mark 107 #1 August 1, 2007 Actual question from the FAA Rigger Test test bank: Which aspect ratio canopy will generally inflate quicker? A) Canopies with aspect ratios up to 1.9. B) Canopies with aspect ratios 2.0 to 2.2. C) Canopies with aspect ratios 2.3 and up. I have no idea. Anybody got an answer, preferably with a citation from Poynter's? Mark Quote Share this post Link to post Share on other sites
darkwing 4 #2 August 1, 2007 My first response is "It is a dumb-ass question." Too many variables. If you restrict it by saying "same number of cells, same nose design, same square footage, same slider..." I'd say ... I still can't answer it... But I suspect they want the answer to be "C" because they might argue that it will have greater down force on the slider. I anxiously await an authoritative response. -- Jeff My Skydiving History Quote Share this post Link to post Share on other sites
Butters 0 #3 August 1, 2007 Initial impression ... if all other attributes are the same, the canopy with the higher aspect ratio will inflate quicker because both canopies will have the same sq. ft. of bottom skin for inflation but the canopy with the higher aspect ratio will have more sq. ft. of nose for inflation. Does this make sense? Edit: However, I have read that the end cells on canopies with higher aspect ratios inflate slower. I guess I have some more reading to do."That looks dangerous." Leopold Stotch Quote Share this post Link to post Share on other sites
dragon2 0 #4 August 1, 2007 The quickest opening canopies I've jumped are crw-type canopies, which are all 7cells. Accuracy chutes also inflate quickly. Also almost all reserves are 7cells and open quick... Same for BASE chutes. Now most of these canopies are older designs so them opening quick may have something to do with that. Sorry no Poynter's ciel bleu, Saskia Quote Share this post Link to post Share on other sites
tdog 0 #5 August 1, 2007 "C" Poynter Volume 2 - 8.30 (I don't have P2 here to verify, but I have the answers with support for the answers on a study guide) Quote Share this post Link to post Share on other sites
mark 107 #6 August 1, 2007 Quote"C" Poynter Volume 2 - 8.30 (I don't have P2 here to verify, but I have the answers with support for the answers on a study guide) The discussion of aspect ratio in 8.30 (beginning on page 330) centers around rigidity and flight characteristics. No direct mention of opening speed. Is there something else in 8.30 that would answer more directly? Mark Quote Share this post Link to post Share on other sites
tdog 0 #7 August 1, 2007 QuoteQuote"C" Poynter Volume 2 - 8.30 (I don't have P2 here to verify, but I have the answers with support for the answers on a study guide) The discussion of aspect ratio in 8.30 (beginning on page 330) centers around rigidity and flight characteristics. No direct mention of opening speed. Is there something else in 8.30 that would answer more directly? Mark Good question. The sheet I have is sometimes incomplete and has assumptions... If I was going to take the test now, I don't know what I would answer... Look at the Spectre (a 7 cell) known for soft openings. Look at a PD reserve known for quick openings. Look at a BASE canopy, known for very fast openings. They are all about the same aspect ratio (correct me if I am wrong, I need to run to work otherwise I would download the specs on a PDR and Spectre)... I believe canopy design (nose angles, etc) will alter opening speed quite a bit. So if I was going to answer based upon known facts in my personal experience, would I choose the soft opening spectre, or the hard opening BASE canopy, as my basis???? I hate the question myself, because like a lot of them in the test bank, the answer I think is "It depends." Quote Share this post Link to post Share on other sites
gdmusumeci 0 #8 August 1, 2007 Quote Look at the Spectre (a 7 cell) known for soft openings. Look at a PD reserve known for quick openings. Look at a BASE canopy, known for very fast openings. They are all about the same aspect ratio (correct me if I am wrong, I need to run to work otherwise I would download the specs on a PDR and Spectre)... They're all very close in terms of aspect ratio -- PD Reserve 2.1, Spectre 2.14, Lightning 2.2. Quote Share this post Link to post Share on other sites
