murps2000

Hey, you aren't that conspicuous. It's just, I've seen a few students come & go there & elsewhere. You had the right attitude, and I can tell that whether the rest of the community knows it or not, skydiving needs you. You were naturally inquisitive, too. That will serve you well. Sorry to say, that I won't be back at the burg much this spring, if at all. Can't really progress there too well in the direction that I wish to go. I think I'm going to head back across the Bay Bridge to where it all started for me. Like the song goes, see some old friends, good for the soul. But check my profile for e-mail add. If you ever wanna rap, I'm here. Blue ones....

Sean. Don't know if you ever got my name, but I think I met you when you did level 1, since I knew Gindy & Peg already, and they came up that day. Like around July 4th, right? You had that cool shirt that said "All my heroes killed cowboys". I did tandems at C-burg, and I remember talking with you a couple times as you went thru AFF & licensing. You drove down (in an ElCo?) & got weathered out once or twice, if I remember correctly. You asked me once what was the worst thing that could happen to you while skydiving (referring to malfunctions, of course), and I think we never really finished that conversation. Anyway, glad to hear you got down to Deland. I thought we told you to get your ass up to the Ranch! You know, Randy, who I believe was one of your JM's is going to be up there this year. I know it's cold, right now, but that place is pretty nice in the summer. Beautiful view. Glad you're still jumping, good luck, brutha!

Really nice manual! Very informative, with succinct presentation of a lot of important info and advice. Especially liked the reference to the "Tao" when describing the perfect swoop. You seem to really appreciate both the art and science of your craft. I get the impression that the manner with which a well designed airfoil so gracefully slices the air is a thing of beauty to you.

Hey bro, are you the Ian that did AFF at C-burg last year? Friends with Peg & Gindy?

That's funny! Man, until now, I used to think that I was the only person to have thought of doing something like that, but I would've been embarassed to say anything about it here. One of the key points in this discussion is reducing riser pressure when you initiate swoop entry. Approaching it in the manner you describe has the opposite effect. I discussed this with somebody at Chambersburg, once, because the DZO there is old-school, and basically anti-swoop (I know, but it was tandem work, and it was an hour from my house). If you ever were swooping and did okay, it was for the most part cool, but if you f-ed up and had to dig a little on a hook, his and the S&TA's solution was to come tell you that you could only do 90's from then on (even though the S&TA routinely skids in on her butt). So this other fella and I are knocking back a few around the fire one night and came up with the idea of doing a mad hook so that you swooped your base leg, and then maintained what you had by doing a 90 into the landing area. Some guys do 90-270's, this was essentially a 270-90. What you end up doing, tho, is basically what amounts to a fly-by under canopy, and you have to try to do a one-armed pull up on your riser to turn in. So it doesn't work so well. But way to think big, though.

I will let it go as well. My original purpose for posting to this thread has been lost, anyway. I would like to say, however, that when I visited your DZ for Halloween of 2001, you faced what I consider to be very challenging conditions for spotting. Surface winds were up considerably, and I assume uppers were quite fast. As I recall, you were very explicit in stating that there would be no set exit interval. Each group was to exit when you gave the go ahead. I remember waiting for as much as 20 seconds at the door after groups before me left. On one load, when I was last to exit, you flew jumprun in the shape of an L, and I had never seen this before. Yet no one landed off, and never did I witness anyone opening near each other. I assumed then, that because you likely flew jumprun at the same airspeed every time, groundspeed was of paramount concern to you in conducting operations this way, and I was more than a little impressed with the results. When at Quincy once, I left your plane at 22,000 ft, and I could swear that I opened up right above the spot in the alternate landing area at which I intended to land. I remember taking a few seconds under canopy to ponder what a great shot it was from 4 miles up. And I also read with great interest the debate which took place in parachutist so many years ago. Your statements made perfect sense to me, and is a reason why I so vehemently clung to my position on this issue. I have no aspirations to ever be a jump pilot, nor a load organizer, so for those who fear my ignorance, don't worry. I will have little influence over your safety in freefall. If I'm riding in your King Air, Mike, I will do as you say, because you have proven to me that you can get the job done. If I am riding in anyone else's aircraft, I will do it the old fashioned way, and use my eyes. And if I don't like what I see when I get outside, I will, as I have on occasion, track for my life. It's what I had to do at Lake Wales.

Hey, do you know which female jumper has the most jumps? I always heard it was Cheryl Stearns, with Carolyn Clay in second place. Is this still correct?

