Saturday, November 22, 2008

Some work and a sled ride

Today the weather forecast was really iffy. Light winds, and lift could go to 7000', but incoming cirrus clouds could spoil it.

The PW5 needed a little work, so I tackled these in the morning:
  • The battery wires were fraying. A and I put new lugs on the ends.
  • The gust locks for the ailerons needed new foam and bungee cord. We'd been using rags as padding for a few months!
  • Replaced the long rear bungee cord on the canopy cover.
  • The O2 system had been left turned on, so the battery was dead. A kindly went to town for a battery.
Some of the student pilots are coming to me with questions about procedures and resources. Without actually getting into ground school, I explain what I can. As one pointed out (and as I've blogged about), many of the books tell you what but they really don't explain the why. For example, one wanted to know about radio procedures on the UNICOM frequency in the landing pattern. What do you need to say, and in what sequence? Why in that sequence?

1. First, say who you're addressing, e.g. "Hemet traffic:" Why first? To get the attention of people who may not be fully listening. You're saying, "Hemet traffic, listen up!"

2. Next, who you are. "Glider two papa delta..." If you said this first, then who you're addressing, people would miss your call sign because they didn't start listening until they heard "Hemet traffic." Listeners aren't fully listening all the time.

3. Where you are. "Entering 45 for..."

4. What you are going to do. I get really specific because we gliders share the airport with power traffic, and they are most of the radio traffic. They're on the other runway (23) and they do a left pattern (which they don't specify). I want them to understand where I am going and that I'm not conflicting with them. "... right-hand pattern to runway two two." I emphasize the second two because they're normally listening for "two three".

5. Finish with who you're addressing. "Hemet". In case #1 got cut off, or was garbled, or they really weren't listnening at the beginning.
Once you understand the why of the sequence, it's easy to remember!

A had not flown the PW5 for a while so I went over the controls and features with him. He took off before noon and had a nice hour-long flight. Unfortunately, he used up all the lift. ;-)

I let off in lift but could not get back into it. The cloud cover had gotten thicker and there was very little sunlight hitting the ground. All I found was about 3 knots of sinking air. Near the Initial Point at about 1300' AGL I found a little weak lift but it was not even big enough to complete a circle in. I ended up with an 18-minute ride. Bummer! After about 2:00, most people were not staying up any more.

At least my landing was good. There was maybe a 4-knot headwind at most. I think I touched down right on the line, and stopped well within the first box. I think what made the difference was that I picked out my aiming point as soon as I turned base, and kept checking my angle to it all the way on the base leg. I think I've been looking elsewhere on base leg, and then not being at the right altitude when turning final. By establishing my aim point on base, the base and final legs are all part of the same glide slope.

Saturday, November 08, 2008


One of the requirements for the Commercial practical test is landings twice as precise as for the Private certificate. The Practical Test Standard says "stopping short of and within 100 feet of a designated point". I'm told that at our field, that translates to touching down and stopping within the first of our two landing boxes, which I think is about 500 feet long. I've had some issues with touching down too soon, i.e. short of the box, and I've been planning to work on this for some time. But the weather conditions have been pretty good lately, so I've tended to go soaring rather than spend time (and money) on landing practice.

I really need to practice this in a Blanik, since that's what I'll take the test in, but one was busy with students all day and the other had its control surfaces removed for replacement of the fabric, so I decided to practice in the PW5. It's different from the Blanik: lighter, doesn't have flaps, and is different in many ways, but my problem hasn't been with those aspects. My problem has simply been the glidepath to the aiming point. For some reason I tend to pick an aiming point too far downwind from the box border, making it so I have to float too far. In other words, I have tended to come down too steeply during the base and final legs.

Flight #1: I let off at the Initial Point at 1000' AGL. In lift! By the time I got to the point of turning base, I was STILL at nearly 1000'! I extended my downwind leg much further than usual. Full spoilers and forward slip and turning slip brought me down steeply, but again my roundout point was too far downwind. The standard advice is to not adjust spoilers after rounding out, but sometimes I do close them slightly to slow the sink rate. At least with the PW5, that's hard to get right, and it's easy to balloon up a bit. I touched down about 15' short of the line. Braking on the ground was very good (there was about a 6-knot headwind component), and stopping smoothly within the first box was easy. (Speed control is crucial to touching down with little energy, making for a short rollout. This I seem to have no problem with.)

Flight #2: This time I didn't have a bunch of lift on downwind, and had a more normal pattern and approach. Speed was right on, didn't have to mess with spoilers, just kept easing the stick back and floating... floating... floating... touched down about 1-2 feet short of the line. Good rollout again.

