Exit Order, Who goes First?

[Brianflian 0]

Anything can be made to work with enough communication.

Let me give you a few examples about why communication doesn't work:

The government has been communicating for years that smoking cigarettes is bad for you. Hasn't worked, has it?

I have seen this happen on numerous occasions:

I am in the first group to exit with strong head winds. I tell the group behind me that they need to leave plenty of space between groups. After exit I look up to see that the otter has barely covered any ground, and is already empty and descending. The whole load go out too early. I turn away from jump run and hoppe for the best, happy I deployed at 2000' and no earlier.

Communication works just fine, if there is a trusted, knowledgable spotter, telling each group when to exit. If that is not available, I'll trust physics, and the exit order described by Burke, Skratch, Kallend, Winsor, and every other common sense skydiover with a will for self preservation.

[Brianflian 0]

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***
As the head winds increase on jump run, leave more room between exits.

Here is a situation that few talk about but I have witnessed:

Groups always need to give adequate time after the prior group to allow for adequate (1500') separation. If uppers are strong, say 60 mph, you have to allow more time than if uppers are light (assuming an upwind jump run)

I believe that you also need to allow for more than 1500' horizontal separation. Here's why:

A plane traveling at 90 mph air speed is going 30 mph ground speed with a 60 mph head wind. To get 1500 feet of horizontal separation (assuming same vertical speed) you need to wait about 34 seconds between groups.

A canopy from the first group flying towards the drop zone after opening and flying at 30 mph will cover about 1500 feet traveling towards the second group in the 34 seconds left between groups. A malfunction, long snivel, inattention to proper opening altitudes, attempted suicide, etc., will put the second group through the space where the first group are flying their canopies.

The problem is compounded if the first group opens high becase of bad spot, or if the first group were freefliers, who tend to open higher because of their lesser experience (just pulling your chain there, Apoil). Also, ground winds are often 180 degrees from uppers.

The remedies I can think of are: to allow adequate time to ensure greater horizontal separation, or to run a crosswind jump run. Neither solution seems optimal, but you can't not jump because of uppers, for crying out loud!

Any thoughts?

Brian

[winsor 186]

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Quote

***
As the head winds increase on jump run, leave more room between exits.

Here is a situation that few talk about but I have witnessed:

Groups always need to give adequate time after the prior group to allow for adequate (1500') separation. If uppers are strong, say 60 mph, you have to allow more time than if uppers are light (assuming an upwind jump run)

I believe that you also need to allow for more than 1500' horizontal separation. Here's why:

A plane traveling at 90 mph air speed is going 30 mph ground speed with a 60 mph head wind. To get 1500 feet of horizontal separation (assuming same vertical speed) you need to wait about 34 seconds between groups.

A canopy from the first group flying towards the drop zone after opening and flying at 30 mph will cover about 1500 feet traveling towards the second group in the 34 seconds left between groups. A malfunction, long snivel, inattention to proper opening altitudes, attempted suicide, etc., will put the second group through the space where the first group are flying their canopies.

The problem is compounded if the first group opens high becase of bad spot, or if the first group were freefliers, who tend to open higher because of their lesser experience (just pulling your chain there, Apoil). Also, ground winds are often 180 degrees from uppers.

The remedies I can think of are: to allow adequate time to ensure greater horizontal separation, or to run a crosswind jump run. Neither solution seems optimal, but you can't not jump because of uppers, for crying out loud!

Any thoughts?

Brian

Your problem here is failing to distinguish the pertinent frame of reference under consideration. As a Physics instructor I found this concept to be particularly frustrating. Students that got it, got it, and students that missed the point would be coming up with the same misconceptions time and time again.

I suggest you go to Tamara Koyn's website and go over the seminar notes that she so graciously put into HTML (to include animating the "window of opportunity" graphics).

The punch line is that separation in the air is not a function of what the ground is doing, period. Separation in the air is relative to the air itself.

The significance of groundspeed on exit is where you land, or, put another way, how much time you have between the first and last exit on a given pass.


Blue skies,

Winsor

[billvon 2,396]

>The punch line is that separation in the air is not a function of what the
>ground is doing, period. Separation in the air is relative to the air itself.

