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kallend

The "45 degree rule" for exit separation DOES NOT WORK

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Ok, your opinion is noted. However, I will ask you for a third time, if you do not agree with the methods described in this thread WHAT IS YOUR SOLUTION? We can go on and on dancing around this but I have yet to see you post anything that provides a solution better than the chart. So please share some of your "conceptual grasp" with the rest of us and show us how to do it right.***

This is a link to the notes I put together for a seminar on the subject. If you read it through, you may see what I am trying to point out.

The information has been out there, from a variety of sources, for quite some time. If you understand the concept, you can generally figure out an appropriate procedure and work with its limitations.

The response I gave elsewhere in this thread provides a Cliff's Notes version of a workable procedure that has a legitimate basis.


Blue skies,

Winsor

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This is a link to the notes I put together for a seminar on the subject. If you read it through, you may see what I am trying to point out.



I get that, as do others who have taken the time to understand the issue. I also understand why you used some of the examples that you did. I don't dispute what you have put out there.However at the end of all of that there is no viable alternative offered that allows the average jumper to make heads or tales of the issue to achieve adequate seperation. You state the following:


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Maintaining a mile and a half between groups which is around 61 seconds at 80 knots is simply not a practical solution. The bottom line is that we must settle for what separation we can get.

If you think your 10 second delay is any guarantee of separation, in and of itself, think again.




You address the other variables that happen in freefall that can and do cause issues which is part of the equation as well. While every thing can be explained academically, it still doesn't supply a workable solution in the real world. Conversely,real world application of the time/ ground speed method,while not absolute or academically correct , is used every weekend on DZ's around the world without major issue.

Granted, that is not an explanation or justification that most like to hear as it is akin to the "big sky" theory. However, given the constraints skydivers are put in there is no "absolutely right" way to tackle this issue(your statement above conceeds this). Given those constraints, it has been conceeded by several people with physics degrees and or conceptual knowledge within this thread that TIME is an acceptable,but not perfect,alternative/ solution, to this issue and it can be conveyed to other jumpers in a matter of seconds without a class in physics and or math. I will say it is an imperfect solution that can be applied to the imperfect world we live in with generally acceptable results.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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We, as usual, are talking at cross-purposes here.

In the examples I used to determine what is "sufficient separation," my point was to show that separation is but one part of the equation.

If you used ground speed for your calculations, *with the caveat that the minimum delay is based on true airspeed*, your standpoint would be defensible.

Using ground speed as your sole criterion allows for circumstances where groups at deployment altitude are right on top of each other.

Using ground speed to determine an appropriate delay is not much more defensible than is using the 45 degree rule. That you usually don't fly into each other is great, but the concept is still terminally flawed.

Being easy enough that it can be used without comprehension is hardly a recommendation.

A true airspeed minimum with a multiplier for uppers is pretty simple. If people were to lay off counting fleas, checking their protractor, and verifying progress over real estate they might use something valid.


Blue skies,

Winsor

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I am by no means a Moron...But you guys just gave me a Freakin headache.... I think ill just go back to guessing at what time seems sort of safe and go with that.....

You know and with what jump pilots seem to make for wages and it seems that alot of them are just there to get hours so they can go on to a better flying Career how many of them do you think are reallubg going to do all that math plus do the other stuff they are doing and be accurate... Maybe we should require all jump Planes to have a second seater who is a Math guy and thats his entire job, to do the MATH. I bet that would do wonders for jump ticket prices...

So can we get a "Jump run Seperation for Dummies" version of all this mumbojumbo? Thanx.
I mean after all, WE JUMP OUT OF AIRPLANES, there is Risk. What I want is something that works for , NOT REMOVING ALL the Risk but something that gives me some slightly better odds for seperation with out a headache.

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I am by no means a Moron...But you guys just gave me a Freakin headache.... I think ill just go back to guessing at what time seems sort of safe and go with that.....

