winsor

If you want to LAND 1000 feet apart, this is fine. It has nothing to do with how far apart you are IN THE AIR, which is the frame of reference of interest when we discuss "horizontal separation." Once you select the wrong frame of reference for your analysis, any further effort is wasted. As Bill pointed out, the critical frame of reference is the speed of the aircraft with regard to the airmass at opening altitude. The next most relevant frame of reference is true airspeed. The least useful datum is groundspeed, so long as we're talking about horizontal separation IN THE AIR. What the ground is doing is, in and of itself, immaterial to the behavior of objects in the air above it. Q: If you have a layer of fog up to 2,500 feet and there is a 20 kt breeze on the ground, can you tell which way the wind is blowing by the behavior of groups in freefall above? A: No, the ground winds and ground speed are entirely immaterial, and have no effect whatsoever on the path of bodies THROUGH THE AIR. Blue skies, Winsor

And I make a living of jumping out of airplanes and more specifically putting people out of them safely. I looked at your paper and the only part that I can assume that your prior post would be applicable to would be jumping from a stationary object. Yes there people who understand and I happen to be one of them. Otherwise the military wouldn't of seen fit to award me the responsibility of jumpmastering people into combat. While I don't write the doctrine, there are people who do. We will assume that they are the "ones" you claim to know the fundamentals. What I and every other HALO jumpmaster do every time we jump is what those who "know" have seen fit to make doctrine. Which goes pages beyond what can be said for sport skydiving, which is too bad. You keep teaching physics in the classroom and I will keep putting people out of airplanes the military way, wheather or not you agree with the military method. Funny how we don't seem to have these seperation issues in the military? Your understanding, such as it is, is the classic "good enough for Government work." You simply don't know enough to have any idea how little you know. The Excel spreadsheet you tout illustrates at a glance the level of your ignorance. It's like the Soviets trying to bluff the West into thinking that their new jet bomber was supersonic without any understanding of the Area Rule - it only took one fast look to classify it as a subsonic flight platform. Your procedure is not inherently dangerous, and is better than nothing, but the physical model you use displays a fundamental lack of comprehension - as does your defense of your methodology. Be advised, you're out of your league. Blue skies, Winsor

But if you stretch out the time between groups, you're also stretching out the horizontal separation in the air. In strong wind, that means the first groups to exit will probably be downwind of the dz. Don't you want the same amount of total horizontal space between the first and last groups to be sure everyone can get back? And if increasing the time between groups increases separation unnecessarily, wouldn't that be a bad thing? I'm going to have to take notice and see if there are more off landings during strong head wind when everyone's taking more time between groups. How far apart you are in the air is simply the product of airspeed and time between exits (e.g., 150 fps * 5 seconds between exits = 750 feet horizontal between groups). The distance between no-drift landing points (like with round parachutes) is the product of groundspeed and time between exits (e.g., (150 fps airspeed - 50 fps headwind) * 5 seconds between exits = 500 feet. In the case above, which is like a 90 kt jumprun into a 30 kt headwind (typical), you can have a total of a mile and a half of horizontal separation in the air with only a mile track over the ground. Looking at it another way, assuming you have constant winds from the ground on up (you don't, but it makes it easier to visualize), the first group and the last group are separated by a mile and a half in the air. Between the time the first group lands and the last group lands, the last group will have drifted half a mile, so their landing points are only a mile apart. This is a FOUR dimensional problem - time is an important element. Blue skies, Winsor

Please explain to me how it's wrong so I can tell the Military. If I know how fast the airplane is moving through the air at a given moment and I know what the winds are at altitude(becasue I did my wind calcs and got the winds) I have a general idea of how much the wind is affecting not only the aircraft but the people leaving the aircraft. Hence the calculation of forward throw when computing the HARP. Once I know all of that I can use the ground speed as a reference to figure out the seperation between groups after the first group exits. I may not be a physics teacher but I have calc'd enough winds and put people out of both STOL and High performance aircraft to know that it works in the real world. Read the article to which I posted the url. I have made a living as a Physics Instructor. The Military is hardly monolithic, and I assure you that there are plenty of people in The Military that already understand the fundamentals. You don't (nothing personal, but it's the truth). Blue skies, Winsor

