Exit Interval Question

[mjrod 0]

What is a safe exit interval between jumpers exiting an AC. I have 78 MFF jumps and we either exited 3 abreast, or ducks in a row with 1 second intervals, if that. However, since I started sport jumping, the process seems to be a little different. I have seen on the posts 4 second intervals, but wanted some feedback. I think it depends on who you are jumping with and the different types of jumpers going out during the pass...free flyers, CRW, student , tandem, or just jumping. I ask because, I just went through 6 jumps with an instructor to get checked out and get my A license before clearing me to jump solo on the DZ, which is the safe thing to do.

Thanks,

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[Kris 0]

It depends....on the groups (RW, FF, etc), the wind speed, and your ground speed.

Do a search on "exit separation" and you'll find enough material to keep you reading for hours.

Sky, Muff Bro, Rodriguez Bro, and
Bastion of Purity and Innocence!™

[LouDiamond 1]

There are many threads on this topic but to save yourself some time and get a straight answer read the following articles and if you have any questions I'm positive you can get a answer. Just don't associate civilian spotting with what you learned in the Military.

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

[billvon 2,991]

For a very simple rule -

Always leave at least 7 seconds. On an Otter, if the uppers are strong and you are flying into them, and the lower winds are the same direction (which is usually the case) divide the uppers by 2 and leave that amount of time. 20kts = 10 sec. 30kts = 15 sec. If you're on a faster airplane like a King Air divide the uppers by 3.

[nate_1979 9]

wow... From your profile I gather that your home DZ is my home DZ... I dont think i've EVER seen 10-15 seconds between exits, I dont think I've seen 7 second delays except for ones I've done when people in front of me have asked for them... I guess I wont feel so bad when I do wait anymore (I always wait atleast 5 seconds).. Even 5 seconds seems like people behind me get to be in a hurry.

FGF #???
I miss the sky...
There are 10 types of people in the world... those who understand binary and those who don't.

[billvon 2,991]

> I dont think I've seen 7 second delays , , ,

I see it pretty regularly. Remember, it's not the time between exit and climbout, it's the time between group 1's feet leaving the door and group 2's feet leaving the door. If you have a 4-way that waits ahead of the door line, then checks the spot, climbs out, gives the count and goes, it's tough to do that in less than 7 seconds. I agree that on some high-wind days people often don't leave enough time.

>Even 5 seconds seems like people behind me get to be in a hurry.

Yep, people can be impatient.

[mjrod 0]

Yes, initially, the time seems like a bit too much...but your explanation of "feet out the door" makes sense. The relation between MFF and sport jumping is not a different animal, but more a different breed. I watch and learn, but in the end, safety is the common thread. The articles in the linkposted above provide an excellent explanation. The spotting procedures were a bit different, as the pilot was using a CARP (computed air release point) to determine the spot, and it looks like it is the responsibility of he first jumper in the door to verify the spot, although I don't think this is the always the case. Anyway, thanks for the information, as I am trying to transition to sport jumping and some habits are still with me..safety always.

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[LouDiamond 1]

The major differences between the 2 are IMO terminologyand somewhat skill related in that Sport jumping blurs both spotting and calculating winds into on one term and calls it spotting. As a MFF JM I have yet to see a Sport jumper or a pilot calculate the winds using the military method to determine the HARP or even spot the way it is done in the military. The other thing to keep in mind is that MFF ops have people all leaving at the same time with out seperation in groups.So esentially it is all one big group all falling flat dumb and happy. If there are different groups there is a different JM which means you have to do a Go around so he can actually SPOT and release his jumpers.You don't have fall rate issues like FFers, 4way or bigger chunks all leaving at intervals on the same jump run like you do in Sport.

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

[kallend 2,026]

Quote

What is a safe exit interval between jumpers exiting an AC. I have 78 MFF jumps and we either exited 3 abreast, or ducks in a row with 1 second intervals, if that. However, since I started sport jumping, the process seems to be a little different. I have seen on the posts 4 second intervals, but wanted some feedback. I think it depends on who you are jumping with and the different types of jumpers going out during the pass...free flyers, CRW, student , tandem, or just jumping. I ask because, I just went through 6 jumps with an instructor to get checked out and get my A license before clearing me to jump solo on the DZ, which is the safe thing to do.

