Wheel brake effectiveness standards

On Sunday, October 18, 2020 at 12:10:31 PM UTC-4, wrote:
On Saturday, October 17, 2020 at 1:37:06 PM UTC-4, Tango Eight wrote:
Let me provide another perspective.

I had around 300 landings in my ASW-20B. I don't immediately recall the number of field landings, but likely 10 ish. That glider, built in 1985, has a 5.00-5 Cleveland wheel / hydraulic disk. That glider weighs as much as a modern 18m glider (no engine). 380 kg dry, with me in it.

My normal habit following a field landing is to walk off the landing roll and self assess. Those landing rolls were never over 250', all but one or two were 200, right on the nose.

So the short answer is: that problem has been solved for 35 years. Copy what works, worry about more important things.

T8
Tango: you weren't clear whether you used the brake to get that short roll, or were they that short without braking?

In my off-airport landings the ground was soft enough that the roll was much less than 200 feet without any brake use. Good thing, since the brake on my glider is rather ineffective. I'll try not to land on the Lake Tahoe golf course :-)

I use the brake some times at my home airport, on grass, to try and stop reasonably close to my trailer, but have to plan the maneuver so that I have a clear space to keep on rolling into if necessary.

(In the video) Landing flaps + full spoilers on final, 48 KIAS, then tail first landing, spoilers still full open, maximum braking without rubbing the nose in the dirt. Even with landing flaps, minimum touch down speed is nearly 50 mph with spoilers open (that's the price of 7.6# wing loading and a 13% thick wing section). Getting stopped in 200' requires a powerful, easy to modulate brake. It's a great system, but it would be seriously less great with a crummy brake. More recent competition oriented 15 & 18m gliders land faster still and the brake is proportionately even more important.

Your Russia with you in it is 5.x # wing loading, thicker airfoil section, not really an apples and apples comparison.

T8