pchapman

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Which Monarchs are you talking about? There are 2 versions.

Well, that's something I (and probably many others) didn't know about Monarchs...

My current rig:
'94 Racer, FX 88, PD 143 ........ 18.0 lbs
(prior to putting in a Cypres 2 weighing about 0.4 lbs)

My impression is that partially in reaction to heavy rigs in the early days, there was a time when the emphasis was on making rigs as light as possible. It was also a time when rigs were less sophisticated. These days there's all sorts of padding and stiffeners and covers for webbing, while back in the early 80's (?) a rig sometimes had only a single layer of cordura for the containers.

Between all that and lightweight round reserves (and some were too lightweight!), some early rigs compared well with those today, despite bigger mains. For example, my first rig had a Titan 265 in it, but weighed only 20 lbs because it was an early Racer and had a Phantom 24 in it.

The lightest I've seen:
Custom rig, Sabre 97, Phantom 22: ...... 12 lbs.

The custom rig had narrower than usual webbing, no padding, no leg hardware at all (step in, non-adjustable), over-the-shoulder throwout reserve PC (no spring or R/C cable & housing), no cutaway housings (individual cutaway cables at each riser only). Used for years by an expert jumper here in Canada.

(I can't be sure of the accuracy of rigger's spring scale I weighed it with. But 12 lbs can't be too far off since the Sabre is listed as 4.5 lbs, the Phantom as 4.4 lbs, leaving 3.1 for the rig. So under 13 lbs is believable.)

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[...] [H]e often jumps it with a camera strapped to his head.

I'll second the notion that SOME Monarchs may open just fine, even if they GENERALLY are of the early generation of faster opening zero P canopies.

I know a middle aged lady who recently jumped a Monarch 155 for a few years and had no problems with hard openings, while packing it fairly normally (i.e., no super tight rolling). Some of us at the DZ were a little wary of it when she first got it, but it turned out well and I put some jumps on it too without problem.

I didn't cover up the fact that when I broke my ankle, it was from skydiving. Nobody treated me really badly although there was some feeling of, "well what do you expect."

But then it actually kind of impressed people when I followed it up by saying that "it was my first real injury after 950 jumps." It made skydiving actually sound good, for those who had imagined that such an injury would be pretty common, even for those making just one jump.

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Jumper registration begins on July 1, 2006 at 2pm EST (19:00 GMT).

I'm a little confused.

Registration (and/or server crashing) seems to have started 2 pm east coast time, but it's Daylight Savings Time here, which is only 4 hours behind Greenwich, not the 5 for EST. Thus 1900 GMT = 1500 east coast time. So registration should start at 3pm local.

(If my memory isn't wrong, I thought in a previous year the Daylight Savings was factored into the time properly.)

It doesn't matter now for this year, but perhaps we can make it more clear next year.

As my own rigger, a year is fine for me, for a rig that isn't in an extremely dusty or dirty environment, isn't getting an extremly high number of jumps a year, and is getting good external inspections between reserve repacks.

I wrote:
Simply shortening the lines equal amounts will also change the geometric position of the jumper under the canopy in the fore and aft direction (relative to the canopy), given that the jumper isn't

Mick replied:
What the hell are you talking about? Due to the physics of gravity the mass will always center itself under the canopy regardless of the line lengths.

My reply:
Sorry, I wasn't clear on one point, making things very confusing! I hope I can clear up what I mean.

I meant that the simple geometry of the parachute system changed, as would be seen if the canopy were laid on its side on the ground and nailed to the floor. Shortening the lines would move the position of the links fore or aft, and not only closer to the canopy. I wasn't talking about the actual orientation in flight -- which Mick was talking about. But still there can be changes in flight behaviour as I will show.

We are dealing with three effects in a row:
- How much does the shape of the aircraft change?
- How does that affect its orientation when actually in flight?
- How do the orientation and shape changes actually affect flight characteristics?

In flight the mass of the jumper is indeed going to hang pretty much "directly under" the canopy, give or take a little because of the drag of the lines & jumper, and the aerodynamic forces on the parachute canopy (lift, drag, and pitching moment).