seal_S49 0 #9 August 2, 2007 Which aspect ratio canopy will generally inflate quicker?*** I'm sure the FAA will designate an answer that is correct, but in the field there are many variables. I say that the single biggest influence on opening speed is the configuration of the nose, because this will regulate the volume of airflow entering. If you disregard all factors (nose configuration, slider, fabric permeability, crossports, eliptical taper, suspension-line trim, control line length) and consider only aspect ratio, I say that the higher ratio will (theoretically) open faster because it will have less internal volume per sq. ft. due to the vertical thickness (camber) of the inflated wing being smaller. Higher aspect-ratio 9-cells typically have thinner ribs than lower aspect-ratio 7-cells. This just in: PPM V#II pg. 331 "Increasing the aspect ratio of a ram-air canopy tends to make it open quicker and harder." Quote Share this post Link to post Share on other sites
riggerrob 598 #10 August 2, 2007 QuoteThe quickest opening canopies I've jumped are crw-type canopies, which are all 7cells. Accuracy chutes also inflate quickly. Also almost all reserves are 7cells and open quick... Same for BASE chutes. Now most of these canopies are older designs so them opening quick may have something to do with that. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> That is because jumpers demanded quick-opening canopies back then. It was routine for classic accuracy competitors to do hop-and-pops from 2,000 and expect to be open NOW! Quote Share this post Link to post Share on other sites mark 107 #11 August 2, 2007 Quote This just in: Thanks! I don't know how many times I read that section without actually reading it.Mark Quote Share this post Link to post Share on other sites Butters 0 #12 August 2, 2007 QuotePPM V#II pg. 331 "Increasing the aspect ratio of a ram-air canopy tends to make it open quicker and harder." Why are reserves ~2.1 (why not larger for quicker inflation)? How does higher aspect ratio affect flight characteristics (stall, recovery arc, landing, etc...)? Does increasing the aspect ratio of a canopy decrease the opening consistency thus resulting in a higher chance of a malfunction?"That looks dangerous." Leopold Stotch Quote Share this post Link to post Share on other sites seal_S49 0 #13 August 2, 2007 QuoteQuotePPM V#II pg. 331 "Increasing the aspect ratio of a ram-air canopy tends to make it open quicker and harder." Those aren't my words, but I agree that there is a fundamental reason for this to be true when all other factors are similar. However, I'm not going to defend someone else's hypothesis. QuoteWhy are reserves ~2.1 (why not larger for quicker inflation)? RMFP! There are many factors that affect opening speed, thus a low aspect-ratio canopy can be made to open very quickly. Ever seen a cut-out slider on a reserve canopy or a mesh base slider? Quote How does higher aspect ratio affect flight characteristics (stall, recovery arc, landing, etc...)? Do your own research or start your own thread. Quote Does increasing the aspect ratio of a canopy decrease the opening consistency thus resulting in a higher chance of a malfunction? Now I think you're onto something. Hint: look at paraglider canopies & see if you can guess why they're not suitable for skydiving. Quote Share this post Link to post Share on other sites darkwing 4 #14 August 2, 2007 QuoteWhy are reserves ~2.1 (why not larger for quicker inflation)? How does higher aspect ratio affect flight characteristics (stall, recovery arc, landing, etc...)? Does increasing the aspect ratio of a canopy decrease the opening consistency thus resulting in a higher chance of a malfunction? Higher aspect ratio in general increases the malfunction rate... -- Jeff My Skydiving History Quote Share this post Link to post Share on other sites Butters 0 #15 August 2, 2007 QuoteQuoteWhy are reserves ~2.1 (why not larger for quicker inflation)? RMFP! There are many factors that affect opening speed, thus a low aspect-ratio canopy can be made to open very quickly. Ever seen a cut-out slider on a reserve canopy or a mesh base slider? I understand that there are many factors. That is why I am asking. Why not a smaller or larger aspect ratio with nose modifications, slider modifications, etc... In other words, canopy manufactures must have weighed out the pros and the cons of each combination and then determined the combination that