air. They might extend all the way from the ground to a cloud or they might be just a bubble. I have been told to study a 1970 hippie lava light, as the rising lava in the light is nothing more than a thermal.
If a thermal bubble leaves the ground and rushes up in a column of air, there is a void that must be filled - with the same amount of air going down or sideways outside the thermal as is going up in the thermal. Again, think of the lava light – as the lava rises, the oil fills the void where the lava was. In other words, if you land near a thermal that is bursting, you can be in the middle of a gust of wind that is going down or sideways filling the area under the thermal. I have been in a thermal that went up at 1,400 feet per minute – which is faster than a lot of jump planes. Somewhere there must have been air going down 1,400 feet per minute to fill the void.
If you see a wind indicator (wind sock) quickly change directions, you might have just witnessed a thermal near by. On a quiet day in a field of tall grass you can hear them leave too, just a quick rustle of the grass is all you hear.
A lot of times thermals are the most aggressive close to the ground as they are narrow and get wider as they go up. They can be explosive off of a super heated asphalt driveway or black roof. There are some “surface tension” forces that keep the thermals close to the ground until they break off. If the wind changes a bit, it might be all it takes to make a thermal release.
In paragliding, you know you are about to enter a thermal when you start to feel turbulence or even go down a bit. You actually judge your angle of attack into the thermal by looking at how the wing turns as you enter it. If your wing flies straight but surges back evenly, you entered it straight on. If your wing turns, part of your wing hit the thermal first causing the turn. If your wing surges forward, you probably just left the thermal.
It is very easy on a large paraglidng wing for half of your wing to be in a thermal and the other half not – causing all sorts of fun things – like asymmetric collapses. You could “hear” them in your wing all the time, they sounded like fabric getting loose then springing tight. Big asymmetrics could collapse more than half a canopy.
On very active thermal days, only the advanced would dare to fly paraglidng canopies/wings because you could experience all sort of "asymmetric collapses” or other dynamic unexpected events.
Paragliders are rated by DHV ratings, 1 thru 4 where 1 is the safest to fly, which rate their handling in stalls and collapses. My DHV 1 GIN Bolero glider turns 90-180 degrees in an asymmetric collapse and must spontaneously recover to get the DHV 1 rating. Gliders rated higher might need pilot intervention to recover from a collapse. Turning = loss of altitude = hit the ground hard any way you look at it. Have you ever studied what might happen to your canopy under an asymmetric? How do you fix it?
To avoid thermals close to the ground, I avoided ground treatments that absorb heat, like rock (pea gravel) or cement. In paraglidng – we liked the green soccer fields, but I don’t think DZ have those. ‘-)
Thermals are caused by heated air on the ground being abnormally hotter than the air above. They “break” off of any pointed object, as small as a shrub. We were taught – turn the ground upside down after a rainstorm and anywhere water would drip off is where thermals rise. It is a mistake to think thermals only happen on hot days, because temperature difference, not just warm air, causes thermals. If the atmosphere is cold and the tarmac is hot – expect a greater thermal than normal even if the outside air temperature is freezing.
There are all sorts of mathematical equations used to predict thermals and the strength of thermals, some available on the 1-800-WXBRIEF FAA Flight Service Center pre-flight briefing system, such as the “wave soaring forecast” and the “K index”. The K index measures stability in the atmosphere. You can also speak to a pre-flight briefer who can help interpret the data – but since I don’t speak pilot, I was always intimidated to talk to the humans and only played the recorded messages.
If you are interested, you can study the “lapse rate” which is the phenomenon that as air gets thinner higher you go up in the atmosphere, the air pressure goes down and so does temperature. Physics says pressure and temperature are related due to fact higher pressure causes molecules to be closer to each other. Pure science says that the “dry adiabatic lapse rate” is 5.5 degrees per 1000 feet. This means, if you jump out of a plane 12K above the ground, expect it to be 66 degrees colder at 12K than at the DZ because the air is under less pressure.
But our flying areas do not exist in scientific test tubes – there is instability in the atmosphere. If the actual temperature, lets say 2K up, is more than 11 degrees colder than the ground temperature – you are bound to experience even more aggressive thermals than normal as the atmosphere tries to find balance.
