ASW-20 flying notes

by Andreas Maurer, 1997

Well, how does it fly?

Basically: Not so simple as a Pegase.

Winch launch

This is exactly the same as with a Pegase: Flaps neutral (Setting 3), trim neutral, and no flap change during the winch launch. No problem at all - the 20 does not tend to "jump" into the air. Very simple.

Aero tow

This is not so simple.

Start your takeoff run with flaps 2 (ALWAYS! Aileron control is weak during the first twenty meters), and when you feel the controls become effective, slowly and carefully move the flaps to 3. Usually you will be rather fast when you do this and lift-off in the moment when your flaps have reached 3.

Be extremely careful not to overshoot 3 and get accidently get into 4 since your aileron power is reduced nearly to zero (!) with the flaps in 4. You won't be able to stop one wing from dropping.

It sounds harder than it actually is: Get into your 20 and practice this a few times before takeoff. Push the flap lever to the left during the movement, and you will not miss the hole even if you do not take a look at it.

During the first phase, use your ailerons extensively! Since the deflections are so small, they need nearly fully deflection to show some reaction. But I'm sure you are used to this from your Pegase.

The first phase of the aero tow becomes more difficult when loaded partially with water - be extremely careful to keep your wings balanced!!! Once a wing is dropped, it becomes difficult to get the wings levelled again.

Well, so much about aero tows. Do your first flight with a shallow wind from straight on (the stronger the wind the easier the aero tow gets), and I'm sure you will have no difficulty. Set the trim exactly into the middle of the first half of the trim range - at 25 percent.


Of course this is very different from any non flapped ship.

For the 20 there exist three important speeds: 40 kts (75 kph) - 57 kts (105 kph) - 67 kts (125 kph).

These are the speeds for flap setting changes.

Below 40 kts: 4
40 kts to 57 kts: 3
57 kts to 67 kts: 2
over 67 kts: 1

When flying with a wing loading of over 40 kg/m^2, the speeds move up about 6 kts (10 kph) at the full takeoff weight of 454 kg.

The ASW-20 flight manual states other speeds, but they are slightly wrong: 43-60-70 kts (80-110-130 kph). You will notice a wrong flap setting immediately: If your flap setting is too positive, you will feel (!!) the brake effect. It will actually feel as if you used the brake in your car. A too negative flap setting is coupled with far less drag increase - so better use a too-negative than a too-positive flap setting.

And you will notice one more thing: Flap setting 4 will nearly always have the effect of a brake. In my opinion (and as experience shows) 4 is not a good flap setting - I only (!!) use it while flying straight on at less than 40 kts (75 kph) in order to climb under a cloud without circling.

And a slight side effect of 4: The 20 likes to spin with 4. Flying very slowly (under 40 kts, 75 kph) with 4 and getting a gust might result in an unwanted spin if your CG is far aft. Be careful with 4! This difficult stall behaviour with 4 is also the cause why I do not use 4 during a winch launch.

You usually will not fly slower than 43 kts (80 kph), so you will not have to use flap setting 4. When circling in the thermal you will also notice that with setting 3 the 20 is *MUCH* more agile than with 4. Besides, with setting 4 she does not build up speed you can change into altitude by pulling up.

The consequence is simple: Use 3 (!!!) as flap setting while circling. It even works with a wing loading of 42 kg/m^2 (in my opinion that's the optimal wing loading for the 20, with less weight it loses some of its high-speed performances). Circle at 48-52 kts (90-95 kph), and you will climb at least as good as any LS-6, LS-8 and better than any Ventus.

I only use flap setting 4 when I have to do a very sharp turn, because at too high bank angle with setting 3 you will feel a slight buffet when you pull it into a sharp turn. Pulling the flap lever between 3 and 4 stops the buffeting. If you have to keep this sharp turn, use 4, but usually you should be able to reduce to 3 again.

When flying with a wing loading of 40 to 43 kg/m^2, circle at 51 kts (95 kph) with flap setting 3. This is also the optimum flap setting. Flying with more wing loading is not useful since the CG will move too far forward, the limited forces of the elevator will stop you from climbing. According to my experience it is not useful to fly with a wing loading of more than 42 kg/m^2, even on strong days.

Flap handling

Your left hand will get a lot to do, believe me...

Always keep in mind that the flaps are used to keep the angle of attack of the airfoil in the optimum range (which is quite narrow with any 15m-ship). That has two consequences on your flying:

It takes some time to get the feeling, but you'll learn it. But don't worry, it takes about 50 to 80 hrs to get used to the flaps so much that they are really an advantage for you...

