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kallend

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

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rehmwa

***> A jumper that has just exited is in the same air mass as the aircraft, and their trajectory will look exactly the same in 0 wind, 100 mph headwind, 100 mph tailwind (even if they *do* reach 45 degrees at some point).

The necessity to compensate for the wind has been discussed in so many posts and articles - "over 9000" - that I didn't mention it on purpose. I'm making a point that haven't seen mentioned before.



Brian's point is precisely correct. the point being

"A jumper that has just exited is in the same air mass as the aircraft, and their trajectory will look exactly the same in 0 wind, 100 mph headwind, 100 mph tailwind"

^^^ THIS is the only thing that matters - if you are in the plane and watching the jumpers, it's a totally useless observation. Look at your finger, look at the deck of the plane, or look at the pilot is exactly equivalent the zero content info you might imagine you are getting.
...


That exact point has been made before. By me and Billvon, and I'm sure others too.
...

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

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kallend

***Should make Bill Von's video a sticky !!!



It's available on my website, link posted previously.

And for anyone who doesn't feel like looking through 18 pages to find that link, there's also a link on his profile page here on DizzyDot.
"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

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LouDiamond

Quote

but I'd love to have the "formula" in my head.




Then print this out and tape it to your helmet;) or better yet, tape it right beside the lights by the door. In order for this to work the pilot must give you the groundspeed while on jumprun.



As has been amply demonstrated, ground speed in and of itself has precisely nothing to do with freefall separation.

One can have zero ground speed (jumping from a tethered balloon) and have excellent freefall separation, and one can have great ground speed (jumping from a free balloon) and have ZERO freefall separation.

In practice this not as egregious a misconception as is the "45 degree rule," but it is still wrong.


BSBD,

Winsor

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So, I was thinking, would it be possible to have some easy to use visual aid in determining the exit separation that would automagically account for ground speed? And came up with this simple idea.

We need to achieve a certain amount of separation over the ground, not the air, as was discussed to death in the previous over 9000 posts (the effect of the wind at opening altitude, let's face it, is relatively minor in this discussion; all jumpers should be flying away from the plane/current deployment area after opening anyway). Let's say, we need 1000ft (300m) over the ground. So, we simply wait until the plane travels 1000ft over the ground, because the trajectories of jumpers with the same terminal speed are translationally parallel to each other and thus are offset by the distance the plane covered over the ground; but how can we gauge this distance? Magic shoes to the rescue! Here's a photo from one of the recent articles on the front page:

[inline LakeBalaton.jpg]

Jumpers look down from the top of the door, and for a given exit altitude their shoes provide a certain scale on the ground. Here, the shoe width corresponds to about 1000ft on the ground, just what we need.

[inline MagicShoe.jpg]

(Indeed, if the exit altitude is about 13500ft, 1000ft on the ground is 1/13.5th of it, which is the same proportion as a 11cm-wide shoe as viewed from 1.5m (5ft) height.

So, when the previous jumper exits, you stick your magic shoe like on the pic, hold your head steady near the top of the door (e.g. lean it against your hands holding the handlebar) and notice a feature on the ground on the forward side of the shoe. Wait until this feature emerges on the aft side of the shoe. That's it, you have about 1000ft/300m of separation, you're good to go!

What if you're a student and there is a freeflyer exiting before you? For a belly jumper (120mph terminal speed) exiting the aircraft flying at airspeed 100mph, the forward throw is about 1300ft; for a headdown at 180mph terminal speed, the throw is about 2000ft, as can be easily calculated in Wingsuit Studio:

[inline ExitSeparation.png]

So, you need extra 700ft of exit separation, so you need to wait almost double the width of the shoe.

Or, instead of using a shoe for reference, more permanent solution is to tape some bright markers to the doorstep at appropriate distance.

Here you go, a simple and visual method for exit separation that automagically accounts for ground speed. Of course, for experienced jumpers it's should [usually] be enough to just rely on the sense of ground speed and time and use their experience, or use a separation chart, but this method can be a good educational tool for students as it emphasizes the importance of ground speed, amount of separation, various amounts of throw for different types of jumping, and gives them an easy tool to gauge the separation, the tool they always have on them. The shoes.

It's magic, pure fucking magic! ;)
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>the effect of the wind at opening altitude, let's face it, is relatively minor in this
>discussion; all jumpers should be flying away from the plane/current deployment
>area after opening anyway.

All jumpers should be flying away from the center of the formation. They should NOT be trying to cluster to one side or the other of the jump run line. During breakoff by far the biggest risk (for any group larger than 2) is the other jumpers in your formation. That risk can be mitigated by good tracks away from the center of the formation.

