What do you say when people use 45 degree rule or try to get others to use it?

[billvon 2,395]

>Can you post those pictures or video of those exits?

Sure:

http://www.dropzone.com/content/Detailed/628.html

[MisterCrash 0]

What time are all the groups arrowed?
Also what lens was used for the pictures? (because if it's a not a wide angle all the arrows are reasonably close to the 45° line).

I do think that the camera test would achieve better results and accurate numbers when you mount it straigth down from top of the door (marking 0° and 45° in the door). That way you can see if the groups actually gain degrees in relation to time. Now you don't really have a reference around that 45° line marked on the image. Also it might be a good idea to let 2 jumpers use a GPS to actually see what kind of angle is reached.

I like the fact you did research regarding the 45° rule and I'm not at all trying to break your research. I'm only saying if you want to bust the 45° "myth" more facts are needed. Also I dont want to defend the theorie, just think there hasn't been a lot of "accurate" research around it.

I know I can be a pain in the ass and if I'm acting like a douchbag you should let me know. Then I'll stop my ranting.

All speeding past collide and crashing, I'm in paradise.

[rhys 0]

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You'd assume wrong. There are places other than New Zealand that have very strong winds. Case in point -

A few weeks ago I had to spot a load into a very tight area that had a 20kt wind coming out of the west at ground level and a 46 knot wind coming out of the south at 12000 feet.

that is moderate winds bill, everyday occurance in NZ.

i'm talking about 70+ knots at 12k, 23 knots on the ground and Zero ground speed.

this is not uncommon at a buzy tandem factory in NZ, they do push the limits beyond what i would call safe but they do it and they are allowed.

Zero or even slightly negative ground speed will mean you are not gaining horizontal separation, and will have to wait a long time between exits!

We can run in at 65 knots in a cresco, and some pilots do not make adiagonal run in to garantee separation.

46 knot uppers_is_not howling uppers, that is moderate uppers.

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[billvon 2,395]

>Zero or even slightly negative ground speed will mean you are not gaining
>horizontal separation, and will have to wait a long time between exits!

If the winds are the same all the way down - no, you don't! You can use the usual seven seconds exit separation and have just as much separation at opening time as you do in the no-wind case.

The problem arises when winds are different at opening altitude (which they usually are.) If they are, then the separation you get is (ground speed of airplane + winds at opening) * number of seconds between groups.

So if the aircraft is flying into the wind doing 80 knots per its GPS, and the winds at opening altitude are 10 knots from the same direction, and you are waiting 10 seconds between groups, you are going to get (80+10 = 90 kts, which is 153 feet per second) 1530 feet between groups.

If we take your example, and the uppers are 70kts (so zero ground speed) and the winds at opening altitude are the same direction at 30kts, and you wanted to leave 20 seconds between groups, then your separation at opening would be (0+50fps)*20 = 1000 feet separation at exit, which might be enough depending on what you were doing.

If the winds at opening are zero, then you will get NO separation no matter how long you wait, and you have to wait until they open and clear the area before you put another group out. (Or run crosswind or something.)

This is the basic reason that just looking at the group doesn't work. You have to see what they do at opening altitude, because that's where you lose the separation you had at exit. Looking at them for ten seconds after they get out doesn't do anything, because in that time they are always in exactly the same relative wind.

[billvon 2,395]

>What time are all the groups arrowed?

Just as the last group was leaving.

>Also what lens was used for the pictures? (because if it's a not a wide angle all
>the arrows are reasonably close to the 45° line).

The standard lens, which was about equivalent to my XSi's lens at 20mm. I tried a wide angle lens, but then you couldn't see the groups in the resulting pictures.

>I do think that the camera test would achieve better results and accurate
> numbers when you mount it straigth down from top of the door (marking 0° and
>45° in the door).

Problem there is:

1) A regular lens wouldn't be able to capture both 0 and 45 degrees (and slightly beyond) easily

2) A wide angle lens would introduce fisheye distortion, so that 45 degree line couldn't be just drawn across the center as it can be when you're aimed that way.

[kallend 1,623]

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What time are all the groups arrowed?
Also what lens was used for the pictures? (because if it's a not a wide angle all the arrows are reasonably close to the 45° line).