(For others to visualize, an extreme example where the pilot is no longer nearly "directly underneath" the canopy can be seen in videos of things like 21 square foot canopies that are not landed. Videos show the jumper pushed well back relative to the canopy, because of the very high speed and thus drag on the jumper.)

The purely geometric issues can be seen in the attached diagram, drawn to scale but with arbitrary lengths and angles.
The canopy starts out with 10 foot front lines, and 13 foot back lines. (For simplicity, the "lines" include the risers.)

[Edit: In the diagram and this post I kept writing "links" but it's clearly the 3-ring suspension point that I mean, where all the lines & risers come together at one point.]

Both are shortened by 3 feet, giving 7 and 10 foot lines. This is a ridiculous amount but makes the principles involved easier to see.

Arcs have been drawn to show where the new lines will intersect, at the "new link location".
The red arrow labelled "1" shows how the lines intersect significantly further back, relative to direction of the lower surface chord of the canopy. The jumper has been moved further back compared to the canopy.

Yes, in flight the jumper's weight will dominate and swing him back "underneath" the canopy again, as Mick said. But that means something else will change: the canopy will be forced to tilt nose up!

If the pitch orientation of the canopy in a normal glide is changed, also affected will be the angle of attack, glide angle, normal (trimmed) airspeed, toggle pressures, stall point, flare ability, and so on.

Shifting the jumpers weight fore or aft is a bit like a hang glider pilot moving himself fore or aft by pulling or pushing on the control bar. Pushing out starts to move the pilot aft, but gravity gets him back "underneath", so the wing pitches up and slows down.

If doing this all relative to the bottom of the canopy seems artificial, then one can just as well look at it in a different way:

Pretend that the diagram shows the canopy as it oriented in normal flight, with gravity straight down. The angles look generally realistic: The jumper is "under" the canopy, and the canopy is angled a little bit nose down from the horizon. Even relative to this in-flight position, one can again see the jumper's position move aft when the lines are shortened. That's shown by red arrow "2". The jumper's weight will tend to swing forward back under the canopy and pitch the canopy nose up.

If the lines are shortened by a given proportion and not a given length, it doesn't fix the problem -- the links again end up at quite a different spot.
For example, the dark green dot on the diagram shows the link location if the lines are shortened by 30%. The front lines become 7 ft long, just like before, and the back lines end up 9.1 ft long.

(If all this is understood, then it is easy to see how the triangles defined by cascaded sections of lines will have geometries that are out of whack, which either mean that some lines would go slack or the canopy will distort in some way to load the lines again.)

I hope all this is adequate to address Mick's concerns.

Overall, I'm saying that there are geometric changes that aren't always obvious, beyond just "putting the jumper closer to the canopy".

Whether small geometric differences will make the canopy fly significantly differently is another matter, which Mick probably can far better address.

This discussion doesn't just apply to line and riser length changes for finely tuned modern CRW or swoop canopies. In the old days one could notice plenty of effect from just adding a single set of extra links to the front or rear risers of a big F-111 canopy.

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A theory comes and the testing doesn't support the theory.
Either we have a problem with the testing or the theory is false.

To add to that, let's remember that saying "the testing doesn't support the theory" may just mean either that "it doesn't tell us anything either way"

We may not have the facts yet to trump theory.

I'm not taking sides, but the answer may indeed be that the testing is the problem. Not that the testing is done poorly, just that one can't do enough of it.

It's a common problem in skydiving, trying to evaluate the probability of unlikely events.

One can do a hundred expensive test drops and have a good chance not to discover something bad that happens only once in 1000 times. (Sometimes the test can be designed to try to make the problem show up more often.)

While it is good to know the positive outcome of all of Mick's tests, some of us may still be undecided about how strong that evidence is in evaluating Bill's theory one way or the other.

Simply shortening the lines equal amounts will also change the geometric position of the jumper under the canopy in the fore and aft direction (relative to the canopy), given that the jumper isn't directly under the middle of a canopy with equal length A/B and C/D lines.

This change will happen whether the lines are shortened by equal lengths, or even by equal proportions. (Since the canopy size isn't being scaled at the same time.)

