how do you track away in a 3+ way without compromising horizontal separation with another group?

[Newbie 0]

im sure this has been discussed before so if anyone can provide links to older posts that would be helpful rather than repeat answers here - all i could find was posts on exit separation, not tracking and group separation.

Anyhoo, what i was wondering, now that im coming up to do 3 and 4 way RW dives, is how to do track to provide necessary horizontal separation between the other jumpers in your group (i think Kallend said that it needs to be 150ft from the centre of the group until opening to be safe) without going "under" another group or jumper on the same load that has exited after your group? As far as i've learnt so far, you track 180 degrees from the centre of the formation which is fine for a 2 way, but what about 3+ ways? In a 4 way, if everyone tracks from centre at 90 degrees from each other, then 2 of the jumpers will be tracking along the jump run right? Does it not happen like this (see below)? Does everyone in a 4 way track at 45 degrees off the jump run line?


If 1-4 represents each jumper in a 4 way (ignore the asterisks):

*1*
2*3
*4*



Do you all track like this, where x represents the centre of the group that everyone is tracking from and 1-4 is the jumpers who have tracked away from centre, and the dashed line is the jump run (couldn't get it exactly straight but you get the idea):

*1********|*******2*
**********|*********
**********|*********
**********|*********
**********X*********
**********|*********
**********|*********
**********|*********
*3********|*******4*



How does it work in a 3 way too? What "angles" should everyone be heading off at? Is this something that should be decided on the ground?

Thanks all

"Skydiving is a door"
Happythoughts

[kallend 2,028]

You avoid other groups by having adequate separation from them on exit. Adequate separation depends on group size, winds aloft, jump plane speed, and what style of flying you and the others are doing.

www.iit.edu/~kallend/skydive/ for details.

...

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

[riggerrob 643]

The best way to achieve separation from other groups is to wait a few seconds after they exit (varies with aircraft speed).
The second method is to track 90 degrees to jumprun.
The third method involves using your eyeballs.
There is no single guarranteed method. You have to skydive with your eyes open.

[billvon 3,008]

>Does everyone in a 4 way track at 45 degrees off the jump run line?

No; they track away from the center of the formation to get clear air. Once you are doing 4 ways, you no longer take jumprun into consideration, since you are more at risk to collide with someone in your own group than another group exiting before/after you.

To ensure enough separation from them, leave enough time between groups. One way to do this is to watch your progress over the ground and wait until you've covered 1000 feet before exiting (or 700 feet then climb out.) If you can't estimate distances like that, then use time. The time depends on the speed of the aircraft and the upper winds, but the minimum time is around 5 seconds between groups - that's in a king air with no uppers. Add time if there's a headwind on jump run or if the aircraft is slower.

[dreamsville 0]

Besides separation between groups as the first precaution, as you watch other jumpers track in your formation you may find that you may be able to put a slight arc in your track that has you going closer to a line directly across jump run. You should only do this if you find you have developed significant separation between those to your sides, but because of the size of the formation and available altitude need to track a bit more. It's not often that I do this, but it's another way to try to avoid the other group.

Obviously, if there's not enough room on either side of you, you have to keep going on the path that safely bisects the tracks of those around you. If you are slightly de-arched, toes pointed, you will have a bit more speed to track further. Keep in mind that on a 3 or 4 way, it can be unsafe to keep tracking a long way (maybe towards another group) if it's clearly not warranted.
|

I don't drink during the day, so I don't know what it is about this airline. I keep falling out the door of the plane.

Harry, FB #4143

[TEB6363 0]

Yep, what these guys said.... In simple terms turn 180 degrees from the "Center Point" of the formation and track.

Please remember if the group is not quite together, still turn from what the group was trying to use as the center point as reference... You don't want to do a nice 180 and then realize you are flying parallel with someone else in the group...

Blue Skies

Once the plane takes off, you're gonna have to land - Might as well jump out!!

[quade 4]

Quote

The time depends on the speed of the aircraft and the upper winds, but the minimum time is around 5 seconds between groups - that's in a king air with no uppers. Add time if there's a headwind on jump run or if the aircraft is slower.

Bill --

Not like I need to show YOU this, but it may be of interest to some other folks who don't quite have this entire concept down yet.

I made a little and very simple spreadsheet that you can enter in jumprun airspeed and separation distance and it spits out numbers showing the time required between exits.