I do think that the camera test would achieve better results and accurate numbers when you mount it straigth down from top of the door (marking 0° and 45° in the door). That way you can see if the groups actually gain degrees in relation to time. Now you don't really have a reference around that 45° line marked on the image. Also it might be a good idea to let 2 jumpers use a GPS to actually see what kind of angle is reached.

I like the fact you did research regarding the 45° rule and I'm not at all trying to break your research. I'm only saying if you want to bust the 45° "myth" more facts are needed. .

Newton's Laws have been very well tested for this type of situation. Isn't that factual enough for you?

...

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

[pilotdave 0]

You could recreate those photographs over and over until you're convinced that the groups never reach 45 degrees, but it still wouldn't help. What if they did reach 45 degrees? What would it tell you about exit separation? If they reached 45 degrees in 3 seconds, would that make 3 seconds a safe separation? What if it took 20 seconds? Would you wait that long between groups?

The real point is that the groups aren't in wildly different locations in the 2 pics (upwind and downwind jump run). There's no reason they would be different. Until they are in freefall long enough to reach very different wind conditions, their motion will be the same relative to the plane (since it's in the same wind) regardless of wind speed or direction. If the group in front of you seemed to shoot back very quickly and reached a 60 degree angle, would that make it safe to jump right behind them with very little delay? Of course not... you're going to be doing the same thing when you exit. What the group in front of you looks like from your perspective has nothing to do with safe exit separation.

Dave

[rhys 0]

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So if the aircraft is flying into the wind doing 80 knots per its GPS, and the winds at opening altitude are 10 knots from the same direction,

A very unlikely situation, winds at 5k would be more like 30+ in those conditions.

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If the winds at opening are zero, then you will get NO separation no matter how long you wait, and you have to wait until they open and clear the area before you put another group out. (Or run crosswind or something.)

You all pass through the same wind speed and have the same windshares, If the plane is stationary on jumprun, 2 people loaded the same would open in the same place regardeless of wind strength and direction changes. When we waited 45 seconds, we waited until the tandem canopy was open until we exited.

At times the pilot would make a diagonal jumprun for safety but most liked being stationary in an aircraft at 12k, 15k jumps are usually not going in those conditions.


remember the plane is essentially stationary, there is no harm in waiting longer then not long enough!

these conditions are not usual at most places but considering the OP is in NZ i wanted to point it out!

i don't use the 45 degree rule as such but I do look to see the separation being achieved!

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[billvon 2,395]

>A very unlikely situation, winds at 5k would be more like 30+ in those conditions.

Agreed; hence the second example.

>You all pass through the same wind speed and have the same windshares, If the
> plane is stationary on jumprun, 2 people loaded the same would open in the
>same place regardeless of wind strength and direction changes.

Correct - but if the wind were the same all the way down you'd still get plenty of separation at opening time if you waited, say, ten seconds. It doesn't matter that you open at the same point over the ground, what matters is how far you are from the next group when they open.

Likewise, if you had the 70kt uppers, 30kt at opening altitude, 20 seconds would be sufficient to give you 1000 feet separation at opening time.

>remember the plane is essentially stationary, there is no harm in waiting
>longer then not long enough!

Definitely agree there!

[brettski74 0]

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I'm only saying if you want to bust the 45° "myth" more facts are needed.

We already have all the facts needed. As Kallend said, Newtonian physics have withstood the test of time well. The law of inertia states that unless acted upon by a non-zero net force, an object at rest will remain at rest and an object in motion with continue to move in a straight line at a constant velocity. Prior to exit, you are travelling with the plane. For simplicity, let's say that the plane is travelling straight and level as the lift provided by the wings is exactly countering the force of gravity and the thrust from the prop/s is exactly countering the drag experienced by the plane as it passes through the air. Let's also say you're floating on the outside of the plane or hanging on the strut of a cessna. You let go of the plane. The plane continues on jump run, flying straight and level at constant speed.

The path that your body moves along as it moves away from the airplane will be the net result your initial velocity with respect to the observer and the cumulative effect of the forces which act upon your body and of those which act upon the plane.

We've already stated that the plane is not changing direction or speed. From the law of inertia we know that the net force acting on the plane is zero.