And either way, any cascaded parts of the lines will load up differently as the cascaded section lengths aren't adjusting for other changes in the geometry.

I can't tell anyone exactly what effects line shortening will have in practice, but I wanted to note that there are plenty of subtle geometric changes that will occur, beyond just putting the jumper closer to the canopy.

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any idea what their track record is? thanks a bunch!

People have already said they have a good track record.

If you're looking for numbers, they haven't had any student fatalities, back at least as far as 1991. (Which is when my personal notes on Canadian skydiving accidents start.) The last experienced jumper fatality was a decade back.

So I think they do have a good track record.

Since I live in Ontario, I only jumped at Eden North when they hosted the National Championships a few years back. They put on a great event.

Canada had an E licence until a few years back when all the licences were redone as part of an international restructuring of licences -- D licences started to require 500 jumps, not 200, that sort of thing.

Our Canadian E licence seemed to be just a "fun" licence as it didn't offer any benefits, other than an exemption from Sporting Licence fees. Some of the qualifications did require a well rounded skydiver, such as having to have an advanced instructor rating, and the basic rigger rating. Other qualifications were a little wacky: Like one jump using an oxygen system in freefall, and 5 water jumps!

In the end only about a dozen people ever jumped through all the hoops to get the "E". Although the licence is no longer issued, those with it get to keep it.

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No, the french word for link is lien.

"Lien" is a link in the sense of a bond, a connection, or now also a web link.

But "maillon" is the French word for a link of a chain.

[outrageous french accent]
"Maillon rapide", eet eez simplee de link dat eez quickky, non?
[/outrageous french accent]

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I jump a Sigma, on which I have found it is possible to overtighten the laterals, making disconnection under canopy nearly impossible.

I also find that very tight laterals can be too tight on the Sigma. (My experience: ~ 400 tandems.) At the DZ I'm at, it seemed to be worse for stability, for example causing more chipping in freefall, as the instructors were forced into a dearched position at their hips. Disconnecting under canopy required more work (like standing on the feet most jumps). And it never seemed to give any benefit, compared to just having tight laterals, in being able to "fly as one" with the student. So at the DZ, after the first year or so with Sigmas, we no longer went crazy in the C-182 trying to tighten up the laterals as much as possible.

(We still consider it very important to have them tight, just not ridiculously so.)

At the DZ we always reconnect the laterals after disconnectig & loosening them.

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I was just conserned to which method was safer, and for some reason I thought that static line was abit more of an old school method vs IAD.

Either method, well done, is safe & effective.

But I'll agree that static line is old school! (I instruct at the Ontario DZ that uses static line but doesn't require 2 weeks of pushups...)

It isn't as popular, it does require more types of gear and more transition training, it is an older technique, and it's not as cool because students aren't getting any real freefall.


Maybe I should leave it at that, but I will comment on a couple things Andrew White mentioned. A lot of what he said is either true in general, or something he has actually seen, but some counterbalancing ideas can be added.

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Our line twist rate was at least five times what it is for IADs out of the same aircraft

True. Off the top I my head, it could be 25 - 50%. But I don't keep track because it doesn't matter much. Yes, students just drift a bit while untwisting.

One hazard might be the occasional student who wants to cut away from line twists despite their training, or who pulls their toggles before untwisting.

As for mals, yes the direction of air flow should make mals more likely. The DZO at the place I jump has a packing method that is supposed to somewhat counteract that. I don't know what the real numbers are, but the DZ has often enough had seasons with zero or one canopy mals when training 500-1000 first timers per year, plus whatever repeats there are. While there's lots of opportunity to debate malfunction rates, I just don't want it thought that direct bag static line automatically means a lot of mals.

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The argument has been made that static line is a more sure way to get 'something' out. To this I call bullshit. The last time I saw a pilot chute in tow on an IAD was over ten years ago.

"Getting something out" is one of the DZO's reasons I believe. When critiquing IAD, I never figured PC in tow was the biggest worry. It was the student tumbling, and grabbing or getting entangled with the PC. That was a significant factor in first jump student deaths in BC in '91, Alberta in '93, and Ontario in '95. The students all had reserve parachutes available so IAD didn't "kill them". (There were plenty of other issues involved.) But IAD is more likely to give a student a nasty high speeed mal than does static line.