>So, we simply wait until the plane travels 1000ft over the ground

That USUALLY works. As long as the jumpers understand the conditions under which it doesn't, that can help.

Since foot sizes vary, I usually just use ground features. 3000 foot runway? Just divide it into 3 and use that as a reference.

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billvon

All jumpers should be flying away from the center of the formation.



To clarify, by "flying away" I meant under canopy, not tracking. And yes, extra separation should always be given to groups, the bigger the more - at least, by typical radius of their "track umbrella".
Android+Wear/iOS/Windows apps:
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iOS only: L/D Magic
Windows only: WS Studio

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>To clarify, by "flying away" I meant under canopy, not tracking.

I meant both. A great many collisions happen shortly after opening. As soon as you open you should be facing the direction you were tracking, and if not, you should get on rears to make sure you are continuing to fly in that line.

After slider is collapsed, camera turned off, swoop cords removed (or whatever other stuff you fuss with is taken care of) and brakes unstowed - then it's generally safe to start turning away. By that time you've generally achieved a safe separation.

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billvon

>To clarify, by "flying away" I meant under canopy, not tracking.

I meant both. A great many collisions happen shortly after opening. As soon as you open you should be facing the direction you were tracking, and if not, you should get on rears to make sure you are continuing to fly in that line.

After slider is collapsed, camera turned off, swoop cords removed (or whatever other stuff you fuss with is taken care of) and brakes unstowed - then it's generally safe to start turning away. By that time you've generally achieved a safe separation.



I really don't think this is a good idea. If you had to track up or down jumprun clear the jumprun.
Secondly waiting with a turn until housekeeping is done would lead to a great deal of outlandings, at least for me. I have about a minute after opening until I land, normal housekeeping takes me about 15-20 sec depending on what I was doing. So now I'm at 500m, already past my first setup point, somewhere out of nowhere and with no chance to reach the DZ because I was flying downwind the whole time.

Think, look, turn avoids collisions. Not stubbornly flying away from an imaginary center.

Or did I missunderstand what you were talking about?

Anyway, thanks yuri!! Great post, will try it out and see, how my students get along with it:)
-------------------------------------------------------

To absent friends

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I think that whenever we talk about 'best practices' or 'standard procedures' they apply to a typical jumper. The majority of people who are in the middle of a bell curve.

Someone jumping an extremely loaded, ultra high performance canopy with all the removable bells and whistles is at the extreme end of that normal distribution curve and many of those standards won't apply to them. That's one reason why people shouldn't jump gear like that until they're suitably experienced - because the SOPs which have kept them safe don't necessarily apply any more and they need to have the experience to make safe alterations to them.

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You're asking the same people who have trouble comprehending the shortcomings of the visual cues of the 45 degree rule to be able to gauge another visual cue right in the middle of their climbout. The period between groups takes into account the climbout so somehow this person with their shoe in the door needs to estimate not only their distance across the ground but also be able to gauge the amount of time to when their group is set in the door.

It's a good thought but not realistic unless for some reason there is a very large quantity of time between groups and this spotter can do rule of thumb mid-air mental telemetry.
"I encourage all awesome dangerous behavior." - Jeffro Fincher

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>Secondly waiting with a turn until housekeeping is done would lead to a great deal of outlandings, at
>least for me.

Well, outlandings are much, much better than canopy collisions.

> I have about a minute after opening until I land, normal housekeeping takes me about 15-20 sec
>depending on what I was doing.

OK. When I am doing FS It takes me about 3. 1 to kill slider, 1 to deal with booties/faceplate and 1 to verify that the brakes are clear. Fortunately I don't have to look at any of that stuff to do it, so I can keep my eyes open as I am flying away from the center. If I have a bizarre opening (a 180 or something) it might take me another second or so to riser turn away from the center.

After opening on a formation you MUST fly away from the center. You are generally not going to be the first to open, and that lighter/slower tracker may be tracking just to your left - or the guy to your right may open facing you. This has to continue until everyone is open and has their canopy under control. Call it 5 seconds on your average 4 to 8 way.

If you are taking 15-20 seconds to do your housekeeping after you open, and you are landing in 60 seconds, then you're doing an extraordinary skydive (very high loadings, complex RDS etc) and you shouldn't be doing FS with a bunch of other people unless they are making specific provisions to deal with your issues after opening.

>Think, look, turn avoids collisions.

Will you see the guy above you, still freefalling, who is going to hit you in another 2 seconds?

