Sunday, November 06, 2011

Dual Flight over Early Snow

Friday brought a fast-moving cold storm to Southern California. Saturday looked to be clear skies and cool aloft with possible thermals to 9 or 10,000 feet, but also possibly windy to 15 knots, with the wind maybe too westerly to make good wave. As I was driving to the airport another pilot called and we talked about sharing a flight, so I prepped our Grob 103. It's the better ship to be in if the winds get strong, but its oxygen tank is out for repair, so I knew we couldn't go too high if the wave was working. We needed to do several items of maintenance, but that gave us some time to get early flight reports from a couple of other pilots. It sounded like a high tow over the mountains might be the only way to fly today, so I was glad to be splitting the tow fee.

There were lenticular clouds to the north, but way too far away to be useful... that's common at Crystal.

The wind was from the west but not very strong, 5 knots most of the time. There was obviously a gentle south wind coming over the mountains, pushing clouds over the rim into the desert as you can see in the picture. And we were told there was an east wind aloft, so ridge lift on the east side of Mt. Lewis was a possibility. And with the clear air, thermals might pop too. So... the air was in a lot of motion today - what would we find?

I took the rear seat, and G as PIC took the front. He said he had not had much experience with wave or ridge soaring, so he thought maybe I'd do much of the flying and he'd to the takeoff and landing. Fine with me. I took myPDA/GPS device hoping to get a trace of our flight. As we were pushing out to the runway, a cigar-shaped lenticular cloud formed right between us and the mountain, so smooth wave was happening. But by the time we took off, it was gone.

Another pilot reported that the rumored ridge lift on Mt. Lewis was not working, and the spillover clouds were really getting thick, so we let off at 8500' kind of in front of the mountain and went looking for ridge lift in various places. G didn't find anything so after a while he turned it over to me. I had seen some raggedy little clouds in a rough SW-NE line that I thought might be weak rotor clouds, but there was no real lift next to them.

So on the theory that the west wind might be making ridge lift or weak wave, I tried a north-south line over the low end of the Second Ridge. I did find some narrow lift and was able to work up in it through several back-and-forth passes. I tried to keep my lines tight in case it was a narrow band, and that seemed to work. The picture (click to expand) shows a trace of that portion of the flight. It was not smooth enough to be wave, and there was no obvious north-south ridge to be making orographic lift, so what was it? I thought maybe the nose of the Second Ridge was creating what they call "bow wave", but the wind wasn't really strong enough for that. It didn't last long, but I gained 1,000', so we had time to fly around.

Didn't find much after that, and eventually got low enough over the ridges that I decided to head toward a weak little lenticular could that was perched over the airport. I found neither good lift nor good sink on the way, and by the time we got there the lennie had disappeared. I gave the plane back to G and he went in search of thermal lift on the way back to the landing pattern. There may have been a little, but it was pretty weak and not working.

There were a few other odd little lennies to the west, but too far for us to reach. We came in for a landing after 51 minutes. The surface wind was still from the west and only about 5 knots, so it had never really picked up.

We had seen a glider above us and later below us when we were working the one area of mysterious lift. Back on the ground, instructor D asked, if that was us he saw, and commented that the shear line had been good but had disappeared as we worked it. Then the light went on! The wind from the south over the mountain, and the wind from the west, were colliding and going up. It wasn't ridge, or wave, or "bow wave", or thermal - it was convergence! I'm gonna need a checklist just for all the different kinds of lift we find in the chaotic environment over the mountains!

No comments: