Forums: Skydiving: Safety and Training:
The "45 degree rule" for exit separation DOES NOT WORK

 

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Freeflysmiley  (C License)

Nov 26, 2007, 2:07 AM
Post #201 of 364 (2710 views)
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Re: [diablopilot] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
In reply to:
Quote:
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?

Yep Sly


brettski74  (C 3197)

Nov 26, 2007, 5:43 AM
Post #202 of 364 (2674 views)
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Re: [kallend] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
In reply to:
Quote:
The 45 degree rule lives on
It does. The largest DZ in Europe generally uses it as their guide for exit seperation...

I don't know that I can do any more.Unimpressed

Maybe this will help. The assertion is that pschologically, having a discussion entitled The "45 degree rule" for exit separation DOES NOT WORK may in the long term reinforce the existence of this rule in the minds of some people. It may be more effective to stop talking about the incorrectness of the 45 degree rule and concentrate on just talking about valid methods.


JohnMitchell  (D 6462)

Nov 26, 2007, 7:37 AM
Post #203 of 364 (2645 views)
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Re: [brettski74] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

Maybe start calling it The 45 degree Myth.Crazy

There are a lot of scientific illiterates in the world. Trying to explain things to them logically can become a real struggle. Unsure


frazeebd  (A 52107)

Nov 26, 2007, 8:36 AM
Post #204 of 364 (2625 views)
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Re: [JohnMitchell] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

I did my AFF on September 1st of this year, and was taught the 45 degree rule. In fact, it was only when I decided to come on here and do some posting and reading and research that it really came to light how much of a failure the 45 degree rule can be.....

Talking about these things on here helped me. I'm sure I'm not the only one. Keep it up.


pilotdave  (D License)

Nov 26, 2007, 9:28 AM
Post #205 of 364 (2611 views)
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Re: [frazeebd] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

Quote:
Talking about these things on here helped me. I'm sure I'm not the only one. Keep it up.

At real dropzones, I think I've heard the 45-degree rule taught twice, and I've heard it explained to be nonsense at least a dozen times. I'd bet those numbers would be reversed if kallend wasn't posting this stuff.

Dave


JohnMitchell  (D 6462)

Nov 26, 2007, 6:29 PM
Post #206 of 364 (2537 views)
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Re: [pilotdave] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
At real dropzones, I think I've heard the 45-degree rule taught twice, and I've heard it explained to be nonsense at least a dozen times. I'd bet those numbers would be reversed if kallend wasn't posting this stuff.
Ouch. Unsure

Yes, I've heard some really good jumpers explaining how it "works" to newbies. I'm glad Kallend's still posting on it. I really think we should start referring to it as the "45 degree Myth."


murps2000  (D 23114)

Nov 26, 2007, 7:50 PM
Post #207 of 364 (2524 views)
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Re: [kallend] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

I don't know that I can do any more.
Quote:

You can still get on the phone and call Empuria and tell them how many fleas are on your dog.


CornishChris  (C 102981)

Nov 27, 2007, 1:35 AM
Post #208 of 364 (2498 views)
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Re: [kallend] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

As a point of interest I wonder whether Empuria has any more incidents due to using this rule than any other DZ that does not. When I jump there I have never had an issue, but then I tend not to use the rule to calculate my exit seperation.

From a gut feel they don't seem to have any more problems...


jurgencamps  (D License)

Nov 27, 2007, 2:16 AM
Post #209 of 364 (2497 views)
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Re: [CornishChris] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
Quote:
The 45 degree rule lives on

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

That is not my experience in Empuria. They always explained me another way (time between two groups).
Who (which instructor, ...) told you that or where do you get your information from?

Jurgen


freeflysteve  (D 102080)

Nov 29, 2007, 3:24 AM
Post #210 of 364 (2371 views)
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Re: [CornishChris] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

 
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Quote
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The 45 degree rule lives on

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


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NO IT DOES NOT WORK,
Just cos a DZ says use it or an instructor, does not mean it works,it is an aid only to be used in conjuction with making sure you actually look to see jumpers who have exited before you whilst you are counting the relevant time away depending on ground speed of aircraft and different jumper group FF or RW for example who went before you,etc etc.Mad


CornishChris  (C 102981)

Dec 4, 2007, 9:08 AM
Post #211 of 364 (2249 views)
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Re: [freeflysteve] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

Please read my post again before you get cross. I am not stating that it works, I am stating that the rule lives on. Two very different things.

