Exit separation on downwind JR

[Frenchy68 0]

In the case of an A/C doing a 180° fly over (an Otter in this case), hence heading downwind, do the exit seperation rules of upwind JR still apply all the same?
In my case, last week end, a full load of 2 to 3 way Free Flyers. Fly over (180°) with still 2X3 way head downers & a solo head down to go before my friend and I went (2 way belly down pulling high). Since I wasn't sure, I left 8 seconds separation after the solo HD before we jumped. Made for a very painful upwind cross country to land in the same zip code as the DZ!
Any insight would be greatly appreciated.

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."

[CanuckInUSA 0]

Think about this for a second. On a downwind jump run, is the airplane flying at a faster or a slower ground speed? It's flying across the ground at a faster ground speed (obviously the ground speed will depend upon the winds aloft) and thus not as much seperation is needed. It's still a good idea to combine time and the 45 degree rule, but not as much time is needed on the downwind leg as it would be required when the airplane is flying into the wind.

Try not to worry about the things you have no control over

[Frenchy68 0]

That's what I thought. However, how much difference is there? For the sake of arguments, let's say a 3 way belly down goes ahead of a solo head down. How much of a difference from an upwind JR?
Just trying to get insight.

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."

[CanuckInUSA 0]

If the airplane(s) you are jumping from are equiped with a GPS (many nowadays are), ask the pilot what your ground speed is. Pretty soon you will learn what is fast and what is slow for the airplane and you will then have a better idea as to what sort of separation to give. This applies to the normal jump run as well. On calm winds aloft days, not as much time is needed between groups. But on strong winds aloft days, tons of time between groups may be needed. And in the cases where your airplane(s) are not equiped with a GPS, you can still check out the forecasted winds aloft by checking out an aviation website (like AOPA's) ahead of time if you are so inclined.

Try not to worry about the things you have no control over

[speedy 0]

Here is a mine of useful information.
http://www.iit.edu/~kallend/skydive/#resources

Download the powerpoint presentaion with the freefall sim. I know it's a lot to read, but if you read it and make a true attempt to understand it, then you can answer your questions yourself.

BTW, I consider doing 180° with the aircraft on the jump run to be dangerous. Before you drop the second group, the first group should have landed. The 1st group does not have enough time with a 180° turn.

Dave

Fallschirmsport Marl

[rainman 0]

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It's still a good idea to combine time and the 45 degree rule

It's never a good idea to use the 45 degree rule if you want to be safe.

Please refer to John Kallend's website for more information.

Blue skies,

Rainman

[winsor 187]

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Think about this for a second. On a downwind jump run, is the airplane flying at a faster or a slower ground speed? It's flying across the ground at a faster ground speed (obviously the ground speed will depend upon the winds aloft) and thus not as much seperation is needed. It's still a good idea to combine time and the 45 degree rule, but not as much time is needed on the downwind leg as it would be required when the airplane is flying into the wind.

A) What your ground speed measures has precious little to do with separation in the air. Minimum time between groups is still minimum time between groups; a function of air speed. This is especially true for a downwind jump run.

B) The temperature has even less to do with separation than does ground speed.


Blue skies,

Winsor

[johnny1488 1]

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What your ground speed measures has precious little to do with separation in the air

What should have been said is that in "most cases" the ground speed is a good quick indicator and is much easier to explain quickly than the airmass at opening altitude. As long as you dont have wind going in 2 totally different directions, the ground speed is a good way to tell if you need to give "more" or "less" time between groups.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[speedy 0]

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The temperature has even less to do with separation than does ground speed.

I find temperature has a lot to do with seperation. In winter jumpers tend to stay as far away from the door as possible to keep warm. This means when it's their turn to exit they have to first walk the whole lenght of the plane (taking a few extra seconds) before they jump. In summer they are all just desperate to get out of the hot aircraft. Exit seperation is reduced.

I never did believe that the critcal temperature was 45° though.

Dave

Fallschirmsport Marl

[johnny1488 1]

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BTW, I consider doing 180° with the aircraft on the jump run to be dangerous. Before you drop the second group, the first group should have landed. The 1st group does not have enough time with a 180° turn.

When we do a 180 at my dz (2, sometimes 3 otters running) we offset the jump run at least 1/4 to 1/2 mile. We generally dont have high openers in the first groups so there is a bit of vertical seperation also.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[CanuckInUSA 0]

I guess you're not a very good reader are you? Since when did I say that one must solely rely on a 45 degree rule? I said time and the 45 degree rule can be used in combination when trying to judge a jump run one isn't used to such as a downwind jump run.

Try not to worry about the things you have no control over

[speedy 0]

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I said time and the 45 degree rule

I would suggest you replace the 45 degree rule with...

Time and counting how many windows the aircraft has, used in combination....

On an upwind jump run, count the doors as well.

Dave

Fallschirmsport Marl

[CanuckInUSA 0]

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The temperature has even less to do with separation than does ground speed.

Once again people are accusing me of saying something I did NOT say. Temperature? Huh? When did I say that the temperature has anything to do with jump run and exit separation?

