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Frank57

Turbulence over Asphalt

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I've never seen any discussion about how the air behaves over hot asphalt. It's seems to lift me up at one point only to drop me at another. I think the middle has hot air rising, but the edges seem to have falling air. My canopy and I just fall.
I know it's best to avoid the relatively hot asphalt and land in the cool grass or dirt, but what is the best way to handle unavoidable black top landings?

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Well the hot rising air has to come from somewhere. So yes there should be some air moving down to a small degree but the dropping effect has to do with your air speed. When you come out of that rising air your canopy may make a dive to netural out its designed flight path. Im sure someone on here can explain much better than me.

As for landing on asphalt, my only suggestion is to wear shoes and remember that you probably wont slide like you will on grass. The second your feet touch the ground they are just gonna stick.

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Think about it. As the air is heated and rises it gets replaced with cooler air coming from the grass areas on the perimeter of the asphalt.This causes the air above the grass to desend down to replace the air that's moving over to the asphalt causing a down draft. So it's not a loss of lift but actually being in a column of desending air.
Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

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I always try to err on the short side versus over-shooting... that way you will have least got a good look at where you're going to land (if you fly a normal pattern) instead of floating over obstacles that you didn't expect to encounter.

Personally I avoid asphalt at dropzones since that's generally where the cars and the planes are. :P

Air can do unexpected things so always be ready (plus it's invisible). Never stop flying your wing until you are safely landed and all momentum has been arrested. You can encounter gusts, rotors, turbulence, etc over grass as well so I wouldn't focus too much on the landing surface as much as simply flying your canopy safely.

NSCR-2376, SCR-15080

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Frank57

I've never seen any discussion about how the air behaves over hot asphalt. It's seems to lift me up at one point only to drop me at another. I think the middle has hot air rising, but the edges seem to have falling air. My canopy and I just fall.
I know it's best to avoid the relatively hot asphalt and land in the cool grass or dirt, but what is the best way to handle unavoidable black top landings?


http://blog.skytrekker.net/2010/12/turbulence.html
"A thermal column (or thermal) is a column of rising air. Thermals are created by the uneven heating of the Earth's surface from solar radiation. The Sun warms the ground, which in turn warms the air directly above it. The sun warms different surfaces more than others - asphalt, concrete, grass, and water - all heat differently. The warmer air expands, becoming less dense (lighter) than the surrounding air mass. The mass of lighter air rises, and as it does, it cools due to its expansion at lower, high-altitude pressures. It stops rising when it has cooled to the same temperature as the surrounding air. Associated with a thermal is a downward flow surrounding the thermal column. The downward moving exterior is caused by colder air being displaced at the top of the thermal."

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Frank57


I know it's best to avoid the relatively hot asphalt and land in the cool grass or dirt, but what is the best way to handle unavoidable black top landings?



Unless you're doing a demo into a stadium or the roof of a shopping mall dressed as Santa. And have to land in the parking lot for some reason.

Landing on asphalt should be completely avoidable in all other jumping situations. Know the spot and the uppers use them to your advantage to land where you want. Don't fly over anything you don't want to land on. And if for some reason your head toward a road and think you'll land on it, land cross wind in the grass on the side of the road if needed.

If you don't know how to land cross wind, ask your instructors and/ or take a canopy control course.

Fly your canopy, don't let your canopy fly you.
diamonds are a dawgs best friend

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The dropzone where I was landing is about 300 x 300 of dirt and peas, with asphalt on all sides. I had not noticed the addition of more pavement, under my final approach side. I will not be jumping there again, until I am a much more proficient canopy pilot. As for the AFF students who begin there, a little special training should be in order. What do you think it might include?

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Accurate analysis.

That reminds me of how I placed fourth in a accuracy competition ahead of guys with thousands more jumps than me.
Light local winds were blowing across the bowl, then across an asphalt runway. I noticed everyone getting bounced about by turbulence/lift over the asphalt runway, so I flew a crabbed approach. I stayed on the bowl side of the asphalt runway, gently crabbing in sideways, I only did my last 40 degree turn at 100 feet above the ground. All my landings were in the pea gravel bowl.
Hint: I flew the last 500 feet of descent in 1/2 to 3/4 brakes. Back then I jumped a 230 square foot Strato-Cloud.

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