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JohnnyMarko

Viso II - Freefall Speed

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So I got a Viso II and I love it. After my last jump, I replayed the jump and it gave me a freefall speed of 133MPH (I have it set to SAS, not TAS). I'm 6', ~195 exit weight, belly flying...that seems really fast...could I have reached that speed or are some digital readings somewhat inaccurate? Thanks

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That's really not that fast for 11 jumps. If you were flying solo, you didn't have a frame of reference by falling with someone, a simple move of your pelvic region down, a suit not made for you, perhaps knees a little down, a little head high, even the type of turns you might have been making... all variables that can contribute to a little extra speed. In time and the more dives you make with others, the more you will learn to adjust your fall rate. For now, just continue on the path of progression with your Instructors and the TLO's on the A card. If you have 11 jumps, then you've only got roughly 13 minutes of flying knowledge. Give it some time.

Enjoy.
Nobody has time to listen; because they're desperately chasing the need of being heard.

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So I got a Viso II and I love it. After my last jump, I replayed the jump and it gave me a freefall speed of 133MPH (I have it set to SAS, not TAS). I'm 6', ~195 exit weight, belly flying...that seems really fast...could I have reached that speed or are some digital readings somewhat inaccurate? Thanks



Turn it to TAS first of all, SAS has some bizarre adjustments that no one knows what they are it's a pretty useless measure. Second at your weight in a "big AFF arch" you could be going that fast.
"We've been looking for the enemy for some time now. We've finally found him. We're surrounded. That simplifies things." CP

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Turn it to TAS first of all, SAS has some bizarre adjustments that no one knows what they are it's a pretty useless measure.



I think SAS is a great thing as it makes speeds at different altitudes comparable.

So if you are at terminal and staying perfectly still, it won't show you doing 130 at 12k, 120 at 8k, 115 at 4k and so on -- it'll just show you the equivalent for 3000'. It'll show pretty much one constant speed, because it is trying to adjust for air density variation with altitude, and thus variation in true air speed.

Now, it is true that L&B don't say anything about the exact density altitude correction applied. But for our purposes the usual standard atmosphere tables will be sufficient to take out most of the speed variation with altitude. We know that the L&B gadget can't take all factors into account -- ground height above sea level, temperature variation, pressure variation from the standard, etc. But it is a very useful thing that it does.

I bet other devices must have something similar.

The actual speed variations on a jump are messy enough without having to deal with a 20% variation in terminal velocity through every jump, if one is looking at the data (or graphs on the computer for a Protrack).

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True, but you can also hose up your speed by playing with the temperature adjustment. I don't know if the Viso has a temp adjustment like jumptrack does. But just by playing with that temperature your speed goes up and down.

Since I've never gotten out a thermometer at 3000 feet to measure the air temperature each day I jump, I just keep mine set to TAS. :ph34r:

Plus TAS corresponds to everyone else's speed readings (Neptune, etc).

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But just by playing with that temperature your speed goes up and down.



Still, temperature differences in the airmass relative to the international standard atmosphere will change the readings -- whether it is SAS or TAS. So there's no advantage either way.

I still prefer normalized data to better evaluate fall rates. While you prefer using TAS to compare to other devices that don't adjust for altitude.

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