jdfreefly 1 #1 February 25, 2004 to make this applicable to realworld examples, distances and velocities should be broken into an x and a y component: va = velocity of aircraft vw1 = velocity of first wind layer vw2 = velocity of second wind layer . . . vwn = velocity of nth wind layer vo = velocity of wind at opening D = Distance (from perspective of outside observer) from exit point to opening, ie: the skydiver opens 300 ft from where they exited D1 = first jumpers D D2 = second jumpers D dt = distance attributed to D from "throw" dp = distance attributed to D from wind push in freefall(sum of dp1...dpn as a result of vw1...vwn) dg = distance attributed to glide from wind after opening Dreq = Distance rquired between groups = absolute value of D1 - D2 We should be able to combine all these factors to come up with an adequate formula to get t(time between exits) did I miss anything? My math skills are a bit rusty so I would like various suggestions on how to combine all this into one formula. Methane Freefly - got stink? Quote Share this post Link to post Share on other sites
dnewcomer 0 #2 February 25, 2004 Quoteto make this applicable to realworld examples, distances and velocities should be broken into an x and a y component: va = velocity of aircraft vw1 = velocity of first wind layer vw2 = velocity of second wind layer . . . vwn = velocity of nth wind layer vo = velocity of wind at opening D = Distance (from perspective of outside observer) from exit point to opening, ie: the skydiver opens 300 ft from where they exited D1 = first jumpers D D2 = second jumpers D dt = distance attributed to D from "throw" dp = distance attributed to D from wind push in freefall(sum of dp1...dpn as a result of vw1...vwn) dg = distance attributed to glide from wind after opening Dreq = Distance rquired between groups = absolute value of D1 - D2 We should be able to combine all these factors to come up with an adequate formula to get t(time between exits) did I miss anything? My math skills are a bit rusty so I would like various suggestions on how to combine all this into one formula. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ John, I don't think you can write a formula that would apply to every contingency because it depends on the number of jumpers exiting in each group, not the whole load. For example, an 8-way will need more room to track from the center of their formation before opening, so they need more time space before and after their exit. If everyone is exiting solo, it would be possible to write such a formula. That rarely happens at a commercial DZ. There are numerous solo's, 2-ways, 5-ways, 3-ways, all-size ways, etc. -- not to mention flatflyers compared to free-flyers -- exiting on any jump run. I believe the 45 degree rule is useful, but when there are very large groups (15-ways) that may be tracking in layers, even the 45 deg. rule may not allow for enough separation. The tendency for most people is to exit too soon after the group before them. We should all err on the side of safety (waiting) even if the pilot has to go around. Dave Quote Share this post Link to post Share on other sites
bigbearfng 9 #3 February 25, 2004 Hmmm.....no comment yet on that "45degree rule"....soon.... Quote Share this post Link to post Share on other sites
diverdriver 5 #4 February 25, 2004 QuoteJohn, I don't think you can write a formula that would apply to every contingency because it depends on the number of jumpers exiting in each group, not the whole load. For example, an 8-way will need more room to track from the center of their formation before opening, so they need more time space before and after their exit. If everyone is exiting solo, it would be possible to write such a formula. That rarely happens at a commercial DZ. There are numerous solo's, 2-ways, 5-ways, 3-ways, all-size ways, etc. -- not to mention flatflyers compared to free-flyers -- exiting on any jump run. I believe the 45 degree rule is useful, but when there are very large groups (15-ways) that may be tracking in layers, even the 45 deg. rule may not allow for enough separation. The tendency for most people is to exit too soon after the group before them. We should all err on the side of safety (waiting) even if the pilot has to go around. Dave 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 Schindler www.diverdriver.com ATP/D-19012 FB #4125 Quote Share this post Link to post Share on other sites
SkydiveMonkey 0 #5 February 25, 2004 This is turning into a "should I have an RSL" debate. Trouble is, no one seems to listen to this one ____________________ Say no to subliminal messages Quote Share this post Link to post Share on other sites
velo90 0 #6 February 25, 2004 QuoteYOU WILL NOT ATTAIN A 45 DEGREE FROM EXIT EVER!!! Not true, just up the the IAS at exit to 100 kts It's is of course no use at all for working out exit seperation. Quote Share this post Link to post Share on other sites
