jdfreefly 1 #26 February 26, 2004 eames - thanks for the reply....I love these forums! Out of 22 posts, only 2 were actually a response to the original question and they were both by the same guy! Way to go dude! You just got 5 points on the Daless respect-o-meter! In reply to your formula, I am actually looking for something complex. I want to come up with something that will work no matter what direction or magnitude the wind is blowing, what direction or magnitude the airplane is moving...the only exception should be the fact that for a 16 way, you need to leave more time. I was really hoping people like Winsor and Kallend would pipe up. I figure Kallend's simulation is allready half way there...it's only problem is it makes too many assumptions. I would like to come up with something that has as few assumptions as possible and outputs a useable result - ie "give 6 seconds between groups"..etc. I was really hoping, due to the nature of my request, the "45 degree" therom would not rear its ugly head in this thread....I am obviously way too much of an optimist. Methane Freefly - got stink? Quote Share this post Link to post Share on other sites
pccoder 0 #27 February 26, 2004 Is that why the strong blast of air? PcCoder.net Quote Share this post Link to post Share on other sites
diverdriver 5 #28 February 26, 2004 QuoteIs that why the strong blast of air? Most likely. Quote Share this post Link to post Share on other sites
eames 0 #29 February 26, 2004 QuoteI am actually looking for something complex. I want to come up with something that will work no matter what direction or magnitude the wind is blowing, what direction or magnitude the airplane is moving... The second one is definitely as complex as it needs to be. It would work no matter what direction or magnitude the wind is blowing or what direction or magnitude the airplane is moving. You just have to plug in the right numbers. -Jason Quote Share this post Link to post Share on other sites
murps2000 86 #30 February 26, 2004 ***By the way, that other King Air is simply not faster. *** I never jumped it, but I've seen it sitting on the tarmac at Titusville. It sure didn't look any faster. Quote Share this post Link to post Share on other sites
kallend 1,623 #31 February 26, 2004 Quote Y'know, I remember someone saying "you never should have said the 45 degree thing can help at all, because someone's going to say that Bill Von said it was OK to use!" And I thought they were being silly; no one would take it _that_ much out of context. Oh well. I'll know better next time than to make comments like that. That someone was me, and it was based on having been a teacher since 1968. There will ALWAYS be someone who misunderstands.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
pilotdave 0 #32 February 26, 2004 Quotemichaelmullins - I have experienced that real strong blast of wind feeling that some other's have mentioned on this thread in the King Air at Titusville too. At the same time I was hearing the stall warning going off in the cockpit before stepping out the door. What was going on there? Any chance it was a gear warning horn? I have no idea if a kingair has this, but some planes have a horn that goes off if the throttle is idled with the gear up. Dave Quote Share this post Link to post Share on other sites
dnewcomer 0 #33 February 26, 2004 QuoteQuoteJohn, Aaaaaahhhhhhhhh!!!! THE 45 DEGREE RULE DOES NOT WORK!!!!! HOW MANY TIMES DO WE HAVE TO POST THIS. YOU WILL NOT ATTAIN A 45 DEGREE FROM EXIT EVER!!! PLEASE STOP SAYING THIS!! Chris, I hope you didn't hurt yourself typing that post. I've been told by experienced skydivers out there (often with many thousands of jumps) about the virtues of the "45 deg. rule." OK...they're wrong. Obviously not everyone is reading the threads on DZ.com. I guess this proves the adage, "Knowledge and wisdom don't necessarily come with experience; sometimes experience comes alone." It's amazing how many so-called experts can disagree on a major issue -- but none of them ever seems to be in doubt about his or her opinion. I believe a few upstart engineers have even recently questioned the 100 yr old theory of how an airfoil creates lift. (My God...the Holy Grail of aerodynamics!!! Isn't anything sacred?) There will probably never be a "precise" formula that can accommodate all variables to accurately determine exit separation on all jump runs. The necessary information is imprecise by its very nature. It would be easier to write the formula needed to send a landing craft to Mare Imbrium. The best anyone can do will have to be a generality that gives a reasonable margin of safety for all situations -- whatever that may be. Dave Quote Share this post Link to post Share on other sites velo90 0 #34 February 26, 2004 QuoteI would like to come up with something that has as few assumptions as possible and outputs a useable result - ie "give 6 seconds between groups"..etc. Once you have come up with your useable result, say 6 seconds, who is going to count them? I have seen people count 6 seconds in 3 seconds and a 4-way team that should give 10 seconds take 20 seconds to set up in the door. Quote Share this post Link to post Share on other sites tombuch 0 #35 February 26, 2004 QuoteThere will probably never be a "precise" formula that can accommodate all variables to accurately determine exit separation on all jump runs. The necessary information is imprecise by its very nature. It would be easier to write the formula needed to send a landing craft to Mare Imbrium. The best anyone can do will have to be a generality that gives a reasonable margin of safety for all situations -- whatever that may be. Dave My contribution to the issue was listed on The Ranch web site late last season and can be found at: http://ranchskydive.com/safety/tb_article15.htm. It's designed as a general discussion with a specific set of numbers to define time between groups under limited conditions. Tom Buchanan S&TA Instructor, AFF, SL, IAD, Tandem Author JUMP! Skydiving Made Fun and EasyTom Buchanan Instructor Emeritus Comm Pilot MSEL,G Author: JUMP! Skydiving Made Fun and Easy Quote Share