There's also the worry about the PC over the tailplane. But that comes down to understanding good ways to do IAD and training instructors appropriately. Just because I know a DZ that twice ripped up the tail of their aircraft due to IAD (in the 80s), doesn't mean other places can't do a lot better!

While static line (direct bag style!) doesn't have that high speed mal issue, it can still suffer from students getting caught up in the lines when backflipping off the step. Or because of the direction the canopy is extracted, a riser can get caught under the reserve pack tray causing a mal. Gear design and packing techniques can minimize this. Still these are valid issues with static line.

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the bridle was stowed correctly. RI changed how the Voodoo's bridle should be stowed.

It gets confusing keeping track of what manufacturers want.

From what I see in manuals I have downloaded:
Talon / Telesis ---- V folds (Vector-like)
Talon 2 ---------- side to side
Talon 3 supplement --- up and down
Talon 3 ----------- side to side
Voodoo ----------- side to side

(And I haven't looked at the Genera, Talon FS, or Telesis 2 manuals yet. They show a Telesis 3 too, but no manual. Oh wait, what's called the Talon FS manual is also called the Talon 3 manual when opened up. RI sure has a lot of names for their rigs...)

The Talon 3 supplement was designed to show people the differences between the Talon 3 and the Talon 2, so they could use the old manual with some changes.

Here one gets into the rules-lawyering. Without phoning the company, how does one know whether that document still applies? The supplement may not now be on their web site, but if there's nothing that specifically withdraws it, are both ways still legal? The supplement has no date to match it with the Talon 3 manual.

(Just rhetorical questions!)

So that's where the pterodactyl logo of Free Flight Enterprises comes from! I had missed the historical connection.

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What kind of loading were you putting on that canopy? a 40+ mph airspeed suggests you were loading the hell out of it!

Everything was loaded with only about 170 lbs -- about 1.4 wing load on the Sabre 120, and 1.9 on the FX 88. (Without getting into different standards of canopy size measurement!)

Unless there was something fundamentally wrong with my data collection, the numbers seem OK to me, and their relationship is reasonable. I got 25 mph under a Manta 288. Basic canopy scaling laws suggest that a 120 canopy would fly 55% faster, or 39 mph. And the 88 at 45 mph. That's if "all else is equal" which it obviously isn't, yet the measured numbers are similar to the predictions. That gives me some confidence in the results.

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First, most canopies have a three-to-one glide ratio.

I know that's the figure that's been used for years, but I don't really believe it.

Hey Walt,
I agree that the 3:1 that people are sometimes taught is too high. I'd GUESS 2.5:1 for the average canopy and closer to 2:1 for small, ground hungry ones, at zero brakes.

The glide ratio in the air does go up with a little brakes, and of course for a strong tailwind like on a cross country, one will pretty much want whatever brake setting gives the lowest rate of descent. (Based on glide polar theory.)

The real data I have is old, from the mid '90s. I got the data with a calibrated anemometer, a variometer, density altitude calculations, etc. A few of the numbers:

At 170 lbs, corrected to sea level conditions for descent rates:

big baffed F-111 7-cell (Titan 265)

-At zero brakes:
2.45 glide ratio
28.5 mph airspeed
16 fps rate of descent

Sabre 1 120

-At zero brakes:
2.5 glide ratio
41.5 mph airspeed
22.5 fps rate of descent
-At an arbitrary "quarter brakes":
2.75 glide ratio
33 mph airspeed
16.5 fps rate of descent


Jonathan 92

-At zero brakes:
2.3 glide ratio
43 mph airspeed
25 fps rate of descent
-At an arbitrary "quarter brakes":
2.6 glide ratio
34 mph airspeed
18 fps rate of descent

Later on I got 47 mph at zero brakes on an FX 88.

The data may help a little in understanding glide ratios even if modern canopies aren't represented.

One method I've used to reduce the effects of expected hard openings is to brace for it -- crossing my arms in front of my neck, tensing and bringing shoulders up and chin down to support my head, preventing it from moving. Very effective for me.

