exit seperation-newbies don't get pressured..

[cvfd1399 0]

Can you post a few numbers for different jump run ground speeds, and their seperation numbers using regular twin otter air speeds? You could use that as a starting guide for everyone to use. Instead of everyone giving a general 6 seconds on a fast upper or a slow upper day which is wrong b/c the faster upper leads to less ground speed and seperation per second. Ie..(using a normal twin otter air speed into a headwind jumprun)
05k uppers is___ jumprun ground speed= 5 sec delay
10k uppers is___ jumprun ground speed=6 sec delay
15k uppers is___jumprun ground speed=7 sec delay
so on and so forth.
That way if you have a ___groundspeed you can explain that for this many seconds you count you attain+or-__ feet of seperation from the group that just exited.
I know that there are times that this needs to be adjusted, but this would help new people like me get the understanding that we are looking for distance between exiting groups, and the only way to do that is to let the aircraft take us away before we jump. Also that a aircraft that always goes 90k on jumprun does not move across the ground the same speed every time due to the winds it is flying in be it headwind/tailwind jumprun. What I am thinking is it is easier to understand for first timers that way. Then you can throw in all the other variables.(spelling for all ) Also I was told that total jump run should not last over 60 seconds from first climbout to last jumper away. I don't know at what ground speed that was figured at. Can anyone give the total jump run time for the above statement with different uppers. Ie higher uppers means a longer timed jumprun B/C of less groundspeed.

Edit: I know that it sounds like a student which I am. The more I put what I think I know out and get feedback the more I know that I know or don't know what I thought I knew.

• Quote

[billvon 3,091]

>Can you post a few numbers for different jump run ground speeds. . .


An Otter typically flies at 80kts IAS. That's about 160 feet per second over the ground for no wind, or 800 feet separation (which is minimum separation for two 4-ways) if you leave 5 seconds.


So:

Upper wind speed FPS over the ground
0 160
20 120
40 85
60 55

A good rule of thumb - for a normal speed aircraft (Otter, Caravan) always leave at least 7 seconds. If uppers are greater than 15 knots, divide the uppers by 2 and use that number of seconds. So, 20 knots - 10 seconds. 30 knots - 15 seconds.


For faster aircraft (King Airs etc) divide by 3. This will work 90% of the time.

[Professor 0]

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>
An Otter typically flies at 80kts IAS.

IIRC, an otter indicating 80kts, at 13500 is something more like 100kts ground speed.

Ted
Like a giddy school girl.

[kallend 2,129]

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Can you post a few numbers for different jump run ground speeds, and their seperation numbers using regular twin otter air speeds?

Take a look at

[url]www.iit.edu/~kallend/skydive/

and click on:

"Powerpoint presentation on separation with freefall sim"

...

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

[cvfd1399 0]

I got you sim and play with it from time to time. I will give the numbers a look thanks.


Thanks billvon too for the numbers

[billvon 3,091]

>IIRC, an otter indicating 80kts, at 13500 is something more like
>100kts ground speed.

80KIAS = 92KTAS = 105MPH= 156FPS groundspeed at 12,500 feet.

[goose491 0]

Quote

...Waiting an arbitrary amount of time, and ignoring the safety jumpers behind so you can have a warm fuzzy feeling, is crap.

Well, I've been hosed before by groups ahead of me taking too long. Whereby I may find it annoying... I would never say that they are hindering or ignoring my safety. My safety is my responsibility and nobody is forcing me to leave the aircraft if the spot is long.

Just worth some consideration... if you land out, it's NOT the responsibility of the group that may have hosed you.


On the other hand, to the original poster: Talk to the culprits, you could be taking it to seriously. I myself have been guilty of the old "Come on man!!! Get out!!!!". Usually in good spirits though. You know, teasing the 4way team that takes half an hour to set up. Sometimes, the entire plane full starts counting out loud once the green lights up. The team don't like that much

My Karma ran over my Dogma!!!