Oh, thermals cause clouds – the reason why paragliders fly “cloud streets” of thermals across country. It is possible to experience “cloud suck” also, where the thermals are so strong you get trapped in a cloud and must use advanced techniques to lose altitude.
Note – I am not an expert at this. Someone with more experience is invited to correct me. But my point is, aggressive thermals can cause turbulence close to the ground, which can very easily cause landings to be rough.
EDITED TO ADD PHOTO. -
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I'm not saying that would have fixed your problem but an experienced canopy instructor / test pilot has pointed out to me that your method of pumping brakes for end cell closure is a common misconception although the slowing it causes will get you there in the end, holding brakes gets you there faster and more consistently.
Pump to bring the slider down but hold to open end cells.
Anyone else comment - slow wing vs pump for closed end cells??? I was told to pump, but at the same time they recommended a flare first in the controllability check because it would kill two birds with one stone. (I just realized that saying is not the best for skydiving.) -
Quote1 in 63 jumps.
Not sure why the "top tiers" of the community is exempt from voting though...
My intent was not to exempt the very experienced - but to isolate equipment that might malfunction more often (where the experienced jumper is willing to accept that risk in exchange for some other desired result). -
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Aside from some second looks and a smile or two from the flight attendants while boarding the plane.
I just flew to California on business. I always ask for the exit row - but never get them - for the extra leg room. I got it both ways. I thought, "I bet I would get weird looks from those-in-the-know if I sat in the exit row and had a rig under my seat. When the nice but serious flight attendant told us how to open the door, she did have a concerned look when I laughed quietly. I could not help it, I was thinking about an airbus exit using the inflatable slide.
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I think most students KNOW not to do low turns - it is that they FORGET when a -tree/rock/plane/hangar/car/insert other noun here - all of a sudden appears in front of them and they panic thinking turning is like a car in 2D space.
This is where I bet a lot more training could be used... It is common to demonstrate your your cutaway moves - but how many instructors make students show emergency landing moves before they leave the plane? -
QuoteYou said instructor #2 caught up to you and grab on, that must have been one hell of an exit to shake your instructor. I know all of my 2 instructor AFFs jumps with some messed up flipping exits they stuck right with me.
I lost one AFF instructor on level 2. We had a good exit, but he left just a little before me for no specific reason other than timing issues. (He was not used to the smaller plane for AFFs and I had to relearn a new exit too.) I saw him on his back below me (we were nearly face to face and perpendicular with his legs near the other instructor) as he let go. AFTER he let go, I deacrched and I went unstable and flipped but resolved the problem on my own. He came up next to me and decided not to hold on until the pull, at which time he had his hand ready to grab if I went unstable." He said, you were stable and flying without me, you proved you could regain stability in the flip you did, why should I grab on and change that?"
So, I disagree that only real unstable exits cause instructors to let go or be thrown off. -
I walked by someone the other day who said to another jumper he had over 40 reserve rides. I kept walking, but thought - "please don't pack my ride."
This poll asks the question, how many times statistically have you fired your reserve - or if you are an employee of a DZ, what is your DZ average.
For the sake of the question, please assume malfunctions on modern (in production) gear that a typical fun/recreational jumper with average experience might use - not mals on highly loaded, super aggressive, competition or experimental equipment only the top tier of our community use.
NOTE - I TRIED TO EDIT THE POLL TO ADD >600- IT WON'T LET ME - SO VOTE 500-600 IF YOU ARE >600. -
Yippe. I put it in my Netflix cue - and it came today... IMAX is great - I wish I saw it in the theatre - however being able to slowmo and rewind on the DVD makes it fun to watch. Great DVD quality! -
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The problems are:
Give me solutions not problems. You are now entitled to give me the same look my coworkers give me. ;-)
I know this is a hard issue - but I also would pay a lot more to know I had a lot better safe training. I lost a friend in paraglidng - and what hurt me is that the loss was because of training.
