Seperation - near collision during deployment

[lintern 1]

I did a solo sit jump at the weekend and came very close to another canopy during deployment.

I have been sit flying for a year now and never came so close to a collision.

The group before me was a 2 way freefly.

After they had exited I left 5 seconds (counting 1 thousand, 2 thousand etc) before I jumped.

I did little in freefall, a few turns and a side flip.

There was a thin layer of cloud from 4000ft to 3500ft and I deployed just under 3500ft.

Just as I felt the lines and bag coming off my back I saw a canopy suddenly open below me, about tens of feet away to the side.

Its hard to judge distance in the air due to persepctive (especially when falling past a stationary object during freefall!) but I estimate the canopy was probably 20 ft away.

Anyway, it was too close for my liking and the person under this canopy was also uncomfortable about how close it was.

If they had had an off heading opening it could have been closer still.

It was too late for me to track away from this other canopy because my deployment had started.

And I couldnt see anyone below me just before deployment because the cloud was from 4000ft to 3500ft.

My question is, I have always left at least 5 seconds seperation and never had a problem, so why this time did I come so close ?

I have heard of the 45 degree rule but this is a controversial topic.

Some people say it works, other people say it doesnt work and not to use it.

I remember finding a power point presentation on the internet about seperation, which showed a video clip of why the 45 degree rule doesnt work.

I cant remeber the link but I can get hold of it.

So how long should I leave between seperation, if last time 5 seconds wasnt enough ?

[WatchYourStep 0]

NO PRO OR INSTRUCTOR HERE

What were the ground speeds like?

What were the uppers doing, etc?

A 5 second blanket rule isn't a good one to go from what I was taught. There are several other variables.

Not to mention when you sit do you normally fall down the tube or are you driving/backsliding over the sky.

Just questions not ripping on you or anything.

Edited to add: At least being that close left you plenty of time to do some CRW

"You start off your skydiving career with a bag full of luck and an empty bag of experience. The trick is to fill the bag of experience up before your bag of luck runs out."

[lintern 1]

Quote

What were the ground speeds like?

What were the uppers doing, etc?

This is something I am going to have to pay more attention to.

The ground speed wasn't very much, maybe 10-15 knots.

But I dont know about the uppers.

As for back sliding, when I have jumped with other people in sit i have never had that problem and tend to fall relatively straight down the tube.

[speedy 0]

A quote from John Kallend was " 5 seconds is never enough delay". I did manage show that in exceptional conditions it could be enough, but most of the time it isn't.

You followed a group out, they are going be tracking at break off, which means you need more separation than when following a solo.

Here's link to Kallends skydiving resources

Download the "Powerpoint presentation on exit safety with freefall sim.(updated 3/2004) "

Read it, study it, ask questions here or at your DZ about bits you don't understand. When you have understood the presentation, you should be able to calculate the delay you need yourself.

Dave

Fallschirmsport Marl

[feuergnom 22]

five seconds delay sounds a little short. my lowest comfort-level when doing a solo starts with 7, but it depends all on the speed of the uppers. when it's hauling even 15 to 20 seconds can be to quick.

and ending up 20 feet away on a deploying canopy would have me swearing and cursing for the rst of the ride. i guess i'd quit for the rest of the day, to figure out what went wrong.

as for the group before you being freefliers as well: did you ask what kind of routine they were doing?


edit: speedy already provided you with the link i was searching for

The universal aptitude for ineptitude makes any human accomplishment an incredible miracle

dudeist skydiver # 666

[lintern 1]

Quote

Here's link to Kallends skydiving resources

This is the power point presentation with the video clip explaining why the 45 degree rule doesnt work.

This is what I was refering to in my original post.

Didnt quite understand the video clip though.

So is the 45 degree rule a load of rubbish then ?

[feuergnom 22]

Quote

So is the 45 degree rule a load of rubbish then ?

definitly

The universal aptitude for ineptitude makes any human accomplishment an incredible miracle

dudeist skydiver # 666

[PhreeZone 15]

Anyone that says to trust the 45 degree rule has never studied physics and in this aspect they need to be ignored. The 45 degree rule does not work in any situation since a group will never reach 45 degree. Exit seperation is to based off the Winds aloft speeds or more specifically the ground speed of the aircraft.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Remster 24]

Quote

The ground speed wasn't very much, maybe 10-15 knots.

