I had a fun, interesting and challenging wave flight on Sunday. Talking to Kempton, who was planning to fly from Williams, the prior evening, my plan was to head north to the Napa valley wave once I get to 18K. So I took a tow shortly after 10AM to Los Vaqueros towers (few miles SW of the towers near wave3 waypoint) and released in weak wave which only took me to 7K, but enough to move further north to try to Diablo wave (wave1) which worked much better and eventually gave me 15K of altitude where the climb stopped. The wave was relatively weak and inconsistent likely due to the wind direction shift from NNE to NNW and back to NNE, and the wind dropped from 45 knots to 35 knots above 12K or so. While climbing in the Diablo wave I was in contact with Norcal which went well. I was asked about my intentions and replied they I will likely remain stationary for the next hour with gradual climb expecting up to 18K, so they vectored the airliners a little further north pointing me out to each one. I could also see some of them as ADS-B targets in my powerflarm. Anyway once I stopped climbing at 15K I decided to try Napa anyway, with the plan to turn around if I don't find anything before I loose glide back to Byron. Easy said than done, since as I was getting closer to the point of no return near Napa, I hit strong sink, which is indicating of possible strong wave lift nearby, so I wasn't willing to give up at that point, and quickly lost glide back to Byron and was now committed to Napa airport. Committing to Napa actually made things easier since now I had extra altitude to look for the wave, and based on Kempton's tip from our early discussion, I moved further west and indeed found the wave over the SW corner of the town at around 5000 feet. It was averaging only 1 knot and took long time to climb to 8K which was all I could get. Once at 8K over Napa I had marginal glide back to Byron and had the option of gliding back to Byron or try to explore more. To make long story short, I spent the next couple of hours exploring the wave trying to continue north with limited success , getting closer to the town of St Helena, but each time retreating back to the Napa wave to climb back up, from as low as 3000 feet (which required circling in the rotor for a while). Each time back to 8K or so after long slow climb and trying to explore in different direction. As I am not aware of any other safe airstrip in Napa valley which is covered with unlandable vineyards, I made sure to keep Napa airport in safe glide all the time. It was interesting to note that the wave was nearly miles downwind of the hills, which would suggest secondary wave, but I never found a primary up wind. so after 3 such low saves at the exact same spot over Napa back to 8K I was planing to go on final glide back to Byron, only to manage to climb higher this time to 9.3K, which gave me comfortable glide back to Byron. But I guess it was too comfortable for my taste, and being greedy as I am, I decided to try north once more to see if I can connect with the St Hellena wave before going on final glide. I actually finally found a good 10 miles stretch of wave maintaining above 9K, pretty much where Kempton found strong wave in previous flight from Williams, and kept going until I almost lost glide back to Byron then turned around with the confidence that I can follow my trace back and regain glide, but to my horror the wave completely fell apart and I found strong sink at exactly the same line I was climbing few minutes earlier. Even the Napa wave was no longer working and turned into strong sink. This highlights one of the differences from thermal flights - if you loose the wave, you will likely encounter strong sink and will loose ton of altitude before able to reconnect, much more than the typical sink between thermals, and sometime you wouldn't be able to reconnect. Also down lower it may be harder to contact the wave as it may not be working well below certain altitude. So I found myself over Napa at 5000 feet or so, well below glide to Byron 50 miles away, in strong sink and one hour before sunset. A quick check with my flight computer confirmed that I still had glide to Concord if I head there immediately, and so I did, making the retrieve much easier than Napa. Concord tower was friendly and on the ground I got help from Rusty who was the Byron airport manager last year.
As it was 30 minutes or so to sunset, I figured it was too late to call for aeroretrieve, so instead asked my wife to come get me, as my home in San Ramon is only 20 minutes away. But as it turned out, Mathew was heading that way on his way back home anyway, and with 2 passengers (Maya and Fabien) which were kind enough to volunteer to drive my car and trailer so I could spare my wife from the drive and save a trip to Byron to get my car. Thanks folks, and thanks to Buzz for coordinating that and hooking up my trailer.
All in all, it was an educating flight trying to explore wavelets over Napa valley where I have limited experience flying in wave, and a reminder not to push my luck too much, after 3 low saves it was probably time to head home :-)
Flight trace: http://www.onlinecontest.org/olc-2.0/gliding/flightinfo.html?dsId=2795594
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