Gann
states that they would climb to 100 feet above their cruising altitude and
then descend the 100 feet back down. He called this "flying on the step."
He claims that it bought them a few more knots of airspeed.

Makes no sense to me... that is, if you mean this as a continuous process (up, down, up, down). Once you are at the most efficient speed (however you define it), deviating from that speed in either direction reduces efficiency. In terms of energy,
you get back all the energy of the climb in the descent - but no more. However, you dissipate (waste) more energy due to friction at the higher speed, which is when you are regaining the energy you spent to climb to the higher altitude. Friction
goes up as the square or the cube of the velocity (depending on the realm), which means you lose more going faster than you gain going slower. So the best way to achieve a certain average speed is to fly at that speed.

Jose
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