One of the more challenging aspects of every wave flight of Perlan 2 is the tow. On the September 9, 2017 wave day the air that the CNVVM tow plane and Perlan 2 flew through was dynamic. It could be compared to a moderate roller coaster ride. The video linked below shows a 4 minute composite of that hour long tow.
Wave lift is the result of strong winds blowing across a mountain range. (See the wave graphic vertical cross section.) The air is forced to go up over the mountains but then rapidly sinks toward the valley floor. Then there is a rebound effect similar to what can be seen in a stream. When fast moving water is forced over big rocks you can see the waves generated downstream of the big rocks. Whether in the air, or the water, you can see wave harmonics downstream. See satellite screen shot from the day of this flight. The satellite view clearly showed the "wave bars" or harmonics under some higher level cirrus clouds. There were lots of clouds pushed up against the Andes Mountains on the Chilean (lefthand) side and wave bar harmonics downstream on the Argentine (righthand) side of Andes Mountains. On any day with mountain wave lift in the air there will also be sink between the wave bars - or what goes up must come down. My apologies to meteorologists for the simplified description.
On September 9, 2017 the Perlan 2 launched into mostly calm air with Jim Payne and Tim Gardner behind Cholo in the CNVVM Boero. However very soon the tow plane and glider started climbing through air going up, then down, then up again. It looked like a roller coaster ride - with no tracks! The rope connecting the two aircraft was stretched tight, then went slack. One way to tighten slack rope is to move the nose of the glider a bit more left or right. Seeing the tow plane from Perlan 2's eyeball windows is a challenge. Seeing the rope can be extremely challenging.
The turbulence encountered on the day of the video would be considered mild to moderate. At the end of the video the glider released the tow rope and executed a tight turn to the left. This marked the beginning of soaring flight. Once established with the nose of glider pointed west into the wind the Perlan 2 started rapidly climbing at over 1,000 feet per minute. (Like a homesick angel)
For a four minute aerial "roller coaster" ride in 3 dimensions, join Perlan 2 in "Turbulence on Tow" in our YouTube video edited by Tim Davis https://youtu.be/4HU3-0FyaZM For a superb time lapse video of how much spinning energy is inside the rotor zone go to https://mobile.twitter.com/ChessInTheAir/status/960902790485651456/video/1
Perlan Soars High! Jackie