This is almost a stand still. You should have given the group 15 seconds. At least.

Consider yourself lucky, and read about exit seperation.

Remster

[dragon2 0]

Besides 5 secs being really short, freeflyers can move around a lot. Are you sure you fell straight down? Did the other 2? A sit or hd can move quite a lot, comparable to a track sometimes Esp above cloud cover it may be hard to see if you're moving a lot or not.

ciel bleu,
Saskia

[lintern 1]

Quote

You should have given the group 15 seconds. At least.

The trouble is if you leave it too long in the door you get people behind you shouting to get out.

I can imagine that if I had waited 15 seconds in the door the people behind me would have been going mad !

It also means that people exiting towrds the end of the jump run could be deep.

(at the DZ where this incident happened the rule is that freeflyers exit before flat flyers)

[mnealtx 0]

Quote

It also means that people exiting towrds the end of the jump run could be deep.

It can - you have to work with the entire load so that everyone gets an acceptable spot. Note I said acceptable, not perfect!

Quote

(at the DZ where this incident happened the rule is that freeflyers exit before flat flyers)

Ouch - bad juju there - John's presentation will show why. Belly flyers are more affected by the winds than free flyers and can pushed over the preceeding group by a combination of wind and not enough separation.

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[speedy 0]

Quote

The ground speed wasn't very much, maybe 10-15 knots.

Do you mean the aircarft ground speed during the drop run or do you mean the wind speeds on the ground?

If that was the aircraft ground speed 30 secs would be too short.

Dave

Fallschirmsport Marl

[billvon 2,435]

>And I couldnt see anyone below me just before deployment because the cloud was from 4000ft to 3500ft.

Problem #1. Do not exit over a cloud. That canopy could have been an airplane with a 50 foot wingspan.

>My question is, I have always left at least 5 seconds seperation and
>never had a problem, so why this time did I come so close ?

Because 5 seconds is never enough separation. Eevn on a light-wind day (ground speed 80mph) 5 seconds gives you only 600 feet; not enough for most jumps. (Most people track at least 200-300 feet on breakoff.)

>I have heard of the 45 degree rule but this is a controversial topic.

Doesn't work.

>So how long should I leave between seperation, if last time 5
>seconds wasnt enough ?

There are many answers to this question.

#1, what most people do, ask someone more experienced or the pilot.

#2, look out the door and watch the ground. When 1000 or 1500 feet have passed, exit.

#3, use time. A good rule of thumb is always wait a _minimum_ of seven seconds. If the upper winds are strong, divide them by 2 and use that number of seconds. (i.e. if the winds are 40kts wait at least 20 seconds.) If this results in openings that are too close, keep increasing the time between groups. The upper-wind forecast isn't always correct.

>The trouble is if you leave it too long in the door you get people behind you shouting to get out.

Ignore them.

[winsor 187]

Quote

NO PRO OR INSTRUCTOR HERE

What were the ground speeds like?

Ground speed is, in and of itself, entirely irrelevant to separation in the air.

Ground speed may be used as a correction factor in a calculation, but is arguably the worst choice you could make if selecting a single parameter upon which to base exit delay.

The "45 degree rule" is actually worse - on a par with voodoo or phrenology - so I do not tend to even consider it.

Quote

What were the uppers doing, etc?

A 5 second blanket rule isn't a good one to go from what I was taught. There are several other variables.

The best parameter upon which to estimate exit delay is the speed of the aircraft with regard to the airmass at opening altitude. This, unfortunately, is sort of a bitch to evaluate in practice.

Quote

Not to mention when you sit do you normally fall down the tube or are you driving/backsliding over the sky.

Pivotal issue.

Quote

Just questions not ripping on you or anything.

Edited to add: At least being that close left you plenty of time to do some CRW

Been there, done that. I am one of the lucky survivors.


Blue skies,

Winsor

[brettski74 0]

Quote

Quote

The ground speed wasn't very much, maybe 10-15 knots.

This is almost a stand still. You should have given the group 15 seconds. At least.

Since he said that he didn't know what the uppers were doing, I think he took this to mean the speed of the ground winds, not the horizontal speed of the aircraft relative to the ground, but yes, do a search and read up on exit separation.

I'd also say that since you were following a two-way, your exit separation probably should have been closer to 7 seconds at a minimum, anyway. You need to give more space to groups to give them space to track away from each other.