this post Link to post Share on other sites kallend 1,623 #36 February 26, 2004 QuoteQuoteQuote I believe a few upstart engineers have even recently questioned the 100 yr old theory of how an airfoil creates lift. (My God...the Holy Grail of aerodynamics!!! Isn't anything sacred?) This falls into the "angels on the head of a pin" category of debate. You can calculate lift two different ways, and they both come up with the same answer. So which is "correct"? Does downwash create pressure differences, or do pressure differences crete downwash? The 100 year old theory worked just fine to design the wings of P51s, Spitfires, Otters, C182s, etc. As for separation, we do know how to calculate it exactly if we have all the variables available, and we can PROVE absolutely that the 45 degree "rule" is bogus. Any disagreement revolves around how best to deal with the situation when we don't have exact values for all the variables, and generally all the suggestions on these recent threads work OK, 'cos they all have some margin for error built in..... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites billvon 2,396 #37 February 26, 2004 Attached is an Excel spreadsheet that calculates exit separation. The left columns are the data to be entered. Enter winds at exit and deployment altitudes in ktas and degrees. Heading can be true or magnetic as long as you use the same scheme throughout. Enter aircraft true airspeed (ktas, not kias) and heading of the aircraft. Enter the number of seconds you will leave between groups. On the right side are the results. You'll see aircraft groundspeed along jump run in ktas and fps, and the amount of wind down the jumprun line at opening altitude. The final number is total separation in feet. JK, feel free to check this and make sure I didn't reverse a sign or something. Quote Share this post Link to post Share on other sites kallend 1,623 #38 February 27, 2004 QuoteAttached is an Excel spreadsheet that calculates exit separation. The left columns are the data to be entered. Enter winds at exit and deployment altitudes in ktas and degrees. Heading can be true or magnetic as long as you use the same scheme throughout. Enter aircraft true airspeed (ktas, not kias) and heading of the aircraft. Enter the number of seconds you will leave between groups. On the right side are the results. You'll see aircraft groundspeed along jump run in ktas and fps, and the amount of wind down the jumprun line at opening altitude. The final number is total separation in feet. JK, feel free to check this and make sure I didn't reverse a sign or something. Looks good to me.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites kallend 1,623 #39 February 27, 2004 OK, here's a shot at a calculator to give a recommended separation between groups based on group size (your group and the preceding group). Assuming normal tracking, fall down the tube without backsliding, etc. This is more judgement than science- feedback please.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites jdfreefly 1 #40 February 27, 2004 Thanks to Kallend and Bill for actually answering the question....on a side note, Tom , that is a great article. Maybe I can print out about 20 copies and scatter them around the dz on safety day.... I fully understand that there is no silver bullet that will give us an absolute answer to life the universe and everything....However, we should be able to come up with something that will work in 99 percent of the cases involved. Hopefully, Bill's formulas and Kallend's can combine to create that solution. Then from now on, when someone mentions the 45 degree rule, they can be pointed to this. I know some will still insist that they are right and all the good sience in the world can't compete with blind devotion to myth. I wish the world wasn't that way, but as my grand papy always said, "Why don't you wish in one hand, and crap in the other, then tell me what you have." Methane Freefly - got stink? Quote Share this post Link to post Share on other sites jdfreefly 1 #41 February 27, 2004 Okay, I copied Bill's spreadsheet and modified it so you can do it either way, enter all the relevant data in one, including time between groups and it will tell you how much separation that produces(thanks Bill). The second one you enter all the relevant data including the desired amount of separation and it will tell you how many seconds to allow between exits. Combine that with Kallend's estimates on required separation for different sized groups and we nearly have everything we need for a great first draft. Once again though, I would like to make something that takes a few more things into account..see my original post...but this is a great starting point. Do you guys feel that this is good enough? I guess my question is this: The spreadsheet really doesn't take into acount how much push is created by the wind during freefall and how that effects groups falling at different speeds. Is that so small as to have an insignificant effect on these formulas? Does that assume people put in conservative numbers...obviously someone trying to use this to put groups so close as to only allow a 100 foot margine for error will receive bad results. Bill? Kallend? Thanks again for the useful input. Methane Freefly - got stink? Quote Share this post Link to post Share on other sites dnewcomer 0 #42 February 27, 2004 B-- I believe this thread represents the best reason DZ.com exists. Too bad everyone who ever exits a plane to make a skydive is not going to read it. The idea of making copies of this info for wide distribution at DZ's on Safety Day is a good one. Maybe the USPA should send a memo or email out to all DZ's, DZ owner/operators, and S&TA's emphasizing that the "45 Deg. Rule" is invalid and should never be used or recommended as a technique for determining exit separation distance. It would seem that this should be part of their goal to maximize the safety of the sport. D-- Quote Share this post Link to post Share on other sites pccoder 0 #43 February 27, 2004 Could be, but I remember someone mentioning on the plane that it was the stall warning. But, they could be wrong. PcCoder.net Quote Share this post Link to post Share on other sites kallend 1,623 #44 February 27, 2004 QuoteQuotemichaelmullins - I have experienced that real strong blast of wind feeling that some other's have mentioned on this thread in the King Air at Titusville too. At the same time I was hearing the stall warning going off in the cockpit before stepping out the door. What was going on there? Any chance it was a gear warning horn? I have no idea if a kingair has this, but some planes have a horn that goes off if the throttle is idled with the gear up. Dave My Mooney does this. Not that it has any relevance at all to a King Air.