Hmmm.....that brings up a good question. It's often said that longer time between groups is necessary when jump run is into a strong wind. But wouldn't the jumpers exiting the plane be in that same wind? Essentially, the airspeed of the plane is unchanged. The distance traveled in the air over a 6 second period of time is the same no matter what the wind is doing. So, when the first jumper exits, they will be whisked away downwind from the plane much faster when there is a strong wind. So why is it necessary to change the separation time between groups? After 6 seconds, they should be just as far "downstream" from the plane regardless of ground speed. No? This is a classic "frames of reference" scenario that gives Freshmen fits (at least those in a rigorous technical program presupposing a solid basis in Physics). The airspeed of concern to jumpers just after exit is the true airspeed of the jump aircraft. In a free balloon you're looking straight down at whoever just left, regardless of what the ground is doing. The benefit that a headwind provides is the ability to take more time between groups and still have everybody get back (groundspeed only affects WHERE YOU LAND). Thus, with honking headwinds at altitude you can greatly increase horizontal separation between groups above the minimum, without anyone getting hosed (assuming that the person spotting has some understanding of the physics involved there, as well). Blue skies, Winsor

With a lineover, often it will go pretty close to straight ahead until you clear the brakes. Then you can expect to be spinning wildly on your back. This season I have had two lineovers (yeah, I've modified the offending portion of my packing technique). The first was on an elliptical loaded less than 1.2:1, and I cleared it by pulling down the rear riser on the offending side. It just popped out and flew fine. The second was on a cross-braced canopy loaded over 2:1, and it was a solid bowtie. Rather than find out how it would behave if I pissed it off further, I chopped it. In both cases the canopy had a mild turn, but I emphasize DO NOT CLEAR THE BRAKES until you have cleared the malfunction. I assure you that it is much more pleasant to cut away when in relatively normal flight under a canopy you'd just rather not land than it is to sort things out from a violently spinning malfunction. Kicking out of four line twists under a reserve is not my idea of a good time. Blue skies, Winsor

"For every complex problem, there exists a solution that is simple, elegant - and wrong." H. L. Mencken Nice spreadsheet, but the physics are fundamentally flawed. What the ground is doing is entirely irrelevant with regard to separation IN THE AIR. It only matters in terms of where you land. If you wish to pick a critical speed, it is that of the aircraft with regard to the airmass at opening altitude. An introductory treatment of exit separation can be found here: http://dogyks.home.netcom.com/jumprun/jmprun~1.htm. Blue skies, Winsor

I'm not an instructor, so my comments reflect only my opinion. One fundamental concept regarding safety systems is that they should be as simple as possible. Another is that you should change as little as possible in the lifesaving sequence over time. Thus, if possible, the best scenario is to learn a set of safety procedures on day one that will work just fine a thousand jumps from now. I am kind of a chicken, so I don't like going back into freefall unless I have my thumb hooked through silver. The idea of cutting away and then trying to find where the ripcord went when the harness shifted bothers me. My procedure is one hand per handle and I stuff them in my jumpsuit before clearing the brakes on my reserve. To get to whether you should hang on to your ripcord to see if you'd pulled it, this concept puzzles me. The fact that you're still in freefall is usually a pretty good clue that you're not done with your emergency procedures, and I've been known to pitch handles when I had more immediate concerns than hanging on to them. Keep pulling handles until you're under a good canopy, and hang on the handles if you are afforded that luxury, but focus 100% on staying alive regardless. If you're worried about losing the handle, don't sweat it - they'll make you a new one. Anyhow, the most basic cutaway procedure I was taught (when switching to 3-rings from shot and a half Capewells) was two hands per handle, keep an eye on the reserve ripcord while pulling the cutaway, and fling each handle once it is pulled completely. For your first cutaway, I suggest throwing the handles away as a matter of course. Thereafter, keeping the handles is optional, but you should be ready to pitch them IMMEDIATELY if they interfere in the slightest with your emergency procedures (sometimes there's more to do after pulling handles...). Oh, and whatever your procedure - practice it a lot. Having it be second nature really helps in a pinch. Blue skies, Winsor