Can someone perhaps put the guidelines that are posted in the SkydiveAZ planes on here? They seemed to be a pretty good basis for exit separation based on what I've read so far, unless someone has some better guidelines that can be reasonably implemented by a human standing in the door of a jumpship.

[Remster 24]

Quote

Since he said that he didn't know what the uppers were doing, I think he took this to mean the speed of the ground winds, not the horizontal speed of the aircraft relative to the ground, but yes, do a search and read up on exit separation.

Good point.

To the OP: Groudspeed is the speed at which the plane is flying, relative to the ground.

Winsor: Its not the ideal metric to use, we can agree on that, but, its a good start.

Remster

[JohnRich 4]

Turn 90-degrees to the left or right of the jump-run line as you do your sit-fly. That way if you are sliding across the sky, you will be going perpendicular to other groups, instead of towards them.

[sparkie 0]

good topic, I learnt a lot again. A LOT of newbies like me use 5-6 seconds delay @ our dz. Or so they tell me when the subject comes up. I went on to looking where the group b4 me was but also min. 5-6 secs delay. Looks like I sort of picked up the 45degree method.

After going over the powerpoint presentation I see why this is wrong and will apply some form of ground speed calculation from now on.

Thanks, you just made this newbie less dangerous to the other jumpers at my DZ ;P

[DJL 232]

Quote

Quote

You should have given the group 15 seconds. At least.

The trouble is if you leave it too long in the door you get people behind you shouting to get out.

I can imagine that if I had waited 15 seconds in the door the people behind me would have been going mad !

It also means that people exiting towrds the end of the jump run could be deep.

(at the DZ where this incident happened the rule is that freeflyers exit before flat flyers)

Exit separation needs to be discussed and understood through the plane before exit. JUST LIKE LANDING DIRECTION. If you're scared of people yelling at you to exit then don't get on the plane.

"I encourage all awesome dangerous behavior." - Jeffro Fincher

[ps5601 0]

lintern, as you jump in the UK every lift will have a designated jump master on board (NOTE, what a UK jumper means by a jump master is NOT the same as what an American calls a jump master).

The job of the jump master, among other things is to decide the correct exit order and separation between groups. To do this they should have checked with DZ control and/or the pilot about speed and direction of the upper winds. If you are not sure about what separation to give ASK them. You can ask DZ control and/or the pilot yourself too of course.

As a note, you may have seen 1 group start to climb out 5 seconds after the previous group left, but don't forget that for even a 2-way to get in the door and exit takes a few seconds so the actual EXIT separation is 7 - 8 seconds, especially if there is an exit count. As a solo, your climb out/exit is pretty much non existent so you need to include the extra time in your delay before you exit.

Blue skies

Paul

[divegoddess 0]

newbie here.... but I have been told by more experienced freeflyers that it's never a bad idea to look around before you wave off and pull...I usually do a barrel roll to see if there is anyone in the air space above me and I look directly below me before I wave off.

[JohnRich 4]

Quote

newbie here.... but I have been told by more experienced freeflyers that it's never a bad idea to look around before you wave off and pull...I usually do a barrel roll to see if there is anyone in the air space above me and I look directly below me before I wave off.

True, but you don't want to wait until pull time to find out. You should be keeping track of the other jumpers on your dive as you track off, so that you know where each and every one is. If any of them are unaccounted for, then you check your blind spots too.

It's not uncommon for people to be so intense in their track, that they lock their heads straight on their shoulders, and never look around. The best track is one in which you are rubber-necking in all directions to monitor where others are, so that you can adjust your track if necessary, and ensure that you're clear.

It's reassuring to look left and right and see your tracking partners doing the same thing looking at you - that way everyone is aware of where everyone else is. I get concerned when someone is charging ahead blindly, not paying attention to who is around him.

[Scrumpot 1]

Quote

at the DZ where this incident happened the rule is that freeflyers exit before flat flyers

I know of a few dropzones that do this as a SOP. Each of them that do, has their own specialized reasons, reasoning and/or conditions, it seems.

Can you tell me, does your DZ routinely fly its jumprun either:

- Into the (uppers) wind
- "Downwind" - or,
- Crosswind ?

Have you discussed with them (the DZO, the DZM, the pilot) why it is, for them, they practice this, and their reasoning? Just out of curiosity, if you have, I'd be interested in hearing it.

Thanks.
Blues,
-Grant

coitus non circum - Moab Stone