You know and with what jump pilots seem to make for wages and it seems that alot of them are just there to get hours so they can go on to a better flying Career how many of them do you think are reallubg going to do all that math plus do the other stuff they are doing and be accurate... Maybe we should require all jump Planes to have a second seater who is a Math guy and thats his entire job, to do the MATH. I bet that would do wonders for jump ticket prices...

So can we get a "Jump run Seperation for Dummies" version of all this mumbojumbo? Thanx.
I mean after all, WE JUMP OUT OF AIRPLANES, there is Risk. What I want is something that works for , NOT REMOVING ALL the Risk but something that gives me some slightly better odds for seperation with out a headache.



Okay, I keep forgetting that Math is a foreign language for a lot of people.

What we have here is, however, "kindergarten algebra," the mathematical equivalent of "See Spot run! Run, Spot, Run!" Anyone who can balance their checkbook should be able to guesstimate the appropriate values in their head.

Come on, this is not Rocket Surgery. How accurate do you think the count typically is between two groups? Do you think " gimme ten seconds" is likely to result in anything like 10.00 seconds? How exactly do you think the typical skydiver tracks to his/her quadrant?

In practice, from an airplane going into the wind, using ground speed will put people out with sufficient separation most of the time.

If you conclude from this that ground speed is the critical parameter, I refer you to my tethered and free balloon models. The tethered balloon has zero ground speed but gives separation, the free balloon has ground speed and no separation.

John Kallend's PowerPoint presentation (referenced in this thread and on this site) does a great job of making clear the whys and wherefores of exit separation. He also says to go ahead and use ground speed in your calculations - so long as you understand the limitations of the method.

I have landed off, I have had canopy collisions and near-misses, and I have lost friends to midair collisions. When all is said and done, I am more concerned with achieving adequate separation than the method by which it is achieved.

As H. L. Mencken said, "For every complex problem, there exists a solution that is simple, elegant - and wrong."

Einstein said something to the effect that "Every problem should be made as simple as possible - but no simpler."

Beware of dumbed-down theory. It is typically wrong - sometimes dangerously so.


Blue skies,

Winsor

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If you used ground speed for your calculations, *with the caveat that the minimum delay is based on true airspeed*, your standpoint would be defensible.

Using ground speed as your sole criterion allows for circumstances where groups at deployment altitude are right on top of each other.

Using ground speed to determine an appropriate delay is not much more defensible than is using the 45 degree rule.



Although jumpers might at times say they are basing their separation "on ground speed", in reality they may only be using observed ground speed to modify what they already know -- they're already familiar with the aircraft they are jumping and are used to the typical separation times needed, for an aircraft of that airspeed.

This doesn't change the whole discussion about what is a simple but not too simple way to decide separation. But I think it makes things look a little less pessimistic about jumpers who seem to be looking at ground speed only.

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This 45 degree myth sucks yet seems to work. Is there any other 'easy to understand' concept that 'works really well'. I understand the separation deal. You should not be worried if i'm exiting after you. It's the newbies who count fast who I can tell that the f!@#$cker is going to exit too close to me and my group that I would like to feel comfy with.

Counting to "10-one thousand" or more is very easy. Few people can judge 45 degrees with any accuracy anyway. But I can sure as hell count to 10.

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I am by no means a Moron...But you guys just gave me a Freakin headache.... I think ill just go back to guessing at what time seems sort of safe and go with that.....

You know and with what jump pilots seem to make for wages and it seems that alot of them are just there to get hours so they can go on to a better flying Career how many of them do you think are reallubg going to do all that math plus do the other stuff they are doing and be accurate... Maybe we should require all jump Planes to have a second seater who is a Math guy and thats his entire job, to do the MATH. I bet that would do wonders for jump ticket prices...

So can we get a "Jump run Seperation for Dummies" version of all this mumbojumbo? Thanx.
I mean after all, WE JUMP OUT OF AIRPLANES, there is Risk. What I want is something that works for , NOT REMOVING ALL the Risk but something that gives me some slightly better odds for separation with out a headache.

