eames

First of all, this sucks. I just heard. I can't believe it.... Personally, and I think everyone agrees here, I would never try to catch a main. But I wouldn't try to catch a freebag and PC either. I've discovered that a PC can, in fact, cause a considerable amont of discomfort. And there's no doubt that it could cause a malfunction, too. But anyway.... I have a simple suggestion. I had a cutaway last week and my main got lost in the most hideous swamp/jungle I've ever had the displeasure of hacking through.... There was only one reason I was able to find it: As soon as I landed under my reserve, I took my video camera off my head, zoomed in on the canopy, and recorded exactly where it landed. If you do this, and you have a GPS, you can set a way-point where you landed, set another one in the line of site of where the canopy landed, determine a heading, grab a compass and go for it. I suppose you could do this without video, but it's easy to forget exactly where it went down, especially when everybody and three of his best friends are telling you that it landed in a thousand different places. I guess this would be a bit more difficult for those flying bigger reserves, because the main might land first, but it worked well for me. And if you're doing video and you see someone else's gear going down, why not just video it? -Jason

That's right folks, Team Mirage will be at Skydive Orange May 14-16! Don't miss this unique canopy flight event! Registration for this event is $20 and will include: One-on-one canopy coaching for all levels, with landing video and debrief Entry fees for the Sunday morning swoop competition (participation not required) The team will also conduct various high-performance exhibition landings throughout the course of the weekend. Team Mirage is a factory sponsored swoop team comprised of Jason Eames, Dave Hebert, Kevin Love, and Hans Paulson. All of the members of the team are pro-level swoop competitors and USPA instructors. Event schedule Friday, May 14th: Registration begins. Exhibition landings will occur throughout the day. Saturday, May 15th: Registration continues. Coaching begins for registered participants. Participants will exit the Otter on 7500' low passes. Coaches will be determined on a rotating basis and participants will be coached on a first-come-first-served basis. Participants should speak with coach prior to boarding the aircraft to asses goals and to plan each landing. Video debriefs will occur directly after each landing. Sunday, May 16th: Registration is closed. Swoop competition for those registered participants who are interested in a low-pressure, low-key, fun introduction to competitive canopy flight. This competition is intended for canopy pilots at all levels. Participants of the swoop competition should intend to perform thier current approach and landing techniques, simply applied to a swoop course. Handicaps will be awarded on the basis of jump numbers and/or canopy size. Events will include distance and accuracy. Medals may be awarded. Coaching will continue after the completion of the competition. See www.skydiveorange.com for directions.

I won't argue that people will make mistakes and gross miscalculations, but such mistakes have the gravest consequences in canopy piloting of all the skydiving disciplines. It's the responsibility of each individual to approach this new discipline carefully and vigilantly, even if that involves some degree of reading between the lines. No amount of correct verbage will keep everyone safe. Well, I've never seen anyone compete without having donned her or his gear.... Jason

First, this really shouldn't be an issue... skydivers shouldn't learn how to calculate wingloading by reading the rules of a high level canopy piloting competition, and even if they did, if they haven't figured it out by the time they're ready to buy a high performance canopy, then they certainly have bigger issues to deal with. Furthermore, exit weight is implied well enough (did the wording actually confuse someone that you know?); I don't know anyone who has inferred the wrong meaning. Second, if you want to be picky, your definition could be the cause of an even worse miscalculation.... By not specifying units, a skydiver could come up with any number of incorrect wingloadings. Airliners have crashed for that very reason. Jason

I agree. It's also a legal requirement in the U.S..... Not that anybody cares, or course. But technically, to make a legal jump, your main has to have been packed within the last 120 days (not necessarily by a rigger): (c) If installed, the automatic activation device must be maintained in accordance with manufacturer instructions for that automatic activation device.

