kelpdiver 2 #51 October 18, 2004 Quote No, I have often been impressed by how many people of my acquaintance have advanced degrees (MS & PhD) yet never got beyond the level of expertise at the basics that they achieved during Freshman year. They may be able to set up second-order partial differential equations just fine, but if faced with, say, rotational dynamics, through which they struggled to get a C, they would do well to show C level comprehension even now. .... I no longer teach Physics for a living. If you are an engineer, you should have the study tools to find the readily available resources and figure it out for yourself. It's pretty basic stuff. So, in short, you'd rather insult than explain. That sounds like academia all right. It appeared that your argument was that separation only depended on winds at opening altitudes, and that uppers were irrelevent. And something about 1000ft of separation. But you kept it rather vague, and unexplained, with lots of wiggle room. I'll go see now if your notes are more clear. Quote Share this post Link to post Share on other sites
winsor 186 #52 October 18, 2004 It appeared that your argument was that separation only depended on winds at opening altitudes, and that uppers were irrelevant. Nope. Separation is a simple function of exit speed with regard to the airmass at a particular altitude. The minimum is typically the airmass at opening altitude (with an upwind jumprun) or at exit altitude (with a downwind jumprun). The speed of the uppers with regard to the ground is a consideration for spotting, but is irrelevant in and of itself for separation. These are related, yet very different, concepts. And something about 1000ft of separation.Quote I picked a nice, round number as an example. It didn't occur to me that it might pose a conceptual challenge. [But you kept it rather vague, and unexplained, with lots of wiggle room. Quote You have obviously mistaken me for someone who cares one way or another. I'll go see now if your notes are more clear.Quote Knock yourself out. If you can improve upon them, by all means do so. Blue skies, Winsor Quote Share this post Link to post Share on other sites
billvon 2,406 #53 October 18, 2004 >So, in short, you'd rather insult than explain. Would both of you cut it out! Quote Share this post Link to post Share on other sites
kelpdiver 2 #54 October 18, 2004 He entered a thread in the "Safety and TRAINING" forum rather with brisk words and when asked to elaborate, said it wasn't his problem or care. There's something wrong with that. If he doesn't care, why post? End of harsh words. Quote Share this post Link to post Share on other sites
winsor 186 #55 October 18, 2004 Quote He entered a thread in the "Safety and TRAINING" forum rather with brisk words and when asked to elaborate, said it wasn't his problem or care. There's something wrong with that. If he doesn't care, why post?Quote The not caring part is regarding your analysis. To a great extent it really doesn't matter whether the reason why someone gets out with sufficient separation is physically valid - so long as they somehow provide for that separation. If you simply read numbers off a table and give the indicated exit count, that can work. You don't need to perform a detailed analysis every time you exit the airplane, and doing so won't eliminate rogue variables such as people tracking hell for leather at odd altitudes and pitching high, etc.. Thus, there is a difference between knowing HOW and knowing WHY. When people who have a pretty good handle on the how part of the deal conclude that they therefore understand why, I have a problem with it. Particularly when they're wrong. If someone gives a good count of 10 before jumping, I'm fine with that. That's the safety part of the deal. If they do it because the moon is in Aquarius and they saw a cat on top of a red car that day, I would rather not know. I am primarily concerned with the fact that they stay the hell away from me in the air. If someone wants to postulate an invalid model as the physical basis upon which they base their decision, I can't be bothered to hold their hand and lead them through it. It has been done to death on numerous occasions, and the information is available to anyone who takes the time to look. The "Safety and Training" part is, again, give sufficient time between groups to ensure adequate separation, and exit the airplane such that you can land somewhere safely. If you limit your focus to those issues, you should do okay. Blue skies, Winsor Quote Share this post Link to post Share on other sites MWGemini 0 #56 October 18, 2004 QuoteThe "Safety and Training" part is, again, give sufficient time between groups to ensure adequate separation, and exit the airplane such that you can land somewhere safely. If you limit your focus to those issues, you should do okay. Maybe I'm just not comprehending, but I don't think you have explained how to determine what "sufficient time between groups" is. I'll have to read your notes, but since that is the ONLY link you've posted in the 3 pages of this thread, either we are all blithering idiots and have failed to derive any meaning from your posts, or you have failed to explain your position well enough. I'm here to learn, but if you can callously insult professionals and colleagues, I'm sure that I am completely meaningless to you. Mike Quote Share this post Link to post Share on other sites christelsabine 1 #57 October 18, 2004 Why don't you just enter "Safety" in the menu? That could help you a lot, and you will not only need links. dudeist skydiver # 3105 Quote Share this post Link to post Share on other sites