Well, so much about flying this ship. I'm absolutely sure you'll learn to adore the flexing wings during flight. In my opinion this is the most comfortable glider ever built since it flies extremely smoothly but is also very sensitive for thermic.


Not much to say about it. The extreme flap settings sound more difficult than they actually are.

During downwind set flap setting 4, and trim the 20 to about 46 kts (85 kph), your optimal approach speed (absolutely sufficient!). Gear of course down. Plan your traffic pattern a little bit closer than with your Pegase - actually the normal approach angle of the 20 is very close to the one of a Ka-8, but much, much steeper if necessary. Plan your approach as if you flew a Ka-8.

Well, and after your turn into final, set the flap setting 5. The nose will rise, and you will have to push. Extend your airbrakes, and enjoy! You can keep your glide angle with the stick - point with the nose at 150 ft (45 m) in front of your touchdown point and set the airbrakes to keep 46 kts (85 kph). The flare will be automatic, too. You will probably first touch down with the main wheel, but with some experience it is also possible to land it with the tail wheel first (but that's not so easy since you will stall the 20 out, connected with a sudden loss of lift and aileron effectiveness).

After touchdown, most probably the wheel brake will not work very well - a common problem of all older Tost brakes. But since you touch down at about 32 kts (60 kph), it will be no problem...

And now to the gimmick, the "sharp" landing with 5 and fully extended flaps (setting 6). You should have made a couple of landings with 5 first. 6 brakes very impressing - as much as fully extended airbrakes on your Pegase, but with a nose-down attitude of the whole glider. Then add airbrakes, and you will fall like a stone...

You should try this manoeuvre at greater altitudes: Set flaps to 6 (I prefer to do this at 43 kts (80 kph) since the forces on the lever are rather high), push down the nose, and extend the airbrakes. Then push down the nose until you have reached the Vne of 65 kts (120 kph). For the first 500 ft (150 m) you will fall at a 60 degree angle, and the rest of the glide towards the touchdown will be controlled via the stick - just point and land...

If you want an optimal short landing roll, make sure that you have exactly 46-47 kts (85-87) kph prior to the flare.

Most probably you will have to release the airbrakes prior to touchdown, but the flare with fully extended flaps and airbrakes is very, very short - the airspeed will bleed off extremely fast!!!! So make sure that you do the flare at exactly the right altitude - you will have only one try, and there are nearly no corrections possible. This behaviour is the cause why the later 20s and the ASW-27 do not have such an extreme flap setting.

Be extremely careful to be high enough to reach the airfield when using flap settings 5 or 6! It does not have any negative effect if you change from 5 to 6 or 6 back to 5 in order to reach the airfield (the 20 does not lose any altitude during this manoeuvre), but after some time you will get used to flying much smaller traffic patterns and steeper approaches.

Sure, it takes some practice, but once you have a good command of it, the 20 will be the safest glider in the world to land safely on a short field , perhaps over some trees.

If you do a "long landing" in strong wind use flap setting 3 instead of 4. If you use 4 your main gear will be the first to touch down, and most probably you will be jumping into the air again for the next five touchdowns. And of course the aileron effectiveness is reduced very much with 4... Use 3 instead, then your tail will touch down first, and you will stay on the ground, coupled with good aileron effectiveness. The airbrakes are much less effective than those on a Pegase with this approach, so make sure there is plenty of airfield ahead of you.

Notes on minor things


It only likes to spin with flap setting 4. Be careful when stalling it at 4! Spin entry might be very quick and violent, immediately starting the rotation. Once in a spin, recovery needs two things: The normal method, rudder opposite and neutral stick, and flap setting 3 or 2 !!! With 4 it takes a half turn more to recover, and you might violate the Vne for flap setting 4 (85 kts, 160 kph) during the recovery.


Check the rubber bands that keep the gear doors closed. They like to wear out, and then the gear doors open in flight.


You can remove the back rest and fly without it, if you have not enough space. I measure 2,01 meters and have plenty...

Wing seals

They seem to bring a lot of performance. Make sure that they are applied.

Well, so much about flying an ASW-20.

Some things sound a little bit complicated at first, especially the flap stuff, but remember that it takes some time to learn it. After the first year you will stop thinking about it. When I fly a non-flapped ship (which does not occur too often!) my left hand always wants to move a lever that is not there...very annoying!