Up until the time that you let go of the plane, you were traveling with the plane, not moving towards it or away from it, so for an observer in the plane your initial velocity is also zero.

What forces are acting on your body at this time? What determines the magnitude and direction of those forces? If the upper winds are to have an effect on the path your body takes as it moves away from the plane, as observed from the plane, one of two things must be true. Either there is some force acting upon your body that is dependent on the upper winds, or the law of inertia is wrong. Which is it?

[rhys 0]

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Correct - but if the wind were the same all the way down you'd still get plenty of separation at opening time if you waited, say, ten seconds. It doesn't matter that you open at the same point over the ground, what matters is how far you are from the next group when they open.

And linetwists on a icarus main(open in full drive) flying up jumprun at the same airspeed as the windstrength?

An unlikely scenario, yes, but I have seen it a few times.

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[billvon 2,395]

>And linetwists on a icarus main(open in full drive) flying up jumprun at
>the same airspeed as the windstrength?

. . . is as likely as an Icarus main open in full drive flying DOWN jumprun in no wind conditions. (Which, if it's a Safire 189, isn't a big deal - but can be a bigger deal if it's a Crossfire 89.)

You have to choose your exit separation distances based on canopy speeds, breakoff distances and group sizes. These issues apply whether the winds are zero or howling. THEN you add on extra time if needed for wind-reduced separation.

[rhys 0]

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. . . is as likely as an Icarus main open in full drive flying DOWN jumprun in no wind conditions. (Which, if it's a Safire 189, isn't a big deal - but can be a bigger deal if it's a Crossfire 89.)

You have to choose your exit separation distances based on canopy speeds, breakoff distances and group sizes. These issues apply whether the winds are zero or howling. THEN you add on extra time if needed for wind-reduced separation.

You failed to see the point Bill, in the scenario I described above, you would remain stationary in your opening position and using your (7 second) model, would be hit by the next guy in 7 seconds and potentially will be in a quadrupal tandem fatality scenario.

The idea is to leave adequte separation, not 'just enough' separation. If the cool guys are booting you in you rig to get out, so they can do their 430degree swoop, but you are still not sure. Check you pins again and fuck em, they can go around.

It is not a race and we shouldn't be pushed into doing things that don't make sence just because they do in someone elses mind.

If there is not much wind at all there is no problem, but when there is alot we should be on the more consevative side than, taking the 'ahh 7 seconds is enough' attitude.

This website is well known for bad advice from under experienced post whores, when you explain such scenarios, you should allow for the fact that not everyone has the same level of understanding than you and they may just take some sarcastuc comment seriously.

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[mark 102]

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This website is well known for bad advice from under experienced post whores. When you explain such scenarios, you should allow for the fact that not everyone has the same level of understanding as you and they may just take some sarcastic comment seriously.

Irony.

[strop45 0]

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If your DZSO or CSO requests that you use this rule, I suggest you do so. although 45 degrees might never happen as explained in various hypothesies, a good shift in the position of the previous group towards the tail indicates adequate separation is being achieved.

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It is not a race and we shouldn't be pushed into doing things that don't make sence just because they do in someone elses mind.

+1 for the irony

Or has your position changed? In one post you argue that people should use a rule which doesn't work(i.e. make sense) and now you argue the exact opposite.

WTF ????

The difference between stupidity and genius is that genius has its limits." -- Albert Einstein

[billvon 2,395]

> in the scenario I described above, you would remain stationary in your
> opening position and using your (7 second) model, would be hit by the
>next guy in 7 seconds and potentially will be in a quadrupal tandem
>fatality scenario.

No, he wouldn't - unless the winds at opening altitude are zero. Using some very basic math, and the variables in your example:

70kts at altitude, groundspeed is zero
Surface winds are 23kts from the same direction
Winds at opening altitude (5000 feet) are 40kts in the same direction (an assumption, feel free to give me a different number if you know it)

7 seconds = 472 feet separation

Now, that may not be enough - so 14 seconds may be a better delay, giving you 944 feet separation. Or if you prefer wait until the tandem has descended to a safe altitude (say, 2000 feet) before you put the next one out. That's even safer.