[Professor 0]

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I would never say that they are hindering or ignoring my safety. My safety is my responsibility and nobody is forcing me to leave the aircraft if the spot is long.

Just worth some consideration... if you land out, it's NOT the responsibility of the group that may have hosed you.

They are potentially increasing your chances for an off landing, or a low return to the DZ, which is less safe. How is that not bad? Agreed, everyone is responsible for themselves first, and I could land with the plane, and eat the $18, or ask for go around after go around, but neither of those is good either. There should be no reason that you can't get everyone out of a normal jump aircraft on a normal jump run with safe separation and a good spot.

Billvon:
Just when I thought I had ya. What formula did you use to get 92 kts? I found a couple of references, but they gave me slightly different numbers, 96 and 99.

Ted
Like a giddy school girl.

[Frenchy68 0]

As an option to eating the $18, wouldn't pulling higher work? Isn't it safer than disregarding exit separation basic rules? Just wondering.

Nick

"For once you have tasted Absinthe you will walk the earth with your eyes turned towards the gutter, for there you have been and there you will long to return."

[Professor 0]

Probably, but I'd never really advise someone to make a habit of pulling at an unplanned altitude and without telling the rest of the load. I guess in theory, though, proper exit separation should ensure that this wouldn't be a problem. At least not for people in other groups.

And pulling high still sucks, and shouldn't be neccesary.

Ted
Like a giddy school girl.

[goose491 0]

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They are potentially increasing your chances for an off landing, or a low return to the DZ, which is less safe.

No they aren't. My point is, the guy in front of you can take half an hour to leave... if you get out after him and end up half an hours worth of hosed... it's not his fault for hosing you... it's yours for getting out.

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There should be no reason that you can't get everyone out of a normal jump aircraft on a normal jump run with safe separation and a good spot.

No arguments here. I agree whole heartedly. We're talking about taking 6 seconds and being rushed at like 2 seconds though... not right. Plain and simple.

My Karma ran over my Dogma!!!

[Professor 0]

Quote

No they aren't. My point is, the guy in front of you can take half an hour to leave... if you get out after him and end up half an hours worth of hosed... it's not his fault for hosing you... it's yours for getting out.

OK, fine. How about this: It's his fault for placing you in the position of having to chose between getting out long, riding down, pulling high, or asking for a go around. Do you not agree that everyone has a responsibility to get out at the right time?

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We're talking about taking 6 seconds and being rushed at like 2 seconds though... not right. Plain and simple.

As I've already said, 6 seconds is fine. And bitching at people after 2 seconds is shitty. Actually take 6 seconds, and I'll never have anything to say. But remember, if you're climbing a group out, it'll probably take 4 seconds, so you'll be outside by the time people start bitching anyway.

Ted
Like a giddy school girl.

[goose491 0]

Quote

But remember, if you're climbing a group out, it'll probably take 4 seconds, so you'll be outside by the time people start bitching anyway.

...and that's when you should climb partially back in, point to your ear and scream "What?!? I can't hear!".

My Karma ran over my Dogma!!!

[skr 1]

> Can you post a few numbers for different jump run ground speeds

Down at the bottom of

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

is an article called "Dealing with Uppers" that
has some ground speed vs seconds numbers
plus a discussion of where they came from.

http://indra.net/~bdaniels/ftw/sg_skr_dealing_1_uppers.html

is the URL.

Here's a table for common situations:

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

|  ground  ||           |           |

|  speed   ||  1000 ft  |  1500 ft  |

|  knots   ||           |           |

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

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

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

| 70 knots ||  8-9 sec  |  1-13 sec |

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

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

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

I talked to Bryan Burke at Lost Prairie and he said
that at Eloy they no longer fly jumpruns at less than
60 knots ground speed.

When the uppers get stronger than that they start
flying various forms of cross wind jump runs.

Skr