Mountain wave lift – what is it?
Wind blows 90 degrees ( up to 45 degrees of either side of 90 is ok too) to the ridge lines. Air is forced upward, and after it passes the crest, it goes down the back side of the ridge, and depending on the stability of the air, ripples in the air mass are caused, just like ripples on a pond. The air going over the ridge does not compress. The entire air mass rises as it passes over the ridge and the resulting ripple on the downwind side is often a massive exaggeration of the initial upward push caused by the ridge line. Many of us have flown our gliders in mountain wave to altitudes well over 25,000 feet.
Why do we need a special coordination to fly at higher altitudes?
If you know your airspace rules, you know you are not allowed to fly above 18,000 feet without express permission from Air Traffic Control (ATC). To facilitate meeting all of the requirements imposed by ATC, we have established “wave windows”. A wave window is a specific parcel of airspace in which the glider pilot is allowed to operate the glider above 18,000 feet up to a specific altitude. The Window has specific boundaries both laterally and vertically. Pilots are not allowed to operate within that wave window without clearance.
Current Procedures for the Williams Soaring Wave Window