AFF school - $2,500 - not killing yourself on landing - priceless. -
I could not agree more with Tom's points. I am new to skydiving with only 7 jumps, but I have a hundred or so paraglider landings. (For those who are unfamiliar with a paraglider – imagine a parachute that is designed to have a great glide slope so you can fly across country just using thermals for lift where you launch on a hill with the wing fully inflated. My paraglider had a surface area of 354 sqft or a wing loading of 0.5 lb per square foot. This means wind and thermals greatly affect your landings and flying.)
Both of my “ouch” landings on my paraglider were when I was a student with little flying experience. One was in a steep turn that could have killed me - just to avoid landing in an empty road when the wind and a thermal took me off my spot by a good margin (stayed up on final in a thermal)... I also landed into a fence once – same issue with the thermals, but I did not want to do a 90 degree turn 20’ off the ground. I will choose a PLF with 5 MPH forward movement (assuming a flare) into a fence any day over landing on my side at 30MPH in a steep turn. But, please don’t take my novice opinion as advice.
The concept of what is learned in stress works in stress is important. When learning my emergency procedures for skydiving - in the back of my mind thought, great - I can do it on the ground - but what happens when I get a fast spinner? I did it in the simulator hanging from the roof being pushed around, but I still did not feel 100% “muscle memory.” On my AFF4 - the instructor had me put on the mockup harness and show him a pull. Every previous instructor just watched me pull and described the malfunction to react to. He was behind me and grabbed me and started throwing me around the hangar after I pulled my main. I had to relearn the cutaway move while trying to keep my balance on my feet. I asked him to do it again. I think I might owe this instructor my life some day – it was the best thing that happened to me in the training – because I was caught off guard, whereas in the simulator I knew they would throw me around! I encourage all instructors to try to throw the most wicked curve balls at your students – as it really works to teach control in stressful situations.
How can one teach obstacle avoidance and low turns? Simulating it is hard. I know I am going to work with an expert at canopy control pretty early on – as I feel it is so far the weakest link in my training so far – where “never turn low” is taught with perfection but “there is a plane landing on the runway and you are blown that way due to a wind shift – now what do you do?” is not taught as well.
My two cent novice opinion is that there are way too many skydiving and paragliding fatalities that are due to the inability to train for the worst on landing. I just saw on TV “Impact: Story of Survival” where a very experienced skydiver with a video rig fought a line twist which came undone enough to cause a fast spin. He cut and his reserve had three twists on the reserve. He came out of the twists with a perfect canopy overhead – but then was heading straight for the trees with no room to spare – and 4 seconds latter he hit the ground in a hard turn causing serious injuries and near death. I realized I am ill prepared for obstacle avoidance in such a situation too. You could tell he had the “the worst is behind me” feeling and then realized where he was at and panicked.
I know obstacle avoidance was a low priority on the paragliding syllabus – stalls and other malfunctions were taught well, and even were practiced over bodies of water for extra margin – but most paragliding fatalities occur under a perfectly good canopy – canopies that are much bigger and much less aggressive than skydiving rigs. I have been told that more than half of all skydiving fatalities are under a perfectly good canopy too. That being said, I ask, wouldn’t it make sense that if half of skydiving deaths occur on landing with a good canopy, shouldn’t half the basic (AFF or similar) training be devoted to canopy work and worst case landing procedures, even if it means more time and/or training equipment? Again, the opinion of a novice, take it for what it is worth. -
I have never jumped w/out eyewear. But I have ridden my sportbike at 80MPH+ without.
I find it is easier to see without glasses than wearing bad sunglasses - as the airflow makes rotors behind the lenses.
I learned, should my glasses cause problems and I can't see the car in front of me, to rip them off and go without. But most of the time I wear a full face helmet on my motorcycle.
I don't know how well this translates to 120MPH freefall. Just my experience. -
Lucie813,
I am nearing the end of my AFF levels right now. If the weather would have been good today I would have been done... I am far from an expert at skydiving, however, I can say, don't let the AFF stuff scare you. Don't read all the requirements before signing up, because they are much more intimidating on paper than in real life.
I think I waited so long to get into skydiving because I thought, "I could never do THAT. Flips, you gotta be kidding."
