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Who is first to exit the plane?

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Poll makes no sense...yeah a few times I have been on loads where it was a 3 way freefly and then a 12 way belly where the freefliers got put out first because of upper winds - but those were super rare, and they all worked out awesome.
If the order were reversed completely wouldnt it be pretty much the same?? If not then why not?

As for me and my house, we will serve the LORD...

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I appreciate DR. K's work,..

But all of you guys have forgotten the fundamental thing about this simulation in that it is constructed to support the software writers opinions and doesn't reflect real world physics.

Don't look at the pictures and convince yourselves that this is the way it is.

Here is a fundamental concern of mine:
Quote


"I don't think a belly flier will go less far in forward throw than my calculation,



The same physics and calculations are used to support free fall rates, times and drift. But a Belly Flier has less cross sectional area. Hence less resistance to horizontal motion. You can't use one fact to support one opinion and then basically in the same sentence ignore this fact to come up with conclusions.

If you watch groups from the ground you can clearly see that horizontal motion, from the aircrafts initial horizontal motion, never stops,...There simply isn't enough time for the small amount of air resistance to fully stop their ballistic curve. This is most apparent with tandems, the drogue is clearly visible from the ground and is easy to track. I have encountered way to many individuals that are under the mistaken belief that horizontal motion stops as soon as you exit. I have also encountered way to many people that are under the mistaken idea that ten seconds of trajectory time accounts for a thousand feet horizontal separation with different types of skydiving. Ya all need to re-do some of your math. And many of you need to rethink the examples you use because you can't ignore the difference between a belly fliers horizontal position and a free flyers head down position. The head down position offers much more cross sectional area and slows down horizontal motion considerably sooner than an average belly flier.

The only thing that can stop horizontal motion is changing direction in the air, something that all free fliers and tracking divers, and wing-suitors know well.

This means large belly groups can easily move horizontally into a free fliers air space. Think of the head down position as putting on the brakes as to horizontal motion because of the increased air resistance.

I participate in some of these inane conversations because increased awareness of all of the many variables in exit order increase safety.

And until you all are aware of the two factors that are in fact going to save someone from a collision your all deluding yourselves when you place absolute faith and trust in someone else's' pictures and ideas....

Time between groups. And multiple passes for small landing areas.

C

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

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As for the other thread concerning AAD off button - I honestly believe that 99 percent of jumpers would prefer a visible reachable OFF button.




Start a poll on it.

From what I saw, you were the ONLY person advocating it.


Regarding this thread, the poll options suck so I didn't vote.:


Belly, Big to small.
Freefliers. Big to small.

It's not rocket science.

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hub1100

Agrees with Snowcrash75 and Gearless Chris:

" B F A T Word "

Belly Fly
Free Fly
AFF
Tandem
Wing Suits



I, too, have heard this but I've forgot the reason (I would ask my AFFI but the DZ is closed and I have no way of getting in touch)... what is the reason for Belly before Freefly?
I know the rest has to do with pull height, fall speeds, etc... but belly before freefly I can not remember for the life of me. Thanks :)
You are not the contents of your wallet.

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yoink

***
The only thing that can stop horizontal motion is changing direction in the air, something that all free fliers and tracking divers, and wing-suitors know well.



Nope. Air resistance will stop horizontal motion.

Eventually.

If you exit the aircraft at what altitude, if you do nothing but fall face down, at 13,500, does your horizontal motion stop due to air resistance??

(Be careful here because this altitude is below AGL.)

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

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"While they are in the same moving air mass, they are drifting horizontally at the same rate"

Are you saying that this may not be true?



There is a difference between what Dr. K is saying about drift and what I am pointing out about ballistic trajectories.

Many want to believe that by maintaining a stable free fall (belly) position that this offers the same horizontal air resistance as a head down position. This isn't true. And needs to be included in any mathematical model.

Just think of exiting a King Air by jumping up with your full body perpendicular to the relative wind. You will hit the tail. Such is the difference in body position.