>It is not a race and we shouldn't be pushed into doing things that don't
>make sence just because they do in someone elses mind.

Agreed! We should understand what's actually happening, and not use some "45 degree rule" nonsense that makes no physical sense (other than in people's imaginations.)

>but when there is alot we should be on the more consevative side
>than, taking the 'ahh 7 seconds is enough' attitude.

I agree. And if you would rather wait 14 seconds, or 30 seconds, or even have a separate pass for each jumper, then by all means, do so.

[JohnMitchell 14]

I still want to know what you advocate teaching all these new people about exit separation. Is it well grounded in physics or just some mumbo-jumbo?

[rhys 0]

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+1 for the irony

Or has your position changed? In one post you argue that people should use a rule which doesn't work(i.e. make sense) and now you argue the exact opposite.

WTF ????

No i don't think the 45 degree rule is exactly correct, but I do think that looking out and making sure horizontal separation is being achieved is the best thing to do.

This '7 seconds is adequate for everything' hypothesis is asking for real trouble in a situation with 'very _strong_uppers'.

I don't believe either rule is correct but i believe the 45 degree rule is at least some way close to seeing if horizontal separtaion is achieved.

Counting 7 seconds and bailing out with 80 knot uppers is plain old stupid!

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[rhys 0]

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I still want to know what you advocate teaching all these new people about exit separation. Is it well grounded in physics or just some mumbo-jumbo?

Read above,

I have, for the most part of my career, been given the winds at various altitudes from the very beginning of my skydivng career.

Once I travelled abroad I was shocked to find that not only did the dropzones I went to not obtain the winds aloft, but they couldn't have cared less about them!

After a while I realised that unless you live at or around 45 degrees, the chances of very_strong_uppers are much much less.

I have however experienced 60 knot uppers at around 3 degrees South in Tanzania, and 16 degrees south in Australia, never above 60 knots in my experience though, and not very often.

These type of winds are commonplace where I learned and began my career. We would continue to jump with up to 80 knot uppers as long as the ground wind is clean and not above 23 knots!

So to answer your question,

I advocate listening to your DZSO, (or S&TA in america), if you don't feel comfortable with thier decision...

...Don't jump!

Never take advice from these forums and take it literally.

Just because something works somwhere for someone else, does not mean it works for everyone, everywhere.

Local knowledge and experience will never be rivaled by hearsay on the internet.

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[rehmwa 2]

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No i don't think the 45 degree rule is exactly correct, but I do think that looking out and making sure horizontal separation is being achieved is the best thing to do.

45 isn't 'exactly' correct, or even a little bit correct. But I totally agree with looking out and checking horizontal separation - by looking at the apparent ground speed (which can be done on jump run preferably). Looking at the other group is nonsense as they'll follow nearly the same path no matter what the winds are doing since the first part of the dive and the aircraft itself are always in the same relative airmass - the only affect on these 'relative' perspectives I can think of is if the pilot would DRAMATICALLY change the jump run speed - I wonder how much though before we'd be confident of seeing it with just the naked eye out of a big door

This '7 seconds is adequate for everything' hypothesis is asking for real trouble in a situation with 'very _strong_uppers'.

strawman here - I agree that method is nonsense also, but I don't think that's what those opposing the 45 degree falsehood are advocating - most are advocating understanding the wind patterns (speed and direction of all the layers) and selecting an appropriate delay based on the what "really" happens between groups

I don't believe either rule is correct but i believe the 45 degree rule is at least some way close to seeing if horizontal separtaion is achieved.

nonsense - as long as you're looking at the group in freefall instead of the ground progress, you don't learn anything other than forcing an arbitrary delay (something like 7 seconds) -

typical days have lowers and uppers are "normally" in the same direction with the uppers faster - on those days with an upwind jump run, the plane's ground speed should define separation delay - fast ground speed is smaller delays vs low groundspeed. It's not hard to do. Days with different wind behaviors need to be done differently

Counting 7 seconds and bailing out with 80 knot uppers is plain old stupid!

