Sunday, July 26, 2009

Hot and Stable

Although this weekend wasn't as blisteringly hot as last weekend, it was still about 98F and quite humid. The various forecasts predicted possibly good soaring, but it was not to be. I think the main reason was a very strong inversion. As part of my morning weather analysis, I use a little web site from NOAA which provides an interpolated "sounding" plot for most any airport. (You can find it at I use the one for March Air Reserve Base, which is pretty close to Hemet. It showed a very strong inversion at 5,000 MSL, effectively putting a lid on most thermal activity. It also showed an interesting convergence of the temperature and dew point from 18,000 to 25,000. Which means if you could get up high, you'd find thick cumulus clouds. By 10:30 there were already cumulonimbus forming at about 13,000 over the mountains. They overdeveloped and it looked like they produced rain all afternoon.

So I just planned to do another commercial/instructor practice flight in a Blanik. I always hope to find some lift to offset the stalls and slips I'm practicing. A few guys reported some thermals in midafternoon, but due to insufficient tow plane capacity, I didn't get up until after 3:30, and what little lift there may have been was gone. I spent much of the afternoon pushing gliders around, running the wing for others, and waiting in the hot sun.

I practiced boxing the wake, removing slack line on tow, then shallow slow-flight turns, incipient stalls, speed control while entering turns, and a full stall. There was a little zero-sink air and a little strong sink. I flew over the airport to review the pattern for the power runway - the examiner may want me to fly a pattern on the other side with the power traffic, so I plan to practice that one day soon.

As described before, I'm practicing flying the pattern with no drag devices (flaps or spoilers) because that seems to be an item on the commercial practical test. I think my directional control in the forward slip for the full downwind leg was really good, as well as a turning slip to the base leg. And I made sure to be looking for traffic in both patterns the whole time - that's another item the examiner is strict about, but it's always been a good habit of mine anyway.

Once on final approach, it became obvious I was not going to need to reverse my forward slip direction as I had been planning to practice. I was not going to need any slip at all... in fact, I was going to land short. What the...?? Only later when I thought about it did I figure out what had happened and why:
  1. During the 45-degree leg (the pattern entry), for some reason I had a hard time spotting the wind sock. I knew that there had been a fairly strong wind, about 14-18 knots when I took off, and I wanted to be sure to know what it was doing so I could plan my slipping pattern. That turned out to be a bigger distraction than I realized.

  2. I switched over to AWOS to get the wind, and waiting for it consumed most of my 45-leg time, putting me a little behind with my downwind turn, slip setup, and radio call.

  3. So although I got the wind direction right, I failed to adjust my pattern speed for the wind strength. That had little effect on downwind and base, but when I turned final, that insufficient airspeed meant that I didn't penetrate the now-headwind, and I ended up short... and wondering why.
So what I learned is that I should get the wind from AWOS well in advance of entering the pattern, so I'm not rushed. Then make sure to use the "S" for speed in the checklist to choose my pattern speed as well as compensate for the wind direction. That's second nature on a normal pattern, but for this no-drag-device approach, I've been thinking too much about the wind direction for the slip, and not enough about the whole FUSTALL checklist. More to practice! I'm planning to fly every weekend that I'm in town in August and September.

On the other hand, my study and practice tests for the CFI written tests are going really well, and I plan to take the test within the next two weeks.

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