Add another human eliment which is a 'jump master/separation master/ spotter/ load organizer'. A person who is on each load and organizes the separation between groups. Sure that person would take up a seat on the load and would mtl require a ticket and be jumping last out. there are just not enough incidents due to separation that would account the need for such a slot.

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This 45 degree myth sucks yet seems to work. Is there any other 'easy to understand' concept that 'works really well'. I understand the separation deal. You should not be worried if i'm exiting after you. It's the newbies who count fast who I can tell that the f!@#$cker is going to exit too close to me and my group that I would like to feel comfy with.

Counting to "10-one thousand" or more is very easy. Few people can judge 45 degrees with any accuracy anyway. But I can sure as hell count to 10.

Yep, I counted to 10-one thousand today on 6 jumps. Winds were high , at 10-one thousand I climbed out , my skysurfer got into position and we exited at just over 15- one thousand. I estimate we had between 1,000 and 1,500 ft of separation between the next group. Counting worked well. I also watched the next group, no groups that exited ahead of us ever made it to 45 degrees. Maybe 30 degrees. I was still looking at the group as if they'd make it to 45 degrees. Jumping with 80kt uppers flying into the wind means more time between groups. We still could've given the group ahead of us more time, but were at a safe distance horizontally and vertically. Vertically we were open at 5grand and others around 3 grand. Larry

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Add another human eliment which is a 'jump master/separation master/ spotter/ load organizer'. A person who is on each load and organizes the separation between groups. Sure that person would take up a seat on the load and would mtl require a ticket and be jumping last out. there are just not enough incidents due to separation that would account the need for such a slot.



Newbie Question: Isn't there supposed to always be one person on each load that serves as the jumpmaster (a USPA recommendation/rule)?

- David
SCR #14809

"our attitude is the thing most capable of keeping us safe"
(look, grab, look, grab, peel, punch, punch, arch)

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Okay, I keep forgetting that Math is a foreign language for a lot of people.

Well Math is actually something that has always come natural for me. In the 9th grade I completed Algebra, geometry, Trig, Calculus, and Math analysis. So it isn’t that Math is foreign, its that I want to enjoy my skydive with out having to think out the math of this equation just to get separation. I’d like to be able to think about the Dive Plan I have with the fine folks I am jumping with.

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What we have here is, however, "kindergarten algebra," the mathematical equivalent of "See Spot run! Run, Spot, Run!" Anyone who can balance their checkbook should be able to guesstimate the appropriate values in their head.

Again I would really like to focus on my jump not sit there and do math for everyone on the plane.

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Come on, this is not Rocket Surgery. How accurate do you think the count typically is between two groups? Do you think " gimme ten seconds" is likely to result in anything like 10.00 seconds?


As far as this goes...If you are trained to count in a Cadence, as we were in Army jump School, it is pretty easy to get an accurate count and be fairly consistent.
Example: I asked my wife to run a stop watch and not tell me the times until we were done with 5 attempts. Using the cadence I was trained with in the Army, I counted from 1 thousand, 2 thousand…up to 10 thousand. These are the times she reported.
10.30 seconds
9.89 seconds
10.21 seconds
10.20 seconds
9.80 seconds
That’s an Average of 10.08 seconds with only a variance of .50 seconds over 5 attempts. That seems pretty damn consistent to me.

I just don’t understand why something so simple has to become some long drawn out Math Class.

Most people understand the risk involved in skydiving. If they don’t then they shouldn’t be skydiving. I really dont see a need to make this all so damn technical and scientific for the average jumper.

Just seems to me that if you set a basic base time between groups then adjust from there for changing conditions and groups the world will be right.

Teach that in FJC's. Teach a Cadence before they jump. Hand them a stop watch and have them practice during class breaks.

Seems pretty simple to me..

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Add another human eliment which is a 'jump master/separation master/ spotter/ load organizer'. A person who is on each load and organizes the separation between groups. Sure that person would take up a seat on the load and would mtl require a ticket and be jumping last out. there are just not enough incidents due to separation that would account the need for such a slot.



Newbie Question: Isn't there supposed to always be one person on each load that serves as the jumpmaster (a USPA recommendation/rule)?

- David

Not certain about that one. No jumpers on the aircraft I was on today had 'a' jumpmaster, we each jumpmastered ourselves. During AFF training program students typically will have an instructor with them. As an licensed jumper 'you' are your own jumpmaster on most jumps. Your required to do the things that you learned in AFF or student training ' the basics'. Such as climbing into the aircraft without banging your head, handle checks, preplanned dive, predetermined pull altitude, exit order in reference to other groups, knowing landing direction, spotting (watching/looking for aircraft that you might collide with) , other jumpers, and where the dz is in relation to the 'spot', time between groups(separation), handle checks oh i said that one already, again handle checks, pulling on time, flying with the traffic pattern, landing safely, and most of all not killing me. Larry

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Okay, I keep forgetting that Math is a foreign language for a lot of people.

Well Math is actually something that has always come natural for me. In the 9th grade I completed Algebra, geometry, Trig, Calculus, and Math analysis. So it isn’t that Math is foreign, its that I want to enjoy my skydive with out having to think out the math of this equation just to get separation. I’d like to be able to think about the Dive Plan I have with the fine folks I am jumping with.

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What we have here is, however, "kindergarten algebra," the mathematical equivalent of "See Spot run! Run, Spot, Run!" Anyone who can balance their checkbook should be able to guesstimate the appropriate values in their head.

Again I would really like to focus on my jump not sit there and do math for everyone on the plane.

Quote

Come on, this is not Rocket Surgery. How accurate do you think the count typically is between two groups? Do you think " gimme ten seconds" is likely to result in anything like 10.00 seconds?


As far as this goes...If you are trained to count in a Cadence, as we were in Army jump School, it is pretty easy to get an accurate count and be fairly consistent.
Example: I asked my wife to run a stop watch and not tell me the times until we were done with 5 attempts. Using the cadence I was trained with in the Army, I counted from 1 thousand, 2 thousand…up to 10 thousand. These are the times she reported.
10.30 seconds
9.89 seconds
10.21 seconds
10.20 seconds
9.80 seconds
That’s an Average of 10.08 seconds with only a variance of .50 seconds over 5 attempts. That seems pretty damn consistent to me.

I just don’t understand why something so simple has to become some long drawn out Math Class.

Most people understand the risk involved in skydiving. If they don’t then they shouldn’t be skydiving. I really dont see a need to make this all so damn technical and scientific for the average jumper.

Just seems to me that if you set a basic base time between groups then adjust from there for changing conditions and groups the world will be right.

Teach that in FJC's. Teach a Cadence before they jump. Hand them a stop watch and have them practice during class breaks.

Seems pretty simple to me..

Your well trained at that 10 second count. If you are exiting after me, I would'nt worry too much about you and the separation. Only if all jumpers could be as smart as you, even when up jumpers are yelling at them to 'go' even if they have'nt reached 10 seconds.

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Only if all jumpers could be as smart as you, even when up jumpers are yelling at them to 'go' even if they have'nt reached 10 seconds.



LOL then they need to learn to look back at them and present a GREAT 1 Finger Salute. I am sure that turning back and looking at them might take a couple more seconds :)

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This 45 degree myth sucks yet seems to work. Is there any other 'easy to understand' concept that 'works really well'. I understand the separation deal. You should not be worried if i'm exiting after you. It's the newbies who count fast who I can tell that the f!@#$cker is going to exit too close to me and my group that I would like to feel comfy with.

Counting to "10-one thousand" or more is very easy. Few people can judge 45 degrees with any accuracy anyway. But I can sure as hell count to 10.



Why not stick a cheap digital timer by the door? You can get a kitchen timer for around $10.
...

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

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>So can we get a "Jump run Seperation for Dummies" version of all this mumbojumbo?

