Sailplane angle of bank vs circle diameter
Tags
circle angle of bank

A pilot can train and safely fly to solo standard without learning to circle. Sure, he can turn the glider, and if the thermals are huge he can wander around in them and go up a bit. But this isn't good enough to make progress in the sport of cross country soaring. And pilots that don't make progress are likely to give it up.

The first thing I do in any coaching session with a new pilot is to see if he can circle continuously at 40-45° of bank, at the appropriate speed, without slipping, skidding or jerking the nose up and down. If a pilot can do that, then can he take off the bank and put it on again, back up to a tight turn, again without slipping, skidding or making the nose go up and down? Many pilots simply can't do it tidily enough to soar properly. Doesn't sound hard, does it? Trust me, it is difficult for a low-hours pilot to achieve.

Why turn so tight? Because thermals are small. Yes, I know, I've flown in the high desert and the Sierras: big powerful climbs, easy and fun. On the good days, when you're in the right place. But how about scraping a ballasted 15m racer off the ridges at Mifflin, at all of 1kt, or digging yourself out of a hole when you get the wrong side of the convergence at Mono Lake. Now you have to turn really tight in exactly the right place. Pure handling skill is essential.

So here's a couple of things that might help you improve.  (See banner photo)

First, measure your thermals. If you fly across a new thermal at 60kt you're covering 100 feet per second, give or take. Count how many seconds you are flying in the core. In most cases you'll only be in the best bit for three or four, six, maybe eight seconds. A ten-second core transit is pretty rare (unless, as I said, you're in the high desert on a good day etc...)

If you climb at around 50-55kt then a 20° bank gives a circle approximately 1000' across. This isn't what I would call circling, it's merely wandering around the countryside in vast arcs. 20° bank won't keep you within most thermals. A 30° banked circle is 600' across, giving you a better chance of success. At 45° you get down to about 500' across. That would just keep you within a five-second core - five seconds across at 60kt. It's not practical to turn much tighter than that for more than a few seconds - too much g and far too difficult for most pilots. And, frankly, not usually worth the effort.

Now calibrate your angle of bank. It's incredibly easy: your ASI, altimeter, and vario are mounted with screws at each corner. Line the diagonal up with the horizon and that's your standard climb angle of bank - 45°. OK, you have to hunker down and squint a bit to achieve this, so you could put a little wireframe or piece of card onto the coaming, in your sightline underneath the yaw string. It's a bit of effort but well worth it.

Lastly, make sure that you are using a method of centering that entails turning at 45°, no less, every time that you are in the core of the thermal. There are many different ways to climb and there isn't time to cover all that right now, but if you're not turning hard when you're in the good bit...then I'm going to climb away from you. Some thermals do reward a different technique, and other gliders will get in your way. But not very often: the best policy is to turn tight. So when the vario is peaking you should be sitting at that 45° bank. If you want to move the glider around to centre the climb then do it when you're not in the best bit of the thermal: always turn hard in the core. On average this will pay off.

Now you may or may not be able to achieve this at your own level of experience and skill. 50-55kt, nose in the right place, not going up and down, and the yaw string either exactly in the middle or a showing a slight slip - never skid. Oh, and at 1000' agl in rough air on a hot day, after five hours airborne already. We don't do this because it's easy, we do it because it's hard.

If you can't do it right, then you know why you're not climbing as well as the experts. Get onto it and practise! Then we can talk about centering...

Have fun. ~ G

G Dale
   G Dale is the popular author of The Soaring Engine book series.  He follows the endless summer, working for the British Gliding Association, The Gliding Association of New Zealand, and the Gliding Federation of Australia, always teaching cross country flying. He’s also flown and worked at various gliding clubs around the world: at Nympsfield as Chief flying instructor, at Booker again as CFI, at Lasham as DCFI and soaring coach, and at Glide Omarama as head coach, with visits to Minden, Serres, Takikkawa, Narromine, Lake Keepit, and many other clubs as a peripatetic soaring instructor and mountain flying coach.