As far as air speed is concerned (assuming the pilot flies by the numbers, which they should), the airplane is going to be flying the same air speed regardless of what direction the airplane is flying. The track across the ground is dependent on the winds aloft and how fast or how slow the airplane is making progress along jump run. I'm not really advocating that people give little exit separation when dealing low winds aloft, but I am saying that it's important to recognize when the winds are strong that extra time be given. That is why time and the 45 degree rule do work together. Yes I can see that the 45 degree rule alone has it's flaws. But unless people know how fast or how slow the airplane is tracking across jump run, they really don't know how much time to give each group.

Now if you're talking about separation being dependent upon air apeed because on one jump you're jumping out of a slow aircraft (a Cessna) and on the next jump you're jumping out of a C-130 (obviously a much faster aircraft), well then you're talking apples and oranges and how often does that happen for most jumpers at their regular DZs (outside of something like the WFFC which has many different aircraft).

[speedy 0]

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Yes I can see that the 45 degree rule alone has it's flaws.

Flaws????? It is totally useless!

Edited to add: Have you not read the thread in this forum titled the 45 degree rule?

Dave

Fallschirmsport Marl

[CanuckInUSA 0]

What part of the word combination do you NOT understand? And hasn't everything I said started with the word time? I am done with this thread and done with people who are quoting me out of context!!!

Try not to worry about the things you have no control over

[johnny1488 1]

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That is why time and the 45 degree rule do work together.

I've gotta agree with speedy also. The 45 degree rule has absolutley no use at all in any seperation use. It is dangerous and should be abandoned all together. Time is the only factor to determine exit seperation. How you determine that time can be gotten from a few sources but they basicly come from one source. The difference between airspeed on jumprun and airspeed at opening altitude. The 45 degree rule tells you absolutely nothing.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[speedy 0]

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What part of the word combination do you NOT understand?

I think that combination in your context means using both time and the 45° rule together.

Using time is a good idea, combining (i.e.using together) the 45° rule with time is a bad idea.

edit for spilling

Dave

Fallschirmsport Marl

[CanuckInUSA 0]

Okay even though I said I was done (which I will be soon), you don't seem to quote me out of context so here's my take.

Yes I agree that the 45 degree rule alone isn't right. So one is in the door and they count ... whatever it is they were counting to ... then do they blindly just jump or do they look and if they look what happens if the group ahead of them isn't really moving all that much ... well they counting so according to some of the people here it's okay to jump right? I say no!!! If time and the group ahead of you hasn't tracked off (say 45 say something else) you don't jump, you continue to wait. Vertical seperation doesn't really mean much if I have a reserve ride and fall in on top of the group in front of me. Horizontal separation is everything and this is a factor of time in the door and using our eyes to ensure that we aren't jumping before we should because we didn't really properly understand how much the aircraft might be tracking across jump run.

People remember what the original poster was asking in this thread. How much seperation is needed on a downwind jump run. The answer is dependent upon the winds aloft and generally it's not as much time.

I realize that some of you are just interested in making another "this guy doesn't know shit" argument because he mentioned the god-aweful 45 degree rule. But go back to the original responses and read what was said. Not as much time is needed when the aircraft is hauling ass due to low winds aloft and extra time is needed when the winds aloft are strong.

Try not to worry about the things you have no control over

[speedy 0]

Let me ask you a question
Do you think the angle of the jumpers exiting the plane after 5 seconds will be different for ....
a) the plane is dropping in 60 knot head winds
b) the plane is dropping in 10 knot head winds

Dave

Fallschirmsport Marl

[johnny1488 1]

When I jump, instead of looking at the group out before me, I look more at the spot and how much ground the plane has covered since they left (assuming the wind direction is fairly constant). Looking at the group before you is way too subjective cause they're moving, you're moving. Way too hard to tell. I look at the ground and for air traffic.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[speedy 0]

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I look at the ground and for air traffic.

And I look at the cloud cover and for air traffic

Dave

Fallschirmsport Marl

[CanuckInUSA 0]

What do I look for when I'm at the door. Yes I look at my spot and how fast or how slow it changes. Yes I look for aircraft below me, yes I look at the cloud cover and yes I watch the group in front of me. But what does all this have to do with the topic at hand "Exit separation on a downwind jump run"?

I'm done ... at least for now as I need to jump in the shower and get my sorry ass off to the salt mines (work) because "The Man" doesn't like it when I'm late for work.

Try not to worry about the things you have no control over

[johnny1488 1]

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But what does all this have to do with the topic at hand "Exit separation on a downwind jump run"?

When I look out and see we are doing mach5 over the ground, I dont wait that long to get out.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[speedy 0]

Canuck chose not answer my question
My guess is he things the angles will be different.

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When I look out and see we are doing mach5 over the ground, I dont wait that long to get out.

At mach 5 I would stay in the aircraft, that's way to fast to exit.

Dave

Fallschirmsport Marl

[pilotdave 0]

I hate the idea of downwind jumpruns. The biggest problem, in my opinion, is that canopies from one group are flying toward the next group of freefallers. With an upwind jump run, the plane is flying away from the airport. Each group opens farther and farther away, while the previous group of open canopies is moving farther from the opening point, toward the airport.

With a downwind jumprun, the plane is flying toward the airport at the exit point. Open canopies from one group are flying toward the opening point of the next group.

Better plan separation really carefully to avoid one groups opening point from coinciding with the previous group's position under canopy.

Dave