markbaur

That's what I wrote. Arrows, airplanes, and parachutes tend to keep pointed into the relative wind. Mark

Cypres? Mark

Quite the contrary. What matters is where the center of pressure is with respect to the center of gravity. Arrows, airplanes, and parachutes have a larger side-surface area aft of the CG, so tend to keep pointed into the relative wind. You can design a parachute with a more aft CG (and some folks have tried, as a way to reduce the force needed for front riser maneuvers), but it turns out to be more unstable -- the nose tends to collapse more easily. Mark

Great idea! Some places are already doing this. It saves time, plus having just one instructor giving signals simplifies the debriefing. Mark

I jump a Sabre 135 from time to time. When I pack it, I don't roll the nose or the tail. I don't "set" the nose way back. I don't clean out the inside, or carefully flake between the lines either. I get smooth and fast, but not hard openings. Lines straight, brakes set, slider unstowed and up against the stops, pilot chute cocked, locking stows in good condition. Not much else to this packing stuff. Mark

I appreciate the positive affect you've had on language improvement. Mark

I sometimes free-pack the lines on my main, which means the deployment start with "line dump." I still free-pack the lines on my reserve (in the sense that my reserve doesn't use rubber bands). The lines in the free bag pocket usually don't dump out, but there's not much slowing them down as they emerge from the pocket. Stowing the lines to PD standards extends the time for accelerating the bag and pilot chute to your freefall speed, so reduces peak snatch force. But there are a number of other things which are more important, such as deployment speed, size of pilot chute, size/weight of parachute. I don't think "line dump" is a significant source of hard openings, so I figure the primary purpose of line stows is to carry the lines away from things they might snag on, like body parts or container flaps. If this is so, the stows can be relatively loose but still functional. Of course, I distinguish between "line dump" and "canopy dump," or bag opening before line extension. I have several experiences with canopy-first deployment at terminal, and don't plan on doing any more. Mark

How about no kicker flaps at all, like a Talon 2? Mark

I've been curious about this for a while. Why might a Talon p/c coil lock, but not a Vector, Mirage, Javelin, etc.? Mark

There are still major manufacturers who make their canopies using two passes of a single-needle machine, and that's what I'd recommend for starters: much easier to get the thread tensions right, much easier to deal with bobbins running out of thread. You'll prefer a commercial machine, if only for the space under the arm. Lots of fabric is going to get pushed through there. A common household machine is adequate for zigzag on fingertraps, but you may need to custom order needles large enough for E-thread. And there are work-arounds for the bartacks you might want on the canopy at the line attachment points and at the leading edge where the pieces join together. Mark

As the student's parachute deploys, his feet swing forward. If the instructor turns toward the student's head, he's turning away from getting kicked. The SIM describes the student's actions at pull time, but doesn't describe what the instructors should do. The standard bottom end sequence for instructors with an unresponsive student is: -- altitude reminder (altimeter tap or wave prompt). If that doesn't get the student started with his pull sequence, then -- pull signal. If the student doesn't start to pull, then -- redock and attempt to assist the student with his pull. If the student resists, then -- pull the ripcord and, depending on the situation, either leave or remain in place to ensure deployment. Timing is important. Starting the bottom end sequence high robs the student of the opportunity to do it himself, and may be the difference in earnng an advancement to the next category. Finishing the sequence low compromises safety. This is a tough sequence to fly, made tougher in the AFF IRC because the candidates will arrive at this point after having experienced 30 to 45 seconds of tumbled exit, spins, flips, and tons of adrenaline, but still needing to make accurate decisions: -- What if the student responds to the alti tap by waving, but just keeps waving? -- What if the student does a practice pull instead of an actual pull? -- What if the student starts to pull, then waves off? -- What if the student pulls on the instructors altimeter instead of the ripcord? Mark

The gear review says the Crossfire is an elliptical canopy. This means that nearly every piece is different, so you'll need quite a few templates. For top and bottom surfaces, the templates are straightforward, but creating rib templates will be a challenge. You might be better off trying a traditional rectangular canopy, to keep the construction simpler. If you are doing a straight copy of an existing canopy, by all means use a factory line set. You don't have to sew down the finger traps (though you might tack them if you want), so experimenting with trim is easy. If you are working on your own design, consider non-cascaded lines, which allow more accurate trim. Mark

I wouldn't worry about copyrights and patents, as long as you are making parachutes for your own personal education and use. When I was making parachutes, I told Para-Flite I needed the poker chips they were using for slider stops, and they obliged by selling me several sets. And after make a couple line sets, I called Django (predecessor of Glidepath and Flight Concepts), told them I was making copies of their parachutes, and would they please sell me a line set or two? No problem there, either. Determining if your parachute will fly straight and turn okay -- that's easy. Figuring out if it is landable -- that's hard, because it's difficult to judge descent rate when you're at decision altitude. What's your plan? Mark

I can believe that reserves are inspected and packed under more controlled conditions than mains, but I'm not sure about being used under more controlled conditions. Who would like to speculate with me that reserves malfunction more often (that is, at a greater rate per use) than mains? Mark

No, because the jumpers continue downward faster than the airplane flies forward. Mark

After the previous group has been in freefall for about 10 seconds, they'll be falling at 120 mph, while the airplane continues at its airspeed of about 80. The distance will be less than the height, so the angle will be more nearly vertical. If the previous group ever got beyond the 45-degree angle, then sooner or later they'll be falling back through the 45-degree line into the unsafe zone. The longer they fall, the worse the separation gets. Does that make any sense? One more time, forget that 45-degree angle stuff. It doesn't work, never has, never will. If you use the 45-degree method, you are relying on luck. Risky business. Mark

My experience is that even with a vigorous slip, it's hard to get the door open more than a few inches. Getting it open far enough to exit safely is difficult, and I would be very concerned about scraping ripcords and pins across the door frame and latch. If you still insist on trying, at least take the front passenger seat out, so you'll be able to push on the aft-most part of the door, where you'll have the most leverage and most clearance for exit. Mark

The exact name for the fabric loop that the medium ring passes through is "riser." A front and rear riser are constructed from a continuous length of nylon strap (webbing), from the connector link where the front suspension lines are attached, down around the medium ring, and back up again to the connector link where the rear suspension lines are attached. Replacing the fabric loop around the middle ring means replacing the riser -- just buy new ones. I don't know a name for the fabric loop the small ring is attached to. Replacing this loop usually requires removing the grommet and a lot of other stitching. That's possible, but if there's damage to the loop, there's probably damage elsewhere on the riser as well. Buy new. Mark

If the winds decrease as altitude decreases, but are all from roughly the same direction, the jumpers would continue to drift downwind, though not as fast. Jumpers wouldn't slide in the direction of flight. Are you describing some kind of illusion, which causes folks in the airplane to think they are seeing a forward slide? Mark

All night jumps are made in the shade. Mark

Does anyone know where my friend could find these dropzones? Skydive Twin Cities is one. Mark

Yes, this is an easy conversion. Given the opening time of the reserve, you might want to keep the tandem Cypres (firing altitude 2000 feet) and raise your malfunction decision altitude, and in turn raise your planned deployment altitude. It remains a tandem rig, though, which means that rental costs will be considerable more than rental for standard student gear. You'll still need a helmet (might be one your size at the DZ) and a jumpsuit (probably custom). Mark

One limit is set by the gear. Until recently, the max suspended weight for most equipment was 254 pounds. Some newer equipment is certified for 300 pounds, which allows for a 265 pound jumper if the rig weighs the typical 35 pounds. There have been some very large students (300+ pounds) who've jumped modified tandem rigs. A second limit is set by individual instructor ability: an instructor needs to be able to fall with the heavier student, and also needs to be big enough to control the student in freefall. A third limit is aircraft. An extremely large student will not fit comfortable inside a Cessna, and there isn't much room on the step, either. Otter/Caravan/Skyvan work okay. Mark

The excellent part of this paper are the sections entitled ""Learning to Fly the Canopy," "Landing," and "Crash Landing," in the 13 pages from page 58 through page 70. This is the part that should be posted for more general reading. The rest of it is a gassy exposition of the Ideal Gas Law (which tells us that a hot, humid day in Houston is like a cool, dry day in Denver -- that's not news), and an embarassing discussion of airfoil performance (no mention of parasite or induced drag, for example). Edit this stuff out, so folks don't have to wade through it to get to the good stuff. Mark

Make sure you have set your brakes correctly. To set the brake, pull the brake line down until the cat-eye is below the guide ring. Put the top of the toggle through the cat-eye, then put the top of the toggle into the elastic hood. If you put the top of the toggle through the cat-eye without pulling the cat-eye through the guide ring, the elastic hood will take the opening load, and the brake will frequently release. Also, if you put the top of the toggle through the guide ring, your brake will sometimes release. Mark