So I take it this means you won’t forget me? Well let’s see… perhaps to get myself to agree with you I should approach this topic in a different way. Say, in the manner of a simple geometric proof. Now, if I accept as postulate that if Kallend says something, it must be right, and Kallend’s position is the same as yours, and your position (and therefore Kallend’s) differs from mine, it must follow, then, that I am wrong, right? Dang! Err… thanks… I think. Actually, engaging in heated debate with you, Kallend and Billvon? It’s probably stupidity. Don’t mistake the gift of the gab for intelligence. I believe the intransigence you speak of was something I most likely mistook for tenacity. Well then, you have nothing to worry about from me. As you can see, I’m merely stupid. In addition, I doubt seriously that I will ever be in a position to make a decision that will jeopardize your safety. You already know that I will give you way more time than three seconds if I’m exiting after you, regardless of my motive for doing so, and I don’t think I could force you to exit an aircraft at a time that you deem unsafe. You already know that I’m aware that I should track perpendicular to the line of flight whenever possible, so I will probably not commit an incursion into your airspace after exit. You also know that I think holding at my opening point is a bad idea, so I doubt I’ll be under canopy below you in freefall. Given my choice of disciplines to pursue in skydiving, it's most likely that I will probably take myself out by way of a botched hook turn. If you and I are at the same DZ when it happens, I promise to do my utmost to avoid hitting you with the jagged end of my protruding femur. Wait a second. What if said comic book physics still get you to make the right decision? You said yourself that if someone mandates three seconds between groups, they’re clueless, and I agree, but it seems to be for the wrong reasons. I wasn’t, and the only misconceptions put to rest are my own. As far as the models are concerned, I wouldn’t worry too much. The only one so vociferously put forth was mine, and I believe it fairly well lies in ruin for all to see at the top of the illogical argument pile. It in itself was not incorrect, but, as you pointed out, it does not exactly apply. I see now that this is because it stops at what would be analogous to the opening point in a skydive, and more needs to be considered after that. Kallend’s assertion that a group of skydivers on ram-air canopies behaves, on average, as does a group on rounds is something I definitely failed to consider. I sort of figured this to be a purely random event, and this led me to believe that horizontal distance between opening points was necessary, regardless of time delay. In the case where ground speed is zero and winds at deployment altitude are also zero (an admittedly highly unlikely scenario), collision issues will arise, but also I see now that this is not directly related to the fact that ground speed is zero. It is instead because the difference between airspeed at jump altitude and wind speed at deployment altitude happens to be the same as the difference between airspeed and ground speed, and is merely coincidental. I believe at one point you made a statement that should have clued me in to this. I believe it was this one: The most critical parameter for ensuring freefall separation is the speed of the aircraft with regard to the airmass at opening altitude. So you tried. Well, now there’s one more, Winsor, even if it took all but the physical beating of the concepts into my head. And if Mike Mullins, whose ability to consistently and accurately put jumpers on target cannot be overstated, can admit he was wrong and change his position, than certainly I can, as well. I must say that it was quite gracious of you to attempt to educate me in these matters without charging me money. I hope I don’t see a bill. Now, I think I’ll go wash this crow out of my mouth with a nice glass of shut the hell up. Oh, and BTW, I’m still not going back to jump CASA’s at Lake Wales.

***The points you are missing: You have to account for the individual who deploys, and then fiddles around with his slider, cheststrap and booties while drifting with the wind. You have to account for the Stiletto that opens on a random heading. On average for the first few seconds of flight, they drift with the wind. You have to account for the average behavior of the group, each of whom may be facing out from the center but whose center point drifts with the wind. People don't just deploy and, when open, instantly turn into the optimum direction for collision avoidance. Sometimes they turn in the worst direction for collision avoidance and the wind drift makes it even worse. - Thank you, Kallend. These points are exactly what I am missing. Your ability to see my obstacle to accepting what I am being told in the midst of this debate over whether or not I understand the physics involved is one that must serve you well as an instructor. And I now see what Billvon and Winsor are trying to get through my thick skull. If opening and behavioral anomalies experienced by jumpers under ram-air canopies average out such that they behave like rounds, then canopy drift should be taken into account when determining exit interval. Whether or not jumpers end up opening at the same point in space because their exit point is stationary over the ground is, in fact, inconsequential because of the time delay (which Billvon and Winsor did attempt to tell me), and the fact that the ram-air pilot who, after opening, holds in the wind at the point at which he opened (albeit lower, of course) is essentially flying back up the line of flight. As Billvon appropriately pointed out, this is a decidedly unsafe thing to do, and can defeat the beast laid plan of anyone determining exit interval. And, you may be surprised to know, some people have round reserves! This is no surprise, but I would be surprised if you said they used them on every jump. Nevertheless, I’m familiar with the school of thought that says you should spot for your reserve.

