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

[Divalent 89]

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Which, in a nutshell, is why it doesn't work.

0ft/sec x 7 sec = 0 ft: all the watermelons land on each other.

I must be missing something here, because he clearly was advocating using ground speed to determine exit separation (the "7 sec" was his example), which is the right way to do it, yes?

[by that I mean, of course, you have to rearrange the equation to be:
X = Z / Y
Where X is exit interval time in secs, Z is desired separation distance in ft, and Y is the ground speed of the plane in ft/sec]

[billvon 2,380]

>I must be missing something here, because he clearly was advocating using ground
>speed to determine exit separation (the "7 sec" was his example), which is the right
>way to do it, yes?

Yes, sorry, should have said "which in a nutshell is why the 45 degree thing doesn't work."

>Where X is exit interval time in secs, Z is desired separation distance in ft, and Y
>is the ground speed of the plane in ft/sec

I think the full form is distance = time between groups x (groundspeed of airplane + winds at opening altitude)

Speeds are in feet per second, time is in seconds, airplane is assumed to be flying into the wind, winds all the way down are assumed to be roughly the same direction.

[NWPoul 1]

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You don't seem to have the concept of separation.
How much separation do you get if you drop jumpers with 7 seconds of delay, the plane flies with 80kts into the wind and the wind is 10, 40, 70 kts?

Horizontal Separation at the moment of opening? It should be the same for all the cases

Why drink and drive, if you can smoke and fly?

[FastRon 0]

Bill- I'm pretty sure that's what I meant. Airspeed plus or minus the vector of winds aloft parallel to that airspeed= the ground speed along jump run? If that is zero then everything ends up on top of everything else? If it's not zero then isn't there SOME built in separation by allowing whatever time between groups is appropriate? (I only suggested 7 seconds becasue someone else cited it.)
I am sort of aware we usually don't try to open at ground level...
I personally prefered about 2500 feet or so. :-)

[stayhigh 2]

45 degree does not work.

but I tell my students. if there is no information available, and pilot just tells you fuck off, when you ask him for the upper wind. only then apply 45 degree rule because it is better than none.

Bernie Sanders for President 2016

[pchapman 261]

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only then apply 45 degree rule because it is better than none.

But I thought that video tests*, and analysis, show that jumpers may or may not pass through the 45 degree line, or hover around it, depending on aircraft speed.

In typical circumstances, a jumper will go out the door and be at a relatively steep angle (relative to a line to the horizon), get to a shallower angle as they get decelerated horizontally but haven't picked up much vertical speed, and later in the fall get to a steeper angle again when they're dropping vertically faster than the typical jump aircraft is travelling horizontally.

The angle has to do with the jumper's body position to some degree (low or high drag), and largely to do with the aircraft's speed. But unless there is wind shear in the altitudes not far below the plane where the jumpers are being watched, the angle has nothing at all to do with upper vs. lower winds. Small amounts of wind shear will have only a small effect on angle.

Aircraft speed will affect it, but then one can use easier to measure time rather than trying to discern 45 degrees vs 50 degrees or the like.

So instead of the 45 degree rule, you'd be better served by just using a 7-10 second rule -- OK in a lot of cases but not in some.

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*Von Novak's classic video test results once again:
http://www.dropzone.com/content/Detailed/628.html

[JohnMitchell 14]

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Aircraft speed will affect it, but then one can use easier to measure time rather than trying to discern 45 degrees vs 50 degrees or the like.

So instead of the 45 degree rule, you'd be better served by just using a 7-10 second rule -- OK in a lot of cases but not in some.


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*Von Novak's classic video test results once again:
http://www.dropzone.com/content/Detailed/628.html

I've got a pretty good eye for angles, but a lot of people couldn't tell 45 degrees if it bit them in the ass. Besides, it's meaningless. Use time to separate the groups.

[billvon 2,380]

>only then apply 45 degree rule because it is better than none.

I agree. But that's because if you used it you would never get out. (Which is inconvenient but does ensure adequate separation.) Most groups never cross the 45 degree line.

[piisfish 135]

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> But that's because if you used it you would never get out. (Which is inconvenient but does ensure adequate separation.) Most groups never cross the 45 degree line.

just ask the pilot for MORE speed

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[kallend 1,621]

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45 degree does not work.

but I tell my students. if there is no information available, and pilot just tells you fuck off, when you ask him for the upper wind. only then apply 45 degree rule because it is better than none.

There are an infinite number of incorrect ways to ensure separation. Why choose that one?

...

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

[popsjumper 2]

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> If we dropped say 4 same sized/weight watermelons 7 seconds apart, shouldn't they
>impact in a rough line parallel jump run about aircraft ground speed (in ft./sec.) times
>7 seconds apart?

They will impact about 7 seconds apart.

