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

While not at all directed at solely at you, in light of comments such as these I'm curious as to other people's opinions are of an earlier reply of mine. Bob

For all the aerodynamic drag purists out there I'll point out that the largest source of drag in the total deployed canopy system is the suspended human. Collapsing sliders and RDS are mere window dressings until people are willing to wear full spandex/vinyl "style" suits. Allowing risers to spread can have some effect on glide performance though it's effect is often misperceived and usually overestimated. The canopy planform, aspect ratio, airfoil, number of cells, fabric type, line trim, line type, and total included anhedral angle have greater performance implications - some significantly so - than spread risers do. Loosening a chest strap beyond the point there is any tension in it is potentially unsafe and useless except perhaps in classic accuracy competitions. Bob

Not true at all. I've performed many autorotations at zero airspeed as well as forward, sideward, and backward autorotations with varying airspeeds. It's necessary to transition to forward flight prior to touchdown in order to arrest the vertical descent rate and then trade rotor energy (RPM) for smooth surface contact. A power off autorotation from 500 feet the surface to within 50 feet of a predetermined spot is required for the helicopter CFI practical test; I was long by 18 inches. Again, not true. The maximum glide ratio of helicopters varies from just over 1:1 to around 3:1 dependent on a variety of factors, and the autorotative descent rate is 1500 feet per minute minimum and often significantly more. IF the pilot gives the order to bailout, it's imperative to go into freefall and track away before pulling, preferably 90 degrees to the helicopter's flight path. Keep in mind that if rotor system contact of any sort is made it will likely be castophic for everyone left aboad. An open container is likely to be disasterous for everyone except perhaps the individual with the open container. Helicopter rotor systems don't take to contacting anything other than air, rain, or small insects very well. The lack of understanding of this aspect of helicopter operations on the part of the average skydiver is why I'm not interested in being a helicopter jump pilot except in a few very specific types. Bob Commercial helicopter pilot and CFII

Scott, I strongly suggest you view the video I posted a link to if you haven't already. All joking aside and with no offense intended, I highly recommend you leave the bravado on the ground when you jump. CRW specifically and parachuting and skydiving in general have no tolerance for complacency or mistakes. The next jump you make is the most important one, not the one you're on. We'd all like to be doing that with you as contrasted to starting yet another thread in Incidents or Blue Skies - In Memory Of. Bob

I wouldn't use the phrase "the only problem" when referring to CRW and you may want to reconsider using this type of canopy for any sort of contact. See the Wrap that Rascal thread and this video in particular for more. Bob

I packed my tail pocketed Lightning like a reserve with a totally exposed nose, etc. for competition. Barely clearing the A/C out the door almost always resulted in a horizontal deployment with my feet at the horizon. There's sweet spot with fast opening deployments in the 2-3 second range after exiting. That allows the body to slow down horizontally before the vertical velocity builds up too much. I've deployed the same setup in the 8-9 second range due to a dropped PUD and while vertical the deployment was, shall I say, brisk and memorable. It's quite possible to pack a tail pocket for reasonably gentle openings. The two items I've used with great success one or both at a time are rolling the nose extremely tightly to the B lines and not stowing the brakes. I roll all the cells together in one direction. Be sure to clear the stabilizers in all cases as that is a key ingredient in avoiding off-heading openings. Many are wary of not stowing brakes but it works fine for Lightning CRW for several reasons: 1) It slows down the deployment such that the brakes can be grabbed while the canopy is still deploying, 2) an off-heading opening can be corrected while it's still occurring, and 3) the formation turn and/or collision avoidance can be initiated as early as possible. Bob

He could consider that for each person, but I suspect Bill may instead think "hey, this person could get other people hurt, everyone better be careful" or "hey, this person could get other people hurt, so they can jump elsewhere", etc. Bob

An ELT is just such a system and is exactly where I'd opt to put the identification and GPS position components of ADS-B functionality. The altitude and RF components could be there as well or might be better co-located with a mode C transponder/encoder or derivative. Data and power could be transferred between the two over a NMEA 0183 or USB interface. Far fetched? Look at the ACR Aerofix 406 and ACR Microfix 406. Bob

Very cool. Were I on the load, I'd have been a little concerned if Teuge was closer to Eindhoven, Nijmegen, or Arnhem. Some of the older locals could have had flashbacks. Bob

Being a Gulf of Mexico (GOM) helicopter pilot myself, I can vouch for your comments. Ones eyes and TCAS work fine for traffic purposes but ATC radar is practically useless at the altitudes and range we fly at. The lack of continuous accurate position reporting is addressed but could be much better. ADS-B promises to make every GOM pilot's nightmare - taking a swim close to sundown when no one knows quite where you are and they can't get to you even if they do - "just" a really bad night. Bob