ASW-20 notes

These notes are a description of the things that struck me as significantly different from the club's Standard Class gliders when I converted onto my ASW-20. Be aware that I only have 35 hours on type though I did get Gold distance in 123. So, if you notice a difference of opinion between Andras, or any other experienced ASW-20 driver, and my comments you should take what I say with a grain of salt.


Before you start to fly an ASW-20 you should read the ASW-20 handbook as well as Andras Maurer's handling notes. He has a lot of hours in one and knows the glider well.

What you need from the handbook:

Differences between the ASW20, ASW-20B and ASW-20C models

The main differences between the models are:

Some examples of the A and B models were retro-fitted with a lifting instrument panel. I think this was standard on the F model, which was built by Centrair in France. Almost all the modified ones use the Centrair/Pegase panel and canopy support because it's relatively easy to fit. I believe it's always been an expensive modification, but in my opinion it is a useful one.

All models have seven Hoteliers to connect and disconnect. If yours doesn't have Weedekind Sleeves consider getting them fitted. That makes it much easier to connect all six wing Hoteliers, which are single-handedly connected and disconnected through a rather small hatch.


Winch launching is no problem. Just don't look at the tips during the launch because they're waaay up there!

Aero tow is a handful: you need to start with the flaps at -6 degrees to get any aileron response at all. The ailerons start to be effective at 30 kts and you need to select zero flap immediately you feel them bite: the ASW-20 won't lift off in negative flap. If you're in zero by the time you hit 35 kts it will lift off gently but if you're slow and are at 40 kts by the time you select zero it will really pop up off the ground. A word of warning: if you miss zero and select thermal flap by mistake leave it there despite the poor aileron response because you'll drop really fast if you go back to zero on tow. Towing in thermal flap is OK despite the poor roll rate because the thermal flap Vne is high enough for all normal towing.

Normal flight

The flap only has five settings (six if you count the Jesus setting), which is fine for the first three, which are very fast, fast and cruise, and for landing flap, but the gap between cruise (zero) and thermal flap is so big that most people make little use of the thermal setting. The ASW-20 climbs well in zero flap at 45-50 kts anyway, but in thermal flap it feels really stately and is starting to get spin-prone: they are famous for spinning in thermal and landing flap settings. Twice mine departed without warning when I was thermalling in zero flap at 45 kts and a 45 degree bank. Both times I had it back within a 1/4 turn, but 300 ft lower and at 80 kts. They are very slippery. By the way, I tried to make it do this in calm evening air, but it wouldn't depart, so I think there needs to be small scale turbulence in the thermal for it to spin from a normal thermal turn.

Spin recovery is straight forward. The first action is to select full negative flap because positive flap settings have a Vne that is dangerously low for spin recovery. Usually this is enough for it to auto-recover before you have a chance to use the normal spin recovery actions.

Because of the large speed difference between zero and thermal flap (57kts to 42kts) a common modification is to cut another flap setting notch midway between zero and thermal flap. Mine didn't have this but I imagine its really useful. The factory thermal setting (+8 degrees) is a bit too much so I think +4 degrees could be on the button.

The controls feel a little stiff in roll. I think this is because the flap/aileron mixer adds a small amount of friction, but the roll response is good in normal flight. Its terrible on the ground because the ailerons are tiny and the coupled flaps don't fully compensate for that. The trim springs are very strong. You'll really notice that, but its not a big problem because you can trim for best glide (57 kts in zero flap) and do all inter-thermal speed control with the flap lever. If you use thermal flap for climbing there's almost no need to touch the trim except for take-off and landing.

You'll notice almost no attitude change with speed in a straight glide which does tend to mess up your speed perception. When you select negative flap the fuselage pitches up about enough to counter the pitch down that you'd expect from accelerating an unflapped glider. Remember that negative flap makes the wing chord more negative in relation to the fuselage, which raises the nose relative to the wing. Using flaps isn't hard but it is different. Imagine you learnt to drive on an automatic and then converted to a manual gearbox. Its the same: moving the flaps is easy, but being in the right flap setting at all times takes a lot of practise. I expect you'll take at least 30 hours to get to that point: I certainly did.

The ASW-20 is stable hands off in straight flight. When I tried it in zero flap trimmed for 57 kts it developed a 20 second phugoid, which is a slow vertical oscillation. During this the speed varied over +/- 5 kts in phase with the phugoid. It built up slowly and then stabilised at these values, which I measured by watching the ASI and timing the cycle period. All slippery gliders do this. Its not a problem: if you're holding the stick and paying attention it simply doesn't happen. ASW-20s are docile in normal flight. You can get a drink, take a photo or a pee, find a sandwich or look at the map without it suddenly biting you.

What it is not is stable hands off and feet stationery in a turn. Clean or wheel down the ASW-20 does not show a benign spiral. From a trimmed speed of 50-55 kts. The turn tightens so that by the time its turned more than 180 degrees there will be more bank, the nose will have dropped and you'll have gained at least 20 kts. Don't even think of getting into cloud in one unless you have instrument training and blind flying instruments installed. That's really a warning should you go wave flying with an ASW-20: you really don't want to be caught above cloud in one unless you have an artificial horizon fitted and are in current practise with it.


Landing is pretty easy. Once you're in landing flap you use the brakes as normal. A typical approach would be to fly the pattern in zero flap and use the same approach speed as you would in a Pegase. Turn base at the same point as usual and then fly finals, still in zero flap, until the edge of the field is alongside the instrument panel cowl. At this point you'll think you're far too high and close but don't worry: overshooting in an ASW-20 is almost impossible on a normal airfield. When you're sure you're in, select landing flap. Give the stick a good shove while you're moving the flap lever or you'll loose 15 kts instantly. Now use the brakes as normal for the approach. The ride down is good and controlable but do keep an eye on the speed because with flaps down it won't accelerate very fast even with the brakes closed. The round out and hold off are similar to an unflapped glider with full brakes out. However, you shouldn't add 5 kts for luck as you might in an unflapped glider: the ASW-20 won't stop flying until its down to 32-33 kts and that extra 5 kts will float you into the next county. Once you're used to the steep descent you'll find landings are no problem at all. To put numbers on it, in landing flap and full brake an ASW-20 can manage a 1:4 descent rate, or about twice what an unflapped glider can do.

You can land an ASW-20 in zero flap but by themselves the brakes are fairly weak, so the approach needs to be fairly flat.


- Martin Gregorie, 2008