Hooknswoop

I'm sure Quade can do a much better job w/ this one, but this is my understanding. The shape of the airfoil determines where the low pressure above the wing is centered. If the low pressure is located near the nose of the canopy, front riser pressure will be higher and the canopy more resistant to collapse. If the center of lift (low pressure) is located farther back, the front riser pressure is lighter, but then there is also less force pulling on the lines and more prone to folding under. A canopy is restrained from folding up by your weight and the lines. It can fold downwards. What keeps a canopy from folding down is the pressure differential between the top and bottom of the canopy and it's rigity from the ram-air coming in the nose. The steeper a canopy is trimmed, the faster it will fly, creating a higher internal pressure, all other things being equal. Turbulence pushing down on the canopy can cause any canopy to fold under if it strong enough. So it seems to me that a canopy w/ high front riser pressure is more resistant to having the nose fold under. Of course, hook turners like a low front riser pressure for those long dives. What is the right answer? That's for the guys w/ the cool CAD progams to figure out. Hook

The amount of bow or slack in the steering lines is controlled or set by the length of the brake-to-toggle line. The lower you set the toggles, the more slack in the steering lines in full flight and vice-versus, but not on opening. Setting the toggles low or high will not change the amount of steering line between the canopy and the riser, because the brakes are set and the brake setting is not affected by toggle position. To change the amount of steering line between the riser and the tail of the canopy you have to change the length of the line between the brake loop and the tail. I wouldn't recommend changing that setting unless you really know what you are doing. Hook

Line Dump What is it? Line dump is when the pilot chute pulls hard enough on the bad and/or the line stows that hold the bag closed are loose or small enough that the canopy is yanked out of the bag before the lines are taunt. The canopy begins to inflate and then the lines go taunt, resulting in a hard opening. The opening would be very hard and cold result in injury and/or equipment damage (broken lines, torn fabric, etc) For this to happen, the line stows that hold the deployment bag shut must be released before the line tension would release them normally. If the other, non-locking stows released early, the only difference should be a faster, not harder opening. How loose would the locking stows have to be? That depends. Size of the deployment bag, distance between the locking stows, weight of the bag, amount of force the pilot chute delivers at your opening speed are all factors. Taking some measurements on an old J3 main deployment bag, I found that the bag is 13 inches wide. This is how far apart the line stows are. The locking stows are 5 inches apart. If you make 2 inch line stows, you have 8 inches of line on the outside of 2 bands with 13 inches on line between the bands. So there is 5 inches more line between the band. Since there is more line between the stows of the stows, the line between the stows is heavier and if you accelerated the bag enough, the lines would be pulled out of the stows, creating line dump. The line stow bands would have to be loose or the bag accelerated at a pretty high rate to achieve this. The heavier the line and the farther apart the stows, the bigger the problem. Why not make line stows that put an equal amount of line outside the stow as inside? The larger the stow, the larger the chance that one stow could find its way inside another stow, creating a bag-lock. Also, larger line stows tend to turn the bag. As a line is pulled out of the stow, the bag is tilted at an angle and is exposed to the relative wind and it is easy for the bag to spin. The same thing happens with very tight stows, the bag spends more time tilted at an angle, possibly being spun by the wind. Now look at the old style J3 bag again. The locking stows are 5 inches apart. If you make 2 inch stows, there is 8 inches of line outside the stows and 5 inches between the stows. The line outside the stows is heavier and high acceleration of the deployment bag does not tend to create line dump. Acceleration tends to hold the stows in place until line tension pulls them out. Only if the locking stows were to break, allowing the canopy to come out of the bag could the locking stows line dump. Looking at a J3 reserve free-bag, the locking stows are only 4 inches apart, so there is even less weight between the locking stows. Looking at reserve packing instructions, I found the Dolphin manual says 2-3 inch locking stows, the Mirage manual says 2 inches for micro-line and up to 3 inches foe Dacron line, and the Reflex manual says 1 ½ inch locking stows. I have used Tub Stoes for thousands of jumps and have never experienced a hard opening that I could attribute to line dump. Mr. Booth, we could use your experience w/ this one. Hook

Thanks Chris, I have wondered how skydiving ops compare to GA. How much does high gross weights, aft CG's, pressure for fast turnaround times, aircraft modifications, maintainance, and pilot training contribute to that statistic? In your opinion, what change/improvement would have the most effect on reducing jumpship accidents? Do you think that change/improvement to the way things are done is realistically achievable/implmentable? Hook

