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Horizontal Separation

 

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turnlow  (D License)

Jul 21, 2003, 3:52 PM
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Horizontal Separation Can't Post

OK, had a fun one this weekend. We were on an 8-way RW jump and left the aircraft first, followed by a low time freeflyer (about 35 jumps). Around 10,000 feet the freeflyer passed less than 10 yards off and 15 yards below our formation traveling at near tracking speed. It was a bit disturbing - particularly given the fact the he told me he was going to pull around 4,500 feet.

I had a chat with him when he landed about the dangers of that particular situation. His first comment was that he "waited 4 seconds after we left before jumping." I tried to impart to him 2 main points:

1) Exit separation is about horizontal separation, not elapsed time between groups - you must look,

2) You must not track or freefly back along jump run - in most cases, you must be perpendicular to jump run.

Anything I missed? Comments?
__________________________________________________


CanuckInUSA  (D 26396)

Jul 21, 2003, 3:59 PM
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Re: [turnlow] Horizontal Separation [In reply to] Can't Post

In reply to:
You must not track or freefly back along jump run - in most cases, you must be perpendicular to jump run.

IMHO, this is one of the biggest dangers (especially to people learning) of freeflying. When I do a solo freefly, I always make sure I'm perpendicular to the flight line. But what about the times when we're chasing someone backsliding across jump run? God the longer I'm in this sport (which I love) and the more jumps I do, the more close calls I see and realize how dangerous it can be at times.


(This post was edited by CanuckInUSA on Jul 21, 2003, 4:02 PM)


gus

Jul 22, 2003, 12:34 AM
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Re: [turnlow] Horizontal Separation [In reply to] Can't Post

Last weekend it was pretty windy, right on the limits on the ground and strong up top. Run-in was into wind and people were not leaving anywhere near enough gap between groups - the group that got out after us were way too close. After a few loads people started to realise that our groundspeed was so low they could put 15 seconds between groups but they certainly weren't at the start of the day. It's quite scary stuff and whoever is jm needs to remind people how important horizontal seperation is.

Gus


Newbie  (C License)

Jul 29, 2003, 4:48 AM
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Re: [gus] Horizontal Separation [In reply to] Can't Post

In reply to:
Last weekend it was pretty windy, right on the limits on the ground and strong up top. Run-in was into wind and people were not leaving anywhere near enough gap between groups - the group that got out after us were way too close. After a few loads people started to realise that our groundspeed was so low they could put 15 seconds between groups but they certainly weren't at the start of the day. It's quite scary stuff and whoever is jm needs to remind people how important horizontal seperation is.

Gus

i agree with this, but would also add that JM's are not the be all and end all - i STILL hear JM's saying to jumpers at my dz on my load to wait "until the previous group is at a 45 degree angle" when asked how long to leave for separation.

Bottom line, it's all about distance, horizontal that is. Aks billvon about this if you like, or kallend, they can get pretty indepth about how it works, but they have simple little formulas that can be used to estimate 1000ft of separation.
And don't let people shouting "GO!" behind you put you off - as long as you aren't leaving excessive time between groups, you need to make sure you leave a proper amount of separation. People shouting "GO!" are most likely to be the people streaking past like in the original post IMO.


Premier billvon  (D 16479)
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Jul 29, 2003, 8:37 AM
Post #5 of 75 (2752 views)
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Re: [turnlow] Horizontal Separation [In reply to] Can't Post

I've had this happen to me too. It's more of a problem with tracking than with exit separation - a clueless freeflyer can easily cover 1000 feet, and there goes even a good amount of exit separation. Facing perpindicular to jump run is the key here.


tphilpin  (D 24815)

Jul 29, 2003, 8:50 AM
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Re: [turnlow] Horizontal Separation [In reply to] Can't Post

Everything you always wanted to know, including an online freefall demonstration for spacing can be found at : http://www.iit.edu/~kallend/skydive/

You will learn it is NOT about 45 degrees, it is NOT about ground speed.... with the physics to prove it.

Enjoy


tattoojeff  (A License)

Aug 21, 2003, 4:40 PM
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Post deleted by tattoojeff [In reply to]

 


Premier Remster  (C License)

Aug 21, 2003, 4:42 PM
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Re: [tattoojeff] Horizontal Separation [In reply to] Can't Post

the site works fine for me

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


Premier LouDiamond  (D 25931)
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Aug 21, 2003, 4:56 PM
Post #9 of 75 (2648 views)
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Re: Horizontal Separation [In reply to] Can't Post