Look, I went to Kallend's website (which was quite nice), and plugged in the values for the three scenarios that he depicted. All things being equal, that is, no difference in fall rates between each group, the distance between opening points remained constant at 1000 ft. for each situation. Each jumper drifted the same amount during freefall. The only thing that increased the distance between the parachutists was the downwind drift of the first jumper under an open canopy, while the second jumper finished freefall. This would lead one to assume that the jumpers in the program were on rounds, and at the mercy of the winds after opening. Last I checked, people don't jump rounds much any more, so counting on the previous jumper to automatically drift downwind would be relying on chance, IMO. Next, I tried plugging in some other values to see what I would come up with. Leaving the airspeed on jump run constant at 80kts, I plugged in upper wind values of 0, 20, 40, 60, and 80 kts. I left ground winds at 0 to simplify. What I noted was that the distance between opening points steadily decreased with each increase in upper wind values (which one could equate to a reduction in groundspeed on jumprun). Further, I found that, in order to maintain the same separation between opening points, exit intervals needed to increase exponentially with each increase in upper wind velocity. Then, I tried plugging in the same values as a tailwind, which would simulate an even greater groundspeed. Distances between opening points increased further. Remember, airspeed remained the same. Try this yourself, and see what you come up with.

Nice link, with an obvious great deal of effort put into it. I disagree with the conclusions you draw, however, particularly in case 2, figure 1. The figure shows the tethered balloon, which is the same condition as the one I described in which airspeed and upper winds cancel each other out. Each jumper exits and arrives at the same opening point. they follow the same light trail. Where the smoke goes is irrellevant because the smoke is not falling. If the first jumper hangs around under canopy at the same point above the ground where he opened, the next jumper's opening point will be right over top of him. Think of it this way. If you are in a boat travelling at 20 fps up a stream that is flowing at 20 fps (in effect moving 0fps over the bottom of the stream), and start dropping fishing bobbers into the water, they will be separated by 20 feet for each second of interval between them. They will remain separated this way because they will remain under the influence of the fluid medium in which they are placed indefinitely. If you start dropping fishing weights into the water, and they take 5 seconds to sink to the bottom, they will all travel 100 ft. downstream as they descend and hit bottom at the same point. Can you explain to me how they would travel to anywhere else? Also, if airspeed is what should determine exit interval, then exit interval should be the same for each jump run on every day, regardless of the change in wind conditions, as long jump run is flown at the same airspeed. To my knowledge, I have only recently, and for the first time, visited a DZ that operates this way. Upper winds and ground speed are usually taken into account. Why is this? Is the majority of the skydiving community as ignorant of basic physics as I appear to be to you?

Answer: Yes it would. You and all who exited before and after you would be affected identically by the variances in wind direction and velocity that you encountered as you descended. In short, you would all drift the same amount.

Do you really think that if you were flying jumpers with an airspeed of 160mph into uppers that were blowing at you at 160mph (giving you a groundspeed of 0 mph) that you would do anything but drop them all right on top of each other? Sure they would be separated by some 240 ft. for each second between exits at first, but at some point they would get off the hill and be falling straight down, except for the horizontal vector imparted to them by the winds they fell through. They would all drift in freefall to the same point when they reached opening altitude. In this hypothetical situation, and, in fact, all other situations, airspeed would be irrelevant.

As the great Foghorn Leghorn once so elloquently stated: "I know, I know, you can't argue with figures, son!" With regard to canopy design, I've often puzzled over how two different sizes of the same model could seem to exhibit such variances in riser pressure. I've experienced this on Stilettos and Batwings, and I'm at a loss to explain it. While I can't be absolutely positive as to the state of trim of all of the canopies I've jumped, they all seemed to be okay. Any hypotheses, doctor?

Ground speed is entirely irrlevant to separation in the air. Airspeed is what gives you freefall separation, groundspeed *contributes* to separation between groups on landing. Big, big difference. *** I don't know if a thread about this has yet existed on DZ.com, but it surely has been discussed before. I'm not sure exactly when, but sometime in the early to mid 90's, a lengthy exchange regarding this issue occurred within the letters section of parachutist, and I believe Mike Mullins ended up doing fine job of clearing things up for the non-believers. Trust me, ground speed is what you need to consider when determining exit separation. It was correct then, and it is correct now.

Yeah, X-Keys rules! Only DZ I've been to that has a swoop lake.

poop. I mean swoop.

LMAO Dude, that is a really cool story. Is that how you got promoted to Captain?

