Real Life Examples: Highest Lift to Drag Ratios

[KJ_Lesnick]

I'm curious where I could go to find out information on aircraft with the highest L/D ratios for their mach number provided they're not classified

 

[Machdiamond]

Gliders. The Eta should be near the top but I haven't look at this for a long time.
And with powered flight, I would guess the two Rutan round the world aircraft: Voyager and GlobalFlyer since these are two point design airplanes - awful airplanes overall but exceptional at what they were designed for.
For higher speeds where Mach numbers matter, L/D is not a consideration because parasite drag becomes dominant and L/D refers to induced drag.
-Luc

 

[Sundog]

You might also want to look up strut braced wings as well. The HD.34 was an example of such an aircraft.

 

[KJ_Lesnick]

Okay, so at the upper end we got the Eta which has a top speed of 175 mph which is around 0.23 mach at sea level...