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Inspired by the new phoenix fly wingsuit, which is looking at around a 3:1 glide ratio for good flyers i am curious to find out what the glide ratio of my canopy is. I had a look around once before and the closest thing i could find was an approximation of 3:1 for a skydiving canopy (the same as the wingsuit, which is what interested me).

I understand that there are many variables in effect but is there any way to work out an approximate glide ratio of a canopy?

I think a modern canopy would glide at about 2:1 or 3:1.

Theoretically, you should be able to get a better ratio in a wingsuit, since you're "all wing", without the parasitic drag of the lines or the jumper hanging under.


A recording GPS unit with an altimeter is one way to measure it.

It's very easy to work out on a nil wind day:

(1) At X feet note where you are over the ground.
(2) Fly in a straight line until landing, assuming there's nothing in the way. Leave the brakes alone.
(3) If you are a wimp you may flare for landing but realise this will skew the data somewhat.
(4) Measure the distance Y between where you landed and the point you noted earlier (1)
(5) Your glide ratio is Y/X.

For example if you cover 1000 ft horizontally from 1000 ft up then your glide ratio is 1:1. If you cover 1500 ft from 500 ft up your glide ratio is 3:1.

Gus

Forward speed may have a bearing on this discussion..... but I suppose only if you are planning to survive the landing.

For such a calculation I think you'd want to fly your canopy in a way that created the best glide ratio - and that is most likely to be with some rear riser input in order to optimally flatten your glide (exactly how much to use is situation dependent).

You might also want to consider bringing your knees up to your chest and bringing your elbows in, in order to reduce parasitic drag.

Atair claims their Onyx "system" (which is not the skydiving canopy exactly, but which is presumably very similar), has a glide ratio over 4:1.

Source: http://www.extremefly.com/aerospace/onyx/

I know that this data was measured for the Ace/BJ airfoil at one point, in a variety of sizes and loads. I used to have it somewhere on my computer, but I've changed machines twice since then. Let me see if I can dig it up.

 
As a rough guide, I believe a glide ratio of 2.25:1 to 3:1 is reasonable for skydiving canopies at full flight.

Maybe 3:1 for a big easy gliding, high aspect ratio Manta, and 2.25:1 for a small, highly loaded, ground hungry canopy.

This is based on some tests I did years back with anemometers & electronic variometers, with data reduction for density altitude effects, etc. The data won't be perfect but seems consistent. I don't have the time to dig out exact numbers at the moment.

Remember that skydiving canopies are often built nose low for speed, rather than trimmed nose up for efficient glide (more like paragliders). So a skydiving canopy's airfoil usually has potential for a higher glide than it actually achieves.

Also, for small canopies, the pilot size may not change, so the "payload" gives proportionately more drag. A smaller version of the same canopy, with the same pilot, will therefore glide more steeply.

Thanks for all the info guys

BR gives a theoretical glide ratio of 1, 97:1 for the Fox, and 2.05:1 for the Flik, if my memory is good. Actual glide ratio depends on wing loading and PC size ( a 48" PC creates a huge drag...).

Let's say 2:1 for a base canopy, that must be close to reality in most of the cases.