Exit Order Safety Article

[popsjumper 2]

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Sorry your argument doesn't make any sense to me.

Read the first eight (blue) links on this website:

http://mypages.iit.edu/~kallend/skydive/

You beat me to it in this thread but I beat you to it in the 45 Degree rule thread that I resurrected to counter this brazenly deficient discussion on exit separation.



ATTENTION all you young jumpers out there learning about exit separation!!!!!!!

Do NOT let anyone suggest to you to use the 45-degree rule. Only time works properly. That time is based on an arithmetical calculation, not someone's ambiguous idea of 'degrees'

Download Kallend's animated demonstration of it and see for yourself.

Search DZ.com forums for '45 degree' and read more about it.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[rehmwa 2]

The angle of exit from a plane with a fixed airspeed will look the same every single time for an observer point of view located on that same plane. the jumpers and the observer are in the same airmass and the plane is penetrating that airmass in same way regardless of the winds that day......so the relative motion of jumpers and plane is the same no matter the conditions

This is regardless of the winds or combination of the winds that day. That's why observation of the jumpers from the door doesn't give usable information for separation (other than provide a random delay just from the action - still better than nothing)

for those wanting to be able to eyeball it from the plane, a better method is to check out the progress the plane is making across the ground, not looking at jumpers that are in the same moving airmass as the plane itself - more accurate inferences can be made from reading the relative ground reference

however, there is still no substitute to just figuring it out directly

Edit: you guys are a bit rough on Brian. He's given so much to the sport, I'd think communicating good info to him is a lot more productive that just hammering statements about "credibility" etc I see in a couple posts. Of course, I think that's also a better approach for anyone - great mentors and teachers, or brand new jumpers.

I think this is just a great example of how we all have info to learn, no matter how knowledgable, and when I miss on something, I hope that corrections and feedback are respectful and not abusive so I can take it a positive fashion and pass it on.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[popsjumper 2]

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Edit: ...I'd think communicating good info... is a lot more productive that just hammering statements about "credibility" .

You are right and I stand corrected.

It's just so rare that we get to hammer Brian it's hard to resist the opportunity.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[rehmwa 2]

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Edit: ...I'd think communicating good info... is a lot more productive that just hammering statements about "credibility" .

You are right and I stand corrected.

It's just so rare that we get to hammer Brian it's hard to resist the opportunity.

I hadn't thought of it that way

I miss the background in these things (a lot of you guys know each other from way back) and sometimes I read good natured ribbing as something it's not.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[BrianSGermain 1]

I stand corrected. The 45 rule is only part of the formula for creating adequate separation, as the amount of time in relationship to the aircraft's ground speed is critical, no argument. I wrote that post quite late at night, and did not think it through. Sorry about that to all of you who read it.

So, Popsjumper, who are you really? Do you have 100,000 jumps and have been jumping for 99 years? Wow those are some amazing credentials. Isn't it moral to lie about your stats? Who are you, really?

I try very hard to help the skydiving community because I love skydivers, plain and simple. I cannot always be perfect, and I rely on the people to teach me the correct response when I am standing on the wrong side of the line. That is how we stay alive in this sport. We listen, and we keep our egos out of the process. I want to learn the truth, especially when I am wrong.

So, for those of you who took the time to clarify my incomplete comment, I thank you. For those of you who did so with love, I thank you. For those of you who did so with sharp words bordering on slander, I hope the world leads you to learn that being nice to people is the way to go.

Blue Skies All Of YOU,
Brian

Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

[mark 102]

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The 45 rule is only part of the formula for creating adequate separation. . .

Ummm, no. The 45 rule is not any part of the formula.

Mark

[dgw 8]

Just a curiousity on my part - I'm cognisant of why the 'standard' 45 degree rule is not a valid rule for exit seperation. I've always understood it to be 45 degrees relative to the horizontal plane of the aircraft. But, when asked, Brian said it is 45 degrees relative to the horizon, which is not the same at all. Without doing sums, I just wondered about the rational (if any) of this 'new angle' on the 45 degree rule...

[dreaming13000 1]

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I stand corrected. The 45 rule is only part of the formula for creating adequate separation, as the amount of time in relationship to the aircraft's ground speed is critical, no argument. I wrote that post quite late at night, and did not think it through. Sorry about that to all of you who read it.

So, Popsjumper, who are you really? Do you have 100,000 jumps and have been jumping for 99 years? Wow those are some amazing credentials. Isn't it moral to lie about your stats? Who are you, really?

I try very hard to help the skydiving community because I love skydivers, plain and simple. I cannot always be perfect, and I rely on the people to teach me the correct response when I am standing on the wrong side of the line. That is how we stay alive in this sport. We listen, and we keep our egos out of the process. I want to learn the truth, especially when I am wrong.