Flight #3: I decided to do a normal tow and do some soaring. Gotta have some fun, right? Uneventful flight: let off in lift, went up to about 5800' MSL, didn't find any other major lift. Nice clear day! A bit of lift on downwind, but not nearly as much as the first flight. Speed was a little high but I fixed it. Touchdown was... hmm... I don't really remember, I think still about a foot short of the line. Rollout again was nice and short. The wind was just right to "ground fly" balanced on the wheels for about 30 seconds or so.

On all three flights, I think I only used about 2/3 of the first box - the PW5 really stops short and smooth. So... I should definitely move my aiming point even more upwind on the field, to float further into the box, at least when there's a light headwind. I think that's part of the problem: trying to estimate how much the wind will help kill the float - maybe I'm underestimating that aspect. And flying all three different aircraft doesn't help. They're all different weights and different glide ratios, so adjusting for multiple variables is tricky. When I can nail landings in the first box in both Blanik and PW5, in varying wind conditions, then I'll know I'm ready for the practical. (Not a chance in the Grob - it's way too heavy and its wheel brake is weak. I was lucky to stop it in about 1200' a few weeks ago.)

Saturday, November 01, 2008

First Mountain Wave - well, hill wave anyway

Very interesting weather at Hemet today. A low pressure system to the east was to bring rain in by evening, and there were lots of thin cumulus clouds hanging around. The thermal forecast looked good, though no CU were forecast. The temperature profile looked good - no inversion at all. Driving in, I could see occasional little lenticular clouds, indicating wave activity. Huh? There were big "lennies" on the west side of Mt. San Jacinto and smaller ones to the north and west of the valley, but only CU and clear areas over the valley. The tricky part for me has been to figure out from the lennies which direction the wind is actually blowing, and therefore where the upwind side should be. The sounding map showed the wind at about 240, and driving in I was able to observe the trailing edge of a lennie dissipating, and that was the northeast side, which confirmed for me that the wind aloft was from the southwest.

The thermals were only supposed to go up to 7300' MSL, not high enough to reach the big lennies... but maybe the little ones?

The temperature was about 90F, higher than forecast, and way over trigger temperature. The wind at ground level was 13 to 16 knots, and was forecast to be about 20 at 5,000'. By the time I took off in the PW5 about 2:00, the sky was 90% obscured, and I was afraid thermal activity would shut down. But I let off tow in lift at 4500, and worked up to about 5500, and headed southwest toward the closest cloud that looked lenticular. To get there I had to head directly into the wind (approaching what I thought would be the lift area by flying under the cloud - watch out for rotor!). That's usually a killer for altitude, but I was in zero sink much of the way. Groundspeed was way slow! (I didn't bring my PDA, so I didn't have any true wind or groundspeed info.)

The cloud was further away than I thought, beyond the hills beyond the little town of Winchester. Thinking there might be rotor directly under the cloud, I skirted the edge between it and the next cloud. Wrong idea: there was no lift, even a little sink between the clouds, and the zero-sink or 1-knot lift had been under the cloud. I turned around and headed back toward the airport. I was fairly low, but I knew I'd be flying downwind to get back, so I would not lose too much altitude.

Close to the airport, I found lift again and worked it up to 5800'. My drift in the thermal confirmed the wind direction. I headed off toward the lennie again. This time, I was starting higher and closer, so I had a better chance of making it all the way. The minor lift was there again, all the way over to Winchester and beyond. I stayed under the cloud and drifted up, though I never reached cloudbase (which AWOS reported as 7,500'). But the cloud was still further southwest of the airport than I was comfortable going, so I did not go all the way to the leading edge. I eventually turned back and headed home, planning for about a one-hour flight duration.

Under a cloud, it's hard to see the actual shape, but earlier I had been able to see it was a combination of lenticular and CU: smooth and curved at the upwind side, then broken and puffy and going upward on the downwind side. And the next cloud over was definitely smooth and lens-shaped, clearly a wave cloud. So I conclude that I was flying in wave lift, not "cloud suck". It was not as smooth as most wave is described, but then I was not at the leading edge. And these clouds did not quite fit the classic lennies caused by wind blowing across a ridge. The hills upwind that created these waves are small and isolated, so the waves were not wide areas, more like small points. Since I was only up at between 5 and 6 thousand feet, I also conclude that the wind was probably bouncing off the ground, not off a stable air layer. So when I was flying under the cloud, I was essentially flying upwind in a huge updraft between the ground and the condensing moisture. Really a strange flight: I flew about 7 miles directly into a 20+ knot headwind, and actually went UP!

Coming back to the airport, I hit some fairly strong turbulence and some 8- to 10-knot sink. It was either rotor, or all that air that went UP coming back DOWN.

The thermal forecast certainly got the condensation level wrong - it forecast 18,000' and the cloudbase was actually 7,500.