That kinda defeats the purpose, don't you think? Hooking leg straps together prevents large harness inputs. I make it a point to remove straps so that I can slide my legstraps down to get better articulation. If you jump a small or highly loaded elliptical, whether you do harness turns or not, you have to be aware of where your legstraps are. -Jason

The second one is definitely as complex as it needs to be. It would work no matter what direction or magnitude the wind is blowing or what direction or magnitude the airplane is moving. You just have to plug in the right numbers. -Jason

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

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

Hey, that canopy looks conspicuously familiar! Doesn't happen to be a VX 109 does it? ;) -Jason

This is (of course) a better way to do it. But it took doing it with the real numbers to understand why. Now I really have it down... conceptually and practically. Thanks for the quiz. -Jason

I hear bells ringing.... Now that I think of it, who cares about 50 ft/sec x 11 sec? That's not how fast the plane is flying through the upper airmass. 140 ft/sec x 11 sec = 1540 ft in the upper airmass. -90 ft/sec x 11 sec = -990 ft (because of the difference in speeds of the air at exit altitude and opening altitude). 1540 ft + (-990 ft) = 550 ft Ding, ding, ding. Man, if I had only plugged the numbers in according to how I've been preaching the whole time! Sorry for being slow. Yay, we all agree! -Jason

Can you explain to me why I'm wrong?

I don't think I'm considering the ground at all. In fact, if the guy in the balloon saw another balloon in the upper winds, and used his handy laser rangefinder, he would see it moving 90 ft/sec. He would still see the Otter moving at 50 ft/sec in the other direction. The Otter and the upper balloon would be moving away from each other at (90 + 50) 140 ft/sec. So the groups gain 550 ft of separtion from the upper winds and the plane, then lose 440 ft due the first group reversing direction in the lower winds for the 11 seconds before the second group opens. Would you explain to me why I'm wrong? -Jason

They are the wind. Uppers and lowers are pointing in opposite directions. 11 sec in the door at 50 ft/sec in one direction, then 11 sec under canopy at 40 ft/sec in the other direction. I guess I'll have to think about it more. -Jason

Don't you have to subtract the 40 x 11 = 440 ft that group one drifts while under canopy since the uppers and the lowers are heading in opposite directions? -Jason

Okay, I think I see where I went wrong. The center of the second group is only 110 ft from the balloon and yes, there is a risk of collision between groups (and the balloon). I think johnny1488 would have been right. -Jason

I figure the center of the second group will be about 1100 ft from the balloon. And No, there's no chance of collision because even if a member of each group tracked right at each other there would still be 500 ft between them. How'd I do? Edit: They may have less than 500' between them if the member of the first group that was heading toward a member of the second group while tracking continued toward him under canopy. But, he couldn't travel 500' in 11 seconds under canopy in brakes, so there's still no change of a collision. -Jason

Depends on the windspeed at altitude (difference between the velocity of wind at jumprun altitude and opening altitude). If the difference is a large, yes, there is something to worry about. This all fits perfectly into the model that has been described. That's fine, I'm not trying to tell you what to do. -Jason

I award you zero points, we are all dumber for reading that, and may god have mercy on your soul. [That was a joke.] I think we're done here. -Jason

By the way, I'm not sure who is left on your side. I believe I can safely say that Hook now agrees with what we're saying. -Jason

Are the jumpers on the ground? Then why would you define separation in terms of the ground? Actual separation (the distance between two groups when the second group opens, with respect to the ground or the airmass) does not change with groundspeed. It only changes with the airspeed of the plane on jumprun, the difference between the velocity of the winds at jumprun altitude and opening altitude, and the time left between groups. That's it. No matter what the groundspeed is. -Jason

That was not advice, I wrote, "By the way, I don't recommend trying it... I hope you found that obvious." Apparently you didn't. I also never said "half a second." You said, "0.5 seconds." Enough with semantics. Do you dispute this? -Jason

Can you get away with using groundspeed as a reference? Yes, as was stated earlier. If that's all you're arguing then, fine, you're right. But if you want to understand the physics of separation, you'll have to let go of the idea that the ground plays into the equation. -Jason

My argument is that separation between groups does not depend on groundspeed. Actual separation (in terms of the airmass, which is all that matters) depends on three things: Airspeed of the plane on jumprun, the difference between the velocity of the winds at jumprun altitude and opening altitude, and the time left between groups. Nowhere does groundspeed factor into separation. -Jason