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I'm estimating some wing parameters for an imaginary airplane (simple college project). We are allowed to use coefficients for any basic types of flaps (plain/split/slotted/Fowler etc), but since I'm doing a glider I'd like to go with the one that's really used.

tl;dr - What kind of flaps are used in modern gliders (preferably training ones)?

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modern training gliders (like an ASK 21) do not have flaps. Flaps are used on high performance gliders because the pilot needs some more experience to operate them safely.

Gliders, especially training gliders control sink speed by spoilers.

enter image description here Image source: https://de.wikipedia.org/wiki/Luftbremse#/media/File:Alexander_Schleicher_ASK_21_2.jpg

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  • $\begingroup$ Wow, this is really amazing, thanks. Since I might have to use some kind of flaps to calculations, could you please explain briefly which flaps are used for these high performance gliders? $\endgroup$ – rafal.sz Dec 14 '17 at 21:14
  • $\begingroup$ @rafal.sz usually plain flaps are used because they are simple to construct need low maintenance and are easy and quick to operate manually through stakes. $\endgroup$ – Timothy Truckle Dec 14 '17 at 21:21
  • $\begingroup$ Flaperons are quite common as far as I know. They are, in contrast to powered airplanes, often used in upward pointing position to improve glide ratio in higher speeds. $\endgroup$ – Martin Dec 15 '17 at 8:23
  • $\begingroup$ @Matrin Do you have an example where it is used on a glider? $\endgroup$ – Timothy Truckle Dec 15 '17 at 9:05
  • $\begingroup$ Yep. I'll write more detailed answer later this day when I have more time to collect some resources. $\endgroup$ – Martin Dec 15 '17 at 9:09
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As Timothy already mentioned, most trainers do not have flaps, but when a glider is equipped with flaps, it would be most commonly in form of flaperons where full-span ailerons are coupled with flap control allowing common-mode motion both upwards and downwards. In contrast to the powered airplanes, flaps in gliders are used not only for landing, but also (maybe more importantly) to adjust optimal glide ratio for the speed currently flown. Thus upward turned flaps are common configuration during fast gliding between thermals for example.

Finding information for particular gliders, especially such mentioning flaperons explicitly turned to be quite hard. Pilot operating manuals usually just describe how to manipulate flaps handle without going into the details on actual construction. Typical placecard for flaps handle (from DG-400 manual) does look like this. Ranging from landing configuration to negative flaps. Typical placecard for flaps control

Particular gliders equiped with flaperons include (maybe not the most modern ones, but those I was able to find some more info about, good enough as examples IMO):

  • DG-800 and LS-10 has full-span flapperons. Mentioned explicitly in the flight manual: The wings feature single piece flaperons, which are driven at two places. The mixing of aileron and flap deflections takes place in the fuselage. (The same formulation exists in LS-10 flight manual.)
  • DG-600 -- according to the wiki.
  • ASW-20 (and probably some other Schleicher gliders too) -- there are two distinct surfaces on each wing, sometimes referred as "flap" and "aileron", but both of them actually moves according to the mixed inputs of both controls, the ASW-20 flight manual contains nice table of deflections: ASW-20 control surfaces angles
  • Eta has three flaperon sections on each wing, each with different mix ratio between control inputs
  • ... and many others, I believe
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