sducoach 0 #7 February 25, 2004 Time, time, time, time, time, time, between groups! 45 degrees does not work as diverdriver stated unless all groups are the same, winds are the same, the distance (read that time) from the a/c is the same REGARDLESS of how far down the 45 degree line they are. HELP CHRIS!!!!!! Blues, J.E.James 4:8 Quote Share this post Link to post Share on other sites
pccoder 0 #8 February 25, 2004 I'm suprised how many threads have been created lately about this very same issue. PcCoder.net Quote Share this post Link to post Share on other sites
The111 0 #9 February 25, 2004 QuoteQuoteYOU WILL NOT ATTAIN A 45 DEGREE FROM EXIT EVER!!! Not true, just up the the IAS at exit to 100 kts It's is of course no use at all for working out exit seperation. Heh, I was thinking the same thing. Had to climb out of the King Air at Titusville this weekend (fast than Mullins' - 15k in 7 minutes). Goddamn I could barely hang on. All I had to do was wait for one other guy to climb out so we could do our exit and I seriously almost got blown away. I wonder how fast that plane goes on jumprun?www.WingsuitPhotos.com Quote Share this post Link to post Share on other sites
elfanie 0 #10 February 25, 2004 Quote Heh, I was thinking the same thing. Had to climb out of the King Air at Titusville this weekend (fast than Mullins' - 15k in 7 minutes). Goddamn I could barely hang on. All I had to do was wait for one other guy to climb out so we could do our exit and I seriously almost got blown away. I wonder how fast that plane goes on jumprun? King air's prop blast is notoriously horrible. they get to altitude quick...but exits are a pain in the butt. I've A-L-M-O-S-T gotten blown off...I was rear float, as front float was climing out he hit my front arm and so I went belly-open to the prop blast...just about blew me off and I pulled my shoulder (slightly) pulling myself forward and re-grabbing the bar. nice place for getting to altitude (and zero-G's are fun to play with) But that tiny door? And that prop blast? Not as nice... -------------------------------------------- Elfanie My Skydiving Page Fly Safe - Soft Landings Quote Share this post Link to post Share on other sites
billvon 2,380 #11 February 25, 2004 >I believe the 45 degree rule is useful . . . If you want a rule that's that easy, count the windows in the airplane before exiting. It will give you a decent amount of time between exits and will give you something to do. It has nothing to do with exit separation (of course) but then neither does the 45 degree rule. Quote Share this post Link to post Share on other sites
timmyfitz 0 #12 February 25, 2004 The 45 degree doesn't work for skydiving but to say "YOU WILL NOT ATTAIN A 45 DEGREE FROM EXIT EVER!!! " is incorrect. It's simple math. If the plane continues at it's present altitude eventually the plane and the first jumper out will be at 45 degree angle, it may take up to two miles but......The formula is begginers geometry.....a2 + b2 =c2 (the 2 means squared, of course) Quote Share this post Link to post Share on other sites
diverdriver 5 #13 February 25, 2004 The 45 degree rule does not work for seperation. Stop saying it does. You will get someone killed eventually. I'm a bit fed up with having to repeat it over and over. Those instructors that continue to try and tell new jumpers that this is an acceptible method for attaining seperation should be taken out back and shot. There, is that better? Quote Share this post Link to post Share on other sites
pilotdave 0 #14 February 25, 2004 QuoteQuoteI believe the 45 degree rule is useful So diverdriver, you're saying we should all carry a protractor in the plane with us? Good idea. I'll put in in the pocket my hook knife is supposed to go! And I am just kidding and misquoting for those that haven't figured that out. Dave Quote Share this post Link to post Share on other sites elfanie 0 #15 February 25, 2004 QuoteQuote I believe the 45 degree rule is useful, 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!! You know that the 45* rule doesn't work... however...I also recall Bill (von) saying that he, too, saw value in the 45* rule...not because the previous jumper will get to a 45* angle at the appropriate time.. but because it makes newbies, who are otherwise overwhelmed with everything they have to think about, stick their heads out the door, scratch their heads, and wonder if that's 45* or not before they climb out and exit the plane...therefore usually giving themselves enough separation. Having value doesn't mean it's accurate. it means usually it is effective. although it could be said that it would be just as effective to place the rule that after the person before you exits, you have to touch all your handles, check your chest strap, and pat yourself on the head 3 times before you can exit. -------------------------------------------- Elfanie My Skydiving Page Fly Safe - Soft Landings Quote Share this post Link to post Share on other sites eames 0 #16 February 25, 2004 It would be even simpler than that.... Vac = airspeed of aircraft Vop = relative velocity of winds at opening alt* t = time between groups Separation = (Vac + Vop)t ** * relative to the aircraft ** This formula assumes that the upper and lower winds are directed exactly at or exactly against each other. I.e. If the winds at opening altitude are going in the opposite direction of the winds at jumprun altitude, then Vop will be negative. Insert a bit of trig otherwise. To understand why this works, see the "Re: [Martini] Opening High for Bad Spots" thread in Safety and Training. -Jason Quote Share this post Link to post Share on other sites kallend 1,620 #17 February 25, 2004 QuoteThe 45 degree doesn't work for skydiving but to say "YOU WILL NOT ATTAIN A 45 DEGREE FROM EXIT EVER!!! " is incorrect. Quote That is true. I'll bet they reach over 45 degrees when exiting the jet, and it would be pretty easy (for some) in a wingsuit. It's simple math. If the plane continues at it's present altitude eventually the plane and the first jumper out will be at 45 degree angle, it may take up to two miles but......The formula is begginers geometry.....a2 + b2 =c2 (the 2 means squared, of course) You may be correct, but your reasoning is wrong. Eventually the angle will reach 45 degree if the following happen: The skydiver deploys a parachute and slows the descent rate OR the skydiver reaches the ground and stops descending, AND the plane continues on it's way and doesn't return to the DZ. Otherwise, as long as the plane's TAS is less than the skydiver's fall rate, the skydiver will not reach 45 degrees no matter how long the freefall. And Pythagoras has nothing to do with that.... 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 eames 0 #18 February 25, 2004 Here's a more general formula that accounts for a difference in upper and lower wind direction (it can probably be simplified)... separation = (Vop*t cos A + Vac*t)^2 + (Vop*t tan A)^2 where Vac = airspeed of aircraft Vop = relative velocity of winds at opening alt t = time between groups A = angle between winds on jumprun and at opening altitude. -Jason Quote Share this post Link to post Share on other sites michaelmullins 77 #19 February 25, 2004 If you are getting blown off the side or having difficulty exiting that King Air, then that King Air is not slowing down and/or does not have the engine at idle. Propblast is from the prop-- if the engine is at idle and not producing any significant amount of thrust then there will be no propblast. Slipstream wind is from airspeed and is simply a function of how fast you are going. The exit speed on my King Air is 80 kts, there is no prop blast, and the only wind you will feel is 80 kts. 80 kts is the speed specified for competition and that is what the Otters are doing on exit. My 75 lb 11 year old had no trouble front floating nor has anyone ever complained about the wind blast or exit speed on my King Air. By the way, that other King Air is simply not faster. If the aircraft is flown properly there is no more wind or blast than any other jump aircraft and it is no more difficult to exit than any other ( yes, I know the door is smaller). Mike Mullins Quote Share this post Link to post Share on other sites billvon 2,380 #20 February 25, 2004 >but because it makes newbies, who are otherwise overwhelmed with > everything they have to think about, stick their heads out the door, > scratch their heads, and wonder if that's 45* or not before they > climb out and exit the plane...therefore usually giving themselves > enough separation. >Having value doesn't mean it's accurate. it means usually it is > effective. Well, by those standards, having a premature deployment out the door is effective in ensuring opening separation. Which is to say, sometimes it gives you a _lot_ of separation, but sometimes it can injure or kill you. Making someone look out of the plane is certainly a good thing, but if the rule is followed, people may get injured or killed when upper winds are high because they will not leave enough time. So as long as you tell people that the 45 degree rule can injure or kill them when used properly, you're covered. Quote Share this post Link to post Share on other sites pilotdave 0 #21 February 26, 2004 Hmmm... http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=857313;search_string=45%20degree;#857313 On january 14th you wrote: QuoteThe 45 degree thing can help with separation because it makes people stick their head out the door, look for the previous group, and then scratch their head for a moment while they try to figure out what 45 degrees is. That usually gives them enough separation from the previous group, if conditions are good. So I don't get too annoyed when I hear about the 45 degree thing, because it gets people to look out the door before they jump (which is a good thing) and it delays them a bit (which is also, generally, a good thing for separation.) On windy days, though, it may not be enough. Perhaps adding a caveat that they have to check the main landing gear as well if winds are high might do the trick. Dave Quote Share this post Link to post Share on other sites billvon 2,380 #22 February 26, 2004 Like I said, it can get people to look out the door and wait a bit. On windy days doing that alone (relying on the 45 degree thing to actually _work in other words) can kill you, so you have to add something else, like looking at the landing gear or doing some other silly thing that wastes just enough time. Or just wait the required amount of time for the separation you want. 