yuri_base 1 #26 June 14, 2008 Quotethe canopy now feels a (20-5) = 15kt wind from the right. The canopy will turn right into this relative wind I think the opposite is true: the canopy doesn't turn into [suddenly changed] relative wind, it turns away from it. If the former was true, the gusts will have self-stabilizing effect on canopy, while I haven't experienced such an effect or saw it once: sideways gusts always push the canopy in the direction of the gust. Everyone experienced this, but here's a good example: http://www.youtube.com/watch?v=m1bFXlwfs9Q at 1:39. The root of this effect is in different dynamic characteristics of the canopy and the pilot: gust coming from the right will quickly push canopy to the left and tilt it due to its low mass, while the pilot stays in place, so the canopy turns left.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
kallend 2,123 #27 June 14, 2008 QuoteQuotethe canopy now feels a (20-5) = 15kt wind from the right. The canopy will turn right into this relative wind I think the opposite is true: the canopy doesn't turn into [suddenly changed] relative wind, it turns away from it. If the former was true, the gusts will have self-stabilizing effect on canopy, while I haven't experienced such an effect or saw it once: sideways gusts always push the canopy in the direction of the gust. Everyone experienced this, but here's a good example: http://www.youtube.com/watch?v=m1bFXlwfs9Q at 1:39. The root of this effect is in different dynamic characteristics of the canopy and the pilot: gust coming from the right will quickly push canopy to the left and tilt it due to its low mass, while the pilot stays in place, so the canopy turns left. Disagree. If canopies turned away from the relative wind, they'd always be turning away from their current direction of flight.... 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
yuri_base 1 #28 June 15, 2008 Quote If canopies turned away from the relative wind, they'd always be turning away from their current direction of flight. It's like saying, "When I'm walking or driving, my feet or my car are turning in the direction the road is coming from." Even in situations when the relative wind is not created by the motion of the canopy itself, the canopy does not have tendency to turn into the wind. For example, when you kite the canopy, you make it turn into the wind by orienting your shoulders and giving inputs to keep heading. Turn 90 and see if the canopy wants to turn into the wind.Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
Martini 0 #29 June 15, 2008 Not a fair analogy, the kayak doesn't "feel" the current but it is affected by the relative wind as the current moves it through the air.Sometimes you eat the bear.............. Quote Share this post Link to post Share on other sites
pilotdave 0 #30 June 15, 2008 Think about how hard it would be to control a canopy if they turned away from gusts. They'd be totally unstable. Forget a gust for the moment and imagine if the canopy temporarily flew slightly sideways through the air. So in other words, it's flying with a little sideslip. What will happen? The sideslip will reduce and the canopy will return to flying straight. In other words, it will turn into the relative wind. What would happen if the opposite was true. A little sideslip would cause the canopy to turn a little more, increasing the sideslip angle. That would make it turn more, and more, and more. It would either turn forever until you apply control to stop it, or it would turn until it's flying backwards. A canopy is stable in all axes. When disturbed, a canopy will return to a stable configuration. If you increase the angle of attack, it will automatically decrease. If you change the bank angle, it will roll out on it's own. And if you yaw to one side, it will recover on it's own to flying straight. Dave Quote Share this post Link to post Share on other sites
kallend 2,123 #31 June 15, 2008 Quote Quote If canopies turned away from the relative wind, they'd always be turning away from their current direction of flight. It's like saying, "When I'm walking or driving, my feet or my car are turning in the direction the road is coming from." Even in situations when the relative wind is not created by the motion of the canopy itself, the canopy does not have tendency to turn into the wind. For example, when you kite the canopy, you make it turn into the wind by orienting your shoulders and giving inputs to keep heading. Turn 90 and see if the canopy wants to turn into the wind. Cars do indeed have a tendency to turn into the direction in which they are moving (where the road goes is not relevant). This is achieved by the caster angle in the steering mechanism. Planes have vertical stabilizers which provide yaw stability. Canopies are also stable in yaw. Which means they turn INTO the relative wind if it is not coming from straight ahead.... 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