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites kallend 1,623 #45 February 27, 2004 QuoteOkay, I copied Bill's spreadsheet and modified it so you can do it either way, enter all the relevant data in one, including time between groups and it will tell you how much separation that produces(thanks Bill). The second one you enter all the relevant data including the desired amount of separation and it will tell you how many seconds to allow between exits. Combine that with Kallend's estimates on required separation for different sized groups and we nearly have everything we need for a great first draft. Once again though, I would like to make something that takes a few more things into account..see my original post...but this is a great starting point. Do you guys feel that this is good enough? I guess my question is this: The spreadsheet really doesn't take into acount how much push is created by the wind during freefall and how that effects groups falling at different speeds. Is that so small as to have an insignificant effect on these formulas? Does that assume people put in conservative numbers...obviously someone trying to use this to put groups so close as to only allow a 100 foot margine for error will receive bad results. Bill? Kallend? Thanks again for the useful input. Where is it? It wasn't attached to the post. Put my bit at the beginning and you have it all in one place. If you do that and send it to me, I can add some stuff to account for fall rate differences unless someone beats me to it.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites winsor 186 #46 February 27, 2004 QuoteQuoteThere will probably never be a "precise" formula that can accommodate all variables to accurately determine exit separation on all jump runs. The necessary information is imprecise by its very nature. It would be easier to write the formula needed to send a landing craft to Mare Imbrium. The best anyone can do will have to be a generality that gives a reasonable margin of safety for all situations -- whatever that may be. Dave My contribution to the issue was listed on The Ranch web site late last season and can be found at: http://ranchskydive.com/safety/tb_article15.htm. It's designed as a general discussion with a specific set of numbers to define time between groups under limited conditions. Tom Buchanan S&TA Instructor, AFF, SL, IAD, Tandem Author JUMP! Skydiving Made Fun and Easy With all due respect, I don't believe you have the temerity to post an article that makes serious reference to the 45 degree myth. The 45 degree approach is worse than useless. Anyone paying attention can demonstrate its invalidity as a trivial exercise. Anyone who thinks it has merit is surviving on luck alone. Regardless of all the ratings you put forth, you just flunked Freshman Physics. Do your homework, and fix your website. You have dangerous misinformation posted therein. Blue skies, Winsor Quote Share this post Link to post Share on other sites billvon 2,396 #47 February 27, 2004 >OK, here's a shot at a calculator to give a recommended separation >between groups based on group size . . . It looks good for any group over 6 people, but I'd add discrete limits below that. I think I might also change the scaling factor to 250. Solo: 800 feet min (since solos are often low experienced jumpers who tend to slide) 2-6 way: 1000 feet min (since I don't believe in people tracking in any direction other than away from the center, and up to 6 ways generally break off at the same altitude and hence have the same spread) Quote Share this post Link to post Share on other sites kallend 1,623 #48 February 27, 2004 Quote>OK, here's a shot at a calculator to give a recommended separation >between groups based on group size . . . It looks good for any group over 6 people, but I'd add discrete limits below that. I think I might also change the scaling factor to 250. Solo: 800 feet min (since solos are often low experienced jumpers who tend to slide) 2-6 way: 1000 feet min (since I don't believe in people tracking in any direction other than away from the center, and up to 6 ways generally break off at the same altitude and hence have the same spread) Thanks - will make changes. As I said, this is judgement, not physics.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites tombuch 0 #49 February 27, 2004 Quote With all due respect, I don't believe you have the temerity to post an article that makes serious reference to the 45 degree myth. The 45 degree approach is worse than useless. Anyone paying attention can demonstrate its invalidity as a trivial exercise. Anyone who thinks it has merit is surviving on luck alone. Unfortunately, the 45 degree rule is out there and needs to be addressed. It DOES work if there is no wind at all, and that needs to be understood. It doesn't work if there is wind. Many people (here at dropzone.com and at my drop zone, believe in the 45 degree rule, so we can't ignore it. Heck, many instructors are still teaching the 45 degree rule, so our customers come to us believing it works. Please reread that part of the web feature:QuoteThe concept of watching a group leave and slide back under the tail to 45 degrees behind the airplane seems to work well with no wind, but it provides only a single separation standard that is difficult to quantify or vary for different types of groups that require more or less space. If there is lots of wind, the 45 degree standard can provide considerably less separation than