A terminal reserve ride is no walk inn the park either. I know of two back injuries from terminal reserve deployments. As long as the last two locking stows are tight enough to keep the D-bag shut until line stretch, line dump shouldn't be an issue. i've deployed a Stiletto 97 at terminal (or a little faster, high altitude, on my back) using a reserve style D-bag with the lines stowed in a pouch and the last two stows in a bungee locking stow w/ soft openings. It just took less time for the canopy to come out of the bag. Hook

Dan- So the one (tandem main) I saw was a prototype? It is the one that had the close encounter w/ the Piper Cub. I am still willing to test jump the two Cobalt 95'2 w/ differrent line trims to compare front riser pressure. I am also interested in an update regarding the wind tunnel testing. Hook

Dis-connectiong an RSL and attaching it to the cutaway housing won't present a problem is most cases. Make sure you don't wrap it around the risers or anything. I can't think of any systems that it would present a problem on. Anyone else think of any rigging problem w/ a disconnected RSL? I would recommend not letting flop around freely. Something to watch out for w/ RSL's: I caught an RSL w/ the small split ring for the quick-release snagged on the white loop of the 3-ring next to it. In a cutaway, the 3-ring wouldn't have released. Hook

Chuck- The Atair tandem main I looked at had a zero P top skin and F-111 bottom skin, was this a prototype or production version? I didn't get to see it fly, but looking at it on the ground, it looked very durable. Hook

What ever happended to those two Colbalt 95's you said you could produce for test jumping? How's the wind tunnel testing going? Hook

The wind speed does not change the recovery arc of a canopy- see the downwind turning thread. Hook

They drift w/ the wind, same as a hot-air balloon, but I don't see where you are going w/ this one. Do you understand the fish bowl concept? Hook

Take a look at airliners as they cruise overhead leaving contrails. They fly in a straight line pointed in exactly the opposite direction as their contrail. Now the jet and the contrail may be drifting, but there isn't a crosswind hitting the tail, trying to turn the jet into the wind. The airmass the jet is flying in is moving, same as a fish bowl in a car moving down the freeway. Hook

Sorry, missed the veeertical part:-). a weather vane and a tetrahedron point into the wind because they are mounted on the ground on bearings. The vertical stab of an aicraft only feels the relative wind and relative wind has nothing do do with the wind over the ground. If you took a small remote control boat, and got it going at a constant speed across a smooth river and then locked the rudder, it would hit the other side perpindicular to the river, downstream of where it started. It would not turn up or downstream. if you were above a solid smooth layer of clouds under canopy, there would be no way for you to deterrmine which way the wind was blowing or how strong. The canopy would not automatically head in any direction. Same as the goldfish example, the fish has no idea that it is doing 60 mph, it swims happily around it's bowl, it doesn't swim in any particular direction just beacuse the water mass it is swiming in is moving in any particular direction. Hook

That doesn't work, a canopy won't fly backwards in a wind tunnel. Try this: close your eyes under canopy (do a hop and pop w/ no one else in the air) put your hand out and feel the wind in steady-state flight. Turn 180 degrees and let the canopy return to steady state flight. Feel the wind again. It will feel exactly the same. Without looking down, you will have no idea if you are going into with or cross wind. If you let the canopy fly down wind, any turbulence that turned the canopy would turn in the direction of into the wind. Hook

"An aicraft flying North in an airmass moving West does not have a tendancy to turn left. -------------------------------------------------------------------------------- Horse Hockey! It's called "weathervaning". The force on the aircraft's vertical stab will tend to turn it into the wind. The thrust of the engine propels the plane North, but put the stab in neutral trim and there will be a tendency to turn left." The aicraft's ground track would be NE w/ a North heading. The stab controls the pitch axis and has nothing to do w/ left and right, only up and down. Think of it this way: Put a goldfish in a fish bowl next you in your car. Drive down the freeway, would the fish know that it was travelling 60 mph over the ground? No, it would swim around normally, unaware that it was cruising down the freeway. Wind is an airmass moving across the ground, same as a fish bowl (well not the same, but same concept). A canopy flying through this airmass that is moving across the ground has no idea which way across the ground the airmass is moving and therefore is not influenced by the direction the airmass is moving over the ground. Drop a canopy with no pilot, just weight, at any airspeed/altitude and watch which way it goes after deployment. -- the tests I spoke of were with 500# of weight, from 250 feet, static lined at 125 knots, ground winds 15 knots. Canopy opened on line flight and immediately turned downwind every time.