The speed of sound (in a gas) is a function of temperature only. Sonic velocity varies by the square root of (absolute) temperature. At around 820 degrees Celsius the speed of sound is double what it is at 0 degrees Celsius, which is more of a consideration with regard to maximum piston speed in a recip or blade speed in a turbine than for skydiving in general. However, at -100 degrees Celsius the speed of sound is about 76% of its value at room temperature, going from about 346 to 262 meters/second or 774 to 586 mph. This is all off the top of my head, so don't bank on accuracy to three digits, but the basic idea is sound. Blue skies, Winsor

Well we will just have to hope that the winds are blowing in the same direction that the crop rows are planted otherwise what good does it do to look for signs of wind direction? (eye roll smiley) That bit of advice might be suitable for low/varibale wind days but the last thing one should be worrying about when landing off in a farmers field is if they're landing with the rows. Oh, I have to disagree with that. Needless to say, I've made rather a few landings into a variety of crops, under canopies from rounds to Class V and with crosswinds ranging from nil to substantial. There is a real laundry list of reasons why it is strongly advisable to land with the rows with a crosswind component instead of landing across the rows directly into the wind. If you can sink it straight down between the rows, fine. Otherwise, keep your ground track between the rows until your arrival. Blue skies, Winsor

This has to rank up there with the all time worst advice. Could you please elaborate with how the suns position dictates which way the wind is blowing? Does the suns position change if the wind changes while you climb to altitude? Using the sun as a reference point to determine wind direction is as good as flipping a coin, especially on days where the wind is constantly changing direction. You need to re think your method of determining wind direction before you hurt yourself. Back before the EPA was a reality, you could count on the plume from at least one chimney or smokestack being visible near a built-up area, which made real-time wind determination easy. For better or worse, those days are long gone. Using the sun as a directional reference provides a starting point, and it is of course not directly related to wind direction. It simply increases the odds that you are landing into the wind, which is a good thing. Pointing into the direction from which the wind was coming 10 minutes ago (if you're jumping Mullins' plane - there may be some that aren't as fast...) seems like a better idea than simply picking a direction and hoping that it's a good one. The contention that it is bad advice does not seem to be accompanied by a more effective field-expedient technique. If you know of a better way, please share it with us. Blue skies, Winsor

I have a mess of round reserves, but none of them are in CYPRES-equipped rigs. Putting a CYPRES in a Wonderhog is like putting a $50 saddle on a $5 horse. Blue skies, Winsor

Yup. As we watched it, we all agreed that we were witnessing a CYPRES save. A beautiful yellow canopy mercifully brought him into a clear and dry area with no further injuries. We couldn't have got there in time if he had hit the water. Blue skies, Winsor

I like to have as much nylon overhead as I can manage after pulling silver. When my FX 99 opened in an unlandable configuration at the Convention, emergency procedures resulted in my being under a 218 sq. ft. Raven 2 loaded at 0.9:1, which I can land just about anywhere. The smallest (square) reserve I have packed is 175 sq. ft., and I have used it successfully on more than one occasion. My preferred minimum size gives a 1 psf loading, and I'll take a Raven IV if I can get it. I NEVER base the size of my reserve upon the size of the main. The benefits of having a big, docile reserve greatly outweigh any concerns about a two-out scenario as far as I'm concerned. YMMV Blue skies, Winsor

Not at all. The ribs on a frap hat can focus an impact on one of the plates of the skull, thus increasing the likelihood and severity of a skull fracture. The utility of a frap hat is for carrying gloves, altimeter and whatnot, as well as keeping a dirt-alert against the ear and reducing injury from sharp metal in the airplane. For protection against impact a frap hat is junk, and may well be worse than nothing at all. I wear frap hats, and try not to hit my head. Blue skies, Winsor You can't really believe that crap. Any protection is better then none. The ribs in a frap hat are 8/9 inches long and any impact would be distribute the impact over the length of the rib. When you work cutting fire wood, do you wear gloves? That thin piece of leather gives you some protection. Come on people get serious. You weren't paying attention. I wear gloves, but don't expect they'll do a whole lot of good against a chainsaw or lawnmower blade for example. I wear a frap hat, but don't expect it to do much more than keep from minor cuts or trivial bumps in the airplane. Even a hard helmet is no guarantee of survival from a freefall collision, not to mention an out of control landing. Necks are pretty fragile, all things being considered. Protective equipment is a good thing, but so is a certain amount of skepticism. It's a bad plan to expect any one thing to carry the day, and the best thing any expensive headgear can do is to convince you that you don't want to lose money by having it get dinged - particularly if your head is in it at the time. Though gear fear is a bad thing, it's a good idea to plan the jump as though your helmet won't help you and you'll be under reserve at a low altitude over the worst real estate in the vicinity. By the time you get in the door, however, you should have planned properly so you can trust your equipment and procedures and go for it. Blue skies, Winsor