Now the other ting that is a really widely held misconception is that in free fall, again stable neutral position, this will stop forward motion. This is what we call magical thinking. And nothing could be further from the truth. Your on a big air hockey table people, and your ballistic trajectory continues till you hit the ground. You cannot ignore physics by ignorance. But this is another subject. For large groups yo all move the same thru the air, and there are two components to this motion Horizontal and Vertical. It's just that your all moving thru the air following this curve so it appears that your falling straight down. Your only reference is the other nearby people, so it's fairly easy to understand this misconception. But the other circumstance where this misconception exists is in RW where some people believe that to stop forward motion all you have to do is go to a box or neutral position. This belief has maimed people, people.
There is a huge difference between the proper application of extending your legs to move forward at an appropriate speed for the conditions as compared to believing that to stop forward motion all you have to do is go to a neutral box. If your well timed coast isn't so well timed you need to counter your initial input to stop the motion in question. In other words if you put in full leg extension to move quickly and find your self approaching others to hot then yes you need to move backwards to counter the inertia, Coast, whatever you want to call it....

But alas we have people that believe that motion can be stopped by going to the neutral position. This is a little scary that there are so many that believe this. All you have to do is roll a cue ball to see the effects of inertia. Give the ting a little push and it rolls a little bit. The surface friction eventually slows it to a full stop. Give the ball a big push and it can bounce across the table for quite some time. The same in the air.

If and because we haven't included body position and all of the various in be tweens we face the very real situation that by having belly fliers go out first that they, because of their decreased air resistance due their body position they will move horizontally into a free fliers airspace. If the free fliers go out first, their perpendicular body position, to the relative wind, slows down their horizontal motion. Then in this case by belly groups exiting second the distance between types actually increases and the likely hood of sharing the same airspace decreases. The rub is of course that free fliers can develop very great horizontal movement by their varying body positions. This for the astute reader should cause some concern because regardless of exit order,...they can really move around in the sky.

Which brings us back to my points that I have already pointed out above.



Think of it this way, in some other threads about "line trim" many very experienced people have pointed out that we can tell when our canopies are flying like shit by the number of progressive malfunctions that canopy is experiencing. Obviously we should be looking at line trim, but should we be having these inane conversations about malfunctions being the indicator???? Kind of a stupid way to fix things by waiting and arguing about malfunctions. So the conversations usually end up by everyone having this debate about how many inches and the severity of the malfunction and a whole other bunch of nonsense. What you should be doing is having discussions about fixing your line trim well before this malfunction stage. Like when line trim gets to be more than 10% of original specifications. But then the dickheads of the world point out cost and "you don't have to do this or that..." and a hundred other things,... all a side issue to the main problem.

Your all doing the same with these discussions about exit order....:S

C

Aircraft Drop

Now add the terminal velocity, and resistance values for various body positions. And you can see the complexity of trying to simplify things. You also need numbers for air resistance for various body positions. An understanding of V(vac) , and trail would be helpful as well. Or we also have a wealth of information from bomb parabolic trajectory studies. People have been dropping stuff from things in the air as soon as things have taken to the air.

And as someone has just reminded me, free fliers spend less time in the air, this translates to less horizontal motion. This is not a plus for sending them out second.

And here is another way of looking at things that has much real world real experience behind it. If we want to get all the bombs on target, to get them to bunch up so to speak. All we have to do is add air resistance to the bombs that are released later in the stack. This increases their horizontal resistance, changes their parabolic curve so to speak. Al that is required is a small tab on the fin. This means that the objects with the least amount of horizontal resistance go out first. (think Belly) Then the objects with more horizontal resistance are dropped. (Think Free fliers.) They all end up the same place on the ground. Is this what you really want???
But what do I know, "I only have one tandem jump."

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And here is another one that frequently gets lost:


How fast is the aircraft travelling when you get out?
Let's say your going about 80. And for the sake of argument there is no wind. This means that each exit is separated by about 600 feet, using 5 seconds between groups. Correct my math if I'm off here, please....

