Archives for April 2006

More Lessons From Tiger

I had a mildly harrowing flight today off of Tiger Mt.

Conditions were questionable, from either North or South launch.

On the South launch, winds were cycling from 3-15 MPH, driven mostly by sun-heated atabatic flow, in cycles lasting about two minutes long. In the lulls, however, the wind was blowing backwards from the North from 1-2 MPH, for about 30 second intervals.

On North launch, which was more in the shade, the winds were only 1-3 MPH, but were also alternating directions about every minute.

Kristen and I had hiked up to the top, and there were no other pilots on launch. That alone was a big clue, and I was seriously considering just hiking back down with my wing. Instead, we waited quite a while and the cycles on South launch got lighter and farther apart.

Eventually, it was light enough on South that I figured I could launch. However, on set-up, I still alternated between having a respectable “wall” in my wing, only to have it collapse and blow over from the rear. I was waiting for a good lull, then planned to just get out of there in that window. It was not a day I would have preferred to launch, but I kept asking myself “is it safe?” The answer kept coming back “It’s questionable.” So I waited some more, then decided to launch off of South.

Well, the sink right after launch was pretty bad. I ended up hugging the ground for way too long, gaining altitude only as the ground dropped, then sinking back again for probably 500 yards down the mountain. I was airborne this whole time, but never more than 30 feet above the ground, and some times as low as 10 feet over the trees. Mentally, I was thinking about evasive-maneuvers. “Look for the opening” I kept telling myself. Look for the spot where the ground dropped away the most, or where I had the most clearance from trees. Meanwhile, my wing kept suffering from momentary collapses on one side or the other, making that tell-tale FWOP noise. All the while, I dare not look up to see it, since my eyes were so focused on steering a path to open air and avoiding the trees. My brain was on over-drive.

But eventually, I did clear the last of the trees, mostly because the hill dropped off precipitously, and not because I flew out or over anything. But now even with over 100 of feet of clearance, I was still in some pretty bad sink and I was concerned that I would just barely make it to the bottom of the mountain, probably landing in the swimming pool at the nudist colony at the base. In fact, it was on my mind as an alternate landing zone because everything else was worse. I needed more altitude to get around the horn to the right and pointed towards the primary landing zone.

Eventually, I did manage to get enough vertical clearance to turn right, and I could see what was going on: the battle between a gentle North flow, and South atabatic flow. I should have gone off of the North launch, or else decided to walk. Nonetheless, I still had to make it to the LZ, and altitude was quite low. I thought I might land in the big swamp south of the LZ, but that would actually be OK. When I got closer, I saw that all three windsocks at the LZ were pointing different directions, with the highest and most prominent one indicating the wind was from the South. On the bright side, that wind was taking me directly towards the landing zone. On the other hand, I find landing to the South more difficult because of the high trees on the North end of the field.

I set up for landing, pointing South, with appropriate clearance for those trees. Unfortunately, I didn’t have forward penetration through the wind. I was staring at the tree with the windsock maybe 30 feet away both below and to my left. The sock was blowing straight out, and I was completely stationary in all directions – both vertical and horizontal. I knew that if the wind died or shifted, that my margin of separation was inadequate. So for the first time, I had to use my speed-bar to sacrifice altitude in an attempt to gain the forward speed necessary to get in front of the trees. I had used it once before at much higher altitude as part of my training, but this was the first time I used it out of necessity.

While it did let me penetrate forward of the trees and closer to the LZ, I did not want to hold too much speed-bar with winds that twitchy. Remember that all three socks pointed in different directions, so once I had cleared those trees in the south-wind, I was now over the LZ with West-wind. The problem is that the LZ is a football field long from North to South, but only a swimming-pool wide from East to West, with power-lines and a highway on the West. Of course, there is a mountain and trees on the East, so South-West was the way to go splitting the distance between the power lines and the swamp.

I had descended to maybe 15 feet above the ground and was ready to flare right where I wanted to be, but then I got a big updraft which took me back up to about 40’ amidst the screaming beeps of my variometer. I wanted to just pick a straight line and stick with it rather than making big changes that close to landing, but the conditions sucked! I was not about to pull “big-ears,” since the rapid-switching meant I wanted full control of my wing. I did manage to eventually sink back down to 10’ again, sinking very slowly with a ground speed of near zero. I made a slight flare, followed by deliberately running forward, then turning and a rapidly killing my wing. I was on the ground, and I was fine.

The entire flight lasted probably less than 4 minutes. A normal no-wind flight takes closer to 8 minutes. While it was not a flight that I would care to repeat, I was quite pleased that I had an array of skills and tricks at my disposal to manage a safe journey. I’m also grateful for the opportunity to have a “learning” flight I can draw upon for the future.