Exit Separation - Real World Thoughts

[GrumpySmurf 0]

"Power Point"
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"The tool of liars and cheaters worldwide - betterly known as the 'Sales and Marketing Department' - when you have nothing useful to say, or want to hide the truth in lots of pretty pictures - use Power Point(tm). Ask for it by name."
Sorry, a Dilbert-esque moment.

[AndyMan 7]

I saw john's presentation last year. Freefall drift is one area where the more I know, the more I get confused.
_Am
ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
Yahoo IM: ametcalf_1999

[kallend 1,640]

<<confused.>>>
I've re-done the section that caused most confusion, with more animations.
PS I'm not selling anything, the only reason I use Powerpoint is that it's the easiest way I know to make a slide show. A picture is worth 1000 words (at least).

[quade 3]

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A picture is worth 1000 words (at least).

Or 10 bucks if you send it to Parachutist.
quade
http://futurecam.com

[SAMPLEKSample 0]

I think you brought up some major safety points....myself being a low time jumper with just over 100 jumps, I am nervous about these things...organization and rules should be established.
But, upper winds change throughout one day...ask the pilot yourself what the winds are doing and in what direction...pass it around, this will help give an estimated time in seconds, but seconds should not determine the group seperation. If there is miscommunication of upper winds, even if not, you should be looking all the wayout of the plane to check your spot and watching the group ahead of you until they are at a 90 degree angle. If they are pulling higher you give them some extra time, and if you are pulling high, let the group know behind you...
and unless you are last out of the plane, you have no right to say you are pulling at 3,000 and pull at 4,000 b/c you made a poor spot or a poor call to jump...you make your decision and stick with it...the group behind you is trusting you.

[billvon 2,421]

Agree with most of it, but this angle thing keeps coming up . . .
>If there is miscommunication of upper winds, even if not, you should be looking all the wayout of the
>plane to check your spot and watching the group ahead of you until they are at a 90 degree angle.
In most cases the group ahead of you will _never_ appear to be directly below you - and if they somehow do, it would be a mistake to get out of the plane at all, since the plane is going backwards with respect to winds at lower altitudes. Perhaps you meant 45 degrees. This makes more sense, but still tells you nothing about winds. Whether the uppers are 10 knots or 80, they will reach that 45 degree angle in the same amount of time.
-bill von

[PhreeZone 15]

You can make a decision but a lot can blow it apart..... freefall collision and someone gets hurt, they dump out high, a premature opening, lots of things can make jumpers open off their predeterminted altitudes. Vertical seperation is no substitue for horzontial speration.
And there is no magical angle that the group before you needs to be at before its safe to leave the plane. 90 degrees are straight under you, clearly bad. We've proven time after time why the 45 degree thing is bogus. The Way old time thing about wait till the group turns the first point is totally wrong, and almost any other visual cue is junk. The only way to ensure saftey is horizonal seperation. Horizonatal seperation is only achieved by proper exit seperation.
Cause I don't wanna come back down from this cloud... ~ Bush

[AndyMan 7]

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In most cases the group ahead of you will _never_ appear to be directly below you - and if they somehow do, it would be a mistake to get out of the plane at all, since the plane is going backwards with respect to winds at lower altitudes. Perhaps you meant 45 degrees. This makes more sense, but still tells you nothing about winds. Whether the uppers are 10 knots or 80, they will reach that 45 degree angle in the same amount of time.

In Kalends demo saturday, he showed that not only is the 45 degree theory wrong, it's impossible. In his simulations, the jumpers NEVER got to a 45 degree angle from the plane. On a no wind day they never got much past 30 degrees. In moderate winds they went to 28 degrees. They simply fell off too quickly.
And yes, my brain still hurts.
_Am
ICQ: 5578907
MSN Messenger: andrewdmetcalfe at hotmail dot com
Yahoo IM: ametcalf_1999

[mgaillar 0]

Could someone please point me to the resources that reference why the 45 degree angle is wrong or does not work. I am interested in reading about this as I was taught that this is one method to insure adequate horizontal separation.
Thanks!
Matt
http://www.skydiveorange.com

[diverdriver 5]

http://www.iit.edu/~kallend/skydive/
Read ALL of the sections. It's a whole program and very informative. Go to the "Powerpoint Presentation on Seperation."
Chris Schindler
ATP/CFII
D-19012
www.DiverDriver.com

[kallend 1,640]

>>>Could someone please point me to the resources that reference why the 45 degree angle is wrong or does
not work. I am interested in reading about this as I was taught that this is one method to insure adequate
horizontal separation.
Thanks!
Matt<<<
1. people do the strangest things. By tracking up or down the flight line you can change the "angle" by quite a lot. When I exit first on my 10-way team (Grrr) I "surf" the slipstream and make an angle of 45 degrees almost immediately. OTOH, someone diving out will have a completely different "angle".
2. just do the physics, f=ma, for, say, a spaceball (which won't do the strangest things) and you'll see the angle doesn't reach 45 degrees.
3. Wind definitely affects horizontal separation, but has no effect on the "angle" unless you pass through a windshear.
4. Look at some photos of skydivers exiting on a big-way attempt. You will see a stream of jumpers falling from the planes. Get out a protractor and measure the angle the stream makes with the vertical and draw your own conclusions
3.