ABSOLUTELY - good thing people aren't advocating a blanket 7 second delay falsehood

I'm fascinated how people are trying their best to turn this thread into a debate over which 2 completely wrong delay criteria is better. I'd give them both a pass.

edit: to your point - I wonder if watching the other groups progress "against the background of the suface" if one could estimate an adequate gage of the relative separation would provide. Seems to be a tricky visual, though compared to just knowing the relative difference between uppers and lowers etc. If this is your point, (rather than the 45 degree sweep 'relative to the aircraft' which everybody else using the concept (wrongly) as, then I totally understand your position). If the plane isn't moving fast (high uppers), then the bodies will pass the background differently (the only visual indication would be the constant relative separation of the jumpers from the plane (same every time) than if the plane was moving (low uppers) and the visual would be the same constant separation of the jumpers vs plane added(subtraacted) to the ground speed visual. If you think on it, the results would be backwards, since on a low wind day, (I think) those two perspectives would be in opposite directions - thus encouraging a shorter delay on a high wind day - mistake. But I'm not sure.

...
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

[rehmwa 2]

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Local knowledge and experience will never be rivaled by hearsay on the internet.

however, the laws of physics will always win out over false local knowledge, badly applied experience, and just poor thinking and planning skills.

(In the end, I think we're all advocating the same thing, even if it's taking a bad theory and then 'tweaking' it until we actually do the right thing despite the poor theory. So whatever rationalization your DZ would use to force a long delay on days with very windy uppers - I'm glad at the results)

aside - I really like the days when the uppers are screaming and the ground winds are normal. You can pretty much park the plane at altitude and take huge delays (sufficient for the previous group to open and go away) - it makes the freeflyers nervous to wait so long - it makes the tandems pretty happy, because they can do everything really calm.

I learned that lesson chasing a tandem once on a higher uppers day. I climbed out after a few seconds from the last 'fun' group. The TM I was chasing sat on the bench for about another 50 seconds and just smiled and laughed at me hanging on the camera step until he was ready to get out. we had no issues getting back - and even less traffic than usual of course.

...
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

[pilotdave 0]

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This '7 seconds is adequate for everything' hypothesis is asking for real trouble in a situation with 'very _strong_uppers'.

Who is arguing that the correct exit separation is 7 seconds? Some people are arguing that TIME can be used to determine exit separation (if you know the winds at exit and opening). But nobody is suggesting that 7 seconds is always correct. But what is NEVER correct is choosing exit separation by watching the previous group to see what angle they make in relation to the plane. There is no correct angle.

Dave

[kallend 1,623]

The known laws of physics do NOT support your position.

Suggest you download and read this:

www.iit.edu/~ugcol/separation.zip

...

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

[JohnMitchell 14]

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So to answer your question,

I advocate listening to your DZSO, (or S&TA in america), if you don't feel comfortable with thier decision...

...Don't jump!

Never take advice from these forums and take it literally.

Just because something works somwhere for someone else, does not mean it works for everyone, everywhere.

Local knowledge and experience will never be rivaled by hearsay on the internet.

Ask the local DZO? That's your lesson? Sorry, but why not teach people how to judge jump run spacing themselves so they can do it safely without bothering the DZO every damn jump? Like setting an AAD, gear checking, and spotting, jump run spacing is a subject that needs to be taught, and taught correctly. I was expecting a great lesson plan from you. I"m rather disappointed.

We teach to use more spacing between larger groups, more time on days with high winds aloft.

Exit order:Boards, belly, freefly, aff, tandems, trackers, wingsuits.

All tracking and wingsuiting to be done away from the jumprun line.

On the plane, if you don't know the skill level of the person following you, take a moment to ask what kind of jump they are doing and what exit spacing they will give you. If you are not happy with the answer, advise them what time interval you feel would be more appropriate.

If you open short of the DZ, wait for the next group to open before you head back to the DZ.

If you feel there was not enough spacing for safety, talk to the other group and modify what you are doing.

Once again, in longitudinal separation rules, time is a very good tool to use to separate both airliners and skydivers. I see it work all the time. You just have to know what you are doing.

[rehmwa 2]

Our pilot gives us the ground speed on jump run - also the surface winds if they changed - he also plays Flight of the Valkyrie on jump run

that's about all most of us need to decide on delays between groups - especially the music

We like our pilot

...
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