Now that you know the theory of Glide Ratio from our last lesson, how does that translate for you in the sky? In this episode of Aerodynamics for Dummies, our resident engineer digs a little deeper. We find out what the ratio numbers are for JYRO canopies and why it’s a bit more complicated than it first appears.
JYRO Canopies Glide Ratio
Here are the GR numbers for our JYRO canopies on full drive (within +/-0.3):
- Tandem: 3.0
- Student: 3.2
- Safire 3: 2.8
- Crossfire 3: 2.8
- JFX 2: 2.3
- Leia: 2.1
- Petra: 1.8
As you can see, our high performance canopies have a lower GR on full drive than our more docile range. So why is that? They’re supposed to be more sophisticated, right?! Well, it’s mainly for a couple of reasons.
The trim is designed differently
As opposed to paragliders, our wings are not trimmed to fly at their best Glide Ratio. They are trimmed steeper to provide a nice dive and a wide range of speed. This allows for fast flight and soft flare. Exactly what you want from a skydive parachute.
For instance, if you put your Petra on deep brakes, you can fly next to a Student canopy. If you let Petra out on full drive, you can follow a wingsuit. Take it one step further and in a sustained turn, you could follow someone in freefall!
Canopy size and Pilot Drag also factors into determining the Glide Ratio
All the tests done to record this data, were done with a wing loading (WL) within the recommended range for each canopy. So the most advanced wings have been tested with small sizes (typically a 69 for Petra). While the beginner canopies have been tested on bigger sizes (typically a 139 for a Safire 3). Since the pilot doesn’t scale down, their Drag has a much greater impact on the small canopies than the big ones.
In conclusion, we design more sophisticated wings, not for Glide Ratio, but for a wider speed range. A flat trimmed Petra 139 would certainly out-glide a Safire 3 139, but a Safire 3 69 would be impossible to land!
So what does that actually mean in the real world?
Another aspect to consider is if you are coming from a long spot. There is not much margin to improve the Student Glide Ratio by the way it is designed. However, for your Leia, changing body position (e.g. leaning back in a Mutant Harness) or using rear risers, you can gain a lot and probably get close to 3.0.
Finally, in the real world, Glide ratio depends heavily on winds. Flying upwind will significantly decrease your Glide Ratio. Anyone landed off because you were dropped downwind? That’s why. On the flip-side, you can cover miles and miles with the right tail winds. Unfortunately, it’s not quite as simple as this though. To complicate things further, winds have more impact on slower canopies than fast ones.
For example, say your Safire 3 is flying at an airspeed of 50 km/hr facing winds of similar velocity. It will have a GR of 0.0 and will fly straight down. Whilst your mate is flying their Leia at 100 km/hr in the same winds, will still have a ground speed of 50km/hr, giving it a GR around 1.0. So that’s why when you and your mate exit the plane at the same time, you land off, but they arrive back to the PLA.
Basically, knowing your canopy is good, but you also need to know the winds!
To understand all of this better, we would need to introduce the concept of Polar curves. But that’s for another episode…
Speaking of next episodes, we’ll be talking about how to manipulate Drag to your advantage. Think Cornelia Mihai zooming through the Speed course. Or Jason Sanders powering passed the final markers on a Distance round.