Forums: Skydiving: Safety and Training:
Calculating the "spot"

 

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Dave-Dornan  (C 110107)

Jun 11, 2012, 9:25 PM
Post #26 of 58 (1019 views)
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Re: [rifleman] Calculating the "spot" [In reply to] Can't Post

Since your profile says you are a uk student you will have to do a low and high spot for your JM1 and B cert.

You will get a brief from your instructors when you get to that stage.

Dave


nigel99  (D 1)

Jun 11, 2012, 9:33 PM
Post #27 of 58 (1015 views)
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Re: [davelepka] Calculating the "spot" [In reply to] Can't Post

In reply to:
Quote:
It should be a prerequisite to C or D license.

Negative ghostrider. WDIs were of use in the days of round canopies when drift could mean the difference between landing on the DZ or not. With a very narrow window of manuverablity, a round canopy needs to be spotted accurately to get the students home.

Squares, on the other hand, can get home from a wide swath of sky, and if you can drop the jumpers anywhere in that area, they can make it back to the DZ. The precision you can gain with a WDI is far more than is needed for modern, steerable canopies.

Consider than an average Otter load might cover a mile or more between the first and last exits, and it's rare for anyone to land off these days. If you want to jump a round, pull out a WDI and give it a shot. Otherwise, when jumping a square, simply look at the wind speed and direction, make your best guess, and then pilot yourself back to the DZ.

Dave I understand why on a turbine it is a pain and that is why few modern jumpers learn to properly spot. But doesn't the lack of skill end up with incidents like Lake Tahoe? Also it seems to me that as a D license holder it would be a good skill to have.


davelepka  (D 21448)

Jun 11, 2012, 9:42 PM
Post #28 of 58 (1012 views)
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Re: [nigel99] Calculating the "spot" [In reply to] Can't Post

 
I wasn't suggesting that jumpers not learn to spot, I was suggesting that making a WDI toss a part of any modern skydiving training is a waste of time and energy. Should we also require jumpers to learn how to pleat their gores?

I'm a huge supporter of situational awareness among jumpers, and that includes the spot, weather, exit orders, aircraft loading etc, all things that do get lost in the mix at bigger DZs where those things are 'done for you'. Much like canopy control, those are things that jumpers should really take more of an interest in, as those are areas that are directly related to their safety and well-being. Sadly, many jumpers are content to take the minimum level of training required in those areas, and won't persue any further study on their own.


mjosparky  (D 5476)

Jun 11, 2012, 10:12 PM
Post #29 of 58 (1006 views)
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Re: [davelepka] Calculating the "spot" [In reply to] Can't Post

In reply to:
Negative ghostrider. WDIs were of use in the days of round canopies when drift could mean the difference between landing on the DZ or not. With a very narrow window of manuverablity, a round canopy needs to be spotted accurately to get the students home.

WDIs were dropped at 2,500 feet directly over the target. The plane would circle until the WDI landed. The spot is the same distance up wind from the target as the WDI is down wind. They only work for low level jumps; they do not give you any indication of upper winds.

Sparky
Attachments: Untitled.jpg (18.5 KB)


sundevil777  (D License)

Jun 11, 2012, 10:13 PM
Post #30 of 58 (1006 views)
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Re: [faulknerwn] Calculating the "spot" [In reply to] Can't Post

In reply to:
If you go to skydive midwests website they have an app which lets you enter the winds aloft and ground winds and it will do the math. We've been using it for a couple years now and it works quite well.

Very nice (spot calculator)

http://www.skydivemidwest.com/...one/spot-calculator/


erdnarob  (D 364)

Jun 12, 2012, 10:51 AM
Post #31 of 58 (966 views)
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Re: [rifleman] Calculating the "spot" [In reply to] Can't Post

Hi Rifleman

You mention you are a student...maybe in sciences or applied sciences ! Anyway, few years ago I have made a program to calculate the spot using a Graphing calculator HP 48 GX. If you are interested by it, I will send you the program and a sample of calculation which validates it. On my program every step is explained.

