Sunday 5-20-2001, Boulder, CO. I was supposed to fly out on business that morning. I went to DIA as planned in the morning. From DIA to the W, the sky looked pretty good. I was sure that was due to the fact that I had to leave. However, my travel agent had screwed up my flight arrangements, so instead of an AM flight I had a PM flight, as I just found out at the terminal! So I decided not to wait on standby for another flight since the chances of getting it were very low anyway, but rather to go back to Boulder and take advantage of what it'd looked like it was going to turn to be a pretty good soaring day.
... time forward ... about 3pm at 1V5 ...
There was a prospective new club member and I offered to take him for a ride. To the NNE, the sky looked as it were overdeveloping. We launched in 13K. Mike Exner towed us in 08L.
As we launched and towed through 7Kft, Mike told me to watch the wx to the NE, and I was already doing that. It was starting to look much worse than just before the launch. I just wanted to get away from it, since it looked like something localized and that it would move through in 20min. I did consider releasing and speeding back to land, but I figured that I would most likely hit the gust front in front of it. On the other side, there were a few sunny spots in the mountains. From my previous flight 30min earlier I knew that there was lift that could be worked.
As we towed NW towards the mountains, in no time the wx moved in and was almost over the field. By this time, it definitely looked pretty bad. Mike was talking to me about possible options. I could barely hear and understand the radio. I was in the front seat of 13K and the speakers are behind the passenger in the back. That, coupled with building static made it almost impossible to make out what he was saying. Luckily, I had my handheld with me, and that worked much better.
Eventually, Mike waved me off, and I headed for lift in the few sunny spots that were still there. It was not working great, but I had enough altitude to hang around in it for another 20min as I thought the worst wx will pass by then.
Mike flew back to Boulder and reported that it was pretty bad, x-winds 30kts, with gusts even higher. One suggestion was that I go to Longmont (2V2) in the hope that it might be better there. I did not think that was such a good idea, given that Longmont is oriented NW, and winds were NNE. Also, with that much headwind, I calculated that I may not be able to make it there anyway (I had my final glide calculator and GPS). Anyway, Mike flew to Longmont and reported that it was just as bad. From there Mike went to Tri-County (48V) and landed there.
Since the worst weather was E of foothills, I decided to hang around over the mountains a little longer, that is, while I still had sufficient altitude. I stayed over the sunny spots for a while, and my passenger flew a little. As the sunny spots disappeared and the lift stopped working, I headed E. There were a few bumps along the way, but nothing workable.
I flew to position myself to the N of the field. By this time it became clear that the weather was not going to change much for my landing, especially given that it was cloudy and yucky all over, it was blowing at 40-50kts at that altitude (I was gliding down through 8Kft). It looked like there would be nothing to produce any lift. The two main landing options were (1) land out into the wind, or (2) land at 1V5 diagonally.
Interestingly, as I got close to Boulder reservoir, I hit a patch of lift. I circled right and fell out of it. I headed back for the same spot. It was still there, sort of. I decided not to work it, and as I moved more E I got into some sink. Then I hit another patch of lift. I moved perpendicular to wind direction, WSW - ENE, and that worked well (fig 1). I was able to maintain and even gain little altitude. It would disappear if I went too far in either direction. I was sitting in place at 45kts IAS, essentially just slowly moving sideways wrt ground. I thought it was some kind of a mini-wave, and that, given the wind speed and direction, there must be some surface feature upwind that was generating it, but I could not determine what. After the flight I drew the trace (fig 2). Apparently my mini-wave was generated by the Haystack Mountain; it is positioned 4.5km directly upwind from where the lift was found.
It was really nice to sit almost stationary and watch small clouds fly by. I was essentially parked in 0 sink which allowed me to rethink whether there were any other landing options that were not considered. However, it boiled down to #1 or #2. I was not too keen about landing out. MHG G102 did exactly that, and I could see him sitting in the field. Meanwhile, Mark reported that the wind on the ground had eased a bit.
I stayed in my mini-wave for a few more minutes. As it started to rain, it was time to land. My plan was to land on the main runway. The thinking was that, in the optimistic case, if there were enough surface friction, the wind just above the ground may not had been that strong and I might had been able to straighten out on the runway. O/w, I would just go diagonally towards the SSB shack. I knew that the field was pretty level there, while there was a ditch further down E.
I flew something a little reminiscent of our standard landing pattern (fig 3). I kept my airspeed between 65 and 70. On the downwind, I flew away from the field to have enough space to do a really-well-banked 180 turn (i.e., my base) onto the final. It was very gusty. By the way, it was interesting to note that even on such a bad day there was still a bump of lift on the downwind leg, in its usual place where it always lives. As I flared, the rudder had not much effect, so it became clear that it was best to not even try to stay on the main runway. I touched down at about the centerline, and started rolling directly towards the runway edge, specifically directly towards the runway light (knee-high rods sticking out on the side of the runway). I hopped over it and touched down again on grass and quickly stopped.
My passenger appeared cool throughout the flight. As we landed I explained to him that not every flight had the extra excitement component that we had just experienced. Quoting Mark, "The passenger said that the ride had exceeded his expectations and rated gliding above bungee jumping for thrills." He also said that he was not sure whether the whining sound (vario) was an emergency signal indicating it was time to jump out. We'll see whether he joins...
A few SSB members and other spectators helped to pull and tie down the glider. Around that time it was starting to snow.
The whole flight took 59 minutes (fig 4). The pressure difference from launch to land was almost 300ft! That is, the pressure rose from 29.72"Hg to 30.00"Hg. The highlighted area in fig 5 shows the preasure change during the filight. The temperature dropped from 68F to 40F (fig 6). According to NCAR foothills lab measurements, which are typically a little bit less than what we really have at the field, at the time when I landed, the wind speed was 20kts gusting to 40kts (figs 7, 8).
Hopefully, this story would help other SSB members be safer pilots. This wx was forecast. There is no excuse not to check wx forecast before flying, no matter how good the sky looks. Apparently, nobody that was hanging out at the field that day had done it!
Fly safely. Pedja
To watch time-lapse movie of the day's weather, click here (QuickTime plugin required).
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