relyon

Been on many a jump together - I'll miss you Ken. Bob

You may want to rethink that Chuck. The factory bridle length for Lightning 176s and smaller is 79". I jumped a stock L-126 and had the bridle/PC half-hitch around a teammate's left brake line during an octaplane 8-way speed team practice jump (similar to how bolas work). Another teammate noticed it before breakdown and it only resulted in one cutaway (me), but it could have been worse. A kill cone helps keep the PC from bouncing around, but it also increases the total mass at the end of the bridle. That in turn increases the chance of an unintentional entanglement on an aggressive dock like I experienced. The way I solved both problems at once without a kill cone was to shorten the bridle until it pulled the PC mesh into the center retraction ring, but not so far as to prevent the canopy from fully inflating spanwise. Of course, YMMV Bob

One memorable hop-n-pop was a 2100' speed 8-plane CRW team practice jump from two C-182s in formation ... with light rain. Bob

Line length and trim are closely related but are distinctly different things. Line length is just that and it assigns the length of the A lines. Length effects the formation plane/stack height, "reactivity" (somewhat subjective), and recovery arc length, among other things (*). Line trim is the difference in length of each additional line (front to back: B, C, D, brakes, etc). Trim sets how "steep" a canopy is and effectively sets the rate of descent with no input, among other things. Lightning trims are ordered sequential, rotation, and demo from "flatter" to "steeper" (**). Sequential was the first trim and rotation has added later (ostensibly for rotation use and necessitating the name sequential for the original trim). Demo came even later in combination ZP upper skin/F111 lower skin canopies where CRW was done during the later stages of a combined RW/CRW demonstration jump (***). See the attached for more details. Bob * Shorter lines do Stalled Canopy Relative Work (SCReW) better than longer ones; "World Record" line lengths don't SCReW worth a damn ... ** A "flatter" trim has less of an angle between nose-tail-horizon than a "steeper" one does. *** IIRC, the late Jerry McCauley worked with PD to develop/test demo trim in conjunction with his duties as a Navy Leap Frogs team member.

The trim tab is a cam-lock type of device that shortens the [front] riser slightly and changes the overall canopy trim. It has the advantage that it doesn’t require any input (pull) once it’s set and is easily popped out to release; the disadvantage is that it can't easily be adjusted ad hoc and might (be) release(d) when that isn’t desired. It’s use has been superceded by adding one or more links to adjust trim where and when that’s needed. I’ve tried just about everything that attached to risers at one time or another but haven’t seen a trim tab used in years (ca 1997). What are often used for CF are:Blocks Loops 2:1s (or 3:1s) Line attachments (notably outside B-lines)Also, if it has a loop it will often be a fairly large one kept open by a piece of wire (often cutaway cable) or surgical tubing. The loop is double layered and the expansion material is between the two layers. Except for blocks wrapped with Vetrap, I don’t have any pictures but can point you to these threads (read all the posts and there may be other threads):2:1 Debate 2 to 1 vs B line attachments Loops on rear risers? dive loop modificationHope this helps, Bob

More of what Chuck and Frank said. I suggest you look at this video and this thread. They document just how fast things can go to hell. When coming to the conclusion "that won't happen to me" as I suspect you will, keep in mind very experienced CRWdogs have bought it after encountering events that were relatively benign compared to the above. None of us wants to read another "no shit, there he was ..." story. Bob

Spider sliders: a long (7+ ft) pilot chute bridle feeds through a channel in the center cell center rib and attaches to a X slider right at the center. Seeing a video of a canopy deploying with one instantly gives one the impression of a spider moving through it's web. For 2-way, yes, and they hold the current world record (16 points in time). Redline competed in 4-way sequential (http://www.omniskore.com/comp/2007/usnats/cf/4seq/601.asp). I'll have to email Craig, Gary, Sharon, and Scott and get their opinions of the canopy. Bob

Sounds like a "spider slider" (ca 1980). Bob

I'm curious. How many how many in-flight complete power loss situations have you dealt with? Making up your own mind as to the proper procedure to be followed at any given time is fine; performing that procedure without the approval of the pilot-in-command is not. Worse case would have been everyone on board and possibly more on the ground were killed or injured, whatever the reason. What you've outlined is a hypothetical outcome from an actual incident that fortunately sounds like it actually ended in the best case scenario. Bob

Parachuting, not skydiving. Mars Polar Lander tried that in December 1999 after inadvertently cutting away due to insufficient pinchecks. It unfortunately impacted moments later as it had no reserve. Robotic Martian CF someday perhaps? Bob

That may well prove to be a fatal assumption. I've seen entanglements and wraps that made made my hair stand on end clear. I've also seen things I figured were no big deal turn into a complete mess literally faster than one could say ball of shit. All were from altitude. I'd rather follow a cutaway main safely to the ground than impact with it, but YMMV. If you find yourself doing one-way CRW in anything other than a stable biplane, cutaway the main. Use gentle toggle inputs to the dominant canopy in order to steer a stable biplane. Bob

I conservatively estimate I have 140-150 hours or more under canopy and know quite well the theory, formulas, and canopy flight behavior, in addition to actually doing that which I'm discussing. Ironically perhaps, my slider is up and chest strap tight more often the not. I prefer it that way for reasons I choose not to get into. Just because one thinks something is or isn't happening doesn't make that the case. The lack of understanding of canopy [aero]dynamics doesn't mean it suddenly doesn't apply. Bob

All true, but the actual amount of that effect is overestimated and it does less than it may seem, even though it may feel like it's doing more. On a stock Velocity 75 with 18 inch risers the distance from the top of three rings to the bottom skin is just over 120 inches. Moving the three rings apart 6 inches (3 inches each side) results in less than one tenth of one percent difference in effective span. That's with no slider (RDS) and a competely loose chest strap. The higher lift performance gain is minor compared to the lower drag performance gain that could be realized if the jumper is willing to do what that entails. Alas, RDSs are cool and vinyl suits are geeky ... or so it appears by comparing the relative numbers of each. That is not to say there is no effect on control, since loosening the chest strap does have an effect on that in the way of harness turns. But performance and control are two different topics, albeit interrelated. Bob

Caren, Take a look at http://www.omniskore.com/comp/2007/usnats/index.asp for a few videos from the CF 2-way competition at the last US Nationals. The current world record is at FSC WR. It doesn't get any better than that at present. Say hello to Tom for me. Bob

virgin-burner: I stated "Loosening a chest strap beyond the point there is any tension in it ...", not that the chest strap shouldn't be loosened at all. Also, there are more ways that one to quiet a flapping slider. Stowing it is one way, a RDS is another way, and there are other ways too. pilot-one: There are other ways to do this as well. Longer lines, longer risers, and wider riser attachment points all affect the anhedral geometry in the same way (ie. make the angle smaller). I'm not suggesting these are desirable for a given application, just that they're possible. While admittedly not simple, so does comparing the cos(A1) to the cos(A2) where A1 is the anhedral angle before loosening the chest strap and A2 is the same angle after loosening it. Anybody who thinks it makes a big difference has never done the calculation. So does shortlining, though that brings with it undersirable characteristics as well and is probably not the sort of fun a swooper is looking for. Very wrong. Loosening the chest strap is key to flattening the wing by separating the anchor points of the suspension lines. The wider the better. ... It's physically impossible to make the canopy wider than it is completely flattened out, but even that point can't be reached. The more a canopy flattens, the more the spreading force provided by the anhedral geometry diminishes. Well before it reaches the optimum flat geometry is will collapse; the internal pressurization alone in a ram air canopy is completely insufficient to keep it open. Bob