morris 0 #32 June 15, 2008 QuoteThink about how hard it would be to control a canopy if they turned away from gusts. But they do, it just far from being that bad that it is a "control-problem". I never thought about yuris explaination that the canopy has less mass than its pilot and thereby being more affected by gusts, creating a bank angle for a moment... interesting - could add something to my own explaination... My explanation is that the profil is way "wider" in the front half. Therefore any gust will affect/push the nose of the canopy way more/stronger than the thin tail, resulting in a turn. A canopy flying north should turn to the east if it´s hit be a gust from the west. As air is almost never completly "quite and equal" a canopy should in perfect conditions (canopy perfect, harness perfect, weight in the harness symetrical,...) always fly downwind sooner or later... Quote Share this post Link to post Share on other sites
pilotdave 0 #33 June 16, 2008 No. It can't even work that way a little. It's either stable or unstable in yaw. Canopies are stable. If you have a small sideslip angle and don't apply any control to correct it, it will not go out of control. It will self correct. That means it turns toward the relative wind. Again, forget gusts of wind because they complicate the situation. Just think about the canopy flying with a little yaw angle compared to the relative wind. Actually, forget canopies for a second and think about a plane. Planes are a bit easier to picture because they have a vertical tail. So picture this... the pilot kicks the right rudder pedal and then brings the pedals back to neutral. The plane yaws right. That causes the relative wind to shift slightly to the left of the nose. What happens next? Does the plane yaw farther to the right, increasing the sideslip angle, or does it yaw to the left, decreasing the sideslip? With a plane, it's pretty obvious that it will yaw back to the left, decreasing the sideslip so it flies straight again. Now imagine a plane flying backwards, so the tail is in the front. The pilot kicks the rudder and then lets go... the tail yaws over to one side. What happens next? Will it self-correct? No, the yaw angle will increase and the plane will spin around until it's flying the other way (backwards, not just flying in the opposite direction). That's the situation you're describing... a plane (canopy) that turns AWAY from the relative wind. Which of those sounds like the canopy you fly? Dave Quote Share this post Link to post Share on other sites
champu 1 #34 June 16, 2008 QuoteEveryone experienced this, but here's a good example: http://www.youtube.com/watch?v=m1bFXlwfs9Q at 1:39. The root of this effect is in different dynamic characteristics of the canopy and the pilot: gust coming from the right will quickly push canopy to the left and tilt it due to its low mass, while the pilot stays in place, so the canopy turns left. Watch your example video again, and pay very close attention just a few moments earlier (at 1:36.) There is a wind gust from the right and you can see the canopy yaw to the right, that is, into the gust. The following roll/pitch to the left looks like toggle input to me. The whole approach was very "toggle-happy" and the lesson to learn there is to do less on final, not that he or she was had by the wind. Either way, glad to see the note that they were okay. Quote Share this post Link to post Share on other sites
pchapman 279 #35 June 16, 2008 QuoteQuote The root of this effect is in different dynamic characteristics of the canopy and the pilot: gust coming from the right will quickly push canopy to the left and tilt it due to its low mass, while the pilot stays in place, so the canopy turns left. [...] There is a wind gust from the right and you can see the canopy yaw to the right, that is, into the gust. The following roll/pitch to the left looks like toggle input to me. So there are different views of what a canopy might to when it meets a gust from the side. I'm guessing that is possible that both behaviours can occur at the same time: a) the canopy yaws into the direction the gust came from (yaw stability), and b) rolls away from the gust due to the different forces / inertia / mass densities / ballistic coefficients / or whatever factors you want to include, of the jumper vs. their canopy. (The behaviour yuri_base described.) Without understanding the exact aerodynamics, it is quite conceivable that a gust could get the canopy swinging away from the gust, and then continue to swing side to side a bit until the motion damps down, but at the same time have it tend to weathervane towards the gust. Quote Share this post Link to post Share on other sites
sapplegate 0 #36 June 18, 2008 Next jump, leave the brakes up after opening, turn with the rear risers to avoid any traffic, and then when clear, point the canopy cross wind, and see what happens. Let us all know what you think! Blue Skies! Quote Share this post Link to post Share on other sites
