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diverds

Exit Separation for Pilots

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After reading Bill Von Novak's article on exit separation and speaking with him on the phone, it is my understanding that 1000 feet of separation across the ground is adequate for average sized groups. The following chart shows the amount of time necessary to achieve that 1000 feet of separation for a given ground speed. I've attached it as a word doc as well.


To Achieve 1000 of Horizontal Separation

Ground Speed in Knots/Seconds Between Groups

120/5
115/6
110/6
105/6
100/6
95/7
90/7
85/7
80/8
75/8
70/9
65/10
60/10
55/11
50/12
45/14
40/15
35/17
30/20
25/24
20/30

For the last several months I have been making a jump run announcement that includes the current ground speed and the necessary time between groups. The jumpers seem to appreciate it so I thought I would share it with other jump pilots out there. I will cross post this on www.diverdriver.com as well.

-Dave


Skydive Radio

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Nice work Dave.

I wrote a feature for The Ranch S&TA site a few years ago that covered the same ground. It begins with a discussion about how we figure the time between groups, and then lists ground speed at various upper wind speeds. Finally it computes the required time between groups to allow 500 feet, 1,000 feet, and 1,500 feet of separation. We began with 500 feet as the minimum because that's what our pilots and drop zone management thought was appropriate given the costs of running the airplanes. I agree that 1,000 feet is a better starting point.

The final chart was printed out and posted at manifest along with winds aloft for the day. That way jumpers could figure out the required seperation when they manifested.

The article is #15 called "Waiting Between Groups" available at: http://theblueskyranch.com/STA.php
Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

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I have been posting and advocating the use of this method on the forums as far back as 2003. The attached excel sheet in this POST can be printed out,laminated and taped next to the door of the aircraft and or in the cockpit. I know of at least 1 DZ that has been using it for many years successfully.

Direct link to the Excel sheet HERE
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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Good chart. I would add that that chart is valid for zero winds at opening altitude, and conservative under normal conditions (i.e. when winds at opening altitude are the same direction as winds on jump run, which is most of the time.) In other words, under normal conditions you will get either the listed separation or greater separation.

The only gotcha is when the winds at opening altitude are opposite. This happens here during Santa Ana conditions, but fortunately is rare.

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When I first read the tread title, I thought, "if the the pilot is exiting the plane, I'm not waiting for exit separation.":o:ph34r:



If the pilot is exiting the plane I want to be dam'n sure I've already exited!
The only naturals in this sport shit thru feathers...

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Good chart. I would add that that chart is valid for zero winds at opening altitude, and conservative under normal conditions (i.e. when winds at opening altitude are the same direction as winds on jump run, which is most of the time.) In other words, under normal conditions you will get either the listed separation or greater separation.

The only gotcha is when the winds at opening altitude are opposite. This happens here during Santa Ana conditions, but fortunately is rare.



Opposing uppers & lowers are not all that rare in some places. In southeast Texas, it is quite common in the winter months to have very strong uppers from the northwest, regardless of the direction or speed of the ground winds.
Chuck Akers
D-10855
Houston, TX

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We've been using that chart at Skydive Orange taped next to the Otter door for a number of years and it has worked quite well. All the pilot has to do is yell back the ground speed on jumprun and let the spotter determine the separation.

Thanks for the chart, we love it.

- Dan G

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Good chart. I would add that that chart is valid for zero winds at opening altitude, and conservative under normal conditions (i.e. when winds at opening altitude are the same direction as winds on jump run, which is most of the time.) In other words, under normal conditions you will get either the listed separation or greater separation.

The only gotcha is when the winds at opening altitude are opposite. This happens here during Santa Ana conditions, but fortunately is rare.



Opposing uppers & lowers are not all that rare in some places. In southeast Texas, it is quite common in the winter months to have very strong uppers from the northwest, regardless of the direction or speed of the ground winds.



Near the Great Lakes the surface winds are often dictated by the lakes but the winds aloft are following the usual westerly flow. Mountains can produce wind anomalies too.
...

The only sure way to survive a canopy collision is not to have one.

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We've been using that chart at Skydive Orange taped next to the Otter door for a number of years and it has worked quite well



Orange is where I first saw it implemented consistently with good results when it was my home DZ. I cannot claim that the chart is my idea as I believe it was Lambert who passed the Excel chart on to me when I asked him about it. It's definitely been an Orange thing for as long as I can remember.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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I really appreciate this thread. I have just started my self-supervised phase and my last jump was a bit confusing for a rookie. I was a lone solo going between a group of RWs and a group of tandums. One of the camera guys finally gave me a little direction. Having this information in my head helps me understand what I was being told. Thanks
POPS #10623; SOS #1672

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Orly King started asking for ground speed readings from me in 1998. It developed into the exit seperation table we used at Skydive Chicago for many years. I am very glad to see that this is being posted by exit doors so everyone knows what to expect. Knowlege is power.
Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

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I am very glad to see that this is being posted by exit doors so everyone knows what to expect



Unfortunately, it's not as wide spread as one would think it would be since all it requires is simply taping the chart by the door and asking the pilot the GS.[:/] I've taped several by doors of A/C only to come back later and see it has been removed.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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TAS is not really the issue when talking about exit separation. Distance traveled across the ground is what you need to be concerned with and of course that varies greatly depending on the upper winds.

In the Otter on a no wind day you are looking at a ground speed of somewhere around 90 knots. Can't speak first hand for other aircraft but would expect most of the normal skydiving fleet to fall somewhere in that same range with the exception of the Casa and King Air which would be a bit faster.

And before someone says it...yes the DC-9 would be faster as well :P

-Dave


Skydive Radio

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TAS is not really the issue when talking about exit separation. Distance traveled across the ground is what you need to be concerned with and of course that varies greatly depending on the upper winds.



Agreed, distance traveled across the ground is what you need. However, in order to calculate that distance you need to know what the TAS is and what the winds are. Reminder: GS=TAS +/- winds.
Without the TAS you have no idea what the GS is, and hence what the distance traveled across the ground is.

What you are telling me is that an Otter on jump run has a TAS of about 90 kts. That's the info I'm looking for, but for more jump A/C.

"Let the misinterpretation and attacks begin."

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Okay, I understand what you're asking now. Just keep in mind that doing the math yourself based on a forecast winds aloft will not be nearly as accurate as just asking the pilot for a ground speed. Winds aloft forecasts are just that...forecasts. They are not actual. GPS ground speed is the real deal and will be much more accurate for you.

-Dave


Skydive Radio

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TAS is not really the issue when talking about exit separation. Distance traveled across the ground is what you need to be concerned with and of course that varies greatly depending on the upper winds.




-Dave



Well, what you REALLY need to be concerned with is distance traveled relative to the air at opening altitude, but distance over the ground is usually a good surrogate.
...

The only sure way to survive a canopy collision is not to have one.

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