winsor 186 #58 October 19, 2004 QuoteQuoteThe "Safety and Training" part is, again, give sufficient time between groups to ensure adequate separation, and exit the airplane such that you can land somewhere safely. If you limit your focus to those issues, you should do okay. Maybe I'm just not comprehending, but I don't think you have explained how to determine what "sufficient time between groups" is. Okay, the Cliff's Notes version is that you want groups far enough apart that they are not LIKELY to infringe upon each other's airspace. Here we're going to ignore the very real factor of groups sliding like a bastard in freefall, people breaking off early and tracking toward the DZ and so forth. If you factor those issues in, you'll want a separate pass per group. As an aside, we are concerned with what is happening in the air - the ground is an issue for spotting. If you look at the ability of a competent skydiver to track, assuming a 3,500 foot breakoff and 2,500 foot opening, you can expect the diameter of the group to approach 1,000 feet. The most important altitude to have full separation is opening altitude. This is where the radius of influence of a given group is at its maximum, and it is generally where the paths of the groups are at their most convergent. However, the most elusive parameter of interest is wind speed at opening altitude, so it is usually easiest to work around it. If it's not available, you can't waste too much time fretting. To start with a calm day calculation, figuring 90 knots true airspeed (150 feet per second) gives you a little over 6 seconds between groups for your 1,000 feet of separation all the way to the ground. On a day with 40 knot uppers and 10 knots at opening altitude, you have to increase your delay to maintain 1,000 feet of separation at opening altitude. The 90 knots true airspeed of the aircraft, minus the 30 knots difference between the winds at altitude and at opening altitude, gives 60 knots, or 100 feet per second. You now have to wait 10 seconds between each "go!" to get the same 1,000 feet between groups at opening altitude. A couple of caveats: 1) Vertical separation is NOT separation. Sometimes parachutes open much higher - or lower - than expected. 2) Sufficient is a judgment call. 1,000 feet between groups decreases the likelihood of one group intruding on the airspace of another, but does not guarantee it. If you have a handle on the variables, you can adjust accordingly. If you're following a 16-way out, you should assume they are going to break high and track like hell; give them PLENTY of time. A series of solos where nobody's tracking at breakoff can work with a couple of seconds between jumpers. Anyhow, the discussion of spotting and separation is sure to crop up on a regular basis, but the physics don't change. Once you understand what's involved, you need only pay attention and use your judgment. Blue skies, Winsor Quote Share this post Link to post Share on other sites pilotdave 0 #59 October 19, 2004 So THATS why dogs lick their balls! Sorry. I'll shut up now. Dave Quote Share this post Link to post Share on other sites speedy 0 #60 October 19, 2004 QuoteOn a day with 40 knot uppers and 10 knots at opening altitude, blowing in the same direction..... you may now continue Dave Fallschirmsport Marl Quote Share this post Link to post Share on other sites winsor 186 #61 October 19, 2004 QuoteQuoteOn a day with 40 knot uppers and 10 knots at opening altitude, blowing in the same direction.... Good point. That's one problem with the short form. On a day with 40 knot uppers and 10 knots at opening altitude IN THE OPPOSITE DIRECTION, you have to increase your delay to maintain 1,000 feet of separation at opening altitude. The 90 knots true airspeed of the aircraft, minus the 50 knots difference between the winds at altitude and at opening altitude, gives 40 knots, or 67 feet per second. You now have to wait *15* seconds between each "go!" to get the same 1,000 feet between groups at opening altitude. Note here that reversing the direction of the 10 knot breeze altitude results in 50% more time being necessary to achieve the same separation. Reversal of wind direction with altitude is more common than people often suppose. I will often have a headwind at 2,500 feet, but a significant tailwind at 10,500 feet (or vice-versa). Blue skies, Winsor Quote Share this post Link to post Share on other sites speedy 0 #62 October 19, 2004 QuoteThat's one problem with the short form. That is why people should go to Kallends web site and download the stuff there and study it. The information is out there! read it. There is no need for Winsor to try and post here in a short form what has already been posted a 1000 times before. B.T.W I am not posting the link as it has been posted many times dropzone.com search for the link Dave Fallschirmsport Marl Quote Share this post Link to post Share on other sites Prev 1 2 3 Next Page 3 of 3 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. Paste as plain text instead Only 75 emoji are allowed. × Your link has been automatically embedded. Display as a link instead × Your previous content has been restored. Clear editor × You cannot paste images directly. Upload or insert images from URL. Insert image from URL × Desktop Tablet Phone Submit Reply 0 Go To Topic Listing