provided the maximum amount of pros (with each pro being weighted accordingly) with the minimum amount of cons (with each con being weighted accordingly). I would be glad to do my own research ... can you give me a good place to start? Thanks."That looks dangerous." Leopold Stotch Quote Share this post Link to post Share on other sites waltappel 1 #16 August 2, 2007 QuoteActual question from the FAA Rigger Test test bank: Which aspect ratio canopy will generally inflate quicker? A) Canopies with aspect ratios up to 1.9. B) Canopies with aspect ratios 2.0 to 2.2. C) Canopies with aspect ratios 2.3 and up. I have no idea. Anybody got an answer, preferably with a citation from Poynter's? Mark Let's assume some factors are equal (I know they never are): * sq. ft. * ability of nose to grab air * "thickness" of the canopy * number of cells * sliders are proportionate to the canopies Per the above assumptions, the volume of each cell should be the same but the cells on the higher-aspect-ratio canopies will be wider and their lengths will be shorter. Seems to me like the larger cell openings and the shorter chord would mean the canopy with the highest aspect ratio would open the fastest. Walt Quote Share this post Link to post Share on other sites seal_S49 0 #17 August 2, 2007 Quote canopy manufactures must have weighed out the pros and the cons*** You can bet that they have, and the number one design priority for a skydiving canopy is that it must inflate at terminal in a reliable (enough) manner. A wing design w/ better flight characteristics is no good if it doesn't meet this priority. Reserve and base canopies will be even more of a performance compromise to gain as much reliability as possible. After a couple of decades of tremendous progress, the industry has proven it's ability to design favorable opening characteristics (fast or slow) into a wide variety of wing profiles. So far, the lower aspect-ratio 7-cell canopy seems to be the best design compromise for the unique requirements of a reserve. I would be glad to do my own research ... can you give me a good place to start? Thanks*** I'd suggest searching the subject of aerodynamics as related to wing design. Airplanes, gliders, and ram-air parachutes are all subject to the same laws of physics. Once you understand terms like: lift, drag, span, chord, camber, aspect ratio, glide ratio, angle of attack, stall, wingtip vortices, etc., you'll notice the differences in canopy designs and understand how mfrs produce different products, each with its own specific flight envelope. The sport of paragliding seems to offer more tutorial info on this subject. Consumers of these canopies (wings) seem to demand more info and their mfrs seem to provide more. This is a huge topic with many elements, each of which could generate a lengthy thread. Quote Share this post Link to post Share on other sites Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Reply to this topic... × Pasted as rich text. 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mark 107 #11 August 2, 2007 Quote This just in: Thanks! I don't know how many times I read that section without actually reading it.Mark Quote Share this post Link to post Share on other sites
Butters 0 #12 August 2, 2007 QuotePPM V#II pg. 331 "Increasing the aspect ratio of a ram-air canopy tends to make it open quicker and harder." Why are reserves ~2.1 (why not larger for quicker inflation)? How does higher aspect ratio affect flight characteristics (stall, recovery arc, landing, etc...)? Does increasing the aspect ratio of a canopy decrease the opening consistency thus resulting in a higher chance of a malfunction?"That looks dangerous." Leopold Stotch Quote Share this post Link to post Share on other sites
seal_S49 0 #13 August 2, 2007 QuoteQuotePPM V#II pg. 331 "Increasing the aspect ratio of a ram-air canopy tends to make it open quicker and harder." Those aren't my words, but I agree that there is a fundamental reason for this to be true when all other factors are similar. However, I'm not going to defend someone else's hypothesis. QuoteWhy are reserves ~2.1 (why not larger for quicker inflation)? RMFP! There are many factors that affect opening speed, thus a low aspect-ratio canopy can be made to open very quickly. Ever seen a cut-out slider on a reserve canopy or a mesh base slider? Quote How does higher aspect ratio affect flight characteristics (stall, recovery arc, landing, etc...)? Do your own research or start your own thread. Quote Does increasing the aspect ratio of a canopy decrease the opening consistency thus resulting in a higher chance of a malfunction? Now I think you're onto something. Hint: look at paraglider canopies & see if you can guess why they're not suitable for skydiving. Quote Share this post Link to post Share on other sites