While literally true, separation with time is more accurately described as a function of the _difference_ between windspeeds at opening and at exit. Since winds at opening altitude are generally approximately the same direction as at exit, and since winds at lower altitudes are generally much lower in magnitude, a good first approximation is to wait longer if your groundspeed on jumprun is lower.

[winsor 186]

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>The punch line is that separation in the air is not a function of what the
>ground is doing, period. Separation in the air is relative to the air itself.

While literally true, separation with time is more accurately described as a function of the _difference_ between windspeeds at opening and at exit. Since winds at opening altitude are generally approximately the same direction as at exit, and since winds at lower altitudes are generally much lower in magnitude, a good first approximation is to wait longer if your groundspeed on jumprun is lower.

Agreed, and the larger amount of time you have during your window of opportunity on jump run allows you to build in more separation between groups.

The critical speed for horizontal separation is the speed of the jump aircraft with regard to the air at opening altitude. Since the winds at altitude can vary by both magnitude and direction from those at opening altitude and on the ground, you hit the point of diminishing returns fast when trying to be too exact.

Building in as much separation between groups as is feasible, and avoiding complacency regarding separation, tend to keep us out of trouble.


Blue skies,

Winsor

[Brianflian 0]

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[Your problem here is failing to distinguish the pertinent frame of reference under consideration. As a Physics instructor I found this concept to be particularly frustrating. Students that got it, got it, and students that missed the point would be coming up with the same misconceptions time and time again.

I suggest you go to Tamara Koyn's website and go over the seminar notes that she so graciously put into HTML (to include animating the "window of opportunity" graphics).

The punch line is that separation in the air is not a function of what the ground is doing, period. Separation in the air is relative to the air itself.

The significance of groundspeed on exit is where you land, or, put another way, how much time you have between the first and last exit on a given pass.


Blue skies,

Winsor

My problem here is a failure to communicate.

When I am watching the group before me to ensure adequate separation, I reference the ground, fully cognizant that the ground is doing nothing. The ground is a valid frame of reference for many aspects of skydiving.

It can be demonstrated that at exit, a body is above a certain point on the ground, and the plane is moving away from that point. At opening, the body is above a certain point on the ground and is or will be moving away from that point. I'm not a physics professor, or a mathematics professor, but I am certain that the earth, the plane, and the bodies can all be linked by some equation.

I have also seen the situation I described in practice. I have been under canopy for over 30 seconds flying towards the dropzone when I saw the group after me, who fell at a comparable rate, open directly overhead.

[Brianflian 0]

[reply Agreed, and the larger amount of time you have during your window of opportunity on jump run allows you to build in more separation between groups.)

I must disagree. Do a down wind jump run. If the first group gets out at the short end of the window of opportunity, the second group might get out at the long end with very little time in between. The critical factor is horizontal separation, which can be most easily related to as point above the ground.


(The critical speed for horizontal separation is the speed of the jump aircraft with regard to the air at opening altitude. Since the winds at altitude can vary by both magnitude and direction from those at opening altitude and on the ground, you hit the point of diminishing returns fast when trying to be too exact.)

It should be obvious that we can't come up with an exact equation for each situation. And since we can't be exact, nor do we have the time, and often the mental capacity or information to take into account all the factors on jump run and still remember the skydive (unless you are freeflying, they don't have to remember anything (another little dig at Apoil?) you can simplify everything by using the ground as a reference. Measure horizontal separation by the distance the plane has traveled over the ground from the point over the ground where the previous group exited.

(Building in as much separation between groups as is feasible, and avoiding complacency regarding separation, tend to keep us out of trouble.)


Agreed. I for one, have vowed not to be rushed by pilots, DZO's or other skydivers when choosing my exit point. Don't let people rush you out the plane onto the previous group.

Brian

Hey Skratch, how am I doing?

[quade 3]

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Measure horizontal separation by the distance the plane has traveled over the ground from the point over the ground where the previous group exited.

You have access to a Norden Bomb Sight or something?

