Thursday, December 27, 2007

Sleigh Ride

We often call a glider flight a "sled ride" if there's no lift found, because it's a downhill ride all the way from release to touchdown. But since this was the last Saturday before Christmas, let's call it a sleigh ride. And this day of soaring involved some frost and ice!

The forecast was for 450 or so fpm of lift up to 5000 or 6000 feet, but there were hints of an inversion which could defeat the lift. I was determined to fly regardless of lift, because I had not been in the air for about a month. It was very clear due to recent rain, and had been cold overnight. There was frost on the wings of the Grob and the PW5, which I have never seen at Hemet before. T commented on my blog post about the water collecting in the PW5's spoiler boxes and horizontal stabilizer, so we checked the boxes and were surprised to find ice. And not just a little skin of frost - a hard layer of ice a good quarter inch thick and about a foot long! It took quite a bit of work to break it up and pull it out so it would not interfere with the spoiler arms. Then we checked the drain holes in the boxes... one on each side was plugged with dirt, which explains why the water accumulated. Something else to inspect and maintain. There's something to learn every day on every flight!

I planned to take a high tow because I expected there to be no lift. The ground temperature was above the trigger temp, but if the air was too stable that wouldn't matter. On the way up, I decided to use the Outside Air Temperature (OAT) display as I have mentioned before. On the ground, it registered 25C, or 77F, which is way more than the 63F thermometer in the shade on the shed was indicating. So the dark runway must have been heating the air just at ground level. I didn't watch the OAT right after takeoff, but at about 400'-500' AGL it was already down to 16C. It kept going down fairly rapidly as we climbed, and then it stuck at 9C at about 1500'-2000' AGL and stayed there all the way up to 3800' AGL where I released. So there was a definite inversion layer - a big thick layer of 9C air that was not getting any cooler! I knew that I would not find any lift in that zone.

The flight was nice anyway, even if was a sleigh ride. The visibility was incredible! Usually we have some haze or smog, but this day was crystal clear. I could see quite a ways out into the ocean, and the sun was lighting up the water like gold. The mountains and all the lakes were gorgeous. This is why I fly.

I played around a bit with airspeed and sink rate, trying to get the minimum possible sink. Maybe sometime I'll take notes on them and see how they compare with the published polar.

I did find a few bumps at 1200'-1500' AGL, below that inversion layer. I circled a few times and found nothing better than zero sink. All too soon it was time to come in and land. My flight time from 3800' AGL was 26 minutes, or 146 feet per minute - right at the theoretical minimum sink rate for the PW5.

A reminder for the new year: the Air Safety Foundation recommends that your first flight of the year be with an instructor. Not a bad idea!

Thursday, December 13, 2007

Blown out

It seemed like everything was conspiring to prevent me from getting in a flight last weekend. I had planned to give a friend a ride on Sunday. But the weather is always iffy this time of year, and a series of cold fronts have been moving through. Saturday was rainy (and I was busy anyway). Sometimes the day after a storm is good soaring weather, but this day still had substantial wind in the forecast, so I waved the friend off and decided to go out myself and see if it was flyable. Hemet is often a calm place when there's wind all around... and the thermal forecast looked usable. Really cold air aloft!

Due to other morning commitments, I arrived at the field about 12:30. A few people were flying, a pilot reported some wave lift earlier in the day... so I decided to go ahead. Delay #1 came in the form of rainwater in the PW5's spoiler boxes. I'd never paid much attention to it before, but we checked and found at least an inch. Tipping the glider onto each wing drains the water out of holes, but it takes a while. It collects in the horizontal stabilizer, too. So, to you other PW5 guys in the club: plan on about 15-20 minutes of extra prep time after a rain!

Delay #2 came in the form of an unfavorable wind direction. This is the first time I have ever seen the tow operation reverse directions at HMT. Should be no big deal, right? Except that now the starting end of the runway is a LONG way from the tiedowns. So I need the help of club members to push out (I can push the PW5 myself to the close end of the runway.)

Delay #3 came in the form of more complicated operations using the reversed runway. I won't go into details, but it involves more work to keep the runway clear for landings and for tow plane operations, and fewer good landing options.

There were other little things along the way, minor equipment issues. I finally was lined up on the runway, next in line for takeoff at about 3:30, a little late in the day especially in winter. But as I always tell people, I'd rather take a sled ride than stay on the ground - gotta stay current and proficient! And the view of the freshly snowed mountains promised to be spectacular.

And then the wind picked up! For several minutes it was at least 15-20 knots, and was shifting direction about 30 degrees. The PW5 really does not do well with much crosswind, and it seemed to me this could be the start of and end-of-day wind increase. If I took off, and then the wind got stronger while I was up... well, as I mentioned, the landing options are a bit more restricted when operating the other way on this airport. So I cancelled and pushed off.

Maybe next weekend. Between the iffy weather and the extra stuff that occupies weekends during the holiday season, it may be another couple of weeks.