Now take the case where the wind is 70kts at altitude and the plane is flying straight into it. Your groundspeed is zero. Winds on the ground are light and variable. Now you do the experiment again. How far apart will the watermelons be when they hit the ground?

You should have used an AN-2 in nearly any wind conditions.


Our separation was....when the guy before you opens and flies out from under you, then you can go.


Or, AS Pissfish said....tell the pilot to crank it up to 120 knots and then calculate.

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

[Southern_Man 0]

If the pilot, for some strange reason, won't give you ground speed or headwind, stick your head outside the airplane and jump when you've moved .2 over the ground. It is not hard.

"What if there were no hypothetical questions?"

[popsjumper 2]

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only then apply 45 degree rule because it is better than none.

But I thought that video tests*, and analysis, show that jumpers may or may not pass through the 45 degree line, or hover around it, depending on aircraft speed.

Which is why telling the group behind you to use the 45-degree rule gives you PLENTY of separation.




(just joking 45-degree rule proponents...just joking.)

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

[DBCOOPER 1]

The solution is to change the name to the 45 degree myth...

Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

[kallend 1,621]

At an event last week I was talking to a recently USPA certified AFF instructor (certified at well known California DZ) who said he was told by the AFF examiner to teach his students the "45 degree rule".

So I'll resurrect this thread which, like a zombie, refuses to die.

...

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

[Napalm_C 0]

I was shocked though over the summer when we visited one of the biggest and most well known DZs in Southern Europe that even there they insisted on the 45 degree rule. As a visiting jumper it was not my place to question this approach but I made sure to ask at least 4 different people there and each and every one insisted on the 45 degree rule.

On one lift, our group (3 way flat) left 14s after the group before us (4 way flat) and on breakoff I literally had to pull 2s into my breakoff track because I could see a canopy open just off to the side. 45 degree rule doesn't work but it is still being widely used and TAUGHT...

Personally I'd like your permission to John to show your presentation at my local DZ, it won't be easy though to convince people with triple my jump numbers and years in sport that this concept needs to be eradicated.

P.s. Typed this on mobile so apologies for typos

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[kallend 1,621]

Napalm_C

I was shocked though over the summer when we visited one of the biggest and most well known DZs in Southern Europe that even there they insisted on the 45 degree rule. As a visiting jumper it was not my place to question this approach but I made sure to ask at least 4 different people there and each and every one insisted on the 45 degree rule.

On one lift, our group (3 way flat) left 14s after the group before us (4 way flat) and on breakoff I literally had to pull 2s into my breakoff track because I could see a canopy open just off to the side. 45 degree rule doesn't work but it is still being widely used and TAUGHT...

Personally I'd like your permission to John to show your presentation at my local DZ, it won't be easy though to convince people with triple my jump numbers and years in sport that this concept needs to be eradicated.

P.s. Typed this on mobile so apologies for typos

Certainly.

...

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

[BIGUN 1,049]

Please share with them the Professor's web page, animations, white papers and presentations also.

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

Nobody has time to listen; because they're desperately chasing the need of being heard.

[sundevil777 93]

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On one lift, our group (3 way flat) left 14s after the group before us (4 way flat) and on breakoff I literally had to pull 2s into my breakoff track because I could see a canopy open just off to the side.

14 seconds should have been plenty of time, unless there were real strong upper winds?

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[JWest 0]

sundevil777

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On one lift, our group (3 way flat) left 14s after the group before us (4 way flat) and on breakoff I literally had to pull 2s into my breakoff track because I could see a canopy open just off to the side.

14 seconds should have been plenty of time, unless there were real strong upper winds?

Thats what I was thinking. If 45 degrees gave your 14 seconds I would say that supports it.

I was taught the 45 rule as measured away from the tail but that would take forever.

[mark 102]

JWest

I was taught the 45 rule as measured away from the tail but that would take forever.

What exactly were you taught, and how well does it work for you?

Mark

[kallend 1,621]

JWest

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On one lift, our group (3 way flat) left 14s after the group before us (4 way flat) and on breakoff I literally had to pull 2s into my breakoff track because I could see a canopy open just off to the side.

14 seconds should have been plenty of time, unless there were real strong upper winds?

Thats what I was thinking. If 45 degrees gave your 14 seconds I would say that supports it.

I was taught the 45 rule as measured away from the tail but that would take forever.

There's a protractor on the tail of the plane you jump from?

...

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

[kallend 1,621]

Bill, can you re-post your video showing that no-one ever reaches 45 degrees?

...

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

[yoink 321]

kallend

At an event last week I was talking to a recently USPA certified AFF instructor (certified at well known California DZ) who said he was told by the AFF examiner to teach his students the "45 degree rule".

Did he say what he did?

Did he refuse and try to educate the examiner, or did he nod and smile to get the rating then ignore him?

[wasatchrider 0]

am I the only one that does not know what the 45 degree rule is?

BASE 1519