desired. In fact, if we imagine an airplane flying directly into a wind so great that the plane isn't moving, it will still be possible to achieve the 45 degree standard as jumpers are initially blown back, but every jumper will be getting out over exactly the same place on the ground, they will be blown back along exactly the same path, and will open at the same place with no separation at all. The separation doesn't suddenly disappear when the airplane stops covering ground in the wind, but rather deteriorates as the wind speed increases, and the 45 degree rule can't be expected to compensate. The crux of the feature (available at: http://ranchskydive.com/safety/tb_article15.htm is to base separation on time, NOT the 45 degree rule. We can argue about if the critical wind is at jump altitude, or opening altitude, but for simplicity I needed to advance a basic policy that is simple to understand and implement under most conditions. With 22 people on each plane making their own decisions at a drop zone with "no rules" we need an easy solution. On those few days with weird winds our pilots tend to spot accordingly, and we try to get folks thinking as best we can. So, with all due respect, we can't actually ignore the 45 degree rule, we need to teach around it, and provide a well reasoned alternative. Tom Buchanan Instructor (AFF, SL, IAD, Tandem) S&TA Author JUMP! Skydiving Made Fun and EasyTom Buchanan Instructor Emeritus Comm Pilot MSEL,G Author: JUMP! Skydiving Made Fun and Easy Quote Share this post Link to post Share on other sites pilotdave 0 #50 February 27, 2004 QuoteIt DOES work if there is no wind at all, and that needs to be understood. Ummm...you sure? Be more specific. Does it work no matter what the airspeed is? How about group size? I think to make a statement like that is just silly. It simply doesn't work. If you want to address it, say that it simply doesn't work. 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velo90 0 #34 February 26, 2004 QuoteI would like to come up with something that has as few assumptions as possible and outputs a useable result - ie "give 6 seconds between groups"..etc. Once you have come up with your useable result, say 6 seconds, who is going to count them? I have seen people count 6 seconds in 3 seconds and a 4-way team that should give 10 seconds take 20 seconds to set up in the door. Quote Share this post Link to post Share on other sites
tombuch 0 #35 February 26, 2004 QuoteThere will probably never be a "precise" formula that can accommodate all variables to accurately determine exit separation on all jump runs. The necessary information is imprecise by its very nature. It would be easier to write the formula needed to send a landing craft to Mare Imbrium. The best anyone can do will have to be a generality that gives a reasonable margin of safety for all situations -- whatever that may be. Dave My contribution to the issue was listed on The Ranch web site late last season and can be found at: http://ranchskydive.com/safety/tb_article15.htm. It's designed as a general discussion with a specific set of numbers to define time between groups under limited conditions. Tom Buchanan S&TA Instructor, AFF, SL, IAD, Tandem Author JUMP! Skydiving Made Fun and EasyTom Buchanan Instructor Emeritus Comm Pilot MSEL,G Author: JUMP! Skydiving Made Fun and Easy Quote Share this post Link to post Share on other sites
kallend 1,623 #36 February 26, 2004 QuoteQuoteQuote I believe a few upstart engineers have even recently questioned the 100 yr old theory of how an airfoil creates lift. (My God...the Holy Grail of aerodynamics!!! Isn't anything sacred?) This falls into the "angels on the head of a pin" category of debate. You can calculate lift two different ways, and they both come up with the same answer. So which is "correct"? Does downwash create pressure differences, or do pressure differences crete downwash? The 100 year old theory worked just fine to design the wings of P51s, Spitfires, Otters, C182s, etc. As for separation, we do know how to calculate it exactly if we have all the variables available, and we can PROVE absolutely that the 45 degree "rule" is bogus. Any disagreement revolves around how best to deal with the situation when we don't have exact values for all the variables, and generally all the suggestions on these recent threads work OK, 'cos they all have some margin for error built in..... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites billvon 2,396 #37 February 26, 2004 Attached is an Excel spreadsheet that calculates exit separation. The left columns are the data to be entered. Enter winds at exit and deployment altitudes in ktas and degrees. Heading can be true or magnetic as long as you use the same scheme throughout. Enter aircraft true airspeed (ktas, not kias) and heading of the aircraft. Enter the number of seconds you will leave between groups. On the right side are the results. You'll see aircraft groundspeed along jump run in ktas and fps, and the amount of wind down the jumprun line at opening altitude. The final number is total separation in feet. JK, feel free to check this and make sure I didn't reverse a sign or something. Quote Share this post Link to post Share on other sites kallend 1,623 #38 February 27, 2004 QuoteAttached is an Excel spreadsheet that calculates exit separation. The left columns are the data to be entered. Enter winds at exit and deployment altitudes in ktas and degrees. Heading can be true or magnetic as long as you use the same scheme throughout. Enter aircraft true airspeed (ktas, not kias) and heading of the aircraft. Enter the number of seconds you will leave between groups. On the right side are the results. You'll see aircraft groundspeed along jump run in ktas and fps, and the amount of wind down the jumprun line at opening altitude. The final number is total separation in feet. JK, feel free to check this and make sure I didn't reverse a sign or something. Looks good to me.