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franck102

Web-based separation charts

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I was following a thread on separation in another forum, and was wondering how useful a web page that displays a chart of ground separation based on the wind forecast for the day woud be?

Roughly, the idea would be:

- manifest in the morning browses to the web page, and enters the location of the DZ, the IAS of their plane on jump run, and the direction & altitude of the jump run

- In the backend I get the wind forecast from http://www.arl.noaa.gov/ready/cmet.html, and I use it to produce a chart that shows how long you need to wait to achieve x feet of separation on jumprun.

- Manifest prints the chart & posts it

Would this be useful? If so, here are a few questions:

- How do you actually use the wind forecast on http://www.arl.noaa.gov/ready/cmet.html?? There are about 20 "windgrams" to choose from, and the altitudes are given in mb - how do you convert this to altitude?

- Should there be an option for manifest to enter their own wind forecast?

- What exactly should the output be - I was thinking of:

a) wind forecast if it was automatically retrieved
b) time to wait to get 100 feet of separation (or 2 columns for 500 & 1000 feet?)

Let me know what you think...

Franck

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How do you actually use the wind forecast on http://www.arl.noaa.gov/ready/cmet.html?? There are about 20 "windgrams"


AVN short range is probably what you want
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the altitudes are given in mb - how do you convert this to altitude?


z = 23000 * log(P0/Pz)
z = altitude in feet
P0 = Pressure at sea level in millibars (1013 if no actual value)
Pz = Pressure at altitude z in millibars

1 millibar = 0.02953 inches of mercury (you'll need it to convert the pressure at sea level).
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Should there be an option for manifest to enter their own wind forecast?


yes. The jumprun as well.
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What exactly should the output be


In addition to the time for 100ft, 500ft and 1000ft, there should be the optimal jumprun with the begining and the end. Of course, this has to take into account the winds from opening altitude to the ground.

Once you have all of this, you could turn it into a simulator (or ask John Kallend if you can use this to improve his excellent simulator).

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Let me know what you think...


A bit nerdy but it's a pretty cool idea. Not sure if it would be of any practical use at the DZ, but probably a very useful tool to explain spotting and exit separation with realistic data.

bb
--
Come
Skydive Asia

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Something like this would be nice at the DZ's that have a computer, but lots of DZ's dont.

I think a better thing would be to create this as a trainer to teach people how to make their own determination of exits and exit count.
Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

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We have a big picture of the dz near manifest, and one of our pilots usually calls and gets the winds aloft through the day. They'll write it on that picture (with a grease pen) with arrows showing direction, and noting the speed. It might be a good idea to print off a wind speed/seperation time needed chart and put next to it.

You may need multiple columns for different aircraft the DZ flies, but I'm not sure about the different distances - I'd say just put a note on there that it's for x feet of seperation at opening, which is good for a y-way formation - adjust accordingly. Hopefully most people know you need to give more time after a 18-way than you do a 2-way.
it's like incest - you're substituting convenience for quality

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http://aviationweather.gov/fdwinds

This is what you want to look at for winds aloft. It is given in MSL not millibars. Find a wind reporting station near you. Make sure you look at the effective time. It will be in "Zulu" time. Convert this to local time. If you need help doing that, ask your pilot what correction to apply. Before you make any decisions on what the jumprun should be talk it over with your pilot so you are on the same page. There might be something in this that you are not accounting for (like crosswind jumprun).
Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

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DATA BASED ON 221200Z
VALID 221800Z FOR USE 1700-2100Z. TEMPS NEG ABV 24000

FT 3000 6000 9000 12000 18000 24000 30000 34000 39000
BRL 3611 3623-05 3529-07 3555-07 3563-19 3579-29 349142 349849 348756
DBQ 3609 3620-05 3523-08 3648-08 3559-20 3579-29 349343 349849 348555
FWA 3424 3626-09 3622-11 3523-16 3322-28 3536-39 357641 355742 323643
JOT 3415 3622-08 3628-10 3535-14 3679-22 8602-31 851543 851049 358250
MKG 3521 3624-09 3624-11 3526-16 3536-28 3686-34 861443 359248 355547

Take this for example. I pulled it up for the Chicago area. It is valid on the 22 of the month at 1800Z. That is 12:00 Local. (The correction for Central Standard Time is GMT (zulu time) minus 6 hours.) It is for use at 11:00 am local to 3:00 pm local. Then I look at JOT for Joliet, IL. Across the top of the report are the altitudes of reporting. 3,000 6,000 etc.

You would read the line JOT as 3,000 winds from 340 at 15 knots. 6,000 feet 360 at 22 knots temperature minus 8 degrees centigrade. 9,000 feet 360 at 28 knots temp. minus 10. 12,000 350 at 35 knots temp. minus 14. ETC.....

Does that help?
Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

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Thanks Chris, that's exactly what is needed!

Franck



Now, as for a standard printout I actually don't think you could put in enough variables into it to cover all possibilities. I think communication with basic education is what you need to get proper seperation. A chart may not keep up with flock dives and birdman suits, etc.....see what I mean?
Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

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Something like this would be nice at the DZ's that have a computer, but lots of DZ's dont.

I think a better thing would be to create this as a trainer to teach people how to make their own determination of exits and exit count.



Well, actually my goal isn't to create a tool that can compute the ideal separation to the millisecond for all possible cases - I think this would have limited use.

Instead the goal would be to get as many jumpers at as many DZs as possible start using this count as their primary means of determining the appropriate separation. In my 20 jumps since AFF 2 different jumpers have explained to me how I should look at the angle of the previous group to decide when to go. I'm sure most experienced spotters & JMs know better, but they often get busy once the jumprun has started and each group decides for themselves when to go.

My hope was that if we can make it easy enough to use for manifest and they start posting it every morning the service could contribute to promote safer practices.

Franck

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Thanks Chris, that's exactly what is needed!

Franck



Now, as for a standard printout I actually don't think you could put in enough variables into it to cover all possibilities.



The chart would be customized

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I think communication with basic education is what you need to get proper seperation.



Absolutely, though in practice it seems many misconceptions about separation exist even among experienced jumpers. If bottom separation / time are posted along with the winds at a DZ, students will ask about it and trigger some discussions.

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A chart may not keep up with flock dives and birdman suits, etc.....see what I mean?



If we just give the bottom separation as a function of time clearly jumpers are still responsible for deciding how much separation to seek. That's why I was thinking having only one column, either # of seconds to get 100 feet or # of feets per second, this way the chart isn't suggesting any specific separation.

Franck

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