WOW, this issue is like a social disease, it always comes back. I will say that if you want to read all about this to do a search and you can spend hours reading people argue about it. Frankly, it's scary how many people don't have a clue on this issue. I've attached a Excel doc that you can download, print and laminate and tape next to the door of your A/C for reference. It is quick and easy to use and ends debates on the A/C.
Attachments: Exit Separation.xls (16.5 KB)


andy2

Aug 21, 2003, 5:09 PM
Post #10 of 75 (2644 views)
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Re: [tattoojeff] Horizontal Separation [In reply to] Can't Post

Quote:
but im not sure why 45 degree method is flawed

I think the flaw in it is that by tilting your head a bit, or picking it up higher etc will drastically change that "45 degree angle". Also this is subjective as each aircraft has a different door and therefore will support a different "angle of observation" when viewing exiting jumpers. PLus wind speed will often dictate how long of a seperation you need. The 45 degree angle is just inherently flawed all around, pretty much.

At least this is what I have thought about and plus it has been reinforced by jumpers at my DZ. Timing is everything, not what angle they look like theyre at.


kallend  (D 23151)

Aug 21, 2003, 5:47 PM
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Re: [tphilpin] Horizontal Separation [In reply to] Can't Post

In reply to:
Everything you always wanted to know, including an online freefall demonstration for spacing can be found at : http://www.iit.edu/~kallend/skydive/

You will learn it is NOT about 45 degrees, it is NOT about ground speed.... with the physics to prove it.

Enjoy

Not everything - someone tracking up or down the line of flight renders any calculation useless. As BillV said, 1000ft of separation can easily be eaten up by a clueless individual.


freakydiver  (D 26421)

Aug 22, 2003, 8:12 AM
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Re: [turnlow] Horizontal Separation [In reply to] Can't Post

Ummm,

"1) Exit separation is about horizontal separation, not elapsed time between groups - you must look, "

Actually I completely disagree - separation is calculated based on upper winds and jump run direction with respect to those upper winds, and aircraft speed. I have seen many many arguments to show that a count is much more solid than looking. The whole 45 degree angle thing of looking is a complete myth - I'm sure Kallend and billvon would completely back these statements up.

#2 you state is correct. #1 I think is wrong.

Also, 4 seconds IMHO ain't shit for seperation in most larger turbine DZ aircraft...

I'd be pissed as hell if I were you eight though and really drive into this noobiez skull the importance of seperation, especially since I've noticed the same things on alot of DZs out there, separation seems to be taken for granted more times than not.

Be safe!


Premier billvon  (D 16479)
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Aug 22, 2003, 8:59 AM
Post #13 of 75 (2565 views)
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Re: [freakydiver] Horizontal Separation [In reply to] Can't Post

>>1) Exit separation is about horizontal separation, not elapsed time between groups - you must look, "

>Actually I completely disagree . . .

I disagree about the 45 degree angle too. However, one method of ensuring good exit separation is to look at the _ground_ and simply exit when you've covered 1000 feet or so. To do this you have to be a good spotter, which means that you have to be able to look straight down (which is the hardest part of spotting to learn.) This method effectively gives you more time when the upper winds are high since it will take the plane longer to cover that 1000 feet. The nice part about this method (the Skratch method) is that you don't need to know the upper winds to perform it.

And of course you should be looking out the door anyway just to make sure you are clear of traffic.

>Also, 4 seconds IMHO ain't shit for seperation in most larger turbine DZ aircraft...

Definitely. You need 5-7 seconds at least, and that's with a fast plane and no wind. 4 seconds only works if you wait 4 seconds _then_ start your climbout - assuming your climbout takes an additional few seconds.


Hooknswoop  (D License)

Aug 22, 2003, 9:31 AM
Post #14 of 75 (2547 views)
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Re: [turnlow] Horizontal Separation [In reply to] Can't Post

Another way of looking at separation is the time between the base exits a DC-3 and when the last diver exits. 8+ seconds is normal and the last diver catches the base. In the 8+ seconds, the aircraft is covering ground (how much depends on the uppers), but for the last diver, the distance to make up is vertical, not so much horizontal.

Derek


freakydiver  (D 26421)

Aug 22, 2003, 10:21 AM
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Re: [billvon] Horizontal Separation [In reply to] Can't Post

Thats a great thought Bill - thanks!


kallend  (D 23151)

Aug 22, 2003, 11:32 AM
Post #16 of 75 (2518 views)
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Re: [billvon] Horizontal Separation [In reply to] Can't Post

In reply to:
>>1) Exit separation is about horizontal separation, not elapsed time between groups - you must look, "

>Actually I completely disagree . . .

I disagree about the 45 degree angle too. However, one method of ensuring good exit separation is to look at the _ground_ and simply exit when you've covered 1000 feet or so. To do this you have to be a good spotter, which means that you have to be able to look straight down (which is the hardest part of spotting to learn.) This method effectively gives you more time when the upper winds are high since it will take the plane longer to cover that 1000 feet. The nice part about this method (the Skratch method) is that you don't need to know the upper winds to perform it.