So, for those of you who took the time to clarify my incomplete comment, I thank you. For those of you who did so with love, I thank you. For those of you who did so with sharp words bordering on slander, I hope the world leads you to learn that being nice to people is the way to go.

Blue Skies All Of YOU,
Brian

+1

sheeesh, some of these guys are always looking for a fight of ANY kind.

When I saw the words "45 degree angle" I thought to myself "oh shit.....here it comes." You haven't lost any credibility in my book and I've been lurking these forums for many moons now.

thanks for all you've done for the sport Brian.

"A man only gets in life what he is believing for, nothing more and nothing less" Kenneth Hagen

[kallend 1,623]

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I prefer to use my eyes and wait until I see the previous group behind the airplane drift to at least a 45 degree angle.
BG

Sorry Brian, but that is complete nonsense.
www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=1971076;page=1;sb=post_latest_reply;so=ASC;mh=25;

...

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

[BrianSGermain 1]

Hi Everyone!

It would appear that people do not agree with the idea of using your eyes in the door as a means to create exit separation, and by mentioning this idea, I have provoked a great deal of unrest. I am sorry. I assumed that people already knew to wait significantly longer when it is windy, and was merely trying to point out that looking at the previous group will give you a better idea of whether they are still underneath the airplane. Without adding a significant delay on a windy day, the 45 degree idea is pointless. I was merely adding an additional aspect of the process called "direct observation".

I hear that we need to make it clear that using the ground speed is the ONLY viable means to ascertain the appropriate time between groups when compensating for slow aircraft ground speed . That is fine with me. I hereby retract my previous statement. I will forevermore teach that the 45 degree rule is not helpful in any way, and that using your eyes can only lead to an erroneous sense of separation on a windy day.

You can all settle down now and get back to having fun.
I love you all anyway...

Sincerely,
Brian

Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

[pchapman 261]

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I stand corrected. The 45 rule is only part of the formula for creating adequate separation,

No, it has nothing to do with separation.

Except for any spurious reason because by the time someone looks at the previous group and thinks, "uh, that must be 45, they are pretty far away in any case", 5 seconds has probably elapsed so you've added some separation before climbing out.

Or if you happen to notice a head down group not falling back as fast, maybe you take more time. But that has nothing to do with 45 degrees specifically.

It has been suggested that one might as well count the fleas on Bill von Novak's dog. Do a slow mental flea count to 10, do a slow climbout, and most days, you won't die in any case.

Why is 45 wrong?

1) Read some of those long exit separation threads scattered across this site.

2) Bill von Novak's video shows multiple groups falling away for many seconds. They are always below the 45 degree line and never sweep back far enough to hit it -- except sometimes for a trivial moment just after exit, within the first couple seconds.

(I haven't seen the video lately but one place with a couple stills and exlanation by von Novak is at http://www.pirep.org/forum/viewtopic.php?t=1180)
[Edit: more stills posted by Bill v N in http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=951741;]

Makes sense: near the airplane the airplane is still moving 80 kts or whatever forward and the jumpers quickly decelerate from that horizontally (belly fly), and are just picking up vertical speed. Since it is all the same air mass near the plane, for a moment they drop aft of the 45 line. Later, the plane is still doing 80 kts horizontally and the jumpers are doing 100 kts+ vertically, so the jumpers, the rest of the way to opening, are below the 45 degree line.

For freeflyers, low drag head into the wind on exit, they probably won't even drift back near 45 degrees at any time.

[That's for all sorts of typical into wind flights. One can create special scenarios with low uppers and 120 kt lowers where jumpers would drift back past 45 degrees. But that doesn't matter if it is shown that in all sorts of regular situations, the jumpers never go aft of 45 degrees except possibly just after exit.]


3) It has also been pointed out that if the big changes in wind speed don't occur near the aircraft, there is absolutely no difference in the angle of fall relative to the aircraft from day to day near the aircraft.

So whether you look at a real 45 degrees or some other fantasy 45 units of angle, you would see no difference on days with different winds.

If the uppers from 10,000' on up to jump run at 13,000' are 80 kts , a 4 way team will fall away the same on every day (for 20 seconds), whether the winds down at 3,000' are zero or 80.

Now if the differences in wind speed are spread out evenly across all altitudes, sure, there'll be a little change in angle from day to day. But that may only be a few degrees in difference between a strong and low upper day, and probably impossible to judge. (e.g., I calculated for a day with calm winds at opening and 40 kts at jump run, compared to a calm day, and found about a 3 degree change between the two days, for jumpers who have been in the gradually changing winds for 12 seconds after exit. Not bloody likely that you can tell the difference. Plus it still has nothing to do with "45 degrees".)


Some concepts take some thinking through to understand and be personally convinced. Read up and give it a good think!

[kallend 1,623]

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Hi Everyone!