darkwing 4 #14 August 2, 2007 QuoteWhy are reserves ~2.1 (why not larger for quicker inflation)? How does higher aspect ratio affect flight characteristics (stall, recovery arc, landing, etc...)? Does increasing the aspect ratio of a canopy decrease the opening consistency thus resulting in a higher chance of a malfunction? Higher aspect ratio in general increases the malfunction rate... -- Jeff My Skydiving History Quote Share this post Link to post Share on other sites
Butters 0 #15 August 2, 2007 QuoteQuoteWhy are reserves ~2.1 (why not larger for quicker inflation)? RMFP! There are many factors that affect opening speed, thus a low aspect-ratio canopy can be made to open very quickly. Ever seen a cut-out slider on a reserve canopy or a mesh base slider? I understand that there are many factors. That is why I am asking. Why not a smaller or larger aspect ratio with nose modifications, slider modifications, etc... In other words, canopy manufactures must have weighed out the pros and the cons of each combination and then determined the combination that provided the maximum amount of pros (with each pro being weighted accordingly) with the minimum amount of cons (with each con being weighted accordingly). I would be glad to do my own research ... can you give me a good place to start? Thanks."That looks dangerous." Leopold Stotch Quote Share this post Link to post Share on other sites
waltappel 1 #16 August 2, 2007 QuoteActual question from the FAA Rigger Test test bank: Which aspect ratio canopy will generally inflate quicker? A) Canopies with aspect ratios up to 1.9. B) Canopies with aspect ratios 2.0 to 2.2. C) Canopies with aspect ratios 2.3 and up. I have no idea. Anybody got an answer, preferably with a citation from Poynter's? Mark Let's assume some factors are equal (I know they never are): * sq. ft. * ability of nose to grab air * "thickness" of the canopy * number of cells * sliders are proportionate to the canopies Per the above assumptions, the volume of each cell should be the same but the cells on the higher-aspect-ratio canopies will be wider and their lengths will be shorter. Seems to me like the larger cell openings and the shorter chord would mean the canopy with the highest aspect ratio would open the fastest. Walt Quote Share this post Link to post Share on other sites
seal_S49 0 #17 August 2, 2007 Quote canopy manufactures must have weighed out the pros and the cons*** You can bet that they have, and the number one design priority for a skydiving canopy is that it must inflate at terminal in a reliable (enough) manner. A wing design w/ better flight characteristics is no good if it doesn't meet this priority. Reserve and base canopies will be even more of a performance compromise to gain as much reliability as possible. After a couple of decades of tremendous progress, the industry has proven it's ability to design favorable opening characteristics (fast or slow) into a wide variety of wing profiles. So far, the lower aspect-ratio 7-cell canopy seems to be the best design compromise for the unique requirements of a reserve. I would be glad to do my own research ... can you give me a good place to start? Thanks*** I'd suggest searching the subject of aerodynamics as related to wing design. Airplanes, gliders, and ram-air parachutes are all subject to the same laws of physics. Once you understand terms like: lift, drag, span, chord, camber, aspect ratio, glide ratio, angle of attack, stall, wingtip vortices, etc., you'll notice the differences in canopy designs and understand how mfrs produce different products, each with its own specific flight envelope. The sport of paragliding seems to offer more tutorial info on this subject. Consumers of these canopies (wings) seem to demand more info and their mfrs seem to provide more. This is a huge topic with many elements, each of which could generate a lengthy thread. Quote Share this post Link to post Share on other sites