I don't know about you, but I find it incredibly difficult to know exactly where the previous group got out . . . especially if I'm the next guy spotting -after- a 16-way. In other words, I ain't anywhere -near- the freekin' door and it's gonna take me a few seconds to get there after the last diver leaves. There's just going to -have- to be some guesstimation going on for that to even sort of work.

quade -
The World's Most Boring Skydiver

[Brianflian 0]

I don't know about you, but I find it incredibly difficult to know exactly where the previous group got out . . . especially if I'm the next guy spotting -after- a 16-way. In other words, I ain't anywhere -near- the freekin' door and it's gonna take me a few seconds to get there after the last diver leaves. There's just going to -have- to be some guesstimation going on for that to even sort of work.

I already stipulated that we can't be exact. You can however, do a bit of interpolation. Or you can get someone who moves faster to spot.

[quade 3]

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I already stipulated that we can't be exact. You can however, do a bit of interpolation. Or you can get someone who moves faster to spot.

Ok, I just wanted to point out the difficulties and guesswork involved. It's exactly what I do when I have to and . . . well, there's almost no way I'm climbing out -after- somebody else. (Camera Weasle don't ya know)

quade -
The World's Most Boring Skydiver

[billvon 2,396]

>The critical factor is horizontal separation . . .

That's true.

>which can be most easily related to as point above the ground.

True as a very rough rule of thumb, but not true always. Simplest example: plane doing 80kts, winds 80kts on the nose, winds at opening altitude 80kts from the same direction. Everyone will open at exactly the same spot over the ground, but the separation will be the same as if there was no wind at all - since the important frame of reference is at opening altitude. According to the jumpers who just opened, they're moving away from the 'opening point' at 80 kts. The next group will be in clear air.

Since the winds at opening are _usually_ from a similar direction and are not as strong as upper winds, groundspeed can be used as a rule of thumb. There are a few situations (winds opposite direction at opening altitude) where it doesn't work, but fortunately those conditions do not occur often.

[Brianflian 0]

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>The critical factor is horizontal separation . . .

That's true.

>which can be most easily related to as point above the ground.

True as a very rough rule of thumb, but not true always. Simplest example: plane doing 80kts, winds 80kts on the nose, winds at opening altitude 80kts from the same direction. Everyone will open at exactly the same spot over the ground, but the separation will be the same as if there was no wind at all - since the important frame of reference is at opening altitude. According to the jumpers who just opened, they're moving away from the 'opening point' at 80 kts. The next group will be in clear air.

Since the winds at opening are _usually_ from a similar direction and are not as strong as upper winds, groundspeed can be used as a rule of thumb. There are a few situations (winds opposite direction at opening altitude) where it doesn't work, but fortunately those conditions do not occur often.

I'm sorry, Bill. that just sounds like a very tortured argument to make the theoretical sound more important than the practical.

The ground is still the most useful frame of reference, since the "window of opportunity" on jump run relates specifically to where the jumpers want to land (usually on the ground). And without wind drift indicators at opening altitude, there is no information to the spotter about wind velocity or direction at opening altitude.

In practice, winds at opening altitude usually are closer to those on the ground, rather than those at exit altitude.

[kallend 1,623]

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>The critical factor is horizontal separation . . .

That's true.

>which can be most easily related to as point above the ground.

True as a very rough rule of thumb, but not true always. Simplest example: plane doing 80kts, winds 80kts on the nose, winds at opening altitude 80kts from the same direction. Everyone will open at exactly the same spot over the ground, but the separation will be the same as if there was no wind at all - since the important frame of reference is at opening altitude. According to the jumpers who just opened, they're moving away from the 'opening point' at 80 kts. The next group will be in clear air.

Since the winds at opening are _usually_ from a similar direction and are not as strong as upper winds, groundspeed can be used as a rule of thumb. There are a few situations (winds opposite direction at opening altitude) where it doesn't work, but fortunately those conditions do not occur often.

I'm sorry, Bill. that just sounds like a very tortured argument to make the theoretical sound more important than the practical.

The ground is still the most useful frame of reference, since the "window of opportunity" on jump run relates specifically to where the jumpers want to land (usually on the ground). And without wind drift indicators at opening altitude, there is no information to the spotter about wind velocity or direction at opening altitude.

In practice, winds at opening altitude usually are closer to those on the ground, rather than those at exit altitude.

They weren't at Z-Hills earlier this week. Besides, is "usually" good enough? My main "usually" opens, but I still have a reserve.

...