It would appear that people do not agree with the idea of using your eyes in the door as a means to create exit separation, and by mentioning this idea, I have provoked a great deal of unrest. I am sorry. I assumed that people already knew to wait significantly longer when it is windy, and was merely trying to point out that looking at the previous group will give you a better idea of whether they are still underneath the airplane. Without adding a significant delay on a windy day, the 45 degree idea is pointless. I was merely adding an additional aspect of the process called "direct observation".

I hear that we need to make it clear that using the ground speed is the ONLY viable means to ascertain the appropriate time between groups when compensating for slow aircraft ground speed . That is fine with me. I hereby retract my previous statement. I will forevermore teach that the 45 degree rule is not helpful in any way, and that using your eyes can only lead to an erroneous sense of separation on a windy day.

You can all settle down now and get back to having fun.
I love you all anyway...

Sincerely,
Brian

Here's some more stuff:

www.dropzone.com/cgi-bin/forum/gforum.cgi?post=951741;search_string=%2045%20degree%20%20video;#951741

BTW, I still have billvon's video posted on my web site under the exit separation presentation link.

mypages.iit.edu/~kallend/skydive/

...

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

[jumpsalot-2 2]

Brain Germain, human. Although the 45 deg. rule is proven in-appropriate to judge exit seperation. One thing to point out, that we all see on jump runs. Jumpers who don't even watch the group ahead of them in freefall. Stick you damn head out the door and WATCH how they fall in relation to the plane, while also noting the planes speed or progress across the ground. Take the few seconds (7, 10, 15 etc.) to assess this info......yes in the mean time others will be yelling GO, GO, GO......but we need to make sure first before exiting......

Life is short ... jump often.

[popsjumper 2]

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So, Popsjumper, who are you really? Do you have 100,000 jumps and have been jumping for 99 years? Wow those are some amazing credentials. Isn't it moral to lie about your stats? Who are you, really?

Maybe you really meant immoral.
I'm the one who questioned your statement. The text speaks for itself...just as any poster's message.
BTW, I have more than two jumps but yes, you have outted me. I have fewer years in sport than indicated. Not even Airtwardo has that many.....ummm...I could be wrong there, though.

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I try very hard to help the skydiving community because I love skydivers, plain and simple. I cannot always be perfect,

Yep. None of us are perfect and none of us are above reproach. Not even God would get a pass if he was passing incorrect information to our youngsters.

I had no idea you were so sensitive. I'll be aware of that in the future you can be sure.

Thanks for your PM.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[popsjumper 2]

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Take the few seconds (7, 10, 15 etc.) to assess this info......yes in the mean time others will be yelling GO, GO, GO......but we need to make sure first before exiting......

Excellent point. We don't want to be lemmings and land off with the previous group if nothing else.

For the youngsters:
While you are counting the exit separation, please be looking out the door for air traffic, clouds and location at the very least. Be set up and step off AT the count.

For example, the group ahead of you leaves and you start counting while you are looking AND while you are getting set up in the door so that you can step off at the count instead of just starting your climb out at the count.

Exit separation means the time from one exit to the next....not the time from one exit to the next climb out.

You'll make those behind you very happy.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[popsjumper 2]

Speaking of Bill...being one of the prime proponents of doing the calculations and the one who did the video proof if the 45-degree fallacy, where is he in all this mess?

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[chuckakers 370]

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...and was merely trying to point out that looking at the previous group will give you a better idea of whether they are still underneath the airplane. Without adding a significant delay on a windy day, the 45 degree idea is pointless. I was merely adding an additional aspect of the process called "direct observation".

The 45 degree thing is always pointless, wind or not.

When a group exits, it will move aft of the aircraft (and thus create an angle to the rear) at the same rate regardless of what the wind is doing relative to the ground, so long as the wind speed (and direction for that matter) at the exit altitude is the same as it is below the plane during the observation interval. This is simply because the aircraft and the skydivers outside are in a mass of air that is the same for both objects whether that mass is moving relative to the ground or not. The only way the wind can affect drift angle is if the wind speed (or direction) at the exit altitude is dramatically different than the wind speed at the altitudes the exited jumpers fall through during the observation interval - and that would be exceedingly rare.

Assuming the winds at the exit altitude and observation interval altitudes are the same, the only other relevant element that will change the visual angle vs observation interval is what the exiting group does after exit. Freeflyers - who experience a slower horizontal deceleration after exit relative to their vertical acceleration - will create less aft visual angle for a given observation interval than belly flyers who by comparison slow down horizontally quicker and speed up vertically slower during the same interval.

Using the 45 degree rule will not insure adequate separation at opening because the variable (other than time between exits) that most affects opening separation - the difference in wind speeds at different altitudes - seldom exist with any significance at the altitudes where the 45 degree angle is observed.

