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#21
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Interesting... is this an active myth in skydiving circles? That some
chutes turn naturally into the wind? |
#22
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Aren't most BASE jumps done without a reserve?
Yes. This may be changing - I no longer actively BASE jump so I have not kept up. Do BASE jumpers prefer the reserve square or the sport chute (since control into tight LZs is a consideration)? BASE jumpers prefer a parachute designed for BASE. Before these were available, most BASE jumpers used parachutes normally used as reserves (the Raven series were quite popular). Some still use them. None used anything even vaguely similar to the modern sport main canopy. Michael |
#23
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I don't think you will find that there are any emergency
prachutes with square canopies, they are all round. Not true. Both Relative Workshop and Strong make emergency rigs that will accept square reserve canopies, and will sell them to you if you convince them you know what you are talking about when you ask for one. They're the only kind I use. Square parachutes while offering more control when open require the wearer to be in a stable position when the chute is deployed, they are therefore less reliable when deployed in anything other than a stable attitude. Not true. Square emergency parachutes are used with freebags (they won't even have a bridle attach point), which allow deployment even if the pilot chute or bridle entangles with the body of the jumper due to an unstable opening. The same is not true of rounds, which are thus more prone to 'horseshoe' malfunctions. Picture what that looks like - if you really want to. The Irvin EB** series were reputed to be the fastest opening chutes in the world at one time and they certainly use round canopies (I24). Maybe they still are, I hope so cos that is what I have. The primary factor affecting the speed of opening (assuming such variables as airspeed, altitude, etc. are kept constant) is the volume of air required to inflate the canopy. Square canopies need less air to inflate, as they are smaller. The can be made smaller since they generate lift, not just drag. Because of this, squares inflate much quicker than rounds designed to carry the same loads - so quickly in fact that all modern squares (other than those used for BASE jumping from VERY low altitude - about 600 ft or less) are equipped with sliders to slow the opening to something only a little faster than rounds. Square sport canopies often have sliders that slow the opening enough to make it 'comfortable' but the emergency parachutes have just enough slider to keep you from breaking your back in a terminal velocity opening. There are actually only two advantages to rounds. The first is cost - old obsolete technology is always cheaper. You can pick up a serviceable round rig for a couple hundred dollars US; a square rig will be newer and more expensive. The second is the reduced need for training. The square parachute is a wing. It must be flown and flared for a landing. Further, for various reasons I will be happy to go into if anyone is interested, it doesn't really fly and flare like a rigid wing. Finding yourself under one with 30 seconds to figure out its flight characteristics and land it in a suboptimal landing area is NOT the hot tip. Much as I dislike rules, I would still recommend a training jump or two for anyone planning to use a square rig without prior experience, as well as briefing from someone who understands both ram-air wing and rigid wing aerodynamics and can prepare you for the differences. Michael |
#24
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Thanks for that. It would seem therefore that the standard
conical chute is the only choice for the majority of glider pilots on the grounds that it is likely that we will only ever use it if we have to.As I have already said, if it is good enough for Martin Baker it's good enough for me. I am firmly of the opinion that people who jump out of perfectly serviceable aeroplanes are .........how can I put it.......... lacking in some way. :-) At 21:30 06 April 2005, Michael wrote: I don't think you will find that there are any emergency prachutes with square canopies, they are all round. Not true. Both Relative Workshop and Strong make emergency rigs that will accept square reserve canopies, and will sell them to you if you convince them you know what you are talking about when you ask for one. They're the only kind I use. Square parachutes while offering more control when open require the wearer to be in a stable position when the chute is deployed, they are therefore less reliable when deployed in anything other than a stable attitude. Not true. Square emergency parachutes are used with freebags (they won't even have a bridle attach point), which allow deployment even if the pilot chute or bridle entangles with the body of the jumper due to an unstable opening. The same is not true of rounds, which are thus more prone to 'horseshoe' malfunctions. Picture what that looks like - if you really want to. The Irvin EB** series were reputed to be the fastest opening chutes in the world at one time and they certainly use round canopies (I24). Maybe they still are, I hope so cos that is what I have. The primary factor affecting the speed of opening (assuming such variables as airspeed, altitude, etc. are kept constant) is the volume of air required to inflate the canopy. Square canopies need less air to inflate, as they are smaller. The can be made smaller since they generate lift, not just drag. Because of this, squares inflate much quicker than rounds designed to carry the same loads - so quickly in fact that all modern squares (other than those used for BASE jumping from VERY low altitude - about 600 ft or less) are equipped with sliders to slow the opening to something only a little faster than rounds. Square sport canopies often have sliders that slow the opening enough to make it 'comfortable' but the emergency parachutes have just enough slider to keep you from breaking your back in a terminal velocity opening. There are actually only two advantages to rounds. The first is cost - old obsolete technology is always cheaper. You can pick up a serviceable round rig for a couple hundred dollars US; a square rig will be newer and more expensive. The second is the reduced need for training. The square parachute is a wing. It must be flown and flared for a landing. Further, for various reasons I will be happy to go into if anyone is interested, it doesn't really fly and flare like a rigid wing. Finding yourself under one with 30 seconds to figure out its flight characteristics and land it in a suboptimal landing area is NOT the hot tip. Much as I dislike rules, I would still recommend a training jump or two for anyone planning to use a square rig without prior experience, as well as briefing from someone who understands both ram-air wing and rigid wing aerodynamics and can prepare you for the differences. Michael |
#25
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I'd consider installing a ballastic parachute and riding the damaged
glider to the ground surrounded by the cockpit. Charlie "Lite" |
#26
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I'd consider installing a ballastic parachute and riding the damaged
glider to the ground surrounded by the cockpit. Charlie "Lite" |
#27
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It's an active myth in non-skydiving circles.
wrote in message oups.com... Interesting... is this an active myth in skydiving circles? That some chutes turn naturally into the wind? |
#28
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BASE (Building, Antenna, Span, and Earth) jumps are done without a reserve
because they would be useless. (Main didn't open? Prepare to die, or get seriously b0rke.) BASE jumpers prefer reserve/emergency chutes for obvious reasons: they don't want to die. wrote in message ups.com... Aren't most BASE jumps done without a reserve? Do BASE jumpers prefer the reserve square or the sport chute (since control into tight LZs is a consideration)? Just trying to get educated since we appear to have a group of folks with useful information. |
#29
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How can a chute weathervane if it is freely drifting with the wind?
This sounds like the old "downwind turn" myth of general aviation fame. I can see that if the chute is descending rapidly through a strong wind velocity gradient, it would tend to orient into or out of the wind (not sure which) due to the height of the chute/risers/chutist stack. If that is the effect being described, how much of a wind gradient is required? Just curious, 66 |
#30
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Thanks for that.
You're welcome. It would seem therefore that the standard conical chute is the only choice for the majority of glider pilots on the grounds that it is likely that we will only ever use it if we have to. If by that you mean that you won't train to use your emergency equipment, then you are correct. Stick with the round. Just don't be surprised if it lands you in the hospital. Remember - those maximum loadings are based on a fit man in his 20's wearing boots with ankle support. For a middle aged man wearing tennis shoes, they really ought to be reduced by 30% or so. Not so the weights on squares - they are, if anything, conservative if you know how to land one. I am firmly of the opinion that people who jump out of perfectly serviceable aeroplanes are .........how can I put it.......... lacking in some way. :-) As opposed to the spectacular good sense exhibited by those who fly airplanes that don't even have engines Glass houses, stones, etc. Michael |
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