So for an Otter with 10 groups exiting, for example,....

that takes up about a mile.

All upwind, hopefully???

So the last to get out is basically guanteeed to be 4000 feet away from pattern entry (playground) area????

What if they are a student and what does this say for those areas that traditionally put students out last????

Nothing like setting the stage for failure from the get go???

C

Simple math:

5 sec x 1 min/60 sec x 1 hr/60 min x 80 miles/1 hr x 5280 feet/1 mile = ~ 600 feet of sepeeration. So if your landing area is about 3000 feet wide how many groups can exit overhead? 3000/600 = 5 groups before yo start to run out of ground....
But what do I know, "I only have one tandem jump."

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Thank you for your thoughts about this. This seems like a good time to point out two articles by Bryan Burke that address the horizontal travel problems we are seeing today with disciplines like angle flying and wingsuits thrown into the mix.
http://www.dropzone.com/safety/General_Safety/The_Horizontal_Flight_Problem_935.html
and,
http://www.dropzone.com/safety/General_Safety/Implications_of_Recent_Tracking_Tracing_and_Wingsuit_Incidents_938.html

Trackers can get out 2 miles away and still make it back, and wingsuits can travel 5 or more with a good tail wind. Bryan does an excellent job of explaining the problems and his solutions.
But what do I know?

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ChrisD

Now the other thing that is a really widely held misconception is that in free fall, again stable neutral position, this will stop forward motion. This is what we call magical thinking. And nothing could be further from the truth. You're on a big air hockey table, people, and your ballistic trajectory continues till you hit the ground.



This is the reason why a belly flier facing at a right angle to the line of flight slides past the belly flier facing the line of flight. It's because of the greater surface area presented by the side of the right-angle flier's body, compared with the head-and-shoulders surface area of the facing-the-line-of-flight flier.

What nonsense.

Quote

You cannot ignore physics by ignorance.



What truth.

Mark

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"When I looked down and saw the distressing image of a canopy blossoming below me, it was due to a novice sitflyer who slid down jump run under my 4-way belly team."

What does he say? Did "novice sitflyer" jumped after 4-way or before?


It doesn't matter. Thru poor flying you can slide up or down the jumprun line.

The important thing is for novices freeflyers (and anyone tracking) to move perpendicular to the jumprun line. That way you're not flying into someone else's column of air.

I really don't care what your poll results are. Public opinion does not alter right from wrong. ;)

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I don't consider big to small or small to big to matter one whit.

time drifting absolutely does - belly before freefly (typical into the wind jumprun)



(the various winds, jump runs, etc absolutely matter, but for the typical/general case, the standard rules from these 80,000 threads on the same subject are just fine).

...
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

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billvon

>And for the sake of argument there is no wind. . . . .All upwind, hopefully?

That doesn't make sense. Upwind in no wind? Did you mean something else?



If you start to look at just the parabolic drop, what is called the classic drop physics thing, V(vac), you can see how exiting every 5 seconds at around 80 you put about 600 feet of distance between groups. Basically this is the distance travelled in 5 seconds. If the aircraft isn't travelling at 80, say it's facing into the wind then this distance between groups is smaller. This is where the 45 rule :S comes in. Basically the space describes a 45 500 feet on each side of a square. 500 feet down 500 feet behind, on the 45 degree slope line. Because in the biginining the 182 travelled at about 70, and exiting at about whatever altitude you pick the first thousand burns up about 1000 feet. this takes ~ 10 seconds so some genius figures 500 feet down (roughly 5 seconds.) 5 seconds apart will give yo about a 45 slope. This is why the 45 rule worked for a time. Cause it worked and ensured adequate separation.

Now if you r in a head wind the aircraft isn't travelling at 80 anymore so you don't have the same separation. Luckily when the winds aloft are high most jumping ceases cause the winds on the ground are high too. So when the winds at altitude are roughly exceeding 30 give or take roughly the ground winds are at about 20 and most people start thinkin....