I am finding that the AFF training is pretty easy, and you don't have to do it perfect either. For an example, I really overshot a 90 degree turn the first time I did it. I passed the level anyway - because I told the instructor I knew I overshot, so we just talked on the ground how to fix it next time. Now, if I had gone into a spin or something out of control, I would have failed.
About being afraid of heights... I myself cannot walk to the edge of a cliff and look down unless there is a railing. This is not a problem in skydiving because the reference points (ground, cliff walls, ground wind) are all so far away.
I found it real scary to enter the doorway on my first three jumps, because the instructors were holding on so tight it was clear they did not want me to do anything except exactly what they expected. My instructor at one point put his hand on my chest holding me back even though I was not even moving yet. This subliminally makes you have a fear of the door - like it is a dangerous place for you to go – it is scary. But on level 4, where I knew the instructor was going to let go and was not even holding on tight when I got into position - I got to the point of thinking - "What is the worst thing that could happen, I could fall out of the plane and I know how to fall and regain stability, and pull my own chute." At this point, entering the doorway becomes much less stressful and actually quite fun.
Regarding the PLF... I dreaded the training too, thinking I am too big of a clutz to do that. Ask my dog, he won't even rollerblade with me anymore. I nailed it my first try. I did it three more times because it was FUN not because the instructor told me to.
Here is what I would do... Take a tandem jump, a fun jump. Tell the instructor you think you will do AFF, but do the tandem just to get used to the smells of the plane and the sensation of freefalling. If the DZ has a Tandem/AFF program where the tandem is used in place of the first AFF jump, do that so you save the money.
Ask the DZ employees, like your tandem instructor, what AFF or AFF/Tandem offerings they have. I did a tandem a long time ago (1998) and went right into AFF this fall without another tandem. However, the second I left the plane - I remembered the exact sensations of freefall, and suddenly all the stress was over because I knew how everything else would feel and I was doing what we were trained to do. It is hard to believe you will be completely comfortable the first time freefalling with a chute on your back, but a good tandem experience does that.
Here is my only advice for AFF. Visualize the tasks on the ground - and visualize what to do if you don't nail it in real life. For an example, ask your instructor, "So you want me to turn 90 degrees one way, then 90 back to looking at you. If I go 180 one way, should I go 180 back so I can see you, or only go 90 and expect you to move?”
Nail it on the ground, visualize doing it, and you will be a-ok.
So, the point to the story – as long as you are mentally ready to take part in skydiving – the AFF will be simple. Don’t worry about the details – just go with the flow.
GO JUMP! -
- - > This is kind of a long essay… Read on optionally…
Today a police officer missed a rioter and shot someone with a beanbag killing her for no reason.
Yesterday two Japanese climbers were removed from a rock face dead after weather trapped them.
This week two people from Colorado died while doing a crew demo – something I had to explain to my family.
The day before my AFF1 - our office manager flew to New York to bury her sister-in-law, her sister-in-law's husband, and their 3-year-old son - taken out by a drunk driver with 5 prior accidents.
Two months ago I tried to convince an employee flying commercial airlines was safer than showing up to work. I promised him I would pay for the airfare if he found some place he wanted to go. He has not purchased the ticket yet.
Three months ago, I had to report to a customer’s office building to organize the clean up the bodily fluids of a call-center employee who got up to goto the bathroom and died walking to the restroom. He died instantly when all his blood came out of his ears in front of hundreds of co-workers. The ice in his big gulp was still cold when I threw it away.
A year before I watched my grandmother take her final breath at age 90 - suffering a painful natural cause death. I had never seen someone die before seeing each system shut down slowly.
Sometime the previous summer I saved my dog's life while walking to a birthday party when he ran out in front of a SUV on leash. He was milliseconds from guaranteed death without my input, and my reflexes saved his life.
A year before I became real good friends with someone who performs heart surgery. I can't believe he has been the final goodbye ("you will be going to sleep now") for many people who never make it and still wakes up in the morning to go to work.