To summarize, my program results is an addition of distance vectors.

I also made a grid on a Google Map aerial picture of my DZ with the center being the landing area. Concentric circles are drawn every 500 ft and radials every 10 degrees. Therefore when you calculate the spot (given in distance and direction) you can easily find it on the picture.


(This post was edited by erdnarob on Jun 12, 2012, 10:55 AM)


hillson  (D 33134)

Jun 12, 2012, 2:53 PM
Post #32 of 58 (939 views)
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Re: [rifleman] Calculating the "spot" [In reply to] Can't Post

I've found that is easier to figure out where you don't want to get out / land and go from there. With wind data and an aerial photo of your DZ it is pretty easy to figure out where you want to be and more importantly where you don't.


cavscout73  (C 40414)

Jun 12, 2012, 3:46 PM
Post #33 of 58 (923 views)
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Re: [rifleman] Calculating the "spot" [In reply to] Can't Post

In reply to:
Is there some kind of formula for calculating the spot from wind charts/forecasts? If so, could someone please tell me what it is, as I'd like to be able to figure it out for myself.

Many Thanks
Not sure if its text book or good for all but i was told right after i came off student status to get the winds aloft for the given altitude and use 1/4 mile for every 10 mph of wind. Its gotten me back every time..


nigel99  (D 1)

Jun 12, 2012, 6:02 PM
Post #34 of 58 (900 views)
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Re: [davelepka] Calculating the "spot" [In reply to] Can't Post

In reply to:
I wasn't suggesting that jumpers not learn to spot, I was suggesting that making a WDI toss a part of any modern skydiving training is a waste of time and energy. Should we also require jumpers to learn how to pleat their gores?

I'm a huge supporter of situational awareness among jumpers, and that includes the spot, weather, exit orders, aircraft loading etc, all things that do get lost in the mix at bigger DZs where those things are 'done for you'. Much like canopy control, those are things that jumpers should really take more of an interest in, as those are areas that are directly related to their safety and well-being. Sadly, many jumpers are content to take the minimum level of training required in those areas, and won't persue any further study on their own.
Thanks for clarifying. It is tough because we all 'learn' to spot for our A license. But with big planes and GPS all you are really doing is popping your head out the door for a few seconds. At some point in the sport you should be required to do a non gps spot.


dninness  (D 19617)

Jun 12, 2012, 6:03 PM
Post #35 of 58 (900 views)
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Re: [sundevil777] Calculating the "spot" [In reply to] Can't Post

http://www.skyjump.com/thespot

(Thats is for Pepperell. Matt Veno, the wizard code monkey behind it, has made it available to any DZ that wants to put it on their website: http://www.flyingchipmunk.com/...generally-available/)

Speaking from experience, it takes the forecasted winds aloft, so as per usual, "no plan survives first contact with the enemy." All the usual disclaimers apply.

EDIT: Sorry, now with clicky goodness


(This post was edited by dninness on Jun 12, 2012, 6:35 PM)


SansSuit  (D 21554)

Jun 12, 2012, 6:20 PM
Post #36 of 58 (905 views)
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Re: [rifleman] Calculating the "spot" [In reply to] Can't Post

The spot is only important if you care where you land. Wink


skyjumpenfool  (Student)

Jun 12, 2012, 7:27 PM
Post #37 of 58 (886 views)
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Re: [SansSuit] Calculating the "spot" [In reply to] Can't Post

Landing on the DZ is highly over rated! Tongue

and, their not called "wind drift indicators" any more. The PC term these days is "students". Smile


Squeak  (E 1313)

Jun 12, 2012, 11:15 PM
Post #38 of 58 (858 views)
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Re: [skyjumpenfool] Calculating the "spot" [In reply to] Can't Post

In reply to:
Landing on the DZ is highly over rated! Tongue

and, their not called "wind drift indicators" any more. The PC term these days is "students". Smile