So you are saying that if a a captain of an airliner turns off the heading control part of an automatic pilot, but leaves on the altiude control part and the aircraft is flying into the wind, the aircraft will do a 180, and stabilze on the new heading? And an airliner heading downwind would not need input from an auto pilot or pilot to keep the aicraft pinted downwind? As a pilot, you know from experience this isn't true. Hook

A canopy has no way of knowing which way the wind is blowing. I suppose that if the canopys were opening 180 degrees off heading, you could have dropped them going the other direction and they would have turned into the wind. If canopys had a tendancy to turn downind, then aircraft would also. They don't. An aicraft flying North in an airmass moving West does not have a tendancy to turn left. Hook

I would contact the manufacturer and let them know what happened. More than likely they will make it right. Did you buy it new? Hook

It isn't TSO'd. 240 lbs. is the manufactures recommended maximum suspended weight. Hook

Is therre only 75 jumps on the canopy? What is the new problem? What kind of gromments does you slider have, what type of lines? What kind of canopy is it? Hook

The whole canopys naturally want to turn downwind topic came up again this weekend and got me thinking as to why people think this is true. Let’s agree on a few things first. 1. Windspeed is the measure of the rate of movement of air across the ground 2. Airspeed is the measure of an object moving through the air. 3. A canopy with a normal forward airspeed of 30 mph will have a 30 mph airspeed regardless of the windspeed. 4. A canopy’s groundspeed will be affected by the windspeed, but it’s airspeed will not. 5. Turbulence can cause a canopy to turn. 6. Jumpers tend to only concentrate on keeping the canopy pointed into the wind on short final (except for short spots). 7. The most turbulence can be found near the ground from interaction between the wind and objects on the ground and thermals are more prevalent near the ground. Because the only time a jumper is paying very close attention to keeping their canopy pointed into the wind is on short final, at low altitude in the most turbulence, any turn resulting from turbulence will turn the canopy downwind, because any turn when you are into the wind is downwind. On the same principle, if everyone flew short final downwind, any turbulence induced turn would cause the canopy to turn into the wind leading people to believe that canopys naturally weather-vaned into the wind. A canopy has no idea which way into the wind and downwind are and has no tendencies to settle out on an into the wind heading or a downwind heading. The entire “downwind turning tendencies” is a myth. Hook