A year before, a gentleman I learned to paraglide with died paragliding. He was the ideal student, conservative and well trained, a retired individual with a family and flying experience. This convinced me that even the “safe” flyers can meet the ground suddenly.
A year before, a good friend was hit by a drunk driver while riding his bike. I see his blue “in memory of” street sign daily while driving to work.
A year before, my best friend saved my life, as I turned upside down in a kayak and was stuck under water due to a clothing mishap locking me halfway in the kayak. I looked at the sand at the bottom of the lake inches away and thought, this is how I am going to die. I saw death and knew what the final moment might be like. Just then, he grabbed be and turned me over.
I am only a few weeks into skydiving - and the risks scare the shit out of me. I wonder if the Automobile Association of America (AAA) had a documentation of every car fatality on their website – how many people would never get in a car?
If someone asks me - would I rather die young experiencing life or die old wishing I did more - I try real hard to tell the truth, but the fact is I don't know what the truth is. I think this is a lose-lose proposition.
I try to reassure myself that I know when to walk away, and thus I am less likely to kill myself skydiving or riding my motorcycle… But then there was that time I saw a car hydroplane in the rain 2 feet in front of my motorcycle and slide 200’ off the highway. Why in the *&^% was I riding in the rain? I did not know I should have walked away, and consider myself lucky to be here. Oh, by the way, I was riding home from a bungee jump and had the adrenaline pumping – which proved that adrenaline clouds judgment.
When learning to paraglide - my instructor would not give a student a passing grade to P2 unless he saw the student make the decision to walk down instead of fly the mountain when other people were still flying. I walked down a few times…
I am 29 years old now, and beside for coming to terms with the risk of skydiving, I am having to come to terms with the risk of life. Death is something that takes a lifetime to understand. (Yes, that previous sentence is a cheap play on words.)
So, my question back to you all, have you accepted the risks in life, not just skydiving? If the answer is yes, I don't believe you. I don't know anyone comfortable with the fact accidental death could occur one second from now. Boom, you are now dead. Are you ok with that? Whatever you are doing right now, someone has died doing it. Whatever you are doing in 8762 seconds from now, someone has died doing it.
But, I am already realizing the power of skydiving. Not taking into consideration the automatic activation devices, every time you leave a plane your life expectancy is turned into seconds. You have to save your life every time. This is experience millions of people will never understand or comprehend. It is an amazing power.
I think a lot of adventurous people are more prepared for death than the average population. Or are they in denial?
On a final note - the shark keeper at the London Aquarium told our group last year - more people were killed by beverage vending machines in 2003 than by shark attacks, but my heart rate never rises around a Coke machine, but I am scared shitless of sharks. -
So, I am new to Skydiving (hi everyone) – but have some good experience flying a paraglider. (In case you are not familiar with a paraglider, imagine a much more rectangular and larger skydiving canopy that you launch fully inflated by running off a hillside – with the point to catch thermals and stay up for a long time.)
I found there is a piece of gear used in skydiving that is exactly the same as in paragliding – the release pin (either curved or straight)… But, in paragliding it is used on the release of a tow rig assembly – in conjunction with a three ring disconnect mechanism. (Just like one of the main canopy connection points on a skydiving rig put on the end of a rope.)
So what is a tow in paragliding – it replaces the mountain - you can launch by running on flat ground while a winch with 3 or 4 thousand feet of rope pulls you up – looking just like a parasail behind a boat – where you pull the “rip cord” at altitude to fly off into the wild blue yonder free of the tow. (By the way, it is real hard to keep the wing flying straight behind the tow when crosswind occurs, going off 30 or so degrees is never recoverable and requires an abort – unlike parasailing in Mexico which can be done drunk.)
Ok – so here is the safety part. I did not assemble the three rings on the tow, but the person who did accidentally pushed the release pin way too far so that the rope loop was not around the pin, but past the hole on the pin and around the webbing sowed to the pin. As soon as a bit of tension was applied to the three rings, there was no way on earth that the pin could have been released. Once flying, it was upside down and under tension so I could not see the pin.
See the drawing attached (ok, so I pushed the limits of Microsoft Paint to make the drawing – please don’t critique the drawing.)
