Low Wing-Loading on Small Gliders

[krista]

As many of you have heard, we had a wonderful day at Edith's Gap on Saturday, with several pilots flying 25-81km cross-country. I, however, was not one of them. Again, another safety lesson from a [flight] dummy.

My flight was not good based upon a number of poor decisions, including the decision to launch. I have done some significant self-reflection and research since Saturday, which I believe may be beneficial to the group---particularly smaller pilots on smaller wings. Here are the issues. (SMALL PILOTS: If you don't want to read the whoe thing, please skip to the link at point #5. PLEASE READ IT.)

1. Decision to Fly: I assessed the condition similar to another EG flight I had, in which I landed at the barn, due to a strong south cross. The clouds overhead clearly indicated S-SSW. I made the decision not to fly. Then I changed it after having seen Laszlo and Austin launch and fly without issue. Should have revalidated the decision based on more data (including the post-flight analysis and research below.)

2. Flight: I launched and was immediately lifted into the sky; it wasn't so bad and was smoother than other spring day flights. I had some issues in which I would get blown backwards very briefly, then I would recover. The air seemed slippery, which I chocked up to somewhat strong spring conditions. The air was fine as I thermaled up to 3,000 feet, keeping the LZ within reach. Then the wind shifted SW, and my thermal died. I went to Kennedy knob thinking it would be a good trigger with the rocks in the sun and facing the wind. I was greeted by 6.4m/s sink. I never found the thermal. I remained in 6m/s sink all the way to the ground using half speed bar. Max speed: 69kph. I had two LZ options, having gotten out of position to reach the main LZ. First, an LZ right off of Camp Roosevelt / Fort Valley road and in the shade. Second, an LZ in the sun with about three fields and a house, but closer to the knob. I chose the one in the sun thinking it was the highest chance of catching a thermal. Instead, I caught rotor, more 6m/s sink, and now 20-25mph winds. What I didn't realize from above, is also the hill next to it, which created a micro-venture affect. As I got into position, I was getting blown backwards into the wind, now seeing power lines cutting through the big field. Sigh. I set up of the next field back and was going backwards even faster towards trees; I pushed full speed bar and was still going backwards. Then I had a full collapse over the trees with insufficient altitude to deploy my reserve. Thankfully, I recovered quickly and with some extremely active piloting, maneuvered my way to a patch of greenery atop the small, venturi-creating hill, over my shoulder. I regained forward speed about 15 feet above the ground. Pilot and glider safe.

3. Post-Flight Reaction: Stupid, stupid, Krista. I'm lucky to be walking. Stupid, really stinking stupid, Krista. I asked my friend Jon, who also has my glider in size S, if he had issues with getting blown backwards. He sent me the link below at #5 (SMALL PILOTS: READ IT).

4. Post-Flight Research: My wing-loading is 3.5kg per square meter of glider. Three, point, stinking, five. Here's the issue, which is more eloquently explained in the article below. I'm not "light" on my wing, according to the manufacturer's weight range, but I'm LIGHT on my wing. I'm at 83kg (suited up with some water) on a 60-90kg glider with an flat area of 23.5m2 (about 3m2 too big, or 12kg too light).

5. SMALL PILOTS---READ THIS (The whole thing please): http://laurenmartins.blogspot.co.uk/201 ... ml?spref=b. An excerpt: "...most paraglider manufactures do not make the XXS, XS or S gliders small enough, instead of spending some time in these smaller wings, to get them to certification with optimum size ex 19sqm flat for 80kg all up pilot , 17sqm flat for a 70kg all up, they make them 3 to 6 meters larger than what would be ideal, because bigger gliders with low wingload are slower and get certification easily without them having to spend time on them. If your flight weight is from 60-80kg you may not surprisingly find out that your wing may be over 22sqm flat in same cases." As she lays out, "[the] minimum wingload for ladies or light boys fly modern paragliders depending of the (glider class, arc and other parameters) is no less than 4kg/sqm flat."

6. Post-Flight Reflection: I am going to come up with additional ballast options until I can find a new wing with a better wing-loading range. I must shy away from stronger wind days, and must respect that just because every other pilot is doing fine (including fellow EN-Bs) in the conditions, that doesn't mean that I will. When I was looking for a new wing, weight and size were part of it. Over the course of my search, I began weighting other glider characteristics over size (ultimately choosing a S over an XS given safety certifications). This cannot be done for XXS, XS, and S gliders. Yes, indeed, size does matter.

[Matthew]

Wow! Very interesting article.

Hey Matt Ingram, what is your glider size and wing loading????

Matthew

[mingram]

I agree... very interesting. I'm flying a higher aspect ratio EN-C glider which affects the actual wing loading. I'm not sure exactly how that's accounted for, but from that article they split wings out by category so we should compare my loading with Krista's. We need to compare with other higher performance EN-B gliders like Austin's Hook 3.

I'm flying a UP Summit XC2 SM (72-94kg recommended weight range)
84.5 kg all up
24.3 m2 flat area
= 3.47 kg/m2 wing loading

I flew in Dunlap, CA and had a really hard time flying into the wind compared to other pilots (and every flight started up wind). I was mostly flying against EN-D wings, but the ones I talked to said they were flying over the recommended weight range and said I needed to ballast up. Adding an extra gallon of water helped, but it was really hard to carry in my harness. On the East coast I don't typically have an issue because I chose not to fly on really windy days and because we get plenty of low/no wind days during the summer. Those are my favorite. I don't like getting blown around. If I were to fly on the west coast I would get a smaller glider. I'd also probably even go higher aspect ratio.

Krista, maybe this is more reason to start looking at higher aspect ratio wings. I know you have the skills/touch - you just need to find one the right size. Since we're the same weight all up you should try mine.

[Matthew]

... Krista, maybe this is more reason to start looking at higher aspect ratio wings....

****

Or maybe pasta, lots of pasta.

And donuts!

Matthew

[AustinKasserman]

I fly a Medium (25m2) Niviuk Hook 2. The recommended weight range is 80-100kg and I fly at roughly 89-94kg depending on winter/summer.

After Krista launched we were both on the ridge for 10-15 minutes together. I do remember getting nearly parked a couple times while facing the South cross, and I can imagine Krista, being even lighter would have experienced the same.

The only incident I've ever had in my brief 1.5 years as a PG pilot was getting blown back behind Woodstock during one of my first flights in VA. I wasn't injured and my gear wasn't damaged so I was lucky in that regard. I've been extra cautious since then to stay in front and watch my ground speed. Given that I've never had a major issue controlling my glider for collapses/spins/stalls (fingers crossed), I've found that my biggest safety concerns to date are all about penetration - getting blown over, getting parked and making glide to the LZ. I like to call my speed bar my "speed down bar" because the times when I have been parked and used bar, my forward speed increased only marginally while my downward speed seemed to increase quite a lot. For these reasons, I think in a lot of ways a higher performance glider may actually be safer in many situations. Take that with a grain of salt because I've only ever flown an EN-B. I wish there was an easy way to test fly a bunch of wings without planning a big vacation around it...

[theflyingdude]

Krista, great write-up! Glad you didn't splat!

Thanks for posting it here!!!

JR

[Dan T]

I think that all other factors being equal, such as equivalent wing loading, a smaller pilot is still going to get pushed around more. He or she is carrying less inertia into the active (and therefore accelerating) air. A smaller wing is only part of the solution. The other part is fly in lighter conditions. This applies to hang glider pilots as well.

Dan