IIRC the term came from an incident related to a bad spot in the '70s. A parachutist landed out, and the farmer who picked him up asked if his airplane had been on fire. When told that the airplane was working just fine, the farmer inquired "then whuffo you jump?" Thus, the term whuffo refers to the clueless groundbound moreso than those who simply haven't jumped. Many who have not will tell you they "always wanted to," and sometimes it turns out to be the truth. Blue skies, Winsor

Not at all. The ribs on a frap hat can focus an impact on one of the plates of the skull, thus increasing the likelihood and severity of a skull fracture. The utility of a frap hat is for carrying gloves, altimeter and whatnot, as well as keeping a dirt-alert against the ear and reducing injury from sharp metal in the airplane. For protection against impact a frap hat is junk, and may well be worse than nothing at all. I wear frap hats, and try not to hit my head. Blue skies, Winsor

Changing the order is a good idea. Like the observation that you can smoke then drink but had best not drink then smoke, sky then scuba is a whole lot better than scuba then sky. Getting bent sucks. Blue skies, Winsor

Okay, okay, so it's a bad idea to try to land a cheapo as though it was a Sabre. For those of you who don't already know, burying the toggles on a modified round does not induce a flare - it results in an immediate SINK. Should you apply both brakes vigorously at around 20', the amount of time you have to set up for a PLF will be reduced severly. If you are jumping a round like it's a round and are already set up for a PLF, it will just be a bit more vigorous a landing than usual. If, however, you are lacksadaisical and expect to snap into PLF position at the last second, there's a good chance you can hit asymmetrically and break something (like a tarsal). This is particularly true if you're wearing TEVAs instead of Paraboots. There's nothing wrong with an old 7-TU if you jump it accordingly. If you wish to make it up as you go along, the "if you're going to be dumb, you have to be tough" rule of thumb applies. Blue skies, Winsor

Uh, I landed my 99 loaded at 2:1 last week with the pilot chute inflated. No biggie; it just flew kind of funky but landed as softly as I could have asked. Blue skies, Winsor

My highest is something like 23,500 feet out of Mullins' plane. One's blood boils at something like 64,000 feet, but you'd surely get bent well below that altitude. You first. He can make it if he maintains a nominal 3.7:1 glide ratio from 30 k, to include the canopy flight portion. If he has really honking tailwinds (often available at altitude) and substantial throw from the aircraft pointed at France on exit, perhaps in a slight climb at as high a speed as he could handle, he can make it. I jump for fun, and this would not appear to qualify. Blue skies, Winsor

49:17

Driving is more dangerous than skydiving. Well, at least if you are driving to the hospital to get your stomach pumped after finding that the aspirin you washed down with tequila were actually quaaludes, and you only have a car with bald tires and bad brakes at the top of the mountain with winding roads without guardrails between you and medical attention. Under normal conditions, however, skydiving is one hell of a lot more dangerous than driving. Blue skies, Winsor

Canada Short season, otherwise great. Germany Reasonable and very nice. Switzerland Short season, costly, good community. Austria Most expensive, limited jump window. France Reasonable with outstanding infrastructure. Italy Great fun, but too long ago for opinion to matter. Scotland Great fun, but too long ago for opinion to matter. Blue skies, Winsor

For anyone coming to Rantoul who is interested in jumping rounds, we will have a variety of airworthy gear at Load Organizer Tent 3. There will be at least a couple of ParaCommanders D-bagged in Wonderhogs with BOC throwouts (no CYPRES) and likely the odd cheapo. If you're bringing any kind of a round, please touch base so we can organize an all-round formation. Perhaps we'll see how many people we can get into a baton-pass dive; at Quincy all we got was a two-way. In any event, for people who have never jumped a round this is an opportunity to experience the best of the breed. Blue skies, Winsor