As soon as I saw a skydive rig and saw the “infamous pin” on the main and reserve, I inspected to make sure that the pin could not be pushed in past the hole at the end of the pin. On the rigs I have been using, it is indeed impossible… But, riggers and those who repair or make gear – be sure there is no way to push in the release pin so the loop is on the wrong side of the hole on the pin!
--- End Skydiving Observation
Ok – so those who want to know how the paragliding incident finished… I pulled and pulled – and nothing happened. I was 300’ AGL (bad tow, no lift and limited headwind) heading 14 MPH towards the tow equipment in the back of a pickup truck with the operator blinded by the sun unable to see my struggles. The tow operator watched me pass him connected with about 20 feet of slack in the towline yelling “pull, pull”. **duh** Now, the proper procedure is to cut the towline (I should have had a knife too) but the operator had to run around to the other side of the pickup truck as to grab the line since I overflew the truck. He was not quick enough as far as I was concerned, so I initiated unplanned and untrained for procedures.
I immediately envisioned my wing flying forward reaching the end of the line, and turning forward motion into a downward dive --- perhaps a stall, perhaps an asymmetric deflation throwing me into a turn??? A shallow turn would have put me with the wind and I did not have the radius – plus I heard my verio beeping indicating I was going up. I needed down without putting tension on the tow line.
Now I don’t really know all the difference in characteristics between skydiving canopies and paragliding wings yet since I have only a few jumps, but I have been told a spiral dive close to the ground has the same general consequences in skydiving as it does in paragliding… Well, I initiated a spiral dive from 300’ towards the pickup truck, at one point reaching the end of the rope. Against all odds, I landed it with a flare, directly under the wing, on my feet between the truck and 20’ tall haystack with the tow line wrapped in the hay stack.
The tow rig should have been grounded until it was made failsafe – but instead I opted to leave after I was told, “just don’t push the pin in that far.”
Travis -
Ya, I saw on a show that Troy and the IMAX guy for Wild California would go up in a helicopter and wait until the control tower gave them airspace between jumbo commercial airliners - as and when the space became available.
Thanks all for the wonderful suggestions. I am planning my 2005, and I wanted to have a wish list of where to go. I travel a lot for work, so perhaps I can get to a few places a day or two early to get in some fun too.
My ears are still open for more suggestions.
T -
I remember watching the sky surfing sequences by Troy Hartman in the IMAX Adventures in Wild California movie. I thought - I have to do that - not the sky surfing, but skydive in the most beautiful oceanfront area looking at white sand and blue ocean.
I see a company in Cancun that is rated by experienced skydivers as a "tandem factory” and experienced jumpers highly recommend experienced jumpers stay away.
So, my question then is - what are the most beautiful drop zones out there - the ones where you have to try real hard not to lose altitude awareness because of the view, the ones worthy of movies (I.E. you don’t land in field between the runway and hangar)? For the sake of discussion, lets assume DZ that are full time operations and actively solicit solo jumpers.
T
Thermals
in Safety and Training
I looked it up to make sure I remembered correctly. Here is a link. (5.5 F per 1000 FEET or 9.8C per 1 KM)
http://www.campusprogram.com/reference/en/wikipedia/d/dr/dry_adiabatic_lapse_rate.html
I know nothing of fluid dynamics, but I am guessing that the types of slipstreams can be different depending on many factors.
I think the bus analogy works great for a thermal a few hundred feet off the ground since the bus and thermal are both moving in open space. But, it does not illustrate a thermal close to the ground in my opinion. Imagine a bus parked against a wall (the ground) and taking off with incredible acceleration. For the first moment, nearest the wall, the bus leaves a negative pressure pocket where the bus was parked. Air HAS to fill this void, so you HAVE to get a sideways or downward movement. If the thermal had 200,000 cubic feet of displacement, 200,000 cubic feet of air has to fill the void. How it gets there is anyone's guess - but I don't want to be flying when it happens. ;-)
I am thinking you might have illustrated a good point – thermals might have more intense wind effects close to the ground where they originate. Anyone have a real large smoke machine so we can fill a DZ with smoke and watch the thermals?