Toward the Windward Side

The nose yawed toward the windward side, and the glider did not climb again. It was still passing through the present patch of air; its ground track had already turned, but the lift did not strengthen with the turn. A few minutes earlier, a similar heading and airspeed had still carried the aircraft upward; the present weakening alone was not enough to conclude that the mountain wave had shifted. The pilot did not wait for the cause to become clear. The deflection had already begun.

If it first entered the sink on the downwind side, the return would have to be made into a strong headwind. The difference between the two directions had already fallen onto the ground track before the outcome appeared: one side searched into the wind for the lift just lost; the other would carry the aircraft into descending air, then require it to come back upwind.

When the wave pattern is stable, adjusting heading and airspeed can indeed let a glider continue using the stronger area of lift. The aircraft was not suspended in the air; the wings were always moving rapidly through it. Flying into wind only canceled part of the movement relative to the ground. At a lower speed, the track would slide downwind. That set of controls had worked a moment ago, but now it did not bring the climb back.

The aircraft continued crossing toward the windward side. The air it was now passing through did not maintain the earlier lift, and new stronger lift did not appear at once. The deflection carried it away from the track that had just been working, but had not yet brought it to another confirmed position. In the cockpit there was no airflow map with boundaries already drawn, only the ridge moving slowly relative to the cockpit; before any result had appeared, the aircraft had already spent altitude and distance.

This direction did not necessarily conceal stronger lift, nor did being chosen first make it correct. It was simply not yet deep inside the area of sink that would require an upwind return. In the later wind drift, the aircraft might pass again through the rising side of the wave.