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

[LouDiamond 1]

This discussion amazes me every time I hear it. Each side pulls out the slide rules and ultimately nothing is gained. At the same time I fail to see how anyone could not comprehend the reason FF gets out last. One would think the visual description depicted on the web page mentioned would suffice but as it has often been said....Common Sense isn't common. Unfortunately, it will take someone getting killed or injured before it is universally accepted that FF needs to get out after belly. Just my 2 cents

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[billvon 2,396]

>I'm sorry, Bill. that just sounds like a very tortured argument to make the
>theoretical sound more important than the practical.

The theoretical is not more important than the practical, but it's important to remember that the practical is _based_ on the theoretical, and not the other way around. That way you know when the practical rule of thumb will fail.

As an example of when it will fail - santa ana winds at Brown. Winds 50kts from the east at altitude, 10kts out of the west at 2000 feet (due to mountain wind shadow.) In this case you need to leave even _more_ than the usual ground-based separation, because the usual assumption (winds same direction but lighter at opening alt) fails. And yes, this does happen.

>The ground is still the most useful frame of reference, since the "window of
> opportunity" on jump run relates specifically to where the jumpers want to
> land (usually on the ground).

Definitely. But now you're talking about spotting, not exit separation. Spotting generally involves where to put out the first group; exit separation refers to how long the next group has to wait.

>And without wind drift indicators at opening altitude, there is no information
> to the spotter about wind velocity or direction at opening altitude.

You mean other than winds-aloft forecasts, information from the pilot (based on GPS speed) and information from the first load. Such information is readily available, but you have to ask for it.

[Brianflian 0]

Okay.
Brian

[Deleted 0]

biggest rw group to smallest rw, to FF, to student, to tandems

[fudd 0]

Just want to throw in my opinion. I'm no expert at this, but this is what i've concluded:

Bellyfliers first:
pro: Drift causes more horizontal seperation.
con: Opening at almost same time for freeflyers and belly fliers.

Freeflyers first:
Pro: Time difference (vertical seperation). A freeflyer exiting first would have been under canopy for 20 seconds when the bellyflyer opens.
Con: Drift can cause zero horizontal seperation.

There's a lot of factors in play here, and arguments for both cases.
I haven't decided yet what exit order I would prefer. However it seems like most people (and the ones with a lot of experience) argue for bellyfliers first, so with my low experience that option would seem like the most wise.
I would agree in theory. Especially when looking at the simulations. However, when it comes reality I am not entirely convinced what would be the safest.

There are only 10 types of people in the world. Those who understand binary, and those who don't.

[Ron 7]

Well I started this whole thing (Geeze am I sorry)...

And I got an answer from the S&TA at Z-hills...Of course he yelled it at me and called me ingnorant for not understanding how clear it was????? Even though he had never told it to me before????

Any way, he told me that they had tried the "Flat goes first" exit order at Zhills for 2 weeks, and it was unsafe. Now if he feels like posting his argument here.....I'll let him do it. (it will miss some of the VOLUME he gave it to me with, but it does have some merit) He is not a dumb guy, and I do respect his opinion, if not his approach to giving it.

I did have another talk with Paul at the DZ bar....He was much more easy to talk to, and he agreed with Pips point of view....

Two guys I respect, both with more jumps than me, and both with more at Z-Hills than me, both like this exit order.
I am not going to argue it with them, although I will gladly disscuss it with them some more.

And I would like to go on the record to say that I have never had a problem like this at Zhill's (or any other DZ for that matter) with exit seperation.

Freefliers can go first with a degree of saftey....It can, and does cause at times extra passes. But as Paul pointed out "It's not your fuel being used, and its worth it to be safe". He did point out some very good points, and I am glad we had that disscusion.

Anyhow....Z-Hills is a great place, and like I said even though it is not the "standard norm" other than extra passes I have never seen a problem with freefliers first. In theory it can be bad, but I personaly have never had a problem with it.

Ron

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[apoil 0]

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>if you only ever do it one way, you are wrong.

I think that's a dumb thing to say. Thankfully it's not true for riggers, AFF-I's, competitors, record attempts etc. Occasionally, there is actually a right way to do something, and doing it that way all the time does not make it wrong.

This is getting way off topic now.