[kallend 1,640]

<<<And yes, my brain still hurts.>>>>
Remember that the demo was for specific conditions (jump-run speed 80 kts IAS, jumper fall rate, etc).
A faster jump run speed or slower jumper fall rate will give larger angles. But it's not the actual angles that are the problem, it's that the angle and the horizontal separation are really not related to each other in a meaningful way.

[SAMPLEKSample 0]

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Vertical separation is definitely no substitution for horizontal...but dont you think they should both be considered???[/reply

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[scottbre 0]

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Vertical separation is definitely no substitution for horizontal...but dont you think they should both be considered???

I'm no expert but it seems to me that the only type of separation that makes any difference is horizontal separation. Vertical makes no difference at all.

"Your mother's full of stupidjuice!"
My Art Project

[lummy 4]

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Vertical makes no difference at all.

DISCLAIMER I'm not an expert either, FAR from it

Let's think about it this way then, (ALL freefly in the example) if your 3 way head down is planning on opening at 3k and you have 2 solos as well , one planning on pulling at 3,5 and the other 4, wouldn't you want the lower pullers going first? In that event (providing everyone pulls where they say they will) no one is going thru anothers opening altitude while still in freefall.
Granted, it's not making accomodations by adjusting your opening altitude, but it is taking into consideration and making vertical seperation

I promise not to TP Davis under canopy.. I promise not to TP Davis under canopy.. eat sushi, get smoochieTTK#1

[kallend 1,640]

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(providing everyone pulls where they say
they will)

Well, you just destroyed your own argument with that condition.

[quade 3]

So, let's say the guy above has a cutaway . . . where's your verticle separation now?

quade -
The World's Most Boring Skydiver

[freeflir29 0]

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where's your verticle separation now?

How's that saying end?

"The altitude above you, the runway behind you, and the gas that was in your tanks 5 minutes ago. "

[lummy 4]

That I did, didn't I?

Just for the record, I wasn't trying to make a case for one or the other, but stating a personal opinion that both horizontal and vertical seperation should be part of the equation with Horizontal being first and foremost.

Are you guys trying to say that you wouldn't take vertical seperation into account at all? Why?

I promise not to TP Davis under canopy.. I promise not to TP Davis under canopy.. eat sushi, get smoochieTTK#1

[freeflir29 0]

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Are you guys trying to say that you wouldn't take vertical seperation into account at all?

Well...sort of....vertical separation isn't a predictable variable. Sure....if someone is pulling high (Say 4000 or more) you put them out last just in case they actually pull there. We all know that a mal can happen, and that could put the jumper under canopy MUCH lower. You also don't want someone opening their canopy and flying around up or down the jump run while you still have jumpers in free fall. Verticle separation is a consideration but it's definately far secondary to horizontal. The only time it counts is when the horizontal separation measures fail.

[AndyMan 7]

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Well...sort of....vertical separation isn't a predictable variable.

Well, sure. People pull at the wrong altitude, and people have prematures and cuttaways. But by the same token, novice freeflyers track up and down the jumprun without even noticing, people in different groups intentionally track towards each other, and wind drift effects groups of different sizes differently.

I'm clearly on the side of horizontal separation. I've seen Kallend's presentation, and it made a lot of sense, once my head stopped hurting. But I refuse to say that verticle separation is worthless. It's important, just not as important.

This is, after all why we put students and "high pullers" at the nose of the plane, even if they're doing RW.

This debate will never be settled until DZO's give each group their own pass, which will happen shortly after hell freezes over, or the Maple Leafs win the Stanley Cup.

_Am

__

You put the fun in "funnel" - craichead.

[Zenister 0]

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The Way old time thing about wait till the group turns the first point is totally wrong

that was actually a guideline at some point?!?

yeeks, thats like 1/2 count after Airspeed exits..

____________________________________
Those who fail to learn from the past are simply Doomed.

[crazy 0]

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Are you guys trying to say that you wouldn't take vertical seperation into account at all? Why?

Question of risk, in terms of probability to have a collision. Double the horizontal separation and you reduce the risk by 4. double the vertical separation and you won't change significantly the risk (in some cases you will even increase the risk because you provide an opportunity to use the vertical separation to reduce the horizontal separation). Hence, vertical separation is a very secondary point compared to horizontal separation.

Imagine you are in a full load of solos from a MI-8. Would you jump with only 500ft horizontal separation and no vertical separation at all? Would you jump with no horizontal separation (stationary) at all and 500feet vertical separation?

Now, once all the important parameters have been considered, if there is still some freedom left in the order of the groups, of course it doesn't hurt to use vertical separation.