May 27, 2011, 4:24 AM
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Re: [Squeak] The "45 degree rule" for exit separation DOES NOT WORK
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No, it's not "hard to count aloud." And perhaps you have perfect 1-second interval exit counts.
But not everyone count seconds well, nor does everyone count to the same number. One person's 8-count may be 4 secs. Another may only count to 4 or 5, and even if they count seconds well, this is probably too little time.
With a clock or timer or distance meter, it's not subjective.
This is why western Cutlure is DOOMED
Common sense should be floated on the minerals exchange $1000 per ounce of gold is NOTHING compared to the rare nature of CDF
May 27, 2011, 8:35 AM
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK
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>What's a better model for calculating the separations between groups >(constant separation between each group no matter what they do >freefly/belly solo/2way/3way/4way) for a turbine dz?
Some methods that work:
1) Look down, wait until the plane covers 1000 feet, then go. Runways are good "measuring sticks" for this. (Works provided lower winds are lighter than uppers.)
2) Wait at least 7 seconds. If uppers are high, divide them by 3, wait that number of seconds, then go. (For faster planes divide by 2.)
3) Actually do the math. Separation in feet is (jump run speed + winds at opening altitude) * time between groups in seconds, assuming jump run is into the wind and winds at opening are the same direction as on jump run but lighter. All speeds in feet per second. Make sure you are at LEAST 500 feet from the previous group, more for larger groups.
Try telling this to Skydive AZ. They recently posted 4 secs between solos, 4-6 for small groups. Why make two runs when you can get everyone out in one?? <snip> .
Did you notice that this is based on ground speeds being above a certain level, with additional time required for slower airspeed?
May 27, 2011, 3:10 PM
Post #232 of 364
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Re: [billvon] The "45 degree rule" for exit separation DOES NOT WORK
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Hi Bill,
I guess I wasn't clear that it's a countdown between exits, not getting into the door. I understand the concern about looking at a clock rather than out.
I would hope that people could use it to set cadence and timing and not stare at it, e.g. "it's at 3 or 4 so I'm getting in the door" then doing normal procedures such that it's around 7 secs. Or at simplest a blinking light at 1 per sec to help count cadence. Could be used or not used.
Not trying to over technologize or distract... just faciliate some consistency if this is desired.
LouDiamond (D 25931)
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May 27, 2011, 3:18 PM
Post #233 of 364
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Re: [Remster] The "45 degree rule" for exit separation DOES NOT WORK
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>What's a better model for calculating the separations between groups >(constant separation between each group no matter what they do >freefly/belly solo/2way/3way/4way) for a turbine dz?
Some methods that work:
1) Look down, wait until the plane covers 1000 feet, then go. Runways are good "measuring sticks" for this. (Works provided lower winds are lighter than uppers.)
2) Wait at least 7 seconds. If uppers are high, divide them by 3, wait that number of seconds, then go. (For faster planes divide by 2.)
3) Actually do the math. Separation in feet is (jump run speed + winds at opening altitude) * time between groups in seconds, assuming jump run is into the wind and winds at opening are the same direction as on jump run but lighter. All speeds in feet per second. Make sure you are at LEAST 500 feet from the previous group, more for larger groups.
Try telling this to Skydive AZ. They recently posted 4 secs between solos, 4-6 for small groups. Why make two runs when you can get everyone out in one?? <snip> .
Did you notice that this is based on ground speeds being above a certain level, with additional time required for slower airspeed?
Thank you Remster, you beat me to it. It is statements like these, when taken out of context either intentionally or unintentionally, that false and in some cases dangerous/erroneous information gets put out there as gospel when in fact it is far from the whole truth/story.
May 27, 2011, 3:41 PM
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Re: [LouDiamond] The "45 degree rule" for exit separation DOES NOT WORK
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>What's a better model for calculating the separations between groups >(constant separation between each group no matter what they do >freefly/belly solo/2way/3way/4way) for a turbine dz?
Some methods that work:
1) Look down, wait until the plane covers 1000 feet, then go. Runways are good "measuring sticks" for this. (Works provided lower winds are lighter than uppers.)