The first five seconds after opening is the second most dangerous time under canopy. (The first is the final turn to landing.) Right after opening you have the people in your group opening around you. Some are in freefall, some have already opened, some are in the process of opening. You have the next group about to open. If everything went right, they will be opening in 7-10 seconds about 1000 feet from you. If not, they will be opening about 3 seconds after you in your airspace. They can see you; you can't see them. Being predictable, and flying away from everyone else, is going to be your best bet.

Also, opening facing away from the formation means that everyone is doing the same thing. That guy who is facing you and trying to release his brakes, not looking at you? He's going to turn out, perhaps even before he sees you. Best if you do the same, so you end up flying parallel - and then keep going that way until that risky period is over.

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Of course, for experienced jumpers it should [usually] be enough to just rely on the sense of ground speed and time and use their experience, or use a separation chart, but this method can be a good educational tool for students



To reiterate this point: *of course*, in light winds and for experienced jumpers/groups, it would be ridiculous if somebody was standing in the door staring at their shoe. The 6s separation for solo belly and up for bigger groups, is simple enough to feel intuitively, 6 seconds is a time interval that is naturally consumed by pre-exit activities such as looking at the jumper exiting before you, waiting a bit and taking your position in the door. As long as you don't rush, 6s passes just like that.

But in strong winds, this internal feel of timing fails. If the uppers are 80mph and the 100mph plane now travels at 20mph ground speed, the separation time must be increased 5x! So, it must be 30 seconds for solo belly and something like a minute for small groups, etc. Now, I've never ever actually seen somebody waiting for 30s, let alone a minute on windy days. Yes, jumpers more or less understand that they need to wait more, but a few realize how dramatic the increase must be.

In such situations, SEX (naturally, an abbreviation for Shoe EXit separation method :)) gives a solid tool to insure proper separation. And you get the time and justification to stare at your shoe as long as needed.

But besides this, SEX can be a rule of thumb (or rule of shoe) for students and low-experience jumpers. One of the first posts in this thread was,

Quote

Understanding and accepting that the "45 degree rule" does not work, lets talk about what does.

I've heard a lot of things from other jumpers and instructors. One of them was the 45 degree rule. Another is to wait as many seconds as half of the upper wind strength. 40mph uppers? Wait 20 seconds. Another is to wait until it just "looks like there's enough" separation, but as a tremendously inexperienced jumper, I can't make that judgment.

So how should I judge separation? I still ask more experienced jumpers pretty much every time, trust their judgment and try to learn from it, but I'd love to have the "formula" in my head.



Jumpers WANT rules of thumb. 45 degree rule is dead, something should be invented to replace it. SEX is the answer. Easy, always available, and automagically works in any wind.

Shoes... shoes everywhere! It was the clown shoes that instigated the Wingsuit Theory. 10 years later, they help jumpers avoid collisions. It's magic, pure fucking magic! :)

[inline ShoesEverywhere.jpg]
Android+Wear/iOS/Windows apps:
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iOS only: L/D Magic
Windows only: WS Studio

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If the uppers are 80mph and the 100mph plane now travels at 20mph ground speed, the separation time must be increased 5x! So, it must be 30 seconds for solo belly



Here's even more dramatic and less obvious example: same 80mph uppers, but the pilot changed from the previous load, this pilot likes to trim the plane to fly at 90mph TAS on jump run. The ground speed is now only 10mph, so a solo belly must wait... a whole MINUTE to achieve the same amount separation that on a light-wind day takes just 6 seconds!

Have anyone actually seen a jumper waiting a whole minute in strong winds? I think, most jumpers that think of themselves as safe and experienced, will say, "Winds are strong, the plane is barely moving. I'll give a generous FIFTEEN seconds of separation!" These 15s correspond to 1.5s in light wind. This safe, generous jumper is going to fall almost on top of the previous one! Add a bit of backsliding, and we have a collision.

This mistake won't happen if the Rule of Shoe is used. How many people can shoes save over the years?

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

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I will say that I've been in a plane a number of times where the uppers were honking and when jumpers started to give 10 second plus delays before climbout they started getting shouted at by people in the front of the plane.

Pissed me right off. >:(

Sit down & shut the fuck up. You have no idea what's going on in the door if you're not there.

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yuri_base

We need to achieve a certain amount of separation over the ground, not the air, as was discussed to death in the previous over 9000 posts (the effect of the wind at opening altitude, let's face it, is relatively minor in this discussion; all jumpers should be flying away from the plane/current deployment area after opening anyway).



Not exactly sure what you mean by needing separation "over the ground, not the air". The only reference that matters is the distance between the jumpers or groups of jumpers and that is a straight line measurement without respect to anything else.

