FreeFlight Advice: Tips for climbing in thermals
Posted on FreeFlightAdvice.com June 3, 2014
Q: Hey, I am hoping to get your help and expert opinion on something. I’ve sent you a link to a four minute clip of me flying last weekend. I pinned off from the tug at about 2500 feet agl and I was able to climb just about 1000 feet. I did this pretty much by boating around in the lift with a few turns. I am a fairly new hang three, and still working on staying in lift. I wonder if you can take a look at this video, and tell me where I should have been turning more, or banking more, flying slower or faster, etc. in other words, just a critique of what I’m doing and not doing here. The video ends at the point where you can hear the sink alarm going off and the rest of the flight was all sink. It was also fairly windy aloft that day and I didn’t want to get blown too far downwind. Anyway, thanks so much for your help.
A: First and foremost, what an awesome day! It looks like the lift was EVERYWHERE!!!
Before getting into some specific things I see in the video, let’s talk about some general best practices for climbing in lift. One of the things you asked about was flying slower or faster… in lift, you can’t fly slow enough! And by “you can’t”, I mean that our aircraft is incapable. In a perfect world we could just stop and hover in lift… then we’d never have to turn; it’d be so easy! But alas, our wings need airspeed to create lift and keep us flying. When you think really think about that, though… it kind of tells you how fast to fly- as slow as possible- in lift. We should also go deeper into “as slow as possible”… There are two important airspeeds you should learn for thermalling: First is the stall speed of the glider, which can be pretty elusive. Because of the twist in our wings, the root of the wing at the keel is at a higher angle of attack than the tips, and therefore stalls before the tips. Seeing that you are flying a Wills Wing, I know that your glider is equipped with stall tufts (pieces of yarn stuck to the top surface). These are strategically placed to identify the first onset of stall, which they’ll signify by first point out sideways toward the tips, before pointing forward when you’ve actually stalled. It’s a great idea to take a tow up in smooth conditions and practice flying as slow as you can and watch those tufts. Try to get a FEEL for where stall is through the feedback the glider gives you. You’ll get your best sink rate (IE climb rate) flying as slow as possible but BEFORE any of the wing is stalled. Note that in a turn wing loading increases because you’re pulling G’s, and that raises your stall speed… which is why I recommended focusing on the FEEL rather than measuring for a specific airspeed. The other important speed to learn is minimum controllable airspeed. Flying slow gets you sinking as slow as possible through the air you’re in, but that’s not of much use if you fly out of the thermal! Most gliders are very hard to steer at the low airspeed where we get our absolute best sink rate… so a compromise must be made. First priority must be maintaining control of the glider- staying in the thermal, putting the glider where you want it to go, and of course not hitting the ground or other gliders around you.
Another general best practice you asked about is bank angle. You had asked if you should be banking steeper or less steep, and when. The simple answer is yes! The complicated answer is when to flatten out and when to tighten up. Learning that takes many, many years… and it’s one of the key things that makes a sky-god thermal pilot so damn good! In general terms, we know that our glider is most efficient flying straight and level, and our sink rate increases (or climb rate decreases) the more we bank. So I aim to turn as flat as possible (flying slow helps a lot with that!), but as steep as necessary. Necessary meaning my first priority is staying in the lift, second priority is flying as efficiently as possible. You might notice this is very similar to flying slowly. The two are related because the diameter of a 360 is determined by speed AND bank… changing either one will effect the diameter. Changing BOTH can make a huge different in how tight you’re turning. I’d say that most pilots turn a little too wide and would do better if they practiced efficiently turning a little tighter.
Getting a little more specific means we need to identify some traits about the thermal. As a new pilot, you’re probably going to have to fly in-and-out of the thermal a few times to identify it’s traits. More experienced pilots can look at weather traits and dial in what to expect (high or low pressure for example), as well as “feel” what a thermal is like as soon as they enter (based on the thousands of other thermals they’ve flown in over the years). Unfortunately there’s no good shortcut to experience, so for now be content with flying through the thermal a few times and learn what you can as quickly as you can. Flying through the thermal, we want to identify two main things- how wide is it, and how strong a climb is it? As simple as that sounds, it can be complicated because thermals usually aren’t uniform… there might be a wide part with a slow climb and core- which isn’t always in the center- where the climb is faster. Knowing how wide the thermal is tells us how much we need to bank; your goal is to keep the vario beeping during your entire 360. If it doesn’t beep during one part of your 360, you probably found the edge of the thermal… so as you enter the thermal again, flatten out for just a moment to move yourself a little better centered, and then bank back into that 360. Rinse and repeat.
It get’s a bit trickier still when you find a ‘core’, because you need to ask yourself if the core is strong enough to make up for the increased inefficiency of turing steeper to stay in just that portion of the thermal. Most times I think it is, but that’s just me. If nothing else, it’s good practice flying slow and turning tight- a skill just about everyone could benefit from improving no matter how good they already are. I am sorry to report that, once again, being able to evaluate if a core is strong enough to offset turing tighter is something that only comes with experience.
Getting specific about your flight video:
There’s a perfect example to focus on if you start watching at about 2:10. Since we can hear your vario, we can tell that you are in weak lift already- but at about 2:15 you definitely fly into a stronger ‘core’. We can hear the vario indicating the climb rate is increasing, increasing, and at about 2:18 we can hear that the climb rate is slowing again. This tells us that, flying pretty much straight, you had a solid 3 Mississippi’s in that core… which means it’s big enough to 360 in. Since it’s not huge, you’ll have to bank quite a bit to keep your entire 360 within that core. How much to bank? Well if you do a few 360’s and keep adjusting where the center of your circle is, and you still can’t get a full 360 with the vario beeping, you probably need to tighten up some more. If you’re getting full 360’s in that core you could try flattening your turn out a little and see if you fall out of it or stay in it. Thermals are also ever-changing, so these are questions and exercises you should be continuously doing any time your climbing, until they become second-nature. The best thermal pilots know when you widen and when to tighten to make the most of their thermal.
A common mistake newer pilots tend to make is flattening out their turn as they fly through a stronger part of the thermal. This IS what you want to do if you need to move the center of your 360 over a little, but in the situation at 2:10 in this video, as the vario is beeping faster and faster, you should really be banking steeper and steeper. By flying straight you are destined to fly out of that stronger part. This isn’t terrible, because now you know about how wide it is… but now you’ve got to do a 180 and fly back into it. What a lot of new pilots end of doing is flying relatively straight through the lift, and then doing a 180 in the sink surrounding the lift. That is terribly inefficient! So as you’re flying into the core and the pitch on the vario is increasing and increasing, start to turn! By the time the glider rolls, and then actually starts to turn, that’s about the right timing to keep you in or near the core. And if you’re 360 isn’t centered, now you can go through what I talked about earlier with extending one side of your 360 in order to adjust where your 360 is centered.
Thermalling is part science, part art. It is one of the hardest things to learn (or teach), because there are just so many variables. We are ALL constantly working on climbing better. The most helpful thing to knowing how to thermal is experience, which comes from practice and repetition… and there is no shortcut for that. What you CAN do, is exactly what you’ve done here- ask for help. Also remember people are nice, so you need to be your own worst critic- look for mistakes and what you could have done differently. Ask specific questions about specific things (do you think I should have turned left instead of right when I hit that thermal? WHY?).
Looks like you are doing great, and you’ve got a pretty ideal place to fly and practice! Get back up there and do it again!