I call it 1st loadSlySlySlySly


JackC1

Jun 13, 2012, 12:59 AM
Post #39 of 58 (851 views)
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Re: [Squeak] Calculating the "spot" [In reply to] Can't Post

I always watch a WiDI load before manifesting.


erdnarob  (D 364)

Jun 13, 2012, 9:36 AM
Post #40 of 58 (807 views)
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Re: [skyjumpenfool] Calculating the "spot" [In reply to] Can't Post

I disagree completely with you that landing at the right place is over rated. Landing at the right place is safer. Anywhere outside the landing area can be hazardous. Any objects can be found on the ground and often hidden by high grass : piece of concrete with steel bars protruding, gap, irrigation channel, rusted pieces of metal...not counting roads, hydrolines, fences, houses...anything...name it.
You never know when you can be caught off gard by high winds and when the spot can be missed for various reasons.

Now about wind drift indicators. It seems old fashion but throwing wind rift indicators is the sure way to evaluate where the spot is.
No wonder why it is still a requirement or should be for the A license. People rely too much on their canopy performances but soon or later found themselves in a situation where they cannot make it back.
On a recent school football field parachute demo, the winds were marginal blowing at near 15 knots which is about the limit for a parachute demo. Fortunately, I had two wind drifts (red and gold). They landed, as expected, quite far away but from 2000 ft in the air I could easily evaluate the spot. People at the ground told me later that when they saw me leaving the airplane, they never thought I could come back. But the spot is the spot and I was back over the football field relatively fast and had the time to prepare for a nice landing in front of the spectators. Imagine a sec that I have missed the football field. The spectators would consider me as a zero instead of hero. Hundred of pictures have been taken. But because of the use of wind drift indicators, people on the ground will have a good opinion of skydivers and skydiving in general.

Knowing how to drop a wind drift indicator is important for any unusual winds situation and is a must for a parachute demo. But if you want always to rely on other people, never be on the first load of the day by high winds and decide to never get your PRO rating you are almost right.


(This post was edited by erdnarob on Jun 13, 2012, 12:27 PM)


JohnMitchell  (D 6462)

Jun 13, 2012, 11:32 AM
Post #41 of 58 (800 views)
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Re: [erdnarob] Calculating the "spot" [In reply to] Can't Post

You, Dave and I are all very experienced and we've all thrown our share of WDI's. With that said, I'll go with Dave's assessment that all square rigs have made starting the day with a WDI unnecessary.

Maybe for a tight demo, extreme weather or tight DZ with students, maybe, but I don't think I'll be hucking one at my present DZ.


popsjumper  (D 999999999)

Jun 13, 2012, 12:15 PM
Post #42 of 58 (789 views)
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Re: [rifleman] Calculating the "spot" [In reply to] Can't Post

In reply to:
What I meant was that I'd like to be able to calculate the spot for myself even though atm I'm having to trust my instructors to put me out at the right point.

How will I know if the spot is right if I have no idea how to figure it out? (6 years in the military have taught me that mistakes can and do happen, even with qualified personnel)

You are all over it, rifleman. Learn to do the math.
It could mean the difference some time.

Keep in mind that the example in the SIM is very basic. Learn that and then if you really want to be better at it, insert some changes in
-wind directions and speeds at different altitudes,
-jump run into the wind or some degrees of crosswind or even with the wind
-other.

By looking at varying conditions, you'll discover some very important issues regarding determining exit point, opening point AND separation at opening.


popsjumper  (D 999999999)

Jun 13, 2012, 12:28 PM
Post #43 of 58 (783 views)
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Re: [davelepka] Calculating the "spot" [In reply to] Can't Post

In reply to:
Now say there are 10mph winds blowing out of the north. If you were south of the DZ, those winds would stop you from gliding very far, so you won't want to open up very far south of the DZ, let's say less than 1/4 mile.
And we can calculate that. We don't have to guess.