2) Wait at least 7 seconds. If uppers are high, divide them by 3, wait that number of seconds, then go. (For faster planes divide by 2.)
3) Actually do the math. Separation in feet is (jump run speed + winds at opening altitude) * time between groups in seconds, assuming jump run is into the wind and winds at opening are the same direction as on jump run but lighter. All speeds in feet per second. Make sure you are at LEAST 500 feet from the previous group, more for larger groups.
Try telling this to Skydive AZ. They recently posted 4 secs between solos, 4-6 for small groups. Why make two runs when you can get everyone out in one?? <snip> .
Did you notice that this is based on ground speeds being above a certain level, with additional time required for slower airspeedground speed?
Thank you Remster, you beat me to it. It is statements like these, when taken out of context either intentionally or unintentionally, that false and in some cases dangerous/erroneous information gets put out there as gospel when in fact it is far from the whole truth/story.
No worries... And before everyone starts again on this, my post should have read like it does now in this reply (bolded)
May 27, 2011, 4:33 PM
Post #235 of 364
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK
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I guess I wasn't clear that it's a countdown between exits, not getting into the door.
Yeah, that's where we have issues in teaching people because the terminology in skydiving isn't that clear. We have to emphasize that we are talking about timing between actual drops or jumps and not 'exit' as in starting to climb out.
May 27, 2011, 4:48 PM
Post #236 of 364
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Re: [Remster] The "45 degree rule" for exit separation DOES NOT WORK
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Try telling this to Skydive AZ. They recently posted 4 secs between solos, 4-6 for small groups. Why make two runs when you can get everyone out in one?? <snip> .
Did you notice that this is based on ground speeds being above a certain level, with additional time required for slower airspeedground speed?
Hi, I didn't mean to take it out of context. Skydive AZ's normally posted min exit time is 5-7 secs if ground speed > 80 knots (more added for less speed and between groups).
I believe the ground speed was 100 knots, so 4 secs may be accounting for the 25% extra speed. I just haven't seen that exit time ever posted and it concerned me a bit (even if it is somehow reasonable) and I took it out on the DZ operators.
(This post was edited by fly67 on May 27, 2011, 4:58 PM)
May 27, 2011, 7:58 PM
Post #239 of 364
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK
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I just haven't seen that exit time ever posted and it concerned me a bit (even if it is somehow reasonable) and I took it out on the DZ operators.
Let's be honest here, with 75 jumps there is a lot you haven't seen before. Instead of posting about it on this website, how about asking someone at the DZ what's going on?
Really, if anything concerns you, make a habit of resolving those concerns before you jump. This time, it would have been explained that light (or non-existant) upper level winds equals a very high ground speed, and so the time between groups is reduced to maintain the overall length of the jumprun. Maybe the next time you have a concern, it will prove to be a real concern that could have lead to a comprimise in safety. In that case, speaking up before you jump is what would prevent you from falling victim to that safety oversight.
Even in the cases where the concern stems from your lack of understanding (by no fault of your own), having nagging fears about possible problems with the skydive is never going to help your performance. So even if your concerns turn out to be unfounded, at least you're not going into a jump thinking about the 'what ifs'.
You're the only one watching out for you (that you know of). Speak up when you're not sure, and make sure you're sending yourself into a good situation.
May 28, 2011, 3:50 PM
Post #241 of 364
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Re: [davelepka] The "45 degree rule" for exit separation DOES NOT WORK
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Hi... The reason I brought it up at all is that Bill said "Wait at least 7 seconds."
I realize the 4 sec separation was probably "reasonable" (I was trying to own up to my mistake). So again, I apologize for a thoughtless off-the-cuff comment.
Also, I double-checked the posted min separation time today and I had it wrong. It is 4-5 seconds and more for groups and slower ground speed.
If I do the math (ground speed): 4 secs @ 80 knots = 540 ft 7 secs @ 80 knots = 945 ft 4 secs @ 100 knots = 676 ft 7 secs @ 100 knots = 1183 ft
What separation "sufficient" or better, safe? (I understand I don't have to take anyone's advice, just curious).