If in doubt, see Professor Kallend.

Chuck Akers
D-10855
Houston, TX

[ChrisD 0]

Somebody really needs to start gathering the data that these GPS enabled tracking devices provide.

Some of the freefly java enabled programs have a huge confound in them because they were designed to support a particular point of view...

We have the means at this point we just need a research paradigm that incorporates real data and not supposition...

But what do I know, "I only have one tandem jump."

[FlyingRhenquest 1]

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Somebody really needs to start gathering the data that these GPS enabled tracking devices provide.

Some of the freefly java enabled programs have a huge confound in them because they were designed to support a particular point of view...

We have the means at this point we just need a research paradigm that incorporates real data and not supposition...

I have most of the code in place. I just need to write a state machine to analyze the jumps. I suppose I should get on that...

Reading a GPX or KML file and sucking all the points out isn't particularly hard. I have a factory up on github to do one for GPX, since that's what I happen to be using. You need to pull two or three libraries down in order to use them. It'd be pretty easy to convert to Java or something if you prefer that language.

The only example I have of reading a file in and dumping the points to Google Earth is GPS satellites with 2-day old coordinates from NGA, but I have a class for lat/long/altitudes and the Google Earth code actually requires those.

I'm trying to teach myself how to set things on fire with my mind. Hey... is it hot in here?

[kallend 1,623]

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Somebody really needs to start gathering the data that these GPS enabled tracking devices provide.

Some of the freefly java enabled programs have a huge confound in them because they were designed to support a particular point of view...

We have the means at this point we just need a research paradigm that incorporates real data and not supposition...

Right, assuming that Newton's laws are valid is a HUGE supposition.

...

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

[FlyingRhenquest 1]

Newton's First Law

I'm trying to teach myself how to set things on fire with my mind. Hey... is it hot in here?

[IJskonijn 38]

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Right, assuming that Newton's laws are valid is a HUGE supposition.

Absolutely! The speeds we reach may well be a sizable fraction of the speed of light! *cough*

(Sorry, the physicist in me got out)

[yuri_base 1]

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in my experience as a freeflyer, forward throw is not a minor concern at all. Back in the good old days of freaks out first, I remember opening up on the other side of the flat groups on more than one occasion, including light wind conditions. A head down flyer can continue to have horizontal movement for a very long time.

Some modeling shows that the forward throw (relative to airmass) for a headdown jumper can be 200m (~650ft) greater than that of a belly jumper at jumprun airspeed of ~80kts (and even more at higher airspeeds, obviously). Which essentially "eats up" 5 seconds of exit separation. So if you're a belly jumper exiting after freeflyer (at some DZs this order is still the case), count to 5 first, then start your normal separation count.

[inline Headdown.png]

[inline Belly.png]


The old notion that by 10-12 seconds of freefall the forward throw completely stops as if we're falling in glycerin is incorrect: even at 12s, belly jumper is still moving at ~22mph horizontally, and headdown jumper at whopping 44mph!

Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

[ChrisD 0]

I love the energy and all of the time that has gone into these "modeling" charts, vids, and other graphical displays.

But they all suffer from the same huristical approach,...

even if we just take the gps co-ordinats and plot them on paper by hand, something like drop two jumpers out on the same jump run, collectting data points every .5 seconds and then plot by hand on a graph paper,...

even this gives us more real world data than basic trajectories used in support of any particular individuals view....

Or the Walt Disney type of approach,...which is "One person on the track at a time"???,... Now this becomes a money argument???


think of it this way, since 1970, when this issue really started,...every possible outcome has been viewed and postulated....some of you out there are going to be correct!!!
C

I was at one of the larger dz's last month, and they have a little sign, just before you board the aircraft,...

ON ONE LOAD WE DID IT ONE WAY, AND ON THE NEXT LOAD THEY DID IT ANOTHER WAY...and this is at a dz with a established wing and student program!!!!

You know what this tells me?????

THAT BECAUSE OF THE DERISION AND CONFUSION IN THE SKYDIVING COMMUNITY,...


NO ONE IS LISTENING ANYWAYS!!!


On a side note, the data is going to show nothing that we don't already know,...

the bottom line is going to go back to something I said we should be doing from back in 1973,...

that being "curve the jump run."

But what do I know, "I only have one tandem jump."

[rehmwa 2]

wow, old thread


well, if every group on the load is doing the same discipline, I'd still put a little way between a couple big ways instead of largest to smallest,

for example - two 8-ways and a 2-way

longer net delay for the two big groups that'll be tracking a ton. the 2 way does have the option to track perp to jump run.

Of course, if we calc the correct delay, it's kind of a moot point, so I'm just adding to safety margin. delay between groups and exit order matter so much more than everything else, I hate to bog up on any other factor than the big two

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants