markbaur

You begin to decelerate with the resistance of the first bight of lines coming out of a stow, and you get a "snatch force" peak when you accelerate the pilot chute itself at line-and-canopy stretch. That is, you feel the snatch force shock when the pilot chute accelerates and you decelerate -- and we hope this occurs before opening/inflation shock. If you want to go slower to reduce opening shock, use tighter rubber bands (experience shows not much effect here, though) and a bigger pilot chute. A bigger pilot chute results in higher snatch force but lower opening shock. Snatch force can exceed opening shock, so a bigger pilot chute can make for harder openings. You are correct in implying that deceleration occurs after the canopy emerges from the bag. If you are an excellent tail-wrapper and the pointy end stays closed, the flat-plate area of the canopy is larger than the pilot chute. If there were no slider or other reefing system, then the description would end here. Since most of us jump slider-equipped canopies, what happens next is more complex. Opening shock occurs when the canopy expands in size as the slider moves down the lines, with the most rapid rate of expansion occuring at the beginning. The rate is regulated by slider size and shape. In general, a smaller slider keeps the lines closer together (longer snatch-force deceleration before opening shock), but comes down faster (less sail area, higher opening shock). A larger slider can increase snatch force, and will generally come down slower, but may allow faster inflation at the beginning. Lipped sliders are an attempt to combine the closer-together grommets of a smaller slider with the sail area of a larger one. The key here is that tail-rolling matters much less than what you do with the slider. For softer, more consistent openings, you have to get slider inflation before canopy inflation, and that slider inflation must happen with the slider at the top of the lines. Roll the tail all you want, but if the slider isn't on the stops when the canopy goes in the bag, the slider will have a head start on coming down the lines when the tail unrolls. If you can pack with the slider at the top of the lines, you don't have to roll the tail at all (unless you need to do so to control the canopy getting it into the bag). Leaving the tail unrolled actually makes it easier to ensure the slider is at the top of the lines. Mark

Is the peak "G" force lower when the opening sequence is longer? Or are you just moving the peak to a later time? Why does moving the peak force to a later time make for a softer opening? Mark

Would you be interested in one that had an in-date FXC 12000 and RSL? I was planning to ask $300, but I'm open to offers. Mark

Lead time for publishing is around 45-60 days depending on the material, so this one was too late to make the April issue. Mark

Your post isn't quite clear, so I'm guessing you're a jump pilot flying tandems in a Caravan or Otter. Sorry, the pilot doesn't get to choose the spot. You can make recommendations, but your job is to fly the altitude, direction, and speed the jumpmaster wants. It is possible to hose tandems with a long enough spot, but tandems can usually pull a little higher to make it back. It is still the jumpmasters' responsibility to spot or ask for a go-around. Your job is still to fly the jump run they've asked for. Mark

I'm not sure I understand. The nose gets exposed as soon as the tail is unrolled, so what does it matter if that's sooner or later? My own experience: nice openings without rolling nose or tail on my FX99 and VX93 -- and my Sabre 135. Mark

I understand that rolling the tail (or nose, or both) can lengthen the time from pilot chute throw to canopy fully open. The longer the time, the lower the average "G" force. It's not the average "G" force that hurts, though. It's the peak. How does rolling stuff reduce the peak "G" force? Mark

Figure $25 or $30 per patch, maybe a little more if the hole is within a half inch of a seam. Depending on where the holes are, one larger patch might be better than a couple smaller ones. Your best bet might be to do nothing. I've had a small hole on top of the center cell of my FX99, and it's been there for more than 1000 jumps without getting bigger. Mark

I got to help once with an investigation into a fatality that resulted from excatly that stupid idea. I don't want to do it again. Mark

Try this experiment: With your risers assembled correctly, load the three-ring. Watch the middle ring while you change the amount of loop pulled through the grommet. How much does the middle ring move? Does this confirm or refute your hypothesis about a possible spinning malfunction, or is there insufficient information to tell? Mark

Let's be more specific. The 45-degree method isn't effective at any speed, with any size group, or with any length jump run. And whether you apply it literally or not, no angle-based method works. Mark

http://www.tridenthc.com/closingloop.htm Mark

Replacing the velcro on your bridle is not hard. You'll need E-thread (paragear.com or dj-associates.com), velcro (Paragear, again), and a size 18 needle in your home sewing machine. When you're done, take it to a friendly rigger for a sprinkling of pixie dust and holy water. Your home machine may be able to do the velcro on the container, but you'll need to plan your stitch pattern, since the rig won't fit under the sewing machine arm. Some rigs may require opening up the corner seam -- definitely rigger work. If you decide to try it yourself, a few dabs of hot glue will help keep the velcro in place. Your friendly rigger should take a look at your completed work. It's almost always easier to do container work when both parachutes are out, preferably disconnected. Your profile says "Talon 2." I just looked at one, and the only velcro I found was the idiot patch, the little square on the bridle and its mate on the top flap of the main container. The purpose of the patch is to insure slack above the pin. If that velcro is worn, it's not a big deal -- if it were gone entirely and all you did was match up where the velcro used to be, your rig would still be as secure in freefall, and would open up as well when you throw out your pilot chute. Mark

An applicant for a USPA I/E rating must hold an FAA senior or master rigger ticket. Mark

Since you are an Instructor Examiner, you hold a rigger rating. Use the privileges of your rigger rating to replace the velcro. Mark

The warning sticker on the control unit reads, "Caution. Main canopy opening must be 1500 feet minimum above the unit preset release altitude." [My emphasis.] Mark

Probably won't be. The winds were 30kts at altitude, and there are a few folks insisting the method works in no-wind conditions. Mark

The jump pilot may be required to broadcast an advisory, but other airplanes are not required to have radios to land at an uncontrolled field or to fly over an active drop zone. Broadcasting on a radio does not guarantee safety nor ensure awareness. Mark

A 9-cell elliptical made by PISA, perhaps in the mid 90s. What fabric was it made of? How well did it open? Flight characteristics? Pack volume? Any info appreciated. Thanks! Mark

Not enough information to tell if you got it right. The link should pass through loops on both sides of the bridle. The picture shows it going through at least one, but it's not possible to tell if it goes through the one on the other side. Mark

Not only could it happen, it has. Read this story. Mark

Get a rigger to check. And if you've been pulling the rig toward the bag when you pack, it's time to start using a drag mat, or moving the bag toward the rig. Mark

Thanks for the reply. The incidental business insurance available for homeowners requires coverage for "completed operations" as well as for loss and premises liability. I haven't found a carrier willing to insure for just loss and premises liability. The problem lies with "completed operations." For the insurance companies, this means I have to deliver a parachute that is definitely going to work, that there will never be a claim (or at least, there will never be a substantial claim) based on a parachute's failure to work. Incidental business coverage contemplates nuisance claims, not the major claims of a parachuting injury. If you know of a company that would knowingly offer incidental business coverage for parachute rigging in any of the 50 states, please let me know. Ask your insurance agent what he or she thinks (if you can do that without putting your homeowner's policy in jeopardy). I think you'll be dismayed. Mark

I'm a hanger-upper. It's easier to get a light to shine along, onto, or through the canopy that way. Some cells are too small to crawl into, so hanging by the trailing edge means I can pull the cell taut and see to the end on those small canopies. And hanging makes checking line continuity a snap. Mark

That's an okay method for inspecting the top. Do you use the same method for the bottom? How about the insides? Mark