DougH 270 #37 June 19, 2008 Quote Quote the canopy now feels a (20-5) = 15kt wind from the right. The canopy will turn right into this relative wind I think the opposite is true: the canopy doesn't turn into [suddenly changed] relative wind, it turns away from it. If the former was true, the gusts will have self-stabilizing effect on canopy, while I haven't experienced such an effect or saw it once: sideways gusts always push the canopy in the direction of the gust. Everyone experienced this, but here's a good example: http://www.youtube.com/watch?v=m1bFXlwfs9Q at 1:39. The root of this effect is in different dynamic characteristics of the canopy and the pilot: gust coming from the right will quickly push canopy to the left and tilt it due to its low mass, while the pilot stays in place, so the canopy turns left. The landings in that video are fawking scaaaaary! "The restraining order says you're only allowed to touch me in freefall" =P Quote Share this post Link to post Share on other sites
shropshire 0 #38 June 19, 2008 QuoteNext jump, leave the brakes up after opening, turn with the rear risers to avoid any traffic, and then when clear, point the canopy cross wind, and see what happens. Let us all know what you think! Blue Skies! At deployment height, how you gonna be sure which way the wind is blowing, without a GPS (you're only going to feel relative wind on your face)? (.)Y(.) Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome Quote Share this post Link to post Share on other sites
mnealtx 0 #39 June 19, 2008 Quote Quote Next jump, leave the brakes up after opening, turn with the rear risers to avoid any traffic, and then when clear, point the canopy cross wind, and see what happens. Let us all know what you think! Blue Skies! At deployment height, how you gonna be sure which way the wind is blowing, without a GPS (you're only going to feel relative wind on your face)? Well, I don't know about you crazy Brits, but I usually look at the winds aloft report before I go to the plane... helps with planning out the landing pattern just a little bit... Seriously, though - I don't see how a GPS would help you with winds aloft.Mike I love you, Shannon and Jim. POPS 9708 , SCR 14706 Quote Share this post Link to post Share on other sites
shropshire 0 #40 June 19, 2008 Hi Mike, how's things? I use my GPS (whilst paragliding) to work out the wind speed/direction by looking at my ground track and ground speed whilst flying in different directions. at any given trim setting (Hands up, for example, is easy) the Air Speed of the canopy is always the same... so it's simple maths (actually, I bet that's what the jump ship pilot does too). Reported winds aloft can always be out date too... and not reported too accuratey anyway, but without a compass or GPS you can't be sure that you're pointing exactly into or away from the true Meto Wind. (.)Y(.) Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome Quote Share this post Link to post Share on other sites
mnealtx 0 #41 June 19, 2008 Hi Tony - the comparison between ground track and ground speed is a good point - I hadn't thought of that use. Given the disparity in sink rates between paragliders and parachutes, however, I doubt that skydivers would see as much utility except on a cross-country jump.Mike I love you, Shannon and Jim. POPS 9708 , SCR 14706 Quote Share this post Link to post Share on other sites
kallend 2,123 #42 June 19, 2008 Quote Quote Quote Next jump, leave the brakes up after opening, turn with the rear risers to avoid any traffic, and then when clear, point the canopy cross wind, and see what happens. Let us all know what you think! Blue Skies! At deployment height, how you gonna be sure which way the wind is blowing, without a GPS (you're only going to feel relative wind on your face)? Well, I don't know about you crazy Brits, but I usually look at the winds aloft report before I go to the plane... helps with planning out the landing pattern just a little bit... Seriously, though - I don't see how a GPS would help you with winds aloft. My Garmin 396 shows winds aloft forecasts from the NWS superimposed over the moving map display.... 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
mnealtx 0 #43 June 19, 2008 QuoteMy Garmin 396 shows winds aloft forecasts from the NWS superimposed over the moving map display. Oh, that's sweet!! I'm guessing it's one of the aviation models?Mike I love you, Shannon and Jim. POPS 9708 , SCR 14706 Quote Share this post Link to post Share on other sites
kallend 2,123 #44 June 20, 2008 QuoteQuoteMy Garmin 396 shows winds aloft forecasts from the NWS superimposed over the moving map display. Oh, that's sweet!! I'm guessing it's one of the aviation models? Yup! Has all sorts of cool stuff (lightning strikes, forecasts, current conditions at reporting sites, winds, weather radar, satellite, winds, sigmets, airmets, and XM radio too!)... 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
mnealtx 0 #45 June 20, 2008 QuoteQuoteQuoteMy Garmin 396 shows winds aloft forecasts from the NWS superimposed over the moving map display. Oh, that's sweet!! I'm guessing it's one of the aviation models? Yup! Has all sorts of cool stuff (lightning strikes, forecasts, current conditions at reporting sites, winds, weather radar, satellite, winds, sigmets, airmets, and XM radio too!) Very nice!! I'm envious of all the "bells and whistles" on it! It still seems more feasible for a cross-country jump than "normal" ops - just my opinion, though.Mike I love you, Shannon and Jim. POPS 9708 , SCR 14706 Quote Share this post Link to post Share on other sites
