The up and down sides of rotors relative to ridges

My thinking is that for a wind blowing towards the east, the top of the
rotor is also blowing east and the bottom of the rotor is blowing west,
so the lift side of the rotor is to the west of the sink side. This is
idealized because if the feature causing the wave is convoluted and
irregular, all sorts of chaotic interactions can result in unpredictable
patterns.
That's right, and I don't think it can be predicted, hence my original
position that I would not penetrate upwind looking for the up side of
the rotor unless I had plenty of altitude AGL and a place to bail out
(figuratively). I have personally worked rotor up into wave an several
occasions, but I've always had at least 5K' AGL when I did it. This is
the nature of western flying.
--
Dan, 5J

At 16:40 08 April 2016, Dan Marotta wrote:
My thinking is that for a wind blowing towards the east, the top of
the
rotor is also blowing east and the bottom of the rotor is blowing
west,
so the lift side of the rotor is to the west of the sink side. This is
idealized because if the feature causing the wave is convoluted
and
irregular, all sorts of chaotic interactions can result in
unpredictable
patterns.
That's right, and I don't think it can be predicted, hence my
original
position that I would not penetrate upwind looking for the up side
of
the rotor unless I had plenty of altitude AGL and a place to bail out
(figuratively). I have personally worked rotor up into wave an
several
occasions, but I've always had at least 5K' AGL when I did it. This
is
the nature of western flying.
--
Dan, 5J

I think Dan is right in the fact that there are a lot of variables which
will affect the issue. Mt. Washington in NH is set up similar to what
SOF describes. A high mountain in the west, a sharp V shaped
valley with the Wildcat ski area (lower mountain top) just to the
east. Oct 8, 1966 was the first day of modern wave exploration
there. Four of us got our Diamond altitudes that day. We didn't
know a whole lot about wave, and we operated from the North
Conway airport 23 miles to the south. Alan MacNichol towed us 23
miles through the continuous rotor of the Moat Mountains to get to
Pinkham Notch right in the middle of the valley. We were at about
4200' MSL which was ~2K' below the top of Mt Washington, and
about 2K' AGL. With the L-19 in a 45 left bank, and my 1-26 going
45 right, (both with full opposite control inputs), I released because
there was no other option. I was lucky. After turning right 270
degrees with full controls against, I finally came into the wind and
leveled out. The vario was pegged at over 1500 fpm up, and I was
spit upwards into the wave, where I cut the climb off at 24K' due to
airspace limits at the time. I landed after 1.5 hours and briefed a
fellow club member who had just showed up with his Ka-6. He
experienced the same tow, but was in heavy sink on release. He
dove for the Wildcat ridge thinking it would work. It didn't. The
rotor was going down-slope there. He wound up thrown into the
trees while trying to land in the ski area parking lot. Luckily, he
walked away, but I had to go get the Ka-6 pieces out of the woods
that afternoon. I think that wind speed and atmospheric conditions
will make the size / strength / location of the rotor vary, and that
will directly affect if the downwind ridge is working or not. I, for
one, would not bank on it working.....IMHO.....FWIW.....

Sometimes the rotor goes all the way down to the ground. I was leading a regional at Sugarbush, VT years ago when I arrived back 10 minutes early on a turn area task. The ridge was working OK so, like a chump--er, champion--I continued another few miles to the next turn.

Unfortunately the turn was out in front of the ridge, which--at that point--was stepped, with a lower front ridge and a higher back ridge. Out I went into the valley upwind a few miles to tag the turn (my second big mistake). On way back, it was obvious I would not have enough altitude to safely get to the back ridge with a margin to escape the high valley between the two ridges if the sink I was in didn't abate. No matter, I rolled in over the front ridge and turned north.

More sink! And rough. I must not be close enough. I slid in tighter to the slope. It was really rough now but I was still going down. I could see the leaves being thrashed wildly on the slope. Wind. It MUST be going up! Nope.

By this point I was sinking below ridgetop height and getting pretty upset with the theory of ridge lift, the unfairness of life, and the prospect of going from 1st to last place in one flight. I flew around the corner where the front ridge turned into the main ridge hoping desperately that the different angle might produce different results. No way. Eventually (actually, very quickly) I picked a good field.

Nearby was Kai Gertsen, with his extraordinary skills. When we finally regrouped, we agreed we'd fallen victim to rotor from the upwind mountain. The ridge had been working as I flew south so I hadn't known or worried about it. But the minute I came off that higher back ridge, I was in sink and turbulence and it went literally into the trees on the lower front ridge. Lesson learned. Yes, we were two of the only non-finishers. And, no, it didn't help that I wasn't the only one.

Chip Bearden