And of course you should be looking out the door anyway just to make sure you are clear of traffic.

.

Just a caveat on this. Strictly speaking, you want to cover distance relative to the air at opening altitude. Usually this is pretty much the same as distance over the ground, but if the uppers are in the opposite direction to the lowers then you can find yourself with reduced separation. This is a fairly common ocurrence around here (N. Illinois) due to proximity of the great lakes. I believe it can happen near oceans and mountains too. Last Sunday at the DZ the upper winds were moderate out of the NW, while at 2500ft the winds were 20kt out of the east.

Winsor also came up with an interesting scenario - if you make a jump from a balloon moving with the airmass (as balloons are wont to do), then you have groundspeed but regardless of any exit separation, the canopies end up in the same place (assuming not deliberatley flown off the line of flight).


Premier billvon  (D 16479)
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Aug 22, 2003, 12:42 PM
Post #17 of 75 (2500 views)
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Re: [kallend] Horizontal Separation [In reply to] Can't Post

> but if the uppers are in the opposite direction to the lowers then
>you can find yourself with reduced separation.

Yep. Fortunately, this condition is rare at most DZ's, and it is _very_ rare to have lower winds of a similar magnitude as upper winds but in the opposite direction. If the winds are going the opposite direction at opening altitude but are much lighter (i.e. 30kts at altitude, 5kts at 2000 feet) then you're still in pretty good shape.

>Winsor also came up with an interesting scenario - if you make a
> jump from a balloon moving with the airmass (as balloons are wont
> to do), then you have groundspeed but regardless of any exit
> separation, the canopies end up in the same place . . .

True if the winds are the same from 8000 feet (or exit altitude) to the ground. Since they rarely are, you'll still get some separation, although not as much.


riddler  (D 10234)

Aug 26, 2003, 12:12 AM
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Re: [billvon] Horizontal Separation [In reply to] Can't Post

I think exit separation is one of the biggest problems in skydiving today - anyone with more than 50 jumps has probably witnessed someone buzz close to them in freefall while under canopy - it happens to all of us. There are all sorts of pressures to not spot correctly and not leave enough exit separation. Let me list a few I've witnessed:

1. We have GPS guided turbine planes dropping us from two miles in the air. We've been conditioned that the GPS is more correct than our good judgement. When the rest of the jumpers on the plane see the green light, they expect the jumper in the door to leave. The pilot expects you to leave. No one expects the person in the door to have as good or better judgement than the GPS.

2. Spotting is becoming a lost art. Yeah, we've had to do it for an A license, but how often will an experienced freeflier do it? Usually, they're not the first out of the plane and most jumpers I've observed watch the group ahead of them leave, rather than looking at distance covered over the ground.

3. Dropzones typically have less than a mile of runway and many jump planes are capable of holding more than a dozen jumpers. Dropzones don't want to have to make two passes - it's expensive to make two passes. They want to get all jumpers out of the plane in one pass. At the dropzone I trained, the King Air holding 16 jumpers would cover the length of the runway in just over 40 seconds - not enough time to get everyone out with appropriate exit separation in one pass.

4. The folks in the back of the plane don't want to get screwed on the spot. Tandems don't want to land off with a tandem passenger. Freefliers don't want to have to pull high to make it back from a long spot. When that green light goes on, people in the back start yelling like it's a sinking ship. There is no trust of the person in the door.

5. There isn't a lot of communication between people on the plane. If the plane hold 20 people, but there are two eight-ways, there is nothing wrong with leaving 20-30 seconds of separation between those groups. You can plan on taking longer than the minimum if there are fewer groups on the plane.

I expect there are even more situations than I've listed. The point is if we want to change this culture, we can't do it by changing one thing. We have to work on a number of issues. More time can be spent on spotting - not just for students, but for experienced jumpers. We should have a good enough relationship with each other on the plane that we trust the person in the door to make the right choices - usually they're the only ones that can see what's going on - why yell at someone when you can't see what they see? Jumpers need to be educated on the minimum separation excepted, as well as understanding that there are plenty of circumstances when they can take even more time. Dropzones with fast planes carrying lots of jumpers over a short runway should plan on making more than one pass. Is any one of these issues more relevant than the others to exit separation? If one is more outstanding, then maybe we can start there.


andy2

Aug 26, 2003, 5:41 AM
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Re: [riddler] Horizontal Separation [In reply to] Can't Post