And to previous post I have heard it from a range of instructors, some english, some Babylon guys too.


jumpwally  (D License)

Dec 15, 2007, 7:55 AM
Post #212 of 364 (2122 views)
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Re: [CornishChris] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

well, they are europeans,,,,,what did u expect ? Wink


phoenixlpr  (D 3049)

Dec 15, 2007, 8:15 AM
Post #213 of 364 (2115 views)
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Re: [jumpwally] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
well, they are europeans,,,,,what did u expect ? Wink
Yes, We _do_ are! So what do you expect? Pirate


Premier slotperfect  (D 13014)

Dec 15, 2007, 7:19 PM
Post #214 of 364 (2073 views)
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Re: [phoenixlpr] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

Let's get the thread back on topic, please.


winsor  (D 13715)

Dec 16, 2007, 8:02 AM
Post #215 of 364 (2042 views)
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Re: [slotperfect] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
Let's get the thread back on topic, please.

No problem.

The deceptive part of the "Exit Separation" issue is that it is a stochastic process - which is to say that the whole thing revolves around probability.

An analogy is the likelihood of a head-on collision. If you drift into the oncoming lane on a two-lane road, your odds of having a head-on collision go up, but if you stay in your lane the odds of having a head-on collision are still nonzero.

If you go back and forth between your lane and the oncoming lane on a desert road with virtually no traffic, you stand a pretty good chance of getting away with it. Cross the center line at rush hour in a major city, and your odds of a crash are about 100%.

Conversely, staying in your lane on a vacant desert road nearly guarantees that you will not have a head-on collision. Being on a heavily traveled road in the wee hours of New Year's Day, there is a significant chance that a drunk will cross the centerline.

Back to skydiving.

If you have any kind of separation, whether due to delay in climbout, counting the fleas on your dog or screwing with a protractor, there is a decent chance that everyone will open in their own airspace.

If you have "optimum separation" between groups, there is still a nonzero chance that some numbnuts will track away early or otherwise be in the wrong part of the sky during opening so that a collision ensues.

Having said all of that, you are in a hell of a lot better shape by understanding what is, and going for, the minimum acceptable separation between groups.

Life is a crapshoot. It behooves you to load the dice in your favor.


Blue skies,

Winsor


d123  (B 6134)

May 26, 2011, 2:32 PM
Post #216 of 364 (1308 views)
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Re: [kallend] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

Just trying to learn and do something good at the dz where I work.
What's a better model for calculating the separations between groups (constant separation between each group no matter what they do freefly/belly solo/2way/3way/4way) for a turbine dz?


popsjumper  (D 999999999)

May 26, 2011, 4:24 PM
Post #217 of 364 (1244 views)
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Re: [d123] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In a nutshell, do the math.
How long does it take the plane to cover 1000ft on jump run?
And adjust for group sizes.


(This post was edited by popsjumper on May 26, 2011, 4:25 PM)


Premier billvon  (D 16479)
Moderator
May 26, 2011, 4:31 PM
Post #218 of 364 (1228 views)
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Re: [d123] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

>What's a better model for calculating the separations between groups
>(constant separation between each group no matter what they do
>freefly/belly solo/2way/3way/4way) for a turbine dz?

Some methods that work:

1) Look down, wait until the plane covers 1000 feet, then go. Runways are good "measuring sticks" for this. (Works provided lower winds are lighter than uppers.)

2) Wait at least 7 seconds. If uppers are high, divide them by 3, wait that number of seconds, then go. (For faster planes divide by 2.)

3) Actually do the math. Separation in feet is (jump run speed + winds at opening altitude) * time between groups in seconds, assuming jump run is into the wind and winds at opening are the same direction as on jump run but lighter. All speeds in feet per second. Make sure you are at LEAST 500 feet from the previous group, more for larger groups.


AdrianGlave  (D 33419)

May 26, 2011, 4:37 PM
Post #219 of 364 (1225 views)
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Re: [FrogNog] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

 


fly67  (C License)

May 26, 2011, 9:18 PM
Post #220 of 364 (1150 views)
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Re: [billvon] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
>What's a better model for calculating the separations between groups
>(constant separation between each group no matter what they do
>freefly/belly solo/2way/3way/4way) for a turbine dz?

Some methods that work:

1) Look down, wait until the plane covers 1000 feet, then go. Runways are good "measuring sticks" for this. (Works provided lower winds are lighter than uppers.)

2) Wait at least 7 seconds. If uppers are high, divide them by 3, wait that number of seconds, then go. (For faster planes divide by 2.)

3) Actually do the math. Separation in feet is (jump run speed + winds at opening altitude) * time between groups in seconds, assuming jump run is into the wind and winds at opening are the same direction as on jump run but lighter. All speeds in feet per second. Make sure you are at LEAST 500 feet from the previous group, more for larger groups.

Try telling this to Skydive AZ. They recently posted 4 secs between solos, 4-6 for small groups. Why make two runs when you can get everyone out in one??