In reply to:
On that same day, you could get out much further upwind (north) of the DZ, and have the winds puch you back to the DZ, let's say you could be 2 miles upwind.
And we can calculate that. We don't have to guess.


In reply to:
....so anywhere in there is your 'spot'.
...and what about the resto of the load?

In reply to:
Store all of this info in your memory banks and use to....
adjust for the inaccuracies of winds aloft charts and changes in wind direction and speed as the day goes on.


In reply to:
In the end, it's a bunch of educated guesswork.
Ummmm, for clarification:
Yes, we can only get good data out if we out good data in...and that goes for guesswork, too.


In reply to:
It's not uncommon for there to be an informal morning 'meeting' between the pilot and a senior jumper/staff memeber where they guess at the spot.
Would you agree that doing the calculations would be a better start than "guessing"?

Sometimes students only see us doing the mental work in our heads, using previous experiences, and think we are "guessing".


sundevil777  (D License)

Jun 13, 2012, 2:28 PM
Post #44 of 58 (764 views)
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Re: [JohnMitchell] Calculating the "spot" [In reply to] Can't Post

The value of developing the ability (art) of observing the weather conditions, displaying a thoughtful gaze for several seconds, and then confidently pronouncing where the spot should be cannot be underestimated!


JohnMitchell  (D 6462)

Jun 13, 2012, 7:24 PM
Post #45 of 58 (736 views)
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Re: [sundevil777] Calculating the "spot" [In reply to] Can't Post

You and I go way back. I know you know how to spot.Cool


skyjumpenfool  (Student)

Jun 14, 2012, 11:25 AM
Post #46 of 58 (667 views)
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Re: [JohnMitchell] Calculating the "spot" [In reply to] Can't Post

What Jon and Pops said above... start by studying, observing, calculating, etc? With that comes experience, with experience comes the ability to "guess/know" where the spot should be.

@ erdnarob ... Um, that was an attempt at sarcasm. Smile However, I am in no way afraid of landing off. Partly because I jump where there is an abundance of open space, partly because I've been there - done that. The ability (or at least the lack of fear) to land off can make some decisions much easier. And, decision fear = indecision = late decision = bad decision.
Unsure


JohnMitchell  (D 6462)

Jun 14, 2012, 11:50 AM
Post #47 of 58 (657 views)
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Re: [skyjumpenfool] Calculating the "spot" [In reply to] Can't Post

Good point.

Sooner or later every jumper will land off. How you prepare yourself mentally and practice for that day will determine the outcome.Smile


popsjumper  (D 999999999)

Jun 14, 2012, 10:16 PM
Post #48 of 58 (627 views)
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Re: [skyjumpenfool] Calculating the "spot" [In reply to] Can't Post

In reply to:
The ability (or at least the lack of fear) to land off can make some decisions much easier. And, decision fear = indecision = late decision = bad decision.

Worth repeating...several times

May I add?
Lack of knowledge = decision fear....


MikeJD  (D 10605)

Jun 15, 2012, 5:20 AM
Post #49 of 58 (609 views)
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Re: [JohnMitchell] Calculating the "spot" [In reply to] Can't Post

In reply to:
I'll go with Dave's assessment that all square rigs have made starting the day with a WDI unnecessary.

Not to mention the fact that in general we're exiting higher than we used to. Winds upstairs can be howling and can be completely at odds with those on the ground. Combine that with the improved range of square canopies and I'd guess that freefall drift is at least as significant now as canopy drift.

And you're not going to learn anything much about freefall drift by throwing a WDI from opening height. :)


popsjumper  (D 999999999)

Jun 15, 2012, 2:41 PM
Post #50 of 58 (580 views)
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Re: [nigel99] Calculating the "spot" [In reply to] Can't Post

In reply to:
Thanks for clarifying. It is tough because we all 'learn' to spot for our A license. But with big planes and GPS all you are really doing is popping your head out the door for a few seconds. .
...and THAT is not spotting. It's only a small part of the process.


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