I just wanted to add something from a beginner (me). I've done quite a few 2 ways, 3 ways, etc, but also I've done quite a few solos. When I do a solo and I'm wedged between freefliers, a 4 way, and then tandems out next I usually get out and immediately track perpendicular to jumprun. Since I'm by myself it doesn't matter if I max track and zoom out of the jump run path. Usually 7 seconds of tracking will get me CLEARED out of everybody, and while it eats up a little freefall time its good practice, and then I'm safe and confident to try whatever manueveur I want (within reason of course Tongue). What do you all think about that?


diverdriver  (D 19012)

Aug 26, 2003, 6:39 AM
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Re: [riddler] Horizontal Separation [In reply to] Can't Post

Quote:
3. Dropzones typically have less than a mile of runway and many jump planes are capable of holding more than a dozen jumpers. Dropzones don't want to have to make two passes - it's expensive to make two passes. They want to get all jumpers out of the plane in one pass. At the dropzone I trained, the King Air holding 16 jumpers would cover the length of the runway in just over 40 seconds - not enough time to get everyone out with appropriate exit separation in one pass.

Who says you have to be directly over the runway in order to leave the plane? I almost always have people out of the plane on either end of our 4,500 foot runway and that's one of the longer ones in the skydiving community.

I once had a 15 knot ground speed in the otter. The jumprun time was about 6 minutes for one pass. They were giving 45 seconds in between groups. Totally worked. The jumprun timing is dependant on how many groups, what kind of groups, and ground speed.


riddler  (D 10234)

Aug 26, 2003, 7:53 AM
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Re: [diverdriver] Horizontal Separation [In reply to] Can't Post

Quote:
I once had a 15 knot ground speed in the otter. The jumprun time was about 6 minutes for one pass. They were giving 45 seconds in between groups. Totally worked.

Ahh, Chris - you can be my pilot anytime. Most pilots don't communicate those things. It would be SO nice to get a report on uppers as well as ground winds, ground speed, etc. Maybe that's too much information for most skydivers? It's not for me.

And I completely agree with getting out prior to the runway, as long as there are no uppers. If the runway is a mile long, with no uppers, I've been able to get out half the length prior of the runway and easily make it back - I tell that to students when teaching them to spot. However, it's easier to err on the other side, since most jump runs are upwind and any uppers are going to blow you back, you have a better chance of getting back on the far side. But yes, you do have more than the length of the runway to work with. It comes down to knowing how many groups, what ground speed is and how far you are making it over the ground.


freakydiver  (D 26421)

Aug 26, 2003, 8:04 AM
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Re: [diverdriver] Horizontal Separation [In reply to] Can't Post

Luckily, one of my first pilots stood in in the AFF class and explained things quite similarly to the way I've hear you and Billvon have explained things. I do think there is a growing problem in our precious sport in horiz separation.

This weekend for instance, we were out first out of a King Air - a four way sit, poised door exit. We exit, I'm second to rear in the train, and guy behind me is last in the train (duh freaky). He trains up with me, the two guys in front cork. We turn towards the plane about five seconds after exit, low and behold THERE IS SOMEONE EXITING. I was PISSSSSSSSSED. Low uppers all day, 5 seconds, dude is leaving the plane. There should seriously be some additions to learning materials about seperation distances and time based on all factors involved as imho, too many people are taking things for granted.


CanuckInUSA  (D 26396)

Aug 26, 2003, 8:51 AM
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Re: [andy2] Horizontal Separation [In reply to] Can't Post

In reply to:
What do you all think about that?

That's good, I wish more fliers would do the same. Cool


Premier ianmdrennan  (D 25821)
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Aug 26, 2003, 8:56 AM
Post #24 of 75 (2355 views)
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Re: [diverdriver] Horizontal Separation [In reply to] Can't Post

Agreed. Every day (normally twice) the pilot updates the upper wind information next to our aerial photo for 3, 6, 9 and 12g's. Makes all the difference in planning the jump run, exit times, etc.

Blue skies
Ian


Fast  (D 28237)

Aug 26, 2003, 9:19 AM
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Re: [ianmdrennan] Horizontal Separation [In reply to] Can't Post

As a new jumper I ahve made most of my jumps with someone (coach/affi) and for the most part they are letting me know ehen to get out, how long to wait etc., however I have made it a habbit to talk to somone be it one of the really experienced affis, or someone about what the wind is like at altitude, and how the spots have been for the loads that have already went up. Even though somone has been keeping track of me, its giving me some practical experience about what to look for on jump run, rather than just getting out the door because people don't want to wait, or get a long spot.

One time one of our affIs actually stood in the door a good 30 seconds because he knew that the spots had been short all day. We were right in the middle of the load, everyone looked at him a little wierd for standing in the door of the otter so long, but people trust him because of the experience he has and realize there is a reason he is waiting. Sure enough, it was the best spot of the day.


(This post was edited by Fast on Aug 26, 2003, 9:20 AM)


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