May 29, 2011, 12:47 AM
Post #242 of 364
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Re: [fly67] The "45 degree rule" for exit separation DOES NOT WORK
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What gives the ground speed/distance for safety during deployment in air?? Ground speed does not directly affect separation (only if prev jumper start fly to DZ (usually = follow jump run) just after deployment which bad habbit anyway). Cover the ground with clouds layer, lower than deployment altitude - and there no wind))
Why it is wise to increase the interval between exits in case of High upper wind (low ground speed)? Because you can! You wish from one hand to get as more separation as possible (= more interval) but from the other hand you wish than both first and last jumpers from same run can land in LZ (plane didn't cover so much ground distance). So when ground speed is low you can afford more time and more separation for the same price (ground distance). So there should be reducing of time bw groups when Groundspeed is high (minimum interval should be taken according to AIRspeed), only incresing can be mde when ground speed lover P/S Another issue is wind shifting and drift wich usually gets stronger with higher upperwind, but it's can increase separation as well as decrease it, depending on exit order and other factors)
(This post was edited by NWPoul on May 29, 2011, 3:00 AM)
May 29, 2011, 5:23 AM
Post #244 of 364
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Re: [popsjumper] The "45 degree rule" for exit separation DOES NOT WORK
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(minimum interval should be taken according to AIRspeed),
I don't understand this.
What exactly? You need some horisontal separation on deployment time between you and prev/next jumpers At this moment you and others are in Air not on the ground Separation prvided by traveling of the plane through the air in certain amount of time between jumper's exits
Lets there be wind uphigh with speed 150 ft per sec and plane airspeed will be 150 fps too, so the plane actually doesn't move relative to the earth (groundspeed = 0) but if you exit 10 sec after prev. jumper despite 0 ground distance covered, the distance between you and prev jumper will be ~1500 feet, same as in no wind conditions
but if your ground speed = 0 you can take as much time on exit as you want, without flying away from spot while with zero wind you'l get 1500 feet away with every 10 sec of waiting
(This post was edited by NWPoul on May 29, 2011, 5:26 AM)
May 29, 2011, 6:25 AM
Post #245 of 364
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Re: [NWPoul] The "45 degree rule" for exit separation DOES NOT WORK
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(minimum interval should be taken according to AIRspeed),
I don't understand this.
What exactly? You need some horisontal separation on deployment time between you and prev/next jumpers At this moment you and others are in Air not on the ground Separation prvided by traveling of the plane through the air in certain amount of time between jumper's exits
Lets there be wind uphigh with speed 150 ft per sec and plane airspeed will be 150 fps too, so the plane actually doesn't move relative to the earth (groundspeed = 0) but if you exit 10 sec after prev. jumper despite 0 ground distance covered, the distance between you and prev jumper will be ~1500 feet, same as in no wind conditions
but if your ground speed = 0 you can take as much time on exit as you want, without flying away from spot while with zero wind you'l get 1500 feet away with every 10 sec of waiting
Your theory might work on paper, but in the real world it has one major error - it doesn't account for the difference between the speed of the winds aloft and the speed of the winds at canopy opening altitude.
That difference IS the reason for giving more time between groups when facing into a strong headwind at altitude. When the winds aloft are screaming and the winds at deployment altitude are not, groups WILL BE closer together after deployment for any given amount of time between exits.
Think of it this way - if the aircraft airspeed is equal to that of the headwind, the plane's ground speed is 0. That means no matter how much time jumpers put between exits, THEY WILL ALL OPEN IN THE SAME PLACE because they all GOT OUT IN THE SAME PLACE, assuming they stay in freefall for the same amount of time (more or less time in freefall equals more or less drift distance).
If the winds at deployment altitude are as fast or close to as fast as the uppers, this isn't a problem because by the time the second group gets to that identical opening spot, the first group would have drifted away from that spot because of the wind.