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites kallend 1,623 #39 February 27, 2004 OK, here's a shot at a calculator to give a recommended separation between groups based on group size (your group and the preceding group). Assuming normal tracking, fall down the tube without backsliding, etc. This is more judgement than science- feedback please.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites jdfreefly 1 #40 February 27, 2004 Thanks to Kallend and Bill for actually answering the question....on a side note, Tom , that is a great article. Maybe I can print out about 20 copies and scatter them around the dz on safety day.... I fully understand that there is no silver bullet that will give us an absolute answer to life the universe and everything....However, we should be able to come up with something that will work in 99 percent of the cases involved. Hopefully, Bill's formulas and Kallend's can combine to create that solution. Then from now on, when someone mentions the 45 degree rule, they can be pointed to this. I know some will still insist that they are right and all the good sience in the world can't compete with blind devotion to myth. I wish the world wasn't that way, but as my grand papy always said, "Why don't you wish in one hand, and crap in the other, then tell me what you have." Methane Freefly - got stink? Quote Share this post Link to post Share on other sites jdfreefly 1 #41 February 27, 2004 Okay, I copied Bill's spreadsheet and modified it so you can do it either way, enter all the relevant data in one, including time between groups and it will tell you how much separation that produces(thanks Bill). The second one you enter all the relevant data including the desired amount of separation and it will tell you how many seconds to allow between exits. Combine that with Kallend's estimates on required separation for different sized groups and we nearly have everything we need for a great first draft. Once again though, I would like to make something that takes a few more things into account..see my original post...but this is a great starting point. Do you guys feel that this is good enough? I guess my question is this: The spreadsheet really doesn't take into acount how much push is created by the wind during freefall and how that effects groups falling at different speeds. Is that so small as to have an insignificant effect on these formulas? Does that assume people put in conservative numbers...obviously someone trying to use this to put groups so close as to only allow a 100 foot margine for error will receive bad results. Bill? Kallend? Thanks again for the useful input. Methane Freefly - got stink? Quote Share this post Link to post Share on other sites dnewcomer 0 #42 February 27, 2004 B-- I believe this thread represents the best reason DZ.com exists. Too bad everyone who ever exits a plane to make a skydive is not going to read it. The idea of making copies of this info for wide distribution at DZ's on Safety Day is a good one. Maybe the USPA should send a memo or email out to all DZ's, DZ owner/operators, and S&TA's emphasizing that the "45 Deg. Rule" is invalid and should never be used or recommended as a technique for determining exit separation distance. It would seem that this should be part of their goal to maximize the safety of the sport. D-- Quote Share this post Link to post Share on other sites pccoder 0 #43 February 27, 2004 Could be, but I remember someone mentioning on the plane that it was the stall warning. But, they could be wrong. PcCoder.net Quote Share this post Link to post Share on other sites kallend 1,623 #44 February 27, 2004 QuoteQuotemichaelmullins - I have experienced that real strong blast of wind feeling that some other's have mentioned on this thread in the King Air at Titusville too. At the same time I was hearing the stall warning going off in the cockpit before stepping out the door. What was going on there? Any chance it was a gear warning horn? I have no idea if a kingair has this, but some planes have a horn that goes off if the throttle is idled with the gear up. Dave My Mooney does this. Not that it has any relevance at all to a King Air.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites kallend 1,623 #45 February 27, 2004 QuoteOkay, I copied Bill's spreadsheet and modified it so you can do it either way, enter all the relevant data in one, including time between groups and it will tell you how much separation that produces(thanks Bill). The second one you enter all the relevant data including the desired amount of separation and it will tell you how many seconds to allow between exits. Combine that with Kallend's estimates on required separation for different sized groups and we nearly have everything we need for a great first draft. Once again though, I would like to make something that takes a few more things into account..see my original post...but this is a great starting point. Do you guys feel that this is good enough? I guess my question is this: The spreadsheet really doesn't take into acount how much push is created by the wind during freefall and how that effects groups falling at different speeds. Is that so small as to have an insignificant effect on these formulas? Does that assume people put in conservative numbers...obviously someone trying to use this to put groups so close as to only allow a 100 foot margine for error will receive bad results. Bill? Kallend? Thanks again for the useful input. Where is it? It wasn't attached to the post. Put my bit at the beginning and you have it all in one place. If you do that and send it to me, I can add some stuff to account for fall rate differences unless someone beats me to it.