MWGemini 0 #56 October 18, 2004 QuoteThe "Safety and Training" part is, again, give sufficient time between groups to ensure adequate separation, and exit the airplane such that you can land somewhere safely. If you limit your focus to those issues, you should do okay. Maybe I'm just not comprehending, but I don't think you have explained how to determine what "sufficient time between groups" is. I'll have to read your notes, but since that is the ONLY link you've posted in the 3 pages of this thread, either we are all blithering idiots and have failed to derive any meaning from your posts, or you have failed to explain your position well enough. I'm here to learn, but if you can callously insult professionals and colleagues, I'm sure that I am completely meaningless to you. Mike Quote Share this post Link to post Share on other sites
christelsabine 1 #57 October 18, 2004 Why don't you just enter "Safety" in the menu? That could help you a lot, and you will not only need links. dudeist skydiver # 3105 Quote Share this post Link to post Share on other sites
winsor 186 #58 October 19, 2004 QuoteQuoteThe "Safety and Training" part is, again, give sufficient time between groups to ensure adequate separation, and exit the airplane such that you can land somewhere safely. If you limit your focus to those issues, you should do okay. Maybe I'm just not comprehending, but I don't think you have explained how to determine what "sufficient time between groups" is. Okay, the Cliff's Notes version is that you want groups far enough apart that they are not LIKELY to infringe upon each other's airspace. Here we're going to ignore the very real factor of groups sliding like a bastard in freefall, people breaking off early and tracking toward the DZ and so forth. If you factor those issues in, you'll want a separate pass per group. As an aside, we are concerned with what is happening in the air - the ground is an issue for spotting. If you look at the ability of a competent skydiver to track, assuming a 3,500 foot breakoff and 2,500 foot opening, you can expect the diameter of the group to approach 1,000 feet. The most important altitude to have full separation is opening altitude. This is where the radius of influence of a given group is at its maximum, and it is generally where the paths of the groups are at their most convergent. However, the most elusive parameter of interest is wind speed at opening altitude, so it is usually easiest to work around it. If it's not available, you can't waste too much time fretting. To start with a calm day calculation, figuring 90 knots true airspeed (150 feet per second) gives you a little over 6 seconds between groups for your 1,000 feet of separation all the way to the ground. On a day with 40 knot uppers and 10 knots at opening altitude, you have to increase your delay to maintain 1,000 feet of separation at opening altitude. The 90 knots true airspeed of the aircraft, minus the 30 knots difference between the winds at altitude and at opening altitude, gives 60 knots, or 100 feet per second. You now have to wait 10 seconds between each "go!" to get the same 1,000 feet between groups at opening altitude. A couple of caveats: 1) Vertical separation is NOT separation. Sometimes parachutes open much higher - or lower - than expected. 2) Sufficient is a judgment call. 1,000 feet between groups decreases the likelihood of one group intruding on the airspace of another, but does not guarantee it. If you have a handle on the variables, you can adjust accordingly. If you're following a 16-way out, you should assume they are going to break high and track like hell; give them PLENTY of time. A series of solos where nobody's tracking at breakoff can work with a couple of seconds between jumpers. Anyhow, the discussion of spotting and separation is sure to crop up on a regular basis, but the physics don't change. Once you understand what's involved, you need only pay attention and use your judgment. Blue skies, Winsor Quote Share this post Link to post Share on other sites
pilotdave 0 #59 October 19, 2004 So THATS why dogs lick their balls! Sorry. I'll shut up now. Dave Quote Share this post Link to post Share on other sites
speedy 0 #60 October 19, 2004 QuoteOn a day with 40 knot uppers and 10 knots at opening altitude, blowing in the same direction..... you may now continue Dave Fallschirmsport Marl Quote Share this post Link to post Share on other sites
winsor 186 #61 October 19, 2004 QuoteQuoteOn a day with 40 knot uppers and 10 knots at opening altitude, blowing in the same direction.... Good point. That's one problem with the short form. On a day with 40 knot uppers and 10 knots at opening altitude IN THE OPPOSITE DIRECTION, you have to increase your delay to maintain 1,000 feet of separation at opening altitude. The 90 knots true airspeed of the aircraft, minus the 50 knots difference between the winds at altitude and at opening altitude, gives 40 knots, or 67 feet per second. You now have to wait *15* seconds between each "go!" to get the same 1,000 feet between groups at opening altitude. Note here that reversing the direction of the 10 knot breeze altitude results in 50% more time being necessary to achieve the same separation. Reversal of wind direction with altitude is more common than people often suppose. I will often have a headwind at 2,500 feet, but a significant tailwind at 10,500 feet (or vice-versa). Blue skies, Winsor Quote Share this post Link to post Share on other sites
speedy 0 #62 October 19, 2004 QuoteThat's one problem with the short form. That is why people should go to Kallends web site and download the stuff there and study it. The information is out there! read it. There is no need for Winsor to try and post here in a short form what has already been posted a 1000 times before. B.T.W I am not posting the link as it has been posted many times dropzone.com search for the link Dave Fallschirmsport Marl Quote Share this post Link to post Share on other sites