First, a ground speed of 160mph would mean that the CASA would have to be flying a downwind jump run with uppers doing about 30 mph. This would be the BEST case. Most times, the jump run is flown into the uppers which would slow the ground speed to far less than 160mph. This means that 700 ft. separation was the best that could be hoped for under ideal conditions, which did not exist at the time. Actual separation was much less. Second, 700 ft. separation is enough, unless someone starts tracking up or down the flight line. As I stated in my first post, I do not trust everyone on a CASA load to do that. I'm sorry, but I am firmly convinced that there are quite a few unconcerned or oblivious jumpers out there, and in fact, as was demonstrated by one very close call that a friend of mine had down there, there were some on these CASA loads. Also, there were more than two ways on these loads. There were RW loads as big as 12-ways that I know of, and yet still three seconds was mandated as the amount of separation to be given. Now, how are you going to do a 12-way without at least one person ending up tracking up the line of flight? And what happened in reality was that some groups gave more time, and some gave less. It is simply indicative to me of how many people just walk to the tailgate and hop out, without any thought or regard for the situation that could be developing as a result of conducting skydiving operations this way. And as the thread originator appropriately pointed out, big-sky theory is what saves us most of the time. There is little I can do about this except leave and go somewhere that seems safer, so that is what I did, because it seems an impossible task to make the average jumper aware. No one ever seems to do anything until someone gets hurt or killed.

Man, I'm glad somebody's bringing this up. I hope many jumpers take a look, because I think a lot of people in the sport are either unaware or unconcerned with how important exit spacing is. This was an issue for my girlfriend and me when we were at Lake Wales just before the new year, and it's one of the reasons we left the DZ to go to Z Hills. After several CASA loads of 30 or more, on which the S&TA was insistant on a 3 second delay between groups, even to the point of yelling at the last few groups to get out (because he was doing tandems on the load), we were growing increasingly concerned. Even with a ground speed of 160 mph, by my calculations, this would mean, at most, about 700 ft. between groups, and this was simply unacceptable to us. There were often 5 two ways on each load, mostly jumpers who were unknown to us, and I just do not trust everyone to be situationally aware enough not to track up or down the flight line. Then, a few that were in our our group of visiting jumpers experienced some close calls, and we decided to say something. My girlfriend spoke to the DZ manager, and admittedly she was not excercising what I would call, IMO, the epitome of tact, but she was rightfully upset at the seeming lack of concern by the S&TA for jumpers' safety. It became quite apparent that this was getting us nowhere, so we decided to leave. I lament that we felt compelled to leave, because Lake Wales is a great DZ, with some fun people. But greater spacing, and a second pass, was really necessary, and it just wasn't going to happen. I'm thankful that no freefall collisions occurred while this was going on but I consider this whole affair to be very dissappointing. The institutional knowledge is quite available as to what could happen when circumstances such as these exist, with large numbers of skydivers jumping from multiple turbine aircraft. As a mentor of mine often has stated to me when alluding to an incident that he witnessed years ago at another DZ that operates CASA's, "It's all fun and games, till somebody loses a foot."

I'm not sure who it was. Possibly my friend Lance (username skydive2), because he had a camera, and I know he got a shot of one of my half decent runs on the pond, but it doesn't really look like him. Maybe just another swoop groupie. Yeah, a swoopie... Hey, good luck on your pond tour.

I was the one who came up & showed you the pic, and I'm sending you the shot as I post. But as you'll see, I'm not the guy in your photo. I was standing at the opposite corner of the pond. That's some other mystery photographer. Don't worry about sounding like an asshole, it was all good. If I'd layed some shit like that down on the pond, I'd be pausing to reflect, myself. Very nicely done.

Dr. Seuss rocks. When I have baby-sat my younger cousins/nephews etc., I always make a point of reading their Dr. Seuss books. *** Yeah he does, and my sister's an expert on tweetle beetles, now that she's got three kids. Nice, pic, Fredneck!!

A good year for me: 25-30 per month This year: maybe 15-20 per jumpable month It does, too!! Not like I wouldn't have made 20 jumps on July 4th weekend this year, if I could have, but I'm a just a filthy working joe, and the tandems just weren't there to pay me. Still, even if I'm not jumping, I'll remain at the DZ in order to drink beer and find fault with all the others who are still jumping. That should count for something, because beer, boobies, and fire are all part of skydiving.

Merry Christmas to you, also, and thanks so much for your sacrifice. If you're ever on the eastern shore of Delaware, or at Orange, VA, or maybe down at Carolina Sky Sports, or wherever you happen to catch me I'll cough up a jump ticket, too, as well as a drink of whatever I have. That goes for any of your other jumpin soldier friends. BTW, be careful when Santa comes over, I'm not sure he's equipped with an IFF transponder.