Anyways if the winds at altitude are 30 then the groundspeed is about 50 ,...and what kind of separation do we get at 50 ? Is that enough? (How much ground is covered traveling at 50 mph in FPS?) If you need help thinking about this think of a stationary object at 13.5 everyone will be on top of each other no matter what you do. Your horizontal separation is then a function of your "air resistance," in the relative wind.

So there are factors that have been largely ignored (Think this drift thing) That have greater effects on group sepeeration than the majority thinks and have ignored....

Think of it this way different groups are basically in the same moving airmass. They differ in space and time by about 5 seconds. Now that's a constant 5 seconds not the total travel time. And this is why I have an issue with so many people thinkin that the Drift Calculator is the final word. It's basically because everyone wants a simple answere to a complex problem that they don't understand.

The simple fix is once again more time between groups in higher winds. And shorter jump runs when space is an issue. Or multiple runs. Exit order really doesn't matter. And stop dumping students out last and at the same time expect them to make it to the "holding, play" area, cause they can't!

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

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>Luckily when the winds aloft are high most jumping ceases cause the winds on the
>ground are high too.

Not in my experience. Typically winds aloft are much stronger than surface winds.

And in any case this didn't answer the question. You said "no wind" then you said "put everyone out upwind." That doesn't make sense. If there's no wind you put people out on either side of the DZ. Which means the furthest person is now 2000 feet from the LZ. And since students open at 5000 feet (and get an open and controllable canopy by, say, 4000 feet) this isn't much of an issue.

>nyways if the winds at altitude are 30 then the groundspeed is about 50 ,...and what
>kind of separation do we get at 50 ? Is that enough?

You can do the math pretty easily. Convert IAS to TAS*, subtract wind, then convert knots to FPS, then just multiply by the time between groups. This works for SAME SPEED groups (i.e. all belly) but not for differing groups (i.e. head down vs belly.)

(* - or just use the GPS which shows ground speed.)

> (How much ground is covered traveling at 50 mph in FPS?)

73 FPS.

> If you need help thinking about this think of a stationary object at 13.5 everyone will
> be on top of each other no matter what you do.

If the winds are such that you are stationary at 13.5, and the winds are similar on the ground, you still get pretty good separation on opening. It is the wind DIFFERENCE, not the absolute wind, that gives you problems. (Needless to say, you would not be jumping if the winds at 13,500 were enough to stop the plane - and they were similar on the ground.) It boils down to the plane's airspeed and the difference between winds at exit and opening. Often you can simplify this to the plane's groundspeed, since normally winds near the surface are much lower than winds at altitude.

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billvon

>And for the sake of argument there is no wind. . . . .All upwind, hopefully?

That doesn't make sense. Upwind in no wind? Did you mean something else?



Guinness induced shorthand.


A lot of times when people make these mathematical comparisons they like to take shortcuts along the path to discovery. In the link posted above, prior post, there is the "Plane and the Package." the short cut there is when the author of that animation says in fine print at the bottom: [I] "... (that is, if the influence of air resistance could be assumed negligible),...." [/I]

Of course this whole debate and hypothetical discussion, fun isn't it?, depends upon our understanding of air resistance.

So when I make a simple calculation regarding the MINIMUM time individuals and groups exit an aircraft like an otter I'll use the hypothetical conditions of no wind. No wind on the ground and no wind in the air. (Of course this rarely exists.)

A common exit time in light winds is 5 seconds. (Who thought this up BTW?)

But rarely do things go as planned, ever see every group on an aircraft exit every 5 seconds?

Anyways spotting we can use terms like upwind, downwind, beside or whatever but all in reference to the spot. If we are flying directly into the wind ( if there is wind) we would be downwind of the spot, we would then be directly above the spot, and then we would be upwind of the spot.

When spotting I try to get everyone upwind of the spot when exiting.

Which begs the question: why?

If there isn't any wind we could start exiting on both sides of the spot? As wind speed increases we should start leaning towards exiting closer to the spot and now mostly upwind of the spot. At what point do we make sure every one exits upwind of the spot?