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites winsor 186 #46 February 27, 2004 QuoteQuoteThere will probably never be a "precise" formula that can accommodate all variables to accurately determine exit separation on all jump runs. The necessary information is imprecise by its very nature. It would be easier to write the formula needed to send a landing craft to Mare Imbrium. The best anyone can do will have to be a generality that gives a reasonable margin of safety for all situations -- whatever that may be. Dave My contribution to the issue was listed on The Ranch web site late last season and can be found at: http://ranchskydive.com/safety/tb_article15.htm. It's designed as a general discussion with a specific set of numbers to define time between groups under limited conditions. Tom Buchanan S&TA Instructor, AFF, SL, IAD, Tandem Author JUMP! Skydiving Made Fun and Easy With all due respect, I don't believe you have the temerity to post an article that makes serious reference to the 45 degree myth. The 45 degree approach is worse than useless. Anyone paying attention can demonstrate its invalidity as a trivial exercise. Anyone who thinks it has merit is surviving on luck alone. Regardless of all the ratings you put forth, you just flunked Freshman Physics. Do your homework, and fix your website. You have dangerous misinformation posted therein. Blue skies, Winsor Quote Share this post Link to post Share on other sites billvon 2,396 #47 February 27, 2004 >OK, here's a shot at a calculator to give a recommended separation >between groups based on group size . . . It looks good for any group over 6 people, but I'd add discrete limits below that. I think I might also change the scaling factor to 250. Solo: 800 feet min (since solos are often low experienced jumpers who tend to slide) 2-6 way: 1000 feet min (since I don't believe in people tracking in any direction other than away from the center, and up to 6 ways generally break off at the same altitude and hence have the same spread) Quote Share this post Link to post Share on other sites kallend 1,623 #48 February 27, 2004 Quote>OK, here's a shot at a calculator to give a recommended separation >between groups based on group size . . . It looks good for any group over 6 people, but I'd add discrete limits below that. I think I might also change the scaling factor to 250. Solo: 800 feet min (since solos are often low experienced jumpers who tend to slide) 2-6 way: 1000 feet min (since I don't believe in people tracking in any direction other than away from the center, and up to 6 ways generally break off at the same altitude and hence have the same spread) Thanks - will make changes. As I said, this is judgement, not physics.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites tombuch 0 #49 February 27, 2004 Quote With all due respect, I don't believe you have the temerity to post an article that makes serious reference to the 45 degree myth. The 45 degree approach is worse than useless. Anyone paying attention can demonstrate its invalidity as a trivial exercise. Anyone who thinks it has merit is surviving on luck alone. Unfortunately, the 45 degree rule is out there and needs to be addressed. It DOES work if there is no wind at all, and that needs to be understood. It doesn't work if there is wind. Many people (here at dropzone.com and at my drop zone, believe in the 45 degree rule, so we can't ignore it. Heck, many instructors are still teaching the 45 degree rule, so our customers come to us believing it works. Please reread that part of the web feature:QuoteThe concept of watching a group leave and slide back under the tail to 45 degrees behind the airplane seems to work well with no wind, but it provides only a single separation standard that is difficult to quantify or vary for different types of groups that require more or less space. If there is lots of wind, the 45 degree standard can provide considerably less separation than desired. In fact, if we imagine an airplane flying directly into a wind so great that the plane isn't moving, it will still be possible to achieve the 45 degree standard as jumpers are initially blown back, but every jumper will be getting out over exactly the same place on the ground, they will be blown back along exactly the same path, and will open at the same place with no separation at all. The separation doesn't suddenly disappear when the airplane stops covering ground in the wind, but rather deteriorates as the wind speed increases, and the 45 degree rule can't be expected to compensate. The crux of the feature (available at: http://ranchskydive.com/safety/tb_article15.htm is to base separation on time, NOT the 45 degree rule. We can argue about if the critical wind is at jump altitude, or opening altitude, but for simplicity I needed to advance a basic policy that is simple to understand and implement under most conditions. With 22 people on each plane making their own decisions at a drop zone with "no rules" we need an easy solution. On those few days with weird winds our pilots tend to spot accordingly, and we try to get folks thinking as best we can. So, with all due respect, we can't actually ignore the 45 degree rule, we need to teach around it, and provide a well reasoned alternative. Tom Buchanan Instructor (AFF, SL, IAD, Tandem) S&TA Author JUMP! Skydiving Made Fun and EasyTom Buchanan Instructor Emeritus Comm Pilot MSEL,G Author: JUMP! Skydiving Made Fun and Easy Quote Share this post Link to post Share on other sites pilotdave 0 #50 February 27, 2004 QuoteIt DOES work if there is no wind at all, and that needs to be understood. Ummm...you sure? Be more specific. Does it work no matter what the airspeed is? How about group size? I think to make a statement like that is just silly. It simply doesn't work. If you want to address it, say that it simply doesn't work. 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billvon 2,396 #37 February 26, 2004 Attached is an Excel spreadsheet that calculates exit separation. The left columns are the data to be entered. Enter winds at exit and deployment altitudes in ktas and degrees. Heading can be true or magnetic as long as you use the same scheme throughout. Enter aircraft true airspeed (ktas, not kias) and heading of the aircraft. Enter the number of seconds you will leave between groups. On the right side are the results. You'll see aircraft groundspeed along jump run in ktas and fps, and the amount of wind down the jumprun line at opening altitude. The final number is total separation in feet. JK, feel free to check this and make sure I didn't reverse a sign or something. Quote Share this post Link to post Share on other sites