Maybe what I said came across a little wrong.
But your counterargument is even worse.
So as a rigger I should pack a Javelin the same way as a Racer the same was as a vector?

AFF-I's? Flexibility is KEY to being a good AFF instructor. Everything is up to reinterpretation including the diveflow for different students in different situations.

competitors? If they come up with a new way to engineer a difficult skydive that comes from thinking outside the box, do you think they wont jump on it?

You may be right that there's only one right way to do certain things, but I'm instatntly suspicious any time I hear ANYONE say "this is the only right way to do this". That's narrow minded thinking and I'm surprised to hear you of all people say it.
What you probably mean is "all we know so far indicates that this is the best of other possible ways".

Note: I'm not talking about exit order anymore.
As far as that's concerned, it seems like at zhills we make it work and those who are in charge have a good deal of experience and have found empirically (rather than theoretically) that this is the best way to do it. But it's not just one way - freefliers don't always get out first.

[billvon 2,396]

>So as a rigger I should pack a Javelin the same way as a Racer the
> same was as a vector?

Not at all - but by your argument, if you are a rigger and only pack a javelin one way (i.e. according to the manual) you are wrong. I disagree.

> . . I am suspicious any time I hear ANYONE say "this is the only
> right way to do this".

So am I. But you didn't say that. You said: "if you only ever do it one way, you are wrong." There are many ways to do something, some better than others. It is good to consider all ways to do something. If there is one way that's better, using that way all the time does not make it wrong, despite your S+TA's handy saying.

Sometimes putting freeflyers out first can work. Sometimes, for a given drop zone, putting belly out first as a _rule_ works better. By your standards they would be wrong. Again, I disagree.

[Tonto 1]

Spot on. Fast is last.

Why?

to reduse the chance of collision between groups and give everyone the chance of a good spot. We only jump a Porter, so it's quite easy.

t

It's the year of the Pig.

[Rdutch 0]

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And I would like to go on the record to say that I have never had a problem like this at Zhill's (or any other DZ for that matter) with exit seperation.

Freefliers can go first with a degree of saftey....It can, and does cause at times extra passes. But as Paul pointed out "It's not your fuel being used, and its worth it to be safe".

Hey Ron not arguing with you, but I do remember when our team trained in Zhill's we did have a problem getting a pilot to make another pass, when the groups exiting before took a long time to exit, and we were miles away from the dz. So this work's as long as your pilot doesn't mind making another pass. Also that day a LOT of people landed out and it was mostly the solo freeflyers that got a good spot, and the larger flat groups landed out.

Ray
Small and fast what every girl dreams of!

[dreamsville 0]

I have jumped at Zhills and other places, both as a R/W and free flyer, and also have not had problems with separation. One thing I think most of us can agree with is that jumpers should have an idea of the winds at altitiudeS, ground speed if possible, and watch how fast the group ahead slides away horizontally. Another thing is, if ground speed is higher BE IN THE DOOR AND READY TO EXIT when safe to do so.

Although I have probably been a guilty party at certain times, I have seen people dink around before and during the exit (you can't dink around afterwards: gravity takes care of that) when it wasn't necessary, as the seconds tick beyond a reasonable separation interval. A lot of the time we can minimize the need for another pass. Avoid putting anyone in the position of wanting to pull higher due to the spot, but being afraid to because of groups that exited afterwards!

Harry

I don't drink during the day, so I don't know what it is about this airline. I keep falling out the door of the plane.

Harry, FB #4143

[SkymonkeyONE 3]

Well, as Ron also knows, Raeford has freeflyers out before belly flyers. I don't buy it AT ALL, but I am not the DZO or the S&TA. Personally, I think it's that way here because certain individuals like riding in the back of the plane and then getting out and being able to land first. This is all fine and dandy with me up to the point that I catch one of them sitting in brakes at 1500 feet right over my turn-in point under a parachute that is 30 square feet larger than mine. Their argument is that they also have to suck it up in the winter when it's cold in the back, so that's the trade-off. I can truthfully say that I have never once had to dodge (in freefall) to avoid one of our first-leaving freeflyers, so in my (quite extensive) experience I don't see any reason to stand up and fight to change it right now. Still, I would be a lot happier with an Eloy-type exit order.

Chuck