Cause I'm seeing a lot of GPS guided aircraft that turn the green light on as soon as they are directly overhead. And time in the air when people could have exited early and safely depending upon the wind is being wasted.

So is there an issue with exiting before the spot on jump run?


Anyways calculations are easier to understand if we are at 13,500 and there is no wind and the aircraft is moving at 80 mph ~~. (Upwind, kind of a generic term...)

5 seconds, 600 feet apart, due the parabolic trajectory, and all is well....


now add some wind!

Mostly you have answered some questions yourself about this but I do switch between hypothetical and reality sometimes. To make a point. When I say the winds aloft can be screaming if the winds below are high it's a reference to the fact that hypothetically we can in fact have a jump run that is stationary. It is very easy to have winds aloft at 70 mph (and you wont find me jumpin that day.) so hypothetically under those conditions the objects being dropped will in fact have the same exact path and they will be in fact directly on top of each other. Now some of you will point out that some of these objects, if they are different, will undergo acceleration due to the varying amounts of their inherent wind resistance.

So what is the point of all of this?

Cause there is one heck of a spectrum of difference between these two extremes:

On one hand we have conditions of no wind and everyone is 600 feet apart (@80) and on the other hand if the aircraft is stationary everyone is on top of each other. (@0)

What it comes down to is the awareness of how stuff changes as wind conditions change.

And hopefully for some of you, you will develop an awareness of the amounts of friction and acceleration a moving body of air can exert upon an object.

This is yet again another subject but:

You can't always use the total difference in time to make these types of calculations. Think of it this way...

A freeflyier and a belly flier exit, in the same air, how much acceleration does each experience in the first 10 seconds? How much horizontal friction does each have? (The difference is close to 0)

Now take the next ten seconds, lower altitude, how much horizontal friction? (Still close to 0, but now with decreasing altitude the wind component is actually decreasing.)

And so on, and so on...

It comes down to their horizontal friction and acceleration due to the horizontal component of the winds acceleration.

Throw in a few that believe that once you hit terminal yo fall straight down, and a few others that believe that minimal amounts of the difference in horizontal friction can move you hundreds of feet in a decreasing wind gradient and you have the recipe for confusion.

BUT if the end result is to allow more time between groups then believe in whatever floats your boat!

C

Now here is what is going on in the real world:

All loads are being dumped after the spot, many students are getting out way upwind, too far IMO. And no one is making multiple passes or increasing time for increasing wind conditions.

I also like your use of the 45 rule...If students are opening at 4000 give or take and they are 4000 feet away from their landing area, this is again, roughly the sides of a square, the canopy flying roughly at a 45 degree flight path...:)
You can't have a rule that works under every condition!


My first post last year, was about the Sabre 2 and end cell collapse. Basically you can play with the thing and do stuff which takes up time, or you can just wait out that same time. It don't matter, it's the time you take that works not the exit order. (Except of course, if you don't like the idea of fast horizontal canopies open underneath you whilst still in free-fall.)
But what do I know, "I only have one tandem jump."

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packing_jarrett

I always like the idea of an off-set crosswind jump run with freeflyers out first. the opening will be staged by time in freefall, distance traveled between groups, and drift from the wind offering max separation. It's never caught on



I love your idea, :)
this kind of illustrates how we have been brain washed into thinking we have to get everyone out on one pass. Or as fast as possible.

Try thinking differently,... in that we don't.

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

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ChrisD



this kind of illustrates how we have been brain washed into thinking we have to get everyone out on one pass. Or as fast as possible.

Try thinking differently,... in that we don't.

C



Says the guy that doesn't own aircraft or the DZ or pays for the fuel that flies the plane.
Multiple passes on occasion are necessary. Making them part of every jump run becomes prohibitively expensive. Multiple passes are not necessary in most cases.
To answer your opinion that students are getting out too far upwind and not making the holding area, perhaps this is a DZ-specific problem? I'm sure not seeing that situation at any of the several DZs I jump at.

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