Wow that's interesting stuff. I once went to a WW2 glider museum in Iron Mountain Michigan, but it was more about the manufacturing and stories and less about the design and flight characteristics. The only time I've ever noticed any kind of wash from a towplane is on pavement behind a CAP 182. 100' into the takeoff roll, the right wing always drops. It's a briefing item when we fly there. Spiraling slipstream of a tri gear vs taildragger.

It's a shame we can't put a glider and towplane in a wind tunnel together....or at least some smoke/fluid testing released from the towplane wingtips. So much of aerodynamic "fact" isn't really known, but more speculated and generally accepted. Would be a pretty neat study to actually watch said downwash. I still have never noticed it in flight; It was explained differently to me many years ago, and it has always seemed to prove to be passing below me. If the glider keeps the towplane referenced on the horizon from high tow position, they're essentially level horizontal with each other. That means that the towplane is not dragging the glider through it's path, but rather the two are climbing together, a level horizontal plane going up. (Most gliders' drag in lbs at a tow speed is probably only 50ish pounds...so the tension on the rope wouldn't be much more in order to yield a climb at constant speed. Similar to the discussion on excess power required for climbs in the book Aerodynamics for Naval Aviators). If applying that theory of the horizontal plane climbing evenly, and towing at say 60kts and 500ft/min (for simple math), that's a climb gradient of 500ft/nm, or 5 degrees. So the relative wind is essentially from 5 degrees above the horizon, and downwash results in 5 degrees off below to the rear, or more depending on angle of incidence, etc. That, at 200, back, puts the theoretical downwash line a little over 15 feet below the level horizontal plane that the glider exists in with the towplane. So clearly in that theory, a weak towplane and a heavy glider has many issues beyond clearing the trees, but a strong towplane makes everything less of a factor.

Again that's just a theory, just like the perceived downwash one. My only point here is to say that all this stuff is theory, something from voodoo black magic aerodynamics. It would be truly interesting to hook up some smoke canisters across the wing of the tug and see where it all goes. Same with the tips.

I would love to hear the perspective of military guys here who have done many hours of aerial refueling...what they think about the presence of downwash and how much it affected their aircraft when sitting behind a tanker (with a much higher wing loading).

Jordan