Regardless of these "optimistic" exit times, it would be relatively simple to provide a clock, timer, or indicator to better time exits:
- Simple: Install a large digital clock with seconds
- Countdown timer: Install a large digital countdown timer or indicator light. The next group pushes button when previous group exits. Could be defaulted to 7 seconds (or more depending on uppers) as the minimum exit time. For larger groups simply count out more seconds as needed.
- Ground distance display: Install a ground distance display tied to GPS (or an indicator light based on a preset distance, say 1000ft). The next group pushes the button and jumps when the display shows prescribed separation distance (or indicator light).
- Better calculations... taking into account uppers, etc.

The technology exists for this (although the specific displays might not). I just don't know if the DZ would really want people to count 7-10 secs.


(This post was edited by fly67 on May 26, 2011, 9:30 PM)


Squeak  (E 1313)

May 26, 2011, 10:00 PM
Post #221 of 364 (1132 views)
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

we have al ist of Windspeed to ground speeds (for nose winds) and delays requiired for each.
These are posted right next to the Red/Yellow/green lights, before jump run wind speed is reqwuested off of the PIC, and the list is refered to.
Delays occur according to the indicated wind/groundspeed.
it's not hard to count alloud
one thousand
2 thousand
3 thousand (set up in door)
5 thousand
6 thousand
Ready,
Set,
8 thousand GO


(This post was edited by Squeak on May 26, 2011, 10:01 PM)


fly67  (C License)

May 26, 2011, 10:18 PM
Post #222 of 364 (1120 views)
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Re: [Squeak] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

No, it's not "hard to count aloud." And perhaps you have perfect 1-second interval exit counts.

But not everyone count seconds well, nor does everyone count to the same number. One person's 8-count may be 4 secs. Another may only count to 4 or 5, and even if they count seconds well, this is probably too little time.

With a clock or timer or distance meter, it's not subjective.


mjosparky  (D 5476)

May 26, 2011, 10:18 PM
Post #223 of 364 (1119 views)
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Re: [Squeak] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
we have al ist of Windspeed to ground speeds (for nose winds) and delays requiired for each.
These are posted right next to the Red/Yellow/green lights, before jump run wind speed is reqwuested off of the PIC, and the list is refered to.
Delays occur according to the indicated wind/groundspeed.
it's not hard to count alloud
one thousand
2 thousand
3 thousand (set up in door)
5 thousand
6 thousand
Ready,
Set,
8 thousand GO

Why would you use something so simple when more expensive technology is available? Once you have made the initial purchase and install it all you have left is teach all the jumpers how to use the system without breaking it.

Sparky


Squeak  (E 1313)

May 26, 2011, 10:53 PM
Post #224 of 364 (1107 views)
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

In reply to:
No, it's not "hard to count aloud." And perhaps you have perfect 1-second interval exit counts.

But not everyone count seconds well, nor does everyone count to the same number. One person's 8-count may be 4 secs. Another may only count to 4 or 5, and even if they count seconds well, this is probably too little time.

With a clock or timer or distance meter, it's not subjective.

This is why western Cutlure is DOOMEDCrazyCrazyCrazy

Common sense should be floated on the minerals exchange $1000 per ounce of gold is NOTHING compared to the rare nature of CDFCrazy


Premier billvon  (D 16479)
Moderator
May 26, 2011, 11:30 PM
Post #225 of 364 (1101 views)
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK [In reply to] Can't Post

>Try telling this to Skydive AZ. They recently posted 4 secs between solos,
>4-6 for small groups.

4 seconds should be OK for solos provided they are aware of their surroundings. On a solo you're responsible for separation from other groups, whereas with more than 1 person your primary responsibility is separation from _them._

However, students who do not yet have this awareness do often need more time when jumping from altitude.

>4-6 for small groups.

That's a little fast if they are giving that much time between _exits._ It's very hard to get a typical 4-way-plus-camera out in less than 7 seconds, so even if people are climbing out one after the other you're usually fine.

>Countdown timer: Install a large digital countdown timer or indicator light.
>The next group pushes button when previous group exits. Could be
>defaulted to 7 seconds . . .

This would lead to people either a) waiting 10-15 seconds between exits (which is way too long or b) people looking at the clock instead of looking down and/or concentrating on the exit (which is even worse.)

>I just don't know if the DZ would really want people to count 7-10 secs.

They definitely don't, and people shouldn't! It's 7 seconds between _exits_ not 7 seconds in the door. On a typical (fast) 4-way exit at Perris when I'm doing camera, the process is:

-previous group exits
-I get to the door (.5 second)
-I stick my head out and look down (.5 second)
-I climb out and float, point climbs out (1 second)
-I move back to the step (2 seconds) while tail and outside center get into position
-Inside center takes grips (2 seconds)
-"Still" part of exit (1 second)
-Shake ready set go (2 seconds)

That's 9 seconds, and that's leaving zero time in the door. And that's Fury, which is a fairly experienced team. A faster 4 way might shave that to 7 or 6, but it's quite hard to go faster than that - so _usually_ you're OK. When winds are high you have to wait a bit longer; I usually take the extra time to look around a bit more in the door.


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