Hook Turns I got these questions a while back; > When you are doing hook turns what are you thinking > about on your > approach? Adjusting my approach speed and altitude to set up for the hook, identifying all the canopies in the air w/ me by type, location, pilot, and predicting their flight paths for the time that I could have a conflict w/ them, Go/No-Go decisions as I set up, each point in the sky I have to get a mental "Go" to continue w/ the hook. At the altitude you actually go inverted? (I don’t go inverted), Adjusting the rate of the turn, checking on the traffic that may be potential conflict, feeling where the canopy is and how much energy is stored in it. > As you are hanging > on the front risers? Checking on the traffic in the immediate area, feeling the rate of riser pressure increases, feeling the recovery are and w/ those 2, timing the amount of "double-fronts" I need to complete the landing w/ the most efficiency When you are flying straight > down where are you > looking> Straight down? 45 degrees in front?? Mainly forward, but left and/or right to keep track of traffic if necessary. I'm > trying to understand > the thought process.. > I don't have to think what should I think about, it is a mental "flow", smoothly transitioning from perception to perception, several at a time, with usually the thoughts overlapping. The actual landing is mainly by reflex, same set of variables every time, same set of responses to those variables, with a large percentage of my focus going to identifying the unexpected and dealing with those issues. The hook turn isn't going to hurt me, the bird flying in front of me, the dog running out into the landing area, the pilot doing something they shouldn't is my main concern, and that is what I spend most of my focus on. Usually, nothing unexpected happens and the actual landing doesn't take much thought to do, so that when something does happen, I have the brainpower available and ready to act to handle the unexpected. The same way flying an airplane. It isn't very hard, but turn off the engine and then see what happens. In pilot training, they train you to fly, then really focus on how to handle emergencies. So for the most part, flying is pretty easy, because you can handle flying it when everything is hitting the fan, so with everything working, it isn't that difficult. Glider pilots get one shot at landing, if they overshoot or come up short, that's it, they miss. If you take an experienced glider pilot and put him in an airplane and tell him to land, it will be extremely easy for him. No pressure. He can miss the runway a bunch of times, and all he has to do is hit the throttle and try again. To him, the throttle is a luxury that he isn't used to. If the engine quits on him, he simply reverts back to what he is used to doing, landing w/o the engine, no big deal. So train for when things are not going right and be comfortable in that realm, then do it the easy way. So that when it gets tough, it is no big deal. People that say I am bound to get hurt do not realize that the landing for me is quite easy and that I am fully prepared to deal w/ the unknown. That isn't to say that I have thought of every possible contingency and could never possibly get hurt, but my level of risk is the same as or less than someone that flies at a much lower wing loading and does straight-in approaches. I am ready to deal w/ the unknowns at least as well as the people that are certain I will be injured landing the way I do. I read books on Crew Resource Management, flight discipline, I study accidents, aircraft, car, canopy, anything. The thought process and mistakes that lead to canopy accidents are not specific to canopys. Before jumping a new gear set-up, I review what is different, what problems those differences those could cause, how to prevent those problems from arising and how to deal w/ them if they arise anyway. I evaluate the risks and determine if they are acceptable. This process is either not done or poorly done by newer jumpers simply because they do not have the experience, and they tend to not listen to the more experienced canopy pilots that could help them with their risk management. This process is not visible and it appears to people that I do things, “shooting from the hip”. To jumpers that have no intentions of pushing their limits flying their canopy, I appear reckless. To jumpers that want to push their limits, I appear to simply go and do it, without any preparation or forethought and they think this is they way to go. How many people have pulled out their hook knife on opening, just for the training value? How many people have practiced dropping a toggle to simulate the line breaking and transitioning to rear risers? I have and I continue to “what if” scenarios and solutions to deal with the unexpected. I stay current on my canopy and I self-critique every landing. I set a high standard for what I expect from myself for every canopy flight and I accept no excuses for poor performance. I stay in shape. This sport is full of self-proclaimed experts. The true experts realize that they don’t know it all. They continually look to improve and don’t let their ego get in the way of admitting they are wrong. They update their thought processes as either the right or a new way of doing things are discovered. This is a passage from one of my favorite books: “The following spring, Gill returned to the Black Hills, where the Needles are located, to attempt the climb. He climbed up and down the lower half of the rock over and over, memorizing the moves and building confidence, “getting it wired.” He says that “going up and down, up and down, eventually I worked myself in to such a fevered pitch that I committed myself to the top portion and very fortunately made it. It’s like a lot of other sporting activities. You not only get psyched up but almost become hypnotized or memorized to the point where your mind goes blank, and you climb by well-cultivated instinct.” Climbing the Thimble marked a turning point in Gill’s life. Soon after that he got married and stopped doing climbs that he considered risky. “ I think risk can be addictive,” he explains, “and I didn’t want to become addicted. The intensity not only increases but changes in character when you climb things you simply cannot afford to fall off of. It’s difficult to put into words, but I found myself going into almost a different state of consciousness when I was climbing unroped in dangerous situation. My limbs became very light, my breathing altered very subtly, and I’m sure there were vascular changes that I wasn’t really aware of at the time. I noticed that I went into this different physiological configuration on life-threatening climbs. It was exhilarating and very intense, but almost in a relaxed way. There might be gripping moments, but there would still be this thread of relaxation throughout the whole climb. It was fascinating, but I didn’t want to get hooked on it.” That Gill was so much better than the other rock climbers of the day can be attributed to his experimental, open-minded approach. He trained intensively on gymnastic apparatus when he wasn’t on the rocks, building strength to the point where he could chin himself while hanging from a single finger. A longtime student of Zen, he prepared his mind as thoroughly as he prepared his musculature.” Hook

If you can hook turn a canopy and land it, you can fly it straight in and land it. A downwind straight in landing will hurt a lot less than a low altitude emergency turn without enough altitude to complete the turn. It is a matter of horizontal vs. vertical speed. Sliding through the grass at 30 mph (horizontal speed) may give you a nice rasberry, but hitting the ground at 30 mph (vertical speed) will bust you up. You can reduce you vertical speed to zero even landing downwind, but if you turn too low......... Hook

744 mph w/ the mouse adjusted, optical and cordless :-) Hook

I got bored at 526 mph Hook