Simplest answer:

The distance you will get between group centers is the ground speed of the aircraft plus the speed of the winds at opening altitude, multiplied by the time you leave between groups.

Caveats:

This only works when the winds at opening altitude are the same direction. If they are from the opposite direction, you have to subtract it from groundspeed.

This is also only for same-type groups i.e. several RW groups.

This assumes people aren't drifting. If you're going to slide significantly (i.e. you're doing a solo and practicing tracking) it may not hold.

You generally need a GPS to figure out your groundspeed.

Notes:

Since separation is usually INCREASED by winds at opening altitude, you can usually neglect them (as long as they are in the same direction.) If they're strong they will only help. If they are opposite, then there's trouble in river city.

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>even when up jumpers are yelling at them to 'go' even if they have'nt reached 10 seconds.

Usually I have a fullface helmet on that makes it difficult for me to hear, and it's even harder to hear near the door. If someone is yelling and gesturing when I'm getting ready to exit, either:

a) he's telling me to go or

b) he's telling me something important, like "YOU HAVE TRAFFIC UNDER YOU!"

When I am in a position to do so, I will sometimes take my helmet off to better hear him. If it's a warning it might be a good thing I did. If it's just the usual "GO!" then I'll put my helmet back on and go. Doing so gives me a few extra seconds anyway - and reinforces the idea that _not_ yelling will get people out of the plane faster.

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You know, we don't have much yelling at our DZ. When there's a lot of small groups on the Twin Otter, we sometimes even pre-plan a second pass. Our DZOs are really cool about it. Usually it's tandems in the back, high profit margins, so no one seems to mind the extra operating time so much. We also take the time to brief noobs on how much time they should give the guy ahead of them. Only problem I've seen recently is beginning freeflyers sliding up and down the jumprun line.

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>even when up jumpers are yelling at them to 'go' even if they have'nt reached 10 seconds.

Usually I have a fullface helmet on that makes it difficult for me to hear, and it's even harder to hear near the door. If someone is yelling and gesturing when I'm getting ready to exit, either:

a) he's telling me to go or

b) he's telling me something important, like "YOU HAVE TRAFFIC UNDER YOU!"

When I am in a position to do so, I will sometimes take my helmet off to better hear him. If it's a warning it might be a good thing I did. If it's just the usual "GO!" then I'll put my helmet back on and go. Doing so gives me a few extra seconds anyway - and reinforces the idea that _not_ yelling will get people out of the plane faster.

i like your way Bill. I might use it someday. Ya, my newest helmet is pretty sealed and I cannot hear as much outside noise.

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Heard Sunday on load 4 while climbing to altitude. Experienced guy sitting beside me talking to an inexperienced guy behind me, "Just wait til we're 45 degrees behind the plane before you leave."

The 45 degree rule lives on.

On the ground the experienced guy and I had a pretty thourough debrief using the "Exit Separation Revisited" article found on this site by Bill Von Novak. I printed it out and keep it in my book of instructional articles that stay with my logbook.

Based on my jump numbers I don't have any credibility, so I am very grateful to Bill Von Novak for his expertise that I can use as an example.

A picture is worth 10 million words.

I was very encouraged when the pilot elected to make a second pass with loads that were very diverse. We tend to have belly fliers go in a chunk followed by one or two solo belly fliers pulling high, followed by free fliers followed by AFF followed by tandoms, and maybe a birdman at the very end. It tends to put a lot of pressure on spacing.

Obviously a very complex subject. It's unfortunate that the most experienced jumpers (Tandom and AFFIs) are the ones in the back of the plane screaming for the inexperienced ones to GO. They should be asking the pilot for a second pass when there several groups.

Thanks to the Professors for their discussion.

MH

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The 45 degree rule lives on



It does. The largest DZ in Europe generally uses it as their guide for exit seperation...



Cool. Now it's been established that they are wrong.

Where's that? Empuria?
----------------------------------------------
You're not as good as you think you are. Seriously.

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