kallend 1,623 #38 February 27, 2004 QuoteAttached is an Excel spreadsheet that calculates exit separation. The left columns are the data to be entered. Enter winds at exit and deployment altitudes in ktas and degrees. Heading can be true or magnetic as long as you use the same scheme throughout. Enter aircraft true airspeed (ktas, not kias) and heading of the aircraft. Enter the number of seconds you will leave between groups. On the right side are the results. You'll see aircraft groundspeed along jump run in ktas and fps, and the amount of wind down the jumprun line at opening altitude. The final number is total separation in feet. JK, feel free to check this and make sure I didn't reverse a sign or something. Looks good to me.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 1,623 #39 February 27, 2004 OK, here's a shot at a calculator to give a recommended separation between groups based on group size (your group and the preceding group). Assuming normal tracking, fall down the tube without backsliding, etc. This is more judgement than science- feedback please.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
jdfreefly 1 #40 February 27, 2004 Thanks to Kallend and Bill for actually answering the question....on a side note, Tom , that is a great article. Maybe I can print out about 20 copies and scatter them around the dz on safety day.... I fully understand that there is no silver bullet that will give us an absolute answer to life the universe and everything....However, we should be able to come up with something that will work in 99 percent of the cases involved. Hopefully, Bill's formulas and Kallend's can combine to create that solution. Then from now on, when someone mentions the 45 degree rule, they can be pointed to this. I know some will still insist that they are right and all the good sience in the world can't compete with blind devotion to myth. I wish the world wasn't that way, but as my grand papy always said, "Why don't you wish in one hand, and crap in the other, then tell me what you have." Methane Freefly - got stink? Quote Share this post Link to post Share on other sites
jdfreefly 1 #41 February 27, 2004 Okay, I copied Bill's spreadsheet and modified it so you can do it either way, enter all the relevant data in one, including time between groups and it will tell you how much separation that produces(thanks Bill). The second one you enter all the relevant data including the desired amount of separation and it will tell you how many seconds to allow between exits. Combine that with Kallend's estimates on required separation for different sized groups and we nearly have everything we need for a great first draft. Once again though, I would like to make something that takes a few more things into account..see my original post...but this is a great starting point. Do you guys feel that this is good enough? I guess my question is this: The spreadsheet really doesn't take into acount how much push is created by the wind during freefall and how that effects groups falling at different speeds. Is that so small as to have an insignificant effect on these formulas? Does that assume people put in conservative numbers...obviously someone trying to use this to put groups so close as to only allow a 100 foot margine for error will receive bad results. Bill? Kallend? Thanks again for the useful input. Methane Freefly - got stink? Quote Share this post Link to post Share on other sites
dnewcomer 0 #42 February 27, 2004 B-- I believe this thread represents the best reason DZ.com exists. Too bad everyone who ever exits a plane to make a skydive is not going to read it. The idea of making copies of this info for wide distribution at DZ's on Safety Day is a good one. Maybe the USPA should send a memo or email out to all DZ's, DZ owner/operators, and S&TA's emphasizing that the "45 Deg. Rule" is invalid and should never be used or recommended as a technique for determining exit separation distance. It would seem that this should be part of their goal to maximize the safety of the sport. D-- Quote Share this post Link to post Share on other sites
pccoder 0 #43 February 27, 2004 Could be, but I remember someone mentioning on the plane that it was the stall warning. But, they could be wrong. PcCoder.net Quote Share this post Link to post Share on other sites
kallend 1,623 #44 February 27, 2004 QuoteQuotemichaelmullins - I have experienced that real strong blast of wind feeling that some other's have mentioned on this thread in the King Air at Titusville too. At the same time I was hearing the stall warning going off in the cockpit before stepping out the door. What was going on there? Any chance it was a gear warning horn? I have no idea if a kingair has this, but some planes have a horn that goes off if the throttle is idled with the gear up. Dave My Mooney does this. Not that it has any relevance at all to a King Air.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 1,623 #45 February 27, 2004 QuoteOkay, I copied Bill's spreadsheet and modified it so you can do it either way, enter all the relevant data in one, including time between groups and it will tell you how much separation that produces(thanks Bill). The second one you enter all the relevant data including the desired amount of separation and it will tell you how many seconds to allow between exits. Combine that with Kallend's estimates on required separation for different sized groups and we nearly have everything we need for a great first draft. Once again though, I would like to make something that takes a few more things into account..see my original post...but this is a great starting point. Do you guys feel that this is good enough? I guess my question is this: The spreadsheet really doesn't take into acount how much push is created by the wind during freefall and how that effects groups falling at different speeds. Is that so small as to have an insignificant effect on these formulas? Does that assume people put in conservative numbers...obviously someone trying to use this to put groups so close as to only allow a 100 foot margine for error will receive bad results. Bill? Kallend? Thanks again for the useful input. Where is it? It wasn't attached to the post. Put my bit at the beginning and you have it all in one place. If you do that and send it to me, I can add some stuff to account for fall rate differences unless someone beats me to it.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