Thanks,

If you want a comprehensive analysis of WHY, rather than just a simple rule, check my web site:

www.iit.edu/~kallend/skydive/#resources

and download the Powerpoint presentation.

...

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

[mjrod 0]

Exactly, thanks for the response. It helps to get the explanation from someone who has done both and can understand what I am trying to comprehend.

Thanks

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[JohnMitchell 16]

Quote

What is a safe exit interval between jumpers exiting an AC. I have 78 MFF jumps and we either exited 3 abreast, or ducks in a row with 1 second intervals, if that.

The goal in military FF is to have all the jumpers exit close together, open close together, and land close together. In Freefall, you doing nothing but staying stabe, watching altitude, and keeping track of the rest of your team. Sport skydiving, of course, has a lot of maneuvering in FF, whether belly flying, freeflying, or solo jumping. It's not practical or fun to spend your entire jump just watching ot for the guy who jumped before you. That's why we use the delay, to separate the jumpers for safety.

[skr 1]

> What is a safe exit interval between jumpers

That's a complex question.

I think Billvon's answer is the best sound bite
answer I've heard so far, and in the heat of
the action it's hard to remember more than a
sound bite.

I've collected some people's writing on this
question at

http://indra.net/~bdaniels/ftw/index.html

Look at the one called "Dealing with Uppers"
for a start.

Skr

[skr 1]

> What is a safe exit interval between jumpers exiting an AC

Besides Billvon's rule of thumb there is another approach
based on knowing the ground speed after the green light
is on and how much separation you want.

Here's something I posted to a local mailing list:

|----------||-----------|-----------|

|  ground  ||           |           |

|  speed   ||  1000 ft  |  1500 ft  |

|  knots   ||           |           |

|==========||===========|===========|

| 90 knots ||  6-7 sec  |  10 sec   |

|----------||-----------|-----------|

| 70 knots ||  8-9 sec  |  12-13 sec|

|----------||-----------|-----------|

| 50 knots ||  11-12 sec|  17-18 sec|

|----------||-----------|-----------|



Some people like the table in this form:


|----------||-----------|-----------|

|  ground  ||           |           |

|  speed   ||  1500 ft  |  1000 ft  |

|  knots   ||           |           |

|==========||===========|===========|

| 90 knots ||  10 sec   |  6-7 sec  |

|----------||-----------|-----------|

| 70 knots ||  12-13 sec|  8-9 sec  |

|----------||-----------|-----------|

| 50 knots ||  17-18 sec|  11-12 sec|

|----------||-----------|-----------|



I talked to Bryan Burke at Lost Prairie.


He said that Eloy no longer flies jumpruns

at less than 60 knots.


If the uppers are too strong they start flying

various forms of cross wind jumpruns.


----


Also, there is no easy way to make downwind

jumpruns work with both fast and slow fallers

on the same pass.


If you keep the usual exit order, slow fallers

then fast fallers, the slow fallers drift into

the fast faller airspace in freefall.


If you put the fast fallers out first they get

down 40 or 50 seconds before the slow fallers,

and spend most of that flying their canopies

up jumprun, which leaves them right in the

kill zone when the slow fallers arrive.


Skr

Edit to add that the "pre" tag seems to have
stopped working so you have to imagine that
the tables are lined up the way I meant them
to be.

Edit a second time: I went to file a bug report
and when I came back here to get the url of
this thread it came up looking right so you can
color me confused.

Civilization started with showers, it may be ending
with computers :-) :-)

[PhillyKev 0]

Quote

The spotting procedures were a bit different, as the pilot was using a CARP (computed air release point) to determine the spot, and it looks like it is the responsibility of he first jumper in the door to verify the spot, although I don't think this is the always the case.

Ultimately, it is each individual's responsibility to confirm the spot. Get to know the lay of your dz from the air and it's surrounding area and always take a peek for yourself. Obviously you need to rely on others when you're learning what to look for, but ask people to point out landmarks for you in the air and make it a habit to look out the windows during the climb and out the door before you jump.

[LouDiamond 1]

Here is an actual chart that you can laminate and post by the door for reference prior to leaving the A/C once you know what the ground speed is.

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