All that is a bit much if not expecting a hard opening. For any opening one can at least face directly forward and not have one's head craned too far forward (or back), which would allow a hard opening to tend to snap one's head forward (or back), injuring the neck.

Of course none of this should stop anyone from trying to find ways to make the canopy open consistently softer.

One would rather have a 'hard opening' with a single rapid but smooth deceleration, than an opening where one gets bounced and whipped around. That's particularly tough on one's neck.

(My hard opening experience was while jumping a Sabre 1 135 during big-way jumps, where from the outer row we had a long track and my flare out of the track was often short.)

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Any other more or less INTELLIGENT questions you have heard?

I'm not sure how intelligent all of these questions are, but it is true that many questions are quite reasonable for people who don't know the sport, even if the questions still sound funny to us. It's the questions that show a total lack of understanding of physics (and not just skydiving) that sound the most stupid.

One whuffo's intelligent comment after watching people land:
"It's weird... the jumpers who look the most out of control ... the ones dropping & spinning out of the sky... they have the best landings."

(It's not true all the time but she had a point!)

As for Burnaby Ontario this weekend, high winds kept us grounded until late in the day Saturday, after which we got 2 Otter loads. Few people were still around for RW, but Jeff Gemmell still enthusiastically organized dives for those of us left: Two 3-way dives!
I don't know how things are turning out today, Sunday, but both actual and forecast conditions were bad so I left the DZ after a few hours. Forecast was for 60 knots and -11 C at 12000 MSL...

There's a well known Parachute Recovery Systems Design Guide available that's written by Theo Knacke, dated 1992. (It's a 512 page manual mainly on round parachute design largely for military purposes, full of detailed engineering.)

I noticed that online at Irvin's web site, there is a 42 MB pdf file of the 1978 "Recovery Systems Design Manual" AFFDL-TR-78-151 by 3 authors including Knacke, that is nearly 500 pages, written for the US Air Force etc.

I don't know to what degree the two are similar, as I don't have the 1992 book, and only just spotted & downloaded the 1978 document. Anyone know?

Is the 1992 book done from scratch by Knacke based on what he learned during his long career? Or it is "just" an big update of the 1978 work that he was a main author on? The table of contents for the two don't look like a close match.

In any case, it looks like if one has a passing interest in the subject matter, the 1978 document would be interesting to download. The 1992 book is likely a 'must have' for people in the industry, but it would be overkill for those with just a minor engineering interest in the aerodynamics etc. of parachutes.

The Partenavia breakup is a well known one among airshow accidents. As I heard it, the pilot's wife was doing the narration for the crowd.

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Still, pulling stunts like that anywhere near a crowd in an airplane not designed for it seems like a really, really bad idea.

For the average pilot, yes. Yet a non-aerobatic aircraft can be flown fairly safely in aerobatics if carefully inspected and carefully flown by a pilot who doesn't make mistakes and knows energy management in order to keep the g's low.

The classic example is Bob Hoover with his Shrike Commander, a plane roughly comparible to the Partenavia. He'd fly part of his airshow with one prop feathered, and then both feathered. (Seen the video where he pours himself a glass of tea while flying a barrel roll? Theres's a link at the bottom of http://en.wikipedia.org/wiki/Bob_Hoover)

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Have you read Pat Work's "The Art of Freefall Relitivework"?

Haven't seen it. I think that was the other RW book available at the time. I picked one of the two available books off the mail order lists...

Just curious whether anyone had found the book of use, or whether it was once popular, way back when.

The book was published in '81 as a guide to RW, and I bought the 2nd edition in about '90 when I got my licence. I was trying to find some source of information on RW and that's what was available to buy.

I found the book quite confusing, partially because I had so little RW experience that I couldn't truly understand its lessons in terms of real experience. A lot of the book dealt with the dive down to a formation and how to approach a formation.

The other problem for me was that I was trained in aerodynamics, while the book had many incorrect statements about physics & aerodynamics. While it doesn't take an aerodynamicist to do good RW, it did take away from the perceived authority of the book.