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. The 45 degree thing can kill you because it will not give you enough separation on windy days. Period. Better? Quote Share this post Link to post Share on other sites pilotdave 0 #23 February 26, 2004 I understand. I just found it strange that you seemed to be arguing with yourself up above. She quoted you almost directly. Dave Quote Share this post Link to post Share on other sites pccoder 0 #24 February 26, 2004 The111 - Yea, that is a bad ass plane for getting to altitude, just group exits blow. michaelmullins - 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? Everyone - all this complex math is making me feel like I am at a Physics seminar PcCoder.net Quote Share this post Link to post Share on other sites diverdriver 5 #25 February 26, 2004 QuoteThe111 - Yea, that is a bad ass plane for getting to altitude, just group exits blow. michaelmullins - 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? Everyone - all this complex math is making me feel like I am at a Physics seminar Your pilot was behind the plane and was powering up to try and prevent a full stall. That would be my guess.Chris Schindler www.diverdriver.com ATP/D-19012 FB #4125 Quote Share this post Link to post Share on other sites Prev 1 2 3 Next Page 1 of 3 Join the conversation You can post now and register later. 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elfanie 0 #15 February 25, 2004 QuoteQuote I believe the 45 degree rule is useful, 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!! You know that the 45* rule doesn't work... however...I also recall Bill (von) saying that he, too, saw value in the 45* rule...not because the previous jumper will get to a 45* angle at the appropriate time.. but because it makes newbies, who are otherwise overwhelmed with everything they have to think about, stick their heads out the door, scratch their heads, and wonder if that's 45* or not before they climb out and exit the plane...therefore usually giving themselves enough separation. Having value doesn't mean it's accurate. it means usually it is effective. although it could be said that it would be just as effective to place the rule that after the person before you exits, you have to touch all your handles, check your chest strap, and pat yourself on the head 3 times before you can exit. -------------------------------------------- Elfanie My Skydiving Page Fly Safe - Soft Landings Quote Share this post Link to post Share on other sites
eames 0 #16 February 25, 2004 It would be even simpler than that.... Vac = airspeed of aircraft Vop = relative velocity of winds at opening alt* t = time between groups Separation = (Vac + Vop)t ** * relative to the aircraft ** This formula assumes that the upper and lower winds are directed exactly at or exactly against each other. I.e. If the winds at opening altitude are going in the opposite direction of the winds at jumprun altitude, then Vop will be negative. Insert a bit of trig otherwise. To understand why this works, see the "Re: [Martini] Opening High for Bad Spots" thread in Safety and Training. -Jason Quote Share this post Link to post Share on other sites
kallend 1,620 #17 February 25, 2004 QuoteThe 45 degree doesn't work for skydiving but to say "YOU WILL NOT ATTAIN A 45 DEGREE FROM EXIT EVER!!! " is incorrect. Quote That is true. I'll bet they reach over 45 degrees when exiting the jet, and it would be pretty easy (for some) in a wingsuit. It's simple math. If the plane continues at it's present altitude eventually the plane and the first jumper out will be at 45 degree angle, it may take up to two miles but......The formula is begginers geometry.....a2 + b2 =c2 (the 2 means squared, of course) You may be correct, but your reasoning is wrong. Eventually the angle will reach 45 degree if the following happen: The skydiver deploys a parachute and slows the descent rate OR the skydiver reaches the ground and stops descending, AND the plane continues on it's way and doesn't return to the DZ. Otherwise, as long as the plane's TAS is less than the skydiver's fall rate, the skydiver will not reach 45 degrees no matter how long the freefall. And Pythagoras has nothing to do with that.... 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
