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Old March 26th 17, 11:35 AM posted to rec.aviation.soaring
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Default Will circular runways ever take off?

On Sunday, March 26, 2017 at 12:19:25 AM UTC-4, wrote:
On Thursday, March 23, 2017 at 11:31:26 PM UTC-7, Gert Bass wrote:
This might be a good idea for auto towing. We have 2800 ft of

straight runway at our gliderport. At 780 ft field elevation with a tow
vehicle like a V-8 Chevy Suburban or a V-8 pickup truck, we can get a
maximum of about 800ft AGL auto towing a 1-26, and maybe 475ft AGL
auto towing a 2-33 with two people in it. Except for the problem of the
wind causing a portion of the circle to be towing the glider downwind, a
circular runway would seem to be a good way to extend the runway length
indefinitely, and get more altitude for a given rope length.


This can actually be done on any normal glider field in the form of
towing up an down the runway. The towcar doesn't have a very big turning
radius, so no need for even a large (wide) field. And the glider is
already in the air when the towcar reaches the end of the field and can
make a much larger turn - kind of a teardrop reversal. The towcar can
also slow down a lot for the turn because the glider slingshots around
it. Like a waterskier who overtakes the boat turning.

This can be done several times back and forth and if the tow cable can
be lengthened/reeled out it could reach much higher altitudes than with
a winch launch. But it's rather crazy and a bit like below - better one
good straight setup unless you have a really loong field.
Of course very safe on a circular track if available


Regarding the up and down the runway multiple pass auto tow, with the turn around at the runway ends: Have you actually done it, or do you know anyone who has?

Our runway is dirt and is quite wide, at least 200 ft. so a turn around might be possible without slowing the tow car too much. We also have two shorter, narrower runways that meet together and also with the main runway ends, forming a triangle. Not an equilateral triangle, but fairly close to it. I'm wondering if this triangular circuit could be used to make multiple laps around the circuit on auto tow. One thing I thought of is that instead of a payout winch to let out more line, you could just start out with more line laid out in the first place in order to get higher. However, the trade - off with that idea would seem to be that the tow car would be further down the runway at the start of the tow, so the glider would not get as high by the end of the first runway run as you would with less line out at the beginning of a one leg straight auto tow. So the glider would have to make the first turn around(s) at lower altitude that can be reached with one straight run. Hopefully with each pass, you could eventually get higher than the single pass run. We found by trial and error that about 1100 ft of rope seems to work out for the highest auto tows in still air on our 2800 ft. runway on one pass straight ahead auto tows with our 1-26 and 2-33. We have also towed a DG-100 using the same length rope and tow vehicle. The DG was able to get about 150 ft higher than the 1-26, probably due to better, aerodynamic efficiency.



Isn't the circular runway standard float plane technique on small lakes?


Yea theoretically it is always discussed and for helos in confined areas
as well. In practice I find it doesn't work.
When do you need it? When you are loaded heavy. That means you use full
power to barely start climbing. The turning actually does use up that
little extra power every time I experimented with it - because you bank
quite a bit as space is tight. So setting up the departure in the
longest straight line possible has always been just as good if not
better and looks a lot more sane
Now, turning slightly into wind or to go over the lowest trees that are
off the straight departure is standard, but is far from spiralling


Not a float plane pilot, but I read somewhere that float planes also taxi around on the water in different directions when it's glassy in order to make wakes that allow the floats to break the surface tension on take off and get the plane airborne easier?


The historical evidence, i.e. back issues of Soaring Magazine, indicate that death of the pilot is the reason the practice of reversing an auto tow is not recommended nor endorsed. You have to go back to the '30's and 40's but there are graphic warnings in the letters to the editor. I learned on a winch in the '70's and even the practice of "kiting out the wire" is fraught with potential disruptions and anomalies. Entanglement of the aircraft is probably the chief bugaboo, and I might hazard a guess that with the lighter weight high-strength lines available now, it will be an even greater risk.. 1/8 inch steel has a lot less aerodynamic potential than the "spectra" used for its high tow potential.
Two of my dear friends (both having been instructors and nationally rated pilots), aerotowing a 2-33 in the 80's related how in turbulence the tug surged forward then slowed enough that the rope came back in a loop, wound around the wing and they were only able to extricate themselves by "ruddering" out of the loop a moment before it snapped shut.The rope/wire glider combination has to be kept straight at all times.