It's already filled in for 90 knots on jumprun and 1000 feet of separation between group centers. This should be "just about right" for most twin otter operations.

There's even a nice little graph I made on the second sheet that might be a bit easier for some folks to grasp.

quade -
The World's Most Boring Skydiver

Exit Separation.xls

[RichM 0]

I'd like to add to everyones good comments that I'm impressed that with 52 jumps according to your profile you are thinking of this. Well done.

Rich M

[nightjumps 1]

Paul,

Thanks for the .xls. Very nice tool.

[skr 1]

>all i could find was posts on exit separation,
>not tracking and group separation.

They are related topics.

If you start at the bottom end with how much
separation you want from other jumpers while
opening and work backwards to exit separation

- how much separation from people in your group
and from people in the adjacent groups

- how far do you need to track

- how far do the canopies of one group fly while
the next group is still in freefall

you get an estimate of how much exit separation
you need on top to accomplish this.

When I first ran into this question I thought it was
about 1000 ft, but that was based on round canopy
intuition. Squares cover a lot of ground, so now I think
small groups, 3-5, need more like 1500 ft, and groups
of 8 or 10 need more like 2000 ft.


Some people say you can't tell when you've covered
1500 ft across the ground, but I've taught many people
to do it.

Lots of people have put effort into figuring this out.
I collected some writings and put them up at the bottom of
http://indra.net/~bdaniels/ftw/


We started doing more than one group per pass in the 70's
so all this should have been worked out about 25 years ago.

But it wasn't.

Skr

[Newbie 0]

Quote

Some people say you can't tell when you've covered
1500 ft across the ground, but I've taught many people
to do it.

Hi, thanks for the link, i haven't looked through it but i intend to read it later today, but it looks very comprehensive.
I did have a quick skim through though - i see you are from the same school of thought as Billvon which is to look at the ground as an indicator to measure 1000, 1500 or 2000ft of separation.
However, how is this possible when you are:
a) at a new dz where you are unfamiliar with run in's and objects on the ground at run in with which to use as markers to measure distance on the ground
b) not allowed near the door when the preceeding group exit to look down and spot exactly what you are flying over to measure the distance from that spot to your 1000/1500/2000 ft marker point?
At the dz's i have jumped at here in the UK, if i even try and get close to the door when the preceeding group exit, the jumpmaster will put a hand up indicating for me not to move - i guess they are worried that i am going to jump before giving the previous group enough separation.
In this situation i guess i have to rely on the JM's expertise, but i'd rather not do that to be honest, especially when i asked one of them what they do to judge separation and he told me to watch for the 45 degree angle thing, which as kallend has pointed out, is not a valid indicator of separation.

Anyway i've diverged somewhat from the original point, but i hope you could give me some advice to address points a and b above.

Thanks again

"Skydiving is a door"
Happythoughts

[kallend 2,028]

Quote

i guess i have to rely on the JM's expertise, but i'd rather not do that to be honest, especially when i asked one of them what they do to judge separation and he told me to watch for the 45 degree angle thing, which as kallend has pointed out, is not a valid indicator of separation.

Anyway i've diverged somewhat from the original point, but i hope you could give me some advice to address points a and b above.

Thanks again

You can check for yourself and teach your JM something at the same time: take a look at any exit photo of a big way (such as the recent 120-way on www.tonyhathaway.com) and you can see a stream of jumpers falling away from the aircraft. Get a protractor and see if a 45 degree angle tells you anything about how far they are from the plane..

...

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

[billvon 3,008]

>how is this possible when you are:
>a) at a new dz where you are unfamiliar with run in's and objects on the ground

It is difficult; at places like that, it might be better to ask someone experienced how much time to wait until you're up to speed on exit separation there.

>b)not allowed near the door when the preceeding group exit to look
> down and spot exactly what you are flying over to measure the
> distance from that spot to your 1000/1500/2000 ft marker point?

Keep in mind you don't have to be looking out the door all the time for this to work. If you look out a side window and can see almost straight down, you can do the same thing. If, on jumprun, it takes 10 seconds to cover 1500 feet, then if you wait 10 seconds in the door you'll get 1500 feet separation. (You still have to look out the door to check for traffic of course.)

Most spotters do something very similar. They'll notice that the plane seems to be going really slowly, and they'll realize the uppers are high - and will leave more time between groups. Different rationale but same result.