However, when the winds aloft are fast, but the winds at deployment altitude are not - as is often the case - it will cause the jumpers to be closer together at deployment because the first group doesn't drift away from that spot.
It's not usually a good idea in skydiving to know only part of the equation. It can kill you.
May 29, 2011, 11:27 AM
Post #247 of 364
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Re: [NWPoul] The "45 degree rule" for exit separation DOES NOT WORK
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(minimum interval should be taken according to AIRspeed),
I don't understand this.
What exactly? You need some horisontal separation on deployment time between you and prev/next jumpers.
You do understand that when we are talking about exit separation, we are talking about horizontal distance between break-off/opening, right?
...and Chuck's response sums it up nicely.
Quote:
Think of it this way - if the aircraft airspeed is equal to that of the headwind, the plane's ground speed is 0. That means no matter how much time jumpers put between exits, THEY WILL ALL OPEN IN THE SAME PLACE because they all GOT OUT IN THE SAME PLACE, assuming they stay in freefall for the same amount of time (more or less time in freefall equals more or less drift distance).
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Lets there be wind uphigh with speed 150 ft per sec and plane airspeed will be 150 fps too, so the plane actually doesn't move relative to the earth (groundspeed = 0) but if you exit 10 sec after prev. jumper despite 0 ground distance covered, the distance between you and prev jumper will be ~1500 feet, same as in no wind conditions
Looks like you are talking about vertical separation here. Not good.
So you get the vertical separation until opening....then what? If I leave the plane over the same spot in the same winds as the previous jumper I'll be opening in the same spot as he did....what happened to the horizontal separation? (answer: there was non to start with.)
Surely you are not going to depend on that guy to fly an adequate distance away from YOUR opening are you?
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but if your ground speed = 0 you can take as much time on exit as you want, without flying away from spot while with zero wind you'l get 1500 feet away with every 10 sec of waiting
Again, that's a function of GS, not airspeed.
Hopefully, if your GS is 0, you'll take enough time for the previous guy to open and fly an adequate distance away from YOUR opening point (which will be the same a his as already mentioned. Been there, done that.)
(This post was edited by popsjumper on May 29, 2011, 11:32 AM)
May 29, 2011, 11:49 AM
Post #248 of 364
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Re: [popsjumper] The "45 degree rule" for exit separation DOES NOT WORK
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Looks like you are talking about vertical separation here. Not good.
No I talking about horisontal separation ("vertical separation doesn't work")
Groundspeed is 0
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If I leave the plane over the same spot in the same winds as the previous jumper I'll be opening in the same spot as he did..
Yep, at the very moment of your opening, but at this time he'll be taken away (relatively to ground spot, relatively to you he'll just stay at the same distance which you get at exit +/- distance he intentiannaly travel after opening using his canopy)
Again in just strong wind (without wind share) it's just no difference in separation between groups at dep altitude in strong wind or no wind wind condition
Wind shear - agree, make difference... and the bigger shear than bigger difference and agree the stronger upper wind tha usually stronger the wind shear. But wind shear not simple function of upper wing (and ground speed) as well as his affect on the separation) From other hand - who will be bother to do complecated calculation?)
May 29, 2011, 5:25 PM
Post #249 of 364
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Re: [NWPoul] The "45 degree rule" for exit separation DOES NOT WORK
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billvon (D 16479)
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May 29, 2011, 11:27 PM
Post #250 of 364
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Re: [NWPoul] The "45 degree rule" for exit separation DOES NOT WORK
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>(minimum interval should be taken according to AIRspeed)
I'd disagree there. If the airplane is flying into the wind, and the lower winds are less strong than the uppers (which is usually the case) then it is groundspeed that will give you separation, not airspeed. Technically it's (groundspeed + winds at opening) * time between exits in feet per second. Since winds at opening are generally much lower than winds at altitude, a good approximation is groundspeed * time between groups.
>So there should be reducing of time bw groups when Groundspeed is high
Agreed there. Higher groundspeed = less time between groups, lower groundspeed = more time between groups.
). So again, I apologize for a thoughtless off-the-cuff comment. 