eames 0 #18 February 25, 2004 Here's a more general formula that accounts for a difference in upper and lower wind direction (it can probably be simplified)... separation = (Vop*t cos A + Vac*t)^2 + (Vop*t tan A)^2 where Vac = airspeed of aircraft Vop = relative velocity of winds at opening alt t = time between groups A = angle between winds on jumprun and at opening altitude. -Jason Quote Share this post Link to post Share on other sites
michaelmullins 77 #19 February 25, 2004 If you are getting blown off the side or having difficulty exiting that King Air, then that King Air is not slowing down and/or does not have the engine at idle. Propblast is from the prop-- if the engine is at idle and not producing any significant amount of thrust then there will be no propblast. Slipstream wind is from airspeed and is simply a function of how fast you are going. The exit speed on my King Air is 80 kts, there is no prop blast, and the only wind you will feel is 80 kts. 80 kts is the speed specified for competition and that is what the Otters are doing on exit. My 75 lb 11 year old had no trouble front floating nor has anyone ever complained about the wind blast or exit speed on my King Air. By the way, that other King Air is simply not faster. If the aircraft is flown properly there is no more wind or blast than any other jump aircraft and it is no more difficult to exit than any other ( yes, I know the door is smaller). Mike Mullins Quote Share this post Link to post Share on other sites
billvon 2,380 #20 February 25, 2004 >but because it makes newbies, who are otherwise overwhelmed with > everything they have to think about, stick their heads out the door, > scratch their heads, and wonder if that's 45* or not before they > climb out and exit the plane...therefore usually giving themselves > enough separation. >Having value doesn't mean it's accurate. it means usually it is > effective. Well, by those standards, having a premature deployment out the door is effective in ensuring opening separation. Which is to say, sometimes it gives you a _lot_ of separation, but sometimes it can injure or kill you. Making someone look out of the plane is certainly a good thing, but if the rule is followed, people may get injured or killed when upper winds are high because they will not leave enough time. So as long as you tell people that the 45 degree rule can injure or kill them when used properly, you're covered. Quote Share this post Link to post Share on other sites
pilotdave 0 #21 February 26, 2004 Hmmm... http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=857313;search_string=45%20degree;#857313 On january 14th you wrote: QuoteThe 45 degree thing can help with separation because it makes people stick their head out the door, look for the previous group, and then scratch their head for a moment while they try to figure out what 45 degrees is. That usually gives them enough separation from the previous group, if conditions are good. So I don't get too annoyed when I hear about the 45 degree thing, because it gets people to look out the door before they jump (which is a good thing) and it delays them a bit (which is also, generally, a good thing for separation.) On windy days, though, it may not be enough. Perhaps adding a caveat that they have to check the main landing gear as well if winds are high might do the trick. Dave Quote Share this post Link to post Share on other sites
billvon 2,380 #22 February 26, 2004 Like I said, it can get people to look out the door and wait a bit. On windy days doing that alone (relying on the 45 degree thing to actually _work in other words) can kill you, so you have to add something else, like looking at the landing gear or doing some other silly thing that wastes just enough time. Or just wait the required amount of time for the separation you want. 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. The 45 degree thing can kill you because it will not give you enough separation on windy days. Period. Better? Quote Share this post Link to post Share on other sites
pilotdave 0 #23 February 26, 2004 I understand. I just found it strange that you seemed to be arguing with yourself up above. She quoted you almost directly. Dave Quote Share this post Link to post Share on other sites
pccoder 0 #24 February 26, 2004 The111 - Yea, that is a bad ass plane for getting to altitude, just group exits blow. michaelmullins - 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? Everyone - all this complex math is making me feel like I am at a Physics seminar PcCoder.net Quote Share this post Link to post Share on other sites
diverdriver 5 #25 February 26, 2004 QuoteThe111 - Yea, that is a bad ass plane for getting to altitude, just group exits blow. michaelmullins - 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? Everyone - all this complex math is making me feel like I am at a Physics seminar Your pilot was behind the plane and was powering up to try and prevent a full stall. That would be my guess.Chris Schindler www.diverdriver.com ATP/D-19012 FB #4125 Quote Share this post Link to post Share on other sites