winsor 186 #46 February 27, 2004 QuoteQuoteThere will probably never be a "precise" formula that can accommodate all variables to accurately determine exit separation on all jump runs. The necessary information is imprecise by its very nature. It would be easier to write the formula needed to send a landing craft to Mare Imbrium. The best anyone can do will have to be a generality that gives a reasonable margin of safety for all situations -- whatever that may be. Dave My contribution to the issue was listed on The Ranch web site late last season and can be found at: http://ranchskydive.com/safety/tb_article15.htm. It's designed as a general discussion with a specific set of numbers to define time between groups under limited conditions. Tom Buchanan S&TA Instructor, AFF, SL, IAD, Tandem Author JUMP! Skydiving Made Fun and Easy With all due respect, I don't believe you have the temerity to post an article that makes serious reference to the 45 degree myth. The 45 degree approach is worse than useless. Anyone paying attention can demonstrate its invalidity as a trivial exercise. Anyone who thinks it has merit is surviving on luck alone. Regardless of all the ratings you put forth, you just flunked Freshman Physics. Do your homework, and fix your website. You have dangerous misinformation posted therein. Blue skies, Winsor Quote Share this post Link to post Share on other sites
billvon 2,396 #47 February 27, 2004 >OK, here's a shot at a calculator to give a recommended separation >between groups based on group size . . . It looks good for any group over 6 people, but I'd add discrete limits below that. I think I might also change the scaling factor to 250. Solo: 800 feet min (since solos are often low experienced jumpers who tend to slide) 2-6 way: 1000 feet min (since I don't believe in people tracking in any direction other than away from the center, and up to 6 ways generally break off at the same altitude and hence have the same spread) Quote Share this post Link to post Share on other sites
kallend 1,623 #48 February 27, 2004 Quote>OK, here's a shot at a calculator to give a recommended separation >between groups based on group size . . . It looks good for any group over 6 people, but I'd add discrete limits below that. I think I might also change the scaling factor to 250. Solo: 800 feet min (since solos are often low experienced jumpers who tend to slide) 2-6 way: 1000 feet min (since I don't believe in people tracking in any direction other than away from the center, and up to 6 ways generally break off at the same altitude and hence have the same spread) Thanks - will make changes. As I said, this is judgement, not physics.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
tombuch 0 #49 February 27, 2004 Quote With all due respect, I don't believe you have the temerity to post an article that makes serious reference to the 45 degree myth. The 45 degree approach is worse than useless. Anyone paying attention can demonstrate its invalidity as a trivial exercise. Anyone who thinks it has merit is surviving on luck alone. Unfortunately, the 45 degree rule is out there and needs to be addressed. It DOES work if there is no wind at all, and that needs to be understood. It doesn't work if there is wind. Many people (here at dropzone.com and at my drop zone, believe in the 45 degree rule, so we can't ignore it. Heck, many instructors are still teaching the 45 degree rule, so our customers come to us believing it works. Please reread that part of the web feature:QuoteThe concept of watching a group leave and slide back under the tail to 45 degrees behind the airplane seems to work well with no wind, but it provides only a single separation standard that is difficult to quantify or vary for different types of groups that require more or less space. If there is lots of wind, the 45 degree standard can provide considerably less separation than desired. In fact, if we imagine an airplane flying directly into a wind so great that the plane isn't moving, it will still be possible to achieve the 45 degree standard as jumpers are initially blown back, but every jumper will be getting out over exactly the same place on the ground, they will be blown back along exactly the same path, and will open at the same place with no separation at all. The separation doesn't suddenly disappear when the airplane stops covering ground in the wind, but rather deteriorates as the wind speed increases, and the 45 degree rule can't be expected to compensate. The crux of the feature (available at: http://ranchskydive.com/safety/tb_article15.htm is to base separation on time, NOT the 45 degree rule. We can argue about if the critical wind is at jump altitude, or opening altitude, but for simplicity I needed to advance a basic policy that is simple to understand and implement under most conditions. With 22 people on each plane making their own decisions at a drop zone with "no rules" we need an easy solution. On those few days with weird winds our pilots tend to spot accordingly, and we try to get folks thinking as best we can. So, with all due respect, we can't actually ignore the 45 degree rule, we need to teach around it, and provide a well reasoned alternative. Tom Buchanan Instructor (AFF, SL, IAD, Tandem) S&TA Author JUMP! Skydiving Made Fun and EasyTom Buchanan Instructor Emeritus Comm Pilot MSEL,G Author: JUMP! Skydiving Made Fun and Easy Quote Share this post Link to post Share on other sites
pilotdave 0 #50 February 27, 2004 QuoteIt DOES work if there is no wind at all, and that needs to be understood. Ummm...you sure? Be more specific. Does it work no matter what the airspeed is? How about group size? I think to make a statement like that is just silly. It simply doesn't work. If you want to address it, say that it simply doesn't work. Dave Quote Share this post Link to post Share on other sites