Also, your comment that the winds at opening altitude are "relatively minor in this discussion" is understating this aspect of the calculation. The difference between the wind speed on jump and the wind speed at deployment altitude is exactly why we have to have different delays between exits and the wind at deployment altitude often matters a lot. For example, just recently in Houston the winds on the ground were acceptable for jumping (about 15-19) but at 3,000 feet the winds were over 35 mph, yet at altitude they were only about 15 mph. That changed the calculation drastically versus a typical day.

Finally, your assertion that "all jumpers should be flying away from the plane/current deployment area after opening anyway" is not correct. At many DZ's operating large aircraft with multiple groups often place the opening point of the first group or groups downwind of the landing area, requiring those jumpers to fly up the wind line toward groups that exit after them. As an FS organizer my groups are often the first to exit and we discuss this when conditions warrant dropping us short.
Chuck Akers
D-10855
Houston, TX

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Sure, nothing is perfect. But NO RUSH (which, of course, is an abbreviation for New & awesOme RU of SHoe) method is a Good Enough (GE) ballpark estimate that should work in 99.9% of cases in type of conditions student and low experience jumpers usually jump (e.g. not flying backwards under canopy in 35 mph winds at opening altitudes).

45 degree rule must die. And the only way to make it die is not to repeat how wrong it is (this only perpetuates it), but to replace it with something simple, intuitive, easy to remember and perform, GE rule. Such as NO RUSH. Students need quick formulas. NO RUSH is such a formula. Later, as they become more experienced and learn more, they should be aware of the effects of the winds through the whole freefall. But when they're just starting, they should not be overwhelmed with a Ph.D.-level science of exit separation and bring a laptop running Java freefall simulation to the plane.

It's similar to the Accuracy Trick method. Does Accuracy Trick work in all situations? No. If the winds change or there are shear layers, you're not going to land where starfield effect is zooming in from. You need to try to predict the situation and also give yourself a margin of unpredictability. But it's GE, and is taught and used by all jumpers.

We cannot know or predict all variables, such as full wind profile from 0 to 13500 ft. The numbers from the weather service may not accurately reflect the reality at this moment. There could be some freak wind jet layer happening right now that will magically put the whole load on top of each other. So, the first approximation is to use the information we know with 146% certainty, and that is the ground speed. The pilot knows it, and jumpers, too, can measure it with GPS/phones. But this is the "Excel spreadsheet" method - measure the speed, look up the table. NO RUSH makes this unnecessary, it automagically performs the whole routine in one easy, pun intended, step.

45 degree rule is dead. Killed by a shoe. Stay safe out there and remember NO RUSH! ;)

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

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yuri_base

If the uppers are 80mph and the 100mph plane now travels at 20mph ground speed, the separation time must be increased 5x!



You are missing the most basic point:
Wind means nothing.
Only the difference between uppers and lowers will influence the distance between jumpers at opening.

In other words:
If the wind is equally strong at all altitudes, from exit until opening, the distance between two groups will be exactly the same as when the winds are zero at all altitudes.

Therefore using groundspeed as a reference is just as valid as using the faulty "45 degree rule".

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yuri_base

.. Later, as they become more experienced and learn more, they should be aware of the effects of the winds through the whole freefall. But when they're just starting, they should not be overwhelmed with a Ph.D.-level science of exit separation and bring a laptop running Java freefall simulation to the plane.



None of this requires PhD level science or a laptop, and I'm not suggesting anyone needs to dissect the wind conditions in great detail from top to bottom. What is important is for all jumpers to understand that the critical comparison for separation upon opening (discipline differences not withstanding) is the variance in wind conditions between exit and deployment.

Years ago jumpers started out on round parachutes because we believed squares would be impossible for them to steer and land without carnage. We put them on single operation cutaway/reserve deployment systems because we believed a two-handle system was overly complicated for them. We made them use main ripcords because we believed using throwouts would be too much for them deal with. We were wrong on all counts.

There is no reason young jumpers can't learn to incorporate the winds at deployment altitude when calculating exit separation. We have learned from experience that skydivers learn whatever we teach them. Adding one data point into the calculation is not overly complicated for anyone with enough intellect to skydive.
Chuck Akers
D-10855
Houston, TX

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kallend


Wasn't all this beaten to death years ago?



And rightly so. :S:S

If I have no movement over the ground (STRONG uppers) a ball I throw out the door will land on the exact same spot no matter how long I wait (assuming the differences in wind speed from exit to the ground don't change significantly), even an hour won't change anything
By his logic the ball would land in another state if I wait that long, although my spot over the ground hasn't changed.

Simplified:
Ground speed matters, nothing else!

Go troll somewhere else :P
-------------------------------------------------------

To absent friends

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