larsrulz 0 #51 July 9, 2004 Quade: The page there does show that lift to drag ratio is independent of velocity. I agree with that...I haven't said L/D is dependent on velocity. This is one of the cases where glide slope and L/D are not equal; if you do not fly at best glide speed, then you do not fly at best glide slope. Bill: I didn't say the flight controls of a glider and a parachute are the same (plus I've only flown a TG-4, so I'm not talking about HP gliders). Merely that they fly similarly since they both...well glide under the power of gravity. As for the issues of dynamic stability...that's because a parachute is as flying wing while a glider is an unpowered airplane, so longitudinal stability to two TOTALLY different beasts. The fact is still that they both produce lift and are unpowered...that's all I was getting at really. I don't know how paragliders work for trim and such, so...well, I just don't know. You talk about pitch stability from design, but this is exactly what goes into the glide slope of a parachute. The pitch stability is influenced by the velocity, much as explained above with the whole canopy dive/plane thing. I got a strong urge to fly, but I got no where to fly to. -PF Quote Share this post Link to post Share on other sites
quade 3 #52 July 9, 2004 Quote This is one of the cases where glide slope and L/D are not equal; if you do not fly at best glide speed, then you do not fly at best glide slope. I wanted you to read about weight v. glide ratio. Weight does -not- change the glide ratio. While gliding (no wind, no thermals, straight & level decent, stabilized conditions) you are traveling down a hypotenus called the glide slope. This does not change with the weight of the aircraft. ONLY the speed down the glide slope changes. A lighter aircraft can fly slower because its wings do not have to create as much lift and a heavier aircraft will have to fly faster because its wings have to create more lift -- but the glide ratio -- the glide slope -- the hypotenus created by the forward and downward motion remains the same. This is a fact not up for debate. It's not a matter of opinion. It's not something that changes dependent on what type of wing you happen to be flying.quade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
kallend 1,635 #53 July 12, 2004 QuoteQuoteNot exactly, an aircraft wing works because the path over the wing is longer than that under the wing. The means that a little block'o'air going over the wing must go quicker than its buddy who goes under. The block'o'air going quicker has a lower pressure which causes that block'o'air to want to displace the higher pressure buddy above the wing. This causes the fluid (air) around the wing to lift the wing up, which is basically how lift works. For that to be 100% correct, then the velocity of the fluid moving over the wing should be able to be accurately predicted using Bernoulli's formula. However, in reality, the velocity of fluid over a lifting wing is much higher than what Bernoulli's formula would spedify. The explanation for that is Newton's law on action/reaction forces which deals with deflection of air, in effect push from the underside, rather than being sucked upward by lower pressure as Bernoulli suggests. The implementation of Newton's law has a great deal to do with angle of attack. In fact, changing angle of attack alone changes lift which in effect, negates the Bernoulli formula as being the sole contributor to lift. It's actually a little of both. Bernoulli did not have any formula relating to wings. Bernoulli's equation in fluid dynamics relates to pressure/velocity relations along a streamline, and is just a restatement of conservation of mechanical energy. For the nerds, it can also be derived from Navier-Stokes equations. So as long as Newton's laws hold, and mechanical energy is conserved, Bernoulli's equation works for streamline flow around a wing. However, the velocities can NOT be predicted just by measuring the length of the flow path over the top and bottom surfaces.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 1,635 #54 July 12, 2004 QuoteRead my original reply: "A parachute does not work the same way in which a aircraft wing works. I'm still personally uncertain about what force causes a (square) parachute to "fly," but (I believe) the majority of the force causing flight is air deflection as opposed to pressure differential." So I do agree with you. The name given to the force exerted by a fluid on a surface is "PRESSURE". You cannot have air deflection without a pressure differential.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Scrumpot 1 #55 July 15, 2004 QuoteI do normally come in a bit high, but I'm used to just doing S turns to eat up some altitude. But I also tend to hug the landing area. See now, this concerns me. ...Did this send up any "alarm bells" for any one else? 1st off Sheena, I am not flaming you, so don't get me wrong here. This is precisely why we put this sort of stuff up here, and then talk about it, so we all can learn. However, unless you are ALWAYS last down, and you KNOW you are last down (not so simple of a concept as you might think if for instance you travel to a new DZ, and there are either bigger aircraft doing multiple passes, or even multiple aircraft with staggered jump runs), "Doing S-Turns 'hugging' the landing area" can be a BAD idea! This is precisely (or at least possibly one component of) why GP put this in here. Clearly, you are doing exactly what has been taught to you ...and you feel it is "right", and therefore of no concern. I'm with GP, I think the teaching of "setting up your entering the pattern at 1k" needs to be rethought. Great post! ...But man, did this thread get "hijacked"! Can we maybe please bring it back to what it was meant to illicit, which was (as seems to me) to be a discussion regarding the efficacy of teaching students fixed altitude references (etc.) for their landing patterns & their potential affects, problems &/or concerns? -Grantcoitus non circum - Moab Stone Quote Share this post Link to post Share on other sites
Icon134 0 #56 July 16, 2004 QuoteQuoteI do normally come in a bit high, but I'm used to just doing S turns to eat up some altitude. But I also tend to hug the landing area. See now, this concerns me. ...Did this send up any "alarm bells" for any one else? 1st off Sheena, I am not flaming you, so don't get me wrong here. This is precisely why we put this sort of stuff up here, and then talk about it, so we all can learn. However, unless you are ALWAYS last down, and you KNOW you are last down (not so simple of a concept as you might think if for instance you travel to a new DZ, and there are either bigger aircraft doing multiple passes, or even multiple aircraft with staggered jump runs), "Doing S-Turns 'hugging' the landing area" can be a BAD idea! This is precisely (or at least possibly one component of) why GP put this in here. Clearly, you are doing exactly what has been taught to you ...and you feel it is "right", and therefore of no concern. I'm with GP, I think the teaching of "setting up your entering the pattern at 1k" needs to be rethought. Great post! ...But man, did this thread get "hijacked"! Can we maybe please bring it back to what it was meant to illicit, which was (as seems to me) to be a discussion regarding the efficacy of teaching students fixed altitude references (etc.) for their landing patterns & their potential affects, problems &/or concerns? -Grant Thanks Grant, I do some of the bleeding off a little altitude that Sheena is talking about sometimes (I try to avoid it... and try to be canopy aware head on a swivel looking for other people in the air..) but what I was told to do was if I find my Base Leg (the cross wind leg) is going to put me too high then go a bit wider or if I'm low then cut it a bit tighter to the Landing area... One of my AFF Jumpmasters instructed me that I should never fly my canopy over something I didn't want to land on... (I'm assuming that he meant under a particular altitude...) Are there methods to bleed off altitude w/o S-turning on approach... or would the best practice to do your best to be canopy aware and burn off altitude such that I don't find myself trying to land w/a student on approach... like I did on saturday... (I don't believe I interfered with his approach and he came down after me... but I had some minor conserns in the air and on my approach... ScottLivin' on the Edge... sleeping with my rigger's wife... Quote Share this post Link to post Share on other sites
DrewEckhardt 0 #57 July 16, 2004 Quote Are there methods to bleed off altitude w/o S-turning on approach... You can fly in deep brakes especially when there's some wind. Obviously you want to have enough forward speed to get a decent flare on landing and will want to release the brakes before you get too low so the surge doesn't occur too low. Before you get to final approach you can do that or 1. Fly a bigger pattern. If things aren't good on your down-wind leg you can fly away from where you'll be on final approach. 2. Loose more altitude in turns. Quote or would the best practice to do your best to be canopy aware and burn off altitude such that I don't find myself trying to land w/a student on approach... Opening at a reasonable altitude gives you enough time to gain (brakes) or loose (spiral) altitude relative to other canopies so you aren't landing at the same time. Watch what the the other jumpers are doing and pick the course of action most likely to give separation (if they're being aggressive and not under a wing that's too much bigger let them land first. if they're making gentle turns have whoever's sinking faster land first). Wing loading and your place in the exit order will influence which works better, although modern canopies do have a _huge_ range - you can slow a 105 samurai down to the same descent rate and forward speed you'd have under a 170 spectre. Quote Share this post Link to post Share on other sites
quade 3 #58 July 16, 2004 Another fairly simple way to -dissipate- energy if a person is going long is to pull down on both front risers. The glide ratio will steepen and airspeed will also increase, but the associated increase in parasitic drag will take energy out of the system and will land shorter than if the canopy had been flown in its "normal" configuration. This works in both wind and no wind situations. Obviously, a person would want to transition back to "normal" flight before touching down. quade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
Scrumpot 1 #59 July 19, 2004 QuoteAnother fairly simple way to -dissipate- energy if a person is going long is to pull down on both front risers. Isn't precisely this method now incorporated in fact, as a part of the "new" ISP? I had thought it was. I would prefer to see this practiced, than taking your "final (crosswind) leg" longer/wider! ...Crossing the "center line" on crosswind IMHO is ALSO a bad habit to be getting into! -Grantcoitus non circum - Moab Stone Quote Share this post Link to post Share on other sites
pilotdave 0 #60 July 20, 2004 If that stuff is part of the ISP, maybe I should go do AFF again. I was never taught anything about touching risers in AFF. Actually I'm taking a canopy course next month. Maybe I'll learn a thing or two that students are being taught now! Dave Quote Share this post Link to post Share on other sites
kelpdiver 2 #61 July 20, 2004 QuoteIf that stuff is part of the ISP, maybe I should go do AFF again. I was never taught anything about touching risers in AFF. Actually I'm taking a canopy course next month. Maybe I'll learn a thing or two that students are being taught now! Dave That would depend on the place, I guess. I didn't get anything about canopy work during my [numerous] AFF jumps. Came up while going through the A checklist since there are many requirements there. So sometime soon I'll join you at that canopy class. Quote Share this post Link to post Share on other sites
juanesky 0 #62 July 24, 2004 The 2004 Sims AFF categories (A-H) jumps is very detailed in what the student should learn. In it includes many Canopy maneuvers."According to some of the conservatives here, it sounds like it's fine to beat your wide - as long as she had it coming." -Billvon Quote Share this post Link to post Share on other sites
