Another weird example of dynamic soaring:

A friend of mine used to fly control line model airplanes, "back in the
day".

One day, he just happened to be flying in an up and down flight path. A
day with strong wind. The tank ran dry and the engine stopped. He figured
he would land the model, but for some reason, continued another circle with
the same flight path....low, almost to the ground on one side, while very
high on the other.

To his surprise, the model did not loose speed, and was able to climb to
the same height. He continued circling, and the plane continued on the
same flight path, same speed, without engine!!!

It was pure luck that his up and down circle was in perfect alignment with
the wind direction so as to take full advantage of the wind gradient near
the ground.

I later read in magazines about other control line pilots who experienced
the same phenomenon. There were a series of control line modes which were
designed to specifically take advantage of the "dynamic soaring"...I don't
think those guys called it that.

These models had no engines...they were build very light and extremely
strong. You did have to use a "whipping" action of the control lines to
initially get the plane flying, but once up to speed, and the up and down
flight path established, the models would continue at high speed, and were
fully maneuverable...just like a powered model!!

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